Shifting alleles: Natural selection versus genetic drift in the Mountain

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Population signatures of large-scale, long-term disjunction and small-scale, short-term

habitat fragmentation in an Afromontane forest bird

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4 Jan Christian Habel

1*

, Ronald K. Mulwa

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, Franz Gassert

3 , Dennis Rödder 4

, Werner Ulrich

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,

5 Luca Borghesio

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, Martin Husemann

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, Luc Lens

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1

Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management,

Technische Universität München, D-85350 Freising-Weihenstephan, Germany

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Department of Ornithology, National Museums of Kenya, KE-00100 Nairobi, Kenya

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3

Department of Neurobehavioral Genetics, Trier University, D-54290 Trier

11 4 Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, D-53113 Bonn,

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Germany

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Nicolaus Copernicus University, Department of Animal Ecology, Pl-87100 Toruń, Poland

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Department of Biological Sciences, U niversity of Illinois, 60607-Chicago, Illinois USA

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Terrestrial Ecology Unit, Ghent University, B-9000 Ghent, Belgium

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17 *Corresponding author:

18 Jan Christian Habel, Terrestrial Ecology Research Group, Department of Ecology and

19 Ecosystem Management, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2,

20 85350 Freising-Weihenstephan, Germany

21 Email: Janchristianhabel@gmx.de

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23 Running title: Fragmentation genetics in a tropical forest bird

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25 Keywords: Biometrics, cloud forest, habitat continuity, habitat change, population genetics,

26 microsatellites, temporal comparison, Species Distribution Modelling

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27 ABSTRACT

28 The Eastern Afromontane cloud forests occur as geographically distinct mountain exclaves.

29 The conditions of these forests range from large to small, and from fairly intact to strongly

30 degraded. For this study we sampled individuals of the forest bird species, the Montane

31 White-eye Zosterops poliogaster from 16 sites and four mountain archipelagos. We analysed

32 12 polymorphic microsatellites and three phenotypic traits, and calculated Species

33 Distribution Models (SDMs) to project past distributions and predict potential future range

34 shifts under a scenario of climate warming. We found well supported genetic and

35 morphologic clusters that corresponded to the mountain ranges where populations were

36 sampled, with 43% of all alleles being restricted to single mountains. Genetic population

37 differentiation strongly matched each other at a regional level. Our data suggest that large-

38 scale and long-term geographic isolation on mountain islands caused genetically and

39 morphologically distinct populations clusters in Z. poliogaster . However, major genetic and

40 biometric splits were not correlated to the geographic distances among populations. This

41 heterogeneous pattern can be explained by past climatic shifts, as highlighted by our SDM-

42 projections. Anthropogenically fragmented populations showed lower genetic diversity and a

43 lower mean body mass, possibly in response to suboptimal habitat conditions. Based on these

44 findings and the results from our SDM analysis, we predict further losses of genotypic and

45 phenotypic uniqueness in the wake of climate change, due to the contraction of the species´

46 climatic niche and subsequent decline in population size.

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48 INTRODUCTION

49 Fragmented populations have long been assumed to constitute valid ecological models to

50 predict population trajectories in landscapes subject to rapid anthropogenic habitat

51 fragmentation (MacDougall-Shackleton et al ., 2011). Indeed, fragmented populations often

52 have smaller effective population sizes, reduced dispersal rates, and lower genetic diversity at

53 the population level, compared to panmictic populations (Frankham, 1997; Blanchet et al .,

54 2010). However, in contrast to populations living in historically stable habitat conditions,

55 species exposed to rapid fragmentation of formerly interconnected habitats are rarely able to

56 adapt to these new environmental conditions, in particular since they are often exposed to

57 simultaneous deterioration of the remaining habitat (Stratford and Robinson, 2005;

58 Keyghobadi, 2007; Walker et al ., 2008, Habel and Zachos, 2013). While demographic and

59 genetic effects may be slowed down or counterbalanced by migration and gene flow among

60 populations (Wright, 1951), population connectivity often rapidly decreases when habitat

61 fragmentation increases (Fahrig, 2003). Ultimately, the combination of habitat loss,

62 deterioration and isolation is expected to modify the ecological conditions for populations,

63 which have been shown to be subject to stochastic demographic fluctuations, increased

64 inbreeding, loss of heterozygosity and accumulation of mildly deleterious alleles, while

65 genetic variation might additionally be lost through strong genetic drift in exceedingly small

66 populations (Frankham, 1995; Higgins and Lynch, 2001; Keller and Waller, 2002;

67 Kalinowski and Waples, 2002; Frankham, 2005; Palstra and Ruzzante, 2008). The direction

68 and strength of these effects, however, is expected to vary with both the (evolutionary) history

69 of the landscape change and with species-specific life history traits (Callens et al ., 2011,

70 MacDougall-Shackleton et al ., 2011).

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72 The Eastern Afromontane (EAM) biodiversity hotspot offers a unique setting to study how

73 long-term natural disjunction and short-term anthropogenic fragmentation may affect

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74 populations over different temporal and spatial scales. This biodiversity hotspot region

75 consists of widely scattered but biogeographically similar mountains, running from the Arabic

76 Peninsula to Mozambique and Zimbabwe (White, 1978). Strong isolation caused by

77 orographic heterogeneity and relatively stable climatic conditions have led to an accumulation

78 of endemic species and intraspecific lineages (Bowie et al ., 2006; Burgess et al ., 2007). Many

79 taxa in the region currently occur as geographically restricted units at single mountains, and

80 as such, comprise naturally fragmented populations with independent evolutionary trajectories

81 (Measey and Tolley, 2011). In addition to these long term evolutionary dynamics, plant and

82 animal taxa of the EAM biodiversity hotspot are currently affected by severe loss and

83 degradation of their natural habitats over very short timescales. The EAM forests, in

84 particular, have been subjected to variable anthropogenic effects over the last decades that

85 resulted in a wide range of contemporary forest types, i.e. (i) both large and small pristine

86 forests; (ii) historically fragmented forests; and (iii) anthropogenically fragmented and highly

87 degraded forests.

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89 In this study, we analysed genetic variation based on 12 polymorphic microsatellite markers

90 and phenotypic variation based on three morphologic traits, in Zosterops poliogaster

91 populations sampled in 16 sites across four mountain blocks. Z. poliogaster requires cool and

92 moist climatic conditions and is thus largely restricted to the cloud forests on top of the East

93 African mountains. We sampled populations in each of the above mentioned forest types with

94 contrasting habitat history and current characteristics. To study genetic and phenotypic

95 population effects of rapid habitat change, we sampled and measured both museum specimens

96 and current captures, i.e. covering past and recent episodes of forest fragmentation (Pellikka

97 et al ., 2009). We further performed Species Distribution Models (SDMs) based on 19

98 bioclimatic variables to project the past (6000 and 21,000 years BP), current and future (2080)

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99 climatic niches of Z. poliogaster . By integrating results from genetic, biometric and SDM

100 analyses, we addressed the following research questions:

101 (i) How do long-term and short-term processes of habitat isolation and fragmentation

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103 affect the genetic and morphological structure of mountain populations of Z. poliogaster ?

104 (ii) How do habitat persistence and rapid habitat change affect the population genetic

105 structure in Z. poliogaster ?

106 (iii) How may climate change affect the intraspecific structure and uniqueness of Z. poliogaster in the near future? 107

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109 MATERIAL AND METHODS

110 Study species

111 The bird genus Zosterops is known as a “great speciator”, i.e. showing strong levels of genetic

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113 and phenotypic differentiation across various geographical ranges (Warren et al ., 2006;

Moyle et al

., 2009; Milá et al ., 2010). The East African Mountain White-eye, Zosterops

114 poliogaster is a omnivorous (mostly insectivorous - nectarivorous) flocking bird species that

115 inhabits moist and cool mountain cloud forests across Kenya, Tanzania, Uganda, Somalia,

116 Ethiopia and Eritrea at an elevation of 1500-2500m (Mulwa et al.

, 2007; Redman et al .,

117 2009). Populations at geographically-isolated mountains show distinct morphological (e.g.

118 plumage colouration; Redman et al ., 2009), genetic (Habel et al ., 2013) and bioacoustic

119 (Habel et al ., 2014) variation, which has resulted in to the recognition of different taxonomic

120 entities (Borghesio and Laiolo 2004; Mulwa et al ., 2007; Del Hoyo et al.

, 2008).

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122 Sampling scheme

123 Between 1990 and 2011, a total of 390 individuals from 16 populations were sampled with

124 mist nets in four mountain ranges across the Kenyan section of the EAM: (i) Mt. Kulal

125 (2,69N; 36,94E; ca. 2000m) and Mt. Kasigau (-3,82N; 38,65E; ca. 1500m) still harbour

126 pristine, interconnected and intact cloud forest, in which 46 and 22 individuals were sampled,

127 respectively; (ii) In the Chyulu Hills (-2,66N; 37,87E, ca. 2200m), cloud forests constitute a

128 forest-grassland mosaic that has at least persisted since the Maasai pastoralists caused regular

129 fires many hundreds of years ago. A total of 52 individuals were sampled in two forest

130 fragments located at the northern- and southernmost edges of the mountain range; (iii) In the

131 Taita Hills (-3,41N; 38,30E; ca. 1800m), continuous cloud forest has been transformed into

132 isolated and degraded forest remnants mainly due to small-scale subsistence agriculture, with

133 a particularly dramatic loss, deterioration and isolation of the remaining forest cover since the

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134 1960s (Pellika et al ., 2009). Here, a total of 270 individuals were sampled in 11 forest

135 fragments located along the entire higher elevational range.

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137 Upon capture, each individual was banded with a unique aluminium ring from the East

138 African Ringing Scheme. After measuring its wing length (mm), tarsus length (mm), and

139 body mass (g), a blood sample (stored in pure ethanol and subsequently frozen at -20°C) or

140 feather sample was collected. To allow analysis of temporal variation, field samples collected

141 during 1990, 1997 and 2000 (Ngangao 1990: N = 28; Mbololo 1990: N = 27; Mbololo 2000:

142 N = 14; Mt. Kulal 1997: N = 25) were complemented with 17 museum specimens collected in

143 Chyulu Hills during 1938 (National Museums of Kenya, Nairobi). From these museum

144 specimens, DNA was extracted from blood, feathers or toe pads. The sampling location of

145 each population is shown in Fig. 1; further details on locations, sample sizes and genetic

146 parameters are provided in Table 1.

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148 Genetic analysis

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150

DNA was extracted using the Qiagen DNeasy TM Tissue Extraction Kit (Hilden, Germany) following the manufacturer´s protocol for blood and toe-pads or a user-developed one for

151 feathers (see De Volo et al ., 2008). Microsatellite loci were amplified using Thermozyme

152 Mastermix (Molzym, Bremen, Germany). The PCR products were visualised with an

153 automated sequencer (Beckmann, Coultier). Details of primer-specific PCR conditions and

154 multiplex-assignments are given in Habel et al . (2013). The following 12 microsatellite

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156 primers were genotyped: Cu28, LZ44, LZ41, LZ22, LZ45, LZ14, LZ54, LZ35, Mme12,

LZ18, LZ50, and LZ2. The forward primer of each pair was 5´-labelled with the fluorescent

157 dyes BMN-6 or CY5. Allele sizes were scored against the internal standard ROX-400SD

158 using GENEMAPPER 3.5 (Applied Biosystems).

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160 Statistics on genetic data

161 We used the program MICROCHECKER 2.2.3 (Van Oosterhout et al ., 2004) to test for

162 patterns indicating stutter bands, large allele dropout or null alleles (Selkoe and Toonen,

163 2006). The mean number of alleles per population ( A ), allelic richness ( AR ) and locus-specific

164 allele frequencies were calculated with FSTAT 2.9.3.2 (Goudet, 1995). Calculations of

165 observed ( H o

) and expected ( H e

) heterozygosity, tests for Hardy-Weinberg equilibrium

166 (HWE) and linkage disequilibrium (LD). Recent changes in effective population size were

167 analysed with BOTTLENECK 1.2.02 (Cornuet and Luikart, 1996).

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169 Hierarchical and non-hierarchical genetic variance analysis (AMOVAs) was performed with

170 ARLEQUIN 3.1 (Excoffier et al ., 2005). AMOVAs were computed using the microsatellite-

171 specific R -statistics (Slatkin, 1995; Selkoe and Toonen 2006). The most probable number of

172 genetic clusters without a priori definition of groups was inferred with STRUCTURE 3.1

173 (Hubisz et al . 2009). The batch run function was applied to carry out a total of 100 runs (10

174 each for one to ten clusters), i.e. K = 1 to K = 10. Replicate runs allowed us to calculate means

175 and standard deviations for fixed K -values. For each run, burn-in and simulation lengths were

176 150,000 and 500,000, respectively. Since log probability values for K values were earlier

177 shown to be unreliable in some cases (Evanno et al . 2005), we calculated the more refined ad

178 hoc statistic ∆ K , based on the rate of change in the log probability of data between successive

179 K values. Mantel tests were applied to test for correlations between genetic and geographic

180 distances at a distributional (i.e. after merging individuals within each mountain massif and

181 creating four groups, Mt. Kasigau, Taita Hills, Chyulu Hills and Mt. Kulal) and regional (i.e.

182 across all 11 Taita populations) scale. Matrices of genetic distances between populations were

183 calculated based on Cavalli-Sforza and Edwards (1976) distances and as pairwise R st

using

184 ARLEQUIN 3.1. A total of 5000 permutations were performed to infer levels of statistical

185 significance.

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186

187 To assess the level and direction of gene flow at the same two geographic scales, we

188 estimated the proportion of non-migrants and the source of migrants for each population by

189

190 using a Markov chain Monte Carlo (MCMC) algorithm in BAYESASS 1.3 (Wilson and

Rannala, 2003). We performed 9*10

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iterations with 3*10

6

iterations discarded as burn-in.

191 Delta values of m = 0.30, P = 0.15, and F = 0.15 yielded an average number of changes

192 within the accepted range (Wilson and Rannala, 2003).

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194 Phenotypic analyses

195 We measured wing length (mm), tarsus length (mm) and body mass (g) to test for potential

196 phenotypic differentiation among regional population clusters. We tested for auto-correlation

197 among the three characters using a MANCOVA. The obtained residuals were used for

198 subsequent analyses to adjust for potential allometry. As no significant auto-correlation was

199 detected, differences in morphometrics between populations were analysed by orthogonal

200 squares ANOVA in combination with post-hoc Tukey tests. We used principal component

201 analysis (PCA) to reduce the data complexity and to determine traits for which populations

202 were significantly diverged.

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204 Species Distribution Modelling

205 Geo-referenced species records were compiled from own field data supplemented with data

206 from specimens housed in the collections of the National Museums of Kenya (NMK, Nairobi,

207 Kenya), the Zoological Research Museum Alexander Koenig (ZFMK, Bonn, Germany), the

208 Zoological Museum Kopenhagen (ZMUC, Denmark), and records from the Global

209 Biodiversity Information Facility (GBIF), as well as from various publications (Zimmerman

210 et al ., 1996; Borghesio and Laiolo, 2004; Mulwa et al ., 2007; Redman et al ., 2009).

211 Confounding effects resulting from spatial autocorrelation were minimized by randomly

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212 selecting one species record per 10 arc min grid cell (i.e. spatially filtering 195 records).

213 Current local climatic conditions were inferred from the WORLDCLIM 1.4 database with a

214 spatial resolution of 2.5 arc min (Hijmans et al ., 2005). Expected climatic conditions for 2080

215 were derived from four global circulation models (GCMs) (CCCMA-CGCM2, CISRO-MK2,

216 HCCPR HADCM3, NIES99). A2a and B2a scenarios developed by the Inter-governmental

217 Panel on Climate Change (IPCC, 2007) were spatially downscaled to 2.5 arc min (Ramirez

218 and Jarvis, 2008). As each climate data set comprised 19 bioclimatic variables (Busby 1991),

219 we used pairwise squared Pearson’s correlation coefficients to quantify multi-colinearity

220 (Heikkinen et al ., 2006). In case of R

2

> 0.75, one variable of each pair that was considered

221 biologically most relevant was retained for species distribution modeling. This procedure

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224

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226 resulted in ten bioclimatic variables, i.e. ‘annual mean temperature’ (bio1), ‘isothermality’

(bio3), ‘temperature seasonality’ (bio4), ‘temperature annual range’ (bio7), ‘annual precipitation’ (bio12), ‘precipitation of wettest month’ (bio13), ‘precipitation of driest month’

(bio14), ‘precipitation seasonality’ (bio15), ‘precipitation of warmest quarter’ (bio18), and

‘precipitation of coldest quarter’ (bio19).

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228

229

SDMs were computed with MAXENT 3.3.3k, applying default settings and a logistic output format (Elith et al ., 2011; Phillips et al

., 2006; Phillips and Dudík, 2008) and using a training

230 area enclosed by a 100 km buffer around the species records (see recommendation by Mateo

231 et al ., 2010). To evaluate SDMs through the area under the receiver operating characteristic

232 curve (AUC; Swets, 1988), a total of 100 SDMs were computed, each trained with 70% of the

233 species records and tested with the remaining 30%. Based on the output of these replicate

234 runs, average predictions scores were computed for past, current and future bioclimatic

235 conditions as suggested by each of the four GCMs. We selected the minimum MAXENT

236 score at a 5% sample omission rate as presence/absence threshold. Non-analogous climatic

237 conditions within projection areas exceeding those that a SDM was trained for, may reduce

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238 the reliability of predictions (Elith et al.

, 2010; Fitzpatrick and Hargrove, 2009; Rocchini et

239 al ., 2011). This potential source of uncertainty was quantified in a spatially explicit way in

240 each scenario by using multivariate environmental similarity surfaces (MESS; Elith et al .,

241 2010). Climatic conditions projected for the mid Holocene climate optimum (MH, 6,000

242 years BP) were extracted from CCSM and MIROC simulations available through the PMIP 2

243 database (Braconnot et al ., 2007) and spatially downscaled following the same technique as

244 the 21,000 years BP data, which is described in detail in Peterson and Nyári (2007).

245

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246 RESULTS

247 Genetic diversity

248 The following locality*loci combinations showed significant deviations from Hardy-

249 Weinberg equilibrium due to the presence of null alleles: Chyulu-1938: ZL22; Fururu: ZL44;

250 Ndiwenyi: ZL14, ZL54, Mme12; Ngangao: ZL22, ZL14; Mbololo: ZL14. Samples from Mt.

251 Kulal showed no deviations from Hardy-Weinberg equilibrium, and for Ronge we did not

252 obtain valid results due to small sample sizes. After Bonferroni correction for multiple testing,

253 linkage disequilibrium was not significant in any pair of loci. Locus- and locality-specific

254

255 allele frequencies are listed in Appendix S1. Microsatellite DNA polymorphisms ranged between 2 (ZL41, Mme12, Cu28) and 12 (Zl49) alleles per locus, with a mean of 4.7 ± 2.3

256 alleles/locus and a total of 61 alleles across all loci. Allele sizes did not significantly differ

257 between recent and historic samples (sampling years are given in the list of allele frequencies

258 in Appendix S1). A total of 26 out of 61 alleles (43%) were restricted to single mountains.

259 The proportions of private alleles per population are listed in Table 1.

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261 Mean numbers of alleles ( A ), allelic richness ( AR ), proportions of private alleles ( AP ), and

262 percentages of expected ( H e

) and observed ( H o

) heterozygosity did not significantly differ at

263 regional level among the mountain populations (Kruskal-Wallis ANOVA, all p > 0.05).

264 Current and historic estimates (i.e. inferred from museum specimens collected in the same

265 forests) did not significantly differ for the following pairwise comparisons in the Taita Hills

266 (Ngangao 1990-2009, Mbololo 1990-2009, Mbololo 2000-2009), Chyulu Hills (1938-

267 current), and Mt. Kulal (1997-2010) (paired comparisons per fragment including time

268 intervals as co-variable, population-wise U-tests: all p>0.05). The following populations from

269 the Taita Hills showed a significant excess of homozygotes (tested over all loci): Vuria,

270 Ngangao, Ndiwenyi, Chawia, Fururu, Macha (all p < 0.05). Population- and mountain-

271 specific values of genetic diversity are listed in Table 1.

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272

273 Genetic population structuring

274 The best supported model assigned individuals to two genetic clusters ( K = 2 ): a first cluster

275 comprising individuals from the Taita Hills and Mt. Kasigau, and a second one comprising

276 individuals from Chyulu Hills and Mt. Kulal. While this model effectively yielded the

277 strongest statistical support (Fig. 2), Hausdorf and Hennig (2010) caution against clustering

278 genotypes in few groups. The second best models assigned individuals to seven genetic

279 clusters, thereby (i) splitting individuals from the Taita Hills and Mt. Kasigau, (ii) lumping

280

281 individuals from the Chyulu Hills and Mt. Kulal, and (iii) assigning individuals from the Taita

Hills to a very heterogeneous cluster (Fig. 2). ∆K values of all different models are listed in

282 Appendix S2.

283

284 At a regional scale, the level of genetic variance among Z. poliogaster populations from Mt.

285 Kasigau, Taita Hills, Chyulu Hills and Mt. Kulal was 11.1878 ( R

ST

: 0.5488, p < 0.001).

286 Hierarchical variance analysis assigned the strongest genetic split between the Chyulu Hills

287 and the neighbouring Taita Hills (<100 km geographic distance) with a genetic variance of

288 14.6971 ( R

CT

: 0.6245, p < 0.001), while the remote Mt. Kulal and Chyulu populations (>600

289 km geographic distance) showed comparatively poor genetic differentiation (10.9803, R

CT

:

290 0.5079, p < 0.001). Within the Taita Hills, the 11 remnant populations showed significant

291 genetic differentiation (0.6885, R

ST

: 0.0757, p < 0.001), partitioned over two spatial scales,

292 i.e. between the two main mountain isolates Dabida and Mbololo (0.7642, R

CT

: 0.0795, p <

293 0.05) and within Dabida (0.4684, R

ST

: 0.0504, p < 0.001). In contrast, the southern- and

294 northernmost populations of the Chyulu Hills were not genetically differentiated (-0.0179,

295 R

ST

: -0.0026, p > 0.05) despite comparable geographic distances (see Fig. 1). The level of

296 genetic differentiation between Dabida and Mbololo increased over a 19 year period from

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297 non-significant in 1990 to highly significant in 2009 (1990: 0.0044, R

CT

: 0.0006, p > 0.05;

298 2009: 0.6871, R

CT

: 0.0930, p < 0.001). All values are listed in Table 2.

299

300 Mantel tests did not yield significant correlations between genetic and geographic distances at

301 regional (among four mountain groups, Mt. Kasigau, Taita Hills, Chyulu Hills and Mt. Kulal;

302 r = 0.32, p = 0.13) and local (11 Taita Hills forest fragments; r = -0.20, p = 0.90) scales. While

303 the overall rate of genetic exchange among the four Z. poliogaster mountain groups was low,

304 there was weak gene flow detected among the 11 Taita Hills populations. The small

305 Mwachora and Ndiwenyi populations thereby seemed to act as sources (see Table 3B).

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307 Phenotypic structures

308 Principal component analysis revealed a morphological split between populations from the

309 Taita Hills and those from the Chyulu Hills and Mt. Kulal (Fig. 3A), while individuals from

310 Mt. Kasigau took an intermediate position. Taita individuals were significantly smaller and

311 lighter than individuals from Mt Kulal and the Chyulu Hills (ANOVA: Tukey post-hoc

312 comparisons p < 0.01), while individuals from Mt Kasigau showed intermediate values.

313 Populations from different mountains did not significantly differ in morphology (t-test: p >

314 0.1). A PCA bi-plot showed a strong congruence between morphological and genetic

315 differentiation at a regional level, i.e. separating the Chyulu Hills and Mt. Kulal populations

316 from those of the Taita Hills and Mt. Kasigau (Fig. 3B). Population means and standard

317 deviations of all phenotypic data are listed in Appendix S3.

318

319 Species Distribution Modelling

320 Based on 100 replicates, average training and test AUC scores were 0.932 and 0.871,

321 respectively. Variable bio1 (`annual mean temperature’) (35.0%) contributed most strongly to

322 the SDMs, followed by bio18 (‘precipitation of warmest quarter’) (16.9%), bio19

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323 ‘precipitation of coldest quarter’ (10.1%), bio14 (8.3%), bio3 (8.2%), bio15 (5.6%), and bio7

324 (5.3%). All other variables contributed less than 5% on average.

325

326 The current potential distribution of Z. poliogaster covers major parts of the East African

327 highlands such as Pare Mts. Mt. Meru, Kilimajaro, Taita Hills, Chyulu Hills, Central Kenyan

328 Highlands, Cherangani Hills, and the northern Kenyan Highlands (Mt. Kulal and Mt. Nyiru)

329 (Fig. 4). The projected past distribution of Z. poliogaster showed a strong differentiation into

330 three areas with suitable climatic conditions for 6,000 years BP, covering (i) parts of the

331 Eastern Arc Mountains, (ii) Central Kenyan Highlands, and (iii) Ethiopian Highlands. The

332 distribution range in Southern Kenya (Chyulu Hills, Taita Hills and Mt. Kasigau), however,

333 did not reflect the species´ specific climatic niche (Fig. 4). When projecting the SDMs to

334

335 future climate change scenarios A2a and B2a as proposed by IPCC (2007) for 2080, a severe retraction in the distribution of the species´ climatic niche is projected. Particularly strong

336 effects are expected near the southern distribution edge (Eastern Arc Mountains), but also

337 across parts of the Central Kenyan Highlands and northern Kenya. Suitable climatic exclaves

338 might remain in some areas of the Pare and Usambara Mountains, parts of the Central Kenyan

339 Highlands and restricted areas in the Ethiopian highlands (Fig. 4).

340

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341 DISCUSSION

342 Populations of Z. poliogaster are genetically and phenotypically differentiated over both,

343 regional and local scales. Morphological and genetic data indicate that distinct mountain

344 specific clusters evolved independently from each other. We found no correlation between

345 intraspecific and geographic distance suggesting that geographic isolation is not a main driver

346 of differentiation in this species. On a regional level (here the Taita Hills forest archipelago)

347 we found significant genetic differentiation even among neighbouring populations (Dabida

348 and Mbololo mountains). Temporal analyses point towards an increase in genetic

349 differentiation over time between the Taita Hills populations, while the adjoining Chyulu

350 Hills populations do not show such pattern.

351

352 Effects of long-term disjunction

353 Based on our analyses, we identify two major genetic and morphometric clusters within the

354 studied region (Fig. 4). A first cluster comprises the two southernmost mountain populations,

355 Mt. Kasigau and the Taita Hills that are separated by 60 km of dry savannah. A second cluster

356 comprises both populations of the Chyulu Hills (60 km distant from the Taita Hills) and the

357 one from Mt. Kulal, located 600km north. This intraspecific clustering may reflect the

358 geological history of the mountain massifs: Mt. Kasigau and the Taita Hills represent the

359 northernmost edge of the Eastern Arc Mts. which evolved very early during the Precambrian

360 (White, 1978). In contrast, the other two mountain massifs, Chyulu Hills and Mt. Kulal are

361 geologically much younger (Dimitrov et al ., 2012). The influence of these contrasting

362 geological ages on evolutionary processes have been demonstrated for other species, with

363 deep inter- and intraspecific splits detected in taxa inhabiting the Eastern Arc Mts. (Bowie et

364 al ., 2006; Dimitrov et al . 2012; Fuchs et al ., 2011; Tolley et al ., 2011). Yet, to formally test

365 this hypothesis in the genus Zosterops , phylogenetic analyses and robust estimates of

366 divergence times between mountain-specific lineages are required.

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367

368 An alternative explanation for the observed within-taxon differentiation is based on climatic

369 fluctuations of the last thousands of years (including the glacial-interglacial cycles). The last

370 glaciation ended about 10,000 years ago and caused major forest contractions. During such

371 glaciation many forest species most probably expanded their ranges and colonize isolated

372 forest massifs (Hamilton, 1982). As indicated by the results from SDMs, the past distribution

373 of Z. poliogaster (6000 years BP) was strongly divided into a southern (Eastern Arc) and

374 northern (Central Kenyan Highlands) distribution range. This could be still reflected by our

375 data-sets. The obtained differentiation pattern and the lack of an isolation-by-distance further

376 indicate that the geographic distance is not the most important force driving the genetic and

377 morphological differentiation of these populations.

378

379 In addition to this major genetic split, we detected significant genetic differentiation within

380 mountain massifs, e.g. between populations from two Taita Hills isolates (Mbololo and

381 Dabida) that are separated by a small valley only (cf. Callens et al ., 2011). These findings

382 underline the specific environmental demands (moist and cool climatic conditions, see SDM

383 results) and resulting strong geographical restriction of Z. poliogaster to higher elevations

384 (Mulwa et al.

, 2007; Redman et al ., 2009).

385

386 Habitat persistence and habitat change

387 The restriction of gene flow among remnant populations after the break down of landscape

388 connectivity is a commonly observed coherence (Knutsen et al ., 2000). However, only few

389 studies used historical data to empirically assess the impact of rapid landscape changes on the

390 intraspecific structure of populations. Temporal comparisons of the genetic structure of

391 populations from individuals sampled in the Taita Hills over a 19 years period indicate a

392 significant temporal increase in genetic differentiation. This is likely the result of severe

17

393 habitat fragmentation which has taken place in the Taita Hills during the past decades (Pellika

394 et al ., 2009).

395

396 Several studies have addressed the negative effects of rapid ecosystem change on the viability

397 of populations (Fahrig, 2003), also in the EAM. For instance, Lens et al . (1999) showed that

398 levels of fluctuating asymmetry in Z. poliogaster and six sympatric forest bird species were

399 four to seven times higher for birds in the smallest, most degraded fragments. Increased levels

400

401 of FA have been correlated with reductions in the growth rates and competitive ability of a range of organisms (see reviews by Møller, 1997; Møller & Thornhill, 1998), as well as with

402 reduced survival probabilities in the critically-threatened Taita thrush ( Turdus helleri ) (Lens

403 et al., 2002). In the latter species, Galbusera et al . (2000) also reported severe levels of genetic

404 drift in small, degraded populations. A comparable pattern as found for the Mountain White-

405 eye was observed in the Spanish imperial eagle ( Aquila adalberti ) of which the historic

406 panmictic population network recently collapsed into a scatter of isolated remnant populations

407 (Martinez-Cruz et al ., 2007). The fact that Z. poliogaster individuals from the

408 anthropogenically fragmented forest patches of the Taita Hills have a lighter weight which

409 might be a plastic response to the lower habitat quality. In contrast, populations from more

410 undisturbed fragments, i.e. where habitat conditions remained fairly stable during the recent

411 past, such as in the Chylu Hills, showed higher levels of genetic diversity and weaker genetic

412 differentiation.

413

414 Such contrasting intraspecific signatures of habitat subdivision in two adjoining mountain

415 massifs might be explained by two different scenarios. First, while the Taita Hills forest

416 experienced rapid habitat fragmentation and degradation, the Chyulu Hills are covered by

417 forest-grassland mosaics that persisted during the past hundreds of years. While the current

418 degree of forest fragmentation in the Chyulu and Taita Hills is roughly comparable, both

18

419 areas hence underwent fundamentally different habitat histories. The coinciding patterns of

420 genetic differentiation and habitat history suggest that populations affected from fast habitat

421 change (e.g. the Taita Hills) might suffer severely, whereas populations living in (e.g. the

422 Chyulu Hills) are less affected. Thus, fragmented habitats must not always affect species

423 negatively (Vucetich et al ., 2001; Habel and Schmitt, 2012; Habel and Zachos, 2013).

424

425 Climate warming threats intraspecific diversity

426 Our biometric and genetic analyses suggest a high level of intraspecific uniqueness for single

427 mountain areas. 43% of all detected alleles are geographically restricted to single mountain

428 massifs. This high level of variability and intraspecific endemicity is threatened by a

429 combination of direct (see above) and indirect factors. Strong demographic pressure across

430 major parts of Africa and the increasing need for agricultural products and thus agricultural

431 land lead to increased deforestation (Pellika et al ., 2009). In addition, our SDM projections

432 highlight the relevance of cool and moist climatic conditions for this species (the factor

433 `annual mean temperature’ contributes 35.0%, ‘precipitation of warmest quarter’ contributes

434 16.9%, and ‘precipitation of coldest quarter’ contributes 10.1% to the explanatory power of

435 the suitability of habitats for Z. poliogaster ). These models further suggest that climate

436 change will cause warmer and drier conditions leading to a decline of suitable habitats for Z.

437 poliogaster (Fig. 4). This might lead to extinction of local populations and result in the loss of

438 intraspecific uniqueness.

19

439 Acknowledgements

440 The research was financed by the German Academic Exchange Service (DAAD) and the

441

442

Natural History Museum Luxembourg (MNHN Luxembourg). We thank Titus Imboma,

Onesmus Kioko (Nairobi, Kenya) and Dirk Louy, Thomas Schmitt and Sönke Twietmeyer

443 (Trier, Germany) for field assistance. We thank Hans Matheve (Ghent, Belgium) and two

444 anonymous referees for improving a draft version of this article.

20

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603

25

610

604 Figure 1: Overview of the 16 sampling locations of Zosterops poliogaster . The inset (B)

605 details the Taita Hills sampling sites. 1: Mt. Kasigau, 2: TH-Chawia, 3: TH-Fururu, 4: TH-

606 Macha, 5: TH-Mwachora, 6: TH-Ndiwenyi, 7: TH-Ngangao, 8: TH-Vuria, 9: TH-Wundanyi,

607 10: TH-Yale; 11: TH-Ronge, 12: TH-MBololo, 13: CH-Satellite, 14: CH-Simba valley, 15:

608 Chyulu Hills-1938; 16: Mt. Kulal. Numbers of sampling sites and names of localities coincide

609 with Table 1. Abbreviations: TH = Taita Hills, CH = Chyulu Hills.

26

611 Figure 2: Bayesian structure analyses of populations from Zosterops poliogaster performed

612 with STRUCTURE (Hubisz et al ., 2009), for K = 1-10. Results supported by highest Δ K

613 values ( K = 2 and K = 7) are presented, distinguishing the mountain population of Mt.

614 Kasigau and Taita Hills (TH), while Chyulu Hills (CH) clusters together with Mt. Kulal.

615 Names of populations coincide with other figures and tables.

616

27

617 Figure 3: A: Principal component analysis (PCA) based on three biometric characters

618 segregates the individuals from the Taita Hills (open triangles) from Chyulu Hills (Simba and

619 Satellite) (open dots) and the individuals from Mt. Kulal (open squares). Individuals from Mt.

620

621

Kaisgau (black dots) scores intermediate between both groups. Axis 1 correlates highly with body mass (r

2

= 0.54, p < 0.01). B: A PCA biplot for average morphological (black dots) and

622 genetic R

ST

distances (open circles) segregates populations from Chyulu Hills (Simba,

623 Satellite) and Mt Kulal from the populations from Taita Hills. and Mt. Kasigau.

624

0.1

0

-0.1

-0.2

A

0

PCA 1

0.2

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

B

Simba

Simba

Satellite

Satellite

Mt. Kulal

Mt. Kulal

Mt. Kasigau

Taita

-0.6 -0.4 -0.2

0 0.2

0.4

PCA 1

28

625 Figure 4: Projections of the distribution of Zoterops poliogaster from past, present to future.

626 Warmer colours indicated a higher environmental suitability for the species, unsuitable areas

627 are indicated in light grey. Darker areas indicate areas with non-analogues climatic conditions

628 relative to the training area of the SDMs as identified by MESS analyses. A) Currently

629 realized and potential distribution of Zosterops poliogaster in East Africa, as well as average

630 projections of its currently realized niche and future anthropogenic climate change scenarios

631 provided by the 4 th

IPCC Assessment (A2a and B2a) for 2080. Species records are indicated

632 by black crosses; light grey areas are suggested to be unsuitable; dark grey shading indicates

633 extrapolation of the SDM outside the environmental training range as quantified by MESS. B)

634 Potential distribution assuming under two palaeoclimatic models (CCSM – A&C; MIROC –

635 B&D) under environmental conditions as can be expected for around 6,000 (A&B) and

636 21,000 years BP (C&D).A)

29

637

30

638 B)

639

31

640 Table 1: Parameters of genetic diversity for Zosterops poliogaster (averaged across loci). Given are site number, locality, forest type, number of

641 sampled individuals, mean number of alleles ( A ), allelic richness ( AR ), mountain specific private alleles ( AP ), percentage of expected heterozygosity

642 ( H e

), and percentage of observed heterozygostiy ( H o

). Allelic richness was calculated based on the lowest number of individuals available for a

643 population, which were 9 individuals from forest patch Yale (as we excluded populations from Furia and Ronge from this analysis). Abbreviations:

644 TH = Taita Hills, CH = Chyulu Hills, P = Pristine forest, HC = habitat change, S = stable conditions.

Site Locality-Years

1 Mt. Kasigau

2 TH-Chawia

3 TH-Fururu

4 TH-Macha

5 TH-Mwachora

6 TH-Ndiwenyi

7

TH-Ngangao-1990

TH-Ngangao-2009

8 TH-Vuria

9 TH-Wundanyi

10 TH-Yale

11 TH-Ronge

TH-MBololo-1990

12 TH-MBololo-2000

TH-MBololo-2009

Mean (±sd)

13 CH-Satellite

14 CH-Simba valley

15 Chyulu Hills-1938

Mean (±sd)

History N A

P

HC

HC

HC

HC

HC

HC

HC

HC

HC

HC

HC

HC

HC

HC

S

S

S

22 1.7

28 2.4

25 2.3

27 2.5

13 1.6

31 2.5

28 1.8

21 1.9

6 1.9

16 1.7

9 2.4

4 1.9

27 2.2

14 1.7

21 1.5

AR AP

1.5 0/22

AP[%]

0

1.9 4/31 12.9

1.9 4/30 13.3

1.9 5/33 15.2

1.6 1/21 4.8

1.9

1.9

1.5

-

1.8

1.8

-

1.8

1.8

1.7

8/32

3/22

2/25

2/25

2/23

4/31

2/26

6/28

1/22

1/20

25.0

13.3

8.0

8.0

8.9

12.9

7.8

21.4

4.5

5.0

-

2.0

(±0.4)

20 1.8

1.8

(±0.2)

-

10.7

(±6.6)

1.7 2/24 8.3

15

17

1.9

1.8

1.8 2/25 8.0

1.8 2/24 8.3

1.9 1.8 - 8.2

H o

[%]

34.3

25.0

21.4

21.2

34.9

16.9

29.4

26.5

26.7

45.4

36.7

48.2

46.9

33.9

31.3

31.9

(±9.5)

31.7

33.9

27.2

H e

[%]

35.0

27.2

28.3

31.2

35.2

23.3

30.9

25.2

39.9

40.7

39.5

25.0

32.9

24.9

23.5

30.9

(±6.1)

41.0

45.2

43.2

32.8 43.1

32

16

Mt. Kulal-1997

Mt. Kulal-2010

Mean (±sd)

P

P

(±0.1) (±0.0)

25 2.4 1.9 6/31

(±0.2)

19.4

(±1.6)

38.6

(±2.9)

34.1

21 2.2 2.1 7/28 25.0 40.8 34.8

-

2.3

(±0.1)

2.0

(±0.1)

-

22.2

(±3.9)

39.7

(±1.6)

34.5

(±0.5)

33

645 Table 2: Non-hierarchical and hierarchical analyses on molecular variance (AMOVA) to analyse genetic differentiation among/between mountain

646 groups e.g. species, among individuals within populations, and within individuals. Variance values (top line) with the respective R statistics (in

647 parenthesis below). Groupings were created following Structure analyses (Fig. 2). Abbreviations: *: p < 0.05, **: p < 0.01, ***: p < 0.0001.

648

649 Non-hierarchical variance analyses

650

651

Group

All populations

Taita Hills

Chyulu Hills

Ngangao

Ngangao vs vs

Mbololo past

Mbololo recent

Mt. Kasigau vs Mt. Kulal

Hierarchical variance analyses among populations

(R

ST

)

6.2668

(0.4219***)

0.6885

(0.0757***)

-0.0179

(-0.0026)

0.0044

(0.0006)

0.6871

(0.0930**)

14.6219

(0.5846***)

Among individuals within populations (R

IS

)

-0.1439

(-0.0168)

-0.5478

(-0.0652)

0.8502

( 0.1208)

-0.1963

(-0.0245)

-0.6952

(-0.1038)

0.8331

(0.0802)

Within individuals

8.7299

8.9505

6.1857

8.2143

7.3942

9.5589

Group

Mt. Kasigau vs Taita Hills vs

Chyulu Hills vs Mt. Kulal

Taita Hills,

Among groups or species (R

CT

)

11.1878

(0.5488***)

0.7642

Among populations within groups (R

SC

)

0.6137

(0.0667***)

0.4507

Within individuals

8.7299

8.9505

34

Ngangao vs Mbololo

Mt. Kasigau vs Taita Hills

Mt. Kasigau vs Chyulu Hills

Taita Hills vs Chyulu Hills

Taita Hills vs Mt. Kulal

Chyulu Hills vs Mt. Kulal

(0.0795*)

1.4441

(0.1428*)

20.7425

(0.7818***)

14.6971

( 0.6245***)

12.6453

( 0.5609***)

10.9803

( 0.5079***)

(0.0509***)

0.6998

(0.0807***)

0.0341

(0.0059)

0.6294

( 0.0712***)

0.6585

(0.0665***)

-0.1393

(-0.0131)

8.5150

5.4107

8.5587

9.4979

9.5000

35

652 Table 3: Results of five independent runs of a non-equilibrium Bayesian assessment of

653 migration proportion by population calculated with the programme BAYESASS (Wilson and

654 Ranalla, 2003) at A) the distributional scale and B) the regional scale (i.e. within the Taita

655 Hills). Bolded terms = values >10% of the proportion of non-migrants within a population.

656 Values in columns (populations of origin in first column) represent migrant genes donated to

657 other populations. Calculations were performed for the four mountain groups Mt. Kasigau,

658 Taita Hills, Chyulu Hills and Mt. Kulal.

659

660

661

A)

Mt. Kasigau

Taita Hills

Chyulu Hills

Mt. Kulal

Mt. Kasigau Taita Hills Chyulu Hills Mt. Kulal

0.9751

0.0133

0.0057

0.0011

0.9979

0.0005

0.0031

0.0029

0.9911

0.0025

0.0023

0.0027

0.0059 0.0005 0.0029

0.9925

36

662

663

B)

TH-Chawia

TH-Fururu

TH-Macha

TH-Yale

Chawia Fururu Macha Mwachora Ndiwenyi Vuria Wundanyi Yale Ngangao Mbololo Ronge

0.6859

0.0053 0.0043 0.0029 0.0035 0.0146 0.0074 0.0117 0.0081 0.0110 0.0178

0.0039

0.0039

0.6783

0.0043

0.003

0.6789

0.0024

0.0028

TH-Mwachora 0.0556 0.0470 0.0120

0.9611

TH-Ndiwenyi 0.2074 0.1819 0.2638

0.0068

TH-Vuria 0.0038 0.0041 0.0032 0.0021

TH-Wundanyi 0.0041 0.0048 0.0034 0.0024

0.0040 0.0042 0.0035 0.0019

0.0015 0.0136 0.0068 0.0113 0.0031 0.0102 0.0147

0.0018 0.0150 0.0078 0.0098 0.0034 0.0093 0.0149

0.0021 0.0214

0.1335 0.1229

0.0079 0.0237 0.0239

0.9734

0.0763 0.0931 0.0500

0.2470

0.0141 0.0458

0.0019

0.7080

0.0065 0.0116 0.0030 0.0095 0.0153

0.0017

0.0021

0.0134

0.0125

0.6856

0.0069

0.0109

0.6975

0.0035

0.0028

0.0104

0.0093

0.0158

0.0147

TH-Ngangao 0.0065 0.0047 0.0038 0.0024

TH-MBololo 0.0036 0.0042 0.0036 0.0024

TH-Ronge 0.0037 0.0040 0.0034 0.0021

0.0021 0.0144 0.0071 0.0111

0.6858

0.0114 0.0159

0.0020 0.0128 0.0067 0.0111 0.0034

0.8837

0.0161

0.0022 0.0123 0.0069 0.0103 0.0034 0.0095

0.8215

37

664 Appendix S1: Allele-frequencies calculated for all populations and loci used for this study. Private alleles restricted to one population or mountain

665 area are marked in bold. Population numbers coincide with Table 1 and Figure 1, historic samples are marked with respective sampling years.

666

Zl54

Zl54

Zl35

Zl35

Zl35

Zl35

Zl35

Zl35

Zl35

Zl14

Zl14

Zl14

Zl14

Zl14

Zl14

Zl14

Zl54

Zl41

Zl41

Zl22

Zl22

Zl22

Zl22

Zl22

Zl45

Zl45

Zl45

Zl45

Zl45

Zl45

Zl45

Locus

Cu_28

Cu_28

Zl44

Zl44

Zl44

3

4

5

6

7

2

3

1

2

5

6

7

1

1

2

3

4

2

3

4

5

6

7

3

4

5

1

1

2

1

2

Allele Size

1

2

162

164

1

2

3

216

220

224

122

124

121

123

125

127

129

131

133

134

140

142

144

146

148

150

120

112

116

118

120

122

124

82

86

143

145

149

155

157

106

Abbreviations: MtKa = Mt. Kasigau, TH = Taita Hills, CH = Chyulu Hills, MtKu = Mt. Kulal.

MtKa

-

TH

-

TH

-

TH

-

TH

-

TH

-

TH

1990

TH

-

TH

-

TH

-

TH

-

TH

-

TH

1990

TH

2000

TH

-

CH

1938

CH

-

CH

-

MtKu

1990

MtKu

-

1 2 3 4 5 6 7 7 8 9 10 11 12 12 12 13 14 15 16 16

0.4524 0.0179 0.0800 0.0179 0.0000 0.0000 0.0000 0.0000 0.0000 0.0238 0.0862 0.0161 0.0250 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.5476 0.9821 0.9200 0.9821 1.0000 1.0000 1.0000 1.0000 1.0000 0.9762 0.9138 0.9839 0.9750 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0323 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

1.0000 1.0000 0.9600 1.0000 1.0000 0.9677 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 0.8667 0.9286

0.0000 0.0000 0.0400 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1333 0.0714

0.9524 0.9643 1.0000 0.9821 1.0000 0.9839 1.0000 1.0000 0.9444 0.9762 0.9483 0.9839 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

0.0476 0.0357 0.0000 0.0179 0.0000 0.0161 0.0000 0.0000 0.0556 0.0238 0.0517 0.0161 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0179 0.0000 0.0000 0.0000 0.0484 0.0000 0.0000 0.0000 0.0000 0.0185 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.9762 0.9107 0.9400 1.0000 0.9615 0.9516 1.0000 0.8750 0.8889 1.0000 0.9444 0.9677 1.0000 0.8889 1.0000 0.1500 0.0667 0.1304 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1724 0.0714

0.0238 0.0714 0.0600 0.0000 0.0385 0.0000 0.0000 0.1250 0.1111 0.0000 0.0370 0.0323 0.0000 0.1111 0.0000 0.6250 0.8667 0.7609 0.8276 0.9286

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1250 0.0667 0.1087 0.0000 0.0000

0.0000 0.0800 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0238 0.2400 0.1905 0.2400 0.3333 0.2759 0.2500 0.4667 0.5000 0.2500 0.2586 0.3571 0.3421 0.3889 0.1667 0.1000 0.1000 0.1087 0.1500 0.1786

0.0000 0.0000 0.0000 0.0600 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0357 0.0000 0.0000 0.0000 0.2250 0.2667 0.2391 0.2167 0.0357

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0526 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.9762 0.6800 0.8095 0.6600 0.6667 0.7241 0.7500 0.5333 0.5000 0.7500 0.7414 0.6071 0.6053 0.6111 0.8333 0.6750 0.5667 0.6522 0.3667 0.6071

0.0000 0.0000 0.0000 0.0400 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0667 0.0000 0.2667 0.1786

0.0000 0.0192 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.1154 0.0000 0.0200 0.1818 0.0000 0.0000 0.1333 0.1667 0.0000 0.0536 0.0000 0.0263 0.0000 0.0000 0.9000 0.9643 0.9348 0.1786 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0385 0.2000 0.0000 0.0000 0.0000 0.0714 0.0000 0.0526 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

1.0000 0.8654 1.0000 0.9600 0.8182 0.9615 0.8000 0.8667 0.8333 1.0000 0.8750 1.0000 0.8947 1.0000 1.0000 0.1000 0.0357 0.0652 0.4464 0.7308

0.0000 0.0000 0.0000 0.0200 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0263 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.2321 0.1538

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1429 0.1154

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0263 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

1.0000 0.9815 0.9783 1.0000 1.0000 0.9655 0.9000 1.0000 1.0000 1.0000 1.0000 1.0000 0.9737 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

0.0000 0.0185 0.0217 0.0000 0.0000 0.0345 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0556 0.0000 0.0000 0.0000 0.0000 0.6842 0.6154 0.6591 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0192 0.0000 0.0000 0.0000 0.0000 0.0000 0.0484 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.6190 0.8636 0.9500 0.9630 1.0000 0.9423 1.0000 1.0000 1.0000 1.0000 0.9444 0.9516 1.0000 1.0000 1.0000 0.3158 0.3846 0.3409 0.0000 0.0000

0.0476 0.0000 0.0000 0.0185 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.4821 0.6667

0.3333 0.1364 0.0500 0.0185 0.0000 0.0385 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0417

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.3571 0.2500

38

Zl35

Mme12

Mme12

Zl18

Zl18

Zl18

Zl18

Zl18

Zl50

Zl50

Zl50

Zl50

Zl49

Zl49

Zl49

Zl49

Zl49

Zl49

Zl49

Zl49

Alleles

AP

1

2

3

4

5

1

2

3

4

8

1

2

1

2

3

4

5

6

7

8

135

142

146

128

130

134

136

140

127

130

133

136

100

102

104

106

108

110

112

114

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.1607 0.0417

1.0000 1.0000 1.0000 1.0000 1.0000 0.9655 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0345 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.2000 0.0625 0.1538 0.2500 0.0962 0.0833 0.0625 0.0625 0.1190 0.1379 0.0323 0.0263 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0172 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0690 0.0357

1.0000 0.8000 0.8750 0.7885 0.7500 0.8654 0.9167 0.8438 0.9375 0.8571 0.8276 0.9677 0.9474 0.9444 0.8750 1.0000 1.0000 1.0000 0.9310 0.9643

0.0000 0.0000 0.0625 0.0577 0.0000 0.0385 0.0000 0.0938 0.0000 0.0238 0.0172 0.0000 0.0263 0.0556 0.1250 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0000 0.0000 0.0400 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

0.0000 0.0417 0.0000 0.0200 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1.0000 1.0000 1.0000 0.9231 0.9643

0.2250 0.8542 0.7174 0.7600 0.9500 0.8393 0.7500 0.8182 0.6429 0.7105 0.6852 0.5968 0.5278 0.4000 0.7500 0.0000 0.0000 0.0000 0.0000 0.0000

0.7750 0.1042 0.2826 0.1800 0.0500 0.1607 0.2500 0.1818 0.3571 0.2895 0.3148 0.4032 0.4722 0.6000 0.2500 0.0000 0.0000 0.0000 0.0769 0.0357

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0526 0.3000 0.0435 0.0000 0.0000

0.0000 0.1400 0.0682 0.0000 0.3636 0.0179 0.0000 0.2500 0.3333 0.0000 0.0000 0.0000 0.0789 0.1500 0.0000 0.6316 0.4333 0.6739 0.4333 0.2143

0.0714 0.1800 0.3409 0.1667 0.4545 0.2679 0.2500 0.2500 0.4444 0.2381 0.1458 0.0345 0.1053 0.0500 0.1667 0.1053 0.1000 0.0870 0.0500 0.0000

0.0000 0.0200 0.0227 0.0417 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0417 0.0000 0.0000 0.0000 0.0000 0.2105 0.1667 0.1957 0.0167 0.0714

0.2857 0.3600 0.1591 0.3125 0.1818 0.3750 0.0833 0.1071 0.0556 0.3571 0.1875 0.2931 0.2632 0.0500 0.3333 0.0000 0.0000 0.0000 0.0500 0.0714

0.6429 0.3000 0.2955 0.4167 0.0000 0.2321 0.5000 0.3571 0.1111 0.4048 0.5208 0.2241 0.2105 0.3000 0.1667 0.0000 0.0000 0.0000 0.4333 0.6429

0.0000 0.0000 0.1136 0.0625 0.0000 0.0893 0.1667 0.0357 0.0000 0.0000 0.1042 0.4483 0.3421 0.4500 0.3333 0.0000 0.0000 0.0000 0.0167 0.0000

0.0000 0.0000 0.0000 0.0000 0.0000 0.0179 0.0000 0.0000 0.0556 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

22

0

31

4

30

4

33

5

21

1

32

8

22

3

25

2

25

2

23

2

31

4

26

2

28

6

22

1

20

1

24

2

25

2

24

2

31

6

28

7

39

667 Appendix S2: Results of the Structure analysis for different numbers of given groups ( K = 1-

668 10) analysed based on all individuals. Ln(Pr) is the natural logarithm of the probability

669 calculated using the Structure software that K is the correct number of populations. SD is the

670 standard deviation calculated from 10 independent runs. The ad hoc statistic Delta K is not

671 applicable for K = 1, and from the equation given in the methods section it is obvious that it

672 cannot be calculated for the highest K number either (because data for K = 1 are needed), and

673 is not proper for K = 2 (cf. Hausdorf and Hennig, 2010).

K

1

Ln(Pr) ± SD

-6881.01

± 0.03

∆K

-

2 -5310.51±0.32 4198.93

3 -5089.05

±

147.29 0.15

4 -4845.65

± 176.52

5 -4684.34

±

192.06

6 -4517.69

±

174.03

0.47

0.03

0.38

7 -4416.84±2.92

8 -4425.38

±

42.12

9 -4363.23

±

50.12

10 -4348.24

±

36.38

37.46

1.68

0.94

-

40

674 Appendix S3: Biometric measures for each population. Given are number of measured

675 individuals, length of the wing (cm), length of tarsus (cm), and body mass (g).

676

Locality + No

Mt. Kasigau-1

TH-Chawia-2

TH-Fururu-3

TH-Macha-4

N Wing Tarsus Weight

20

59,0 (±0,9)

21,0 (±0,5)

10,6 (±0,9)

25 59,0 (±1,2) 20,0 (±0,5) 10,9 (±0,6)

25 58,9 (±0,9) 19,8 (±0,5) 10,9 (±0,8)

31 58,4 (±1,7) 19,37 (±0,7) 11,01 (±0,8)

TH-Mwachora-5

TH-Ndiwenyi-6

13 58,9 (±1,8) 19,9 (±0,5) 10,6 (±0,6)

30 58,9 (±1,7) 19,7 (±0,6) 10,9 (±0,8)

TH-Ngangao 1990-7 27 58,7 (±1,3) 20,0 (±0,7) 10,5 (±0,8)

TH-Ngangao2010-7 20 58,5 (±2,0) 20,1 (±0,5) 9,8 (±1,0)

TH-Vuria-8

TH-Wundanyi-9

TH-Yale-10

6 59,0 (±1,3 19,4 (±0,7) 11,0 (±0,6)

16 58,8 (±1,4) 19,8 (±0,7) 10,5 (±0,6)

9 59,1 (

±

1,7) 20,3 (

±

0,26) 11,2 (± 0,4)

TH-Ronge-11 4 58,5 (±1,3) 19,1 (±0,9) 10,4 (±0,3)

TH-MBololo-1990-12 20 58,3 (±1,3) 19,9 (±0,5) 10,7 (±0,4)

TH-MBololo-2009-12 30 58,4 (±1,2) 20,2 (±0,6) 9,5 (±0,7)

CH-Satellite-13 25

62,9 (±1,6) 20,9 (±0,3)

12,7 (±1,6)

CH-Simba valley-14 10 61,1 (±1,7) 21,2 (±0,8) 11,4 (±0,6)

Mt. Kulal-1990-16 32 63,4 (±1,2) 21,7 (±0,6) 13,6 (±0,9)

41

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