Supporting Information Notes S1 and Figs S1–S3
Notes S1 Results and details on methods of analysis for the relationships between
flowering phenology and species geographic climate envelopes, flowering color,
phylogenetic patterns, and foliar C and N isotope ratios
Flowering color
Flower color of each species was assigned to a predominant color (purple, red, white, or
yellow). Species with mixed flower colors or variants of the primary colors were grouped
according to their closest color group or the group that most typically represented the
species. Plants with small or nondescript flowers were considered wind pollinated, which
we treated as a separate color category. When partitioned by flower color, mean FFD
among categories did not significantly differ (wind= 170 ± 4, purple = 167 ± 6, red = 175
± 10, white = 170 ± 3, yellow = 168 ± 2; P > 0.1) (Fig. S1). Yet, peak flowering was
earliest for species with purple flowers (May 11) and latest for species with yellow
flowers (June 26) and wind-pollinated species (June 24).
Phylogenetic patterns
To better understand patterns of FFD evolution, we assembled a phylogenetic hypothesis
including all angiosperm species for which FFD was measured and tested for
phylogenetic signal in FFD, a tendency for closely related species to have similar FFD.
Phylogenetic information was obtained using the Phylomatic tree assembly toolkit and
database (Webb & Donoghue, 2005) to graft individual species onto a phylogenetic
hypothesis for angiosperms (Davies et al., 2004). Phylogenetic signal in FFD was
quantified using the K statistic (Blomberg et al., 2003; Kembel et al., 2010), which
measures the phylogenetic signal in a trait compared to the signal expected under a
Brownian motion model of trait evolution. Higher values of K indicate greater
phylogenetic signal, with an associated P-value indicating whether the trait exhibits more
phylogenetic signal than expected by chance calculated based on comparison of the
observed signal to the expected signal from 1000 randomizations of the tip labels of the
phylogeny.
There was more phylogenetic signal in FFD than expected by chance (K = 0.43, P <
0.01). Taxonomic groups including the family Asteraceae and genera in the Poaceae such
as Sporobolus tended to flower later in the season (194 ± 5, 251 ± 5, respectively) than
taxonomic groups such as the Brassicaceae and the genus Carex in the Cyperaceae (112 ±
5, 116 ± 4, respectively) (Fig. S2).
Geographic ranges
To understand whether FFD was associated with macroclimatic distribution of species,
FFD were compared with climate envelope parameters of species (Craine et al., 2011).
Briefly, for each species, climate envelopes were generated from 1° occurrence data
restricted to the conterminous United States and acquired from the Global Biodiversity
Information Facility (www.gbif.org) in January 2010. Climate envelopes could be
generated for 424 of the 430 species for which we observed FFD. For each species
occurrence, we extracted 50-year MAT and MAP (1950-2000) from WorldClim
(www.worldclim.org). We then determined the 10% and 90% quantiles of MAT and
MAP to describe each species’ climate envelope. The 10% quantile was considered the
lower bound and the 90% quantile was considered the upper bounds for MAT and MAP
for each species.
The geographic range of species was weakly associated with FFD at Konza. Species
whose geographic ranges extend into drier regions flower earlier on average than those
species whose geographic ranges do not extend into drier regions (r2 = 0.02, P = 0.002).
On average species whose geographic range extends into regions with MAP of 200 mm
begin to flower 22 d earlier than those species that extend only into regions with MAP as
low as 900 mm. Species that extended into wetter regions did not begin to flower earlier
or later than those that did not extend into wetter regions (P > 0.05), i.e. there was no
relationship between the MAP upper bound of species climate envelopes and first
flowering dates. Likewise, there was no relationship between FFD and how cold or warm
a region species extended (P > 0.05).
Isotopes
Leaf C isotope concentrations are reported as standardized ratio relative to Pee Dee
Belemnite (13CL) and leaf N isotopes are reported as standardized ratio relative to
atmospheric N2 (15NL). Within-run variability (estimated as the standard deviation of
working standards) was 0.1‰ and 0.2‰ for 13C and 15N, respectively. The betweenrun variability was estimated by comparing the measured value of a working standard to
its calibrated value and was < 0.08‰ and 0.22‰ for 13C and 15N, respectively.
Although multiple processes ultimately contribute to a leaf’s carbon isotope signature
(Salmon et al., 2011), we interpret the interspecific differences in 13CL we measured as
primarily representing differences in photosynthetic water use efficiency (Farquhar et al.,
1989; Smedley et al., 1991). Ambient atmospheric CO2 concentrations and 13C in the
region vary over the course of a season, but influence 13CL by < 0.2‰ (data not shown).
There were no differences in foliar 15N between early- and late-flowering species (P =
0.96). Species that flowered later had lower foliar 13C (r2 = 0.07, P < 0.001) than earlyflowering species (Fig. S3b). Based on these relationships, the last flowering species
would have a foliar 13C 1.7‰ lower after accounting for differences in average 13C for
C3 and C4 species than the first flowering species.
Fig. S1 Patterns of first flowering dates for Konza herbaceous flora partitioned by
flowering color and expressed as fraction of all recorded species flowering per day or
number of species flowering per day. In calculating the total number of species for
scaling the flowering density to total number of species, species that could be categorized
0.016
a
Red
0.012
Yellow
0.008
White
0.004
Purple
Wind
0
75
125
175
225
Day of Year
275
Flowering Rate (S d-1)
Fraction Flowering (d-1)
into two color categories only contributed 0.5 to the species number.
1.4
1.2
1
0.8
0.6
0.4
0.2
0
b
White
Wind
Yellow
Purple
Red
75
125
175
225
Day of Year
275
Fig. S2 Phylogenetic distribution of first flowering dates (FFD) for angiosperm species at
Konza. Height of black bar indicates relative FFD (short bars indicate early flowering,
tall bars indicate later flowering).
Fig. S3 Relationships between first flowering dates and foliar carbon and nitrogen
isotope ratios. Bivariate regressions between first flowering date and (a) foliar 15N (P >
0.94, n = 365), and (b) foliar 13C (C3 (closed circles): y = 28.2 – 0.0084x, r2 = 0.04, P <
0.001, n = 308; C4 (open circles): y = 11.3  0.0094x, r2 = 0.10, P = 0.02, n = 57).
20
0
a
-5
15
b
-10
Foliar d 13 C
Foliar d15 N
10
5
0
-15
-20
-25
-30
-5
-35
-10
-40
75
125
175
225
First Flowering Date
275
75
125
175
225
First Flowering Date
275