Oecologia
Roles of spatial partitioning, competition, and predation in the North American invasion of an
exotic mosquito
T. Z. Freed and P. T. Leisnham*
Department of Environmental Science and Technology, University of Maryland, College Park,
MD 20742-2315, USA.
*corresponding author, leisnham@umd.edu
ESM 1: Calculation of finite rate of population increase λ'
Calculation








ln 1 / N 0  Axf wx 
x




 '  exp

 xAxf wx 


 x

D  
Axf wx  


x

 
Where N0 is the initial number of females (assumed to be 50%), x is the median days to eclosion,
Ax is the mean number of females eclosing on day x, and wx is the mean wing length on day x.
The function f(wx) is the species-specific relationship between fecundity and female wing length.
For A. albopictus, f(wx)=0.5 * (78.02 * wx – 121.24) (Lounibos 2002). For A. japonicus, f(wx)=
(53.078* wx) – 113.91 (Armistead et al. 2008). D is the time from eclosion to reproduction,
which is estimated to be 14 days for A. albopictus (Lounibos 2002) and 12 days for A. japonicus
(Armistead et al. 2008).
References
Armistead JS, Arias JR, Nishimura N, Lounibos LP (2008) Interspecific larval competition
between Aedes albopictus and Aedes japonicus (Diptera : Culicidae) in northern Virginia.
J. Med. Entomol. 45:629-637
Lounibos LP (2002) Invasions by insect vectors of human disease. Annu. Rev. Entomol. 47:233266
ESM 2: Calculation of the aggregation indices.
Calculation of the index of intraspecific aggregation, J; the index of interspecific calculation, C;
and the index of relative aggregation T:
𝐽1 =
V1
1
2−m
m1
1
where m1 is the mean and V1 is the variance of species 1 per patch. At J = 0, species 1 is
randomly distributed among patches, and at J > 0 species 1 is aggregated.
𝐶12 =
Cov12
(m1 ∗ m2 )
where Cov12 is the covariance between species 1 and species 2. At C = 0 the two species are
independently distributed, at C > 0 the two species are positively associated, and at C < 0 the two
species are negatively associated.
𝑇12 =
(𝐶12 + 1)
(𝐽2 + 1)
where the inferior competitor is aggregated independently of the superior competitor at T < 1. T12
is considered to be a necessary and sufficient condition for coexistence between competitors
(Sevenster 1996).
References
Sevenster JG (1996) Aggregation and coexistence .1. Theory and analysis. Journal of Animal
Ecology 65:297-307
ESM 3: Site and site type trends of physiochemical characteristics.
Figure 1 Bivariate plots of (A) detritus (g dry mass) and volume (mL), and (B) total nitrogen
(mg L-1) and total phosphorus (mg L-1) among tree hole (filled) and tire (open) sites. Least
squares means are ± SE.