Table 1.
The strength of evidence for ecological models of mismatch in sexual armaments (scores on principal component axis 2 summarizing variation in female spines and male pregenitals), across 16 populations of G. incognitus sampled from British Columbia, Canada (see [21]). Akaike's information criterion (corrected for small sample sizes; AICc) is given along with model probability, indicating the probability of each model within the set of models given the data and evidence ratio, measuring how many times greater support is for the best supported model, compared with model i. The set of models includes a baseline (intercept-only) model for comparison and an ecological summary model (PC1 ecology, with PC1 scores for the three ecological variables with AICc values lower than the baseline model).
| model description | factors | AICci | Δi | model probability | evidence ratio | adjusted R2 |
|---|---|---|---|---|---|---|
| ecological summary model | PC1 ecology | 16.7 | 0.0 | 0.28 | 1.0 | 0.24 |
| snow depth | mean depth of snow [52] | 17.4 | 0.7 | 0.19 | 1.4 | 0.21 |
| winter severity | mean number of days annually with temperature approaching lower lethal threshold (−10°C) [52] | 18.6 | 1.9 | 0.10 | 2.6 | 0.14 |
| breeding season length | mean number of frost free days annually [53] | 18.6 | 2.0 | 0.10 | 2.7 | 0.14 |
| baseline model | intercept only | 19.1 | 2.4 | 0.08 | 3.4 | n.a. |
| elevation | 20.1 | 3.5 | 0.05 | 5.6 | 0.06 | |
| temperature | mean number of days with temperature > growth threshold for Gerris spp. (10°C) [54] | 20.4 | 3.7 | 0.04 | 6.3 | 0.04 |
| habitat stability | water body area | 21.3 | 4.6 | 0.03 | 10.0 | −0.01 |
| canopy cover | index from 0 to 5 (0, none; 1, 0–20%; 2, 21–40%; 3, 41–60%; 4, 61–80%; 5, 81–100%) | 21.5 | 4.9 | 0.02 | 11.3 | −0.03 |
| emergent vegetation | as for canopy cover | 21.9 | 5.2 | 0.02 | 13.6 | −0.05 |
| water aciditya | pH | 22.0 | 5.4 | 0.02 | 14.7 | −0.06 |
| precipitation | mean precipitation during the breeding season | 22.1 | 5.4 | 0.02 | 14.8 | −0.06 |
| predator presence | detection of corixid bugs, dytiscid or gyrinid beetles, water spiders, minnows, frogs and ducks, by net samples and visual and audial inspection | 22.1 | 5.5 | 0.02 | 15.3 | −0.07 |
| presence of other water striders | 22.1 | 5.5 | 0.02 | 15.5 | −0.07 |
aMeasured at 14 sites; imputed for two sites by the relationship between measured pH and geographical coordinates (see [15]).