Abstract
With global climate change, rainfall is becoming more variable. Predicting the responses of species to changing rainfall levels is difficult because, for example in herbivorous species, these effects may be mediated indirectly through changes in host plant quality. Furthermore, species responses may result from a simultaneous interaction between rainfall levels and other environmental variables such as anthropogenic land use or habitat quality. In this eco-evolutionary study, we examined how male and female Pararge aegeria (L.) from woodland and agricultural landscape populations were affected by the development on drought-stressed host plants. Compared with individuals from woodland landscapes, when reared on drought-stressed plants agricultural individuals had longer development times, reduced survival rates and lower adult body masses. Across both landscape types, growth on drought-stressed plants resulted in males and females with low forewing aspect ratios and in females with lower wing loading and reduced fecundity. Development on drought-stressed plants also had a landscape-specific effect on reproductive output; agricultural females laid eggs that had a significantly lower hatching success. Overall, our results highlight several potential mechanisms by which low water availability, via changes in host plant quality, may differentially influence P. aegeria populations relative to landscape structure.
Highlights
Current climate change scenarios predict a global increase in temperature, spatial heterogeneity in precipitation, UV-B penetration and extreme events such as drought (Bale et al 2002)
Our study focused on how male and female P. aegeria from landscapes that differ in their degree of anthropogenic land use were affected by development on drought-stressed host plants
The data from the present study provide a much-needed first step in elucidating the mechanisms by which low water availability may differentially influence woodland and agricultural population dynamics: (i) for agricultural individuals, larval development on drought-stressed plants reduces survival rates to adulthood and extends the time to adult maturation, both of which directly influence adult recruitment rates at the population level, (ii) adults that develop on drought-stressed plants have lower forewing aspect ratios that may enhance their dispersal capacity and colonizing potential, and may facilitate the movement of individuals out of drought-stricken areas and (iii) females that develop on drought-stressed plants have a lower reproductive output, and agricultural females are further disadvantaged by their decreased resource allocation to egg provisioning that reduces egg-hatching success
Summary
Current climate change scenarios predict a global increase in temperature, spatial heterogeneity in precipitation, UV-B penetration and extreme events such as drought (Bale et al 2002). Predicting the ecological response of species to variation in rainfall levels is difficult as little research has been published documenting the direct effects of changing rainfall levels on species abundance and distribution (Bale et al.2002). In principle the patterns of response of species to changing rainfall levels can be detected globally, eco-evolutionary mechanisms underlying these responses operate locally at the level of individuals and populations and may result from a simultaneous interaction with other environmental variables such as anthropogenic land use or habitat quality (Stefanescu et al 2004; Schweiger et al 2006).
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