Variation in functional traits form the foundation for studying natural selection. In addition, traits regulate species distributions via their effects on dispersal and demography, arguably shaping broad gradients in species richness. Traits such as body size and color influence species dispersal and distributions and determine how species respond to environmental change. With increasing elevation, for example, body size is expected to decrease and melanism is expected to increase resulting in trait clines and likely reduced species richness at high elevations. Furthermore, global warming is expected to shift species ranges upward, creating more fragmented populations. Thus, predicting how species respond to environmental change provides an important analog for predicting how species respond to climate change.
Lepidoptera are particularly diverse in morphology, especially in color and size. As ectotherms, they are sensitive to temperature and are model organisms for understanding the causes and consequences of trait variation in structuring communities both across environmental gradients in geographical space and in response to environmental changes in time. In this study we examined patterns in wing size and coloration in lepidopteran communities across Puerto Rico to 1) test whether wing size and coloration predict distributions or changes in distributions under future climate scenarios and 2) examine large-scale variation in species richness under current and future scenarios of climate change. Towards this end we used thousands of museum specimens to generate species distribution models for present and future climate scenarios.
Results/Conclusions
Based on weighted model averages, the highest species richness occurred at low elevations. Further, high elevation regions were predicted to experience the greatest declines in species richness under all projected climate change scenarios. Spatial variation of traits was evident. Wing size declined non-linearly with elevation. The geographic distribution of wing coloration was more nuanced across the island’s complex topography. However, in general, species at low elevations tended to be brighter, more intense and saturated in color whereas high elevation species tended to be darker and duller in coloration. Models predicted an upward expansion of low elevation species and concomitant changes in trait distributions. We use these results to identify hotspots for conservation and species most vulnerable to climate change.