An unresolved question in evolutionary biology is the extent to which past adaptations influence adaptations of species to a new environment. For example, does past adaptation to an ancestral microhabitat (e.g., trees) constrain adaptation to a novel microhabitat type (e.g., water)? Or does adaptation to a new microhabitat completely erase any traces of previous evolutionary history? This question will be addressed in frogs of the world through measuring performance (e.g., jumping, swimming), body form (e.g., size, shape), and habitat use, and then estimating change during the evolutionary history of frogs via an understanding of evolutionary relationships among species. Data have been collected within China and Colombia, and this grant will extend the sampling to Australia, as well as allowing further work at museums in the U.S.
This research will lead to an understanding of the influence of historical influences (e.g., previous habitat use and adaptations to it) on subsequent evolutionary change, something that has not previously been well understood. Furthermore, this project will result in the training of undergraduate students in research in evolutionary biology, as well as develop international collaboration with scientists from Australia and develop cross-cultural understanding through outreach presentations, both in the U.S. and Australia.
In this study we analyzed ecological, morphology, and functional diversity in frogs around the world. Our primary goal was to understand the factors that generated this diversity across local communities. For example, if environments and associated selection pressures are sufficiently similar around the world, will very different taxa converge to use the environments in similar ways, or will historical influences (e.g., time, ancestral starting point) prevent species in different regions from adapting similarly to the same environments? Does a relative lack of evolution in a group, coupled with biogeographic dispersal, also explain why some species across communities have similar ecology, morphology, and performance? To answer these questions we conducted work at many museums (seven within the United States) and at three field sites around the world, in Australia, China, and Colombia. We collected and analyzed data on morphology (body size and form), performance in jumping and swimming, microhabitat use (e.g., whether frogs live primarily in the trees, water, or ground), and evolutionary relationships among species. These large geographic and temporal scales allowed us to address the above questions about evolutionary adaptation. When we compared species that were very similar in ecology, morphology, and performance across different locations (e.g., China and Colombia), we found that species’ similarity was due to two very different processes. In some cases, this similarity was due to convergent evolution of species across locations – in other words, evolutionarily unrelated groups responded to similar natural selection in the same microhabitat. The convergent evolution was mostly "complete" – traces of adaptation to the ancestral microhabitat of species were erased through convergent evolution. However, in other cases, similarity of species across continents was the result of dispersal around the world with very little evolution. Thus, in frogs, some groups may show remarkable convergent evolution, while others change very little but disperse around the world. Our results raise the interesting question of why some clades fit in the former category (adaptive diversification within a location) while others fit the latter (evolutionary conservatism with dispersal). In terms of scientific significance, this is a surprising and important result, as it demonstrates that even on global scales, communities may not be independent with respect to how the relationship between ecology, morphology, and performance evolved. In other words, natural selection to maintain an already successful type may be just as important as natural selection to adapt to a new environment. In additional to the academic significance of this project, it had two main broader impacts. First, we worked with many undergraduate and young graduate students while doing the international fieldwork of our project (3 in China, 20 in Colombia, 1 in Australia). We also worked with one minority female undergraduate student at Stony Brook University to analyze our data from China. This undergraduate mentee presented her research at the annual Stony Brook undergraduate research poster fair. Second, although not a direct consequence of the research results per se, the international travel we did and collaborations we made as part of this research have had broader impacts. In China, one of us (DSM) gave invited lectures at two universities and met with students to discuss our research and ideas for theirs, including plans for studies in the United States. In Colombia, we gave invited lectures open to the public and a guest lecture in a graduate course. One of us (DSM) also developed a full, semester-long graduate course in comparative biology at the Colombian host institution. This continued research collaboration and education of the greater scientific community in many different parts of the world should lead to further cross-cultural and international communication and cooperation with American scientists.
