For nearly a century, biologists have debated whether past climate change promoted speciation in temperate zone organisms. Models of climate-driven geographic speciation were developed for many groups of temperate organisms, and a particularly detailed and explicit speciation model was developed for North American birds. Over the last decade, this paradigm for North American birds has become the topic of debate, and so a comprehensive understanding of how temperate zone birds were impacted by past environmental change events remains elusive. This project will directly test the paradigm and will significantly extend understanding of the history of the fauna of pine and oak woodlands. The work will use state-of-the-art molecular techniques and analyses to examine the temporal and spatial patterns of diversification of North American birds in relation to past environmental change and will produce a multi-locus comparative phylogeography of pine and oak woodland birds.
The project provides significant mentoring and research opportunities for undergraduate and graduate students, including many students from underrepresented groups, and gives these students a unique opportunity to work in a multi-institutional and multidisciplinary research effort between a small rural university and two large urban research universities. The project also will support a workshop for high school teachers from the rural and reservation communities of western South Dakota and provide them the knowledge and resources to teach about climate change and its impact on biotic diversity in their classrooms.
Intellectual Merit Since the Modern Synthesis, evolutionary biologists have postulated that the climatic oscillations of the Quaternary promoted speciation in temperate zone organisms. Models of climate-driven allopatric speciation were developed for many groups of temperate organisms, but in no group was an explicit speciation model developed with more detail than in North American birds. During this period, the prevailing paradigm for speciation in North American birds led researchers to suggest that the advancing glaciers of the Quaternary fragmented widespread ancestral species, forming sister species pairs represented today by eastern and western forms. Over the last decade, this paradigm has become the topic of a focused debate. We tested the Pleistocene speciation paradigm using a multilocus comparative phylogeographic approach. Our major findings generally supported our initial hypotheses gleaned from the Pleistocene speciation paradigm and include: Lineage diversification across species is spatially concordant with the independent evolution of species/populations in the regional North American pine-oak forests. Lineage diversification is not temporally concordant across avian taxa suggesting the species diverged throughout the Pleistocene glacial cycles and not in response one particularly important biogeographic event. Resident species generally exihibit greater phylogeographic differentiation than long-distance migrant species. Genetic diversity is negatively correlated with latitude. Our comparative tests using ENMs suggest that niche conservatism was the primary force driving isolation and divergence in the focal taxa. Interestingly, our results also suggest that those species that have diverged ecologically are the ones whose ranges were most displaced during the last glacial maximum; however, this result still needs to tested more rigorously. The first proposed Pleistocene speciation models hypothesized that ecological selection was the evolutionary pressure driving divergence in allopatric refugia in most taxa. One of the most interesting findings of this work indicates that species that show evidence of ecological divergence show more pronounced molecular divergence than those that have speciated via genetic drift (niche conservatism) alone. This finding suggests that the genomic architecture of speciation is different for species that diverged in response to ecological selection, and is consistent with the genomic islands of speciation theory. Thus, species that diverged in response to ecological selection will be less likely to reticulate or merge due to secondary contact and hybridization. The phylogeographic work completed through this research suggests a comparative analysis of genomic differentiation in these taxa would provide great insight into the importance of ecology in the evolution of new species and potentially provide insight into the genomics of the evolution of reproductive isolation. Broader Impacts The broader impacts of the research are considerable. At Black Hills State University, twelve undergraduate and seven graduate students, including four American Indian students and eight women, participated in nearly all aspects of the research and many of these students are now pursuing terminal or advanced degrees in the Biological Sciences. Several REU students and all the Master’s students attended regional or national meetings to present the results of their research. This gave each of them the opportunity to interact with professional scientists and faculty other than their mentor. All REU fellows and graduate students helped the Center for the Advancement of Math and Science Education (CAMSE) teach a secondary school educator workshop at BHSU for three years of the project. The goal of the workshop was to teach high school biology teachers modern molecular techniques and teach these educators how these techniques are used in forensic and medical sciences. The project also contributed to the development of a middle and high school teacher workshop co-sponsored by CAMSE and PI Spellman at BHSU. The workshop focused on the science behind climate change and the biological impacts of climate change. During the workshop, teachers designed exercises from local examples of impacts that could be brought back to their classrooms to teach climate change science. The workshop was timely because it followed the passing of a South Dakota law requiring the balanced teaching of climate change in state schools (House Concurrent Resolution 1009). The written text of the resolution included several fallacies regarding climate science, yet the resolution passed easily. The development of the workshop led to demand from South Dakota teachers for more science workshops, which contributed to the procurment of funding from a state grant program to continue the teacher workshop program.
