Repeated Climate-linked host shifts have promoted diversification in a temperate clade of leaf-mining flies

Authors: WINKLER, ISSAC - North Carolina State University; MITTER, CHARLES - University Of Maryland; Scheffer, Sonja

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2009
Publication Date: 9/24/2009
Citation: Winkler, I.S., Mitter, C., Scheffer, S.J. 2009. Repeated Climate-linked host shifts have promoted diversification in a temperate clade of leaf-mining flies. Proceedings of the National Academy of Sciences. 106:18103-18108.

Interpretive Summary: Plant-feeding insects are extraordinarily diverse and cause many millions of dollars in losses to U. S. and global agriculture annually. Understanding the evolutionary history of plant-feeding insects helps shed light on the processes that give rise to this diversity and account for some of the patterns we observe today. In this study we used fossil evidence in combination with DNA sequence data to investigate the timing of diversification events in leaf-mining flies with respect to host-plant usage and past climactic history. We found that past host shifts to new plant groups has resulted in increased diversity while major climactic events in the Oligocene and Miocene have not. However, climate-induced modification of the environment probably did increase the availability of some plant groups to be fed upon by these leaf-mining flies. This research will be of interest to evolutionary biologists, entomologists, and paleontologists.

Technical Abstract: A central but little-tested prediction of "escape and radiation" coevolution is that colonization of novel, chemically defended host plant clades accelerates insect herbivore diversification. That theory, in turn, exemplifies one side of a broader debate about the relative influence on clade dynamics of biotic versus physical-environmental forces. Here we use a fossil-calibrated molecular chronogram to compare the effects of a major biotic factor (repeated shift to a chemically divergent host plant clade) and a major abiotic factor (global climate change) on the macroevolutionary dynamics of a temperate, Cenozoic radiation of phytophagous insects, the leaf-mining fly genus Phytomyza (Diptera: Agromyzidae). We find one of the first statistically supported examples of consistently elevated diversification accompanying shift to new plant clades. In contrast, we detect no significant direct effect on diversification of major global climate events in the Oligocene and Miocene. The broader paleoclimatic context strongly suggests, however, that this abiotic force has had a strong indirect influence through its effect on the biotic environment: repeated rapid Miocene radiation of these flies on temperate herbaceous asterids was almost surely made possible by the dramatic, climate-driven expansion of seasonal, open habitats.