An exploration of the complex biogeographical history of the Neotropical banner-wing damselflies (Odonata: Polythoridae)
Abstract Background: The New World Tropics has experienced a dynamic landscape across evolutionary history and harbors a high diversity of flora and fauna. While there are some studies addressing diversification in Neotropical vertebrates and plants, there is still a lack of knowledge in arthropods. Here we examine temporal and spatial diversification patterns in the damselfly family Polythoridae; which comprises seven genera with a total of 58 species distributed across much of Central and South America.Results: Our time-calibrated phylogeny for 48 species suggests that this family radiated during the early Eocene (~56 Ma), diversifying during the middle Eocene. As with other neotropical groups, the Most Recent Common Ancestor (MRCA) of most of the Polythoridae genera has a primary origin in the Northern Andes though the MRCA of at least one genus may have appeared in the Amazon Basin. Diversification rates have been uniform in all genera except one—Polythore—where a significant increase in the late Pliocene (~3 mya) correlates with mountain uplift. While our molecular clock suggests correlations with some major geographical events, our biogeographical modeling (with BioGeoBEARS and RASP) found little influence of the formation of the Pebas and Acre systems or Andean mountain building, possibly due to the short branch lengths in our time-dated phylogeny, or perhaps to climatic variability during the period in question. Conclusion: The biogeographical models implemented here were unable to explain the effect of South American major geological events (i.e Pebas and Acre systems, Andes uplift) on the diversification of this damselfly family; while diversification in the tree shows some correlation with mountain building events, it is possible that other abiotic and biotic changes during our study period have influenced diversification as well. The high diversification rate observed in Polythore could be explained by the late uplift of the Northern Andes. However, it is possible that other intrinsic factors like sexual and natural selection acting on color patterns could be involved in the diversification of this genus.