Calling the Banners: exploring the complex biogeographical history of the Neotropical banner-wing damselflies (Odonata: Polythoridae)

Abstract

Background Sorting out the biogeographical history of species in the New World Tropics is challenging. We here examine the roles of evolution and biogeography in driving the distribution and diversification of the damselflies of the family Polythoridae. This family comprises seven genera with a total of 57 species, distributed across much of Central and South America. Results Through phylogenetic analysis, relaxed-clock molecular dating and biogeographical analysis we find these genera originated ~56 Ma and started diversifying ~45 Ma. As with other neotropical groups, the Polythoridae have a primary origin in the Northern Andes; at least one genus first appears 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 building. 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. Conclusion We conclude that this family of damselflies, despite its relatively young age, has developed into genera with diverse distributions and some surprisingly high diversity, despite relatively low habitat diversity. Polythore is a recent radiation where biogeographical events may not be the main drivers of diversification. Other factors like sexual and natural selection acting on color patterns could be involved in generate the extreme diversity in this genus.