Biogeography and Ecological Diversification of a Mayfly Clade in New Guinea

Camille-Sophie Cozzarolo,Michel Sartori,Nils Arrigo,Nicolas Salamin,Morgan Gueuning,Camille Pitteloud,Nadir Alvarez,Michael Balke,Sven Buerki

doi:10.3389/fevo.2019.00233

Abstract

Understanding processes that have driven the extraordinary high level of biodiversity in the tropics is a long-standing question in biology. Here we try to assess whether the large lineage richness found in a New Guinean clade of mayflies (Ephemeroptera), namely the Thraulus group (Leptophlebiidae) could be associated with the recent orogenic processes, by applying a combination of phylogenetic, biogeographic and ecological shift analyses. New Guinean representatives of the Thraulus group appear monophyletic, with the possible exception of a weakly-supported early-diverging clade from the Sunda Islands. Dating analyses suggest an Eocene origin of the Thraulus group, predating by several million years current knowledge on the origin of other New Guinean aquatic organisms. Biogeographic inferences indicate that 27 of the 28 inferred dispersals (96.4%) occurred during the Eocene, Oligocene and Miocene, while only one dispersal (3.6%) took place during the Pliocene-Pleistocene. This result contrasts with the higher number of altitudinal shifts (15 of 22; 68.2%) inferred during the Pliocene-Pleistocene time slice. Our study illustrates the role played by – potentially ecological - diversification along the elevation gradient in a time period concomitant with the establishment of high-altitude ecological niches, i.e., during orogenesis of the central New Guinean mountain range. This process might have taken over the previous main mode of diversification at work, characterized by dispersal and vicariance, by driving lineage divergence of New Guinean Leptophlebiidae across a wide array of habitats along the elevation gradient. Additional studies on organisms spanning the same elevation range as Thraulus mayflies in the tropics are needed to evaluate the potential role of the ecological opportunity or taxon cycles hypotheses in partly explaining the latitudinal diversity gradient.

Highlights

Tropical biomes are the most diverse among all ecosystems (Myers et al, 2000; Dirzo and Raven, 2003)
We made a first attempt to infer the biogeography of leptophlebiid mayflies from New Guinea by studying the patterns of dispersal and altitudinal shifts using a molecular clock-based dated phylogeny
We suggest that the colonization of New Guinea by the Thraulus clade might have occurred as early as the Eocene

Summary

Introduction

Tropical biomes are the most diverse among all ecosystems (Myers et al, 2000; Dirzo and Raven, 2003). The formation of mountain ranges is a potentially important driver of speciation as it produces the ecological heterogeneity to study diversification processes (Luebert and Muller, 2015), creating, along new dispersal routes and vicariance events, a vast variety of new ecological opportunities to adapt to Gueuning et al (2017). This is especially true in the tropics where the number of stratified ecosystems found along the elevation gradient is larger than anywhere else (Körner, 2003). One such tropical and mountainous region is the island of New Guinea (NG), which is long known to be exceedingly diverse in terms of species numbers and other aspects of biological diversity (Gressitt, 1982)

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Conclusion