ORIGINAL ARTICLE: Coalescent analyses support multiple mainland‐to‐island dispersals in the evolution of Malagasy Triaenops bats (Chiroptera: Hipposideridae)

Abstract

Biogeographical questions are increasingly amenable to molecular data and associated methods for demographic inference. Traditionally, genetic analyses have relied heavily on phylogenetic approaches. Dated phylogenies can provide working hypotheses for organismal relationships, including the ability to place them within a spatial and temporal framework. This method also has relevance to biogeography; for instance, comparisons of species cladograms and geographical distributions often allow competing dispersal and vicariance hypotheses to be distinguished ABSTRACT Aim We investigate the directionality of mainland-to-island dispersals, focusing on a case study of an African-Malagasy bat genus, Triaenops (Hipposideridae). Taxa include T. persicus from east Africa and three Triaenops species from Madagascar (T. auritus, T. furculus, and T. rufus). The evolution of this bat family considerably post-dated the tectonic division of Madagascar from Africa, excluding vicariance as a viable hypothesis. Therefore, we consider three biogeographical scenarios to explain these species' current ranges: (A) a single dispersal from Africa to Madagascar with subsequent speciation of the Malagasy species; (B) multiple, unidirectional dispersals from Africa to Madagascar resulting in multiple, independent Malagasy lineages; or (C) early dispersal of a proto-species from Africa to Madagascar, with later back-dispersal of a descendant Malagasy taxon to Africa.Location East Africa, Madagascar, and the Mozambique Channel.Methods We compare the utility of phylogenetic and coalescent methodologies to address the question of directionality in a mainland-to-island dispersal event for recently diverged taxa. We also emphasize the application of biologically explicit demographic systems, such as the non-equilibrium isolation-withmigration model. Here, these methods are applied to a four-species haploid genetic data set, with simulation analyses being applied to validate this approach.Results Coalescent simulations favour scenario B: multiple, unidirectional dispersals from Africa to Madagascar resulting in multiple, independent Malagasy bat lineages. From coalescent dating, we estimate that the genus Triaenops was still a single taxon approximately 2.25 Ma. The most recent Africa to Madagascar dispersal occurred much more recently (c. 660 ka), and led to the formation of the extant Malagasy species, T. rufus.Main conclusions Haploid genetic data from four species of Triaenops are statistically most consistent with multiple, unidirectional dispersals from mainland Africa to Madagascar during the late Pleistocene.

Cross-species chromosome painting in bats from Madagascar: the contribution of Myzopodidae to revealing ancestral syntenies in Chiroptera

“…Following the phylogenetic hypothesis of Teeling et al (2005) and Miller-Butterworth et al (2007), Myzopoda originated from a Neotropical noctilionid ancestor that dispersed to Madagascar from South America during the early Eocene. This scenario is in stark contrast to recent phylogeographic studies on Malagasy bats which demonstrate colonization from Africa across the Mozambique Channel (Russell et al 2008;Ratrimomanarivo et al 2007Ratrimomanarivo et al , 2008 or from Asia O'Brien et al 2009). …”

Biogeography and diversification of hermit spiders on Indian Ocean islands (Nephilidae: Nephilengys)

“…Fuller et al (2005) also precluded vicariance in the allodapine bee genus Braunsapis on Madagascar, for which they inferred aerial or over water dispersal from Africa. Russell et al (2008) reconstructed the evolutionary history of Triaenops bats, which diversified in Madagascar with several independent colonizations from Africa. Further cases of colonization of Madagascar from Africa have been inferred in frogs (Vences et al, 2004), freshwater crabs (Cumberlidge, 2008), and other spiders (Agnarsson and Kuntner, 2005;.…”

“…However, existing calibrated phylogenies for vertebrates, invertebrates, and plants are only rarely compatible with the vicariant model (Yoder and Nowak, 2006). Thus, the Cenozoic model seems to apply to more lineages of Madagascar fauna and flora (Yoder and Nowak, 2006), in particular to vertebrates (Vences et al, 2001;Raxworthy et al, 2002;Hume, 2007) and especially mammals (Tattersall, 2006;Masters et al, 2006Masters et al, , 2007Russell et al, 2008).…”

The Generation of a Biodiversity Hotspot: Biogeography and Phylogeography of the Western Indian Ocean Islands

“…In fact, the genus Onychoprion though extremely widespread and abundant, contains only four species in total. Triaenops fruit bats, also good dispersers, have repeatedly colonized Madagascar and adjacent islands in the relatively recent past, but remain species poor (Russell, Goodman, and Cox 2008), presumably due to continuous gene flow across their Malagasy range. Some of the strongest flying insects such as dragonflies have colonized all the islands but only diversified very moderately and many species are widespread and known to disperse long distances overwater (Dijkstra 2007).…”

“…For example, oscine passerines arrived via overwater dispersal from Australia to Asia, moving over the Indian Ocean and eventually to Africa, where they radiated (Jonsson and Fjeldsa 2006), parrots probably colonized the Mascarenes from India (Hume 2007), scops owls colonized Asia from the Indian Ocean (Fuchs et al 2008), and magpie robins colonized Madagascar from Asia (Sheldon et al 2009). Among flying mammals, Pteropus bats repeatedly colonized the islands from Asia (O'Brien et al 2009), and Triaenops bats colonized Madagascar repeatedly from Africa resulting in several Malagasy radiations (Russell, Goodman, and Cox 2008). For Rousettus bats current phylogenies are inconclusive, but they may have arrived from Asia, or the Middle East (Goodman, Chan, et al 2010).…”