Diversification and the adaptive radiation of the vangas of Madagascar

Abstract

The vangas of Madagascar exhibit extreme diversity in morphology and ecology. Recent studies have shown that several other Malagasy species also are part of this endemic radiation, even as the monophyly of the clade remains in question. Using DNA sequences from 13 genes and representatives of all 15 vanga genera, we find strong support for the monophyly of the Malagasy vangids and their inclusion in a family along with six aberrant genera of shrike-like corvoids distributed in Asia and Africa. Biogeographic reconstructions of these lineages include both Asia and Africa as possible dispersal routes to Madagascar. To study patterns of speciation through time, we introduce a method that can accommodate phylogenetically non-random patterns of incomplete taxon sampling in diversification studies. We demonstrate that speciation rates in vangas decreased dramatically through time following the colonization of Madagascar. Foraging strategies of these birds show remarkable congruence with phylogenetic relationships, indicating that adaptations to feeding specializations played a role in the diversification of these birds. Vangas fit the model of an 'adaptive radiation' in that they show an explosive burst of speciation soon after colonization, increased diversification into novel niches and extraordinary ecomorphological diversity.

Temporal niche promotes biodiversity during adaptive radiation

“…Given the prevalence of environmental fluctuations that offer temporal niche opportunities at various timescales in nature 31,32 , this result has important implications for understanding diversification patterns in many natural systems. For example, whereas overshooting dynamics are frequently encountered when studying adaptive radiation in nature 25,26 , many lineages have diversified without showing an apparent decline in diversity 32,33 . Although alternative hypotheses exist 22,31 , our results suggest that TND may potentially explain the maintenance of the accumulated biodiversity over evolutionary time.…”

Are Historical Biogeographical Events Able to Promote Biological Diversification?

“…Ecological opportunity can facilitate changes in diversification dynamics after a dispersal event [33,73]. This is partially supported by evidence showing that dispersal events did not occur randomly across geography, and for some groups colonizing islands it was a notable increase in speciation rates after that events [4,16,21,56,57,61]. For instance, dispersal of the palm tribe Trachycarpeae to different island systems promoted parallel diversifications connected with climatic and geological changes [4].…”

“…For bird clades distributed in the Indo-Pacific archipelago, species diversification rates increased on islands where few dispersal events were inferred, whereas clades occupying islands with high immigration rates exhibited constancy in diversification rates [16]. In the case of Malagasy vangids, early dispersal from Africa to Madagascar promoted an increase in species diversification rates by ecological opportunity followed by a decline through time suggesting an ecological limit for this adaptive radiation [57].…”

Additional Reports on the Breeding Ecology of Chabert’s Vanga <i>Leptopterus chabert</i> and Red-tailed Vanga <i>Calicalicus madagascariensis</i>

“…The vangids are best known for their adaptive radiation, which is comparable to that of the Galapagos finches or of the Hawaiian honeycreepers (Grant & Grant 2008, Reddy et al 2012, Jønsson et al 2012. Although the evolutionary history of the vangids has been well studied (Yamagishi & Nakamura 2009), basic information on the breeding biology of each species is still lacking.…”

“…The family Vangidae is endemic to Madagascar and consists of 21 species (Reddy et al 2012, Jønsson et al 2012. The vangids are best known for their adaptive radiation, which is comparable to that of the Galapagos finches or of the Hawaiian honeycreepers (Grant & Grant 2008, Reddy et al 2012, Jønsson et al 2012.…”