Ecotone shifts in southern Madagascar: first barcoding data and six new species of the endemic millipede genus Riotintobolus (Spirobolida, Pachybolidae)

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Abstract

Six new species of the Spirobolida millipede genus Riotintobolus Wesener, 2009, are described from the spiny forest in southern Madagascar utilising genetic barcoding, drawings and scanning electron microscopy: Riotintobolus tsimelahy sp. nov., R. mangatsiaka sp. nov., R. lavanono sp. nov., R. bovinus sp. nov., R. antafoky sp. nov. and R. makayi sp. nov. One other Riotintobolus population from the spiny forest might represent an additional species based on genetic data, but it cannot be described as no male specimens were collected. At present, the genus Riotintobolus Wesener, 2009 has eight species from the spiny forest and two species from the littoral rainforest. A determination key to all ten species of the genus is provided. Molecular data reveal that the two critically endangered species from the humid littoral rainforest are not closely related to one another, but have their closest relative in the dry spiny forest ecosystem. Riotintobolus mandenensis Wesener, 2009, only known from the southern littoral rainforest of Mandena is related to R. tsimelahy sp. nov. from the nearby spiny forest at Tsimelahy with a p-distance of 11%, while R. minutus Wesener, 2009 from the littoral forest of Sainte Luce is more distant to all other Riotintobolus species, but more closely related to R. bovinus sp. nov. from the southwestern forest of the Makay.

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Gondwana to Asia: Plate tectonics, paleogeography and the biological connectivity of the Indian sub-continent from the Middle Jurassic through latest Eocene (166–35 Ma)

Jason Ali, Jonathan C. Aitchison (2008)

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Madagascar as a model region of species diversification.

Miguel Vences, Katharina C. Wollenberg, David R Vieites … (2009)

Tropical biotas provide excellent settings in which to explore mechanisms of evolutionary diversification, yet these processes remain poorly understood. Pioneering work on biodiversity patterns and diversification processes in other tropical regions has recently been complemented by studies in Madagascar. Here we review diversity models and diversification mechanisms proposed for the fauna of this island and the perspectives for testing them. Madagascar has a diverse biota that has evolved in isolation, and is characterised by regionally pronounced and locally steep environmental gradients, common patterns of microendemism across taxa and numerous evolutionary radiations. These characteristics establish Madagascar as a promising system for the study of pattern and process in species diversification.

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The evolution of local endemism in madagascar: watershed versus climatic gradient hypotheses evaluated by null biogeographic models.

Richard Pearson, Christopher J. Raxworthy (2009)

Substantial insular speciation has resulted in exceptionally high levels of endemism in Madagascar, creating locally restricted species' ranges that remain poorly understood. The contributions of alternative processes that could influence patterns of local endemism-including speciation by geographic isolation or adaptation to environmental gradients-are widely debated, both for Madagascar and elsewhere. A recently proposed hypothesis (the "watershed hypothesis") suggests that allopatric speciation driven by isolation in watersheds during Quaternary climate shifts provides a general explanation for patterns of local endemism across taxa in Madagascar. Here we tested coincidence between species' distributions and areas of endemism predicted by two contrasting biogeographic hypotheses: (1) the watershed hypothesis, and (2) an alternative hypothesis driven by climatic gradients (the "current climate hypothesis"). Statistical significance of coincidence was assessed by comparing against a null model. Surprisingly, we found that extant distributions of lemurs, geckos, and chameleons reveal species patterns that are significantly coincident with the watershed and current climate hypotheses. These results strongly support local endemism developing from multiple processes, even among closely related species. Our findings thus indicate that pluralistic approaches will offer the best option both for understanding processes that generate local endemism, and for incorporating endemism within conservation priority setting.