 |
in Meegaskumbura, Senevirathne, Manamendra-Arachchi, et al., 2019.
|
Highlights
• Pseudophilautus diversification, begins during Oligocene (31 MYA)
• A stately pace of lineage accumulation despite orogeny and climate change.
• Assemblages in most regions comprise of species arising from diverse clades.
• MRCA of a back-migrating clade to India (8.8 MYA), reconstructs as a lowland form.
• Island’s mountains serve as species pumps and refuges for Pseudophilautus evolution.
Abstract
Pseudophilautus comprises an endemic diversification predominantly associated with the wet tropical regions of Sri Lanka that provides an opportunity to examine the effects of geography and historical climate change on diversification. Using a time-calibrated multi-gene phylogeny, we analyze the tempo of diversification in the context of past climate and geography to identify historical drivers of current patterns of diversity and distribution. Molecular dating suggests that the diversification was seeded by migration across a land-bridge connection from India during a period of climatic cooling and drying, the Oi-1 glacial maximum around the Eocene-Oligocene boundary. Lineage-through-time plots suggest a gradual and constant rate of diversification, beginning in the Oligocene and extending through the late Miocene and early Pliocene with a slight burst in the Pleistocene. There is no indication of an early-burst phase of diversification characteristic of many adaptive radiations, nor were there bursts of diversification associated with favorable climate shifts such as the intensification of monsoons. However, a late Miocene (8.8 MYA) back-migration to India occurred following the establishment of the monsoon. The back migration, however, did not trigger a diversification in India similar to that manifest in Sri Lanka, likely due to occupation of available habitat, and consequent lack of ecological opportunity, by the earlier radiation of a sister lineage of frogs (Raorchestes) with similar ecology. Phylogenetic area reconstructions show a pattern of sister species distributed across adjacent mountain ranges or from different parts of large montane regions, highlighting the importance of isolation and allopatric speciation. Hence, local species communities are composed of species from disparate clades that, in most cases, have been assembled through migration rather than in situ speciation. Lowland lineages are derived from montane lineages. Thus, the hills of Sri Lanka acted as species pumps as well as refuges throughout the 31 million years of evolution, highlighting the importance of tropical montane regions for both the generation and maintenance of biodiversity.
Keywords: Ancestral-area reconstruction, Biogeography, Ecological opportunity, Diversification, Molecular dating, Speciation
Madhava Meegaskumbura, Gayani Senevirathne, Kelum Manamendra-Arachchi, Rohan Pethiyagoda, James Hanken and Christopher J. Schneider. 2019. Diversification of Shrub Frogs (Rhacophoridae, Pseudophilautus) in Sri Lanka – Timing and Geographic context. Molecular Phylogenetics and Evolution. In Press. DOI: 10.1016/j.ympev.2018.11.004
