Abstract
The Indonesian island of Sulawesi harbors a highly endemic and diverse fauna sparking fascination since long before Wallace’s contemplation of biogeographical patterns in the region. Allopatric diversification driven by geological or climatic processes has been identified as the main mechanism shaping present faunal distribution on the island. There is both consensus and conflict among range patterns of terrestrial species pointing to the different effects of vicariant events on once co-distributed taxa. Tarsiers, small nocturnal primates with possible evidence of an Eocene fossil record on the Asian mainland, are at present exclusively found in insular Southeast Asia. Sulawesi is hotspot of tarsier diversity, whereby island colonization and subsequent radiation of this old endemic primate lineage remained largely enigmatic. To resolve the phylogeographic history of Sulawesi tarsiers we analyzed an island-wide sample for a set of five approved autosomal phylogenetic markers (ABCA1, ADORA3, AXIN1, RAG1, and TTR) and the paternally inherited SRY gene. We constructed ML and Bayesian phylogenetic trees and estimated divergence times between tarsier populations. We found that their arrival at the Proto-Sulawesi archipelago coincided with initial Miocene tectonic uplift and hypothesize that tarsiers dispersed over the region in distinct waves. Intra-island diversification was spurred by land emergence and a rapid succession of glacial cycles during the Plio-Pleistocene. Some tarsier range boundaries concur with spatial limits in other taxa backing the notion of centers of faunal endemism on Sulawesi. This congruence, however, has partially been superimposed by taxon-specific dispersal patterns.
Highlights
Situated at the triple junction of the Australian, Eurasian, and Pacific plates the Indonesian island of Sulawesi is part of the tectonically most active region in the world
Crown Sulawesi tarsiers further diversified into two major lineages not before Plio-Pleistocene
We further linked our divergence time estimates to proposed land and sea distributions at the paleo-Sulawesi archipelago [40,41,42,43] and to present-day topographical maps indicating interglacial shallow seas and presumably flooded low lying land areas at times of historical sea level increase
Summary
Situated at the triple junction of the Australian, Eurasian, and Pacific plates the Indonesian island of Sulawesi is part of the tectonically most active region in the world. We analyzed the sex-determining region of the Y-chromosome (SRY) and a set of five autosomal and taxonomic widely applicable phylogenetic markers (ABCA1, ADORA3, AXIN1, RAG1, and TTR) [18] in a tarsier sampling with a broad geographic coverage reflecting both geological and vocal features (Fig 1B– 1D and Table 1). On this basis we inferred phylogenetic relationships of distinct tarsier populations and, tested the plausibility of tectonic and climatic forces driving speciation on Sulawesi. In addition we asked whether and to what extent range fragmentation or lineage-specific life history traits shaped current phylogeographic patterns of these group-living nocturnal primates comparing the tarsiers spatial distribution to that of other island endemics
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