Stop and Go – Waves of Tarsier Dispersal Mirror the Genesis of Sulawesi Island

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.

Synchronous diversification of Sulawesi’s iconic artiodactyls driven by recent geological events

“…Populations of Babirusa and SWP in these zones of endemism were also strongly morphologically differentiated ( Figure 2). Altogether, these data and analyses indicate that, despite some differences, the zones of endemism identified in tarsiers, macaques, toads and lizards [18,[40][41][42][43][44][45]47] are largely consistent with the population structure and morphological differentiation in the three species studied here. This is particularly striking for the north arm of Sulawesi (NW, NC, and NE in Figure 4), where we identify two highly differentiated populations (reflected in both mtDNA and nuclear data sets) in all three taxa.…”

“…Previous studies have identified endemic zones that are common to macaques, toads [18,40], tarsiers [41][42][43][44] and lizards [45]. We tested whether the same area of endemism are linked to the population structure in our three species by generating a phylogenetic tree for each species using mtDNA and defined 5-6 haplogroups per species based on well-supported clades (Figure 4a-c; Figure S4-6).…”

Paleoenvironmental and Sea‐Level Change

“…Sea level changes in the Pliocene that periodically exposed and obliterated land bridges shaped dispersal and diversification of Sulawesi tarsiers (Driller et al 2015), and later, responding to the immense sea level fluctuations caused by Pleistocene glacial cycles, also macaques. In fact, changes in sea level and associated shifts in the size and connections of landmasses are implicated in the dispersal and subsequent evolution of several groups of primates.…”

Pliocene Primates

“…Molecular analysis suggests that the main tarsier lineages diversified in the Miocene, but DNA data alongside acoustic evidence have revealed the complexities of their subsequent evolution in the Pliocene. For the Sulawesi clade, this included dispersal across the region, with range expansions and consequent late Pliocene diversification being linked to periodic exposure, due to sea level change, of shelves and land-bridges, as well as lineage divergence promoted by Pliocene tectonic faulting and the associated emergence of lakes (Driller et al 2015).…”