The “sexy shrimp”
Coral reefs in all tropical oceans.
Specimens of
We found evidence for at least five cryptic lineages (9%–22%
The biota of Sulawesi is noted for its high degree of endemism and for its substantial levels of in situ biological diversification. While the island’s long period of isolation and dynamic tectonic history have been implicated as drivers of the regional diversification, this has rarely been tested in the context of an explicit geological framework. Here, we provide a tectonically informed biogeographical framework that we use to explore the diversification history of Sulawesi flying lizards (the Draco lineatus Group), a radiation that is endemic to Sulawesi and its surrounding islands. We employ a framework for inferring cryptic speciation that involves phylogeographic and genetic clustering analyses as a means of identifying potential species followed by population demographic assessment of divergence-timing and rates of bi-directional migration as means of confirming lineage independence (and thus species status). Using this approach, phylogenetic and population genetic analyses of mitochondrial sequence data obtained for 613 samples, a 50-SNP data set for 370 samples, and a 1249-locus exon-capture data set for 106 samples indicate that the current taxonomy substantially understates the true number of Sulawesi Draco species, that both cryptic and arrested speciations have taken place, and that ancient hybridization confounds phylogenetic analyses that do not explicitly account for reticulation. The Draco lineatus Group appears to comprise 15 species—9 on Sulawesi proper and 6 on peripheral islands. The common ancestor of this group colonized Sulawesi ~11 Ma when proto-Sulawesi was likely composed of two ancestral islands, and began to radiate ~6 Ma as new islands formed and were colonized via overwater dispersal. The enlargement and amalgamation of many of these proto-islands into modern Sulawesi, especially during the past 3 Ma, set in motion dynamic species interactions as once-isolated lineages came into secondary contact, some of which resulted in lineage merger, and others surviving to the present. [Genomics; Indonesia; introgression; mitochondria; phylogenetics; phylogeography; population genetics; reptiles.]
more » « lessThe “sexy shrimp”
Coral reefs in all tropical oceans.
Specimens of
We found evidence for at least five cryptic lineages (9%–22%
To determine the historical dynamics of colonization and whether the relative timing of colonization predicts diversification rate in the species‐rich, murine rodent communities of Indo‐Australia.
Indo‐Australian Archipelago including the Sunda shelf of continental Asia, Sahul shelf of continental Australia, the Philippines and Wallacea of Indonesia.
Order Rodentia, Family Muridae.
We used a fossil‐calibrated molecular phylogeny and Bayesian biogeographical modelling to infer the frequency and temporal sequence of biogeographical transitions among Sunda, Sahul, the Philippines and Wallacea. We estimated diversification rates for each colonizing lineage using a method‐of‐moments estimator of net diversification and Bayesian mixture model estimates of diversification rate shifts.
We identified 17 biogeographical transitions, including nine originating from Sunda, seven originating from Sulawesi and broader Wallacea and one originating from Sahul. Wallacea was colonized eight times, the Phillipines five times, Sunda twice and Sahul twice. Net diversification rates ranged from 0.2 to 2.12 species/lineage/My with higher rates in secondary and later colonizers than primary colonizers. The highest rates were in the genus
Our inferences from murines demonstrate once again the substantial role of islands as sources of species diversity in terrestrial vertebrates of the IAA with most speciation events occurring on islands. Sulawesi and broader Wallacea have been a major source of colonists for both island and continental systems. Crossings of Wallace's Line were more common than subsequent transitions across Lydekker's Line to the east. While speciation following colonization of oceanic archipelagos and large islands is consistent with adaptive radiation theory and ideas regarding ecological opportunity, we did not observe a strong signal of incumbency effects. Rather, subsequent colonists of landmasses radiated unhindered by previous radiations.
Madagascar is renowned for its exceptional species diversity and endemism. The island's mountainous regions are thought to have played a role in lineage and species diversification, but this has yet to be explored across taxonomic groups and a temporal context has not yet been identified. We tested whether montane regions have promoted population divergence in Madagascar's vertebrate fauna and, if so, whether these divergence events were contemporaneous.
Moist evergreen forests of Madagascar.
Small mammals and reptiles.
We analysed mitochondrial DNA data from 20 small‐mammal and five reptile species widely distributed across Madagascar's moist evergreen forests. We used phylogenetic and population genetic analyses to identify major phylogeographic patterns, then used linear regression to determine if the strength of phylogeographic structure is related to taxon, body size or elevation. Finally, we tested whether or not divergence across highlands occurred synchronously in multiple species, and used simulations to assess the power of these analyses to accurately estimate divergence times.
We observed a shared phylogeographic pattern across multiple species that suggests Madagascar's northern, central and southern highlands have served as important regions of diversification on Madagascar. This pattern was recovered across taxa with varying body sizes and elevational distributions. We also identified four pulses of divergence between the northern and central highlands since the late Miocene, although simulations suggest that our empirical data cannot recover the number or timing of divergence events with high certainty. Finally, we observed several instances of deep intraspecific genetic splits, suggesting that several of the species we evaluated may represent cryptic species complexes.
We identified a highland‐driven phylogeographic pattern plus several cases of cryptic endemism and recent speciation, which have important evolutionary and conservation implications. This work presents a new phylogeographic hypothesis for recent diversification on Madagascar, reaffirms the urgent need for continued collection of voucher specimens and illuminates areas of particular importance for safeguarding genetic diversity in one of the world's foremost and threatened biodiversity hotspots.