The Greater Antilles are renowned as a biodiversity hotspot and known to be geologically complex, which has led, in part, to the generation of organismal diversity in this area. One of the most species-rich montane groups within the Greater Antilles is the tribe Miconieae (Miconia s.l.) of the Melastomataceae, with ca. 325 species found there. The most diverse clade of Miconia in the Caribbean, the Caribbean clade, composes roughly half of that diversity, with an estimated 160 species, nearly all of which are endemic to the Greater Antilles. It is unclear how that diversity has been generated through time or where it originated, but we now have sufficiently well-sampled and robust datasets to test these patterns. Using a custom-built plastome dataset, we generated a robust phylogenetic hypothesis for 106 of the 160 Caribbean clade members and tested biogeographical patterns among the islands. Our results suggest that the Caribbean clade originated in the mid-Miocene, probably from a South American ancestor, and diversified substantially on the island of Cuba before repeatedly dispersing across other parts of the Greater Antilles, especially into nearby Hispaniola and then, to a lesser extent, into Jamaica, Puerto Rico and, finally, into the Lesser Antilles.
more » « lessThe Caribbean islands are in the top five biodiversity hotspots on the planet; however, the biogeographic history of the seasonally dry tropical forest (SDTF) there is poorly studied.
We reconstructed the phylogeny of
Pleistocene aridification associated with glaciation likely played a role in shaping the current diversity of
Scorpions are an excellent system for understanding biogeographical patterns. Most major scorpion lineages predate modern landforms, making them suitable for testing hypotheses of vicariance and dispersal. The Caribbean islands are endowed with a rich and largely endemic scorpion fauna, the origins of which have not been previously investigated with modern biogeographical methods. Three sets of hypotheses have been proposed to explain present patterns of diversity in the Caribbean: (1) connections via land bridges, (2) vicariance events, and (3) overwater dispersal from continents and among islands. The present study investigates the biogeographical diversification of the New World buthid scorpion subfamily Centruroidinae Kraus, 1955, a clade of seven genera and more than 110 species; infers the ancestral distributions of these scorpions; and tests the relative roles of vicariance and dispersal in the formation of their present distributions. A fossil-calibrated molecular phylogeny was estimated with a Bayesian criterion to infer the dates of diversification events from which ancestral distributions were reconstructed, and the relative likelihood of models of vicariance vs. dispersal, calculated. Although both the timing of diversification and the ancestral distributions were congruent with the GAARlandia land-bridge hypothesis, there was no significant difference between distance-dependent models with or without the land-bridge.
Island systems provide excellent arenas to test evolutionary hypotheses pertaining to gene flow and diversification of dispersal-limited organisms. Here we focus on an orbweaver spider genus
We explored the evolutionary radiation in the House Wren complex (Troglodytes aedon and allies), the New World’s most widely distributed passerine species. The complex has been the source of ongoing taxonomic debate. To evaluate phenotypic variation in the House Wren complex, we collected 81,182 single-nucleotide polymorphisms (SNPs) from restriction site associated loci (RADseq) and mitochondrial DNA (mtDNA) from samples representing the taxonomic and geographic diversity of the complex. Both datasets reveal deep phylogeographic structuring, with several topological discrepancies. The trees highlight the evolutionary distinctiveness of eastern and western T. aedon, which were sister taxa in the SNP tree and paraphyletic on the mtDNA tree. The RADseq data reveal a distinct T. a. brunneicollis group, although STRUCTURE plots suggest admixture between western T. aedon and northern Mexican samples of T. a. brunneicollis. MtDNA data show a paraphyletic arrangement of T. a. musculus on the tree, whereas the SNP tree portrays them as monophyletic. Island taxa are distinct in both datasets, including T. a. beani (Isla Cozumel), which appears derived from T. a. musculus in eastern Mexico, and T. sissonii (Isla Socorro) and T. tanneri (Isla Clarión) although the 2 datasets disagree on their overall phylogenetic placement. Although we had only mtDNA data for T. a. martinicensis from the Lesser Antilles, we found at least 4 distinct and paraphyletic taxa from Trinidad, Granada, St. Vincent islands, and Dominica. The House Wren complex showed strong differentiation in mtDNA and RADseq datasets, with conflicting patterns likely arising from some combination of sex-biased dispersal, incomplete lineage sorting, or selection on mtDNA. The most glaring discrepancies between these 2 datasets, such as the paraphyly of eastern and western North American House Wrens in the mtDNA tree, present excellent opportunities for follow-up studies on evolutionary mechanisms that underpin phylogeographic patterns.
