Speciation in chestnut-shouldered fairy-wrens (Malurus spp.) and rapid phenotypic divergence in variegated fairy-wrens (Malurus lamberti): a multilocus approach.
ABSTRACT The chestnut-shouldered fairy-wrens comprise a subgroup of four species in the genus Malurus (Passeriformes: Maluridae). Collectively, they are widespread across the Australian continent but phenotypic variation is strongly structured geographically in just one species, M. lamberti. Earlier phylogenetic analyses of this group have been limited to one or two individuals for each species and have not represented all currently recognised subspecies of M. lamberti. Historically, the taxonomy and nomenclature of the M. lamberti complex has been debated, in part because of morphological similarities among its subspecies and another member of the group, M. amabilis. We reconstructed the phylogeny of all four species of chestnut-shouldered fairy-wrens including all four subspecies of M. lamberti using a mitochondrial gene (ND2), five anonymous nuclear loci and three nuclear introns. Phylogenetic analysis of the mitochondrial ND2 gene nests M. amabilis within M. lamberti rendering the latter paraphyletic. Individual nuclear gene trees failed to reliably resolve each of the species boundaries or the phylogenetic relationships found in the mtDNA tree. When combined, however, a strongly supported overall topology was resolved supporting the monophyly of M. lamberti and its sister species relationship to M. amabilis. Current subspecific taxonomy of M. lamberti was not concordant with all evolutionary lineages of M. lamberti, nominotypical M. l. lamberti being the only subspecies recovered as a monophyletic group from mtDNA. Some genetic structuring is evident and potential barriers to gene flow are discussed.
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ABSTRACT: Methods that integrate population-level sampling from multiple taxa into a single community-level analysis are an essential addition to the comparative phylogeographic toolkit. Detecting how species within communities have demographically tracked each other in space and time is important for understanding the effects of future climate and landscape changes and the resulting acceleration of extinctions, biological invasions and potential surges in adaptive evolution. Here we present a statistical framework for such an analysis based on hierarchical approximate Bayesian computation (hABC) with the goal of detecting concerted demographic histories across an ecological assemblage. Our method combines population genetic datasets from multiple taxa into a single analysis to estimate: 1) the proportion of a community sample that demographically expanded in a temporally clustered pulse; and 2) when the pulse occurred. To validate the accuracy and utility of this new approach, we use simulation cross-validation experiments and subsequently analyze an empirical dataset of 32 avian populations from Australia that are hypothesized to have expanded from smaller refugia populations in the late Pleistocene. The method can accommodate dataset heterogeneity such as variability in effective population size, mutation rates, and sample sizes across species and exploits the statistical strength from the simultaneous analysis of multiple species. This hABC framework used in a multi-taxa demographic context can increase our understanding of the impact of historical climate change by determining what proportion of the community responded in concert or independently, and can be used with a wide variety of comparative phylogeographic datasets as biota-wide DNA barcoding data sets accumulate.Molecular Biology and Evolution 06/2014; · 14.31 Impact Factor
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ABSTRACT: The south-western land division of Western Australia (SWWA), bordering the temperate Southern and Indian Oceans, is the only global biodiversity hotspot recognised in Australia. Renowned for its extraordinary diversity of endemic plants, and for some of the largest and most botanically significant temperate heathlands and woodlands on Earth, SWWA has long fascinated biogeographers. Its flat, highly weathered topography and the apparent absence of major geographic factors usually implicated in biotic diversification have challenged attempts to explain patterns of biogeography and mechanisms of speciation in the region. Botanical studies have always been central to understanding the biodiversity values of SWWA, although surprisingly few quantitative botanical analyses have allowed for an understanding of historical biogeographic processes in both space and time. Faunistic studies, by contrast, have played little or no role in defining hotspot concepts, despite several decades of accumulating quantitative research on the phylogeny and phylogeography of multiple lineages. In this review we critically analyse datasets with explicit supporting phylogenetic data and estimates of the time since divergence for all available elements of the terrestrial fauna, and compare these datasets to those available for plants. In situ speciation has played more of a role in shaping the south-western Australian fauna than has long been supposed, and has occurred in numerous endemic lineages of freshwater fish, frogs, reptiles, snails and less-vagile arthropods. By contrast, relatively low levels of endemism are found in birds, mammals and highly dispersive insects, and in situ speciation has played a negligible role in generating local endemism in birds and mammals. Quantitative studies provide evidence for at least four mechanisms driving patterns of endemism in south-western Australian animals, including: (i) relictualism of ancient Gondwanan or Pangaean taxa in the High Rainfall Province; (ii) vicariant isolation of lineages west of the Nullarbor divide; (iii) in situ speciation; and (iv) recent population subdivision. From dated quantitative studies we derive four testable models of historical biogeography for animal taxa in SWWA, each explicit in providing a spatial, temporal and topological perspective on patterns of speciation or divergence. For each model we also propose candidate lineages that may be worthy of further study, given what we know of their taxonomy, distributions or relationships. These models formalise four of the strongest patterns seen in many animal taxa from SWWA, although other models are clearly required to explain particular, idiosyncratic patterns. Generating numerous new datasets for suites of co-occurring lineages in SWWA will help refine our understanding of the historical biogeography of the region, highlight gaps in our knowledge, and allow us to derive general postulates from quantitative (rather than qualitative) results. For animals, this process has now begun in earnest, as has the process of taxonomically documenting many of the more diverse invertebrate lineages. The latter remains central to any attempt to appreciate holistically biogeographic patterns and processes in SWWA, and molecular phylogenetic studies should – where possible – also lead to tangible taxonomic outcomes.Biological Reviews 08/2014; · 10.26 Impact Factor