Search

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.] [ABSTRACT FROM AUTHOR]

Zoos and natural history museums are both collections-based institutions with important missions in biodiversity research and education. Animals in zoos are a repository and living record of the world's biodiversity, whereas natural history museums are a permanent historical record of snapshots of biodiversity in time. Surprisingly, despite significant overlap in institutional missions, formal partnerships between these institution types are infrequent. Life history information, pedigrees, and medical records maintained at zoos should be seen as complementary to historical records of morphology, genetics, and distribution kept at museums. Through examining both institution types, we synthesize the benefits and challenges of cross-institutional exchanges and propose actions to increase the dialog between zoos and museums. With a growing recognition of the importance of collections to the advancement of scientific research and discovery, a transformational impact could be made with long-term investments in connecting the institutions that are caretakers of living and preserved animals. [ABSTRACT FROM AUTHOR]

The role of the environmental niche in fostering ecological divergence during adaptive radiation remains enigmatic. In this study, we examine the interplay between environmental niche divergence and conservatism in the context of adaptive radiation on oceanic islands, by characterizing the niche breadth of four Hawaiian arthropod radiations: Tetragnatha spiders (Tetragnathidae Latreille, 1804), Laupala crickets (Gryllidae Otte, 1994), a clade of Drosophila flies (Drosophilidae Fallén, 1823) and Nesosydne planthoppers (Delphacidae Kirkaldy, 1907). We assembled occurrence datasets for the four lineages, modelled their distributions and quantified niche overlap. All four groups occupy the islands in distinct ways, highlighting the contrasting axes of diversification for different lineages. Laupala and Nesosydne have opposite environmental niche extents (broad and narrow, respectively), whereas Tetragnatha and Drosophila share relatively intermediate tolerances. Temperature constrains the distributions of all four radiations. Tests of phylogenetic signal suggest that, for Tetragnatha and Drosophila, closely related species exhibit similar environmental niches; thus, diversification is associated with niche conservatism. Sister species comparisons also show that populations often retain similar environmental tolerances, although exceptions do occur. Results imply that diversification does not occur through ecological speciation; instead, adaptive radiation occurs largely within a single environment. [ABSTRACT FROM AUTHOR]

Bell's and Sagebrush sparrows (Artemisiospiza belli and A. nevadensis) are phenotypically and genetically distinct, but data have yielded contradictory findings for A. belli subspecies. Disjunct populations of A. b. canescens from the San Joaquin Valley and Mojave Desert are phenotypically indistinguishable but diagnosable from Coast Range A. b. belli. However, San Joaquin Valley A. b. canescens shares allozymes and mitochondrial DNA (mtDNA) with A. b. belli whereas Mojave Desert A. b. canescens is genetically distinct. Furthermore, Great Basin A. nevadensis is closer in mtDNA to non-desert A. belli subspecies than to Mojave Desert A. b. canescens, with which it contacts across an aridland transition. We assessed concordance of song with genetics and phenotype for these taxa, and also analysed songs and mtDNA for A. b. clementeae which is endemic to arid San Clemente Island off the coast of southern California. Songs of open, arid habitat populations (A. nevadensis, A. b. canescens, A. b. clementeae) are consistently more similar to each other than they are to songs of coastal A. b. belli. We examined bioclimatic and land cover conditions to understand the basis for these patterns across ecoregions, and discuss the effect of the acoustic environment on song. [ABSTRACT FROM AUTHOR]

Niche divergence or conservatism and phenotypic adaptation are important in lineage diversification. We used mitochondrial DNA ( mtDNA), morphology and ecological niche models to examine these processes in three subspecies of Sage Sparrow ( Artemisiospiza belli belli, A. b. canescens and A. b. nevadensis) that breed in bioclimatically diverse ecoregions in western North America. Overall, mtDNA and morphology are congruent with subspecies, ecoregion and bioclimatic niche. Niche divergence, rather than niche conservatism, accompanied by phenotypic adaptation, is associated with lineage diversification between subspecies. This diversification has occurred with and without physical barriers or accompanying genetic divergence. Populations of A. b. canescens are divided by a montane barrier into two bioclimatic regions ( San Joaquin Valley, Mojave Desert), where they are indistinguishable phenotypically, but show distinctive genetic patterns. Although there is no physical barrier between A. b. canescens in the San Joaquin Valley and A. b. belli in the Coast Ranges, these populations occupy different bioclimatic niches and are phenotypically, but not genetically, diagnosable. Niche overlap is greatest between A. b. canescens from the Mojave Desert and A. b. nevadensis from the Great Basin, yet these subspecies maintain distinctive phenotypes and mtDNA, even in local secondary contact and sympatry. Palaeoclimatic niche models for the Last Glacial Maximum ( c. 21 000 bp) and the Last Interglacial ( c. 120 000 bp) suggest that ecoregionally distinct populations of Artemisiospiza belli experienced different Pleistocene range fluctuations and glacial refugia, with temporal niche conservatism. Populations probably reached their current distributions as favourable climates and habitats expanded after the last glaciation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ••, ••-••. [ABSTRACT FROM AUTHOR]

We investigate the roles of mitochondrial introgression and incomplete lineage sorting during the phylogenetic history of crotaphytid lizards. Our Bayesian phylogenetic estimate for Crotaphytidae is based on analysis of mitochondrial DNA sequence data for 408 individuals representing the 12 extant species of Crotaphytus and Gambelia. The mitochondrial phylogeny disagrees in several respects with a previously published morphological tree, as well as with conventional species designations, and we conclude that some of this disagreement stems from hybridization-mediated mitochondrial introgression, as well as from incomplete lineage sorting. Unidirectional introgression of Crotaphytus collaris (western collared lizard) mitochondria into C. reticulatus (reticulate collared lizard) populations in the Rio Grande Valley of Texas has resulted in the replacement of ancestral C. reticulatus mitochondria over approximately two-thirds of the total range of the species, a linear distance of ∼270 km. Introgression of C. collaris mitochondria into C. bicinctores (Great Basin collared lizard) populations in southwestern Arizona requires a more complex scenario because at least three temporally separated and superimposed introgression events appear to have occurred in this region. We propose an “introgression conveyor” model to explain this unique pattern of mitochondrial variation in this region. We show with ecological niche modeling that the predicted geographical ranges of C. collaris, C. bicinctores, and C. reticulatus during glacial maxima could have provided enhanced opportunities for past hybridization. Our analyses suggest that incomplete lineage sorting and/or introgression has further confounded the phylogenetic placements of additional species including C. nebrius, C. vestigium, C. insularis, C. grismeri, and perhaps G. copei. Despite many independent instances of interspecific hybridization among crotaphytid lizards, the species continue to maintain morphological and geographic cohesiveness throughout their ranges. [ABSTRACT FROM AUTHOR]