Dataset Information

Genetic diversity and drivers of dwarfism in extinct island emu populations.

ABSTRACT: Australia's iconic emu (Dromaius novaehollandiae novaehollandiae) is the only living representative of its genus, but fossil evidence and reports from early European explorers suggest that three island forms (at least two of which were dwarfs) became extinct during the nineteenth century. While one of these-the King Island emu-has been found to be conspecific with Australian mainland emus, little is known about how the other two forms-Kangaroo Island and Tasmanian emus-relate to the others, or even the size of Tasmanian emus. We present a comprehensive genetic and morphological analysis of Dromaius diversity, including data from one of the few definitively genuine Tasmanian emu specimens known. Our genetic analyses suggest that all the island populations represent sub-populations of mainland Dnovaehollandiae Further, the size of island emus and those on the mainland appears to scale linearly with island size but not time since isolation, suggesting that island size-and presumably concomitant limitations on resource availability-may be a more important driver of dwarfism in island emus, though its precise contribution to emu dwarfism remains to be confirmed.

SUBMITTER: Thomson VA

PROVIDER: S-EPMC5938559 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Genetic diversity and drivers of dwarfism in extinct island emu populations.

Thomson Vicki A VA Mitchell Kieren J KJ Eberhard Rolan R Dortch Joe J Austin Jeremy J JJ Cooper Alan A

Biology letters 20180401 4

Australia's iconic emu (<i>Dromaius novaehollandiae novaehollandiae</i>) is the only living representative of its genus, but fossil evidence and reports from early European explorers suggest that three island forms (at least two of which were dwarfs) became extinct during the nineteenth century. While one of these-the King Island emu-has been found to be conspecific with Australian mainland emus, little is known about how the other two forms-Kangaroo Island and Tasmanian emus-relate to the other ...[more]

PMID: 29618519

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Project description:BackgroundIn recent years, the Asian tiger mosquito Aedes albopictus has emerged as a species of major medical concern following its global expansion and involvement in many arbovirus outbreaks. On Réunion Island, Ae. albopictus was responsible for a large chikungunya outbreak in 2005-2006 and more recently an epidemic of dengue which began at the end of 2017 and is still ongoing at the time of writing. This dengue epidemic has seen a high number of human cases in south and west coastal regions, while few cases have been reported in the north and east of the island. To better understand the role of mosquito populations in such spatial patterns of dengue virus transmission in Réunion Island, we examined the genetic diversity and population structure of Ae. albopictus sampled across the island.ResultsBetween November 2016 and March 2017, a total of 564 mosquitoes were collected from 19 locations in three main climatic regions (West, East and Center) of Réunion Island and were genotyped using 16 microsatellite loci. A high genetic diversity was observed with 2-15 alleles per locus and the average number of alleles per population varying between 4.70-5.90. Almost all FIS values were significantly positive and correlated to individual relatedness within populations using a hierarchical clustering approach based on principal components analyses (HCPC). However, the largest part of genetic variance was among individuals within populations (97%) while only 3% of genetic variance was observed among populations within regions. Therefore, no distinguishable population structure or isolation by distance was evidenced, suggesting high rates of gene flow at the island scale.ConclusionsOur results show high genetic diversity but no genetic structure of Ae. albopictus populations in Réunion Island thus reflecting frequent movements of mosquitoes between populations probably due to human activity. These data should help in the understanding of Ae. albopictus vector capacity and the design of effective mosquito control strategies.

Project description:BACKGROUND:The Caribbean offers a unique opportunity to study evolutionary dynamics in insular mammals. However, the recent extinction of most Caribbean non-volant mammals has obstructed evolutionary studies, and poor DNA preservation associated with tropical environments means that very few ancient DNA sequences are available for extinct vertebrates known from the region's Holocene subfossil record. The endemic Caribbean eulipotyphlan family Nesophontidae ("island-shrews") became extinct ~?500?years ago, and the taxonomic validity of many Nesophontes species and their wider evolutionary dynamics remain unclear. Here we use both morphometric and palaeogenomic methods to clarify the status and evolutionary history of Nesophontes species from Hispaniola, the second-largest Caribbean island. RESULTS:Principal component analysis of 65 Nesophontes mandibles from late Quaternary fossil sites across Hispaniola identified three non-overlapping morphometric clusters, providing statistical support for the existence of three size-differentiated Hispaniolan Nesophontes species. We were also able to extract and sequence ancient DNA from a?~?750-year-old specimen of Nesophontes zamicrus, the smallest non-volant Caribbean mammal, including a whole-mitochondrial genome and partial nuclear genes. Nesophontes paramicrus (39-47?g) and N. zamicrus (~?10?g) diverged recently during the Middle Pleistocene (mean estimated divergence?=?0.699?Ma), comparable to the youngest species splits in Eulipotyphla and other mammal groups. Pairwise genetic distance values for N. paramicrus and N. zamicrus based on mitochondrial and nuclear genes are low, but fall within the range of comparative pairwise data for extant eulipotyphlan species-pairs. CONCLUSIONS:Our combined morphometric and palaeogenomic analyses provide evidence for multiple co-occurring species and rapid body size evolution in Hispaniolan Nesophontes, in contrast to patterns of genetic and morphometric differentiation seen in Hispaniola's extant non-volant land mammals. Different components of Hispaniola's mammal fauna have therefore exhibited drastically different rates of morphological evolution. Morphological evolution in Nesophontes is also rapid compared to patterns across the Eulipotyphla, and our study provides an important new example of rapid body size change in a small-bodied insular vertebrate lineage. The Caribbean was a hotspot for evolutionary diversification as well as preserving ancient biodiversity, and studying the surviving representatives of its mammal fauna is insufficient to reveal the evolutionary patterns and processes that generated regional diversity.

Dataset Information

Genetic diversity and drivers of dwarfism in extinct island emu populations.

Publications

Genetic diversity and drivers of dwarfism in extinct island emu populations.

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