Melissa T. R. Hawkins

Mitochondrial genomes suggest rapid evolution of dwarf California Channel Islands foxes (Urocyon littoralis).

Island endemics are typically differentiated from their mainland progenitors in behavior, morphology, and genetics, often resulting from long-term evolutionary change. To examine mechanisms for the origins of island endemism, we present a phylogeographic analysis of whole mitochondrial genomes from the endangered island fox (Urocyon littoralis), endemic to California’s Channel Islands, and mainland gray foxes (U. cinereoargenteus). Previous genetic studies suggested that foxes first appeared on the islands >16,000 years ago, before human arrival (~13,000 cal BP), while archaeological and paleontological data supported a colonization >7000 cal BP. Our results are consistent with initial fox colonization of the northern islands probably by rafting or human introduction ~9200–7100 years ago, followed quickly by human translocation of foxes from the northern to southern Channel Islands. Mitogenomes indicate that island foxes are monophyletic and most closely related to gray foxes from northern California that likely experienced a Holocene climate-induced range shift. Our data document rapid morphological evolution of island foxes (in ~2000 years or less). Despite evidence for bottlenecks, island foxes have generated and maintained multiple mitochondrial haplotypes. This study highlights the intertwined evolutionary history of island foxes and humans, and illustrates a new approach for investigating the evolutionary histories of other island endemics.

In-solution hybridization for mammalian mitogenome enrichment: pros, cons and challenges associated with multiplexing degraded DNA

Here, we present a set of RNA‐based probes for whole mitochondrial genome in‐solution enrichment, targeting a diversity of mammalian mitogenomes. This probes set was designed from seven mammalian orders and tested to determine the utility for enriching degraded DNA. We generated 63 mitogenomes representing five orders and 22 genera of mammals that yielded varying coverage ranging from 0 to >5400X. Based on a threshold of 70% mitogenome recovery and at least 10× average coverage, 32 individuals or 51% of samples were considered successful. The estimated sequence divergence of samples from the probe sequences used to construct the array ranged up to nearly 20%. Sample type was more predictive of mitogenome recovery than sample age. The proportion of reads from each individual in multiplexed enrichments was highly skewed, with each pool having one sample that yielded a majority of the reads. Recovery across each mitochondrial gene varied with most samples exhibiting regions with gaps or ambiguous sites. We estimated the ability of the probes to capture mitogenomes from a diversity of mammalian taxa not included here by performing a clustering analysis of published sequences for 100 taxa representing most mammalian orders. Our study demonstrates that a general array can be cost and time effective when there is a need to screen a modest number of individuals from a variety of taxa. We also address the practical concerns for using such a tool, with regard to pooling samples, generating high quality mitogenomes and detail a pipeline to remove chimeric molecules.

Corrected placement of Mus-Rattus fossil calibration forces precision in the molecular tree of rodents

Time calibration derived from the fossil record is essential for molecular phylogenetic and evolutionary studies. Fossil mice and rats, discovered in the Siwalik Group of Pakistan, have served as one of the best-known fossil calibration points in molecular phylogenic studies. Although these fossils have been widely used as the 12 Ma date for the Mus/Rattus split or a more basal split, conclusive paleontological evidence for the nodal assignments has been absent. This study analyzes newly recognized characters that demonstrate lineage separation in the fossil record of Siwalik murines and examines the most reasonable nodal placement of the diverging lineages in a molecular phylogenetic tree by ancestral state reconstruction. Our specimen-based approach strongly indicates that Siwalik murines of the Karnimata clade are fossil members of the Arvicanthini-Otomyini-Millardini clade, which excludes Rattus and its relatives. Combining the new interpretation with the widely accepted hypothesis that the Progonomys clade includes Mus, the lineage separation event in the Siwalik fossil record represents the Mus/Arvicanthis split. Our test analysis on Bayesian age estimates shows that this new calibration point provides more accurate estimates of murine divergence than previous applications. Thus, we define this fossil calibration point and refine two other fossil-based points for molecular dating.

Simultaneous identification of host, ectoparasite and pathogen DNA via in-solution capture.

Ectoparasites frequently vector pathogens from often unknown pathogen reservoirs to both human and animal populations. Simultaneous identification of the ectoparasite species, the wildlife host that provided their most recent blood meal(s), and their pathogen load would greatly facilitate the understanding of the complex transmission dynamics of vector‐borne diseases. Currently, these identifications are principally performed using multiple polymerase chain reaction (PCR) assays. We developed an assay (EctoBaits) based on in‐solution capture paired with high‐throughput sequencing to simultaneously identify ectoparasites, host blood meals and pathogens. We validated our in‐solution capture results using double‐blind PCR assays, morphology and collection data. The EctoBaits assay effectively and efficiently identifies ectoparasites, blood meals, and pathogens in a single capture experiment, allowing for high‐resolution taxonomic identification while preserving the DNA sample for future analyses.

Novel opsin gene variation in large-bodied, diurnal lemurs

Some primate populations include both trichromatic and dichromatic (red–green colour blind) individuals due to allelic variation at the X-linked opsin locus. This polymorphic trichromacy is well described in day-active New World monkeys. Less is known about colour vision in Malagasy lemurs, but, unlike New World monkeys, only some day-active lemurs are polymorphic, while others are dichromatic. The evolutionary pressures underlying these differences in lemurs are unknown, but aspects of species ecology, including variation in activity pattern, are hypothesized to play a role. Limited data on X-linked opsin variation in lemurs make such hypotheses difficult to evaluate. We provide the first detailed examination of X-linked opsin variation across a lemur clade (Indriidae). We sequenced the X-linked opsin in the most strictly diurnal and largest extant lemur, Indri indri, and nine species of smaller, generally diurnal indriids (Propithecus). Although nocturnal Avahi (sister taxon to Propithecus) lacks a polymorphism, at least eight species of diurnal indriids have two or more X-linked opsin alleles. Four rainforest-living taxa—I. indri and the three largest Propithecus species—have alleles not previously documented in lemurs. Moreover, we identified at least three opsin alleles in Indri with peak spectral sensitivities similar to some New World monkeys.

Evolutionary history of endemic Sulawesi squirrels constructed from UCEs and mitogenomes sequenced from museum specimens

BackgroundThe Indonesian island of Sulawesi has a complex geological history. It is composed of several landmasses that have arrived at a near modern configuration only in the past few million years. It is the largest island in the biodiversity hotspot of Wallacea—an area demarcated by the biogeographic breaks between Wallace’s and Lydekker’s lines. The mammal fauna of Sulawesi is transitional between Asian and Australian faunas. Sulawesi’s three genera of squirrels, all endemic (subfamily Nannosciurinae: Hyosciurus, Rubrisciurus and Prosciurillus), are of Asian origin and have evolved a variety of phenotypes that allow a range of ecological niche specializations. Here we present a molecular phylogeny of this radiation using data from museum specimens. High throughput sequencing technology was used to generate whole mitochondrial genomes and a panel of nuclear ultraconserved elements providing a large genome-wide dataset for inferring phylogenetic relationships.ResultsOur analysis confirmed monophyly of the Sulawesi taxa with deep divergences between the three endemic genera, which predate the amalgamation of the current island of Sulawesi. This suggests lineages may have evolved in allopatry after crossing Wallace’s line. Nuclear and mitochondrial analyses were largely congruent and well supported, except for the placement of Prosciurillus murinus. Mitochondrial analysis revealed paraphyly for Prosciurillus, with P. murinus between or outside of Hyosciurus and Rubrisciurus, separate from other species of Prosciurillus. A deep but monophyletic history for the four included species of Prosciurillus was recovered with the nuclear data.ConclusionsThe divergence of the Sulawesi squirrels from their closest relatives dated to ~9.7–12.5 million years ago (MYA), pushing back the age estimate of this ancient adaptive radiation prior to the formation of the current conformation of Sulawesi. Generic level diversification took place around 9.7 MYA, opening the possibility that the genera represent allopatric lineages that evolved in isolation in an ancient proto-Sulawesian archipelago. We propose that incongruence between phylogenies based on nuclear and mitochondrial sequences may have resulted from biogeographic discordance, when two allopatric lineages come into secondary contact, with complete replacement of the mitochondria in one species.

The Taxonomic Status of Mazama bricenii and the Significance of the Táchira Depression for Mammalian Endemism in the Cordillera de Mérida, Venezuela.

We studied the taxonomy and biogeography of Mazama bricenii, a brocket deer classified as Vulnerable by the IUCN, drawing on qualitative and quantitative morphology and sequences of the mitochondrial cytochrome-b gene. We used Ecological Niche Modeling (ENM) to evaluate the hypothesis that M. bricenii of the Venezuelan Cordillera de Mérida (CM) might have become isolated from populations of its putative sister species, Mazama rufina, in the Colombian Cordillera Oriental (CO). This hypothesis assumes that warm, dry climatic conditions in the Táchira Depression were unsuitable for the species. Our analyses did not reveal morphological differences between specimens geographically attributable to M. bricenii and M. rufina, and phylogenetic analyses of molecular data recovered M. bricenii nested within the diversity of M. rufina. These results indicate that M. bricenii should be regarded as a junior synonym of M. rufina. ENM analyses revealed the existence of suitable climatic conditions for M. rufina in the Táchira Depression during the last glacial maximum and even at present, suggesting that gene flow between populations in the CO and CM may have occurred until at least the beginning of the current interglacial period and may continue today. Because this pattern might characterize other mammals currently considered endemic to the CM, we examined which of these species match two criteria that we propose herein to estimate if they can be regarded as endemic to the CM with confidence: (1) that morphological or molecular evidence exists indicating that the putative endemic taxon is distinctive from congeneric populations in the CO; and (2) that the putative endemic taxon is restricted to either cloud forest or páramo, or both. Only Aepeomys reigi, Cryptotis meridensis, and Nasuella meridensis matched both criteria; hence, additional research is necessary to assess the true taxonomic status and distribution of the remaining species thought to be CM endemics.

Phylogeny, biogeography and systematic revision of plain long-nosed squirrels (genus Dremomys, Nannosciurinae)

The plain long-nosed squirrels, genus Dremomys, are high elevation species in East and Southeast Asia. Here we present a complete molecular phylogeny for the genus based on nuclear and mitochondrial DNA sequences. Concatenated mitochondrial and nuclear gene trees were constructed to determine the tree topology, and date the tree. All speciation events within the plain-long nosed squirrels (genus Dremomys) were ancient (dated to the Pliocene or Miocene), and averaged older than many speciation events in the related Sunda squirrels, genus Sundasciurus. Within the plain long-nosed squirrels, the most recent interspecific split occurred 2.9 million years ago, older than some splits within Sunda squirrels, which dated to the Pleistocene. Our results demonstrate that the plain long-nosed squirrels are not monophyletic. The single species with a distinct distribution, the Bornean mountain ground squirrel (Dremomys everetti), which is endemic to the high mountains of Borneo, is nested within the Sunda squirrels with high support. This species diverged from its sister taxa in the Sunda squirrels 6.62 million years ago, and other plain long-nosed squirrels over 11 million years ago. Our analyses of morphological traits in these related genera support the re-classification of the Bornean mountain ground squirrel, Dremomys everetti, to the genus Sundasciurus, which changes its name to Sundasciurus everetti. Past inclusion in the plain long-nosed squirrels (Dremomys) reflects convergent evolution between these high elevation species.

Genome sequence, population history, and pelage genetics of the endangered African wild dog ( Lycaon pictus )

BackgroundThe African wild dog (Lycaon pictus) is an endangered African canid threatened by severe habitat fragmentation, human-wildlife conflict, and infectious disease. A highly specialized carnivore, it is distinguished by its social structure, dental morphology, absence of dewclaws, and colorful pelage.ResultsWe sequenced the genomes of two individuals from populations representing two distinct ecological histories (Laikipia County, Kenya and KwaZulu-Natal Province, South Africa). We reconstructed population demographic histories for the two individuals and scanned the genomes for evidence of selection.ConclusionsWe show that the African wild dog has undergone at least two effective population size reductions in the last 1,000,000 years. We found evidence of Lycaon individual-specific regions of low diversity, suggestive of inbreeding or population-specific selection. Further research is needed to clarify whether these population reductions and low diversity regions are characteristic of the species as a whole. We documented positive selection on the Lycaon mitochondrial genome. Finally, we identified several candidate genes (ASIP, MITF, MLPH, PMEL) that may play a role in the characteristic Lycaon pelage.

Evaluating the Genetic Diversity of Three Endangered Lemur Species(Genus: Propithecus) from Northern Madagascar

1Bill and Berniece Grewcock Center for Conservation and Research, Omaha’s Henry Doorly Zoo and Aquarium, 3701 South 10th Street, Omaha, NE 68107, USA 2State University of New York Polytechnic Institute, 100 Seymour Road, Utica, NY 13502, USA 3University of Sherbrooke, Sherbrooke, QC J1K 2R1, Canada 4Conservation Fusion, 504 Ridgewood Dr, Bellevue, NE 68005, USA 5Madagascar Biodiversity Partnership, VO 12 Bis A, Antananarivo 101, Madagascar 6Department of Animal Biology, University of Antananarivo, Antananarivo 101, Madagascar 7Giraffe Conservation Foundation, P.O Box 86099, Eros, Windhoek, Namibia