Between a rock and a dry place: phylogenomics, biogeography, and systematics of ridge-tailed monitors (Squamata: Varanidae: Varanus acanthurus complex).

Genomic data are a powerful tool for the elucidation of evolutionary patterns at the population level and above. The combined analysis of genomic and morphological data can result in species delimitation hypotheses that reflect evolutionary history better than traditional taxonomy or any individual source of evidence. Here, we used thousands of single nucleotide polymorphisms, mitochondrial sequences, and comprehensive morphological data to characterize the evolutionary history of the ridge-tailed monitors in the Varanus acanthurus complex (V. acanthurus, V. baritji, and V. storri), a group of saxicolous lizards with a wide distribution in Australia, the driest vegetated continent. We found substantial genetic structure in the group and identify nine geographically clustered populations. Based on admixture patterns and species delimitation analyses we propose a taxonomic scheme that differs from current taxonomy. We consider V. acanthurus as monotypic, synonymize V. baritji with V. a. insulanicus (as a redefined V. insulanicus), elevate the subspecies of V. storri to full species (V. storri and V. ocreatus), and describe a new species from a previously identified center of endemism. The relationships among the species remain unresolved, likely as a result of fast speciation. Our study highlights the capability of large datasets to illuminate admixture patterns, biogeographic history, and species limits, even when phylogeny is not completely resolved. Furthermore, our results highlight the impact that the Cenozoic aridification of Australia had on saxicolous taxa and the role of mesic rocky escarpments as refugia. These habitats apparently allowed the persistence of lineages that became sources of colonization for arid environments.

Molecular and morphological assessment of Varanus pilbarensis (Squamata: Varanidae), with a description of a new species from the southern Pilbara, Western Australia.

Varanus pilbarensis Storr, 1980 is a specialised saxicolous varanid endemic to the Pilbara region of Western Australia. We present genetic and morphological evidence confirming the existence of a divergent southern lineage, here described as V. hamersleyensis sp. nov.. The new species differs noticeably in having a darker colouration and a reduced pattern of small whitish ocelli on the dorsal surface of the limbs only with a largely unbanded tail. By contrast, V. pilbarensis which is redescribed and restricted to the northern lineage, is paler and more boldly patterned with large greyish ocelli on the dorsal and lateral surfaces of the body and a strongly banded tail. The two species have discrete distributions centred on the Chichester and Hamersley Ranges to the north and south of the Fortescue River Basin. This pattern of intraregional genetic structuring is similar to that found in a number of other saxicolous lizard lineages from the Pilbara.

Characterisation of novel and rare Y-chromosome short tandem repeat alleles in self-declared South Australian Aboriginal database.

Y-chromosome short tandem repeats (Y-STRs) are used in forensic science laboratories all over the world, as their application is wide and often vital in solving casework. Analysis of an in-house database of South Australian self-declared Aboriginal males held by Forensic Science South Australia (FSSA) using the Applied Biosystem's AmpFℓSTR® Yfiler™ PCR Amplification Kit revealed 43 variant Y-STR alleles at 6 of the 17 loci. All variant alleles were sequenced to determine the exact repeat structure for each. As a high level of admixture has previously been found within the SA Aboriginal database, samples were haplogrouped using Y-SNPs to determine their likely geographical origin. Although a number of variant alleles were associated with non-Aboriginal Y-haplogroups, a high frequency was observed within the Australian K-M9 lineage. Detailed knowledge of these variant alleles may have further application in the development of new DNA markers for identification purposes, and in population and evolutionary studies of Australian Aborigines.

Confined aquifers as viral reservoirs.

Knowledge about viral diversity and abundance in deep groundwater reserves is limited. We found that the viral community inhabiting a deep confined aquifer in South Australia was more similar to reclaimed water communities than to the viral communities in the overlying unconfined aquifer community. This similarity was driven by high relative occurrence of the single-stranded DNA viral groups Circoviridae, Geminiviridae and Microviridae, which include many known plant and animal pathogens. These groups were present in a 1500-year-old water situated 80 m below the surface, which suggests the potential for long-term survival and spread of potentially pathogenic viruses in deep, confined groundwater. Obtaining a broader understanding of potentially pathogenic viral communities within aquifers is particularly important given the ability of viruses to spread within groundwater ecosystems.

Molecular evidence for an Asian origin of monitor lizards followed by Tertiary dispersals to Africa and Australasia.

Monitor lizards are emblematic reptiles that are widely distributed in the Old World. Although relatively well studied in vertebrate research, their biogeographic history is still controversial. We constructed a molecular dataset for 54 anguimorph species, including representatives of all families with detailed sampling of the Varanidae (38 species). Our results are consistent with an Asian origin of the Varanidae followed by a dispersal to Africa 41 (49-33) Ma, possibly via an Iranian route. Another major event was the dispersal of monitors to Australia in the Late Eocene-Oligocene 32 (39-26) Ma. This divergence estimate adds to the suggestion that Australia was colonized by several squamate lineages prior to the collision of the Australian plate with the Asian plate starting 25 Ma.

Panmixia supports divergence with gene flow in Darwin's small ground finch, Geospiza fuliginosa, on Santa Cruz, Galápagos Islands.

The divergence-with-gene-flow model of speciation has a strong theoretical basis with a growing number of plausible examples in nature, but remains hotly debated. Darwin's finches of the Galápagos Archipelago have played an important role in our understanding of speciation processes. Recent studies suggest that this group may also provide insights into speciation via divergence with gene flow. On the island of Santa Cruz, recent studies found evidence for adaptive divergence in Darwin's small ground finch, Geospiza fuliginosa, between ecologically contrasting arid and humid zones. Despite the short geographical distance between these zones, strong disruptive selection during low rainfall periods is expected to generate and maintain adaptive divergence. Conversely, during high rainfall periods, when disruptive selection is predicted to be weakened, population divergence in adaptive traits is expected to break down. Because periods of low and high rainfall irregularly alternate, the geographical pattern of adaptive divergence can be assumed to break down and, importantly, regenerate in situ. Here, we use microsatellite allele frequency data to assess the genetic population structure of G. fuliginosa on Santa Cruz. We sample 21 sites and four ecological zones across the island. We reject hypotheses of population substructure linked to ecological and geographical differences among sites in favour of a single panmictic population. Panmixia implies high levels of gene flow within Santa Cruz, which favours selection over genetic drift as a valid process generating phenotypic divergence in G. fuliginosa on Santa Cruz. We discuss how our findings may support classic adaptation, phenotypic plasticity, matching habitat choice or any combination of these three processes.

Metagenomic comparison of microbial communities inhabiting confined and unconfined aquifer ecosystems.

A metagenomic analysis of two aquifer systems located under a dairy farming region was performed to examine to what extent the composition and function of microbial communities varies between confined and surface-influenced unconfined groundwater ecosystems. A fundamental shift in taxa was seen with an overrepresentation of Rhodospirillales, Rhodocyclales, Chlorobia and Circovirus in the unconfined aquifer, while Deltaproteobacteria and Clostridiales were overrepresented in the confined aquifer. A relative overrepresentation of metabolic processes including antibiotic resistance (ß-lactamase genes), lactose and glucose utilization and DNA replication were observed in the unconfined aquifer, while flagella production, phosphate metabolism and starch uptake pathways were all overrepresented in the confined aquifer. These differences were likely driven by differences in the nutrient status and extent of exposure to contaminants of the two groundwater systems. However, when compared with freshwater, ocean, sediment and animal gut metagenomes, the unconfined and confined aquifers were taxonomically and metabolically more similar to each other than to any other environment. This suggests that intrinsic features of groundwater ecosystems, including low oxygen levels and a lack of sunlight, have provided specific niches for evolution to create unique microbial communities. Obtaining a broader understanding of the structure and function of microbial communities inhabiting different groundwater systems is particularly important given the increased need for managing groundwater reserves of potable water.

Rise of the machines--recommendations for ecologists when using next generation sequencing for microsatellite development.

Next generation sequencing is revolutionizing molecular ecology by simplifying the development of molecular genetic markers, including microsatellites. Here, we summarize the results of the large-scale development of microsatellites for 54 nonmodel species using next generation sequencing and show that there are clear differences amongst plants, invertebrates and vertebrates for the number and proportion of motif types recovered that are able to be utilized as markers. We highlight that the heterogeneity within each group is very large. Despite this variation, we provide an indication of what number of sequences and consequent proportion of a 454 run are required for the development of 40 designable, unique microsatellite loci for a typical molecular ecological study. Finally, to address the challenges of choosing loci from the vast array of microsatellite loci typically available from partial genome runs (average for this study, 2341 loci), we provide a microsatellite development flowchart as a procedural guide for application once the results of a partial genome run are obtained.