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Invasive species offer insights into rapid adaptation to novel environments. The iconic cane toad (Rhinella marina) is an excellent model for studying rapid adaptation during invasion. Previous research using the mitochondrial NADH dehydrogenase 3 (ND3) gene in Hawai'ian and Australian invasive populations found a single haplotype, indicating an extreme genetic bottleneck following introduction. Nuclear genetic diversity also exhibited reductions across the genome in these two populations. Here, we investigated the mitochondrial genomics of cane toads across this invasion trajectory. We created the first reference mitochondrial genome for this species using long‐read sequence data. We combined whole‐genome resequencing data of 15 toads with published transcriptomic data of 125 individuals to construct nearly complete mitochondrial genomes from the native (French Guiana) and introduced (Hawai'i and Australia) ranges for population genomic analyses. In agreement with previous investigations of these populations, we identified genetic bottlenecks in both Hawai'ian and Australian introduced populations, alongside evidence of population expansion in the invasive ranges. Although mitochondrial genetic diversity in introduced populations was reduced, our results revealed that it had been underestimated: we identified 45 mitochondrial haplotypes in Hawai'ian and Australian samples, none of which were found in the native range. Additionally, we identified two distinct groups of haplotypes from the native range, separated by a minimum of 110 base pairs (0.6%). These findings enhance our understanding of how invasion has shaped the genetic landscape of this species. [ABSTRACT FROM AUTHOR]

The Wet Tropics (WT) population of the yellow-bellied glider Petaurus australis Shaw, 1791 in North Queensland is listed as Endangered at the state and national level, but its taxonomic classification is currently uncertain. Here we expand on previous genetic and morphological analyses of the WT population with additional samples and genetic loci to re-assess its subspecific status. Phylogenetic analyses of the mitochondrial NADH dehydrogenase subunit 4 (ND4) gene showed that the WT population formed a reciprocally monophyletic group relative to a group comprising P. australis from its remaining distribution in Australia. The genetic distinction of the WT population was further corroborated by analyses of the nuclear gene von Willebrand factor. Molecular clock analyses of combined ND2 – ND4 data suggested that the WT population has been isolated from neighbouring populations in southern Queensland over multiple ice age cycles. Morphological analyses show that the WT gliders are smaller, with proportionally shortened faces, and have paler bellies compared to southern yellow-bellied gliders. We, therefore, propose that the WT population be recognised as a distinct subspecies which we herein describe. This taxonomic reassessment of P. australis has important implications for the ongoing conservation management of the WT population and yellow-bellied gliders throughout Australia. The yellow-bellied glider Petaurus australis Shaw, 1791 population in North Queensland is listed as Endangered at the national level, but its taxonomic classification is uncertain. Here we apply new morphological and genetic analyses and propose that it represents a unique, currently undescribed subspecies. Resolving the taxonomy of P. australis has important implications for its ongoing conservation management. Photograph by Rupert Russell. [ABSTRACT FROM AUTHOR]

In the waters of southeast Australia, two species of sawshark—the common (Pristiophorus cirratus) and southern (Pristiophorus nudipinnis) sawshark—are frequent by-catch in commercial fisheries. While harvesting of both species is currently considered sustainable, there has been no investigation of whether P. cirratus and P. nudipinnis display genetically distinct populations throughout their ranges. Such information is necessary for effective management of these species in commercial fisheries. This study examined population structure in both sawshark species through analysis of two mitochondrial genes: cytochrome b (Cyt-b) and NADH dehydrogenase subunit 5 (ND5). Results indicated contrasting levels of population structure, with P. cirratus consisting of two, possibly three, genetically distinct populations with two mitochondrial lineages and P. nudipinnis consisting of a single population. Tests for population expansion also highlighted differences between the two species. Population expansion was detected for the entire P. nudipinnis population, whereas this was only the case for one mitochondrial lineage in P. cirratus. The entire P. cirratus population displayed signals of demographic stability. It is hypothesised that the opening and closing of Bass Strait during glacial-interglacial cycles played a major role in shaping the population structure and expansion signatures observed in this study. Mitochondrial data also suggest that patterned and uniform brown P. cirratus are the same species. Fisheries managers should consider adopting two management units in southern Australia—one along the east coast (for the eastern P. cirratus population) and one along the south coast (for the southern P. cirratus population and the single P. nudipinnis population). [ABSTRACT FROM AUTHOR]

Diversifying selection between populations that inhabit different environments can promote lineage divergence within species and ultimately drive speciation. The mitochondrial genome (mitogenome) encodes essential proteins of the oxidative phosphorylation (OXPHOS) system and can be a strong target for climate-driven selection (i.e., associated with inhabiting different climates). We investigated whether Pleistocene climate changes drove mitochondrial selection and evolution within Australian birds. First, using phylogeographic analyses of the mitochondrial ND2 gene for 17 songbird species, we identified mitochondrial clades (mitolineages). Second, using distance-based redundancy analyses, we tested whether climate predicts variation in intraspecific genetic divergence beyond that explained by geographic distances and geographic position. Third, we analysed 41 complete mitogenome sequences representing each mitolineage of 17 species using codon models in a phylogenetic framework and a biochemical approach to identify signals of selection on OXPHOS protein-coding genes and test for parallel selection in mitolineages of different species existing in similar climates. Of 17 species examined, 13 had multiple mitolineages (range: 2-6). Climate was a significant predictor of mitochondrial variation in eight species. At least two amino acid replacements in OXPHOS complex I could have evolved under positive selection in specific mitolineages of two species. Protein homology modelling showed one of these to be in the loop region of the ND6 protein channel and the other in the functionally critical helix HL region of ND5. These findings call for direct tests of the functional and evolutionary significance of mitochondrial protein candidates for climate-associated selection., (© 2018 John Wiley & Sons Ltd.)