Piecing together female extra-pair mate choice: females really do prefer more ornamented males.

Evolutionary biologists have long been fascinated by extravagant male traits that abound across the animal kingdom and yet convey no apparent benefits to survival. From isopods to elephants, from armaments to ornaments, researchers have spent decades studying male-male competition and female mate choice in an effort to understand the significance of these secondary sexual characteristics. Among socially monogamous species, a frequently proposed explanation for the existence of male ornaments is that they are indicators of male genetic quality subject to female extra-pair mate choice. However, despite over two decades of extensive research into extra-pair paternity (EPP), the evidence that females actually choose more ornamented extra-pair sires is surprisingly scant. Consequently, whether EPP and female choice have contributed to the evolution of male ornaments in socially monogamous species, and what fitness benefits (if any) they signal to females, remains unclear. Progress in this field has been hampered by the challenge of dissociating clear female choice for ornamentation from confounding factors. In this issue of Molecular Ecology, Whittingham & Dunn (2016) use an experimental approach in a bird species with very high rates of EPP to tease apart these correlative effects. In doing so, they demonstrate clearly that male ornamentation is subject to female extra-pair mate choice. Their findings further suggest that EPP can be adaptive for females, and represent an important step forward in validating the role of EPP as an evolutionary driver of ornamental elaboration in socially monogamous species.

On the sand and among the crowds: a new species of Woodworthia gecko (Reptilia: Diplodactylidae) from Auckland, Aotearoa/ New Zealand.

Woodworthia is a diverse genus of diplodactylid geckos found in Aotearoa/ New Zealand, with 17 likely species. Despite this diversity, only two species have been formally described: Woodworthia maculata (Gray, 1845) and W. chrysosiretica (Robb, 1980). In this paper, we use an integrated taxonomic approach to describe a new species of Woodworthia gecko, Woodworthia korowai sp. nov., found along the western coastline of the Auckland Region, New Zealand. Although this species occurs in duneland habitat behind a popular beach near New Zealands most populated city, it was only recognised as a distinct taxon in 2016. We describe W. korowai sp. nov. based on a suite of morphological character states and substantial genetic divergence, based on the mitochondrial NADH dehydrogenase subunit 2 (ND2) gene, that distinguish it from W. maculata sensu stricto and all other known species of Woodworthia. Phylogenetic reconstruction and molecular dating place it sister to the W. maculata group, with an estimated time of divergence in the mid to late Pliocene. This gecko is one of the most geographically restricted of all Woodworthia geckos, occupying an area of less than 500 km2 within the Auckland Region. Its narrow range and coastal association make it susceptible to environmental and genetic stochasticity. Furthermore, the popularity and recreational usage of the dune system threaten its habitat. Therefore, we hope that this description will bring attention to the value of coastal environments and the unique and sensitive duneland of Te Korowai-o-Te-Tonga/ South Kaipara Peninsula and Te Oneone Rangatira/ Muriwai Beach in particular and encourage conservation efforts to protect this newly described species and its habitat.

Long-read sequencing reveals atypical mitochondrial genome structure in a New Zealand marine isopod.

Most animal mitochondrial genomes are small, circular and structurally conserved. However, recent work indicates that diverse taxa possess unusual mitochondrial genomes. In Isopoda, species in multiple lineages have atypical and rearranged mitochondrial genomes. However, more species of this speciose taxon need to be evaluated to understand the evolutionary origins of atypical mitochondrial genomes in this group. In this study, we report the presence of an atypical mitochondrial structure in the New Zealand endemic marine isopod, Isocladus armatus. Data from long- and short-read DNA sequencing suggest that I. armatus has two mitochondrial chromosomes. The first chromosome consists of two mitochondrial genomes that have been inverted and fused together in a circular form, and the second chromosome consists of a single mitochondrial genome in a linearized form. This atypical mitochondrial structure has been detected in other isopod lineages, and our data from an additional divergent isopod lineage (Sphaeromatidae) lends support to the hypothesis that atypical structure evolved early in the evolution of Isopoda. Additionally, we find that an asymmetrical site previously observed across many species within Isopoda is absent in I. armatus, but confirm the presence of two asymmetrical sites recently reported in two other isopod species.

Concordant geographic and genetic structure revealed by genotyping-by-sequencing in a New Zealand marine isopod.

Population genetic structure in the marine environment can be influenced by life-history traits such as developmental mode (biphasic, with distinct adult and larval morphology, and direct development, in which larvae resemble adults) or habitat specificity, as well as geography and selection. Developmental mode is thought to significantly influence dispersal, with direct developers expected to have much lower dispersal potential. However, this prediction can be complicated by the presence of geophysical barriers to dispersal. In this study, we use a panel of 8,020 SNPs to investigate population structure and biogeography over multiple spatial scales for a direct-developing species, the New Zealand endemic marine isopod Isocladus armatus. Because our sampling range is intersected by two well-known biogeographic barriers (the East Cape and the Cook Strait), our study provides an opportunity to understand how such barriers influence dispersal in direct developers. On a small spatial scale (20 km), gene flow between locations is extremely high, suggestive of an island model of migration. However, over larger spatial scales (600 km), populations exhibit a clear pattern of isolation-by-distance. Our results indicate that I. armatus exhibits significant migration across the hypothesized barriers and suggest that large-scale ocean currents associated with these locations do not present a barrier to dispersal. Interestingly, we find evidence of a north-south population genetic break occurring between Mahia and Wellington. While no known geophysical barrier is apparent in this area, it coincides with the location of a proposed border between bioregions. Analysis of loci under selection revealed that both isolation-by-distance and adaption may be contributing to the degree of population structure we have observed here. We conclude that developmental life history largely predicts dispersal in the intertidal isopod I. armatus. However, localized biogeographic processes can disrupt this expectation, and this may explain the potential meta-population detected in the Auckland region.

Contrasting gene flow at different spatial scales revealed by genotyping-by-sequencing in Isocladus armatus, a massively colour polymorphic New Zealand marine isopod.

Understanding how genetic diversity is maintained within populations is central to evolutionary biology. Research on colour polymorphism (CP), which typically has a genetic basis, can shed light on this issue. However, because gene flow can homogenise genetic variation, understanding population connectivity is critical in examining the maintenance of polymorphisms. In this study we assess the utility of genotyping-by-sequencing to resolve gene flow, and provide a preliminary investigation into the genetic basis of CP in Isocladus armatus, an endemic New Zealand marine isopod. Analysis of the genetic variation in 4,000 single nucleotide polymorphisms (SNPs) within and among populations and colour morphs revealed large differences in gene flow across two spatial scales. Marine isopods, which lack a pelagic larval phase, are typically assumed to exhibit greater population structuring than marine invertebrates possessing a biphasic life cycle. However, we found high gene flow rates and no genetic subdivision between two North Island populations situated 8 km apart. This suggests that I. armatus is capable of substantial dispersal along coastlines. In contrast, we identified a strong genetic disjunction between North and South Island populations. This result is similar to those reported in other New Zealand marine species, and is congruent with the presence of a geophysical barrier to dispersal down the east coast of New Zealand. We also found some support for a genetic basis to colouration evidenced by positive FST outlier tests, with two SNPs in particular showing strong association to the expression of a striped morph. Our study provides one of the first population genomic studies of a marine organism in New Zealand, and suggests that genotyping-by-sequencing can be a good alternative to more traditional investigations based on traditional markers such as microsatellites. Our study provides a foundation for further development of a highly tractable system for research on the evolutionary maintenance of CP.

Isolation and characterization of microsatellite loci from Lochmaea suturalis, the heather beetle (Coleoptera: Chrysomelidae), a pest in Europe and a biocontrol agent in New Zealand.

The heather beetle Lochmaea suturalis which is native to northwest Europe has been released as a biocontrol agent for heather in New Zealand. We have isolated and optimized eight microsatellite loci from New Zealand beetles. These loci provide markers with high polymorphism ranging from four to 20 alleles per locus. Observed heterozygosity averaged 0.631 per locus. These results suggest the markers are useful for population studies that will contribute to assessment of L. suturalis as a biocontrol agent.