Tania M. King

Phylogeographical disjunction in abundant high-dispersal littoral gastropods

Phylogeographical disjunctions in high‐dispersal marine taxa are variously ascribed to palaeogeographical conditions or contemporary ecological factors. Associated biogeographical studies, however, seldom incorporate the sampling design required to confidently discriminate among such competing hypotheses. In the current study, over 7800 gastropod specimens were examined for operculum colour, and 129 specimens genetically, to test ecological and historical biogeographical hypotheses relating to biogeographical disjunction in the Southern Hemisphere, and to southern Australia in particular. Mitochondrial DNA sequence analysis of the high‐dispersal intertidal gastropod Nerita atramentosa in southern Australia (88 specimens; 18 localities) revealed an east–west phylogeographical split involving two highly divergent clades (26.0 ± 1.9%) exhibiting minimal geographical overlap in the southeast. The eastern clade of Nerita atramentosa is also widespread in northern New Zealand (43 specimens, 10 localities), but no significant genetic differentiation is explained by the Tasman Sea, a 2000‐km‐wide oceanic barrier. Spatial genetic structure was not detected within either clade, consistent with the species’ dispersive planktotrophic phase lasting for 5–6 months. Digital analysis of operculum colouration revealed substantial differences between eastern (tan) and western (black) specimens. Genetic analysis and visual inspection of 88 Australian specimens revealed a completely nonrandom association between mtDNA data and operculum colouration. Independent examination of a further 7822 specimens from 14 sites in southern Australia revealed both colour morphs at all localities, but reinforced the phylogeographical data by indicating a marked turnover in colour morph abundance associated with a palaeogeographical barrier: Wilsons Promontory. This sharp biogeographical disjunction is in marked contrast to the species’ high dispersal abilities. The genetic similarity of Nerita morio (Easter Island) and the eastern Australian + New Zealand lineage (1.1 ± 0.3%) provides further evidence of long‐distance dispersal in southern Nerita. Phylogenetic relationships of nine species (four genera) of Neritidae, an almost exclusively tropical gastropod family, are consistent with the hypothesis that southern temperate black nerites comprise a monophyletic radiation.

DOES FISH ECOLOGY PREDICT DISPERSAL ACROSS A RIVER DRAINAGE DIVIDE

Abstract Obligate freshwater taxa are frequently distributed among catchments isolated by marine and terrestrial barriers. Such distributions can arise through vicariant changes in drainage geometry, or dispersal via intermittent freshwater connections. We employed two adjacent rivers in southern New Zealand to test for interdrainage dispersal while controlling for historical drainage geometry, and analyzed four ecologically distinct freshwater-limited fish taxa to assess any relationship with habitat preference. Individuals from the Mararoa and Oreti catchments (n >100 per species) were sequenced for a minimum of 1297 bp of mitochondrial DNA (cytochrome b and control region). Phylogeographic relationships were consistent with ecological expectations of interdrainage dispersal capability, with the two obligate riverine taxa each exhibiting reciprocal monophyly between catchments, whereas the two facultative swamp dwellers revealed paraphyletic relationships, one of which shared a haplotype between catchments. Statistical phylogeography, accommodating taxon-specific mutation rates and the known age of the last major riverine connection between these catchments, rejected complete isolation of populations for one of the swamp dwellers. Therefore, dispersal across a young (145–240 kyr) drainage divide is inferred for one species, and can be predicted to some extent by species ecology. Moreover, our study highlights the importance of historical drainage geometry when assessing the causes of contemporary genetic structuring in freshwater taxa.

Contrasting mtDNA diversity and population structure in a direct-developing marine gastropod and its trematode parasites.

The comparative genetic structure of hosts and their parasites has important implications for their coevolution, but has been investigated in relatively few systems. In this study, we analysed the genetic structure and diversity of the New Zealand intertidal snail Zeacumantus subcarinatus (n = 330) and two of its trematode parasites, Maritrema novaezealandensis (n = 269) and Philophthalmus sp. (n = 246), using cytochrome c oxidase subunit I gene (COI) sequences. Snails and trematodes were examined from 11 collection sites representing three regions on the South Island of New Zealand. Zeacumantus subcarinatus displayed low genetic diversity per geographic locality, strong genetic structure following an isolation by distance pattern, and low migration rates at the scale of the study. In contrast, M. novaezealandensis possessed high genetic diversity, genetic homogeneity among collection sites and high migration rates. Genetic diversity and migration rates were typically lower for Philophthalmus sp. compared to M. novaezealandensis and it displayed weak to moderate genetic structure. The observed patterns likely result from the limited dispersal ability of the direct developing snail and the utilization of bird definitive hosts by the trematodes. In addition, snails may occasionally experience long‐distance dispersal. Discrepancies between trematode species may result from differences in their effective population sizes and/or life history traits.

Variation at Innate Immunity Toll-Like Receptor Genes in a Bottlenecked Population of a New Zealand Robin

Toll-like receptors (TLRs) are an ancient family of genes encoding transmembrane proteins that bind pathogen-specific molecules and initiate both innate and adaptive aspects of the immune response. Our goal was to determine whether these genes show sufficient genetic diversity in a bottlenecked population to be a useful addition or alternative to the more commonly employed major histocompatibility complex (MHC) genotyping in a conservation genetics context. We amplified all known avian TLR genes in a severely bottlenecked population of New Zealands Stewart Island robin (Petroica australis rakiura), for which reduced microsatellite diversity was previously observed. We genotyped 17–24 birds from a reintroduced island population (including the 12 founders) for nine genes, seven of which were polymorphic. We observed a total of 24 single-nucleotide polymorphisms overall, 15 of which were non-synonymous, representing up to five amino-acid variants at a locus. One locus (TLR1LB) showed evidence of past directional selection. Results also confirmed a passerine duplication of TLR7. The levels of TLR diversity that we observe are sufficient to justify their further use in addressing conservation genetic questions, even in bottlenecked populations.

Identification of a hybrid zone between distinctive colour variants of the alpine weta Hemideina maori (Orthoptera: Stenopelmatidae) on the Rock and Pillar range, southern New Zealand

The weta Hemideina maori occurs as yellow (to the north), black (to the south) and intermediate colour variants on the Rock and Pillar range in New Zealand. Isozyme electrophoresis revealed little genetic variation, whereas RFLP analysis of an amplified mtDNA sequence uncovered two haplotypes correlating completely with colour in allopatry and nearly so in sympatry. Intermediates had one or other haplotype. The observed distribution of colour variation and mtDNA genotypes is characteristic of a hybrid zone, perhaps formed by secondary contact. Work is continuing to locate nuclear DNA markers and to study the genetic interactions of the colour variants.

Effects of interspecific competition on asexual proliferation and clonal genetic diversity in larval trematode infections of snails

Interactions among different parasite species within hosts can be important factors shaping the evolution of parasite and host populations. Within snail hosts, antagonistic interactions among trematode species, such as competition and predation, can influence parasite abundance and diversity. In the present study we examined the strength of antagonistic interactions between 2 marine trematodes (Maritrema novaezealandensis and Philophthalmus sp.) in naturally infected Zeacumantus subcarinatus snails. We found approximately the same number of snails harbouring both species as would be expected by chance given the prevalence of each. However, snails infected with only M. novaezealandensis and snails with M. novaezealandensis and Philophthalmus sp. co-occurring were smaller than snails harbouring only Philophthalmus sp. In addition, the number of Philophthalmus sp. rediae was not affected by the presence of M. novaezealandensis sporocysts and the within-host clonal diversity of M. novaezealandensis was not influenced by the presence of Philophthalmus sp. Our results suggest that antagonistic interactions may not be a major force influencing the evolution of these trematodes and that characteristics such as host size and parasite infection longevity are shaping their abundance and population dynamics.

Isolation and characterization of microsatellite loci from the endangered New Zealand takahe (Gruiformes; Rallidae; Porphyrio hochstetteri)

Nineteen polymorphic microsatellite loci were characterized from the endangered takahe (Porphyrio hochstetteri). Like many of New Zealands other native avian species, levels of polymorphism were low, with variation detected at only 19 of 110 (17.3%) loci, and most polymorphic loci (78.9%) were diallelic (mean number of alleles = 2.3). Despite these low levels of variation, the microsatellites developed here will be useful for parentage assignment for confirming pedigrees, and investigating relationships between genetic variation, pedigree‐based inbreeding and reproductive success in this highly endangered species.

Phylogeographic genetic analysis of the alpine weta, Hemideina maori: evolution of a colour polymorphism and origins of a hybrid zone

Abstract Body colour is an important distinguishing feature in a New Zealand alpine weta hybrid zone and is strongly correlated with mitochondrial DNA haplotype variation. To assess the broader geographic pattern of this association, an intraspecific phylogeny was generated using mtDNA sequence. Both parsimony and likelihood analyses separated the colour morphs into two clades. One grouped the Rock and Pillar Range “yellow” haplotypes with other Central Otago populations and the other grouped the “black” Rock and Pillar haplotypes as a monophyletic group. The black body colour seen in the south of the Rock and Pillar Range appears to have evolved multiple times across the species. Application of a molecular clock estimated that the Rock and Pillar yellow and black lineages were separated approximately 2 million years ago. The Rock and Pillar yellow lineage split from other Central Otago populations approximately 1 million years later, possibly the result of sequential range contraction and expansion.

The influence of clonal diversity and intensity-dependence on trematode infections in an amphipod

Individual animals are often infected not only by different parasite species, but also by multiple genotypes of the same parasite species. Genetic relatedness among parasites sharing a host is expected to modulate their strategies of resource exploitation, growth and virulence. We experimentally examined the effects that genetic diversity and infection intensity had on host mortality, infectivity and growth of the marine trematode Maritrema novaezealandensis in amphipod hosts. The presence of 2 versus 1 parasite genotype during infection did not influence subsequent host mortality, had different effects on infectivity among genotypes and did not influence growth or variation in parasite growth. Density-dependent growth reductions revealed that the number of parasites infecting a host was more important than their genetic relatedness. Temperature, host size, and host sex influenced the degree to which density-dependent factors affected parasite growth. Our results suggest that the effects of parasite relatedness vary among parasite genotypes in this trematode species, and reveal that many factors play an important role during parasite development and transmission.

Isolation and characterization of microsatellite loci from the yellow‐eyed penguin (Megadyptes antipodes)

Twelve microsatellite loci were isolated and characterized in the endangered yellow‐eyed penguin (Megadyptes antipodes) using enriched genomic libraries. Polymorphic loci revealed two to eight alleles per locus and observed heterozygosity ranged from 0.21 to 0.77. These loci will be suitable for assessing current and historical patterns of genetic variability in yellow‐eyed penguins.