Search

The relationship between species diversity and environmental parameters is poorly understood for the mobile macrofauna of deep-sea habitats due to under-sampling and subsequent lack of accurate taxonomic information. To redress this, cytochrome oxidase c subunit I (COI) DNA sequences were used to estimate species diversity and to compare phoxocephalid amphipod assemblages among 20 stations encompassing a range of environmental conditions. Two regions, east (Chatham Rise) and west (Challenger Plateau) of New Zealand were sampled to depths of 200-1200 m with an epibenthic sled. Using a comparison among identified morphospecies, we found a clear gap in sequence divergences between 6% and 13% and used a 6% threshold to designate molecular operational taxonomic units (MOTUs), as a surrogate to putative species. DNA sequences (n = 297) revealed high total diversity (n = 49 MOTUs), as well as high beta diversity (28 MOTUs found at single location only). Novel phoxocephalid MOTUs were found at most stations, especially on Challenger Plateau and the flanks of Chatham Rise. Analyses of interstation assemblages revealed a major split between regions, indicating minimal overlap in taxon distributions. A cluster of highly similar stations was identified, broadly distributed over the crest of Chatham Rise, in association with elevated food availability, probably resulting from higher surface productivity and relatively shallow depth. Accordingly, multivariate analysis revealed a strong correlation between phoxocephalid assemblages and food supply. This study highlights the value of molecular approaches, in particular COI sequences, for quantifying and comparing diversity in under-sampled and/or under-studied taxa., (© 2012 Blackwell Publishing Ltd.)

We used DNA barcoding to assess the diversity and distribution of New Zealand's groundwater amphipods and isopods (Crustacea) and to determine whether biodiversity and endemism within tectonically active New Zealand are similar to those of more tectonically stable continents. Sixty-five wells were sampled in seven aquifers across four regions within the North and South islands of New Zealand, and resident invertebrates were morphologically identified and then assessed using sequencing of the mitochondrial DNA cytochrome c oxidase subunit one (COI) gene. Invertebrates were found in 54 wells. Of the 228 individual amphipods and isopods found in 36 of the wells, 154 individuals were successfully sequenced for COI (68% success rate) from 25 wells, with at least one well in each aquifer containing sequenced individuals. Of the 45 putative species identified using Barcode Index Numbers (BINs), 30 BINs (78% of all taxa and 83% of amphipods) were previously unrecorded. Substantial morphologically cryptic, species-level diversity was revealed, particularly within the amphipod Family Paraleptamphopidae. Similarly, one isopod taxon morphologically identified as Cruregens fontanus was assigned to five well-separated BINs based on COI sequences. Endemism appeared high, with all taxa regionally endemic; 87% of species were restricted to one aquifer and more than 50% restricted to one well. Non-saturated species accumulation curves indicated that, while additional sampling may increase the range of some currently identified taxa, additional range-restricted taxa are also likely to be discovered. Patterns of diversity and short-range endemism were similar to those found elsewhere, including locations which are more tectonically stable. The predominance of local endemism within New Zealand's groundwater fauna suggests that land-use activities and groundwater extraction require careful evaluation to minimize threats to groundwater biodiversity. [ABSTRACT FROM AUTHOR]

We examined the phylogeographic patterns of Paracalliope fluviatilis (Amphipoda) over its entire range and the prevalence of mate discrimination in laboratory mate choice tests using genetically distinct populations. We predicted that mate discrimination would increase as the level of genetic divergence increased between populations. Thirty different haplotypes were found with pairwise sequence divergences in the range 1–23.5% between locations. Individuals were selected from seven genetically distinct populations and males were presented with ‘local’ (same population) or ‘foreign’ (genetically divergent) females. Males were more likely to pair with local than foreign females but there was no evidence of a gradual increase in discrimination. Discrimination became most prominent (approximately 5 : 1 local : foreign) when genetic divergences exceeded approximately 20%; matings between divergent individuals also resulted in significantly fewer females producing eggs. We suggest that: (1) this abrupt shift in discrimination occurs because individuals from different, but similarly divergent, clades rely on different recognition cues (e.g. moulting pheromones with disparate chemical signatures) that trigger recognition and subsequent discrimination of incompatible mates; (2) geological history associated with sea level changes and a series of isolation events may be responsible for the patterns of discrimination that we observed; and (3) amphipods may be more genetically variable relative to other invertebrate taxa. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 196–205. [ABSTRACT FROM AUTHOR]

Field and laboratory studies were used to assess: (1) whether size assortative mating occurred in the New Zealand amphipod Paracalliope fluviatilis and (2) hypotheses developed to explain size assortative mating. We found that assortative mating occurred and that larger females carried more eggs, suggesting they may be more valuable as mates. Laboratory experiments were then used to determine whether: (1) male size influenced the size of the female selected (mechanical constraints hypothesis); (2) male size influenced pairing success in the presence of competition (intrasexual selection hypothesis); (3) take-overs of females occurred and whether large males were more successful (intrasexual selection hypothesis); (4) guard duration varied relative to male and female size (guard duration hypothesis); and (5) females had control over pairing success and guard duration (intersexual selection hypothesis). Although there was evidence to suggest the existence of intrasexual competition for mates (i.e. both small and large males preferred large females), there was no evidence of overt competition (i.e. takeovers of paired females). There was also no difference with respect to how long small and large males guarded females, but large females were guarded longer by both male size classes. Females handicapped by having their mobility reduced were guarded for the same duration as control females but males were more likely to pair with handicapped females, suggesting that they were easier to amplex. Given the lack of evidence for direct male–male competition or female choice, we suggest that assortative mating may be the result of: (1) indirect competition (e.g. in situ large males may be better able to access and amplex the largest females) or (2) female resistance to small males in combination with higher costs that small males may incur in securing large females. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92, 173–181. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the distribution and dispersal of corophiid amphipods (Paracorophium spp.) in a temperate New Zealand estuary. Individuals in the sediment (resident population) and those caught in bed-load (local-scale movement) and suspended-load (larger-scale movement) were counted, measured, and sexed, during two tidal cycles at 4–6 week intervals spanning 13 months. Gravid females and juveniles were present in the resident population on all sample dates suggesting near continuous reproduction. Juveniles (<2.2 mm body length) accounted for 49.8% of individuals in the sediment, compared to 65.4% of those caught in the bed-load and suspended-load traps. For the majority of sample dates, there was a net export of juveniles from the estuary. The total number of juveniles captured in suspended-load traps was significantly greater during the ebb tide relative to the flood tide (n =541 versus 256), whereas no significant differences were found for adults. Similarly, numbers in the bed-load traps were significantly greater for juveniles during the ebb versus the flood tide (n =900 versus 484), and also for adult females (n =180 versus 86). Juvenile sex ratios were female biased in the sediment (9.8:1) and in suspended-load traps (7.6:1) and both were significantly more female-biased than that recorded for juveniles caught in bed-load traps (5.8:1). By contrast, there was a significantly lower proportion of adult females to adult males found in bed-load traps (1.7:1) and in suspended-load traps (0.98:1) compared to the resident population in the sediment (3.6:1). The mean size of juvenile females caught on a flood tide was significantly larger compared to those on the ebb tide, yet juvenile males were not significantly different, suggesting that smaller females were not returning on the flood tide. We suggest that female-biased juvenile dispersal for estuarine Paracorophium spp. lowers the risk of inbreeding and reduces competition. This may have evolved in response to a polygamous breeding system with little or no social organisation where a female produces more female offspring to maximise her inclusive fitness. [Copyright &y& Elsevier]

1. We evaluated the population genetic structure of the common New Zealand amphipod Paracalliope fluviatilis using eight allozyme loci, and the mitochondrial cytochrome oxidase c subunit I (COI) gene locus. Morphological analyses were also conducted to evaluate any phenotypic differences. Individuals belonging to P. fluviatilis were collected from a total of 14 freshwater fluvial habitats on the North and South Islands, New Zealand. 2. We found evidence for strong genetic differentiation among locations (Wright's FST > 0.25), and fixed differences (non-shared alleles) at two of the eight allozyme loci indicating the possibility of previously unknown species. Analysis of a 545-bp fragment of the COI locus was mostly congruent with the allozyme data and revealed the same deeply divergent lineages (sequence divergences up to 26%). 3. Clear genetic breaks were identified between North Island and South Island populations. North Island populations separated by <100 km also showed genetic differences between east and west draining watersheds (sequence divergence >12%). Accordingly, present-day dispersal among hydrologically isolated habitats appears minimal for this taxon. 4. Although population differences were clearly shown by allozyme and mtDNA analyses, individuals were morphologically indistinguishable. This suggests that, as in North American and European taxa (e.g. Hyalella and Gammarus), morphological conservatism may be prevalent among New Zealand's freshwater amphipods. We conclude that molecular techniques, particularly the COI gene locus, may be powerful tools for resolving species that show no distinctive morphological differences. [ABSTRACT FROM AUTHOR]

Allozyme electrophoresis was used to examine population genetic structure at inter- and intraspecific levels for the New Zealand endemic corophiid amphipods, Paracorophium lucasi and P. excavatum. Individuals were collected from estuarine and freshwater habitats from North, South and Chatham Islands. Analyses of genetic structure among interspecific populations indicated clear allelic differentiation between the two Paracorophium species (Nei's genetic distance, D = 1.62), as well as considerable intraspecific substructuring ( D = 0.15–0.65). These levels of divergence are similar to interspecific levels for other amphipods and it is proposed that at least two groups from the P. lucasi complex and three from the P. excavatum complex correspond to sibling species. In most cases allopatry can account for the differentiation among the putative sibling species. For populations that share a common coastline we found low levels of differentiation and little or no correlation with geographical distance, suggesting that gene flow is adequate to maintain homogeneous population genetic structure. By contrast, populations on separate coastlines (i.e. isolated by land) showed moderate levels of geographical differentiation indicating restricted gene flow. The juxtaposition of population genetic and biogeographical data for Paracorophium in conjunction with the geological record infers past histories of glacial extirpation, and possible isolating effects of sea-level and landmass changes that have occurred throughout the Plio-Pleistocene. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 81, 119–133. [ABSTRACT FROM AUTHOR]

Intraspecific genetic differentiation reflects processes that underpin biodiversity in deep-sea habitats. We examined the spatial genetic structure of epibenthic amphipod taxa from upper bathyal depths (200–1200 m) along New Zealand's continental margins. Genetic variability in amphipods was assessed using cytochrome c oxidase I (COI) to characterise inter-regional diversity and phylogeographic patterns in the Chatham Rise and Challenger Plateau to the east and west of New Zealand, respectively. Automatic barcode gap discovery methods identified 263 MOTUs, of which 14 were detected in both regions. Population genetic analyses found contrasting patterns of diversity among different MOTUs within and between regions. Overall, a pattern of increasing genetic differentiation (K2P distances) with decreasing depth was observed between regions. Genetic differentiation was highest among MOTUs found at shallow depths, while taxa from deeper waters showed little evidence of divergence. Our results suggest that intraspecific genetic diversity is correlated with amphipod family traits, particularly dispersal abilities inferred from habitat preferences (infaunal, epibenthic or pelagic) and may also be linked to regional geological history. Such insights have important implications for regional-scale patterns of diversity associated with local processes in promoting differentiation among populations of bathyal amphipods on New Zealand's continental margins. • We collected amphipods from two bathyal regions off New Zealand. • We aimed to characterise inter-regional genetic diversity and phylogenetic patterns. • Genetic variability was assessed using cytochrome c oxidase I. • Intraspecific genetic differentiation between regions increased with decreasing depth. • Findings are linked to geological events and/or dispersal capacity of individual taxa. [ABSTRACT FROM AUTHOR]