Light and scanning electron microscopy have been utilized to further resolve the taxonomic status of the genus Acanthopleura Guilding, 1829 (Mollusca: Polyplacophora) following Ferreira’s 1986 controversial revision, which synonymised four well-established genera and numerous species. Specimens of the 19 nominal species of the genus Acanthopleura, together with those from five widely disparate, geographic populations of one of these species (A. gemmata), along with specimens of the outgroup, Onithochiton quercinus Gould, 1846), have been utilised. A consideration of gross morphological characters, including features of the valves, girdle armature and gills, clearly separate A. rehderi from Acanthopleura, aligning it with Onithochiton. They also suggest the synonymy of two pairs of species (A. haddoni/A. vaillantii and A. testudo/A. brevispinosa), and indicate that A. loochooana is closely aligned with species previously assigned to Squamopleura (A. araucariana, A. curtisiana and A. miles). Examination of microstructural characters of the intermediate valve, including features of the tegmental micro architecture, the ocelli, the aesthetes and the central anterior eaves, confirm the conclusions of the gross morphological study, and, in addition, indicate a close relationship between A. echinata and A. nigra. Investigation of the girdle armature indicates that Acanthopleura can be divided into four groups based on the possession of predominantly scales, spines, spinelets or spicules. However, there is wide intraspecific variation with regard to micro architecture of the girdle elements. This section confirms the close relationships of A. haddoni/A. vaillantii and A. testudo/A. brevispinosa, and suggests affiliations between other species.

New Zealand is a continental island surrounded by deep-ocean, with a complex system of currents and oceanographic anomalies that may serve to isolate populations of coastal marine organisms. In particular Cook Strait is a 26 km wide body of water separating the North and South Islands which is characterised by complex interactions of tides and converging water masses. Cook Strait is a geologically recent formation that may also impart an historical influence on the biogeographic distribution of coastal marine taxa. In order to investigate the phylogeographic structure of coastal marine taxa around New Zealand's coastline and to investigate the processes that may contribute toward this genetic structure, I analysed mitochondrial DNA genes from limpet species of the Cellana genus. Phylogenetic analyses of the ribosomal 12S and 16S DNA genes showed that C. ornata may approximate the founding lineage to New Zealand, but these genes were unable to resolve between contrasting biogeographic hypotheses about the origin of Cellana in New Zealand. Intraspecific analyses of the mitochondrial cytochrome b gene from populations throughout the biogeographic range of Cellana ornata, C. radians and C. flava showed concordant genetic discontinuity at Cook Strait. Further analyses suggest that allopatric fragmentation and restricted gene flow have caused significant genetic differentiation between populations of the North and South Island. Demographic expansion was also identified for C. radians. The influence of contemporary nearshore currents and sea surface temperature was assessed using the mitochondrial cytochrome b gene for C. radians and C. ornata. Low levels of genetic differentiation between populations corresponding to 'current-zones' suggests that contemporary oceanic processes may be contributing to the genetic pattern observed for these species. However, the shallow divergence between haplotypes and populations restricted thorough investigation of contemporary gene flow. Genealogical concordance across co-distributed marine taxa of New Zealand also lends support to the historic association of genetic and species discontinuities with recent geological changes, such as sea level fluctuations.

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A total of 5065 specimens (5018 valves of bivalve and 47 gastropod shells) have been identified and classified into 27 species from 55 samples collected from raised glaciomarine and estuarine sediments, and glacial tills. The bivalves <i>Hiatella arctica</i>, <i>Mya truncate</i>, <i>Astarte borealis</i>, and <i>Serripes groenlandicus</i> are the most common species. Our samples record the dominance of infaunal suspension-feeders that are most abundant on soft substrates typically occurring in nearshore environments. The dominance of bivalves with respect to gastropods reflects an averaged record of the fossil assemblages inhabiting the high latitude nearshore environments. Six unique associations, which are comparable to the composition of modern communities inhabiting in fiords and on continental shelf from Canadian high arctic, and three distinctive taxa groups (deposit feeders, suspension-feeders, and rare taxa) are recognized by cluster analysis and Multidimensional Scaling conducted on presence-absence data. The trophic composition of paleocommunities in this study is as follows: suspension-feeders > deposit feeders > carnivores > browsers. The occurrence of <i>Mya pseudoarenaria</i> in fossil assemblages indicates an age of the fossils around early Holocene. <p>Most of the samples are not substantially transported nor significantly reworked. Shell disarticulation and fragmentation can result from sea ice scouring of the seafloor and the development of permafrost in raised marine sediments. The degree of shell disarticulation for the four most common taxa is generally low which likely reflects high sedimentation rates and rapid burial in nearshore environments, especially those from glaciomarine silts and estuarine deposits. Four common species exhibit different preservation potential based the degree of fragmentation and disarticulation (Serripes < Mya < Hiatella < Astarte). Shells with high (or low) degree of fragmentation for single species (i.e. Hiatella) also correspond to different energy conditions of the associated sediments facies from which the shells are recovered. The general absence of strongly bioeroded or encrusted shells among samples suggests rapid burial of the shells with only limited exposure on the sediment surface, or the absence of grazing, boring or encrusting taxa in the environment that is dominated by infaunal habit of most of the taxa represented in the shell assemblages. <p>Four taphofacies are recognized by cluster analysis on the basis of four taphonomic variables (fragmentation, corrasion, bioerosion, and encrustation) characterized by poor preservation, fair preservation, fair-good preservation, and fair preservation with poor corrasion respectively. Faunal succession and paleo-marine environments during the deglaciation in early Holocene are reconstructed from the seven sedimentation facies (glacial, beaches, shallow marine, proglacial, shallow marine or estuarine - pebbly sand and gravel with algal debris, shallow marine or estuarine - pebbly silt with algal debris, shallow marine or estuarine - interbedded silt and sand).

A total of 5065 specimens (5018 valves of bivalve and 47 gastropod shells) have been identified and classified into 27 species from 55 samples collected from raised glaciomarine and estuarine sediments, and glacial tills. The bivalves <i>Hiatella arctica</i>, <i>Mya truncate</i>, <i>Astarte borealis</i>, and <i>Serripes groenlandicus</i> are the most common species. Our samples record the dominance of infaunal suspension-feeders that are most abundant on soft substrates typically occurring in nearshore environments. The dominance of bivalves with respect to gastropods reflects an averaged record of the fossil assemblages inhabiting the high latitude nearshore environments. Six unique associations, which are comparable to the composition of modern communities inhabiting in fiords and on continental shelf from Canadian high arctic, and three distinctive taxa groups (deposit feeders, suspension-feeders, and rare taxa) are recognized by cluster analysis and Multidimensional Scaling conducted on presence-absence data. The trophic composition of paleocommunities in this study is as follows: suspension-feeders > deposit feeders > carnivores > browsers. The occurrence of <i>Mya pseudoarenaria</i> in fossil assemblages indicates an age of the fossils around early Holocene. <p>Most of the samples are not substantially transported nor significantly reworked. Shell disarticulation and fragmentation can result from sea ice scouring of the seafloor and the development of permafrost in raised marine sediments. The degree of shell disarticulation for the four most common taxa is generally low which likely reflects high sedimentation rates and rapid burial in nearshore environments, especially those from glaciomarine silts and estuarine deposits. Four common species exhibit different preservation potential based the degree of fragmentation and disarticulation (Serripes < Mya < Hiatella < Astarte). Shells with high (or low) degree of fragmentation for single species (i.e. Hiatella) also correspond to different energy conditions of the associated sediments facies from which the shells are recovered. The general absence of strongly bioeroded or encrusted shells among samples suggests rapid burial of the shells with only limited exposure on the sediment surface, or the absence of grazing, boring or encrusting taxa in the environment that is dominated by infaunal habit of most of the taxa represented in the shell assemblages. <p>Four taphofacies are recognized by cluster analysis on the basis of four taphonomic variables (fragmentation, corrasion, bioerosion, and encrustation) characterized by poor preservation, fair preservation, fair-good preservation, and fair preservation with poor corrasion respectively. Faunal succession and paleo-marine environments during the deglaciation in early Holocene are reconstructed from the seven sedimentation facies (glacial, beaches, shallow marine, proglacial, shallow marine or estuarine - pebbly sand and gravel with algal debris, shallow marine or estuarine - pebbly silt with algal debris, shallow marine or estuarine - interbedded silt and sand).

Six British species of the littoral prosobranch Littorina have been examined for genetic variability at between eight and twenty-five enzyme loci. The characteristics and levels of variability observed are similar to those observed in other taxa of similar somatic complexity. Attempts to relate patterns of variability with enzynle structure and function, or with bionomic strategies have shown no significant trends. A phylogenetic tree has been constructed and divergence times estimated for "five members of the genus. The advantages of the littoral environment, coupled with a poly-specific genus for examining models of evolution, has been discussed. L. rudis and L. littorea have been examined in detail at several sites along the coast of South Wales and variability in each species has been examined in terms of the physical separation and the ecological properties of the populations. Whilst L. littorea is homogeneous and probably effectively panmictic in South \vales, L. rudis shows a significant increase heterogeneity as populations become further separated, indicating substantial population isolation. A highly significant relationship between heterozygosity (gene-diversity) and species overlap has been found, neither of these characteristics could be related to exposure. In populations sampled at more than one tide level, the sample from the higher mark invariably showed the higher heterozygosity. Little relationship could be found between environmental parameters or heterozygosity and measures of morphological variation, however it was found that ~ average older L. rudis and L. littorea were more heterozygous than younger individuals. Heterozygotes show a lower variance than homozygotes for a meristic character, shell index, at some loci. The data havebeen examined for linkage disequilibrium. Information on some foreign populations is presented. The data are discussed in the light of modern evolutionary theory, and a balancing selection model for the maintenance of genetic variability is proposed.

New Zealand is a continental island surrounded by deep-ocean, with a complex system of currents and oceanographic anomalies that may serve to isolate populations of coastal marine organisms. In particular Cook Strait is a 26 km wide body of water separating the North and South Islands which is characterised by complex interactions of tides and converging water masses. Cook Strait is a geologically recent formation that may also impart an historical influence on the biogeographic distribution of coastal marine taxa. In order to investigate the phylogeographic structure of coastal marine taxa around New Zealand's coastline and to investigate the processes that may contribute toward this genetic structure, I analysed mitochondrial DNA genes from limpet species of the Cellana genus. Phylogenetic analyses of the ribosomal 12S and 16S DNA genes showed that C. ornata may approximate the founding lineage to New Zealand, but these genes were unable to resolve between contrasting biogeographic hypotheses about the origin of Cellana in New Zealand. Intraspecific analyses of the mitochondrial cytochrome b gene from populations throughout the biogeographic range of Cellana ornata, C. radians and C. flava showed concordant genetic discontinuity at Cook Strait. Further analyses suggest that allopatric fragmentation and restricted gene flow have caused significant genetic differentiation between populations of the North and South Island. Demographic expansion was also identified for C. radians. The influence of contemporary nearshore currents and sea surface temperature was assessed using the mitochondrial cytochrome b gene for C. radians and C. ornata. Low levels of genetic differentiation between populations corresponding to 'current-zones' suggests that contemporary oceanic processes may be contributing to the genetic pattern observed for these species. However, the shallow divergence between haplotypes and populations restricted thorough investigation of contemporary gene flow. Genealogical concordance across co-distributed marine taxa of New Zealand also lends support to the historic association of genetic and species discontinuities with recent geological changes, such as sea level fluctuations.