Graduation date: 1987

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / Includes bibliographical references.

Until recently most sandy beach studies have made use of snapshot samples but the validity of this approach has been widely questioned. In this study we attempt to resolve this issue by repeatedly sampling two beaches using a stratified random design. Three sampling sessions took place, each approximately six months apart. The three sites on the first beach were selected according to the type of beach (reflective, intermediate and dissipative) with each morphological type duplicated on the second beach. Many of the physical variables measured had significant differences between the sampling sessions but only a few were significantly different between the Sites. Very few of the individual physical variables had significant relationships with the sandy beach macrofaunal abundance and density. However, composite indices had a greater number of significant relationships with the macrofaunal abundance and density. Also very few significant relationships were seen between the species richness and the physical variables of the beaches studied. Effluent line crossing frequency was the only physical variable that could predict species richness but it was considered a weak predictor. Changes in the zonation patterns within and between beaches were also investigated. The highest concentration of taxa and individuals was found near the low-water mark with a gradual reduction of both towards the high-water mark. Some of the sandy beach community variables (abundance, density and species richness) showed significant difference between the sampling sessions but no significant differences were seen between the two beaches. The presence of three zones was noted using MDS plots and Cluster diagrams. However, using a SIMPER analyses, four zones with the possibility of a fifth was noted.

Field experiments and observations were used to define the functional roles and relationships of species in the rocky mid-intertidal community at Pelican Point in the northern Gulf of California. This approach provided resolution of the influences of grazing, predation, competition, and abiotic factors on community structure, and of the direct and indirect effects involved in species interactions. Competition for space, apparently via space pre-emption, between the barnacle Chthamalus anisopoma and encrusting algae of the genus Ralfsia was consistently evident. Grazing by the limpet Collisella strongiana was shown to limit algal abundance and bring about the replacement of Ralfsia by Chthamalus. Chthamalus also excluded Collisella from the rock surface. Predation on Chthamalus by the thaidid gastropod Acanthina angelica increased the abundances of both Ralfsia and Collisella. Some of the temporal variations in community structure observed during this study were clearly linked to variations in the abundances of Acanthina and Collisella and the above interactions. This relatively simple community, existing in what seems a rigorous physical environment, was characterized by strong, highly interdependent biological interactions. Indirect effects were consistently important in species interactions. An intriguing result of this study was the emergence of indirect mutualism between Acanthina and Collisella; this interaction appears to contribute to the persistence and continuing influences of both consumer species, and hence may be of major importance in the organization of this community. The zonation of the barnacles Chthamalus anisopoma and Tetraclita stalactifera at Pelican Point and elsewhere in the Gulf was examined in a test of recent ideas relating ecological and evolutionary patterns in barnacles to morphology and competition for space. Experiments and observations indicated the restriction of Tetraclita to the upper part of the shore by competition from Chthamalus, with Tetraclita able to survive above Chthamalus by virtue of greater tolerance to exposure. These results were in direct opposition to the presumed competitive dominance of large, rapidly-growing, tubiferous barnacles like Tetraclita. Comparisons with results from other shores suggested that numerical dominance goes hand-in-hand with competitive dominance in acorn barnacles. Morphological differences appear to be of minor importance.

The <i>Jaera albifrons </i>species group of intertidal isopods is characterised by strong sexual isolation mediated by female discrimination against heterospecific male tactile-stimulatory courtship behaviour.  This is the first study to examine the genetic basis of traits involved in tactile mediated sexual isolation.  To determine the genetic architecture of male secondary sexual characters (species-specific hair traits carried on the legs of males and a carpus leg-segment shape difference) associated with sexual isolation, experimental hybrid populations of <i>J. albifrons </i>and <i>J. ischiosetosa </i>were used to construct AFLP-based genetic linkage maps.  A number of chromosomal differences (Robertsonian fusions) between the parental species were shown to be associated with reduced hybrid fertility.  A quantitative trait locus (QTL) mapping study revealed that the number of hairs and carpus shape have a complex genetic basis, involving a number of QTL showing dominance, epistasis and possible pleiotropic effects.  These QTL mapped largely to putative regions of restricted recombination, especially chromosomal rearrangements. The qualitative difference, however, was shown to be controlled by a single (or several closely linked ) QTL that did not map to a region of restricted recombination.  These findings suggest that introgressive hybridisation played an important role in speciation in the <i>J. albifrons </i>species group and that chromosomal rearrangements allowed incipient species to persist in the face of ongoing gene flow.  The extensive sharing of a single 16S rDNA mitochondrial haplotype supports the assertion that gene flow has been important.  The reinforcement of premating isolating by natural selection against costly hybridisation is suggested as the mechanism of speciation between these species.  The complete dominance of the <i>J. albifrons </i>allele at the QTL controlling the qualitative difference between the species supports this model of speciation.

Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Melbourne, 1972. / Includes appendices. Includes bibliographical references (p. 243-263).

Thesis (M.A.)--Central Connecticut State University, 1997. / Thesis advisor: Dr. Kim A. Wilson. " ... in partial fulfillment of the requirements for the degree of Master of Arts in Biology." Includes bibliographical references (leaves 47-56).

Thesis (M. Sc.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 144-164.

Swan Bay is a shallow marine embayment of Port Phillip Bay, just north of Queenscliff, Victoria. It has been part of the Harold Holt Marine Reserves since 1977 and is a seagrass habitat. This study investigated the species of fish present in the inter-tidal zone of Swan Bay, collected information on their ecology, investigated the importance of Swan Bay compared to Port Phillip Bay as a nursery and/or breeding area and compared these results with those of similar seagrsss habitats. Field work was carried out monthly over a two year period, from April 1981 to April 1983, using beach seine nets at Swan Bay and Portarlington. Forty four species of fish were identified from Swan Bay and nineteen from Portarlington. Fish were most abundant during the summer and autumn months when seagrass growth was at a maximum and least abundant during winter due to the absence of seasonal residents and decreased numbers of permanent residents. Swan Bay was found to be an important nursery ground for two commercially-caught species: the Yellow-eye Mullet and the King George Whiting. Juvenile Yellow-eye Mullet were more numerous in Swan Bay than at Portarlington. Smell juvenile King George Whiting were more abundant at Portarlington than in Swan Bay where older juveniles were more numerous. The fish fauna of Swan Bay was found to be similar to western Port but the abundance of species varied. Atherinosome microstoma was the dominant species in terms of abundance and biomass. Diet was found to be different from that reported by Robertson (1979) at Western Port due to the different range of prey items.