Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

x, 97 p. : ill. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In all species of pycnogonids (sea spiders) males care exclusively for the offspring, making this group essential for studies on sex roles, sexual selection, and the evolution of parental investment. Unfortunately, little is known about pycnogonid mating patterns, larval development, or the costs associated with parental care. The mating habits of both male and female Achelia simplissima were studied experimentally and reveal that both sexes routinely mate multiple times and have multiple mates. Parental males experience higher frequencies of predator attacks and epibionts and a lower rate of movement as compared with nonparental males. However, parental males are harder to dislodge than nonparental males and suffer no change in feeding frequency as a result of parental care. The external morphology of the first larval stage of Achelia simplissima was described using SEM photos and compared with other larval pycnogonids. Morphological characteristics suggest a "parasitic" mode of postembryonic development. / Committee in Charge: Alan Shanks, Chair; Svetlana Maslakova; Craig Young

M.Sc. (Zoology) / Please refer to full text to view abstract

D.Sc. (Zoology) / Please refer to full text to view abstract

Lick Creek Park is a 515 acre nature park that was acquired in 1987 by the City of College Station, Texas. The site has a variety of indigenous plant and animal species and is an important natural resource for citizens of the region. There is a long-term commitment to inventory this natural park to monitor the changes as our urban community expands to surround the park. There are 989 species of spiders currently recorded from Texas and 332 of them are known to occur in Brazos County. My focus was on improving the ground spider inventory at Lick Creek Park. Spider collections were made using 18 regularly-sampled pitfall traps distributed evenly among three habitats. Spiders from 24 families, 66 genera, and 111 species were identified from 918 specimens, including 627 immature and 291 adult spiders, captured in pitfall traps from April 2005-April 2006. Of the 111 species found, 45 were represented by one specimen only and 20 were represented by two specimens. Rarefaction analyses indicated that the majority of spider species were readily detectable using pitfall traps and inventoried during this study (111 found and 168 estimated to be present). Simpson’s Diversity measure bootstrap estimates determined species diversity overall to be very diverse (0.966), as did a Shannon Weiner Diversity bootstrap estimate (5.483). Also, Simpson’s measure of species evenness (0.264) indicated a low species evenness. Those species found in only one habitat comprised 50% of the total species, and their densities ranged from 1-5 individuals. Those species found in just two habitats comprised 25% of the total species, and their densities ranged from 2-21 individuals. Species found in all three habitats comprised the remaining 25%, and their densities ranged from 4-53 individuals found. Most species occurred at low densities in this study and this often precluded conducting more detailed analyses. Additional sampling is expected to, first, detect known species occurring in previously unrecorded habitats and, second, to detect species not previously found in the park. This inventory of spiders at Lick Creek will provide a basis for further studies on biodiversity and the assessment of human impact on the environment.

Lick Creek Park is a 515 acre nature park that was acquired in 1987 by the City of College Station, Texas. The site has a variety of indigenous plant and animal species and is an important natural resource for citizens of the region. There is a long-term commitment to inventory this natural park to monitor the changes as our urban community expands to surround the park. There are 989 species of spiders currently recorded from Texas and 332 of them are known to occur in Brazos County. My focus was on improving the ground spider inventory at Lick Creek Park. Spider collections were made using 18 regularly-sampled pitfall traps distributed evenly among three habitats. Spiders from 24 families, 66 genera, and 111 species were identified from 918 specimens, including 627 immature and 291 adult spiders, captured in pitfall traps from April 2005-April 2006. Of the 111 species found, 45 were represented by one specimen only and 20 were represented by two specimens. Rarefaction analyses indicated that the majority of spider species were readily detectable using pitfall traps and inventoried during this study (111 found and 168 estimated to be present). Simpson’s Diversity measure bootstrap estimates determined species diversity overall to be very diverse (0.966), as did a Shannon Weiner Diversity bootstrap estimate (5.483). Also, Simpson’s measure of species evenness (0.264) indicated a low species evenness. Those species found in only one habitat comprised 50% of the total species, and their densities ranged from 1-5 individuals. Those species found in just two habitats comprised 25% of the total species, and their densities ranged from 2-21 individuals. Species found in all three habitats comprised the remaining 25%, and their densities ranged from 4-53 individuals found. Most species occurred at low densities in this study and this often precluded conducting more detailed analyses. Additional sampling is expected to, first, detect known species occurring in previously unrecorded habitats and, second, to detect species not previously found in the park. This inventory of spiders at Lick Creek will provide a basis for further studies on biodiversity and the assessment of human impact on the environment.

Stegodyphus mimosarum Pavesi,1883 and S. dumicola Pocock, 1898 are two species of philopatric, inbred, permanently communal, non-territorial spiders that co-occur in parts of South Africa. The patchiness of colony distribution, limited dispersal capabilities and the observation of periodic, but rare mass dispersal events raised interest in factors influencing dispersal. The aim of this project was firstly, to determine which factors influence the spiders' readiness to leave a colony (two laboratory experiments), and secondly, to map nest dispersion in Weenen Nature Reserve, Kwa-Zulu Natal, and to use this to explain nest distribution. The first experiment assessed whether group size and variance in access to resources influenced the decision to disperse. Four colony sizes (8, 16,32 and 64) of S. mimosarum were established under a proportional feeding regime. I expected more spiders to leave larger colonies due to intra-group competition. However, there was no significant increase in the number of spiders leaving with increasing group size. Significantly more spiders left a colony during spring and when spiders were large. In the second experiment, I assessed whether the mean amount of food available, in liberally fed or starved colonies influenced the decision to disperse. Five colonies were fed daily on an abundance of prey items and five were starved. I expected more spiders to leave the starved colonies. However, a significant number of spiders left colonies where food was abundant. During a field survey nests were tagged within 40 plots of 50 m radius, and randomly. Retreat dimensions, height above ground, nest position, nearest neighbouring nests, and species were recorded. Nest status was tracked over six months to three years. I confirmed that nest height above ground was significantly higher for S. mimosarum. The two species differed in retreat volume and nearest neighbour distances. Most nests occurred on the northern aspect of trees. Few nests survived beyond three years, although many new nests were established. Access to resources influenced the decision to disperse. However, only well-fed (larger) spiders had the resources to relocate. Patchy nest distribution could be a consequence of nest site selection, short distance dispersal by budding and bridging, and long distance dispersal by ballooning. / Thesis (M.Sc.)-University of Natal, Durban, 2002.

[Truncated abstract] The southern-temperate spider family Micropholcommatidae is a poorly-studied taxon of uncertain limits and uncertain affinities. Since the first Australian species were described in the early twentieth century, and the family was erected in 1944, the taxonomic status and phylogenetic placement of the Micropholcommatidae have been the subject of ongoing debate. Various phylogenetic hypotheses have been proposed for the family, but these hypotheses have never been tested with a robust phylogenetic analysis – a problem compounded by the inadequate state and confusing history of micropholcommatid taxonomy. To address the many gaps in our understanding of micropholcommatid interrelationships, this thesis will present a comprehensive systematic treatment of the family. Using a combination of molecular phylogenetic, morphological cladistic and taxonomic methods, micropholcommatid diversity is documented and tested at multiple systematic levels, with an alpha-taxonomic and biogeographic focus on the diverse Australian fauna. The taxonomic contribution is substantial throughout, with one new family, two new subfamilies, one new tribe, 14 new genera and 37 new species described. A combined molecular phylogenetic study is presented in Chapter 2, as a 'first pass' exploration of the monophyly, limits and phylogenetic position of the family Micropholcommatidae. The analyses incorporated 50 ingroup spider species, including 23 micropholcommatid taxa, with nucleotide sequences obtained from two nuclear ribosomal RNA genes (18S and 28S). ...The new subfamily Gigiellinae is also described for two enigmatic species in the newly-described genus Gigiella, known only from the temperate Nothofagus rainforests of south-eastern Australia and southern Chile. As a final contribution to micropholcommatid taxonomy, and as an extension to the cladistic analyses presented in Chapter 5, the new spider family Teutoniellidae is proposed in Chapter 6 for three genera from South America, South Africa and Australia. Teutoniellid monophyly is evidenced by at least two unambiguous synapomorphies, and the morphology of the family is described in relation to other symphytognathidan and EbCY spider taxa. The nominate genus Teutoniella is redescribed to include three species from South America, along with an additional new species from Tasmania. Two new teutoniellid genera are also described, each for a single new species from South Africa: Inflaticrus ansieae is described from the Langeberg Range, east of Cape Town; and Woldius hennigi is described from near Pietermaritzburg, north-west of Durban. In summary, this thesis provides a taxonomic and phylogenetic framework for all future research on micropholcommatid spiders. It presents new data on the phylogeny, phylogenetic position, composition, biogeography, molecular evolution and natural history of a previously poorly-known group of spiders, and highlights a number of remaining gaps in our knowledge of micropholcommatid and araneoid systematics. As a novel contribution to scholarship, this thesis synthesises taxonomic and phylogenetic hypotheses at multiple systematic levels, and tests those hypotheses with original, combined datasets.

External reproductive organs of spiders are often species-specific and are important taxonomic characters in species identification. One explanation of this phenomenon, the mechanical isolation hypothesis was tested in two Nuctenea (Araneidae) species. According to this hypothesis, a lock-and-key isolating mechanism should lead to character displacement (mechanical, ecological, or behavioral) between sympatric species with similar genitalia in order to prevent costly interspecific copulation attempts. Homologous external genitalia of male and female Nuctenea sclopetaria and N. patagiata were measured, The measurement means and variances were statistically compared to determine if character displacement was occurring between areas of sympatry and allopatry. Differences in both mean and variance were observed, but the number that differed between regions of sympatry and allopatry was not greater than the number that differed between adjacent regions of sympatry. Thus, these species failed to demonstrate the character displacement predicted by the mechanical isolation hypothesis. Data collected in the study were also used to test a hypothesis that spider genital features tend to be less variable than overall I size features, a hypothesis supported by an earlier study of the primitive spider Hypochilus. F-tests of coefficients of variation showed measurements of the Nuctenea genitalia to be more variable than first femur length. Differences in environmental pressures and genital complexity between Nuctenea and Hypochilus may explain this disparity. / Master of Science

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy