No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Seagrasses are submerged marine plants that provide essential ecosystem functions, but are declining in abundance worldwide. As angiosperms, seagrasses are capable of sexual reproduction, but also propagate asexually through clonal rhizome growth. Clonal growth was traditionally considered the primary means for seagrass propagation. Recent developments in genetic techniques and an increasing number of studies examining seagrass population genetics, however, indicate that sexual reproduction is important for bed establishment and maintenance. Few studies have investigated the reproductive biology and ecology of sub-tropical seagrass species, although this information is necessary for effective management and restoration. This work investigates the influence of pore-water nutrients on flowering, water flow on seed dispersal, consumption on seed survival, and describes the reproductive phenology in Texas for the two dominant seagrass species in the Gulf of Mexico: turtle grass (Thalassia testudinum) and shoal grass (Halodule wrightii). These species exhibit distinctive reproductive seasons that span summertime months, but reproductive output varies spatially and temporally. Results of an in situ nutrient enrichment experiment indicate that turtle grass produces fewer flowers (but more somatic tissue) when exposed to high pore-water ammonium than when exposed to low pore-water ammonium, suggesting that nutrient loading has the potential to reduce seagrass reproductive output. Seed consumption may also limit reproduction and recruitment in some areas, as laboratory feeding experiments show that several local crustaceans consume shoal grass and turtle grass seeds and seedlings, which do not survive consumption. Dispersal experiments indicate that seed movement along the substrate depends on local water flow conditions, is greater for turtle grass than shoal grass, and is related to seed morphology. Under normal water flow conditions in Texas, turtle grass secondary seedling dispersal is relatively minimal (< 2.1 m d⁻¹) compared to primary dispersal, which can be on the order of kilometers, and shoal grass secondary seed dispersal can be up to 1.1 m d⁻¹, but seeds are likely retained in the parent meadow. Results from this work can be used when developing seagrass management, conservation and restoration actions and provide necessary information concerning a life history stage whose importance was historically under-recognized. / text

This thesis examines whether scramble competition is associated with social learning. The question is explored via a comparative study involving two species of grassfinches, Amadina fasciata, and Taenopygia guttata. These finches vary in the degree to which they employ scramble competition while foraging, but are otherwise similar behaviourally and morphologically. General problems associated with the application of the comparative method to the testing of learning specializations are discussed. Functional improvements to previously employed approaches are proposed, and then implemented in a novel methodology and statistical approach to analysing the data, the Manova approach. The results of the study suggest that there is no link between scramble competition and social learning in these two species. When the effects of confounding variables are removed from the interspecific comparison, the species do not appear to differ in their social learning abilities. The results also indirectly suggest that some forms of social learning occur through the mechanisms of general learning.

This study examined the effect of density on rhizome bud production in quackgrass (Elytrigia repens (L.) Nevski). The treatments consisted of two biotypes (L8 and L9), and nine density levels ranging from 1 to 22 plants m$ sp{-2}$. The results showed that bud production per plant diminished with increasing density in both biotypes. However, biotype L8 was less productive at low densities, but almost equal to L9 at higher densities. A second experiment was undertaken to measure the expansion of clonal colonies and the distribution of shoots within these colonies. For both biotypes the growth rate was highest in late summer and early fall, but colonies of L9 grew more rapidly. Biotype L9 had 59% of its total biomass located within 40 cm of the centre as compared with 81% in L8. Overall, Biotype L9 produced more rhizome buds, responded more strongly to intraspecific interference, and grew more rapidly as a colony.

Grass pickerel were collected in rivers and streams throughout Indiana for diet analysis. Frequency of occurrence, mean percent volume, and relative importance index were calculated for diet from all grass pickerel stomachs containing food. Grass pickerel were divided into three size classes (57-95mm, 96-150mm, >150mm) and stomach contents were divided into four groups (insects, fish, crayfish, and other). Grass pickerel in the small size class consumed mostly fish and crayfish while in the largest size class mostly crayfish were ingested. In addition, habitat selection was identified for grass pickerel. Macro and microhabitat were evaluated and described using the Qualitative Habitat Evaluation Index and visual assessment. Grass pickerel selected habitat with slow moving water and instream cover of either logs/woody debris or aquatic macrophytes. / Department of Biology