<p> The impact of beach access paths on dune vegetation was investigated on the Isle of Palms, SC. Understanding the impacts of the most direct form of disturbance in this system (beach access paths) is of increasing importance from ecological and economic perspectives. Vegetation characteristics were measured along transects in foredune, mid dune and back dune communities at set distances from beach access paths. Survey was conducted to allow comparisons between path types and materials. Results indicate that beach access paths have a significant impact on beach dune vegetation. Sand paths cause greater reductions in vegetative cover than wooden paths and wooden paths raised at least 0.7m from the sand surface cause the least reduction in vegetation cover. Closely spaced paths reduce the species richness and percent of vegetative cover more than paths spaced at least 40 m apart. Current regulations can be minimally altered to improve dune vegetation and dune stability. Regulations requiring construction of raised wooden paths and disallowing private sand paths would greatly improve dune vegetation continuity. Additionally, voluntary path sharing of neighboring properties could significantly reduce the number of paths per mile of coastline while creating minimal inconvenience for beachfront homeowners and visitors.</p>

<p> This research aimed to determine whether wood microsites ("nurse logs"), which are regeneration sites in Pacific Northwest (PNW) subalpine forests, supported regeneration at timberline-alpine meadow borders. Upward advance of forests and conifer invasion into alpine meadows, which may be occurring in conjunction with climate warming, have gained worldwide attention. Successful alpine meadow seedling regeneration depends on suitable substrate availability, or microsites, for seedling establishment. To better understand factors associated with wood microsite occurrence, mechanisms of wood input were determined and four specific hypotheses were posed to assess: (1) seedling density and seedling survival; (2) growing season length, summer mean growing temperature, and growing degree hours (GDH); (3) active measures of seedling growth; and (4) global wood microsite climate associations. Of four studies, three were conducted in the Cascade Mountains of Washington state along a west - east precipitation gradient and one study, assessed various microsites globally. For Cascades-related research, wood and adjacent soil substrate temperature, moisture, and associated seedling density, survival, stomatal conductance, water potential, and leaf nitrogen were compared by percent transmitted radiation at 4 to 14 study sites. Analysis of variance (ANOVA), t-tests, regressions, and classification and regression trees (CARTs) were used to assess significance of comparisons. Wood microsites, common at 13 of 14 random Cascade sites, had greater seedling densities, greater seedling survival, greater volumetric moisture content (VWC), greater temperature, and greater number of GDH, as compared to adjacent soils. Greater seedling densities were positively associated with VWC (> 12%), conditions most commonly associated with wood substrate presence. For sites having > 25% percent transmitted radiation, positive relationships existed between stomatal conductance and VWC. Globally, high-elevation forests with wood microsites had mean annual precipitation from 86 cm to 320 cm and mean annual temperatures from 1.5&deg;C to 4.7&deg;C. In general, wood microsites facilitated alpine meadow regeneration better than adjacent soils. Management implications included enhanced understanding of factors associated with upward forest advance and wood use for restoration. Globally, wood microsites importance is likely underrepresented. Wood microsites role with warming climate will depend on precipitation pattern, timing, magnitude, and frequency.</p>

I examined biting, grooming, and inspection behavior in a pre-emergent colony of Parachartergus colobopterus, a neotropical swarm-founding wasp, to determine whether kin discrimination occurs between adult colony members. If within-colony kin discrimination exists, this is a likely place to find it. Low relatedness among colony members at some points in the colony cycle reduces advantages of nestmate discrimination and increases possible advantages of within-colony kin discrimination. I found no evidence of kin discrimination in length or frequency of biting and grooming interactions. Furthermore, interactants in biting, inspection, and grooming interactions were no more or less related than by chance. Results suggest that members of the species P. colobopterus do not identify and preferentially aid closer kin within a colony.

Why do females across a wide range of taxa mate with more than one male? Here, I present the hypothesis that females engage in polyandry as a hedge against genetic incompatibility. I review evidence from the literature showing that the genomes of species are dynamic entities, constantly evolving as a consequence of genetic conflicts within and between the nucleus and the cytoplasm. Cellular endosymbionts, segregation distorter alleles, transposable elements and genomically-imprinted genes can all threaten female fitness by modifying maternal and paternal haplotypes in ways that render them incompatible within the developing embryo. I discuss the potential for polyandrous females to utilize postcopulatory mechanisms such as sperm competition, female choice of sperm, and reallocation of maternal resources from defective to viable embryos in order to minimize the risk and/or cost of fertilization by genetically-incompatible sperm. In a sperm precedence experiment carried out on the pseudoscorpion, Cordylochernes scorpioides, single-locus minisatellite DNA fingerprinting demonstrated strong last-male sperm precedence when females were mated to two males which broke down completely when females were mated to three males. This result indicates that the opportunity for postcopulatory sexual selection may be much greater in nature than is evident from standard, laboratory, two-male mating experiments. Polyandry in this pseudoscorpion is shown to be a deliberate strategy which increases reproductive success. In laboratory experiments, females restricted to mating with a single male experienced a higher rate of embryo failure and produced significantly fewer offspring than either females mated to more than one male in the laboratory or females naturally inseminated in the field. Previously proposed hypotheses such as forced copulation, insufficient sperm from a single mating, male nutrient donations, offspring genetic diversity and inherent male genetic quality cannot explain this higher reproductive success of polyandrous females. Observations of meiotic drive, highly-skewed sex ratios and paternal effects on sex ratio in this pseudoscorpion are consistent with the hypothesis that, by accumulating sperm from several males, C. scorpioides females reduce the number of embryos which fail as a consequence of genetic incompatibility between maternal and paternal genomes.

The prairie and bordering woodlands of the Armand Bayou Nature Center, Harris County, Texas were sampled as an example of Texas Upper Coastal Prairie. The prairie is homogeneous and species-rich but shows very low dominance. Paspalum plicatulum, Dichanthelium spp., Carex cherokeensis, Andropogon virginicus, and Schizachyrium scoparium are the dominant graminoids. This prairie resembles the typical Upper Coastal Prairie of Texas but contains a greater number of eastern species with few southern or southwestern influences. Baccharis halimifolia has invaded the prairie and prairie climax species are no longer dominant. There is little evidence of a reduction in diversity due to brush encroachment. The woodlands are an oak and elm dominated riparian forest of the Upper Coastal Prairie with an important shrub component. Quercus phellos, Q. falcata, Ulmus americana, U. alata and U. crassifolia are common canopy species. Ilex vomitoria, Viburnum dentata, Callicarpa americana and Ligustrum sinense are the dominant shrubs.

In social insect colonies workers realize their reproductive potential through rearing the queen's brood. In the primitively eusocial wasp Polistes exclamans (Hymenoptera: Vespidae) castes are not morphologically distinct. This species has an annual colony cycle that begins when mated, hibernated females start colonies in the spring. One foundress becomes the queen while the rest become workers. The worker population grows throughout the year until the appearance of gynes, females that do not work but become foundresses the following spring. Males are also produced by the end of the season, but they die in winter with the workers. While morphological caste differences are absent, caste can be identified using behavioral and physiological parameters. In contrast with other social insects, female caste remains undetermined until adulthood, and even then females switch between castes under the appropriate circumstances. This can be advantageous since high nest predation rates and unpredictable environmental variation, accompanied by frequent queen supersedure are typical. I studied three aspects of the P. exclamans caste system: (i) morphology and physiology in gynes and workers; (ii) seasonal resource allocation into brood and (iii) effects of brood loss on caste determination. Physiological indicators were derived from qualitative and quantitative studies of biochemical components, and from measurements of metabolic rates. I show that differences between castes are mostly quantitative, rather than qualitative. I suggest that lack of physical and qualitative differentiation is what allows caste transitions. Seasonal resource allocation on brood shows that while young, adult females produced throughout the season increase in weight and size, energy reserves lipids peak in May and June. I suggest that this peak in reserves is related to high predation experienced by colonies during that time and that it allows females to reconstruct their nests more efficiently. Finally, I examine effects of loss of brood in late summer and early fall colonies showing that females that do not have the opportunity to care for brood develop gyne-like characters, but that females that have develop worker-like characters. These results show that caste in P. exclamans is plastic, behaviorally and physiologically, allowing individuals to respond to varying environmental and social conditions.

A mixed pine-oak stand in the Turkey Creek Unit of the Big Thicket National Preserve was logged in 1929-1930 and has experienced no fires since at least 1974. Stand basal area, density, and species richness increased from 1980-1993. A stage projection of the longleaf pine population at the site indicates the population will slowly decline ($\lambda$ = 0.9957) after an initial increase in population size as the population approaches stable size class distribution. Survivorship in the largest size class, 50+ cm dbh, had the largest effect on the outcome. Variations on the base model with potential stronger negative effects from fire suppression reduced $\lambda$ only slightly. Alternatively, small changes in demographic characteristics reflecting positive effects of fire raised $\lambda$ above 1.00. The modeling results suggest that the population is resilient to long-term unfavorable conditions because of the longevity of individual trees.

The housefly, Musca domestica, was used to test the short-term and long-term environmental effects of high population density. The first phase addresses the issue that there are two main selection forces that drive mating behavior, inter- and intrasexual selection. In intersexual selection the females are actively discriminating when choosing a mate and, thus, these male-female interactions are what predominantly define that population. However, in intrasexual selection, males potentially compete against each other over the pool of receptive females. I tested the hypothesis that a less complex courtship would be optimal in a high-density environment, short-term (i.e., one generation). Specifically, I videotaped the mating behavior of individuals subjected to one of two treatments: high-density or low-density (i.e., 200 virgin male-female pairs in a 2 L or 114 L cage, respectively). In both treatments, the flies were allowed to mate for 30 minutes while being videotaped. The proportion of time spent in three male courtship behaviors (HOLD, FORWARD, BUZZ) and one female courtship behavior (WINGOUT) were determined. I found that the mating propensity (percent of mated pairs) was significantly greater in the high-density environment. The courtships in the high-density environment were also significantly less complex (i.e., less FORWARD, less HOLD). My findings suggest that high-density environments stimulated competition among males causing the intrasexual selection processes to outweigh the intersexual processes. The second phase tests the prediction that long-term (i.e., eight generations), high population density will drive the evolution of courtship repertoire towards decreased complexity. I applied the previously outlined methods. Additionally, only those pairs that mated within the allotted time were allowed to contribute to the following generation. The courtship behavior assays suggest that the synergistic effects of high density on the males and inbreeding depression drove the evolution of increased courtship complexity and exaggerated inbreeding depression, therefore, not supporting the prediction or the results of first phase. In the low-density treatment, courtship became less complex and mating propensity increased. These results are applicable to populations with unnaturally high densities and potential for inbreeding such as those in laboratory agricultural pest control, and conservation projects.

Although social hymenopteran colonies show a high level of cooperation among their members, colony members can have conflicts among themselves as well. One of these intra-colonial conflicts is who produces the males. I studied the resolution of conflict in stingless bees, a species-rich group with a tropical distribution. In the majority of stingless bee species both workers and queens are able to produce males. Therefore intracolonial conflict over male production is predicted. Because stingless bee queens mate only once, workers are more related to their own and to each other's sons than to the sons of the queen. Thus on genetic grounds, worker production of males is expected. However, workers might not reproduce if the costs of reproduction are high, or if the queen is able to suppress workers. The decision could have been made in the bygone times and the current pattern does not serve adaptive functions at the present. To test my predictions of conflict over male production I looked at three levels: within colonies, within species, and between species. On the colony and species level, I hypothesized that current conflict is expressed by behavioral antagonism between the workers and their queen. Furthermore, I predicted behavioral conflict to be higher in the periods when males are produced compared to periods with only female production. On the level of comparison between species I expected more signs of conflict in species where both workers and queen produce males than in species where males are all queen derived. The conclusions of this study concerning conflict over male production in stingless bees are: (1) Genetic tools confirmed that workers reproduce in some, but not in other species. (2) The costs involved with worker reproduction could explain why in some species workers reproduce and in others not. (3) There is not only a variance of worker reproduction between, but also within species. Demographical factors might be essential determining the amount of worker reproduction within species. (4) The pattern of worker reproduction could be explained by costs although phylogenetic relationships could explain the pattern also.

A large seasonal variation in methane emission from Texas rice fields was observed in most of the growing seasons from 1989 through 1997. In general, the pattern showed small fluxes in the early season of cultivation and reached maximum at post-heading time, then declined and stopped after fields were drained. The amount of methane emission positively relates to the aboveground biomass, the number of effective stems and tillers, and nitrogen addition. The day-to-day pattern of methane emissions was similar among all cultivars. The seasonal total methane emission shows a significant positive correlation with post-heading plant height. The total methane emission from Texas rice fields was estimated as 33.25 x 109 g in 1993, ranging from 25.85 x 109 g/yr to 40.65 x 109 g/yr. A mitigation technique was developed to obtain both high yield and less methane emission from Texas rice fields. A new approach was also developed to evaluate regional to large-scale methane emission from irrigated rice paddies. By combining modeling, ground truth information and remote sensing into a Geographic Information System (GIS)---a computer based system, the seasonal methane emission from a large area can be calculated efficiently and more accurately. The methodology was tested at the Richmond Irrigation District (RID) site in Texas. The average daily methane emission varied from field to field and even within a single field. The calculated seasonal total methane emission from RID rice fields was as low as 3.34 x 108 g CH4 in 1996 and as high as 7.80 x 108 g CH4 in 1998. To support the application of the estimation method in a worldwide study, an algorithm describing the mapping of irrigated rice paddies from Landsat TM data was demonstrated. The accuracy in 1998-supervised classification approached 95% when cloud cover was taken into account. Model uncertainty and data availability are the two major potential problems in worldwide application of the new approach. A potential alternative model is proposed which allows estimation of regional methane emission from rice plant height.