<p> Amphidromous species migrate between fresh water and the sea for larval development. Many caridean shrimps, especially <i>Macrobrachium </i> spp., are amphidromous, and some populations are found far-upstream within continental river systems. This project tested the hypothesis that populations of <i>Macrobrachium ohione</i> from the Atchafalaya and Mississippi Rivers are amphidromous. </p><p> In the laboratory, I tested the hypothesis that upstream populations of <i>M. ohione</i> have freshwater larval development. My results indicated that saline habitats are essential for <i>M. ohione</i> development, and larval mortality increased after 3-4 days of freshwater drifting. This provides indirect evidence that upstream populations have extended marine larval development. </p><p> Due to their limited freshwater survival, <i>M. ohione</i> must deliver larvae to the sea. Spatial-temporal analysis in the Atchafalaya and Mississippi Rivers reported an influx of reproductive-sized shrimps and females with near-hatching broods into coastal sites. This suggests that females are migrating downstream to hatch larvae in downstream habitats. </p><p> Stable isotope analysis indicated that the upstream juvenile migration originates from saline habitats. Video surveillance revealed that juveniles migrate throughout the night at an average speed of &sim; 0.56 km hr^-1, and swimming speeds were related to the water velocity they swam against. From these results, I estimated that juveniles are capable of migrating to far-upstream habitats within their life span (1-2 years). </p><p> Lastly, I investigated how dams affect the juvenile migration, and tested juvenile migrant climbing abilities. This study reported greater densities of juveniles downstream of dams than upstream of dams, indicating the dams impede the juvenile migration downstream of Old River Control. Shrimp climbing studies revealed that at various inclinations and water velocities, ~ 52% of the shrimps were climbing the shrimp ramp and ~ 12% completed the climb. These results demonstrated juveniles can climb bypass structures with detectable water flows. </p><p> My findings suggest that <i>M. ohione</i> populations within the Mississippi River System are amphidromous, because they require marine larval development and long-distance migrations are conducted to and from the sea. This study may serve as a general model for migrations of amphidromous shrimps in comparable large rivers, and potentially contribute to freshwater shrimp conservation.</p>

The number of species of tapeworms readily available for laboratory control is quite limited. Two species in particular seem best suited for testing the interesting hypothesis propounded by Read, Simmons, Campbell and Rothman (1960). Hymenolepis diminuta, a cestode whose normal definitive host is the wild rat, grows quite well in both albino rats and hamsters, attaining a greater size in the former (Read and Voge, 1954). Hymenolepis citelli, a parasite of ground squirrels, is morphologically very similar to H. diminuta, and while it grows quite well in hamsters, growth and development is very poor in the albino rat (Read and Phifer, 1959). Thus, a knowledge of the characteristics of absorption of amino acids by the two worms, together with a knowledge of the amino acid mixtures characteristic of the intestines of different host species, will perhaps allow direct experimental testing of the hypothesis that these factors are involved in establishment and development of a tapeworm in a particular host species. It is apparent that we still know very little concerning amino acid absorption by Hymenolepis diminuta. The present study was designed to increase our understanding of this phenomenon, especially concerning the absorption of L-methionine by this cestode. Advantage was taken of the more adequate methods described by Read, Simmons and Rothman (1960) to overcome the defects in design of experiments performed by Daugherty (1957a, 1957b) and Daugherty and Foster (1958). In addition it was hoped that such a study would reveal whether the methods employed and the species studied would be suitable in undertaking experimentation designed to answer some fundamental questions concerning the ecological relationship called "parasitism", raised by our present knowledge of amino acid permeation into tapeworms.

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.

Social insect workers often sacrifice their own reproduction so that they may help relatives to reproduce more successfully. However, genetically dissimilar colony-mates may prefer to aid different kin, and this may result in disruptive conflicts. I developed polymorphic microsatellite genetic loci for the African swarm-founding wasp Polybioides tabidus to examine mechanisms to reduce such conflicts. Swarm-founding wasps have many reproductive queens in their colonies which should lower relatedness, increasing the potential for conflicts. I found that even though P. tabidus colonies contained many queens, relatedness was elevated because new queens were only produced after the number of old queens had been reduced to one, or nearly one. Queens were thus highly related, elevating relatedness in the colony as a whole, and promoting sociality. This unique pattern of queen production is consistent with a worker manipulation of the sex ratios known as cyclical oligogyny. Under cyclical oligogyny, new queens are produced when the colony has few queens, while males are produced when the colony has many queens. The males were indeed produced when queen number was higher, and I found evidence that the workers collectively controlled male production. Colonies which produced normal haploid males also produced diploid males, which have a diploid genome but are homozygous at the sex determining locus. P. tabidus does not appear to effectively distinguish between diploid and haploid males, and diploid males should have occurred in colonies without haploid males too. Their absence indicates that they were actively eliminated from colonies in which the workers did not favor male production. Workers also may have controlled who produced the males. Each worker should prefer to produce the males herself. However, I found that the queens produced the males. This may be explained by collective worker policing because the workers would be more highly related to queen-derived males than to the sons of other workers and should prevent reproduction by other workers. Alternatively, each worker might restrain herself if worker reproduction was costly to the success of the colony. The results of this study indicate that collective worker control is an important mechanism stabilizing cooperation.

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.

<p> Polychlorinated biphenyls (PCBs) negatively affect reproduction across taxa. However, how PCBs influence elasmobranchs is not well known. I hypothesized that acute PCB exposure would negatively impact reproductive parameters of newly-mature round stingrays (<i>Urobatis halleri</i>). To determine the acute effects of PCBs on steroidogenesis, male stingrays were injected with either Aroclor-1254 or vehicle (sesame-oil) and held for 24 hrs. Testicular mRNA expression for steroidogenic acute regulatory protein and 3&beta;-hydroxysteroid dehydrogenase decreased with 24 hrs exposure to Aroclor-1254 (p&lt;0.05). To test sperm quality, seminal fluid was exposed to Aroclor-1254 (0.00, 0.001, 0.010, 0.100, 1.000, 10.00 mg/L) for &lt; 1 or 24 hrs. Aroclor-1254 (10.00 mg/L) decreased spermatozoa motility and viability at both time-points compared to controls (p&lt;0.001). At &lt; 1 hrs, spermatozoa motility decreased from the control at 1.000 mg/L (p&lt;0.05) and viability decreased at 0.010 mg/L (p&lt;0.05). These results indicate that Aroclor-1254 may have targeted effects on <i>U. halleri</i>, inhibiting spermatozoa function and steroidogenic enzyme activity at an acute dose.</p>

<p> This study used fine-scale phylogeography of populations of side-blotched lizard, <i>Uta stansburiana</i> to determine concordance with previously identified phylogeographic patterns in the Transverse Mountain Range of Southern California. Mitochondrial DNA analysis revealed clade distributions that both agreed and conflicted with previously identified clade breaks. This study revealed two new distinct clade breaks that transect the San Gabriel Mountains and detected haplotype mixtures in populations sampled between the San Gabriel and San Bernardino Mountains. Genetic landscape GIS analyses identified areas of genetic divergence and diversity for this species. This combined analysis enabled the discovery of a suture zone between the San Gabriel and San Bernardino Mountains that represents a phylogenetic crossroads with high levels of diversity and divergence and complex phylogeographic structure. My results suggest the importance of the use of fine-scale phylogeographic analysis in the discovery of new clade boundaries within a geologically complex and hyper-diverse region.</p>

<p> Rhamphichthyoidea is a monophyletic clade of Neotropical electric fishes (Ostariophysi, Gymnotiformes), with about 55 known species, some still awaiting formal description. These species are widespread in tropical and subtropical freshwaters of South America, with a single species reaching Costa Rica in southern Central America. Rhamphichthyoid species inhabit a variety of lowland habitats including small sandy streams, floodplain oxbow lakes, and the benthos of deep river channels. Rhamphichthyoidea displays substantial morphological disparity, ranging in maximum total body size from 62 millimeters to about 1 meter, and exhibiting diversity of distinctive snout shapes. This phenotypic diversity is reflected in a broad range of ecological interactions and foraging modes. Here I studied the diversity of Rhamphichthyoidea at three levels: alpha diversity, species interrelationships, and macroevolutionary patterns. The first chapter presents results of a species level phylogeny using a total evidence approach, including a new classification based on phylogenetically diagnosed clades. The second and third chapters review the species diversity and boundaries of the poorly studied genera <i>Rhamphichthys</i> (7 spp.) and <i>Gymnorhamphichthys</i> (5 spp.). The fourth chapter presents an analysis of diversification through time, linking habitat occupancy with morphological aspects of snout shape in the radiation of Rhamphichthyoidea. In summary, this dissertation provides information on the species diversity, morphological characteristics, biogeography of the long-snouted rhamphichthyids; the phylogenetic relationships and a newly proposed classification of Rhamphichthyoidea; and adds to the understanding of general patterns of diversification within the Neotropical ichthyofauna.</p>

<p> Humans introduce non-native plants to new areas at an increasing rate with the increased movement across the globe. These invasive species can become mono-cultures and extremely different from the native floral community. Amphibians, at the same time, are facing global declines with approximately one-third of all amphibians threatened or endangered. Due to the importance of amphibians as prey items for many vertebrates including small birds, mammals, and reptiles, and also predator controls over many invertebrates, including some pest species, the decline of amphibians has large implications for many environments. This study looks at a range of interactions between two invasive plants (<i> Typha angustifolia</i> and <i>Phragmites australis</i>) and two native anurans (<i>Lithobates clamitans</i> and <i>Lithobates catesbeianus</i>). </p><p> As ecosystem engineers, plants form the basis of many communities, and sculpt the physical environment by adding complexity to the earth's surface. They also add chemical constituents either actively or passively too ward off other competitors. This change in the environment on both the chemical and physical level leads to complex possibilities for a changed plant community to impact the rest of the ecosystem, including amphibians. I focus on the physical changes by looking at behavior of amphibians in these invasive plant mono-cultures and non-invaded controls, and their appearance in invaded and non-invaded wetlands, both constructed and naturally occurring. On the chemical side of the matter, I monitor water chemistry measures in natural and constructed wetlands that are either lacking invasive plants or have a substantial presence of these plants, and correlate those measures with tadpole growth and survival. </p>

<p> The neural dimorphisms in the zebra finch present one of the most unique examples of sexual differentiation observed in vertebrates. Although knowledge of these differences has been established for over 45 years, the exact mechanism by which they arise is not known. This dissertation provides additional support for estrogens' involvement in brain development. Specifically, blocking of estrogen receptors with ICI 182,780 decreased neuron soma size of song control regions in both sexes during development. These results are distinctive since previous attempts to block estrogen receptors failed to see the large degree of difference my work displayed. I further supported the role of estrogens in neural brain dimorphisms by decreasing the synthesis of aromatase, an enzyme needed for estradiol production, with the administration of Fadrozole. This successfully decreased neuron soma sizes, neuron number, and nuclear volume in song control regions in males and females, which had not been seen in prior attempts from other laboratories. I have concluded that the route of delivery used in these experiments is likely the largest contributing factor to generating these unique results. I also provide evidence of a potential role for ER alpha by displaying its presence at an early post-hatching age in two auditory processing regions. Taken together, my work provides further support for the role of estrogens in the dimorphic development of the brain, and establishes that it is unlikely that ER alpha contributes to neural dimorphisms in the zebra finch.</p>