No description available.

No description available.

No description available.

Previous research suggests that prey-switching behavior by consumers (adaptive foraging) contributes to the stability of food web networks and may help explain the apparent contradiction between the complexity of natural ecosystems and theory that suggests such complex systems should be unstable. However, no previous study has explored the consequences of adaptive foraging behavior on ecosystem processes (or `functioning'). I assembled communities from regional pools while varying searching efficiency, connectance, and the fraction of adaptive foragers in order to observe the effects these properties have on the diversity and functioning of the resultant communities. In general, pools with increased connectance, a higher fraction of adaptive foragers, and intermediate searching efficiencies yielded communities with greater diversity. However, while pools with high connectance and intermediate searching efficiencies tended to have higher ecosystem productivity, adaptive foragers decreased the overall productivity of the assembled communities. Unsurprisingly, adaptive foragers, connectance, and increased searching efficiency all led to higher rates of trophic transfer. These trends occurred alongside an overall positive correlation between diversity and the rates of these processes. In addition, the higher regional richness increased the per-species functioning of the assembled community. These results suggest that the diversity and structure of food web networks interact with the dynamics of trophic interactions to determine and maintain the properties and processes of ecological communities. vii

The Ecuadorean Andes sustains one of the most remarkable frog diversifications. In this region, nearly one in three known species of amphibians belong to the Pristimantis genus, which contains the majority of the direct-developing terrestrial frog species. Although efforts are ongoing to understand the diversity of Pristimantis, large regions of the ecosystems they occupy remain understudied, and speciation and diversity of this genus remains poorly understood. Within this context, an interesting taxon with many unresolved questions regarding patterns and process of diversification is the Pristimantis orestes species complex which is distributed across the Paramo landscape and montane forests in the eastern and western slopes of southern Ecuador. In my thesis, I present a new molecular phylogeny for the P. orestes group based on samples obtained from 62 localities in the south of Ecuador, including samples from type localities of previously described species. First, I used morphological, behavioral, biogeographical and molecular evidence to describe two new species and re-describe P. orestes sensu stricto. Next, I used the molecular phylogeny to delimit candidate species in the group and test for drivers of genetic and morphological diversification, leading to the identification of 13 previously described taxa and 28 undescribed species as part of the P. orestes group. I find evidence that elevation and features of hand morphology are both linked to differentiation among the two major clades in the P. orestes group. However, differentiation within these clades is not explained by elevation or geographical distances, and elevation and hand morphology are not correlated after controlling for phylogenetic relationships. Overall, my results suggest that diversification within the clades is largely driven by vicariance processes, but that local adaptation to microhabitats driven by morphological variation in hand structures may also contribute to speciation in this group.

An intertidal creek off the York River, Va. was sampled for juvenile and adult fishes during the spring, summer, and fall of 1981. Over 21,500 individuals of 14 species were collected using a block net technique. Ninety-eight percent of the total number was derived from five species which were, in order of abundance; Brevoortia tyrannus, Fundulus heteroclitus, Anchoa mitchilli, Leiostomus xanthurus, and Menidia menidia. Diel variations in abundance were indicated for A. mitchilli and M. menidia juveniles which were mostly captured at night and for M. menidia adults, L. xanthurus juveniles, and F. heteroclitus of all ages which were typically captured during the day. A. mitchilli and M. menidia were no longer captured in the intertidal creek after reaching sizes of approximately 60 mm SL and 67 mm Sl, respectively. Production estimates for the fish captured in the intertidal creek system were calculated to equal 2.53 g dry weight m('-2) or 13,051 cal m('-2).

No description available.

No description available.

Archaeorhizomyces is a class of filamentous fungi in Ascomycota, and is abundant in soil. However, seldom has it been deeply researched. Archaeorhizomyces finlayi and Archaeorhizomyces borealis are two different species of Archaeorhizomycetes. Some filamentous fungi can exhibit dimorphic switch between multicellular hyphae and unicellular yeasts; besides, many fungi also produce conidia or other asexual spores under certain situation. These conditions convey the information about growth preferences and life cycles dynamics. In this report, the differences between A. finlayi and A. borealis in their growth as yeasts and formation of conidia in response to different pH and nitrogen sources are observed and discussed, for a deeper understanding of their life cycles. Results turn out that they have different preferences to certain media for producing conidia and yeasts, which means that they may have different life strategies. Besides, chlamydospore were observed in A. borealis culture in tested conditions, chlamydospore reflecting differences between the two species.

Ciliates are basal eukaryotes from Phylum Ciliophora that were first described 400 years ago, but their origins date back 800 million years. Such early origins have allowed contemporary ciliates to be remarkably diverse in both their species numbers and ecological adaptations. Peritrichia, a subclass of ciliates, represents an ideal model to study ciliate diversity, as its members display complex phylogenetic relationships and can be epibionts colonizing the body surface of other organisms. Epibiotic relationships are ecologically and evolutionarily important due to the extensive adaptations in epibiont biology to the life cycles of hosts. These relationships are also important for host population dynamics, as peritrich epibionts can cause myriad detrimental effects on their hosts. The overall goal of this dissertation is to investigate peritrich ciliate distribution and ecology in Chesapeake Bay, as well as to examine epibiotic relationships with its copepod hosts in a multidisciplinary approach combining extensive sampling and molecular analyses. Zoothamnium intermedium, a peritrich epibiont, was used as an evolutionary and ecological model, as this species aggregates several of the obstacles found in the study of ciliates and several groups of basal eukaryotes. The ecological importance of ciliates is introduced in Chapter 1. Key points of their diversity and life history are presented to introduce the topics that will be discussed throughout this dissertation. Chapter 2 examines qualitative data on the seasonality and host preference of Z. intermedium along with relationships to water quality parameters in the York River, Virginia, USA. Results from plankton sampling showed that colonization by Z. intermedium was specific to Acartia tonsa and Centropages hamatus. Host identifiction was confirmed by analysis of the host mitochondrial cytochrome oxidase I gene. Analysis of the small subunit rDNA (SSU rDNA) sequences from the epibiont revealed identical sequences from specimens obtained from the two hosts. Both host species are calanoid copepods but are distributed differently in the water column. Colonization of hosts was uneven across all seasons, and was strongly correlated with dissolved oxygen, salinity, water temperature, and total suspended solids. The different life histories of the two copepod hosts species, coupled with the fact that a high number of free-living (non-epibiont) peritrichs were found in the settlement traps, led us to question the diversity of Z. intermedium and other peritrichs in water bodies of Chesapeake Bay. In Chapter 3, we broadened the molecular analysis to incorporate sequences from both epibiotic and free-living peritrich species. By using the same methods of sample collection from Chapter 2, we found new species of calanoid copepod host, different than the ones previously described for Z. intermedium in the York River. Eurytemora affinis and Undinula vulgaris, both calanoid copepods were also found as hosts for morphologically similar Z. intermedium. The diversity of the Z. intermedium sequences, however, did not follow an obvious distribution. SSU rDNA phylogenetic analysis showed a deep separation between sequences obtained from different A. tonsa populations, which has a cryptic species complex in Chesapeake Bay. Genus Zoothamnium was the most diverse peritrich genus in our samples, followed by genus Pseudovorticella. Such finding might not be aleatory, as previous studies have hypothesized that Zoothamnium and Pseudovorticella species are more common in brackish and marine waters as a result of their more recent invasion from freshwater habitats. Such results underscore the importance of a multidisciplinary approach in the understanding of ciliate-host relationships. Knowledge of species ecology and distribution aids molecular analysis in the best choice of genes to study ciliates with different life histories. In Chapter 4, the focus shifts to host microbiome and potential interactions with Z. intermedium. The microbiome of both colonized and uncolonized A. tonsa was analyzed by high throughput sequencing of bacterial 16S ribosomal RNA (16S rRNA). While dominant bacterial taxa and alpha diversity values were similar between colonized and uncolonized copepods, one ASV (Amplicon Sequence Variant), belonging to family Neisseriaceae, was present only in colonized hosts. The beta diversity analysis was also different, showing a significant separation of the 16S community structure, with different clusters of colonized and uncolonized copepods. Finally, Chapter 5 summarizes all research and main findings of the research conducted in the previous chapters and concludes by discussing such findings as a comprehensive unit. The results obtained in this dissertation provide new knowledge on the evolutionary and ecological diversity of peritrich ciliates, while emphasizing the need for a holistic view of microbial relationships to investigate aquatic ecosystems.