Made available in DSpace on 2014-06-11T19:22:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T19:49:21Z : No. of bitstreams: 1 almeida_hj_me_sjrp.pdf: 760562 bytes, checksum: 3990a9566c6c626d3c9aa06da14b06bf (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A diversidade local de espécies pode ser regulada por fatores locais (como competição, perturbação, condições abióticas, dispersão) e regionais (como a história climática, evolução e migração). O objetivo deste estudo foi entender quais fatores locais e da paisagem melhor explicam os padrões de distribuição de espécies de anuros. O estudo foi desenvolvido na região noroeste do Estado de São Paulo, entre julho de 2007 e fevereiro de 2009, empregando duas metodologias de amostragem: 1) armadilhas de interceptação e queda, instaladas no interior de 18 fragmentos florestais, e 2) procura auditiva e visual em 64 corpos d’água da região. Das 37 espécies conhecidas para esta região, 30 foram registradas neste estudo, sendo 13 no interior dos fragmentos florestais e 29 nos corpos d’água. A eficiência de amostragem foi avaliada por rarefação da curva do coletor. A curva do coletor atingiu a assíntota, indicando que para encontrarmos mais uma espécie o efeito amostral deveria ser muito intensificado. Modelos lineares generalizados (GLM) e análise de ordenação foram aplicados aos dados dos fragmentos florestais, incluindo uma variável espacial (coordenadas geográficas) como preditor de riqueza e composição além das variáveis ambientais que descrevem os fragmentos florestais. Para verificar qual variável ou conjunto de variáveis explicam a riqueza e composição de espécies observadas nos corpos d’água, foram aplicadas análises de regressão linear e correlação de matrizes. Se um efeito significativo fosse detectado, isso indicaria que a riqueza e composição de espécies dos fragmentos florestais e/ou corpos d’água seriam formadas por processos de seleção de habitat. Os resultados indicam que nem as características nem a sua localização geográfica dos fragmentos tem efeito significativo... / Species local diversity can be regulated by local (such as competition, disturbance, abiotic conditions) and regional factors (climate history, evolution and migration). The aim of this study was understand which local and landscape factors best explain the distribution patterns of anuran species. The study was developed in the northwestern São Paulo State between july 2007 and february 2009, using two sampling methods: 1) pitfall traps, installed in the interior of 18 forest fragments, and 2) hearing and visual search in 64 ponds located around the forest fragments. We registered 30 of the 37 known species to the study region: 13 in the interior of forest fragments and 29 in ponds. A rarefaction curve was used in the assessment of the sampling efficiency and results indicate that sampling effort should be highly intensified in order to find one more species. We characterize forest fragments and ponds by measuring five and ten environmental variables, respectively. These environmental variables were used as predictors of richness and composition of these habitats. General Linear Models (GLM) and ordination analysis were applied to the forest fragments data, which includes a spatial variable (geographic coordinates) as a predictor of richness and composition besides environmental variables that describe the forest fragments. In order to verify which variable or set of variables would explain the observed species richness and composition in ponds, it was applied linear regression and matrices correlation to the data. If a significant effect was detected, this would indicate that species richness and composition of the forest fragments and/or ponds are shaped by habitat selection processes. Results indicate that neither the fragments characteristics nor their location have significant effect over the species... (Complete abstract click electronic access below)

In this study we wanted to investigate the community ecology of African termites and uncover possible mechanisms structuring these species communities. Termites are important ecosystem engineers, crucial for the maintenance of tropical biodiversity and ecosystem functioning, therefore we wanted to show how anthropogenic disturbance influences these termite communities. Using a cross-sectional approach, we studied termite community composition along a disturbance gradient from fields to 12-year-old fallows in a West African savannah. We could show that disturbance was associated with environmental filtering of termites from the regional species pool, maybe via its effect on vegetation type. The most heavily disturbed sites were characterized by a subset of termite species which are well-known pests of crop. This supports a model in which strong anthropogenic disturbance selects for termite pest species. Additionally, we comparatively studied termite communities in the two major West African ecosystems, savannah and forest, both under natural settings and along disturbance gradients. Overall we found 33 species in the forest and 22 in the savannah. However, alpha diversity per site did not differ between both ecosystems with on average around ten species. For both ecosystems, species diversity did not decrease along the studied disturbance gradient but encounter rates did. In general, we found little evidence for strong community structuring mechanisms such as environmental filtering or interspecific competition in the natural habitats. Most local communities did not differ significantly from random assemblages of the regional species pool. Interestingly, only the disturbed sites in the savannah showed some sign of phylogenetic structuring, the teak plantation sites did not. By using stable isotope analysis we could investigate how so many termite species with very similar feeding niches can coexist in an African savannah. We discovered that closely related species either differed in their δ15N and /or δ13C signatures, providing support for our hypothesis that fine-scaled differentiation of the feeding niche exists between termites in the studied area that formerly have been classified as feeding on the same dead plant material. We were able to distinguish feeding groups with stable isotope analysis, as each feeding group had a specific δ15N and δ13C signature, supporting the classification of Donovan et al. (2001). Comparatively, we tested whether southern African termite communities show signs of environmental filtering and / or competition along a rainfall gradient in Namibia. There was a regional species pool of 11 species and we found no evidence for phylogenetic structuring at the local scale. Rather, our results suggest that the assembly of the studied termite communities has as strong random component on the local scale, but that species composition changes along the climatic gradient. Interestingly, species richness and species composition was different to West African termite communities.

Plant communities that occur on edaphically heterogeneous landscapes are ideal systems for exploring questions of niche and community assembly. Species with affinity for harsh substrates often have well-defined edaphic niches and are ideal models for testing ecological and evolutionary theory. While plants on substrates such as serpentine and gypsum have received much attention, those on other harsh substrates, including on vertic clay soils, have gone unstudied. Vertic clay soils are both chemically and physically challenging to plant establishment and productivity. Plant communities associated with vertic clay soils of the San Joaquin Desert appear to have a distinctive mosaic pattern of species distribution that reflect differences in soil properties across the landscape. I conducted fieldwork and a pot study with 12 native annual plant species with an affinity for vertic clay soils to determine whether the vertic clay soils at two sites in the San Joaquin Desert were heterogeneous, whether soil heterogeneity predicted the pattern of species distributions observed, and to examine the competition effects of an invasive annual grass (Bromus madritensis) on these species. I found that the vertic clay soils at both of my sites are internally heterogeneous, that soil heterogeneity does appear to shape the patchy distribution of species at both these sites, and that these species have different realized edaphic niches. I utilized treatment soils spanning a gradient of chemical stress present at both study sites in my pot study and found that competition from B. madritensis reduces biomass for all species, and that the effect of competition differed between soil types. Further, I found that species’ edaphic niche optima shift when competition is present, and that competitive ability differed across the gradient of edaphic stress in my treatment soils.

In intermittent streams, hydrological variation is probably the single-most important factor affecting fish assemblage structure. While the response of aquatic assemblages to seasonal or annual variation in hydrology is well-known, less attention has been devoted to how assemblages respond to natural, intraseasonal drought. To explore this question, I conducted summer surveys of fish and aquatic insect assemblages occupying pool refugia in first to third order, intermittent streams in the Saline river drainage in the Ouachita highlands (central Arkansas, U.S.A.)(2001?2003). The goals of this project were: 1) to relate assemblage variability of fishes and aquatic insects to environmental gradients during summer drying of streams; 2) to characterize the variability of fish assemblages occupying pool refugia, which differed in quality along a spatial gradient; and, 3) to determine the population genetic structure of five fish species across the intermittent landscape. Hydrological variables explained significant variation in assemblage variability for fishes. In contrast, variability in aquatic insect assemblages was related to water quality variables. These patterns are similar to those observed at larger scales of space and time. As pools dried, neither fish species richness nor the slope of the species-area relationship changed. However, the structure of many assemblages was variable over time. Pools with a relatively stable hydrology were sources of reproduction and high population growth, low extinction and high immigration. Sites that exhibited a more variable hydrology (drying completely or nearly-so) were sinks characterized by population declines. The majority of sites had minimal population growth, and intermediate immigration and extinction rates, and were dubbed metapopulations. Immigration and extinction dynamics had important effects on population genetics for common fish species. Two common species had relatively high immigration rates and showed no population differentiation. Populations of three species showed differentiation that was not related to geographic distance among sites. Instead, local extinction of rare haplotypes and evidence of recent bottlenecks suggested that ecological attributes associated with summer drought affected population differentiation. It is clear that retaining the natural hydrology of stream systems contributes to the maintenance of biodiversity, and the conservation of complex demographic processes and genetic patterns.

Cavity-nesting guilds are diverse communities of organisms that are hierarchically structured around the creation of and competition for tree holes as nest sites. Quantifying these communities as networks of interconnected species, or "nest webs", is a proven and efficient method for identifying important species and interactions within a cavity-nesting guild that can aid the management of these often threatened communities. Yet nest web data does not provide information regarding how natural resource managers are to encourage the support and adoption of conservation behaviors. This dissertation comprises two broad studies: one describing a cavity-nesting guild in central Namibia, and the other exploring methodology for identifying an effective flagship species for local conservation. In chapter 1, I provide background information of my study system and a review of the cavity-nesting and flagship species literature. In chapter 2, I quantify the species and resources within a cavity-nesting guild and create a cavity nest web to depict cavity creation and use in central Namibia. All cavity-nesters depended on sparse, large trees, which likely contributed to limited use of tree species across the guild. Cavity-excavators were of disparate importance for secondary cavity-nesters: important for small- and medium-bodied species but mostly unimportant for large-bodied species who depend more on large trunk hollows. In chapter 3, I describe and compare species-specific cavity resource niches among guild members to explore potential instances of cavity resource partitioning. Use of nest cavities appears to sort out by size among both cavity-excavators and secondary cavity-nesters. Excavators appear to partition cavity substrate spatially by decay class, while spatial partitioning among secondary nesters was largely by cavity type. Most interesting is the apparent temporal partitioning of large excavations among medium- and large-bodied cavity-nesters. In chapter 4, I explore a novel approach to flagship species selection that identified all previously-existing traits for flagship species, numerous traits specific to culture and personal experience, and a dozen new traits that were previously not recognized as potentially important for flagship species. This method shows considerable promise as a tool for investigating preferences for wildlife among broad stakeholders, as well as for engaging local people in wildlife conservation. / Doctor of Philosophy / Holes in trees, or cavities, are important resources for many birds, who use cavities as a safe place for raising young. Cavity-nesting birds are linked together in a cavity "nest web" based on the types of cavities used by each species. Understanding how birds are linked with each other and with certain types of cavities is critical in order to design conservation plans that preserve important community relationships. However, successful conservation also depends on strong support from local people, who are most often the people tasked with implementing the conservation actions. Flagship species can be used to gain support from necessary groups of people for specific conservation missions. This dissertation consists of two broad studies: the first study describes a community of cavity-nesting birds in Namibia, and the second explores a new way to investigate how people connect with wildlife through emotional connections. In chapter 1, I provide background information on my area of research. In chapter 2, I outline the different trees, cavities, and birds at the study site and estimate their abundance in the area. I also create a cavity nest web that illustrates the links between species. Large trees were relatively uncommon, but were important for all birds in the community. Cavities made by other birds, such as woodpeckers, were very important for small- and medium-sized species, but were mostly unimportant for large-sized species. In chapter 3, I compare the tree cavities used by different species, including the types of trees, cavities, and cavity sizes. I also explore multiple ways by which cavity-nesting birds might be dividing cavities between different species. Our most interesting finding was how medium-sized species seem to share cavities in time rather than in space; some species (i.e., small owls and woodpeckers) breed before some larger species that use the same type of cavity. Breeding early may be a way for some species to avoid competition with more competitive species, and may be the first example of this strategy being used by multiple cavity-nesters in a community. In chapter 4, I explore a new method for selecting flagship species. This method uncovered all traits that have been previously recommended for flagship species, as well as many traits specific to culture and personal experience. We also identified a dozen new traits that were previously not considered to be important for flagship species. Our new method is very promising as a tool for investigating preferences for wildlife among broad stakeholders, and for engaging and involving local people in wildlife conservation.

Crayfish throughout the holarctic are found in association with an order of worms known as branchiobdellidans. This relationship has been confirmed as a cleaning symbiosis in several species. The Conhaway crayfish,​ Cambarus appalachiensis, is a species of crayfish endemic to the New River Basin in Virginia and West Virginia. We studied a population of ​ C. appalachiensis​ in Sinking Creek in Newport, VA from March 2017 until February 2018. We collected morphological data and quantified the branchiobdellidan communities on 986 individuals, and kept note of egg brooding and young of year throughout the study period. The life cycle of C. appalachiensis was found to be similar to other large-bodied species of Cambarus crayfish. Molting occurred throughout the year, peaking in the months of April and September. This molting served as a disturbance effect to the symbiotic branchiobdellidan community and reset community assembly. The worm communities on larger, recently molted crayfish more closely resembled the less diverse communities on smaller crayfish. Most worms on recently molted crayfish were ones that we know are early colonizers. This thesis work provides the first life history information on a newly described species of Cambarus crayfish and provides both seasonal data on its branchiobdellidan associates and one of the first empirical examples of host ontogeny acting as a disturbance on a symbiotic community. / Master of Science / Crayfish throughout North America and Eurasia are the symbiotic partners to a number of small worms. This relationship has been confirmed as a cleaning symbiosis for several crayfish, similar to the cleaning stations at a coral reef. The Conhaway crayfish is a species of crayfish found in the New River Basin in Virginia and West Virginia. We studied a population of Conhaway crayfish in Sinking Creek in Newport, VA from March 2017 until February 2018. We collected data on the physical attributes of the crayfish, quantified the worms present on 986 individuals, and kept note of female crayfish with eggs and baby crayfish throughout the study period. The life cycle of the Conhaway crayfish was found to be similar to other large-bodied species of closely related crayfish. Molting, where the crayfish loses its shell and grows a new one, occurred throughout the year, peaking in the months of April and September. This molting served as a disturbance effect to the symbiotic worms, similar to how a wildfire might displace animals in a grassland ecosystem. The type and number of worms found on larger, recently molted crayfish more closely resemble the type and number of worms found on smaller crayfish. This thesis work provides the first information on the physical and reproductive attributes of a newly described species of crayfish and provides both seasonal data on its symbiotic worms and one of the first empirical examples of host growth and aging acting as a disturbance to symbiotic organisms living on that host.

Shellfish aquaculture is a developing industry along northeast Pacific coastlines and represents another potential stressor to already impacted nearshore ecosystems. The industry is particularly prominent in Baynes Sound, British Columbia (BC), Canada. The region hosts the operations which account for approximately 35% of all clams and 50% of all oysters produced in BC. Concurrently, it represents one of the most ecologically valuable areas in the northeast Pacific. In this study, I examined the interactions of benthic intertidal shellfish aquaculture with nearshore fish communities using abundance, biodiversity (species richness, diversity, and evenness), and functional diversity (Rao’s quadratic entropy and functional evenness) metrics. Also, I measured habitat complexity, as defined by a contour distance:linear distance ratio, at all fish sampling sites because it has often been identified as a driver of community variation. Fish abundance, biodiversity, and functional diversity did not vary between aquaculture and non-aquaculture sites. Additionally, habitat complexity, while on average was 1.2x greater at aquaculture beaches compared to non-aquaculture reference beaches, was not a strong driver of these indicators. Fish communities in Baynes Sound are relatively homogenous on a small scale and are highly functionally redundant, meaning that there is considerable overlap of species’ roles in the ecosystem. In summary, the presence of shellfish aquaculture in Baynes Sound is not associated with either a positive or negative response of fish communities. Furthermore, these communities are functionally redundant and therefore are likely resilient to ecosystem disturbances. / Graduate

<p>Environmental changes, such as climate change, can have differential effects on species, with important consequences for community structure and ultimately, for ecosystem functioning. In the Arctic, where ecosystems are experiencing warming at twice the rate as elsewhere, these effects are expected to be particularly strong. A proper characterization of the link between warming and biotic interactions in these particular communities is of global importance because the tundra's permafrost stores a vast amount of carbon that could be released through decomposition as greenhouse gases and alter the global rate of climate change. In this dissertation, I examine how arthropod communities are responding to warming in the Arctic and how these responses might be affecting ecosystem functioning. </p><p>I first address the question of whether and how long-term changes in climate are affecting individual groups and overall community structure in a high-arctic arthropod food web. I find that increasingly warm springs and summers between 1996-2011 differentially affected some arthropod groups and that this led to major changes in the relative abundances of different trophic groups within the arthropod community. Specifically, spring and summer warming are associated with relatively more herbivores and parasitoids and fewer detritivores within the community. These changes are particularly pronounced in heath sites, suggesting that arthropod communities in dry habitats are more responsive to climate change than those in wet habitats. I also show that herbivores and parasitoids are sensitive to conditions at subzero temperatures, even during periods of diapause, and that all trophic groups benefit from a longer transition period between summer and winter. These results suggest that the projected winter and springtime warming in Greenland may have unexpected consequences for northern arthropod communities. Moreover, the relative increase in herbivores and loss of detritivores may be changing the influence of the arthropod community over key ecosystem processes such as decomposition, nutrient cycling, and primary productivity in the tundra. </p><p>Predator-induced trophic cascades have been shown to impact both community structure and ecosystem processes, yet it is unclear how climate change may exacerbate or dampen predator effects on ecosystems. In the second chapter of my dissertation, I investigate the role of one of the dominant tundra predators within the arctic ecosystem, wolf spiders, and how their impact might be changing with warming. Using results from a two-year-long field experiment, I test the influence of wolf spider density over the structure of soil microarthropod communities and decomposition rates under both ambient and artificially warmed temperatures. I find that predator effects on soil microarthropods change in response to warming and that these changes translate into context-specific indirect effects of predators on decomposition. Specifically, while high densities of wolf spiders lead to faster decomposition rates at ambient temperatures, they are associated with slower decomposition rates in experimentally warmed plots. My results suggest that if warming causes an increase in arctic wolf spider densities, these spiders may buffer the rate at which the massive pool of stored carbon is lost from the tundra. </p><p>Wolf spiders in the Arctic are expected to become larger with warming, but it is unclear how this change in body size will affect spider populations or the role of wolf spiders within arctic food webs. In the third chapter of my dissertation, I explore wolf spider population structure and juvenile recruitment at three sites of the Alaskan Arctic that naturally differ in mean spider body size. I find that there are fewer juveniles in sites where female body sizes are larger and that this pattern is likely driven by a size-related increase in the rate of intraspecific cannibalism. These findings suggest that across the tundra landscape, there is substantial variation in the population structure and trophic position of wolf spiders, which is driven by differences in female spider body sizes. </p><p>Overall, this dissertation demonstrates that arctic arthropod communities are changing as a result of warming. In the long-term, warming is causing a shift in arthropod community structure that is likely altering the functional role of these animals within the ecosystem. However even in the short-term, warming can alter species interactions and community structure, with important consequences for ecosystem function. Arthropods are not typically considered to be major players in arctic ecosystems, but I provide evidence that this assumption should be questioned. Considering that they are the largest source of animal biomass across much of the tundra, it is likely that their activities have important consequences for regional and global carbon dynamics.</p> / Dissertation

Doctor of Philosophy / Department of Biology / Keith B. Gido / A fundamental goal of ecology is to understand environmental associations of species. These associations can provide a basis for predicting spatial distributions in contemporary habitats as well as how those distributions might change in response to anthropogenic environmental change. Developing species distribution models is limited by an incomplete understanding of functional traits, spatial scaling, and the mechanisms and generalities of correlations among abundance and environmental gradients. I address these four issues using observational and experimental approaches. First, I tested opposing mechanisms of community assembly by measuring the dispersion (i.e., diversity) of three types of functional strategies at three spatial scales and along environmental gradients. I found that communities are assembled via abiotic environmental filtering, but the strength of this filtering depends on the spatial scale of investigation, longitudinal network position, and type of functional strategy. Second, I quantified community-environment relationships across thirteen sub-basins, nested within the three major basins within Kansas to evaluate the consistency (i.e., generality) in predictive capability of environmental variables among sub-basins and across spatial extents. I found that longitudinal network position is consistently the strongest predictor of community composition among sub-basins, but in-stream and catchment predictors become stronger correlates of community composition with increasing spatial extent. Third, I used environmental niche models to quantify distributions of four pairs of congeneric cyprinids and found that species within each pair exhibited contrasting stream-size preferences. I then used field experiments to test for differences in individual-level performance between one pair of species (Pimephales notatus and P. vigilax) along a gradient of stream size. I found that adult spawn success and juvenile growth and condition increased with stream size for both species, indicating that these congeners respond similarly to abiotic gradients associated with the river continuum. I concluded that complementary distributions are a consequence of biotic interactions, differential environmental filtering evident in an unmeasured performance metric, or differential environmental filtering by an environmental factor operating at longer timescales. These studies demonstrate the context dependencies of characterizing habitat associations of stream fishes, but also reveal the general importance of stream size and associated environmental gradients in structuring stream fish communities.

Processes structuring bee communities in agricultural landscapes are well-documented compared to those in other anthropogenic landscapes, like production forests. Forests across the temperate zone have historically been under-sampled, in part due to the perception that they provide little habitat to support diverse bee communities. While research suggests that early successional habitats support high levels of bee species richness and abundance, little empirical evidence exists to support the notion that forests, in turn, do not. To understand the relationship between forest successional age and major elements of the bee community, I sampled bees in a southern production pine forest in Hancock County, MS across 2012 and 2013. I found that while bee abundance declines with successional age, species richness does not. Combining this work with other recent research, I propose a generalized framework for understanding the role of disturbance and forest structure in structuring bee communities of southern forests.