The response of plants to climate change is among the main questions in ecology and evolution. Faced with changing conditions, populations may respond by adapting, going extinct or migrating. Fine-scale environmental variation offers a unique mosaic to explore these alternatives. In this thesis, I used ecological surveys, field experiments and molecular methods to study the range of possible responses at a very local scale in the alpine dwarf willow Salix herbacea L. Since gene flow may impact the potential for adaptation and migration, I first explored whether phenological divergence driven by snowmelt patterns impacts gene flow. I found that sites with late snowmelt work as sinks of the genetic diversity, as compared to sites with early snowmelt. I also used a combined approach that looked at the selection, heritability and genomic architecture of ecologically-relevant traits, as well as genomic divergence across the snowmelt mosaic. In this way, I was able to understand which genomic regions may relate to phenological, growth and fitness traits, and which regions in the genome harbor genetic variation associated with late- and early- snowmelt sites. I found that most of the genomic divergence driven by snowmelt is novel and is localized in few regions. Also, Salix herbacea has a strong female bias. Sex bias may matter for adaptation to climate change because different sexes of many dioecious species differ in several functions that may fluctuate with changing conditions. I found that the bias is uniform across environments and is already present at seeds and seedlings. A polygenic sex determination system together with transmission distortion may be maintaining the bias. Overall, fast-evolving microhabitat-driven genomic divergence and, at the same time, genetically-based trait variation at a larger scale may play a role for the ability of S. herbacea to persist in diverse and variable conditions. / SNSF Sinergia Salix

Masters of Science / Although the processes that promote biodiversity and speciation remain poorly understood, ecological factors are thought to be one of the causal agents responsible for promoting variation. Bladder grasshoppers (Orthoptera; Pneumoroidea) are a group of endemic southern African insects that provide an ideal model system to study the role of ecology in speciation. All species rely on acoustic communication for mate location, with males producing an extremely loud advertisement call that is highly species specific. Any alteration to the male call would thus likely have implications for species integrity. In this study, I examined geographic variation as well as potential ecological drivers of biological diversity within Bullacris unicolor, a variable and wide-ranging species of bladder grasshopper. The main aims of the study were to characterise the extent of acoustic and morphological variation among individuals sampled from five geographic locations and to correlate this variation with environmental data and host plant use. At the inter-population level, I found significant differences between populations with respect to both morphological and acoustic characters. Results of multivariate analyses showed significant differences in the body length, pronotum length and head width of males and in the pronotum length, abdomen width and head width of females. Similarly, the acoustic signals of males from the five populations differed significantly in both temporal and frequency components, with all but one variable (peak frequency of the introductory syllables) showing a significant difference. However, there was no correlation between morphological and acoustic variables among populations, and acoustic characters showed far greater divergence among populations than did morphology. In both males and females, the morphological variables that differed among populations were negatively correlated with mean annual temperature, indicating that grasshoppers are larger in areas with lower temperatures. Also, some of the call characteristics of males were correlated with temperature, precipitation, altitude, and slope. Although grasshoppers were observed feeding on a range of host plant species, neither morphology nor signal characteristics were found to vary according to host plant. At the intra-population level, multivariate analyses revealed that all acoustic characters differed significantly among individuals. Morphology may be influencing signal properties within a population to some extent as there were significant correlations between some of the call characters and both abdomen width and tibia length, with lengths of these two morphological variables being positively correlated with temporal components of the call and abdomen width being negatively correlated with frequency components. I also found a significant difference in the carrier frequency of male calls, as well as in some of the morphological characters of males and females, according to host plant. This indicates that host plant use has a greater effect on variation at the intra-population level than at the interpopulation level. In conclusion, the results of my study reveal significant variation in the morphology and acoustic signals of B. unicolor, both within and among populations, and suggest that this variation is at least partially related to ecological factors.

Species that vary in social structure within and among populations can provide unparalleled insight into the evolution of sociality. The theridiid spider Anelosimus studiosus varies widely in its social structure at the northern edge of its range. Colony sizes range from the solitary/territorial female with her offspring to cooperative colonies of tens to hundreds of adult females. In previous work, we developed an assured fitness returns 'brood-fostering model' that predicts that in cooler environments mothers in multiple-female colonies will have a selective advantage over solitary female nests. According to the model, at cool sites the rate of juvenile maturation is slowed, increasing the probability that the mother will die before the brood reaches independence. In her absence, other females would foster her brood. We tested this hypothesis by manipulating colony size and by monitoring the reproductive success of naturally occurring solitary and multifemale colonies in cold and warm temperature environments. Our results indicate that while multiple-female colonies have higher fitness at cool sites, the solitary female nests achieve higher fitness at warmer sites. The higher reproductive success of multifemale colonies at cold sites further reflects the total failure of solitary female nests at these sites. Solitary female nests that survived generally had higher reproductive success than multifemale colonies at all temperatures. In natural colonies, fitness was highest for smaller multifemale colonies in the colder environments and decreased in the larger colonies. We use these data to refine the brood-fostering model and discuss the results with regard to the observed polymorphism in social structure.

Abiotic and biotic variation has been shown to be important in regulating nutrient cycling and belowground communities in natural systems. However, genetic variation in dominant plants as a driver of rates of nutrient cycling is still poorly understood and few studies have looked at genotype interactions across multiple environments. Using Populus angustifolia and a common garden approach, we hypothesized that all three factors: tree genetic variation, environmental conditions and genetic by environment (G x E) interactions would affect soil carbon (C) storage and nitrogen (N) cycling. Replicated copies of five different reciprocally planted Populus genotypes were studied in three separate 18-21 year old common gardens at different elevations (1300m, 1384m and 1587m) in northern Utah, to measure the genotype and environmental effects on pools of soil C and N as well as rates of soil net N nitrification and net mineralization. Our results indicate that genotypes influence pools of soil C, total N and C:N, but genotype did not influence net rates of nitrogen mineralization. Environmental variation significantly influenced pools of soil C, total N, soil C:N and rates of net nitrification and net N mineralization. As predicted, G x E interactions significantly influenced both pools and processes of soil C and N cycling. Overall, we found that genetic variation in plant traits (tree diameter and leaf/root chemistry) as well as soil texture across gardens were significant predictors of soil C and N pools and fluxes across seasons. These data help us understand the relative role of genotypic variation on above- and belowground interactions in different environments and the consequences of these interactions on ecosystem processes. The results from this study show that across an environmental gradient Populus angustifolia genotypes can influence nitrogen mineralization through feedbacks between environmental variation, tree phenotype and soils.

Abiotic and biotic variation has been shown to be important in regulating nutrient cycling and belowground communities in natural systems. However, genetic variation in dominant plants as a driver of rates of nutrient cycling is still poorly understood and few studies have looked at genotype interactions across multiple environments. Using Populus angustifolia and a common garden approach, we hypothesized that all three factors: tree genetic variation, environmental conditions and genetic by environment (G x E) interactions would affect soil carbon (C) storage and nitrogen (N) cycling. Replicated copies of five different reciprocally planted Populus genotypes were studied in three separate 18-21 year old common gardens at different elevations (1300m, 1384m and 1587m) in northern Utah, to measure the genotype and environmental effects on pools of soil C and N as well as rates of soil net N nitrification and net mineralization. Our results indicate that genotypes influence pools of soil C, total N and C:N, but genotype did not influence net rates of nitrogen mineralization. Environmental variation significantly influenced pools of soil C, total N, soil C:N and rates of net nitrification and net N mineralization. As predicted, G x E interactions significantly influenced both pools and processes of soil C and N cycling. Overall, we found that genetic variation in plant traits (tree diameter and leaf/root chemistry) as well as soil texture across gardens were significant predictors of soil C and N pools and fluxes across seasons. These data help us understand the relative role of genotypic variation on above- and belowground interactions in different environments and the consequences of these interactions on ecosystem processes. The results from this study show that across an environmental gradient Populus angustifolia genotypes can influence nitrogen mineralization through feedbacks between environmental variation, tree phenotype and soils.

A partição aditiva da diversidade tem recebido cada vez mais atenção dos ecólogos, sendo utilizada como uma abordagem para fracionar a diversidade ao longo de múltiplas escalas. A abordagem permite ainda testar se a diversidade em cada uma das escalas é maior ou menor do que o esperado segundo uma distribuição de indivíduos ao acaso nas unidades amostrais. Este trabalho avalia a diversidade alfa e beta de nematódeos em cinco escalas espaciais (de cm a km). A importância de componentes ambientais e geográficos (dentro de lagoas e entre lagoas) na diversidade desses organismos também é estimada. Como medida de diversidade utilizou-se a riqueza de morfotipos. Através de dados da literatura, comparou-se a diversidade de Nematoda com os padrões de diversidade descritos para organismos unicelulares de mesmo tamanho (menores de 2 mm). A expectativa era que a assembléia de nematódeos apresentasse uma alta diversidade alfa nas escalas espaciais inferiores, como ocorre para protistas, e valores baixos para diversidade beta, uma vez que a variação na composição da nematofauna refletiria principalmente mudanças nas características ambientais. Foram registrados 13.358 indivíduos e 59 morfoespécies de nematódeos. A partição aditiva da diversidade revelou que a importância da diversidade beta nas escalas maiores (dentro e entre ambientes e entre lagoas) foi maior que o esperado. Através da Análise de Correspondência Canônica Parcial (pCCA), verificou-se que componentes ambientais explicaram 26,95% da variação na composição da nematofauna, enquanto componentes espaciais explicaram 9,93%. Os resultados indicam que nematódeos, ao contrário dos protistas, apresentaram uma baixa riqueza de espécies local (diversidade alfa), apesar de sua alta diversidade de espécies global. Além do mais, parece haver uma seleção de habitat por parte da nematofauna, o que é normalmente verificado para organismos multicelulares e de maior tamanho. / Additive diversity partitioning has received increasing attention of ecologists as a tool to apportioning the diversity across multiple scales and test whether each scale harbors more or less diversity than what would be expected by the random assignment of individuals to sample units. This study assessed alpha and beta diversities of nematodes in five spatial scales (from cm to km). The importance of environmental and spatial determinants of variation in nematodes composition (within and between lakes) was also evaluated. Morphospecies richness was used as a metric to estimate diversity. Using available literature data, observed Nematoda diversity was compared to patterns of diversity described to unicellular organisms with the same size (smaller than 2 mm). It was expected that a high alpha diversity in the lowest spatial scales, as described to protist species, and low beta diversity. Additionally, environmental differences between sites should explain higher variation in Nematoda composition than geographical distance. A total of 13,358 individuals belonging to 59 morphospecies were obtained. Additive partitioning showed that the importance of beta diversity at the higher scales was higher than expected. Using partial Canonical Correspondence Analysis (pCCA), it was found that environmental components (26.95%) explained more variation in community structure than spatial components (9.93%). In relation to known patterns of diversity of protists, local species richness (alpha diversity) of nematodes was low compared to their relative high worldwide richness. Moreover, nematodes tend to shown stronger habitat associations than protists, as usually observed for large multicellular organisms.

A partição aditiva da diversidade tem recebido cada vez mais atenção dos ecólogos, sendo utilizada como uma abordagem para fracionar a diversidade ao longo de múltiplas escalas. A abordagem permite ainda testar se a diversidade em cada uma das escalas é maior ou menor do que o esperado segundo uma distribuição de indivíduos ao acaso nas unidades amostrais. Este trabalho avalia a diversidade alfa e beta de nematódeos em cinco escalas espaciais (de cm a km). A importância de componentes ambientais e geográficos (dentro de lagoas e entre lagoas) na diversidade desses organismos também é estimada. Como medida de diversidade utilizou-se a riqueza de morfotipos. Através de dados da literatura, comparou-se a diversidade de Nematoda com os padrões de diversidade descritos para organismos unicelulares de mesmo tamanho (menores de 2 mm). A expectativa era que a assembléia de nematódeos apresentasse uma alta diversidade alfa nas escalas espaciais inferiores, como ocorre para protistas, e valores baixos para diversidade beta, uma vez que a variação na composição da nematofauna refletiria principalmente mudanças nas características ambientais. Foram registrados 13.358 indivíduos e 59 morfoespécies de nematódeos. A partição aditiva da diversidade revelou que a importância da diversidade beta nas escalas maiores (dentro e entre ambientes e entre lagoas) foi maior que o esperado. Através da Análise de Correspondência Canônica Parcial (pCCA), verificou-se que componentes ambientais explicaram 26,95% da variação na composição da nematofauna, enquanto componentes espaciais explicaram 9,93%. Os resultados indicam que nematódeos, ao contrário dos protistas, apresentaram uma baixa riqueza de espécies local (diversidade alfa), apesar de sua alta diversidade de espécies global. Além do mais, parece haver uma seleção de habitat por parte da nematofauna, o que é normalmente verificado para organismos multicelulares e de maior tamanho. / Additive diversity partitioning has received increasing attention of ecologists as a tool to apportioning the diversity across multiple scales and test whether each scale harbors more or less diversity than what would be expected by the random assignment of individuals to sample units. This study assessed alpha and beta diversities of nematodes in five spatial scales (from cm to km). The importance of environmental and spatial determinants of variation in nematodes composition (within and between lakes) was also evaluated. Morphospecies richness was used as a metric to estimate diversity. Using available literature data, observed Nematoda diversity was compared to patterns of diversity described to unicellular organisms with the same size (smaller than 2 mm). It was expected that a high alpha diversity in the lowest spatial scales, as described to protist species, and low beta diversity. Additionally, environmental differences between sites should explain higher variation in Nematoda composition than geographical distance. A total of 13,358 individuals belonging to 59 morphospecies were obtained. Additive partitioning showed that the importance of beta diversity at the higher scales was higher than expected. Using partial Canonical Correspondence Analysis (pCCA), it was found that environmental components (26.95%) explained more variation in community structure than spatial components (9.93%). In relation to known patterns of diversity of protists, local species richness (alpha diversity) of nematodes was low compared to their relative high worldwide richness. Moreover, nematodes tend to shown stronger habitat associations than protists, as usually observed for large multicellular organisms.

A partição aditiva da diversidade tem recebido cada vez mais atenção dos ecólogos, sendo utilizada como uma abordagem para fracionar a diversidade ao longo de múltiplas escalas. A abordagem permite ainda testar se a diversidade em cada uma das escalas é maior ou menor do que o esperado segundo uma distribuição de indivíduos ao acaso nas unidades amostrais. Este trabalho avalia a diversidade alfa e beta de nematódeos em cinco escalas espaciais (de cm a km). A importância de componentes ambientais e geográficos (dentro de lagoas e entre lagoas) na diversidade desses organismos também é estimada. Como medida de diversidade utilizou-se a riqueza de morfotipos. Através de dados da literatura, comparou-se a diversidade de Nematoda com os padrões de diversidade descritos para organismos unicelulares de mesmo tamanho (menores de 2 mm). A expectativa era que a assembléia de nematódeos apresentasse uma alta diversidade alfa nas escalas espaciais inferiores, como ocorre para protistas, e valores baixos para diversidade beta, uma vez que a variação na composição da nematofauna refletiria principalmente mudanças nas características ambientais. Foram registrados 13.358 indivíduos e 59 morfoespécies de nematódeos. A partição aditiva da diversidade revelou que a importância da diversidade beta nas escalas maiores (dentro e entre ambientes e entre lagoas) foi maior que o esperado. Através da Análise de Correspondência Canônica Parcial (pCCA), verificou-se que componentes ambientais explicaram 26,95% da variação na composição da nematofauna, enquanto componentes espaciais explicaram 9,93%. Os resultados indicam que nematódeos, ao contrário dos protistas, apresentaram uma baixa riqueza de espécies local (diversidade alfa), apesar de sua alta diversidade de espécies global. Além do mais, parece haver uma seleção de habitat por parte da nematofauna, o que é normalmente verificado para organismos multicelulares e de maior tamanho. / Additive diversity partitioning has received increasing attention of ecologists as a tool to apportioning the diversity across multiple scales and test whether each scale harbors more or less diversity than what would be expected by the random assignment of individuals to sample units. This study assessed alpha and beta diversities of nematodes in five spatial scales (from cm to km). The importance of environmental and spatial determinants of variation in nematodes composition (within and between lakes) was also evaluated. Morphospecies richness was used as a metric to estimate diversity. Using available literature data, observed Nematoda diversity was compared to patterns of diversity described to unicellular organisms with the same size (smaller than 2 mm). It was expected that a high alpha diversity in the lowest spatial scales, as described to protist species, and low beta diversity. Additionally, environmental differences between sites should explain higher variation in Nematoda composition than geographical distance. A total of 13,358 individuals belonging to 59 morphospecies were obtained. Additive partitioning showed that the importance of beta diversity at the higher scales was higher than expected. Using partial Canonical Correspondence Analysis (pCCA), it was found that environmental components (26.95%) explained more variation in community structure than spatial components (9.93%). In relation to known patterns of diversity of protists, local species richness (alpha diversity) of nematodes was low compared to their relative high worldwide richness. Moreover, nematodes tend to shown stronger habitat associations than protists, as usually observed for large multicellular organisms.

Changes in abundance of interactive species can have cascading, community-wide effects (Soule et al. 2003). Raccoons (Procyon lotor) prey on a competitor for marine turtle eggs, the Atlantic ghost crab (Ocypode quadrata). Conservation of marine turtles often includes managing raccoons-the most obvious egg predator-which may have broader ecological effects, and unknown effects on egg predation. Neither the relationship between raccoons and ghost crab density nor the effects of ghost crab density on egg predation are well understood. I studied raccoon-ghost crab interactions and the effects of environmental variation on their activity during the 2007 marine turtle nesting season on Canaveral National Seashore, FL. My goal was to model predator activity and identify efficient management strategies to reduce egg predation. Raccoon activity increased with increasing habitat diversity and edge of the dominant cover type, coastal strand. Raccoon activity increased locally and became less variable near segments of beach accessed for human recreation, but activity was greater on undeveloped beach, where habitat diversity and edge were greater. Ghost crab density and size were primarily affected by sand characteristics and recreation but decreased with increasing raccoon activity in June, which may have contributed to sustained declines in ghost crab density. Hatching success of marine turtles decreased with increasing ghost crab egg predation, suggesting ghost crabs are an important cause of egg mortality and not merely scavengers on unhatched eggs. Egg predation by ghost crabs was unrelated to ghost crab density or size, likely a result of monitoring limitations, but raccoon activity increased with increasing egg predation by ghost crabs, supporting previous research and experimental evidence suggesting ghost crabs can facilitate secondary nest predation by raccoons. This indirect interaction has strong implications for marine turtle conservation, because its strength may increase with increasing ghost crab density, potentially negating the effects of raccoon removal.

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