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Understanding the Genetic Consequences of Rapid Range Expansion: A Case Study Using the Invasive Microstegium vimineum Trin. (Poaceae)Baker, Stephen 24 July 2009 (has links)
Global temperature changes are predicted to influence the distributions of plants and can have significant consequences for population genetic structure. Both the nature of these consequences and the processes that shape them are of interest for both conservation genetics and the development of realistic management programs. Rapid range expansion occurs on short temporal scales not conducive to conventional phylogeographical analyses. This paper presents the findings from a population genetic study of the invasive grass Microstegium vimineum Trin. A. Camus throughout the James River Basin of Virginia. Genotypic analysis using Amplified Fragment Length Polymorphism (AFLP) molecular markers were used to test for evidence of rapid range expansion and the effects associated with colonization and spread of Microstegium vimineum. Within the James River Basin three genetically distinct clusters were identified that were not clearly associated with natural geographic boundaries and recent founder events were also inferred. The James River Basin also appears to act as a corridor for long-distance dispersal events. These findings contribute to our knowledge of the genetic consequences of rapid range expansion for invasive species, and more importantly, native species. Contrary to several studies, the present research also indicates that long-distance dispersal is not rare and can be a major contributor to the genetic structure following range expansion.
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Physiological and Behavioral Mechanisms of Range Expansion in the House Sparrow (Passer domesticus)Liebl, Andrea Lyn 01 January 2013 (has links)
Introduced species cause both considerable ecological and economic damage every year. However, not much is known about how certain species are able to establish and spread beyond the site of initial introduction, whereas others do not. Species undergoing range expansion following an introduction may prove to be a valuable resource to invasion biology, but may also be informative in light of species' responses to changing environments (i.e. global climate change). Here, I took advantage of an ongoing range expansion of an introduced vertebrate species. House sparrows (Passer domesticus) were introduced to Mombasa, Kenya in the 1950s and have subsequently expanded their range northwest-ward and now occupy most major cities in Kenya. By comparing older, established populations (i.e. those in Mombasa) with more recently colonized populations at the range edge, it might be possible to determine some of the mechanisms that underlie range expansion in some species and/or populations. In Chapter 1, the background and ideas that motivated the rest of the dissertation is summarized. In Chapter 2, I studied how exploration and glucocorticoids (a hormone released in response to stressors) changed throughout the range expansion. Exploration was greater at the range edge, which is likely to ensure greater discovery of novel resources. Glucocorticoids released in response to restraint were also highest at the range edge, which might facilitate resolution of stressors in unpredictable environments. However, chronically elevated levels of glucocorticoids are often considered maladaptive, unless an individual can appropriately cope with them. Therefore, in Chapter 3, I characterized glucocorticoid receptors (i.e. mineralocorticoid receptor (MR) and glucocorticoid receptor (GR)) in the hippocampus, an area responsible for negative feedback of glucocorticoids as well as induction of behavioral and physiological response to stressors. I found that MR density was lower relative to GR density at the range edge compared to the site of introduction (Mombasa). I speculate this pattern is a mechanism to resolve the elevated levels of glucocorticoids at the range edge. Taken together, these results indicate that individuals at the range edge have a strong glucocorticoid response to stressors to induce a rapid, strong response to resolve stressors. Subsequently, in Chapter 4, I examined the potential mechanisms of phenotypic change among Kenyan house sparrows. Typically, following an introduction event, genetic diversity undergoes a bottleneck and is greatly reduced compared to the source population; as such, genetic evolution as the main driver of changing phenotypes throughout the range expansion is unlikely. We therefore hypothesized that epigenetic mechanisms (e.g. DNA methylation) may compensate for the expected reduced genetic diversity following an introduction. Although there was no pattern of epigenetic variation among cities (i.e. variation did not increase nor decrease further from the site of introduction), epigenetic variation increased as genetic inbreeding increased (a sign of reduced genetic diversity and bottlenecks), suggesting epigenetic modifications may compensate for reduced genetic diversity following an introduction event. Overall, patterns of phenotypic variation emerged dependent on age of the population- these patterns may prove to be important in other vertebrate range expansions as well. Surprisingly, epigenetic diversity did not correlate with phenotypic variation among populations; however, within-individual studies may reveal epigenotypes are related to certain behavioral or physiological phenotypes. In the future, studies should be designed to address how phenotypic differences arise despite relatively low genetic diversity and overall high genetic admixture among individuals. In Kenyan house sparrows, maintenance of high levels of flexibility and differential developmental influences may be important factors that lead to varying phenotypes dependent on time since colonization.
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A molecular assessment of range expansion of the northern or virile crayfish (Orconectes virilis), crayfish-based community co-structure, and phylogeny of crayfish-affiliated symbiontsWilliams, Bronwyn W. Unknown Date
No description available.
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A molecular investigation of dispersal, drift and selection to aid management of an invasion in progressRollins, Lee Ann, Biological, Earth & Environmental Sciences, Faculty of Science, UNSW January 2009 (has links)
Invasive species are problematic but their control can be difficult. When the history and dynamics of invasive populations are unknown, analytical techniques utilising genetic data can provide information to management. The application of these techniques has typically been limited to species with restricted dispersal or to localised geographic scales. Here these techniques are used in conjunction with traditional approaches to study the invasion of a highly vagile species over a continental scale. Originally introduced to eastern Australia, the common starling (Sturnus vulgaris) is expanding westward and has reached the southeast agricultural region of Western Australia (WA). Spatial, temporal and museum samples representing historical incursions into WA were used in genetic analyses to answer questions important to WA management agencies. Where possible, multiple marker classes were used to evaluate their relative ability to address these questions, including microsatellites, mitochondrial DNA (mtDNA), and a nuclear gene. Between two and four genetic groups were identified in Australia, and the localities on the edge of the range expansion (ERE) were consistently genetically differentiated from all others. Levels of genetic exchange between groups appeared to be low, suggesting that localised control may be effective. Analyses of historical samples indicated patterns of genetic exchange are temporally stable. This suggests that starlings will continue to arrive from the east, requiring vigilance from management. Consistently, a negative relationship was found between genetic diversity and date of first record, which may help in the future to distinguish ineffective surveillance from recent colonisations. Genetic evidence of female-biased dispersal indicated that control strategies preferentially targeting females may more efficiently limit dispersal than those targeting both sexes equally. Variants private to particular genetic groups were identified; tracking the spread of these variants may assist future monitoring programs in understanding ongoing exchange between groups. One mtDNA variant private to ERE localities showed dramatic temporal change, which could not be adequately explained by genetic drift or admixture, but may be explained by selection. Microsatellites were most useful in determining origins and identifying dispersers, mtDNA sequences provided a unique tool for ongoing monitoring of dispersal, and nuclear sequences had high levels of gene diversity and resolution of population structure.
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Trait Variation in an Everglades Invasive Species: Life histories, Boldness, and Dispersal in the African JewelfishLopez, Diana P 01 January 2011 (has links)
Invasive range expansion is correlated to life- history variation, boldness and dispersal behavior. The invasion of the African Jewelfish in Everglades National Park provides an opportunity to test life-history trait variation, boldness and dispersal behavior in the invasion success of this species.
My study examined variation in somatic traits, boldness, and dispersal of jewelfish across their invaded range. Life histories were examined on wild individuals. Boldness and dispersal were tested in outdoor experimental tanks. Tested populations from the invasion front have higher somatic traits, but they were not bolder than longer established populations.
Understanding the underlying mechanisms of invasions are key for the development of strategies looking to contain invaders and prevent their spread.
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The Expansion of Black Vultures, Coragyps atratus, into Southwestern OhioNellums, Elizabeth Kay 24 April 2006 (has links)
No description available.
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Population genetic structure and species displacement during range expansion of invasive geckosShort, Kristen January 2010 (has links)
No description available.
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Landscape ecology of the capybara (Hydrochoerus hydrochaeris) in the Chaco region of ParaguayCampos Krauer, Juan Manuel January 1900 (has links)
Doctor of Philosophy / Department of Biology / Samantha Wisely / Habitat fragmentation and destruction are the most ubiquitous and serious
environmental threats confronting the long-term survival of plant and animal species
worldwide. However, some native or exotic species can take advantages of these
alterations and expand their range, placing endemic species at risk of extinction by
changing the composition of biotic communities and altering ecosystem.
Capybara (Hydrochoerus hydrochaeris) are a widely distributed rodent
throughout most of South and Central America, but restricted to areas of standing water.
As the Gran Chaco ecosystem of Paraguay has been converted from dry tropical forest to
pastureland, I hypothesized that this habitat alteration created potential for invasion by
capybara into newly fragmented areas. I used ecological niche modeling to generate
hypotheses about how the distribution of capybara has been affected by land use change,
and tested those hypotheses with phylogeographic analyses. To understand the
mechanisms that have allowed the invasion, I investigated home range, habitat use and
thermoregulation of capybara via radiotelemetry in a deforested area in which capybara
had recently invaded.
Genetic analyses confirm a rapid range expansion scenario with evidence of
secondary contact between two distinct phylogroups which had previously been disjunct.
Modeling results indicated that conversion of forest to pastureland allowed the expansion
to occur. Capybara selected water significantly more than it was available to them, and
avoided shrub forest. I found a significant positive correlation between body temperature
and distance from water, and a significant negative correlation between distance from
water and Chaco ambient temperature. Capybara proximity to water appeared to be
tightly linked to body thermoregulation. These results suggest that although capybara
have expanded into the Chaco forest as it is converted to pastureland, the presence of
permanent water sources in those pastures are the mechanism that allow capybara to
persist in this habitat.
This is the first study to characterize capybara in a xeric habitat without a year
round water source, and scarce natural grasslands. My results show how anthropogenic
habitat modification has allowed capybara to thrive. Understanding how capybara invade
and utilize the deforested Central Dry Chaco will provide valuable information for the
future management of the species and the Chaco ecosystem.
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Como o comportamento animal pode influenciar a distribuição das espécies / The influence of animal behavior on species distributionsLima, Herlander Correia de 21 March 2018 (has links)
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Previous issue date: 2018-03-21 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Research in animal personality is increasing our understanding of what prevents a species from
colonizing new areas, which is one of the outstanding questions in biogeography. Some
behavioral types can perform better than others in specific stages involved in range expansion.
For example, a high exploratory behavior increases the chances of finding new resources in novel
environments. However, inconsistent results in the literature hindered a definite recognition of the
role of animal personalities on species distributions. I collected data available in the literature and
performed a bayesian meta-analysis to assess which behavioral types are driving range expansion
in the following biogeographical processes: dispersal, migration and invasion. I used several
moderators to try to discern context-dependencies in effect sizes. A hierarchical model, with
effect sizes nested within studies, revealed that more exploratory and bolder behaviors facilitate
range expansion. Also, I found that invasive individuals are more likely to be more exploratory
and more active than natives, while dispersers are generally bolder and more exploratory than
non-dispersers. Yet, the low study sample size obtained for analysis stresses the need to conduct
more primary studies. Results highlight the role of behavioral traits in species distributions and
increase our knowledge about which ecological characteristics might prepare species to endure
the current global environmental challenges. / A pesquisa em personalidade animal está aumentando o nosso conhecimento sobre o que
previne uma espécie de colonizar novas áreas, sendo esta uma das principais questões em
biogeografia. Alguns tipos de comportamento podem resultar em melhor desempenho que outros
em específicos estágios de expansão do território. Por exemplo, um comportamento mais
exploratório facilita a descoberta de recursos em um novo meio. Contudo, resultados
inconsistentes na literatura estão dificultando um reconhecimento do papel da personalidade
animal na distribuição das espécies. Coletei dados da literatura e realizei uma meta-análise
bayesiana para determinar que tipos de comportamento são responsáveis pela expansão do
território através dos processos biogeográficos de: dispersão, invasão e migração. Fiz ainda uso
de vários moderadores na tentativa de identificar contexto-dependências nos tamanhos de efeito.
Em um modelo hierárquico, usando tamanhos de efeito aninhados dentro dos estudos, mostro que
um comportamento mais ousado e mais exploratório facilita o sucesso na expansão do território.
Para além disso, eu demonstro que invasores são mais exploratórios e mais ativos que nativos, e
dispersores são mais exploratórios e ousados que não-dispersores. Contudo, o baixo tamanho
amostral obtido para as análises demonstra a necessidade de conduzir mais estudos primários. Os
resultados realçam o papel dos traços comportamentais na distribuição das espécies e aumentam
o nosso conhecimento sobre que características ecológicas podem preparar as espécies para
resistir aos desafios das mudanças ambientais.
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Ecological and evolutionary analyses of range limits and biodiversity patternsBehrman, Kathrine Delany 04 March 2014 (has links)
The goal of this dissertation is to further our understanding of how spatially heterogeneous landscapes may impact the formation of range boundaries that then aggregate to form large-scale biodiversity patterns. These patterns have been analyzed from many different perspectives by ecologists, evolutionary biologist, and physiologists using a variety of different theoretical, statistical, and mechanistic models.
For some species, there is an obvious abrupt change in the environment causing a range boundary. Other environments change gradually, and it is unclear why species fail to adapt and expand their range. The first chapter develops a novel theoretical model of how the establishment of new mutations allows for adaptation to an environmental gradient, when there is no genetic variation for the trait that limits the range. Shallow environmental gradients favor mutations that arise nearer to the range margin, have smaller phenotypic effects, and allow for proportionately larger expansions than steep gradients. Mutations that allow for range expansion tend to have large phenotypic effects causing substantial range expansions.
Spatial and temporal variation in climatic and environmental variables is important for understanding species response to climate change. The second chapter uses a mechanistic model to simulate switchgrass (Panicum virgatum L.) productivity across the central and eastern U.S. for current and future climate conditions. Florida and the Gulf Coast of Texas and Louisiana have the highest predicted current and future yields. Regions where future temperature and precipitation are anticipated to increase, larger future yields are expected.
Large-scale geographic patterns of biodiversity are documented for many taxa. The mechanisms allowing for the coexistence of more of species in certain regions are poorly understood. The third chapter employs a newly developed wavelet lifting technique to extract scale-dependent patterns from irregularly spaced two-dimensional ecological data and analyzes the relationship between breeding avian richness and four energy variables. Evapotranspiration, temperature, and precipitation are significant predictors of richness at intermediate-to-large scales. Net primary production is the only significant predictor across small-to-large scales, and explains the most variation in richness (~40%) at an intermediate scale. Changes in the species-energy relationship with scale, may indicate a shift in the mechanism governing species richness. / text
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