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(1 - 7 of 7)
- Title
- ADAPTIVE RESPONSES OF BRANCHIAL MORPHOLOGY TO HYPOXIA IN THE NEOTROPICAL ELECTRIC FISH GENUS BRACHYHYPOPOMUS.
- Creator
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Pathak, Leilani, Crampton, William, University of Central Florida
- Abstract / Description
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Many tropical aquatic environments worldwide are characterized by intermittent or prolonged hypoxia (low dissolved oxygen). Nevertheless, many tropical freshwater fishes are able to inhabit these challenging environments via a range of morphological, physiological and behavioral adaptations. Brachyhypopomus is a diverse genus of weakly electric fishes represented by 28 known species distributed from Panama to Argentina. 17 species are restricted to permanently normoxic habitats (blackwater...
Show moreMany tropical aquatic environments worldwide are characterized by intermittent or prolonged hypoxia (low dissolved oxygen). Nevertheless, many tropical freshwater fishes are able to inhabit these challenging environments via a range of morphological, physiological and behavioral adaptations. Brachyhypopomus is a diverse genus of weakly electric fishes represented by 28 known species distributed from Panama to Argentina. 17 species are restricted to permanently normoxic habitats (blackwater rivers and terra firme streams), eight species are restricted to seasonally or perennially hypoxic habitats (whitewater floodplains of large tropical rivers or permanent swampy habitats), and three species are eurytopic (occur in both seasonally hypoxic and normoxic habitats). These habitat distributions offer the opportunity to explore both species- and population-level variation in adaptive responses to hypoxia. Across 25 of the 28 known species in the genus (for which specimens were available), one- and two-way ANOVA was used to correlate total gill filament length (a metric of gill surface area) with lifestyle -divided into four categories: 1) stenotopic species (i.e. species occurring in a narrow range of habitats) restricted to hypoxic habitats; 2) stenotopic species restricted to normoxic habitats; 3) populations of eurytopic species from hypoxic habitats, and; 4) populations of eurytopic species from normoxic habitats. One-way ANOVA revealed that populations of eurytopic species from hypoxic habitats had significantly larger total gill filament lengths than stenotopic species from the same habitat (P = 0.0169). Likewise, populations of eurytopic from normoxic habitats had significantly larger total gill filament lengths than stenotopic species from normoxic habitats (P < 0.005). Two-way ANOVA showed that eurytopic species had significantly larger total gill filament lengths than stenotopic species, independent of the disparity in total gill filament length associated with either hypoxic or normoxic habitats. Results indicate a strong correlation between gill surface area and oxygen-habitat among species and populations, which supports the hypothesis that an enlarged gill surface area increases oxygen uptake and serves as an adaptive response to seasonal hypoxia.
Show less - Date Issued
- 2011
- Identifier
- CFE0003651, ucf:48822
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003651
- Title
- Environmental correlates of sensory sampling rate in the electrosensory system of Neotropical electric fishes.
- Creator
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Correa Roldan, Ericka, Crampton, William, Cook, Geoffrey, Correa, Sandra, University of Central Florida
- Abstract / Description
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The nocturnally-active freshwater Neotropical gymnotiform electric fish generate weak electric organ discharges (EODs) that are detected by electroreceptors to facilitate active electroreception (object detection and communication - including species recognition). The EOD rate of 'pulse-type' species varies among individuals as a function of activity rate and during sexual or agonistic interactions. The extent to which EOD rate varies between and within species in natural conditions, and the...
Show moreThe nocturnally-active freshwater Neotropical gymnotiform electric fish generate weak electric organ discharges (EODs) that are detected by electroreceptors to facilitate active electroreception (object detection and communication - including species recognition). The EOD rate of 'pulse-type' species varies among individuals as a function of activity rate and during sexual or agonistic interactions. The extent to which EOD rate varies between and within species in natural conditions, and the ecological and evolutionary factors that influence such variation are poorly known. EOD rate is presumed to represent a measure of sensory sampling rate, and therefore we hypothesized that water flow velocity may correlate positively to EOD rate variation (both between and within species). To test this hypothesis, we made nocturnal EOD-rate recordings of 862 non-breeding individuals of nine common species in rainforest streams of the upper Amazon. These recordings were accompanied by measurements of additional parameters hypothesized to influence intraspecific (but not interspecific) variation in pulse rate by influencing activity rate. These parameters included conductivity and turbidity (proxies for recent rainfall), temperature and dissolved oxygen (a possible metabolic constraint on signaling), body size (representing ontogeny), and moonlight intensity (a metric of predation risk). Using multiple regression in the form of linear mixed effect models, and model selection, we determined that none of these variables explain interspecific variation in EOD rate (-) suggesting that other factors such as species recognition or non-adaptive drift represent more important ultimate drivers of interspecific variation in pulse rate. However, at the intraspecific level, we reported a substantial reduction in mean pulse rate on nights with strong moonlight in two species, Brachyhypopomus sullivani and Gymnorhamphichthys rondoni. In two other species, Brachyhypopomus beebei and Brachyhypopomus verdii, we reported elevated pulse rate during periods of increased conductivity and/or turbidity that followed rainfall and consequent flooding of ephemeral swamps adjacent to terra-firme streams.
Show less - Date Issued
- 2019
- Identifier
- CFE0007618, ucf:52525
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007618
- Title
- Beyond building a tree: Phylogeny of pitvipers and exploration of evolutionary patterns.
- Creator
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Fenwick, Allyson, Parkinson, Christopher, Hoffman, Eric, Crampton, William, Wiens, John, University of Central Florida
- Abstract / Description
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As generic and higher-scale evolutionary relationships are increasingly well understood, systematists move research in two directions: 1) understanding species-level relationships with dense taxon sampling, and 2) evaluating evolutionary patterns using phylogeny. In this study I address both foci of systematic research using pitvipers, subfamily Crotalinae. For direction one, I evaluate the relationships of 96% of pitvipers by combining independent sets of molecular and phenotypic data. I...
Show moreAs generic and higher-scale evolutionary relationships are increasingly well understood, systematists move research in two directions: 1) understanding species-level relationships with dense taxon sampling, and 2) evaluating evolutionary patterns using phylogeny. In this study I address both foci of systematic research using pitvipers, subfamily Crotalinae. For direction one, I evaluate the relationships of 96% of pitvipers by combining independent sets of molecular and phenotypic data. I find the inclusion of species with low numbers of informative characters (i.e. less than 100) negatively impacts resolution of the phylogeny, and the addition of independent datasets has no effect on or a small benefit to confidence in estimated evolutionary relationships. Combined evidence is extremely useful in evaluating taxonomy; I use it with South American bothropoid pitvipers. Previous work found the genus Bothrops paraphyletic, but no study had included enough species to propose a taxonomic resolution. I resolve the relationships of 90% of bothropoid pitvipers, and support the paraphyly of Bothrops as previously defined, but find it consists of three well-supported clades distinguished by distinct habitats and geographic ranges. I propose the division of Bothrops sensu lato into three genera.To address research direction two, I investigate the change in reproductive mode from egg-laying (oviparity) to livebearing (viviparity) in vipers, as well as the expansion of pitvipers through South America. I resolve the phylogeny and the divergence times for subgroups of interest then use model comparison and ancestral character state or geographic range estimation to trace the evolution of reproductive mode or geographic range across evolutionary history. For vertebrates, the predominant explanation for the evolution of reproductive mode is Dollo's Law of unidirectional evolution. This law has been challenged for a number of characters in different systems, but the phylogenetic methods that found those violations were criticized. I find support for unidirectional evolution in two analyses and rejection of it in others, and therefore do not reject Dollo's Law for the evolution of reproductive mode in vipers. In the case of geographic range, dozens of hypotheses have been proposed to explain the great biodiversity in South America, but tests of these hypotheses are lacking. I define specific time- and space-based predictions for seven hypotheses based on geological and climatic events (-) uplift of the Andes Mountains, saltwater inundation of inland areas, change in river flow, and Pleistocene climate changes. I find some support for half of the hypotheses, including one allopatric, one parapatric, and one based on climate change. I conclude that the evolution of South American pitvipers is extremely complex. Through fulfillment of both systematic research directions, I generated new knowledge about pitvipers and evolutionary processes. My methods of evaluating evolutionary patterns provide frameworks for different research questions in these areas, and I suggest that other researchers apply similar techniques to evaluate other portions of the Tree of Life.
Show less - Date Issued
- 2012
- Identifier
- CFE0004535, ucf:49236
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004535
- Title
- Life history response to infection and the potential for dishonest signals in the ground cricket, Allonemobius socius.
- Creator
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Copeland, Emily, Fedorka, Kenneth, Hoffman, Eric, Crampton, William, University of Central Florida
- Abstract / Description
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In order to maximize fitness, individuals must partition their limited resources among competing physiological processes, creating negative statistical associations between processes known as (")life-history trade-offs("). Evidence indicates that individuals tend to decrease their reproductive investment when confronted with a significant immunological challenge in order to increase investment in immune defense. This trade-off is often accompanied by a significant decrease in the sexual...
Show moreIn order to maximize fitness, individuals must partition their limited resources among competing physiological processes, creating negative statistical associations between processes known as (")life-history trade-offs("). Evidence indicates that individuals tend to decrease their reproductive investment when confronted with a significant immunological challenge in order to increase investment in immune defense. This trade-off is often accompanied by a significant decrease in the sexual signal, which provides an honest signal of the male's infection status to potential mates. However, if individual residual reproductive value is low, they may instead increase their reproductive investment to maximize reproductive success before the end of their life (a.k.a. terminal investment). Here, we investigate the potential for terminal investment in the ground cricket Allonemobius socius by inoculating males with varying dosages of an immune challenge. We predicted that both high dose and advanced male age would induce terminal investment. Furthermore, we predicted that terminally investing males would produce a dishonest signal by increasing their signaling effort. We found that upon infection We found that upon infection, young males and old males differentially alter their reproductive strategy. Young males exhibited the classic deceleration of reproductive effort. However, old males increased their calling song energetics and decreased their parental investment (nuptial gift size), suggesting that old males are dishonestly signaling their condition to the female.
Show less - Date Issued
- 2012
- Identifier
- CFE0004529, ucf:49249
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004529
- Title
- Bayesian Model Selection for Classification with Possibly Large Number of Groups.
- Creator
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Davis, Justin, Pensky, Marianna, Swanson, Jason, Richardson, Gary, Crampton, William, Ni, Liqiang, University of Central Florida
- Abstract / Description
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The purpose of the present dissertation is to study model selection techniques which are specifically designed for classification of high-dimensional data with a large number of classes. To the best of our knowledge, this problem has never been studied in depth previously. We assume that the number of components p is much larger than the number of samples n, and that only few of those p components are useful for subsequent classification. In what follows, we introduce two Bayesian models...
Show moreThe purpose of the present dissertation is to study model selection techniques which are specifically designed for classification of high-dimensional data with a large number of classes. To the best of our knowledge, this problem has never been studied in depth previously. We assume that the number of components p is much larger than the number of samples n, and that only few of those p components are useful for subsequent classification. In what follows, we introduce two Bayesian models which use two different approaches to the problem: one which discards components which have "almost constant" values (Model 1) and another which retains the components for which between-group variations are larger than within-group variation (Model 2). We show that particular cases of the above two models recover familiar variance or ANOVA-based component selection. When one has only two classes and features are a priori independent, Model 2 reduces to the Feature Annealed Independence Rule (FAIR) introduced by Fan and Fan (2008) and can be viewed as a natural generalization to the case of L (>) 2 classes. A nontrivial result of the dissertation is that the precision of feature selection using Model 2 improves when the number of classes grows. Subsequently, we examine the rate of misclassification with and without feature selection on the basis of Model 2.
Show less - Date Issued
- 2011
- Identifier
- CFE0004097, ucf:49091
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004097
- Title
- Phylogenetic Community Structure of Aquatic Beetle Assemblages in a Multi-Wetland Experiment.
- Creator
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Kelly, Sandor, Jenkins, David, Parkinson, Christopher, Crampton, William, Song, Hojun, University of Central Florida
- Abstract / Description
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Phylogenetic Community Structure (PCS) metrics are becoming more common in community ecology. PCS metrics estimate the phylogenetic relatedness among members of an ecological community or assemblage. If ecological traits are conserved, then phylogenetic clustering (i.e., taxa are more closely related than expected by chance) indicates habitat filtering as the key process in community assembly. On the other hand, a pattern of phylogenetic overdispersion (i.e., taxa are more distantly related...
Show morePhylogenetic Community Structure (PCS) metrics are becoming more common in community ecology. PCS metrics estimate the phylogenetic relatedness among members of an ecological community or assemblage. If ecological traits are conserved, then phylogenetic clustering (i.e., taxa are more closely related than expected by chance) indicates habitat filtering as the key process in community assembly. On the other hand, a pattern of phylogenetic overdispersion (i.e., taxa are more distantly related than expected by chance) suggests competition is dominant. Most studies to date have used PCS of unmanipulated ecosystems, but the value of PCS metrics will be best revealed in experiments. This project used PCS for aquatic beetle (Coleoptera) assemblages in experimentally manipulated seasonal wetlands on a cattle ranch in south-central Florida, and compared PCS metrics to standard ecological metrics. Wetlands were experimentally treated with all combinations of pasture management, fencing to exclude cattle, and controlled burning during 2006-2009. Beetle assemblages in fenced wetlands were significantly more overdispersed compared to non-fenced wetlands, suggesting that this treatment decreases habitat filtering, causing competition to become the dominant process in community formation. There was also a significant pasture x fence x burn interaction effect, with assemblages in wetlands differing in PCS depending on what combination of the three treatments were applied. Phylogenetic Diversity (PD (-) a measure of branch length of a community or assemblage on a phylogenetic tree) was highly correlated with genera richness (number of genera), and these metrics along with the expected number of genera (D (-) an ecological diversity index) found significant differences among burn treatments and a pasture x burn interaction. The results of this study indicate that PCS metrics complement classical ecological methods and should be widely applied.
Show less - Date Issued
- 2012
- Identifier
- CFE0004394, ucf:49388
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004394
- Title
- Reproductive life history and signal evolution in a multi-species assemblage of electric fish.
- Creator
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Waddell, Joseph, Crampton, William, Fedorka, Kenneth, Quintana-Ascencio, Pedro, Stoddard, Philip, University of Central Florida
- Abstract / Description
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Animals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They...
Show moreAnimals that co-occur in sympatry with multiple closely-related species use reproductive mate attraction signals not only to assess the quality of a potential conspecific mate (sexual selection), but also to discriminate conspecifics from heterospecifics (species recognition). However, the extent to which sexual selection and species recognition may interact, or even conflict, is poorly known. Neotropical electric fish offer unrivaled opportunities for understanding this problem. They generate simple, stereotyped mate attraction signals that are easy to record and quantify, and that are well-understood from the neurobiological perspective. Additionally, they live in electrically-crowded environments, where multiple congeners live and reproduce in close proximity. This dissertation reports an investigation of electric signal diversity and reproductive life history in a nine-species assemblage of the electric fish genus Brachyhypopomus from the upper Amazon. A year-long quantitative sampling program yielded a library of electric signal recordings from (>)3,000 individuals and an accompanying collection of preserved specimens from which suites of informative life history traits were measured. These data were used to understand basic reproductive biology, and to describe sexually dimorphic and interspecific diversity in electric signals. By integrating approaches from ecology, physiology, and evolutionary biology, novel perspectives are provided on: 1. how sexual selection and species recognition interact to shape signal diversity and the occupation of signal space in multi-species animal communities; 2. how extreme seasonal variation in Amazonian ecosystems influences trade-offs in the allocation of reproductive resources (-) including mate attraction signals, and; 3. how environmental variation shapes general life-history traits in a diverse tropical animal assemblage.
Show less - Date Issued
- 2017
- Identifier
- CFE0006925, ucf:51689
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006925
