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ABSTRACT: Epigenetic mechanisms impact several phenotypic traits and may be important for ecology and evolution. The introduced house sparrow (Passer domesticus) exhibits extensive phenotypic variation among and within populations. We screened methylation in populations from Kenya and Florida to determine if methylation varied among populations, varied with introduction history (Kenyan invasion <50 years old, Florida invasion ~150 years old), and could potentially compensate for decrease genetic variation with introductions. While recent literature has speculated on the importance of epigenetic effects for biological invasions, this is the first such study among wild vertebrates. Methylation was more frequent in Nairobi, and outlier loci suggest that populations may be differentiated. Methylation diversity was similar between populations, in spite of known lower genetic diversity in Nairobi, which suggests that epigenetic variation may compensate for decreased genetic diversity as a source of phenotypic variation during introduction. Our results suggest that methylation differences may be common among house sparrows, but research is needed to discern whether methylation impacts phenotypic variation.
Genetics research international. 01/2012; 2012:979751.
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Journal of Herpetology 01/2012; 46(2):241-247. · 1.08 Impact Factor
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Diversity and Distributions 01/2012; 18:1120–1129. · 4.83 Impact Factor
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ABSTRACT: Comparison of the resource accumulation patterns exhibited by related species inhabiting disparate hydrological conditions can provide insight into how they are affected by and respond to different environments. We compared the seasonal body condition of the desert tortoise (Gopherus agassizii) in the Mojave Desert with that of the gopher tortoise (Gopherus polyphemus) in central Florida. We assessed body condition indirectly, with indices derived from the relationship between body mass and size. In turtles, variation in body mass largely reflects tissue hydration, water stored in the bladder, and food stored in the gut. Mean body condition was lower and seasonal fluctuations were of lesser amplitude in the gopher tortoise than in the desert tortoise. Over the short term, body condition of the desert tortoise is correlated strongly with rainfall, but body condition of the gopher tortoise is not. These differences between the two species are consistent with what is known about their physiology and behavior under current climatic conditions. Changing rainfall patterns may severely affect the desert tortoise. The physiological reaction of the gopher tortoise to drought conditions also may put it at substantial potential risk from climate change.
Chelonian Conservation and Biology 07/2011; · 0.91 Impact Factor
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ABSTRACT: Fire is a complex event that maintains many ecological systems. The Florida Sand Skink (Plestiodon reynoldsi) is precinctive to Florida Scrub, a habitat that is maintained by infrequent fire. We characterize the effect of fire on genetic diversity and genetic differentiation at eight microsatellite loci in the Florida Sand Skink (n=470) collected from 30 replicate sites over three 'time since last fire' categories at the Archbold Biological Station. Long unburned sites had greater allelic richness and expected heterozygosity than either recently or intermediately burned sites. More recently, burned sites had greater standard deviations of allelic richness and private allelic richness. Expected heterozygosity positively correlated with 'time since fire' (r=0.36, P=0.05) and abundance (r=0.53, P=0.002). There was a significant spatial component to genetic differentiation, and results indicate individuals rarely disperse >1 km. Genetic differentiation was positively correlated with geographic distance in long unburned units (r=0.59, P=0.04), yet this relationship was disrupted by fire in recently (r=0.00, 1) and intermediately (r= -0.81, 0.05) burned areas. Simulations indicate that demographic changes to a local population could have generated the observed differences among 'time since fire' categories. Our findings indicate that infrequent fire may be beneficial to the Florida Sand Skink and that local populations begin to recover from changes attributable to the fire after 10 years. Too frequent fires may reduce genetic diversity because it may take multiple generations for local populations to recover.
Molecular Ecology 01/2011; 20(1):56-66. · 5.52 Impact Factor
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ABSTRACT: A recent study showed that populations of the threatened Florida Sand Skink had limited loss of genetic diversity over the past 60 yr as a consequence of anthropogenic fragmentation. This study assumed that 60 yr represents 30–37 generations for the Florida Sand Skink, but a new evaluation of mark–recapture data shows that 60 yr represents only about 15 generations. This result suggests that too little time may have passed to observe the full genetic consequences of contemporary anthropogenic fragmentation in the Florida Sand Skink and reinforces similar results from other species. We suggest that snapshots of existing genetic variability in fragmented populations are limited in their ability to predict the evolutionary fate of a species unless life-history attributes of the organism are taken into account.
Journal of Herpetology 12/2010; · 1.08 Impact Factor
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ABSTRACT: 1. We investigated agonistic behaviour and associated characteristics of Sceloporus woodi (Florida scrub lizard), Sceloporus undulatus (Eastern fence lizard) and their hybrids using staged territorial encounters. 2. These Sceloporus hybrids exhibit transgressive aggression and transgressive head-girth relative to the parental species and the transgressive aggression was specifically associated with an advantage in agonistic encounters. Our results suggest a hybrid advantage in natural habitats when defending and invading territories against either parental species. 3. We further analysed general advantages in agonistic encounters across the entire three-group system to elucidate characteristics that may be advantageous under specific circumstances. Individuals with larger body size (SVL) and greater aggression had an overall advantage in agonistic encounters; however, smaller individuals could win when slightly more aggressive and fatter, and less aggressive individuals could win when slightly larger, especially with greater head-girth. 4. The extreme hybrid phenotypes likely occurred through transgressive segregation, which has been implicated as a process through which homoploid, hybrid speciation can occur. Some form of ecological divergence is necessary, however, to impede parental gene flow. Our data suggest that ecological divergence could manifest in territorial species through transgressive aggression.
Journal of Animal Ecology 08/2009; 79(1):137-47. · 4.94 Impact Factor
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ABSTRACT: We obtained demographic data on more than 60 gopher tortoise (Gopherus polyphemus) populations in Florida before the emergence of upper respiratory tract disease (URTD). We later resurveyed 10 populations to compare demographic profiles at sites where antibodies to Mycoplasma agassizii were detected subsequently and at sites where they were not. We screened for antibodies and checked for potential biases in studying URTD by determining whether individuals caught above ground were representative of a population as a whole and whether the probability of detection of seropositive (plus serologically suspect) individuals is a function of sample size. Some sites with no indication of decline had relatively high percentages of seropositive individuals, and some sites exhibiting substantial population decline had no or low percentages of seropositive individuals; therefore, our results do not unambiguously implicate the presence of URTD in the population declines. Seropositive individuals occurred at 4 sites not known previously to have them; therefore, our results indicate that exposure to Mycoplasma agassizii has been more widespread than heretofore suspected. The percentage of individuals determined to be seropositive (plus suspect) tends to be related positively to number of individuals tested and the sizes of individuals caught above ground were not always expected from the size distribution of a population; therefore, our results indicate that sampling method can influence the estimate of percentage of seropositive individuals in the population. We suggest that the simplistic conservation response that we have taken to the emergence of URTD may need to be reconsidered and that maintaining or creating conditions necessary to minimize the chance of re-emergence of URTD, to prevent URTD from reaching epidemic proportions, and to allow populations to recover from URTD is important.
Chelonian Conservation and Biology 01/2009; · 0.91 Impact Factor
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ABSTRACT: The mangrove salt marsh snake (Nerodia clarkii compressicauda) occupies a unique and disappearing habitat in much of coastal southern Florida. Given extensive habitat fragmentation and
high predation pressure in open spaces, it seems likely that populations of N. c. compressicauda consist of isolated groups of related individuals. To assess the degree of population subdivision in this species we genotyped
a total of 125 individuals from seven locations along the Florida coast at four microsatellite loci. Overall heterozygosity
was moderate (57.7%) and somewhat lower than that seen in other snake species. Population subdivision was particularly pronounced
with 19 of 21 sample pair-wise ΦST values significantly different from zero and ranging from 0.064 to 0.343 (P≤0.05). About 11 of 39 alleles were private alleles that also tended to be in high frequency in the populations where they
occurred (average frequency ~27%). The correlation of genetic and geographic distances was highly significant and positive
(r
2=0.8733 and P<0.001) with ΦST increasing by ~0.01 for every 10km of separation. Overall, salt marsh snake populations appear to be fractured into isolated
neighborhoods on the order of 50–80km. In spite of its apparent local abundance, we believe that N. c. compressicauda is in need of conservation protection. The combination of extremely low dispersal, narrow habitat requirements, and most
importantly, extensive habitat alteration resulting from coastal real estate development may mean that N. c. compressicauda is highly susceptible to population extirpation and potentially extinction.
Conservation Genetics 01/2008; 9(2):401-410. · 1.61 Impact Factor
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ABSTRACT: Minimum patch size for a viable population can be estimated in several ways. The density-area method estimates minimum patch size as the smallest area in which no new individuals are encountered as one extends the arbitrary boundaries of a study area outward. The density-area method eliminates the assumption of no variation in density with size of habitat area that accompanies other methods, but it is untested in situations in which habitat loss has confined populations to small areas. We used a variant of the density area method to study the minimum patch size for the gopher tortoise (Gopherus polyphemus) in Florida, USA, where this keystone species is being confined to ever smaller habitat fragments. The variant was based on the premise that individuals within populations are likely to occur at unusually high densities when confined to small areas, and it estimated minimum patch size as the smallest area beyond which density plateaus. The data for our study came from detailed surveys of 38 populations of the tortoise. For all 38 populations, the areas occupied were determined empirically, and for 19 of them, duplicate surveys were undertaken about a decade apart. We found that a consistent inverse density area relationship was present over smaller areas. The minimum patch size estimated from the density-area relationship was at least 100 ha, which is substantially larger than previous estimates. The relative abundance of juveniles was inversely related to population density for sites with relatively poor habitat quality, indicating that the estimated minimum patch size could represent an extinction threshold. We concluded that a negative density area relationship may be an inevitable consequence of excessive habitat loss. We also concluded that any detrimental effects of an inverse density area relationship may be exacerbated by the deterioration in habitat quality that often accompanies habitat loss. Finally, we concluded that the value of any estimate of minimum patch size as a conservation tool is compromised by excessive habitat loss.
Ecology 07/2007; 88(6):1401-7. · 4.85 Impact Factor
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ABSTRACT: Because we possess little understanding of what constitutes optimal habitat for the threatened sand skink, any individual charged with choosing among habitat fragments to promote recovery of the species will need to employ some guesswork. We examined the relative values of employing two kinds of guesswork, “uneducated guesswork,” from literature descriptions of optimal habitat, and “educated guesswork,” from expert judgments of optimal habitat. The rank order of seven areas of scrub habitat in central Florida based on abundance of the sand skink (Neoseps reynoldsi) was compared with the rank order of the areas based on literature descriptions and on expert judgments. Ranks of areas based on expert judgments predicted ranks of areas based on sand skink abundance much better than did ranks of areas based on literature descriptions. Our results show, on the one hand, how uneducated guesswork could challenge recovery of the sand skink and, on the other hand, how educated guesswork could support its recovery.Debido a que poseemos muy poca información de lo que constituye el hábitat óptimo de la especie amenazada Neoseps reynoldsi, cualquier individuo encargado de seleccionar entre fragmentos de hábitat para promover la recuperación de la especie deberá emplear algunas conjeturas. Examinamos los valores relativos del empleo de dos tipos de conjeturas, la “conjetura no educada” de las descripciones de hábitat óptimo de la literatura y la “conjetura educada” de la opinión de expertos en hábitat óptimo. El orden de rangos de siete áreas de hábitat de matorral en Florida central basados en la abundancia de N. reynoldsi se compararon con los rangos de las áreas basadas en las descripciones de la literatura y en base a las opiniones de expertos. Los rangos de áreas basadas en la opinión de los expertos predijo rangos de áreas en base a la abundancia de la especie mucho mejor que los rangos de área basados en las descripciones de la literatura. Nuestros resultados muestran que por un lado las conjeturas no educadas podrían amenazar la recuperación de la especie y por otro lado como las conjeturas educadas pueden soportar su recuparación.
Conservation Biology 01/1999; 13(1):190 - 194. · 4.69 Impact Factor
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ABSTRACT: Recent reports have suggested that a global decline in amphibian populations has taken place during the past few decades. Urban development is thought to affect the richness and abundances of species and, therefore, could be an important cause of decline. We estimated the richness and abundances of anurans in wetlands at a residential development and in similar wetlands at a nearby undeveloped park. The residential development originally was pine flatwoods habitat, as is the undeveloped park curiently. We also compared the anuran species' composition of the park in 1992 with the composition in 1974.Both richness and abundances of anurans in the residential development were different than those in the undeveloped park. Employing the same amount of sampling effort at both sites, we trapped or observed 11 species at the developement and 15 species at the park, and trapped 569 individuals at the development and 1224 individuals at the park. The anuran species richness at the undeveloped park in 1992 was nearly the same as in 1974; a single rare species apparently was not present in 1992. Of the 15 species present in both surveys, 14 showed higher abundances in 1992 than in 1974.We suggest that the current differences between the residential development and the park have resulted from degradation of both the uplands used by many species during the dry season and the temporary wetlands used by many species for reproduction. Four species especially sensitive to such degradation, Bufo quercicus, Scaphiopus h. holbrookii, Hyla femoralis, and H. gratiosa, were the species missing from the residential development.Not all species of anurans typical of pine flatwoods appeared to be affected adversely by development. Three species of ranids, Rana utricularia, R. grylio, and R. catesbeiana, were found in higher abundances at the residential development than at the park. These ranid species breed in a wide variety of aquatic systems, including the permanent bodies of water that are now abundant in the development, and probably use the uplands less than other anurans.If amphibian decline is international in scope, then the decline could be attributable either to global changes caused by humans, or to local, but widespread, environmental degradation, or to a combination of factors. While much recent popular focus has been on potential global causes of decline, we believe that this emphasis may have caused attention to be taken away from local causes that, as our study demonstrated, may be at least as important. We suggest that in many places, local environmental degradation is insidiously chipping away at amphibian diversity, and that more emphasis should be placed on these local causes than is now the case.
Biodiversity and Conservation 11/1996; 5(12):1579-1595. · 2.24 Impact Factor
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ABSTRACT: We surveyed the mangrove forest at the mouth of Lostman's River, on the southwestern coast of Florida, about 2 months after Hurricane Andrew had passed. Damage to the mangrove forest there was severe: about 60% of the trees were either uprooted or broken, about 25% of the upright, unbroken trees were dead, and only about 14% of the upright, unbroken trees were well vegetated. Larger trees were more likely to be damaged, and damaged more severely, than smaller trees. Overall, Rhizophora mangle (red mangrove) fared marginally better than Avicennia germinans (black mangrove), and both of these species fared substantially better than Laguncularia racemosa (white mangrove). The forest structure at our site likely will be substantially altered as a result of Hurricane Andrew for some time to come.
Bulletin of Marine Science -Miami- 06/1996; 59(1):1-8. · 1.15 Impact Factor
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Conservation Biology. 01/1992; 6:537-548.
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ABSTRACT: We compared two assessments of the status of gopher tortoise populations at 10 protected sites in Florida, taken about a decade apart. We assessed status indirectly, using surveys of burrows along belt transects. Transect placement and timing were identical between surveys. We compared numbers of burrows, relative numbers of burrows of different activity conditions, and size distributions of burrows between surveys. The comparisons indicated that populations had declined at as many as eight of the sites. We found no strong connection between population decline and decline in habitat quality, as reflected in decreased ground cover and/or increased canopy cover between surveys. The response of a population to decline in habitat quality may depend on initial habitat structure, the degree of change in habitat structure, the period of time over which change is measured, the amount of habitat involved, and the level of habitat management.
Biological Conservation.
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ABSTRACT: Little is known about the reproductive behaviors and the actual outcomes of mating attempts in the gopher tortoise (Gopherus polyphemus). We examined the mating system and reproductive behaviors of a population of gopher tortoises in central Florida. Using microsatellite markers, we assigned fathers to the offspring of seven clutches and determined that multiple fathers were present in two of the seven clutches examined. We found that gopher tortoises exhibited a promiscuous mating system with larger males fertilizing the majority of clutches. The advantage of larger males over smaller males in fertilizing females may be a result of larger males winning access to females in aggressive bouts with other males or larger males may be more attractive to females. Clutches produced by larger females tended to be sired by a single male, whereas clutches of smaller females tended to be sired by multiple males.
Journal of Heredity 97(2):150-7. · 2.80 Impact Factor
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ABSTRACT: "Based on a symposium held May 1988, University of South Florida, Chinsegut Hill Conference Center" Incluye bibliografía e índice
SERBIULA (sistema Librum 2.0).
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ABSTRACT: The Florida Sand Skink (Plestiodon reynoldsi), the Florida Scrub Lizard (Sceloporus woodi), and the Six-lined Racerunner (Aspidoscelis sexlineata) occur in the threatened and fire-maintained Florida scrub habitat. Fire may have different consequences to local genetic diversity of these species because they each have different microhabitat preference. We collected tissue samples of each species from 3 sites with different time-since-fire: Florida Sand Skink n = 73, Florida Scrub Lizard n = 70, and Six-lined Racerunner n = 66. We compared the effect of fire on genetic diversity at microsatellite loci for each species. We screened 8 loci for the Florida Sand Skink, 6 loci for the Florida Scrub Lizard, and 6 loci for the Six-lined Racerunner. We also tested 2 potential driving mechanisms for the observed change in genetic diversity, a metapopulation source/sink model and a local demographic model. Genetic diversity varied with fire history, and significant genetic differentiation occurred among sites. The Florida Scrub Lizard had highest genetic variation at more recently burned sites, whereas the Florida Sand Skink and the Six-lined Racerunner had highest genetic variation at less recently burned sites. Habitat preferences of the Florida Sand Skink and the Florida Scrub Lizard may explain their discordant results, and the Six-lined Racerunner may have a more complicated genetic response to fire or is acted on at a different geographic scale than we have investigated. Our results indicate that these species may respond to fire in a more complicated manner than predicted by our metapopulation model or local demographic model. Our results show that the population-level responses in genetic diversity to fire are species-specific mandating conservation management of habitat diversity through a mosaic of burn frequencies.
The Journal of heredity 102(4):399-408. · 2.05 Impact Factor
