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James R. Spotila - One of the best experts on this subject based on the ideXlab platform.
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Alien plant threatens Nile crocodile (Crocodylus niloticus) breeding in Lake St. Lucia, South Africa.
Biological Conservation, 2001Co-Authors: Alison J Leslie, James R. SpotilaAbstract:Abstract We observed that the majority of Lake St. Lucia's Nesting Nile crocodiles ( Crocodylus niloticus ) selected open, sunny, sandy areas in which to deposit their eggs. Nests were only found in shaded Sites in the Mpate River breeding area and these nests were shaded primarily by an alien plant Chromolaena odorata . Soil temperatures of shaded Sites at 25-cm depth, were on average 5.0–6.0°C cooler than in sunny Sites at the same depth. They were well below the pivotal temperature for nests of St. Lucia's Nile crocodiles, i.e. they probably produced a female-biased sex ratio, and may have prevented embryonic development altogether. Many females abandoned Nesting Sites when they encountered the fibrous root mats of Chromolaena odorata while digging egg chambers. When additional Nesting Sites were experimentally created, the percent of Sites utilized increased, indicating that suitable Nesting Sites were in short supply. This alien plant is posing a very serious threat to the continued survival of the Nile crocodile in Greater St. Lucia Wetland Park, and unless immediate action is taken, a female-biased sex ratio will result in eventual extirpation of the species from this recently acclaimed Word Heritage Site.
Alison J Leslie - One of the best experts on this subject based on the ideXlab platform.
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Alien plant threatens Nile crocodile (Crocodylus niloticus) breeding in Lake St. Lucia, South Africa.
Biological Conservation, 2001Co-Authors: Alison J Leslie, James R. SpotilaAbstract:Abstract We observed that the majority of Lake St. Lucia's Nesting Nile crocodiles ( Crocodylus niloticus ) selected open, sunny, sandy areas in which to deposit their eggs. Nests were only found in shaded Sites in the Mpate River breeding area and these nests were shaded primarily by an alien plant Chromolaena odorata . Soil temperatures of shaded Sites at 25-cm depth, were on average 5.0–6.0°C cooler than in sunny Sites at the same depth. They were well below the pivotal temperature for nests of St. Lucia's Nile crocodiles, i.e. they probably produced a female-biased sex ratio, and may have prevented embryonic development altogether. Many females abandoned Nesting Sites when they encountered the fibrous root mats of Chromolaena odorata while digging egg chambers. When additional Nesting Sites were experimentally created, the percent of Sites utilized increased, indicating that suitable Nesting Sites were in short supply. This alien plant is posing a very serious threat to the continued survival of the Nile crocodile in Greater St. Lucia Wetland Park, and unless immediate action is taken, a female-biased sex ratio will result in eventual extirpation of the species from this recently acclaimed Word Heritage Site.
Gerald Kastberger - One of the best experts on this subject based on the ideXlab platform.
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genetic structure of an apis dorsata population the significance of migration and colony aggregation
Journal of Heredity, 2004Co-Authors: Jurgen Paar, E Huettinger, Benjamin P Oldroyd, Gerald KastbergerAbstract:Eight microsatellite loci were used to investigate the genetic structure of the giant honeybee (Apis dorsata) population in northeast India. This species migrates seasonally between summer and winter Nesting Sites, and queens appear to return to their previously occupied site. Furthermore, there is a strong tendency for colonies of this species to aggregate at perennially utilized Nesting Sites that may be shared by more than 150 colonies. These behavioral features suggest that colonies within aggregations should be more related than random colonies, but that the long-distance migration could act to minimize genetic differentiation both between geographical areas and within aggregations. Our genetic study supports these conjectures arising from natural history. A. dorsata aggregations are comprised of colonies that share more alleles than expected by chance. Although queens heading neighboring colonies are not close relatives, fixation indices show significant genetic differentiation among aggregation Sites. However, there appears to be sufficient gene flow among aggregations to prevent high degrees of relatedness developing between colonies within aggregations. The results also suggest that there is significant population structuring between geographical regions, although the level of structuring caused by aggregation
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Genetic Structure of an Apis dorsata Population: The Significance of Migration and Colony Aggregation
The Journal of heredity, 2004Co-Authors: Jurgen Paar, E Huettinger, Benjamin P Oldroyd, Gerald KastbergerAbstract:Eight microsatellite loci were used to investigate the genetic structure of the giant honeybee (Apis dorsata) population in northeast India. This species migrates seasonally between summer and winter Nesting Sites, and queens appear to return to their previously occupied site. Furthermore, there is a strong tendency for colonies of this species to aggregate at perennially utilized Nesting Sites that may be shared by more than 150 colonies. These behavioral features suggest that colonies within aggregations should be more related than random colonies, but that the long-distance migration could act to minimize genetic differentiation both between geographical areas and within aggregations. Our genetic study supports these conjectures arising from natural history. A. dorsata aggregations are comprised of colonies that share more alleles than expected by chance. Although queens heading neighboring colonies are not close relatives, fixation indices show significant genetic differentiation among aggregation Sites. However, there appears to be sufficient gene flow among aggregations to prevent high degrees of relatedness developing between colonies within aggregations. The results also suggest that there is significant population structuring between geographical regions, although the level of structuring caused by aggregation exceeds the differentiation attributable to geographic region.
Bryan P. Wallace - One of the best experts on this subject based on the ideXlab platform.
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A global gap analysis of sea turtle protection coverage
Biological Conservation, 2014Co-Authors: Antonios D Mazaris, Vasiliki Almpanidou, Bryan P. Wallace, John D. Pantis, Gail SchofieldAbstract:Although the number and extent of protected areas (PAs) are continuously increasing, their coverage of global biodiversity, as well as criteria and targets that underline their selection, warrants scrutiny. As a case study, we use a global dataset of sea turtle Nesting Sites (n = 2991) to determine the extent to which the existing global PA network encompasses Nesting habitats (beaches) that are vital for the persistence of the seven sea turtle species. The majority of Nesting Sites (87%) are in the tropics, and are mainly hosted by developing countries. Developing countries contain 82% Nesting Sites, which provide lower protection coverage compared to developed countries. PAs encompass 25% of all Nesting Sites, of which 78% are in marine PAs. At present, most Nesting Sites in PAs with IUCN ratification receive high protection. We identified the countries that provide the highest and lowest Nesting site protection coverage, and detected gaps in species-level protection effort within countries. No clear trend in protection coverage was found in relation to gross domestic product, the Global Peace Index or sea turtle regional management units; however, countries in crisis (civil unrest, war or natural catastrophes) provided slightly higher protection coverage of all countries. We conclude that global sea turtle resilience against threats spanning temperate to tropical regions require representative PA coverage at the species level within countries. This work is anticipated to function as a first step towards identifying specific countries or regions that should receive higher conservation interest by national and international bodies.
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regional management units for marine turtles a novel framework for prioritizing conservation and research across multiple scales
PLOS ONE, 2010Co-Authors: Bryan P. Wallace, Andrew Dimatteo, Brendan J Hurley, Elena M Finkbeiner, Alan B BoltenAbstract:Background: Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques — including site-based monitoring, genetic analyses, mark-recapture studies and telemetry — can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings: To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including Nesting Sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for Nesting Sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine- to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally. Conclusions/Significance: The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of Nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework — including maps and supporting metadata — will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.
Yoshito Nakashima - One of the best experts on this subject based on the ideXlab platform.
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population structure of the loggerhead turtle caretta caretta a large marine carnivore that exhibits alternative foraging behaviors
Marine Ecology Progress Series, 2011Co-Authors: Kunihiro Watanabe, Hideo Hatase, Masato Kinoshita, Kazuyoshi Omuta, Takeharu Bando, Naoki Kamezaki, Katsufumi Sato, Yoshimasa Matsuzawa, Kiyoshi Goto, Yoshito NakashimaAbstract:Knowledge of detailed population genetic structure is crucial to conserve and manage endangered species effectively. Size-related variation in feeding-habitat use (neritic vs. oceanic) by adult loggerhead turtles Caretta caretta has been reported within several populations, and sympatric population subdivision was suspected. In the present study, genetic differences between the 2 feeding-habitat groups within 2 Japanese Nesting Sites were assessed, using 5 microsatellite loci and mitochondrial (mt) DNA sequences. There were no genotypic or haplotype differences between the feeding-habitat groups, which were defined by egg-yolk stable isotope ratios and body size, at both Nesting Sites, suggesting that both neritic and oceanic individuals belong to the same genetic population. Differences in feeding-habitat use are unlikely to be a limiting factor for gene flow between feeding-habitat groups and were thought to be the result of phenotypic plasticity rather than population subdivision. Gene flow among 5 Nesting Sites was assessed by pooling these feeding-habitat groups at each Nesting site. Significant genetic structure by female natal homing was observed at the mtDNA level. However, no significant structure was found at the microsatellite DNA level, suggesting male-mediated gene flow caused by migration through courtship areas. Although Nesting beaches are connected by male-mediated gene flow, which might have evolved as a mechanism to avoid genetic fragmentation by natal homing, extirpated beaches would not be easily recolonized from other Nesting populations due to female philopatry. Therefore, conservation of individual Nesting beaches is still needed to maintain the overall genetic diversity of Japanese loggerheads.