Conservation genetic assessment of the paleback darter,Etheostoma pallididorsum,a narrowly distributed endemic in the Ouachita Highlands,Arkansas, USA

1. The paleback darter, Etheostoma pallididorsum, is considered imperilled and has recently been petitioned for listing under the Endangered Species Act. Previous allozyme-based studies found evidence of a small effective population size, warranting conservation concern. The objective of this study was to assess the population dynamics and the phylogeographical history of the paleback darter, using a multilocus microsatellite approach and mitochondrial DNA.
2. The predictions of this study were that: paleback darter populations will exhibit low genetic diversity and minimal gene flow; population structure will correspond to the river systems from which the samples are derived; reservoir dams impounding the reaches between the Caddo and Ouachita rivers would serve as effective barriers to gene flow; and the Caddo and Ouachita rivers are reciprocally monophyletic.
3. Microsatellite DNA loci revealed significant structure among sampled localities (global F_st = 0.17, P < 0.001), with evidence of two distinct populations representing the Caddo and Ouachita rivers. However, Bayesian phylogeographical analyses resulted in three distinct clades: Caddo River, Ouachita River, and Mazarn Creek. Divergence from the most recent ancestor shared among the river drainages was estimated at 60 Kya. Population genetic diversity was relatively low (H_e = 0.65; mean alleles per locus, A = 6.26), but was comparable with the population genetic diversity found in the close relatives slackwater darter, Etheostoma boschungi (H_e = 0.65; A = 6.74), and Tuscumbia darter, Etheostoma tuscumbia (H_e = 0.57; A = 5.53).
4. These results have conservation implications for paleback darter populations and can be informative for other headwater specialist species. Like other headwater species with population structuring and relatively low genetic diversity, the persistence of paleback darter populations is likely to be tied to the persistence and connectivity of local breeding and non-breeding habitat. These results do not raise conservation concern for a population decline; however, the restricted distribution and endemic status of the species still renders paleback darter populations vulnerable to extirpation or extinction.

     

Weak connectivity and population cohesiveness in rudderfish Kyphosus sandwicensis (Teleostei: Kyphosidae) inhabiting remote oceanic islands

1. Population connectivity has a fundamental role in metapopulation dynamics, with important implications in conservation. Easter Island (EI) and Salas y Gómez Island (SG) in the Pacific Ocean are ideal for the study of population connectivity because they are separated by 415 km and isolated from other islands in the Pacific Ocean by >2,000 km.
2. Considering that dispersal processes could play a critical role in the persistence of its populations, the connectivity pattern of the rudderfish Kyphosus sandwicensis was evaluated between EI and SG using both a population genetics and a biophysical modelling approach.
3. The variability in the control region of the mitochondrial DNA did not show a significant phylogeographical pattern, and the variability in 16 microsatellite loci suggested that individuals of K. sandwicensis located at EI and SG belong to the same genetic population. However, historical migration showed that 0.2% of the recruits at EI come from SG and that 0.15% at SG come from EI per year.
4. Using simulated larval release during September and a larval development of 30 days in the plankton, biophysical modelling did not detect migration between the islands. Furthermore, self-recruitment shows interannual variation ranging from 5 to 10% of the total released larvae.
5. Whereas the genetic data showed a lack of population genetic structure but low connectivity of K. sandwicensis between EI and SG, the biophysical modelling showed null movement of particles between the islands. Stochastic movement of larvae or adults could explain the pattern observed, with rafting as an example. These low-frequency and stochastic movements may be important in maintaining the cohesiveness between EI and SG.

     

Indirect connectivity estimates of amphibian breeding wetlands from spatially explicit occupancy models

相似文献   

Genetic connectivity supports recovery of gorgonian populations affected by climate change

相似文献   

Exploring uncertainty in population viability analysis and its implications for the conservation of a freshwater fish

相似文献   

Improving breed-and-release programmes in the face of a threatening pathogen,Batrachochytrium dendrobatidis

1. As the proportion of threatened species increases, so too does the need for effective conservation strategies. In response, captive breed-and-release and habitat mitigation programmes are two conservation actions that are increasing in use and effectiveness.
2. Success of these programmes is frequently hampered by the continued presence of threatening processes. In the case of amphibian reintroductions, a key threatening process that is difficult to eliminate is the deadly fungal pathogen, Batrachochytrium dendrobatidis (Bd). This pathogen is the proximate cause of decline for the threatened green and golden bell frog, Litoria aurea, and has contributed to the failure of previous breed-and-release programmes of this amphibian.
3. To investigate whether is it possible to establish a captive-bred population of L. aurea that could persist in the presence of Bd, a breed-and-release programme was conducted in a created habitat that included increased salinity to inhibit fungal growth rates, exclusion of potential reservoir hosts and source animals bred from parents ‘experienced’ with the strain of Bd present in the release environment.
4. The population persisted in the created habitat for more than 4 years (the timescale of monitoring) but suffered higher infection levels compared with nearby extant populations of L. aurea. These infections significantly reduced apparent survival. Infection dynamics were linked to temperature, host density in the previous season, and size and age of the host, and these factors differed from those in extant populations and are likely to have contributed to the high levels of Bd infection at the created site.
5. This article discusses how it may be possible to manipulate these factors to improve the success of future breed-and-release programmes, and recommends the construction of warm water bodies and a strategy of prioritizing the release of fewer, large propagules of high body condition and mixed-age class, over large numbers of younger, smaller animals.

     

Rapid response of fish and aquatic habitat to removal of a tidal barrier

1. River barrier removal is used increasingly as a conservation tool to restore lotic habitat and river connectivity, but evidence of its efficacy is incomplete. This study used a before–after methodology to determine the effects of removing a tidal-limit barrier on the fishes, macroinvertebrates, and habitats of an English coastal stream.
2. Following barrier removal, habitat diversity increased immediately upstream and remained similar downstream. Mobilized silt altered the substrate composition immediately downstream, but this was temporary as silt was flushed out the following winter. Changes to macroinvertebrate communities occurred upstream and downstream of the former barrier but these were transient.
3. A dramatic and sustained increase in fish density occurred immediately upstream of the barrier after its removal, but effects downstream were minor. The fish community upstream changed, largely due to rapid recruitment and dispersal of endangered European eel (Anguilla anguilla). Eel density in the formerly impounded zone increased from 0.5 per 100 m² before barrier removal to 32.5 per 100 m² 5 months after removal. By 17 months after barrier removal there was no difference in eel density across the six sections sampled.
4. Although resident stream fishes such as bullhead (Cottus gobio species complex, protected under the European Habitats Directive) were abundant in middle and upper-stream sections, brown trout (Salmo trutta, a listed species for biodiversity conservation in England and Wales) density remained low during the study and recruitment was poor. This suggests that although colonization access for anadromous trout was available, habitat upstream may have been unsuitable for reproduction, indicating that wider catchment management is required to complement the restoration of connectivity.
5. These findings suggest that tidal barrier removal is an effective method of restoring lotic habitats and connectivity, and can be beneficial for resident and migratory fishes including those of conservation importance (e.g. European eel) in coastal streams.

     

High‐resolution modelling of ocean circulation can reveal retention spots important for biodiversity conservation

相似文献   

Habitat suitability,coverage by protected areas and population connectivity for the Siamese crocodile Crocodylus siamensis Schneider, 1801

相似文献   

Dolphin population specialized in foraging with artisanal fishers requires zero-bycatch management to persist

1. The small population paradigm assumes that populations with low numbers of individuals intrinsically have a high probability of extinction. The small population of Lahille’s bottlenose dolphins Tursiops truncatus gephyreus that specializes in foraging with artisanal fishers in Laguna, southern Brazil, faces human pressures including bycatch in fishing gear. The viability of this population was modelled over 30 and 100 years under different levels of bycatch, including the current scenario of two bycatches every year, two scenarios with higher incidence of bycatches and three management scenarios. The sensitivity of predicted growth rates to fixed-proportion and observed-variation changes in life history parameters was explored.
2. The current scenario predicted a declining population (r = −0.014; λ = 0.986) with a high probability of extinction in the long term (PE = 0.71). A small increase in bycatches would result in a marked increase in the probability of extinction. Management scenarios seem promising, but only the zero-bycatch management scenario would make the difference between a declining and an increasing population.
3. As expected for slow-growing species, population growth rate was most sensitive to proportional changes in adult female and juvenile survival. However, considering observed variation in vital rates, population dynamics were most influenced by variation in reproductive rates.
4. To determine the highest priority for management action, another simulation was made of how additional threat scenarios of recognized human activities (i.e. bycatch influencing adult survival and increased underwater noise or pollution influencing calf survival) would affect population dynamics. Population growth rate was very sensitive to changes in adult bycatch (especially females), as expected, and only subtly sensitive to a reduction in calf survival.
5. The current level of bycatch is unsustainable. Bycatch needs to be eliminated to maximize the probability of long-term persistence of this dolphin population. However, this population’s persistence could be threatened by natural variation in reproductive rates.

     

Genetic structure of Orbicella faveolata population reveals high connectivity among a marine protected area and Varadero Reef in the Colombian Caribbean

1. The protection of ecosystems with high diversity, such as coral reefs, is not an approach that guarantees their conservation. Thus, maintaining connectivity among coral populations over the long term is a strategy that should be adopted in order to protect diversity and ecological processes. Although coral reefs in Colombia are highly diverse, the population genetics baseline data of keystone species such as Orbicella faveolata are limited.
2. To provide current information about the connectivity between populations of O. faveolata in the Colombian Caribbean, the genetic diversity and distribution of O. faveolata was evaluated with analysis of molecular variance (AMOVA), principal components, and migration estimations using 113 genets distributed in six populations. Also, a genetic structure analysis that included the available data for the Caribbean population was conducted, seeking to understand how the Colombian populations relate to the broader region.
3. According to the global fixation index (F_ST) for the Colombian Caribbean, there was no genetic structure (F_ST = 0.002). Discriminant analysis of principal components (DAPC) showed that Corales del Rosario Archipelago (CR), Este de Isla Fuerte (EIF), San Bernardo Archipelago (SB), and Varadero Reef (VR) were grouped with Oeste de Isla Fuerte (OIF), with Bushnell (BS) representing the most divergent cluster. Migration analysis showed relatively high migration from VR to CR and SB, highlighting the importance of VR as a genetic reservoir for the region. Structure analysis showed that the Colombian population presented a specific genetic identity (F_ST = 0.254), suggesting that the Colombian Caribbean population could be a peripheral population that contributes significantly to genetic variation and is connected through a complex connectivity process.
4. In conclusion, the estimated genetic connectivity reflects the influence of sea surface dynamics over the interpopulation exchange dynamics and the role of protected and nonprotected coral reef in the Colombian Caribbean. Thus, the Colombian Caribbean population of O. faveolata could be relevant to the conservation of genetic diversity on a larger scale.

     

Constrained by aliens,shifting landscape,or poor water quality? Factors affecting the persistence of amphibians in an urban pond network

1. Freshwater communities and especially pond‐breeding amphibians are extremely vulnerable to land‐use change, alien species introductions and the use of pesticides or other toxic chemicals, as reflected in their worldwide decline. Effective conservation and management of ponds requires a better understanding of the biotic and abiotic factors that shape diversity patterns and species distribution, especially in cases of habitat loss
2. The present study aimed to reveal and classify which pond and landscape characteristics are the most important determinants for the occurrence patterns of amphibian species as well as for the overall amphibian species richness in an urban pond network. To achieve this aim, 17 biotic and abiotic variables were measured for 61 ponds and the dataset was analysed by means of a machine‐learning approach, suitability indices and co‐occurrence modelling
3. The highest probability of Triturus macedonicus occurrence was found at fishless artificial and semi‐natural ponds. The persistence of Lissotriton graecus in ponds was predicted by high pond connectivity and the absence of fish reflecting the species dispersive potential. Pelophylax kurtmuelleri showed a higher probability of occurrence with increased pond connectivity and macrophyte cover.
4. Amphibian species richness was higher in fishless ponds with well‐oxygenated waters located in sites with a low to intermediate road density network. Ponds categorized as ‘average’ in terms of newt suitability were more frequently inhabited by fish than Triturus macedonicus. Alien fish species showed negative associations with both newt species, while both newt species showed a positive association between them.
5. The results support the view that conserving a greater number of water bodies with increased landscape connectivity and without any fish presence could provide amphibian species with alternative habitat choices, especially in sites with human pressure where pond stability is at stake owing to continuous landscape changes.

     

Comparison of spatial distribution models to predict subtidal burying habitat of the forage fish Ammodytes personatus in the Strait of Georgia,British Columbia,Canada

1. The Pacific sand lance (Ammodytes personatus) is a key forage species for many commercially important fish (e.g. salmon and groundfish), marine birds, and whales found in nearshore coastal waters of British Columbia, Canada.
2. Sand lance lack a swim bladder and have a requirement for low-silt, medium-coarse sandy sea-bed habitat for burying. Little information is available describing the distribution of burying habitat, partly because there are no commercial fisheries for A. personatus in British Columbia.
3. This information is required by habitat and wildlife managers to identify and protect uncommon patches of burying habitats from detrimental activities, including dredging, infilling, and oil spills.
4. In this study, habitat distribution results from five suitability modelling algorithms were evaluated: maximum entropy, generalized linear model, generalized additive model, random forest, and an ensemble model of the latter three.
5. The maximum entropy model had the highest performance score (area under the receiver operator characteristic curve was 0.78) and was selected as the model that most accurately identified the presence of suitable A. personatus burying habitat.
6. Model results indicate that suitable burying habitat is primarily influenced by derived sea-bed substrate, distance to estuary, distance to sand-gravel beaches, and bottom sea temperature.
7. Overall, the spatial modelling identified only 105 km² of highly suitable sand lance burying habitat, or 2.6% of the study area (0–150 m), primarily in Haro Strait, along the east coast of Vancouver Island, and in northern regions of the strait near Cortes, Savary, and Harwood islands.
8. Identification of this uncommon and patchy burying habitat will contribute to the ongoing conservation of an important coastal prey species.

     

Don't go breaking apart: Anthropogenic disturbances predict meadow fragmentation of an endangered seagrass

1. Although it is well established that human activities are linked to the loss of seagrasses worldwide, the influence of anthropogenic disturbances on the habitat fragmentation of seagrass meadows is less understood. This information is essential to identify how humans are modifying seascapes and what disturbances pose the greatest risk to seagrasses, which is pertinent given the rapid urbanization occurring in coastal areas.
2. This study examined how the habitat fragmentation of an endangered seagrass Posidonia australis varied in relation to several anthropogenic disturbances (i.e. human population, marine infrastructure, terrestrial run-off and catchment land-usage) within 10 estuaries across 620 km of coastline in New South Wales, Australia.
3. When comparing between estuaries, the fragmentation of P. australis meadows was significantly greater in estuaries adjacent to highly populated metropolitan centres – generally in the Greater Sydney region. At sites within estuaries, the density of boat moorings was the most important predictor of habitat fragmentation, but there was also evidence of higher fragmentation with increased numbers of jetties and oyster aquaculture leases.
4. These results suggest that the fragmentation of seagrass meadows will become more pervasive as the human population continues to grow and estuarine development increases. Strategies to mitigate anthropogenic disturbances on seagrass meadow fragmentation could include prohibiting the construction of boat moorings and other artificial structures in areas where seagrasses are present or promoting environmentally friendly designs for marine infrastructure. This knowledge will support ongoing management actions attempting to balance coastal development and the conservation of seagrasses.

     

Genetic connectivity and phylogeography of the night shark (Carcharhinus signatus) in the western Atlantic Ocean: Implications for conservation management

相似文献   

Modelling effects of disturbance on population dynamics of generalized crayfish life history strategies

1. Crayfish play a crucial ecological role and are often considered a keystone species within freshwater ecosystems; however, North American crayfish species face disturbance and ecological threats including invasive species and intensified drought.
2. Demographic models can allow examination of population dynamics of a targeted species under a wide variety of disturbance scenarios. In this study, crayfish population dynamics were modelled and their responses to simulated biological invasions and drought were assessed.
3. As life history data on crayfish are relatively rare, models were used to explore the population viability of four generalized species with distinct life history strategies under 11 disturbance scenarios. RAMAS-Metapop was used to construct stage-based demographic metapopulation models parameterized using vital rates from established literature sources.
4. Models indicated that populations respond differentially to disturbance based on life history. However, both r- and K-selected species appear to be highly susceptible to decline when faced with the additive effects of reduced carrying capacity resulting from invasion and reduced survival rates caused by drought.
5. Constructing models that explore a broad array of life histories and disturbance regimes can provide managers with tools to develop generalized, widely applicable conservation strategies in data-depauperate systems.

     

A new map of the tiger shark (Galeocerdo cuvier) genetic population structure in the western Atlantic Ocean: Hypothesis of an equatorial convergence centre

相似文献   

Identifying important habitat for northern bottlenose and Sowerby's beaked whales in the western North Atlantic

相似文献   

Cumulative impacts of habitat fragmentation and the environmental factors affecting upstream migration in the threatened sea lamprey,Petromyzon marinus

1. River ecosystems are often fragmented by artificial structures, such as weirs. For anadromous species, these structures can impede access to upstream spawning sites and ultimately lead to severe population declines.
2. This study focused on the freshwater spawning migration of the sea lamprey, Petromyzon marinus, an anadromous species threatened by habitat fragmentation across its native range. To quantify the cumulative impacts of multiple weirs on upstream-migrating adults, and to explore the environmental factors affecting migratory movements, passive acoustic telemetry was applied to 56 individuals during their spawning migration in the heavily fragmented River Severn basin, UK.
3. While 89% of tagged sea lamprey passed the first weir upstream of the release site on the main river, only 4% passed the fifth weir. For 85% of migrants, the upstream extent of migration was immediately downstream of a weir. Individuals that passed weirs upstream of the release site (n = 50) took 21.6 ± 2.8 days to reach their most upstream location, experiencing cumulative passage times at weirs of 15.7 ± 2.8 days; these delays constituted a median of 84% of total upstream movement times.
4. Multistate models showed that the weir passage rates of sea lamprey in tidal and non-tidal areas increased significantly when downstream river level and discharge were elevated. Upstream-to-downstream changes in direction were frequent downstream of weirs, but rare in unobstructed river sections.
5. The results provided evidence for a cumulative effect of multiple weirs on sea lamprey movements, substantially delaying upstream migrants and limiting their spawning to atypical habitat. The results also demonstrated the crucial roles of high tides and elevated discharge events in enabling weir passage. Although the Severn Estuary features conservation designations for sea lamprey, this study reveals that barriers are inhibiting their upstream migration, a problem that should be addressed to assist sea lamprey conservation.

     

Gene pool and connectivity patterns of Pinna nobilis in the Balearic Islands (Spain,Western Mediterranean Sea): Implications for its conservation through restocking

相似文献