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16 results for “declining amphibians”
Monitoring Amphibians in the Declined Hemlocks at Harvard Forest 2013-2014
Disturbances such as outbreaks of nonnative insects and pathogens can devastate unique habitats and directly reduce biodiversity. The foundation tree species Tsuga canadensis (eastern hemlock) is declining due to infestation by the nonnative insect Adelges tsugae (hemlock woolly adelgid). The decline and expected elimination of hemlock from northeastern US forests is changing forest structure, function, and assemblages of associated species. We assessed changes in occupancy, detection probability, and relative abundance of two species of terrestrial salamanders, Plethodon cinereus (eastern red-back salamander) and Notopthalmus viridescens viridescens (eastern red-spotted newt), in the experimental removal of T. canadensis at Harvard Forest. Four treatments (logging, girdling, hemlock control and hardwood control) have been applied and replicated in eight 0.81-ha plots. Salamanders were sampled under cover boards and using visual encounter surveys in June-July of 2013 and 2014. Removal of the hemlock canopy increased occupancy of P. cinereus but significantly reduced its estimated detection probability and abundance. Estimated abundance of N. v. viridescens also declined dramatically after canopy manipulations. Our results suggest that ten years after hemlock loss due to either the adelgid or pre-emptive salvage logging, and 50-70 years later when these forests have become mid-successional mixed deciduous stands, that the abundance of these salamanders likely will be less than 50% of their abundance in current, intact hemlock stands.
Fig. 4 in International Journal for Parasitology: Parasites and Wildlife Outbreak of parasite-induced limb malformations in a declining amphibian species in Colorado
Fig. 4. (A) Excysted metacercaria of Ribeiroia ondatrae from an infected frog; (B) Rams horn snails (Helisoma trivolvis) function as first intermediate hosts for multiple trematode species, including Ribeiroia ondatrae. Several of these snails have egg masses on their shells, which can be common in the spring.
Fig. 3 in International Journal for Parasitology: Parasites and Wildlife Outbreak of parasite-induced limb malformations in a declining amphibian species in Colorado
Fig. 3. Whole-body ventrodorsal Micro-CT scans of three leopard frogs from SBN illustrating malformations caused by the trematode Ribeiroia ondatrae. Panels A–C present 3D reconstructions of the skeletons (ventral view) of each of the living frogs in the corresponding lower panels (D–F). For each, obviously abnormal portions of the skeleton are colored in red while supernumerary limb elements are colored in teal. (A) Frog with a severely rotated ilium on the left axis, a thickened femur, thickened tibiofibula (calcaneum) with a bony triangle, an extra bone at the base of the ischium, a supernumerary left hindlimb (polymelia) with a bony triangle in the tibiofibular; the right leg is missing all metatarsals and phalanges. (B) Frog with polymelia of the left leg, with two supernumerary femurs and two unidentified supernumerary bones near the ischium; both primary hind limbs appear to have reductions of the metatarsals and phalanges. (C) Frog with an extremely thickened femur (possibly fusion of multiple femurs) in the left hind limb, a double bony triangle in the tibiofibula, and an extra bone caudal to the ilium.
Fig. 1 in International Journal for Parasitology: Parasites and Wildlife Outbreak of parasite-induced limb malformations in a declining amphibian species in Colorado
Fig. 1. (A) Spring Brook North (SBN) Pond is located in southern Boulder County near Eldorado Springs, Colorado, USA. (B) Image of the pond in spring. (C) Northern leopard frogs (Rana pipiens) use the pond as breeding habitat (image copyright David Herasimtschuk).
Fig. 2 in International Journal for Parasitology: Parasites and Wildlife Outbreak of parasite-induced limb malformations in a declining amphibian species in Colorado
Fig. 2. Limb malformations in leopard frogs from this study include (A–D) skin webbings, which can affect one (A–B) or both (C–D) hind limbs; (E–H) bony triangles, which entail a triangular folding in a longbone and an associated shortening of the limb; and (H–K) extra limbs, feet, and digits, which were typically ventral. Frog in (H) exhibits a double bony triangle and severe truncation in the limb with a duplicated foot. Many animals exhibited multiple malformations and severe structural limb deformities, such as (L).
Data from: Human traffic and habitat complexity are strong predictors for the distribution of a declining amphibian
Invasive species and habitat modification threaten California's native pond-breeding amphibians, including the federally threatened California Red-legged Frog (Rana draytonii). The relative contributions of invasive species, including the American Bullfrog (Lithobates catesbeianus), and of habitat changes to these declines are disputed. I conducted a field study over several years in central California to examine the presence/absence of these two species at 79 breeding ponds to determine the predictive role for occupancy of factors including vegetation, pond characteristics, and measures of human activity. I used a boosted regression tree approach to determine the relative value of each predictor variable. Increased measures of human activity, especially proximity to trails and roads, were the best predictors for the absence of California Red-legged Frogs and California Newts. Historical factors and habitat conditions were associated with the extent and spread of the American Bullfrog. The extent and complexity of aquatic macrophytes and pond surface area were good predictors for the presence of these and other amphibian species. Surprisingly, invasive species played a relatively small role in predicting pond occupancy by the native species. These findings can inform conservation and restoration efforts for California Red-legged Frogs, which apparently persist best in small vegetated ponds in areas of low human disturbance.
Figure 4 in Groundwater decline has negatively affected the well-preserved amphibian community of Doñana National Park (SW Spain)
Figure 4. Number of amphibian species in each grid cell in the 2003-2004 and 2021-2022 survey periods (grid cells with red borders = dry ponds with 0 species).
Figure 3 in Groundwater decline has negatively affected the well-preserved amphibian community of Doñana National Park (SW Spain)
Figure 3. Number of grid cells in which each amphibian species occurred in the 2003-2004 and 2021-2022 survey periods. (Number of grid cells in 2003-2004 = 128, number of grid cells in 2021-2022 = 102).
Figure 2 in Groundwater decline has negatively affected the well-preserved amphibian community of Doñana National Park (SW Spain)
Figure 2. Occurrence of each amphibian species in Doñana National Park during the 2003-2004 and 2021-2022 survey periods. The first map shows the grid cells sampled during each survey period; in orange are the grid cells only surveyed in 2003-2004, in dark green are those only surveyed in 2021-2022, and in light green are those sampled during both periods. Red-bordered are the grid cells with data for 2003-2004 from ponds that were dry in 2021-2022. Similar colours are shown
Figure 1 in Groundwater decline has negatively affected the well-preserved amphibian community of Doñana National Park (SW Spain)
Figure 1. (A): Map of Doñana National Park (SW Spain) showing the sandy area (stabilized and moving dunes), and marsh. It also includes the cartography of temporary ponds, and permanent ponds (as per Gómez-Rodríguez et al., 2011). (B): Ponds Downloaded from Brill.com 08/07/2024 04:54:25PM sampled and the percentage of terrestrial vegetation via Openobserved Accessin. This their is basinsan.open access article distributed under the terms
Data from: Seasonal and ontogenetic variation of skin microbial communities and relationships to natural disease dynamics in declining amphibians
Recently, microbiologists have focused on characterizing the probiotic role of skin bacteria for amphibians threatened by the fungal disease chytridiomycosis. However, the specific characteristics of microbial diversity required to maintain health or trigger disease are still not well understood in natural populations. We hypothesized that seasonal and developmental transitions affecting susceptibility to chytridiomycosis could also alter the stability of microbial assemblages. To test our hypothesis, we examined patterns of skin bacterial diversity in two species of declining amphibians (Lithobates yavapaiensis and Eleutherodactylus coqui) affected by the pathogenic fungus Batrachochytrium dendrobatidis (Bd). We focused on two important transitions that affect Bd susceptibility: ontogenetic (from juvenile to adult) shifts in E. coqui and seasonal (from summer to winter) shifts in L. yavapaiensis. We used a combination of community-fingerprinting analyses and 16S rRNA amplicon sequencing to quantify changes in bacterial diversity and assemblage composition between seasons and developmental stages, and to investigate the relationship between bacterial diversity and pathogen load. We found that winter-sampled frogs and juveniles, two states associated with increased Bd susceptibility, exhibited higher diversity compared with summer-sampled frogs and adult individuals. Our findings also revealed that hosts harbouring higher bacterial diversity carried lower Bd infections, providing support for the protective role of bacterial communities. Ongoing work to understand skin microbiome resilience after pathogen disturbance has the potential to identify key taxa involved in disease resistance.
Data from: Historical amphibian declines and extinctions in Brazil linked to chytridiomycosis
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Data from: Seasonal and ontogenetic variation of skin microbial communities and relationships to natural disease dynamics in declining amphibians
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Data from: Human traffic and habitat complexity are strong predictors for the distribution of a declining amphibian
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Data from: Direct and indirect effects of pine silviculture on the larval occupancy and breeding of declining amphibian species
1. Plantation silviculture is increasing globally and is particularly intensive in temperate coniferous forests, where densely planting trees requires practices common to non-conifer systems that can alter forest floor microhabitat, and potentially threaten amphibian persistence. Most declining amphibian species depend on specific forest microhabitats as terrestrial refugia, but amphibian extirpation associated with tree harvest alone appears unlikely, suggesting that impacts of planting forests on groundcover might better predict recent declines in amphibian occupancy. 2. We repeatedly sampled larval presence or absence of 10 amphibian species native to temperate coniferous forest in the Southeastern United States for one year at 62 isolated wetlands located in either naturally regenerating or planted forest (plantation) to assess three direct ways that planted forests might reduce amphibian breeding site occupancy by: 1) increasing conifer densities, 2) decreasing groundcover, and 3) an indirect pathway, whereby increased tree densities at plantations might reduce groundcover and thus amphibian site occupancy. 3. After controlling for wetland traits and accounting for differences in detection, breeding site occupancy for 8/10 amphibian species was dependent upon whether forests were planted surrounding wetlands (within 300 m). Herbaceous groundcover, not canopy, most commonly influenced occupancy and increased occupancy for declining surface active or fossorial amphibians. 4. Path analyses showed that, by directly and indirectly reducing groundcover (via conifer densities), plantations had significantly lower occupancy of two declining surface active or fossorial frog species, whereas two common aquatic frog species were tolerant to planting conifers. Among declining species, salamanders showed a greater reduction in occupancy than anurans, likely because of greater vulnerability to the drier forest floor conditions of plantation than naturally regenerating forests. 5. Synthesis and applications: Direct negative impacts of coniferous plantation on amphibians can be addressed by limiting groundcover and soil impacts, including switching from high intensity practices, such as mechanical chopping vegetation or bedding soil, to lower intensity site preparation treatments that are less likely to significantly disturb groundcover. Indirect negative effects of dense canopy cover at planted forests could be lowered by periodically thinning canopies prior to final harvest, thus increasing intact forest groundcover and the conservation of both common and declining amphibians.
Data from: Direct and indirect effects of pine silviculture on the larval occupancy and breeding of declining amphibian species
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International Brain Laboratory public data
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OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.