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Changes in physiology and microbial diversity in larval ornate chorus frogs are associated with habitat quality.

ABSTRACT: Environmental change associated with anthropogenic disturbance can lower habitat quality, especially for sensitive species such as many amphibians. Variation in environmental quality may affect an organism's physiological health and, ultimately, survival and fitness. Using multiple health measures can aid in identifying populations at increased risk of declines. Our objective was to measure environmental variables at multiple spatial scales and their effect on three indicators of health in ornate chorus frog (Pseudacris ornata) tadpoles to identify potential correlates of population declines. To accomplish this, we measured a glucocorticoid hormone (corticosterone; CORT) profile associated with the stress response, as well as the skin mucosal immune function (combined function of skin secretions and skin bacterial community) and bacterial communities of tadpoles from multiple ponds. We found that water quality characteristics associated with environmental variation, including higher water temperature, conductivity and total dissolved solids, as well as percent developed land nearby, were associated with elevated CORT release rates. However, mucosal immune function, although highly variable, was not significantly associated with water quality or environmental factors. Finally, we examined skin bacterial diversity as it aids in immunity and is affected by environmental variation. We found that skin bacterial diversity differed between ponds and was affected by land cover type, canopy cover and pond proximity. Our results indicate that both local water quality and land cover characteristics are important determinants of population health for ornate chorus frogs. Moreover, using these proactive measures of health over time may aid in early identification of at-risk populations that could prevent further declines and aid in management decisions.

SUBMITTER: Goff CB

PROVIDER: S-EPMC7294888 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundSpecies interactions can promote mating behavior divergence, particularly when these interactions are costly due to maladaptive hybridization. Selection against hybridization can indirectly cause evolution of reproductive isolation within species, a process termed cascade reinforcement. This process can drive incipient speciation by generating divergent selection pressures among populations that interact with different species assemblages. Theoretical and empirical studies indicate that divergent selection on gene expression networks has the potential to increase reproductive isolation among populations. After identifying candidate synaptic transmission genes derived from neurophysiological studies in anurans, we test for divergence of gene expression in a system undergoing cascade reinforcement, the Upland Chorus Frog (Pseudacris feriarum).ResultsOur analyses identified seven candidate synaptic transmission genes that have diverged between ancestral and reinforced populations of P. feriarum, including five that encode synaptic vesicle proteins. Our gene correlation network analyses revealed four genetic modules that have diverged between these populations, two possessing a significant concentration of neurotransmission enrichment terms: one for synaptic membrane components and the other for metabolism of the neurotransmitter nitric oxide. We also ascertained that a greater number of genes have diverged in expression by geography than by sex. Moreover, we found that more genes have diverged within females as compared to males between populations. Conversely, we observed no difference in the number of differentially-expressed genes within the ancestral compared to the reinforced population between the sexes.ConclusionsThis work is consistent with the idea that divergent selection on mating behaviors via cascade reinforcement contributed to evolution of gene expression in P. feriarum. Although our study design does not allow us to fully rule out the influence of environment and demography, the fact that more genes diverged in females than males points to a role for cascade reinforcement. Our discoveries of divergent candidate genes and gene networks related to neurotransmission support the idea that neural mechanisms of acoustic mating behaviors have diverged between populations, and agree with previous neurophysiological studies in frogs. Increasing support for this hypothesis, however, will require additional experiments under common garden conditions. Our work points to the importance of future replicated and tissue-specific studies to elucidate the relative contribution of gene expression divergence to the evolution of reproductive isolation during incipient speciation.

Project description:Reinforcement contact zones, which are secondary contact zones where species are diverging in reproductive behaviors due to selection against hybridization, represent natural laboratories for studying speciation-in-action. Here, we examined replicate localities across the entire reinforcement contact zone between North American chorus frogs Pseudacris feriarum and P. nigrita to investigate geographic variation in hybridization frequencies and to assess whether reinforcement may have contributed to increased genetic divergence within species. Previous work indicated these species have undergone reproductive character displacement (RCD) in male acoustic signals and female preferences due to reinforcement. We also examined acoustic signal variation across the contact zone to assess whether signal characteristics reliably predict hybrid index and to elucidate whether the degree of RCD predicts hybridization rate. Using microsatellites, mitochondrial sequences, and acoustic signal information from >1,000 individuals across >50 localities and ten sympatric focal regions, we demonstrate: (1) hybridization occurs and (2) varies substantially across the geographic range of the contact zone, (3) hybridization is asymmetric and in the direction predicted from observed patterns of asymmetric RCD, (4) in one species, genetic distance is higher between conspecific localities where one or both have been reinforced than between nonreinforced localities, after controlling for geographic distance, (5) acoustic signal characters strongly predict hybrid index, and (6) the degree of RCD does not strongly predict admixture levels. By showing that hybridization occurs in all sympatric localities, this study provides the fifth and final line of evidence that reproductive character displacement is due to reinforcement in the chorus frog contact zone. Furthermore, this work suggests that the dual action of cascade reinforcement and partial geographic isolation is promoting genetic diversification within one of the reinforced species.

Project description:BackgroundUnderstanding the ecology of larval malaria and lymphatic filariasis mosquitoes in a changing environment is important in developing effective control tools or programmes. This study characterized the breeding habitats of Anopheles mosquitoes in rural communities in different ecological zones in Ghana during the dry and rainy seasons.MethodsThe spatio-temporal distribution, species composition, and abundance of larval Anopheles mosquitoes in breeding habitats were studied in five locations in three ecological zones of Ghana. These were Anyakpor (coastal savannah area), Duase (forest area), and Libga, Pagaza, and Kpalsogu (Sahel savannah area). Larvae were collected using standard dippers and were raised in the insectary for identification.ResultsOut of a total of 7984 mosquito larvae collected, 2152 (27.26%) were anophelines and were more abundant in the rainy season (70.82%) than in the dry season (29.18%). The anophelines comprised 2128 (98.88%) An. gambiae s.l., 16 (0.74%) An. rufipes, and 8 (0.37%) An. pharoensis. In the coastal savannah and forest zones, dug-out wells were the most productive habitat during the dry (1.59 larvae/dip and 1.47 larvae/dip) and rainy seasons (11.28 larvae/dip and 2.05 larvae/dip). Swamps and furrows were the most productive habitats in the Sahel savannah zone during the dry (0.25 larvae/dip) and rainy (2.14 larvae/dip) seasons, respectively. Anopheles coluzzii was the most abundant sibling species in all the ecological zones. Anopheles melas and An. arabiensis were encountered only in the coastal savannah and the Sahel savannah areas, respectively. Larval habitat types influenced the presence of larvae as well as larval density (p < 0.001). The land-use type affected the presence of Anopheles larvae (p = 0.001), while vegetation cover influenced larval density (p < 0.05).ConclusionThe most productive habitats were dug-out wells in the coastal savannah and forest zones, and furrows from irrigated canals in the Sahel savannah zone. Anopheles coluzzii was the predominant vector species in all the ecological zones. The abundance of Anopheles breeding habitats and larvae were influenced by anthropogenic activities. Encouraging people whose activities create the larval habitats to become involved in larval source management such as habitat manipulation to stop mosquito breeding will be important for malaria and lymphatic filariasis control.

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Changes in physiology and microbial diversity in larval ornate chorus frogs are associated with habitat quality.

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