Effects of the interaction between genetic diversity and UV-B radiation on wood frog fitness

Importance of Genetic-Fitness Correlations for the Conservation of Amphibians

Endangered animals suffer from isolation of their habitats. Isolation leads to a reduction in population size as well as a decrease in genetic diversity and a concomitant increase in the risk of extinction. Amphibians are the most endangered vertebrate class. Besides habitat loss, fragmentation and isolation, amphibians are threatened by emerging diseases e.g., chytrid fungus or Ranavirus. By employing experiments, researchers investigate whether changes in genetic diversity within or among isolated populations affect amphibian fitness. While genetic diversity estimates are based on molecular markers, typically microsatellites, fitness is mostly measured as tadpole performance in rearing experiments often under varying environmental conditions. Tadpole performances (e.g., body mass, growth rate and survival) have been found to be negatively affected by low genetic diversity, as several studies have found a positive association between genetic diversity and these fitness traits. Moreover, infection with pathogens also seems to be more likely in individuals or populations with lower genetic diversity. Overall, these genetic-fitness correlations seem to be more pronounced or detectable in smaller, declining populations but not in larger populations. Genomic studies, which sample a larger fraction of the genome, are still scarce in the conservation genetic literature on amphibians. These are likely to increase in upcoming years and may reveal adaptive variants that protect against dangerous pathogens or environmental changes. Altogether, genetic-fitness correlation studies should be a priority in order to develop effective management plans for the genetic rescue of isolated, imperilled amphibian populations.

Gigantism in tadpoles and color anomalies in European green toad Bufotes viridis from Poland

Some new cases of anomalies in wild Bufotes viridis from Western Poland are presented together with a discussion of their potential causes and a comparison with similar cases from the literature. The anomalies in question are color aberrations (pre- and post-metamorphic) and developmental pathologies (pre–metamorphic). The color anomalies include an ochre patch in a juvenile, leucism and albinism in both tadpoles and juvenile individuals. Developmental pathologies described in this paper include gigantism, edema, curvature of tail, and asymmetric bodies.

Living with relatives offsets the harm caused by pathogens in natural populations

Living with relatives can be highly beneficial, enhancing reproduction and survival. High relatedness can, however, increase susceptibility to pathogens. Here, we examine whether the benefits of living with relatives offset the harm caused by pathogens, and if this depends on whether species typically live with kin. Using comparative meta-analysis of plants, animals, and a bacterium (nspecies = 56), we show that high within-group relatedness increases mortality when pathogens are present. In contrast, mortality decreased with relatedness when pathogens were rare, particularly in species that live with kin. Furthermore, across groups variation in mortality was lower when relatedness was high, but abundances of pathogens were more variable. The effects of within-group relatedness were only evident when pathogens were experimentally manipulated, suggesting that the harm caused by pathogens is masked by the benefits of living with relatives in nature. These results highlight the importance of kin selection for understanding disease spread in natural populations.

Unequal sisters - Past and potential future range development of Anatolian and Hyrcanian brown frogs

Phylogeography can reconstruct historical evolutionary processes by comparing historical patterns of gene flow, divergence among species and by using species distribution models (SDM) upon geographic distribution. We investigate the phylogeographic patterns of Anatolian brown frogs including R. macrocnemis and R. tavasensis as well as the Hyrcanian brown frog, R. pseudodalmatina, using a fragment of the mitochondrial 16S rRNA gene for 145 specimens across the entire range of these frogs. We calculate parameters of molecular diversity, such as the number of variable sites (S), the number of haplotypes (h), haplotype diversity (Hd) and nucleotide diversity (π). We generated a haplotype network and used three methods (Neutrality tests, mismatch distributions and Bayesian skyline plots) to reconstruct the demographic histories of R. macrocnemis and R. pseudodalmatina. Finally, we used SDMs to predict the habitat suitability for three periods: The Present Day, the Last Glacial Maximum (LGM) and the future until 2070 for R. macrocnemis and R. pseudodalmatina. Our phylogenetic analyses support a late Miocene origin of Anatolian and Hyrcanian lineages. Hyrcanian brown frogs were enclosed in lowlands of the southern coast of the Caspian Sea after the uplift of the Elburz range and the Armenian plateau. The formation of a salinity belt from the north Aegean corridor (the south western Turkey) to northward during the Late Tortonian led to the subdivision of ancestor of the Anatolian lineage into today isolated western and eastern populations. The salinity belt had a considerable impact on the divergence of R. tavasensis from R. macrocnemis. Combined historical demographic analyses and SDMs revealed a rapid expansion occurring during the Pleistocene in R. macrocnemis and R. pseudodalmatina. Currently, suitable habitat for R. macrocnemis has declined compared to the LGM, and the species is predicted to do even worse under future climatic conditions. In contrast, R. pseudodalmatina found suitable habitat from the LGM to present within its restricted distribution area; it is predicted to do fine even under future climate.

Effect of biogeographic history on population vulnerability in European amphibians

The genetic diversity of populations, which contributes greatly to their adaptive potential, is negatively affected by anthropogenic habitat fragmentation and destruction. However, continental-scale losses of genetic diversity also resulted from the population expansions that followed the end of the last glaciation, an element that is rarely considered in a conservation context. We addressed this issue in a meta-analysis in which we compared the spatial patterns of vulnerability of 18 widespread European amphibians in light of phylogeographic histories (glacial refugia and postglacial routes) and anthropogenic disturbances. Conservation statuses significantly worsened with distances from refugia, particularly in the context of industrial agriculture; human population density also had a negative effect. These findings suggest that features associated with the loss of genetic diversity in post-glacial amphibian populations (such as enhanced fixation load or depressed adaptive potential) may increase their susceptibility to current threats (e.g., habitat fragmentation and pesticide use). We propose that the phylogeographic status of populations (i.e., refugial vs. post-glacial) should be considered in conservation assessments for regional and national red lists.

Pheomelanin in the skin of Hymenochirus boettgeri (Amphibia: Anura: Pipidae)

Pheomelanin is supposed to be the first type of melanin found in vertebrates, in contrast to the main type - eumelanin. Our study aimed at detecting pheomelanin in the skin of Hymenochirus boettgerii. We employed electron paramagnetic resonance (EPR) spectroscopy, and transmission electron microscopy (TEM), supplemented with standard histology and immunochemistry. We identified pheomelanin in the dorsal skin of adult frogs (not only in the dermis, but also in the epidermis) and in the dorsal tadpole. Our work identifies Hymenochirus boettgerii as a model in the basic study on the mechanism, evolution and role of melanogenesis in animals, including human.

Effects of UV radiation on aquatic ecosystems and interactions with climate change

The health of freshwater and marine ecosystems is critical to life on Earth. The impact of solar UV-B radiation is one potential stress factor that can have a negative impact on the health of certain species within these ecosystems. Although there is a paucity of data and information regarding the effect of UV-B radiation on total ecosystem structure and function, several recent studies have addressed the effects on various species within each trophic level. Climate change, acid deposition, and changes in other anthropogenic stressors such as pollutants alter UV exposure levels in inland and coastal marine waters. These factors potentially have important consequences for a variety of aquatic organisms including waterborne human pathogens. Recent results have demonstrated the negative impacts of exposure to UV-B radiation on primary producers, including effects on cyanobacteria, phytoplankton, macroalgae and aquatic plants. UV-B radiation is an environmental stressor for many aquatic consumers, including zooplankton, crustaceans, amphibians, fish, and corals. Many aquatic producers and consumers rely on avoidance strategies, repair mechanisms and the synthesis of UV-absorbing substances for protection. However, there has been relatively little information generated regarding the impact of solar UV-B radiation on species composition within natural ecosystems or on the interaction of organisms between trophic levels within those ecosystems. There remains the question as to whether a decrease in population size of the more sensitive primary producers would be compensated for by an increase in the population size of more tolerant species, and therefore whether there would be a net negative impact on the absorption of atmospheric carbon dioxide by these ecosystems. Another question is whether there would be a significant impact on the quantity and quality of nutrients cycling through the food web, including the generation of food proteins for humans. Interactive effects of UV radiation with changes in other stressors, including climate change and pollutants, are likely to be particularly important.

Chronic exposure of Rana pipiens tadpoles to UVB radiation and the estrogenic chemical 4-tert-octylphenol

While adverse effects of exposure to ultraviolet B radiation (UVBR) and environmental pollutants on amphibians have been documented, few studies examined the effects of interactions between environmental stressors on amphibian health. Here the impacts of chronic exposure to UVBR and the estrogenic chemical 4-tert-octylphenol (OP), alone and in combination, on the survival, development, growth, and metamorphosis of Rana pipiens (northern leopard frog) tadpoles are evaluated. Tadpoles were exposed to environmentally relevant levels of OP (0.01 or 10 nM), with and without exposure to UVBR (approximately 0.22 W/m2). After 8 mo of exposure, animals were transferred to a clean-water grow-out system for 3 additional mo. There was no effect of treatments on the weights of animals at wk 42 or on the age, snout-vent length (SVL), and weights of tadpoles at forelimb emergence (FLE). However, tadpoles exposed to UVBR had markedly delayed development and significantly fewer reached metamorphosis compared to control animals. Although exposure to UVBR and OP together produced the highest incidence of mortality and developmental anomalies, UVBR alone was sufficient to produce significant mortality of tadpoles, and exposure to UVBR or OP alone induced a significant increase in malformations and abnormalities. The malformations observed consisted mainly of spinal curvature. Our results show that chronic exposure to environmental levels of UVBR or OP alone exerts lethal and/or sublethal effects on R. pipiens tadpoles.