Unusual lack of reproduction in toad populations from agricultural habitats

Anthropogenic alterations of habitats can have detrimental consequences for biodiversity. Documenting these effects require monitoring in multiple sites that vary in the degree of alterations over long temporal scales, a task that is challenging. Yet, simple naturalist observations can reveal major ongoing events affecting wild populations, and serve as a basis for further investigations. We quantified breeding parameters of spined toad (Bufo spinosus) populations from forested (preserved) and agricultural (altered) habitats. We found that reproduction did not occur at the sites surrounded by agriculture, while it occurred successfully in ponds from forests. Males were present at all sites, but females, amplexus, egg strings and tadpoles remained absent from agricultural sites. Observations made at the same sites indicated that breeding occurred during previous years. Our observations of habitat- and sex-specific lack of reproduction may have critical consequences for the persistence of populations of a widespread amphibian species in agricultural areas.

Intra-Body Variations of Stable Isotope Ratios (δ13C, δ15N) and Influence of Storage Methods in Aquatic and Post-Aquatic Stages of the Common Toad, Bufo bufo

Isotopic signatures of carbon and nitrogen are widely used for analysis of the structure of food webs in aquatic ecosystems. The study of animals raises a number of methodological questions, including choice of representative tissues and organs for sampling as well as storage of the studied organisms. Furthermore, the impacts of preservation methods can be tissue-specific, age-specific, and even taxon-specific; thus, studies of these impacts on particular taxa are necessary. We focused on the C and N isotope composition of the common toad (Bufo bufo), one of the most widespread European anuran amphibians. We hypothesized that its different tissues and organs may vary in isotopic composition, and ethanol and freezing may have different effects on isotopic values. Our results showed that both “tissue” and “storage method” factors significantly affected the δ13C values of tadpoles and postmetamorphic juveniles, whereas only the “tissue” factor had a significant effect on the δ15N values. The two stages, tadpoles and postmetamorphs, should be analyzed separately despite the brief postmetamorphic period of the juveniles. The skin, legs, muscles, and tail in tadpoles and legs, muscles and heart in juveniles can be used for δ13C and δ15N analysis regardless of the method of storage. The results will serve for the optimization of future study designs in isotopic ecology.

Smooth newt Lissotriton vulgaris and common toad Bufo bufo populations persisting in the unusually small area of Sommers Island in the Baltic Sea

Sommers Island is an abandoned 20 ha patch of land in the Baltic Sea. It is inhabited by isolated populations of smooth newt (Lissotriton vulgaris) and common toad (Bufo bufo). The island demonstrates the small area in which it is possible to have a stable population of newts and toads for a period of at least several decades, probably much longer. Most reproduction of both species occurred in one pool with an area of about 100 m². The total area of optimal terrestrial habitat is about 2.5 ha, with an additional 3.5 ha of sub-optimal habitat available. The island is inhabited by about 123 adult newts and several dozen adult toads.

Reinforcement alone does not explain increased reproductive isolation in sympatry

Comparative studies of reproductive isolation (RI) by Coyne and Orr (1, 2) and others indicate a significant role for reinforcing natural selection in Drosophila speciation. The reinforcement hypothesis predicts increased prezygotic, but not postzygotic, RI between sympatric species pairs in response to maladaptive hybridization. We revisit this hypothesis and others using additional Drosophila, Lepidopteran, and toad (Bufo) data. In contrast to the predictions of reinforcement, we find increased premating and postzygotic RI between sympatric Drosophila species, including between recently diverged species pairs, as defined by Coyne and Orr (1) and others (i.e., DNei < 0.5). However, at slightly lower divergence thresholds increased postzygotic RI in sympatry is not statistically significant, while increased premating RI is, generally in agreement with the predictions of reinforcement. While premating data are unavailable, postzygotic RI is also increased between sympatric Lepidopteran and toad (Bufo) species. We find only modest support for 'concordant asymmetries' in premating and postzygotic RI between sympatric Drosophila, described by others as uniquely supporting reinforcement. Finally, the proportion of geographic range overlap shared by species is positively associated with the magnitude of premating RI as predicted by reinforcement, but it is also positively associated with postzygotic RI, which cannot be explained by reinforcement. Taken together, our results demonstrate that comparisons of premating and postzygotic RI in sympatry depend greatly on divergence time, and suggest that fusion, extinction, and/or other mechanisms must combine with reinforcement to generate these patterns.

First distribution record of the Asiatic Toad Bufo gargarizans Cantor, 1842 from India — Dibang Valley in Arunachal Pradesh

Bufo gargarizans, a species complex, has a wide distribution ranging from Japan to south-western China, Vietnam, and Russia but was not previously reported from India. Surveys conducted in Dibang Valley district of Arunachal Pradesh near the Indo-Tibetan border with China in 2014–15 revealed previously unreported specimens of the toad genus Bufo. Based on photographic comparisons with morphological characteristics obtained from published literature, we have identified the Bufo from Dibang Valley as the Asiatic Toad Bufo gargarizans Cantor, 1842. Individuals of the species reported from Dibang have a wide mid dorsal line in the dorsum, rarely observed in Bufo gargarizans except in the sub-populations on the Tibetan Plateau.