Phenological delay despite warming in wood frog Rana sylvatica reproductive timing: a 20-year study

Across all taxa, amphibians exhibit some of the strongest phenological shifts in response to climate change. As climates warm, amphibians and other animals are expected to breed earlier in response to temperature cues. However, if species use fixed cues such as daylight, their breeding timing might remain fixed, potentially creating disconnects between their life history and environmental conditions. Wood frogs Rana sylvatica are a cold-adapted species that reproduce in early spring, immediately after breeding ponds are free of ice. We used long-term surveys of wood frog oviposition timing in 64 breeding ponds over 20 yr to show that, despite experiencing a warming of 0.29°C per decade in annual temperature, wood frog breeding phenology has shifted later by 2.8 d since 2000 (1.4 d per decade; 4.8 d per °C). This counterintuitive pattern is likely the result of changes in the timing of snowpack accumulation and melting. Finally, we used relationships between climate and oviposition between 2000 and 2018 to hindcast oviposition dates from climate records to model longer-term trends since 1980. Our study indicates that species can respond to fine-grained seasonal climate heterogeneity within years that is not apparent or counterintuitive when related to annual trends across years.     

Localized hypoxia may have caused coral reef mortality at the Flower Garden Banks

Coral Reefs - On July 25, 2016, turbid water and dead corals, sponges and other invertebrates were discovered at the East Bank (EB) of the Flower Garden Banks (FGB) National Marine Sanctuary....     

Microgeographical variation in thermal preference by an amphibian

Ectotherms use behaviour to buffer effects of temperature on growth, development and survival. While behavioural thermoregulation is widely reported, localized adaptation of thermal preference is poorly documented. Larval amphibians live in wetlands ranging from entirely open to heavily shaded by vegetation. We hypothesized that populations undergo localized selection leading to countergradient patterns of thermal preference behaviour. Specifically, we predicted that wood frog (Rana sylvatica) larvae from closed canopy ponds would be more strongly temperature selective and would prefer higher temperatures than conspecifics from populations found in open canopy ponds. In a study of six breeding ponds in north‐eastern Connecticut, USA, these predictions were upheld. The countergradient, microgeographical variation in thermal preference documented here implies that wood frog populations may have diverged rapidly in the face of contrasting selection pressures. Rapid, behaviourally mediated responses to changing thermal environments have important implications for understanding population responses to climate change.     

An MΨ-Containing Heterologous RNA, but Not env mRNA, Is Efficiently Packaged into Avian Retroviral Particles

Retroviruses preferentially package full-length genomic RNA over spliced viral messages. For most retroviruses, this preference is likely due to the absence of all or part of the packaging signal on subgenomic RNAs. In avian leukosis-sarcoma virus, however, we have shown that the minimal packaging signal, MPsi, is located upstream of the 5' splice site and therefore is present on both genomic and spliced RNAs. We now show that an MPsi-containing heterologous RNA is packaged only 2.6-fold less efficiently than genomic Rous sarcoma virus RNA. Thus, few additional packaging sequences and/or structures exist outside of MPsi. In contrast, we found that env mRNA is not efficiently packaged. These results indicate that either MPsi is not functional on this RNA or the RNA is somehow segregated from the packaging machinery. Finally, deletion of sequences from the 3' end of MPsi was found to reduce the packaging efficiency of heterologous RNAs.     

Ribeiroia Infection Is Not Responsible for Vermont Amphibian Deformities

Reports of limb deformities in amphibians have garnered wide notice from scientists and the public alike. Recent laboratory and field research has supported the hypothesis that infection by the helminth parasite, Ribeiroia ondatrae, is associated with deformities, particularly in the western United States. In this study, observational and experimental evidence from eastern United States (Vermont) provides evidence that Ribeiroia is absent from a large sample of sites including those with a history of relatively high frequencies of deformity, that the composition of deformities is distinct from that associated with experimental infection by Ribeiroia, and that the composition of limb deformities seen in natural populations in Vermont is typical of that reported in the literature. We suggest that while Ribeiroia has been shown to be responsible for deformities in some species and locations, other factors may be responsible where the composition of deformities is inconsistent with patterns resulting from known Ribeiroia infection.     

Canopy closure and amphibian diversity in forested wetlands

The crowns of trees and shrubs often overtop temporary wetlands in forested regions. By shading pond basins, canopy can dramatically change the conditions experienced by residents such as amphibians. In this study, we estimated the presence of 8 amphibian species across 17 temporary wetlands at the Yale–Myers Forest in northeastern Connecticut, USA. In addition, we quantified the light environment using a grid of hemispherical canopy photographs to calculate Global Site Factor (GSF) within each wetland. Amphibian richness was low in most wetlands, and most wetlands were relatively shaded. Amphibian richness increased in lighter wetlands. This result was not confounded by relationships with wetland size. Most amphibian species tended to be absent from heavily shaded wetlands (‘open canopy specialists’). However, three species were often found in the shadiest wetlands (‘canopy generalists’). Field transplant experiments using one canopy generalist and one open canopy specialist showed that development of the generalist was less affected by wetland light levels compared with performance of the specialist. These findings suggest that canopy may be an important determinant of amphibian diversity patterns across wetlands. Further, conservation strategies dependent on universally applied, inviolate shoreline vegetation buffers may inadvertently contribute to species loss. Because species differ in their sensitivity to changes in canopy, these losses may be predictable.