Nucleotide diversity patterns of local adaptation at drought‐related candidate genes in wild tomatoes

We surveyed nucleotide diversity at two candidate genes LeNCED1 and pLC30‐15, involved in an ABA (abscisic acid) signalling pathway, in two closely related tomato species Solanum peruvianum and Solanum chilense. Our six population samples (three for each species) cover a range of mesic to very dry habitats. The ABA pathway plays an important role in the plants’ response to drought stress. LeNCED1 is an upstream gene involved in ABA biosynthesis, and pLC30‐15 is a dehydrin gene positioned downstream in the pathway. The two genes show very different patterns of nucleotide variation. LeNCED1 exhibits very low nucleotide diversity relative to the eight neutral reference loci that were previously surveyed in these populations. This suggests that strong purifying selection has been acting on this gene. In contrast, pLC30‐15 exhibits higher levels of nucleotide diversity and, in particular in S. chilense, higher genetic differentiation between populations than the reference loci, which is indicative of local adaptation. In the more drought‐tolerant species S. chilense, one population (from Quicacha) shows a significant haplotype structure, which appears to be the result of positive (diversifying) selection.     

Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciation

High-alpine life forms and ecosystems exist at the limits of habitable environments, and thus, are especially sensitive to environmental change. Here we report a recent increase in the elevational limit of anurans following glacial retreat in the tropical Peruvian Andes. Three species have colonized ponds in recently deglaciated terrain at new record elevations for amphibians worldwide (5244–5400 m). Two of these species were also found to be infected with Batrachochytrium dendrobatidis ( Bd ), an emerging fungal pathogen causally associated with global amphibian declines, including the disappearance of several Latin American species. The presence of this pathogen was associated with elevated mortality rates of at least one species. These results represent the first evidence of upward expansion of anurans to newly available habitat brought about by recent deglaciation. Furthermore, the large increase in the upper limit of known Bd infections, previously reported as 4112 m in Ecuador, to 5348 m in this study, also expands the spatial domain of potential Bd pathogenicity to encompass virtually all high elevation anuran habitats in the tropical Andes.     

The impact of sarcoptic mange Sarcoptes scabiei on the British fox Vulpes vulpes population

• 1 Disease epizootics can significantly influence host population dynamics and the structure and functioning of ecological communities. Sarcoptic mange Sarcoptes scabiei has dramatically reduced red fox populations Vulpes vulpes in several countries, including Britain, although impacts on demographic processes are poorly understood. We review the literature on the impact of mange on red fox populations, assess its current distribution in Britain through a questionnaire survey and present new data on resultant demographic changes in foxes in Bristol, UK.
• 2 A mange epizootic in Sweden spread across the entire country in < 10 years resulting in a decline in fox density of up to 95%; density remained lowered for 15–20 years. In Spain, mange has been enzootic for > 75 years and is widely distributed; mange presence was negatively correlated with habitat quality.
• 3 Localized outbreaks have occurred sporadically in Britain during the last 100 years. The most recent large‐scale outbreak arose in the 1990s, although mange has been present in south London and surrounding environs since the 1940s. The questionnaire survey indicated that mange was broadly distributed across Britain, but areas of perceived high prevalence (> 50% affected) were mainly in central and southern England. Habitat type did not significantly affect the presence/absence of mange or perceived prevalence rates. Subjective assessments suggested that populations take 15–20 years to recover.
• 4 Mange appeared in Bristol's foxes in 1994. During the epizootic phase (1994–95), mange spread through the city at a rate of 0.6–0.9 km/month, with a rise in infection in domestic dogs Canis familiaris c. 1–2 months later. Juvenile and adult fox mortality increased and the proportion of females that reproduced declined but litter size was unaffected. Population density declined by > 95%.
• 5 In the enzootic phase (1996–present), mange was the most significant mortality factor. Juvenile mortality was significantly higher than in the pre‐mange period, and the number of juveniles classified as dispersers declined. Mange infection reduced the reproductive potential of males and females: females with advanced mange did not breed; severely infected males failed to undergo spermatogenesis. In 2004, Bristol fox population density was only 15% of that in 1994.

     

Parental,social and environmental factors associated with hatching failure in Florida Scrub‐Jays Aphelocoma coerulescens

Hatching failure within clutches of eggs occurs to varying degrees in many avian species. We investigated predictors of hatching failure in a population of Florida Scrub‐Jays, for which hatching success has been monitored for 15 years. We assessed whether hatching failure was related to parental traits (e.g. age, experience as a pair or body condition), lay date, social structure (e.g. number of helpers), environmental conditions, or some combination of these. We used linear mixed models and Akaike’s information criterion to determine the models that best explain observed patterns of hatching failure. The best model showed that increased hatching failure was associated with below‐average rainfall during the breeding season, and was more common for newly established breeding pairs than for pairs that had previously produced one or more clutches together. Other contributing models suggested that hatching failure was greatest for the youngest and oldest female breeders. Some aspects of our findings are consistent with conclusions drawn from other species. However, as a whole, our analyses suggest that hatching failure in the Florida Scrub‐Jay is influenced by a complex set of environmental and parental factors.     

DIFFERENCES IN RESTING-SITE PREFERENCE IN TWO COEXISTING LAND SNAILS, ARIANTA ARBUSTORUM AND ARIANTA CHAMAELEON (HELICIDAE), ON ALPINE SLOPES

Resting-site preference and patterns of spatial distributionwere examined in the sympatric land snails Arianta arbustorumand A. chamaeleon on two opposite slopes in the south-easternAlps, Austria. The two slopes did not differ in proportion ofA. arbustorum and A. chamaeleon (74.4% vs. 25.6% on the NNE-exposedslope and 68.3% vs. 31.7% on the SSW-exposed slope). Individualsof both species showed aggregated dispersion patterns. The nearest-neighbourmethod indicated that in both species snail aggregations predominantlyconsisted either of A. arbustorum or A. chamaeleon on the NNE-exposedslope with a mosaic of rocks and distinct patches of differentplants. On the SSW-exposed slope, which was less variable invegetation cover, snail aggregations consisted of conspecificand hetero-specific individuals. Juvenile and adult A. arbustorumpreferred to rest attached to leaves of Adenostyles alliariae,but avoided rock surfaces and patches of grass on the NNE-exposedslope. In contrast, juvenile and adult A. chamaeleon preferentiallyrested on rock surfaces, and also avoided grass patches. Juvenileand adult A. chamaeleon did not differ in resting-site preference,whereas small differences in resting sites were observed betweenjuvenile and adult A. arbustorum. Differences in resting-sitepreference is one way of niche differentiation which may allowindividuals of the two Arianta species to coexist. (Received 14 March 1996; accepted 8 July 1996)