Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary process driving adaptationnatural selection-are largely unknown. We report that aspects of precipitation and potential evapotranspiration, along with the North Atlantic Oscillation, predicted variation in selection across plant and animal populations throughout many terrestrial biomes, whereas temperature explained little variation. By showing that selection was influenced by climate variation, our results indicate that climate change may cause widespread alterations in selection regimes, potentially shifting evolutionary trajectories at a global scale.C limate affects organisms in ways that ultimately shape patterns of biodiversity (1). Consequently, the rapid changes in Earth's recent climate impose challenges for many organisms, often reducing population fitness (2-4). Although some species may migrate and undergo range shifts to avoid climate-induced declines and potential extinction (5), an alternative outcome is adaptive evolution in response to selection imposed by climate (6). However, we lack a general understanding of whether local and global climatic factors such as temperature, precipitation, and water availability influence selection (2, 7). Understanding these effects is critical for predicting the consequences of increasing droughts, heat waves, and extreme precipitation events that are expected in many regions (8, 9).To quantify how climate variation influences selection, we assembled a large database of standardized directional selection gradients and differentials from spatially [mean = 4.6 ± 5.4 (SD) populations, range = 2 to 59 populations] and temporally [mean = 5.2 ± 6.8 (SD) years, range = 2 to 45 years] replicated selection studies (N = 168) in plant and animal populations (Table 1 and database S1). We focused on directional selection that can generate increases or decreases in trait values because it is well characterized and is likely to drive rapid evolution (10) in response to variation in climatic factors. However, selection acting on trait combinations and trait variance may also be affected by climate (7). Selection gradients estimate the strength and direction of selection acting directly on a trait, whereas differentials estimate "total selection" on a trait via both direct and indirect selection because of trait correlations (11). These standardized selection coefficients describe selection in terms of the relationship between relative fitness and quantitative traits measured in standard deviations, thus facilitating cross-study comparisons (11,12).Geographically, the database contains many estimates of selection from temperate, mid-latitude regions centered at 40°N (Fig. 1A). The populations in this database span many terrestrial biomes on Earth, with the exception of tundra and tropical rainforests where selection has rarely been quantified (Fig. 1B...

Summary 0[ In social mammals where group members cooperate to detect predators and raise young\ members of small groups commonly show higher mortality or lower breeding success than members of large ones[ It is generally assumed that this is because large group size allows individuals to detect or repel predators more e}ectively but other bene_ts of group size may also be involved\ including reduced costs of raising young and more e}ective competition for resources with neighbouring groups[ 1[ To investigate the extent to which predation rate a}ects survival\ we compared mortality rates in two populations of suricates "Suricata suricatta#\ one living in an area of high predator density "Kalahari Gemsbok Park# and one living in an area of relatively low predator density "neighbouring ranchland#[ Most aspects of feeding ecology and growth "including time spent feeding\ daily weight gain\ growth\ adult body weight\ breeding frequency and neonatal mortality# were similar in the two populations[ In contrast\ mortality of animals over 2 months old was 0=6 times higher in the Park than on ranchland[ 2[ Mortality of juveniles between emergence from the natal burrow and 5 months of age was higher in small groups than large ones in the Park but signi_cantly lower in small groups than large ones on ranchland[ Adult mortality declined in larger groups in both areas[ 3[ The tendency for survival to be low in small groups had far!reaching consequences for the risk of group extinction[ During a year of low rainfall in the Park\ all groups of less than nine animals became extinct and population density declined to around a third of its initial level[ We argue that high group extinction rates are to be expected in species where survival declines in small groups and mortality rates are high[ Key!words] cooperative breeding\ demography\ mammals\ mortality[ Journal of Animal Ecology "0888# 57\ 561Ð572

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Evolution generates a remarkable breadth of living forms, but many traits evolve repeatedly, by still poorly understood mechanisms. A classic example of repeated evolution is the loss of pelvic hindfins in stickleback fish (Gasterosteus aculeatus). Repeated pelvic loss maps to recurrent deletions of a pelvic enhancer of the Pitx1 gene. Here, we identify molecular features contributing to these recurrent deletions. Pitx1 enhancer sequences form alternative DNA structures in vitro, and increase double-strand breaks and deletions in vivo. Enhancer mutability depends on DNA replication direction and is caused by (TG)-dinucleotide repeats. Modeling shows that elevated mutation rates can influence evolution under demographic conditions relevant for sticklebacks and humans. DNA fragility may thus help explain why the same loci are often used repeatedly during parallel adaptive evolution.

Functional interpretations of helping behaviour suggest that it has evolved because helpers increase their direct or indirect fitness by helping. However, recent critiques have suggested that helping may be an unselected extension of normal parental behaviour, pointing to evidence that all mature individuals commonly respond to begging young (whether they are parents, relatives or non-relatives) as well as to the lack of evidence that cooperative activities have appreciable costs to helpers. Here we provide an example of one form of cooperative behaviour that is seldom performed by parents and has substantial energetic costs to helpers. In the cooperative mongoose, Suricata suricatta, non-breeding adults commonly babysit young pups at the natal burrow for a day at a time, foregoing feeding for 24 hours. Parents rarely contribute to babysitting, and babysitting has substantial energetic costs to helpers. Members of small groups compensate for the reduced number of participants by babysitting more frequently, and neither the proportion of time that babysitters are present nor the survival of litters vary with group size.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Though models of life-history decisions are traditionally based on age-related changes in the costs and benefits of reproduction, in nature both costs and benefits vary with individual differences in phenotype as well as with environmental changes. Using long-term records of individual reproduction and survival in the Soay sheep of St Kilda, we show that the costs and benefits of breeding to animals of different weight categories vary with population density.3. Subsequently, we use stochastic dynamic programming to predict the optimal fecundity of animals belonging to each category at high and low population density. Optimal strategies of fecundity vary with population density as well as between different weight categories of sheep. However, there is no evidence that the sheep track density-related changes in optimal fecundity. Instead, their behaviour approximates to an average, weight-related optimum that is well adapted to the range of conditions that they encounter.

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Allelic variation at seven hypervariable tri- and tetranucleotide microsatellite loci was used to determine levels of population differentiation between 14 populations of red grouse (Lagopus lagopus scoticus) in northeast Scotland, UK. Despite the potential for long-distance dispersal in grouse, and a semicontinuous habitat, significant population divergence was observed (mean RST = 0.153; P < 0.01) and an isolation-by-distance effect detected (Mantel test: P < 0.001). Examination of the spatial trend in principal component scores derived from allele frequencies among populations highlighted a barrier to gene flow that was confounding a simple isolation-by-distance effect. This barrier corresponded to an area of unsuitable habitat for grouse associated with a river system that bisected the study area. Mean genetic relatedness was higher for males than for females in all but one of the study populations, suggesting that the territorial behaviour and natal philopatry displayed by cocks have a manifold effect in generating the observed spatial genetic structure. Lower female relatedness values suggest a higher level of female-mediated gene flow, which is sufficient to prevent the loss of genetic variation from within populations and the onset of inbreeding effects. The potential consequences of local subdivision for red grouse populations are discussed.