Species-energy theory indicates that recent climate warming should have driven increases in species richness in cool and species-poor parts of the Northern Hemisphere. We confirm that the average species richness of British butterflies has increased since 1970–82, but much more slowly than predicted from changes of climate: on average, only one-third of the predicted increase has taken place. The resultant species assemblages are increasingly dominated by generalist species that were able to respond quickly. The time lag is confirmed by the successful introduction of many species to climatically suitable areas beyond their ranges. Our results imply that it may be decades or centuries before the species richness and composition of biological communities adjusts to the current climate.

Habitat loss and fragmentation are among the biggest threats to biodiversity. Anthropogenic habitat fragmentation leads to small and isolated remnant plant and animal populations. The combination of increased random genetic drift, inbreeding, and reduced gene flow may substantially reduce genetic variation of remnant populations. However, the magnitude of these responses may depend on several poorly understood factors including organism group, habitat type of both the fragment and the surrounding matrix, life‐history traits, and time since fragmentation. We compiled data for 83 plant and 52 animal species and conducted a meta‐analysis following best practices to evaluate how these factors mediate the effects of anthropogenic habitat fragmentation. We calculated 206 effect sizes as correlations between one of four measures of population‐level genetic diversity and fragment area. All analyses were repeated using models of increasing complexity (traditional random‐effects models, multilevel models accounting for non‐independent data, and multilevel models additionally correcting for phylogenetic relatedness). We confirmed that anthropogenic habitat fragmentation has overall negative effects on genetic diversity of organisms. Our meta‐analysis shows, however, that plant species responded in general stronger to fragmentation than animal species and that the largest negative impacts of fragmentation occurred in tropical and temperate forest fragments, surrounded by a non‐forest matrix. In contrast, we found only weak responses in non‐forest fragments. Genetic diversity measured as mean number of alleles (A) showed the strongest response to fragmentation. Expected heterozygosity (He) and percentage of polymorphic loci (PLP) showed similar but weaker responses. In contrast, our meta‐analysis indicated that inbreeding (Fis) was not measurably affected by anthropogenic habitat fragmentation. Additionally, our models revealed that effects on genetic diversity became stronger with age of fragments: We found significant negative responses for fragments older than 50 yr but not for those more recently isolated. Our meta‐analyses also showed that currently animals are underrepresented in the literature on genetic effects of anthropogenic fragmentation, as are certain geographical regions and habitat types. We expect that future field studies using state‐of‐the‐art approaches will provide further evidence of negative genetic effects, which may reinforce the here reported patterns, even for groups not yet studied.

Aim: In ectotherms, the colour of an individual's cuticle may have important thermoregulatory and protective consequences. In cool environments, ectotherms should be darker, to maximize heat gain, and larger, to minimize heat loss. Dark colours should also predominate under high UV‐B conditions because melanin offers protection. We test these predictions in ants (Hymenoptera: Formicidae) across space and through time based on a new, spatially and temporally explicit, global‐scale combination of assemblage‐level and environmental data.Location: Africa, Australia and South America.Methods: We sampled ant assemblages (n = 274) along 14 elevational transects on three continents. Individual assemblages ranged from 250 to 3000 m a.s.l. (minimum to maximum range in summer temperature of 0.5–35 °C). We used mixed‐effects models to explain variation in assemblage cuticle lightness. Explanatory variables were average assemblage body size, temperature and UV‐B irradiation. Annual temporal changes in lightness were examined for a subset of the data.Results: Assemblages with large average body sizes were darker in colour than those with small body sizes. Assemblages became lighter in colour with increasing temperature, but darkened again at the highest temperatures when there were high levels of UV‐B. Through time, temperature and body size explained variation in lightness. Both the spatial and temporal models explainedc. 50% of the variation in lightness.Main conclusions: Our results are consistent with the thermal melanism hypothesis, and demonstrate the importance of considering body size and UV‐B radiation exposure in explaining the colour of insect cuticle. Crucially, this finding is at the assemblage level. Consequently, the relative abundances and identities of ant species that are present in an assemblage can change in accordance with environmental conditions over elevation, latitude and relatively short time spans. These findings suggest that there are important constraints on how ectotherm assemblages may be able to respond to rapidly changing environmental conditions.

Urbanisation is increasing worldwide and is regarded a major driver of environmental change altering local species assemblages in urban green areas. Forests are one of the most frequent habitat types in urban landscapes harbouring many native species and providing important ecosystem services. By using a multi-taxa approach covering a range of trophic ranks, we examined the influence of degree of urbanisation and forest size on the species richness and functional diversity of plants, and ground surface-active ants and spiders. We conducted field surveys in twenty-six forests in the urban region of Basel, Switzerland. We found that a species’ response to urbanisation varied depending on trophic rank, habitat specificity and the diversity indices used. In plants, species richness decreased with degree of urbanisation, whereas that of both arthropod groups was not affected. However, ants and spiders at higher trophic rank showed greater shifts in species composition with increasing degree of urbanisation, and the percentage of forest specialists in both arthropod groups increased with forest size. Local abiotic site characteristics were also crucial for plant species diversity and species composition, while the structural diversity of both leaf litter and vegetation was important for the diversity of ants and spiders. Our results highlight that even small urban forests can harbour a considerable biodiversity including habitat specialists. Nonetheless, urbanisation directly and indirectly caused major shifts in species composition. Therefore, special consideration needs to be given to vulnerable species, including those with special habitat requirements. Locally adapted management practices could be a step forward to enhance habitat quality in a way to maximize diversity of forest species and thus ensure forest ecosystem functioning; albeit large-scale factors also remain important.