Tom H. Oliver

Protected areas facilitate species’ range expansions

The benefits of protected areas (PAs) for biodiversity have been questioned in the context of climate change because PAs are static, whereas the distributions of species are dynamic. Current PAs may, however, continue to be important if they provide suitable locations for species to colonize at their leading-edge range boundaries, thereby enabling spread into new regions. Here, we present an empirical assessment of the role of PAs as targets for colonization during recent range expansions. Records from intensive surveys revealed that seven bird and butterfly species have colonized PAs 4.2 (median) times more frequently than expected from the availability of PAs in the landscapes colonized. Records of an additional 256 invertebrate species with less-intensive surveys supported these findings and showed that 98% of species are disproportionately associated with PAs in newly colonized parts of their ranges. Although colonizing species favor PAs in general, species vary greatly in their reliance on PAs, reflecting differences in the dependence of individual species on particular habitats and other conditions that are available only in PAs. These findings highlight the importance of current PAs for facilitating range expansions and show that a small subset of the landscape receives a high proportion of colonizations by range-expanding species.

Long-term changes to the frequency of occurrence of British moths are consistent with opposing and synergistic effects of climate and land-use changes

Summary Species’ distributions are likely to be affected by a combination of environmental drivers. We used a data set of 11 million species occurrence records over the period 1970–2010 to assess changes in the frequency of occurrence of 673 macro‐moth species in Great Britain. Groups of species with different predicted sensitivities showed divergent trends, which we interpret in the context of land‐use and climatic changes. A diversity of responses was revealed: 260 moth species declined significantly, whereas 160 increased significantly. Overall, frequencies of occurrence declined, mirroring trends in less species‐rich, yet more intensively studied taxa. Geographically widespread species, which were predicted to be more sensitive to land use than to climate change, declined significantly in southern Britain, where the cover of urban and arable land has increased. Moths associated with low nitrogen and open environments (based on their larval host plant characteristics) declined most strongly, which is also consistent with a land‐use change explanation. Some moths that reach their northern (leading edge) range limit in southern Britain increased, whereas species restricted to northern Britain (trailing edge) declined significantly, consistent with a climate change explanation. Not all species of a given type behaved similarly, suggesting that complex interactions between species’ attributes and different combinations of environmental drivers determine frequency of occurrence changes. Synthesis and applications. Our findings are consistent with large‐scale responses to climatic and land‐use changes, with some species increasing and others decreasing. We suggest that land‐use change (e.g. habitat loss, nitrogen deposition) and climate change are both major drivers of moth biodiversity change, acting independently and in combination. Importantly, the diverse responses revealed in this species‐rich taxon show that multifaceted conservation strategies are needed to minimize negative biodiversity impacts of multiple environmental changes. We suggest that habitat protection, management and ecological restoration can mitigate combined impacts of land‐use change and climate change by providing environments that are suitable for existing populations and also enable species to shift their ranges.

Declining resilience of ecosystem functions under biodiversity loss

The composition of species communities is changing rapidly through drivers such as habitat loss and climate change, with potentially serious consequences for the resilience of ecosystem functions on which humans depend. To assess such changes in resilience, we analyse trends in the frequency of species in Great Britain that provide key ecosystem functions—specifically decomposition, carbon sequestration, pollination, pest control and cultural values. For 4,424 species over four decades, there have been significant net declines among animal species that provide pollination, pest control and cultural values. Groups providing decomposition and carbon sequestration remain relatively stable, as fewer species are in decline and these are offset by large numbers of new arrivals into Great Britain. While there is general concern about degradation of a wide range of ecosystem functions, our results suggest actions should focus on particular functions for which there is evidence of substantial erosion of their resilience.

Macroevolutionary patterns in the origin of mutualisms involving ants

Ants are a diverse and abundant insect group that form mutualistic associations with a number of different organisms from fungi to insects and plants. Here, we use a phylogenetic approach to identify ecological factors that explain macroevolutionary trends in the mutualism between ants and honeydew‐producing Homoptera. We also consider association between ant–Homoptera, ant–fungi and ant–plant mutualisms. Homoptera‐tending ants are more likely to be forest dwelling, polygynous, ecologically dominant and arboreal nesting with large colonies of 104–105 individuals. Mutualistic ants (including those that garden fungi and inhabit ant‐plants) are found in under half of the formicid subfamilies. At the genus level, however, we find a negative association between ant–Homoptera and ant–fungi mutualisms, whereas there is a positive association between ant–Homoptera and ant–plant mutualisms. We suggest that species can only specialize in multiple mutualisms simultaneously when there is no trade‐off in requirements from the different partners and no redundancy of rewards.

Oviposition responses to patch quality in the larch ladybird Aphidecta obliterata (Coleoptera: Coccinellidae): effects of aphid density, and con- and heterospecific tracks.

The effects and persistence of oviposition-deterring semiochemical cues from conspecific and heterospecific larval tracks on the oviposition rate of Aphidecta obliterata (Linnaeus) females were investigated. In addition, the effects of varying aphid prey density were considered and also whether any resulting response originated from differential nutritional status of females and/or due to aphid odour stimuli. The existence of oviposition responses to conspecific egg chemicals was also considered. Gravid A. obliterata females were deterred from oviposition by conspecific larval tracks and the effect was density dependent. Females actively avoided searching in these contaminated areas. Tracks induced a significant effect on oviposition for up to three days. Heterospecific tracks of the coccinellid Adalia bipunctata (Fabricius) or the chrysopid Chrysoperla carnea (Stephens) did not induce any oviposition response in A. obliterata females. Increasing aphid density induced increased oviposition rate in A. obliterata females. Nutritional status of females was an important factor in the relationship between aphid density and oviposition rate, but aphid associated cues (odours) were not. There was an inhibitory effect of extracts of conspecific egg-surface chemicals on oviposition by A. obliterata females. In the field, cannibalism, competition and limited food availability represent the major threats to egg and larval survival. Patch quality assessment mechanisms enable females to lay eggs at sites where offspring survival is maximized. Oviposition-deterring semiochemicals tend to promote more even distribution of predators over prey patches.

Forest management effects on carabid beetle communities in coniferous and broadleaved forests: implications for conservation

Abstract.  Carabid beetles (Carabidae, Coleoptera) were sampled by pitfall trapping to determine the effects of plantation forest management on beetle abundance, diversity and community composition. Five habitats were chosen for study to represent the different environments created by the clear‐fell and re‐plant forestry cycle: clear‐fell, new‐plant, mixed (conifer and broadleaved) and mature stage conifer plantation. The results from these sites were compared with semi‐natural deciduous woodland. Beetles were trapped for 6 weeks during June and July 2005. At each site, a range of environmental parameters were measured; soil pH, soil organic matter content, soil water content, percentage canopy cover, amount of dead wood, leaf‐litter depth, tree species present, tree diameter at breast height and percentage cover of ground vegetation. These were used to interpret differences in carabid abundance, diversity and community assemblage. Beetle abundance was highest in the deciduous habitat, but species diversity was not significantly different between any of the sites, except the clear‐fell habitat which was less diverse. Carabid community assemblages of forest specialist, forest generalist and open‐habitat species were investigated. Only the broadleaved deciduous woodland contained large populations of forest specialist species. These results suggest inclusion of purely broadleaved stands in the forest landscape is necessary to maximise diversity at the landscape scale and enhance the overall conservation potential of managed forest land. Within habitats the amount of dead wood, number of tree species present, percentage canopy cover and leaf‐litter depth were significant determinants of carabid abundance and diversity.

Avoidance responses of an aphidophagous ladybird, Adalia bipunctata, to aphid‐tending ants

Abstract 1. Insect predators often aggregrate to patches of high prey density and use prey chemicals as cues for oviposition. If prey have mutualistic guardians such as ants, however, then these patches may be less suitable for predators.

A decision framework for considering climate change adaptation in biodiversity conservation planning

1. General principles of climate change adaptation for biodiversity have been formulated, but do not help prioritize actions. This is inhibiting their integration into conservation planning. 2. We address this need with a decision framework that identifies and prioritizes actions to increase the adaptive capacity of species. The framework classifies species according to their current distribution and projected future climate space, as a basis for selecting appropriate decision trees. 3. Decisions rely primarily on expert opinion, with additional information from quantitative models, where data are available. The framework considers in-situ management, followed by interventions at the landscape scale and finally translocation or ex-situ conservation. 4. Synthesis and applications: From eight case studies, the key interventions identified for integrating climate change adaptation into conservation planning were local management and expansion of sites. We anticipate that, in combination with consideration of socio-economic and local factors, the decision framework will be a useful tool for conservation and natural resource managers to integrate adaptation measures into conservation plans.

Habitat associations of species show consistent but weak responses to climate

Different vegetation types can generate variation in microclimates at local scales, potentially buffering species from adverse climates. To determine if species could respond to such microclimates under climatic warming, we evaluated whether ectothermic species (butterflies) can exploit favourable microclimates and alter their use of different habitats in response to year-to-year variation in climate. In both relatively cold (Britain) and warm (Catalonia) regions of their geographical ranges, most species shifted into cooler, closed habitats (e.g. woodland) in hot years, and into warmer, open habitats (e.g. grassland) in cooler years. Additionally, three-quarters of species occurred in closed habitats more frequently in the warm region than in the cool region. Thus, species shift their local distributions and alter their habitat associations to exploit favourable microclimates, although the magnitude of the shift (approx. 1.3% of individuals from open to shade, per degree Celsius) is unlikely to buffer species from impacts of regional climate warming.

Ant semiochemicals limit apterous aphid dispersal

Some organisms can manipulate the nervous systems of others or alter their physiology in order to obtain benefit. Ants are known to limit alate aphid dispersal by physically removing wings and also through chemical manipulation of the alate developmental pathway. This results in reduced dispersal and higher local densities of aphids, which benefit ants in terms of increased honeydew and prey availability. Here, we show that the walking movement of mutualistic apterous aphids is also reduced by ant semiochemicals. Aphids walk slower and their dispersal from an unsuitable patch is hampered by ants. If aphid walking dispersal has evolved as a means of natural enemy escape, then ant chemicals may act as a signal indicating protection; hence, reduced dispersal could be adaptive for aphids. If, however, dispersal is primarily a means to reduce competition or to maintain persistent metapopulations, then manipulation by ants could be detrimental. Such manipulation strategies, common in host–parasite and predator–prey interactions, may be more common in mutualism than expected.