Duncan McCollin

Finding NEMO: nestedness engendered by mutualistic organization in anemonefish and their hosts

The interaction structure of mutualistic relationships, in terms of relative specialization of the partners, is important to understanding their ecology and evolution. Analyses of the mutualistic interaction between anemonefish and their host sea anemones show that the relationship is highly nested in structure, generalist species interacting with one another and specialist species interacting mainly with generalists. This supports the hypothesis that the configuration of mutualistic interactions will tend towards nestedness. In this case, the structure of the interaction is at a much larger scale than previously hypothesized, across more than 180° of longitude and some 60° of latitude, probably owing to the pelagic dispersal capabilities of these species in a marine environment. Additionally, we found weak support for the hypothesis that geographically widespread species should be more generalized in their interactions than species with small ranges. This study extends understanding of the structure of mutualistic relationships into previously unexplored taxonomic and physical realms, and suggests how nestedness analysis can be applied to the conservation of obligate species interactions.

The effect of hedgerow loss on microclimate in the Mediterranean region: an investigation in Central Spain

In Central Spain hedgerows are an important component of the landscape although many have been lost due to landscape planning and reallotment programmes. Loss of hedgerows can produce changes in environmental conditions that can be especially critical in summer, corresponding with the dry period in Mediterranean ecosystems. In order to show the effects of hedgerow removal on summer Mediterranean environmental conditions in rural landscapes, this paper describes a comparison of some key environmental conditions between areas where hedgerows are still present, compared to areas where they have been removed. Through a two-way ANOVA, it was found that temperatures in the hedgerows were significantly different from those in the fields, whilst air temperatures beneath the hedgerows were lower, and steadier, than those of surrounding areas. When temperatures of the fields were compared to those sites where hedgerows had been removed, significant differences in temperatures were detected belowground and sometimes at soil surface level but not at higher levels. The levels of soil water content and organic carbon were higher where hedgerows were still in place. These differences indicate potentially negative environmental impacts due to hedgerow removal. The implications of hedgerow conservation for environmental protection and for cropland productivity are discussed.

The conservation value of restored landfill sites in the East Midlands, UK for supporting bird communities

There has been a rapid decline of grassland bird species in the UK over the last four decades. In order to stem declines in biodiversity such as this, mitigation in the form of newly created habitat and restoration of degraded habitats is advocated in the UK biodiversity action plan. One potential restored habitat that could support a number of bird species is re-created grassland on restored landfill sites. However, this potential largely remains unexplored. In this study, birds were counted using point sampling on nine restored landfill sites in the East Midlands region of the UK during 2007 and 2008. The effects of restoration were investigated by examining bird species composition, richness, and abundance in relation to habitat and landscape structure on the landfill sites in comparison to paired reference sites of existing wildlife value. Twelve bird species were found in total and species richness and abundance on restored landfill sites was found to be higher than that of reference sites. Restored landfill sites support both common grassland bird species and also UK Red List bird species such as skylark Alauda arvensis, grey partridge Perdix perdix, lapwing Vanellus vanellus, tree sparrow, Passer montanus, and starling Sturnus vulgaris. Size of the site, percentage of bare soil and amount of adjacent hedgerow were found to be the most influential habitat quality factors for the distribution of most bird species. Presence of open habitat and crop land in the surrounding landscape were also found to have an effect on bird species composition. Management of restored landfill sites should be targeted towards UK Red List bird species since such sites could potentially play a significant role in biodiversity action planning.

Do British birds conform to Bergmann's and Allen's rules? An analysis of body size variation with latitude for four species

Capsule An analysis of body mass and wing length for four bird species shows trends broadly in line with predictions from Bergmanns and Allens rules but with species- and sex-specific trends in terms of body size variation with latitude in Britain. Aims To analyse body size characteristics for bird species with latitude in Britain and to test Bergmann’s and Allen’s rules (over a range of c. 740 km). Methods Body mass and wing length for four bird species (Blackbird Turdus merula, House Sparrow Passer domesticus, Robin Erithacus rubecula, and Song Thrush Turdus philomelos) were analysed using principal components regression analysis to investigate trends with latitude, longitude, or by sex and Julian day. Results Evidence was found for latitudinal gradients in body mass for male Blackbird, female House Sparrow (both increasing in size northwards), and female Robin (decreasing in size northwards) and in wing length for female Robin and male Song Thrush (decreasing and increasing northwards, respectively). Conclusion Trends were broadly in line with predictions from Bergmanns and Allens rules except for Robin which had trends opposite to those expected. Differences in trends between sexes suggest a role for an interplay between natural and sexual selection with latitude that deserves further consideration.

Landscape metrics as functional traits in plants: perspectives from a glacier foreland

Spatial patterns of vegetation arise from an interplay of functional traits, environmental characteristics and chance. The retreat of glaciers offers exposed substrates which are colonised by plants forming distinct patchy patterns. The aim of this study was to unravel whether patch-level landscape metrics of plants can be treated as functional traits. We sampled 46 plots, each 1 m × 1 m, distributed along a restricted range of terrain age and topsoil texture on the foreland of the Nardis glacier, located in the South-Eastern Alps, Italy. Nine quantitative functional traits were selected for 16 of the plant species present, and seven landscape metrics were measured to describe the spatial arrangement of the plant species’ patches on the study plots, at a resolution of 1 cm × 1 cm. We studied the relationships among plant communities, landscape metrics, terrain age and topsoil texture. RLQ-analysis was used to examine trait-spatial configuration relationships. To assess the effect of terrain age and topsoil texture variation on trait performance, we applied a partial-RLQ analysis approach. Finally, we used the fourth-corner statistic to quantify and test relationships between traits, landscape metrics and RLQ axes. Floristically-defined relevé clusters differed significantly with regard to several landscape metrics. Diversity in patch types and size increased and patch size decreased with increasing canopy height, leaf size and weight. Moreover, more compact patch shapes were correlated with an increased capacity for the conservation of nutrients in leaves. Neither plant species composition nor any of the landscape metrics were found to differ amongst the three classes of terrain age or topsoil texture. We conclude that patch-level landscape metrics of plants can be treated as species-specific functional traits. We recommend that existing databases of functional traits should incorporate these type of data.

Effect of soil conditions and landscape factors on macro-snail communities in newly created grasslands of restored landfill sites in the UK

Though restored landfill sites provide habitat for a number of taxa, their potential for land snail remains unexplored. In this study, large-sized land snails (> 5 mm) were surveyed using transect sampling on nine restored landfill sites and nine corresponding nature sites in the East Midlands region of the UK during 2008. The effect of restoration was investigated by examining land snail species composition, richness, and diversity (Shannon Weiner index) in relation to habitat and landscape structure. Thirteen macro-snail species were found in total and rarefied species richness and diversity on restored landfill sites was not found to be statistically different to that of reference sites. One third of the snail species, comprising 30% of total abundance, found in the restored landfill sites were non-native species introduced to the UK. Soil electrical conductivity was the strongest predictor for richness and diversity of land snails. Road density was found to have a positive influence on snail species diversity. Given the high percentage of introduced species detected further research is needed in terms of the management implications of restored landfill sites and the dynamics of native versus non-native species.

Pushing back the baseline: a novel approach to detect long-term changes in terrestrial faunal abundance using historical qualitative descriptions

Abstract Studies that examine changes in the populations of flora and fauna often do so against a baseline of relatively recent distribution data. It is much rarer to see evaluations of population change over the longer–term in order to extend the baseline back in time. Here, we use two methods (regression analysis and line of equality) to identify long-term differences in abundance derived from qualitative descriptions, and we test the efficacy of this approach by comparison with contemporary data. We take descriptions of bird population abundance in Cambridgeshire, UK, from the first half of the 19th century and compare these with more recent estimates by converting qualitative descriptions to an ordinal scale. We show, first, that the ordinal scale of abundance corresponds well to quantitative estimates of density and range size based on current data, and, second, that the two methods of comparison revealed both increases and declines in species, some of which were consistent using both approaches but others showed differing responses. We also show that the regional rates of extinction (extirpation) for birds are twice as high as equivalent rates for plants. These data extend analyses of avifaunal change back to a baseline 160-190 years before present, thus bringing a novel perspective on long-term change in populations and categories of conservation concern (e.g., Amber- or Red-lists) based on recent data. Changes in status are discussed in relation to various factors, although perhaps the most pervasive were of anthropogenic origin.

Abundance estimates for landbirds and seabirds extracted and compiled from annual reports of the Skokholm bird observatory

Long-term ecological data are essential for conservation and to monitor and evaluate the effects of environmental change. Bird populations have been routinely assessed on islands off the British coast for many years and here long term data for one such island, Skokholm, is evaluated for robustness in the light of some 20 changes in observers (wardens) on the island over nearly eight decades. It was found that the dataset was robust when compared to bootstrap data with no species showing significant changes in abundance in years when wardens changed. It is concluded that the breeding bird populations on Skokholm and other British offshore islands are an important scientific resource and that protocols should be enacted to ensure the archiving of records, the continuance of data collection using standardised protocols into the future, and the recognition of such long-term data for science in terms of an appropriate conservation designation.