Garth N. Foster

EFFECT OF LAND DISTURBANCE AND STRESS ON SPECIES TRAITS OF GROUND BEETLE ASSEMBLAGES

In this paper we test whether the morphology and life traits of species (in our case ground beetles of the family Carabidae) can be related to the main underlying axes of environmental variability of their habitats. Sites were selected a priori to maximize two gradients: land use as a general measure of disturbance characterized by an index of land management, and habitat adversity or stress as characterized by elevation and vegetation structure. The underlying environmental axes and the relationships of the morphology and life traits of the species with them were investigated using RLQ analysis, a multivariate ordination method able to relate a species trait table to a site characteristics table by way of a species abundance table. The first environmental axis was highly statistically significant and explained most of the variability. It was strongly negatively related to the intensity of land management, and positively related to increasing elevation and a set of variables reflecting vegetation stress. Two predictions were tested and found to be valid in the studied system: in highly managed lowland sites species were smaller, and the frequency of macropterous species (with better dispersal abilities) was higher. Other traits also showed significant relationships with the main environmental axis: in the intensively managed lowland sites species had broader bodies, longer trochanters, and wider femora (characters associated with plant eaters), were paler in color, overwintered only as adults, bred in spring or autumn, and were active in summer. We conclude that the ground beetle assemblages of the studied sites respond in a similar way to the same underlying environmental factors. This allows the precise definition of functional groups, which can be used to characterize functional diversity and its relationships with changes in land management.

The Effect of Geographical Scale of Sampling on DNA Barcoding

Abstract Eight years after DNA barcoding was formally proposed on a large scale, CO1 sequences are rapidly accumulating from around the world. While studies to date have mostly targeted local or regional species assemblages, the recent launch of the global iBOL project (International Barcode of Life), highlights the need to understand the effects of geographical scale on Barcodings goals. Sampling has been central in the debate on DNA Barcoding, but the effect of the geographical scale of sampling has not yet been thoroughly and explicitly tested with empirical data. Here, we present a CO1 data set of aquatic predaceous diving beetles of the tribe Agabini, sampled throughout Europe, and use it to investigate how the geographic scale of sampling affects 1) the estimated intraspecific variation of species, 2) the genetic distance to the most closely related heterospecific, 3) the ratio of intraspecific and interspecific variation, 4) the frequency of taxonomically recognized species found to be monophyletic, and 5) query identification performance based on 6 different species assignment methods. Intraspecific variation was significantly correlated with the geographical scale of sampling (R-square = 0.7), and more than half of the species with 10 or more sampled individuals (N = 29) showed higher intraspecific variation than 1% sequence divergence. In contrast, the distance to the closest heterospecific showed a significant decrease with increasing geographical scale of sampling. The average genetic distance dropped from > 7% for samples within 1 km, to < 3.5% for samples up to > 6000 km apart. Over a third of the species were not monophyletic, and the proportion increased through locally, nationally, regionally, and continentally restricted subsets of the data. The success of identifying queries decreased with increasing spatial scale of sampling; liberal methods declined from 100% to around 90%, whereas strict methods dropped to below 50% at continental scales. The proportion of query identifications considered uncertain (more than one species < 1% distance from query) escalated from zero at local, to 50% at continental scale. Finally, by resampling the most widely sampled species we show that even if samples are collected to maximize the geographical coverage, up to 70 individuals are required to sample 95% of intraspecific variation. The results show that the geographical scale of sampling has a critical impact on the global application of DNA barcoding. Scale-effects result from the relative importance of different processes determining the composition of regional species assemblages (dispersal and ecological assembly) and global clades (demography, speciation, and extinction). The incorporation of geographical information, where available, will be required to obtain identification rates at global scales equivalent to those in regional barcoding studies. Our result hence provides an impetus for both smarter barcoding tools and sprouting national barcoding initiatives—smaller geographical scales deliver higher accuracy.

Relationships between agricultural management and ecological groups of ground beetles (Coleoptera: Carabidae) on Scottish farmland

The primary aim of this research was to classify ground beetle species, collected from farmland habitats in Scotland, into distinct groups based on their ecological traits. The objective classification of 68 species on this basis, using multivariate analyses, identified seven distinct ecological groups that were primarily determined by size, diel activity and diet (e.g. large Carabus spp., nocturnal plant feeders and species feeding on Collembola). The influence of agricultural land use and management intensity on these ecological groups was then investigated. The percentage of both Carabus spp. and individuals was greater on heather moorland and semi-natural grassland sites than in intensively managed arable or grassland sites. The percentage of Carabus spp. was also adversely affected by intensive agricultural management. A higher percentage of carabids feed specifically on Collembola in intensive grassland sites than in arable or semi-natural grassland sites suggesting that Collembola were more available in intensive grassland. This study introduces a non-taxonomic method of classifying carabids on the basis of their ecology. Such classification methods not only enable influences of agriculture to be detected across broad ecological groups rather than being reliant on the presence of a few key indicator species, but may also help in predicting how such changes to the community structure may influence ecosystem functioning.

Comparing the effects of farming practices on ground beetle (Coleoptera: Carabidae) and spider (Araneae) assemblages of Scottish farmland

Multivariate techniques were used to compare and contrast the effects of land cover and farming practice on ground beetle and spider assemblages of Scottish farmland. For both ground beetles and spiders, the ordination and fuzzy clustering of sites were related to land cover rather than geographical location or year of sampling. The same four types of land cover group were identified: that is, heather moorland, semi-natural grassland, intensive grassland and arable land. The robustness of these land cover groups was tested using previously unsampled sites and it was found that 79 and 86% of sites, for ground beetle and spider assemblages respectively, were allocated to the land cover group predicted from their actual land cover. Furthermore, procrustes rotational analysis found a strong relationship between ground beetle and spider assemblages in intensively managed sites, suggesting that the assemblage structure of one group could be used to predict that of the other. The observed relationship between spider and ground beetle assemblages does not necessarily indicate that both groups were responding to agricultural practices in the same way. Indeed, the highest number of beetle species occurred in intensively managed grassland and arable sites while the highest number of spider species occurred in semi-natural grassland and heather sites. When conducting ecological assessments, one might wish to collect information on a wide range of ecologically different taxa; however, financial constraints make this unfeasible. From the results it could be concluded that spiders should be chosen in preference to ground beetles when seeking to make predictions on how farming practices influence invertebrates. However, such a conclusion would be premature since not only were spiders more numerous in the traps, but they were also more time consuming to process. In addition, the strong relationship found between the spider and ground beetle assemblages further justifies carabids as a target group when monitoring the influence of farming practices on biodiversity.

Prediction of plant diversity response to land use change on Scottish agricultural land

Surveys of 87 sites within nine locations on Scottish agricultural land, during 1995–1997, recorded 335 species of vascular plants and 95 bryophyte species, within 31 recognisable plant communities. Multivariate analysis placed the vegetation into five main vegetation types, with differing plant species richness ( S: number of species per 100 m 2 ). These were upland grassland (mean S = 37); mesotrophic semi-improved grassland (mean S = 25); mire/heath vegetation (mean S = 22); intensive grassland (mean S = 12); and arable land and weed communities, including set-aside (mean S = 9). Management intensity was a good predictor (R 2 = 0.729) of vegetation type, with low intensity being typical of upland grassland, and high intensity typical of arable vegetation. The data were used to develop and test a set of minimal linear models of plant diversity response to land-use changes, operating at field scale, under the agro-geo-climatic conditions of mainland Scotland. The models utilised predictor variables drawn from a suite of functional vegetation attributes, environmental data, and management information. All-plant-species S was well predicted at quadrat level (i.e. within field, excluding margins) by three models with high R 2 values (0.82–0.93) utilising management variables such as crop-type, livestock density, time since last cultivation; vegetation state variables such as bryophyte cover, sward height, litter cover; and environmental variables such as soil P content. Bryophyte S was well predicted by four models with high R 2 values (0.83–0.92). Bryophyte percentage cover was the most important predictor variable in these models. Vascular plant species S was less well predicted than either all-plant-species or bryophytes-only models. The models can be used to assess the implications of land-use change scenarios, and to aid management decisions to help to maintain plant diversity within the Scottish agricultural landscape.

Modelling populations of Erigone atra and E. dentipalpis (Araneae: Linyphiidae) across an agricultural gradient in Scotland

Linyphiid spiders are important generalist predators of insects in agricultural habitats. Their ability to rapidly disperse and colonise disturbed habitats makes them important as a natural form of pest control, often present before other predatory groups arrive. This paper examines the distribution of Erigone atra and E. dentipalpis, which are amongst the commonest linyphiid species to be found on agricultural land in Scotland. The habitat preferences of these species were assessed using abundance and proportion data from 71 independent sites sampled using pitfall traps over 2 years and a selection of repeat first-year sites sampled during the second year, incorporating a range of land-uses from extensive moorland, through grasslands to intensive arable fields. E. atra dominated in autumn sown crops, and E. dentipalpis dominated at the other end of the agricultural management spectrum in low-intensity grasslands. Both species were considered absent from upland and moorland habitats. Linear regression modelling was used to create a model which best estimated the variance in proportions of E. atra in the catch across the sites using a selection of vegetation, soil, management and landscape variables. This model was based on data from 58 sites where Erigone species were abundant and explained 66% of the variation in E. atra. The variables included were increasing vegetation biomass above 50 mm and increasing levels of mixed grazing (both positive), and a combination of increasing plant species richness and vegetation stem density (negative). The efficiency of the model was examined using data from 13 sites which were sampled in the subsequent year to assess the effects of no changes and changes in land-use on the proportions of the two species. Only two sites were considered inaccurate (more than 20% different from the model), suggesting a relatively high level of accuracy. Interaction between the two species was tested for and not found to explain the differences in proportion observed. Comparisons with other studies were carried out, showing similar trends in proportions and in some of the variables identified as important. The influence of specific variables on each species is described in light of possible allometric-type effects, and the importance of these species for conservation and pest control in agriculture is discussed.

Using Collembola to assess the risks of applying metal-rich sewage sludge to agricultural land in western Scotland

The recent United Kingdom ban on the disposal of sewage sludge at sea has led to the prediction that land application of sludge will become more widespread. The positive aspect of recycling nutrients may, however, be offset by the risk of contamination by heavy metals that are frequently present in sludge. The environmental impact of applying metal-rich sewage sludge to agricultural land was, therefore, assessed using Collembola. A combination of pitfall trapping and suction sampling was used to monitor epigeal/hemiedaphic Collembola on a small plot field trial in the west of Scotland. Four sludge treatments were investigated: cadmium-rich sludge, zinc-rich sludge, uncontaminated sludge and a no-sludge control. It was found that the abundance of Lepidocyrtus cyaneus Tullberg and Isotoma viridis Bourlet was significantly lower in plots receiving cadmium-rich sludge than those receiving uncontaminated sludge. Isotoma anglicana Lubbock was not influenced by the presence of metals in sludge and Isotomurus palustris (Muller) was actually favoured by the application of metal-rich sludge. Other aspects of collembolan ecology, and the efficiency of the two sampling methods, are also discussed.

The Impact of Different Agricultural Land-uses on Epigeal Spider Diversity in Scotland

Detailed knowledge of the biodiversity of spider communities on agricultural land is important both in terms of enhancing pest control and understanding the driving forces influencing nature conservation value. Pitfall traps were used to assess spider species diversity at 71 Scottish agricultural sites between May and September during 1996 and 1997. Land-use varied from intensive arable fields, grasslands and extensive heather (Calluna vulgaris) moorland. Spider species richness (S) was found to decrease significantly as farm management intensity increased. Several linear regression models based on the 1996 data (50 sites) and a selection of plant, soil and landscape variables explained up to 88% of the variation in species richness. Four of these models were used to estimate 1997 species richness (36 sites: 15 repeat and 21 new) and up to 58% of sites were correctly predicted to within ± four species of the actual number caught. As only 60% of the repeat 1997 sites had values of S within four units of their 1996 score, this suggested a relatively high level of model accuracy. Model accuracy increased to 64% when all four models were used for each site, suggesting the individual models should be targeted at specific land-use types. We discuss the relevance of these models for predicting the consequences of changes in agricultural land-use for spider diversity.

Factors affecting the size of leatherjacket (Diptera:Tipulidae) populations in pastures in the west of Scotland

Abstract Leatherjacket ( Tipula spp.) populations were surveyed in 77 pastures in the west of Scotland in the winter of 1991/92 and again in 1992/93. General soil characteristics and a number of other environmental variables were also recorded for each pasture in 1992/93. Leatherjacket numbers and associated environmental variables were analysed using Generalised Linear Interactive Modelling (GLIM) to produce a generalised linear model relating 1992/93 leatherjacket numbers to field characteristics over 68 of the pastures surveyed. The model was constructed using four categorical variables (aspect, silage use, tendency to waterlogging, organic fertiliser use) and three continuous variables (1991 /92 leatherjacket numbers, sward height at time of sampling, distance from the Atlantic). All seven variables had a significant effect in the model and together accounted for 50% of the total variability in 1992/93 leatherjacket numbers. Possible modes of action are suggested for each of these variables. The predictive efficiency of the model was tested using the data from nine pastures excluded from the original data set. The results of the analyses confirmed the positive effects of waterlogging on leatherjacket numbers, but also indicated the importance of other previously undocumented factors such as aspect and the influence of prevailing winds. In addition, none of the standard soil characteristics recorded (such as pH, bulk density or percentage loss on ignition) was found to have any effect on leatherjacket numbers. The relevance of these findings to future research on leatherjackets in pastures is discussed.

A North African–European transition fauna: water beetles (Coleoptera) from the Ebro delta and other Mediterranean coastal wetlands in the Iberian peninsula

The aquatic Coleoptera of some major wetlands in the Mediterranean coast of Spain were surveyed, with the aim of assessing their conservation value and the status of some coastal species in the Iberian Peninsula. 2. Classification of 59 species from 13 sites between the deltas of the rivers Ebro and Llobregat using TWINSPAN suggested that water origin and amount and structure of vegetation were major factors influencing the composition of the coastal water beetle communities. 3. The Ebro delta is considered to be a key biogeographical area, being the limit of the distribution of a number of north African and European species. Coastal sites in the Iberian peninsula sustain the only known populations in continental Europe of at least three Ethiopian species, although two of them may have become extinct. Some European species known to have reached the north of Catalonia were also considered to be possibly extinct in the Iberian peninsula owing to the destruction of their habitats. Three circum-Mediterranean coastal species were recorded for the first time in the Iberian peninsula, one of them in a genus new to its fauna. 4. Despite the scarcity of true endemics-the result of the recent geological origin and the temporal dynamics of coastal systems-some species were exclusive to temporary habitats, and had very restricted distributions. 5. Although most of the areas studied have some form of protection, this is mainly focused in large, permanent lagoons and on the vertebrate fauna. The need to include marginal areas and invertebrates in the protection plans for the area is stressed.