Effects of disturbance on the biodiversity and abundance of isopods in temperate grasslands

Connell's ‘intermediate disturbance hypothesis’ was tested using a relatively simple, species poor isopod community in grass heaths and in a coastal sand dune grassland. Variation in diversity resulted from disturbance both to the soil profile and sward structure due to grazing. Predictions from a spatial survey were tested using a 20 years time series. These changes were related to changes in rabbit activity, anthropogenic soil disturbance and on one site, deposition of blown sand. Changes in the soil profile resulted in diversity initially increasing due to decreases in the density of the commonest species, leading to an increase in equitability. Prolonged disturbance to the soil profile both due to sand blowing onto one site and rotavating on another, lead to a reduction in diversity due to one of the species being eliminated. The isopod community was most diverse when least disturbed by grazing, of intermediate diversity under intermediate grazing intensity and least diverse when most heavily grazed. In these simple communities, differences in diversity were mostly determined by differences in equitability rather than in species richness. We conclude that maximising heterogeneity of sward structure could have advantages for the conservation of both invertebrate biodiversity and vertebrates that feed on them.     

Diversity erosion beyond the species level: Dramatic loss of functional diversity after selective logging in two tropical amphibian communities

Assessing the effects of logging on different aspects of biodiversity and general ecosystem properties is of prime importance if the few remaining areas of intact tropical forest are to be efficiently protected. Commonly used measures of biodiversity may only inadequately reflect actual disturbance after logging and studies restricted to only one specific eco-region do not allow for generalizations of results. We hence measured the impact of selective logging on different levels of diversity of two tropical anuran communities in two geographically distinct eco-regions. Species-diversity patterns were incoherent both, within and between studies. In West Africa, species richness did not differ between primary and exploited forest sites, whereas South American anuran communities exhibited higher species richness in primary sites. Yet, in both eco-regions, functional diversity (FD) was higher in primary forest communities. Absolute values of FD were higher in South American anuran communities, despite higher species richness in West African communities. FD was higher in older recovery, as compared to younger recovery states, even though species-diversity did not differ significantly. Three major conclusions can be drawn from our results. 1. Scale matters: it is important to monitor different levels of biodiversity in order to reveal its actual loss after anthropogenic disturbance. 2. Time matters: the disturbance history of a site is important in order to detect patterns that otherwise remain unnoticed. 3. Geographic history matters at the local scale: whereas general patterns at higher diversity levels were identical in both eco-regions, species richness, species diversity and turnover patterns differed.     

Lizards and landscapes: integrating field surveys and interviews to assess the impact of human disturbance on lizard assemblages and selected reptiles in a savanna in South Africa

Habitat degradation through over-grazing and wood collection is especially prevalent in developing countries such as South Africa. As human populations expand and the demand for land increases, the traditional idiom of setting aside protected areas for conservation is insufficient and assessment and protection of diversity outside these areas is needed. We assessed the impact of land use on lizard assemblages in communal rangelands in South Africa by comparing abundance, species richness and species diversity between degraded communal lands with a protected area. We first quantified vegetation differences between the study areas and found marked differences. Communal lands had significantly fewer large trees and less ground cover. Contrary to prediction, we found no evidence that any species of lizard was negatively affected by habitat disturbance. Some species were more common in communal lands, and species richness and diversity were also higher using certain sampling techniques. Terrestrial diversity was likely enhanced due to the preference of many terrestrial lizards for open, sparsely grassed areas. We discuss other reasons for increased diversity such as the intermediate disturbance hypothesis and/or reduced numbers of predators and competitors. We also conducted surveys of households and traditional healers to investigate the relationship between human uses of reptiles and abundance. The predominant users of reptiles were traditional healers. The most commonly used species were not encountered in our field surveys, and respondents indicated that they appeared to be declining. Our results emphasise the importance of integrating local knowledge into biodiversity assessment and conservation planning. Although we did not identify a negative impact of disturbance on lizard communities, community structure was different and this likely influenced ecosystem integrity and function in some way.     

Biodiversity and ecosystem function of tropical forest dung beetles under contrasting logging regimes

A key challenge for tropical conservation biologists is to assess how forest management practices affect biodiversity and associated ecosystem functions. Dung beetles (Scarabaeidae: Scarabaeinae) provide an ideal focal guild for such studies. We compared dung beetle assemblages and experimentally assessed rates of dung removal and seed burial in undisturbed forest, low-intensity selectively logged forest under sustainable forest management, and high-intensity logged forest, not under sustainable management in Malaysian Borneo. In total, 7923 individuals from 39 species of dung beetle were collected. There were no significant differences in abundance, biomass or diversity across sites. Species richness was significantly lower in the high-intensity logged sites. Beta diversity was low: of 35 species recorded in undisturbed forest sites, 32 were also captured in low-intensity sites and 29 in high-intensity sites. The environmental and vegetation variables measured had little influence on species composition. An average of 63–99% of dung was removed over 24 h. Mean dung and seed removal were significantly lower in the high-intensity logged sites. Dung removal rates were significantly and positively correlated with dung beetle species richness, but not with dung beetle biomass or abundance. However, the biomass of large-bodied, nocturnal dung beetles was positively correlated with dung removal. In contrast to previous studies, dung beetle biomass and abundance were not correlated with species richness, indicative of density compensation. Overall, dung beetle communities and associated ecosystem functions were robust to low-intensity but not high-intensity selective logging. These differences may be related to changes in the abundance and biomass of particular dung beetle species or guilds rather than community-wide measures of abundance and biomass, highlighting the need to move beyond simplistic biodiversity-ecosystem functioning correlations to understand the functional consequences of habitat modification in high-diversity ecosystems.     

The importance of fine-scale savanna heterogeneity for reptiles and small mammals

Tropical savannas are an important reservoir of global biodiversity. Australia’s extensive savannas, although still largely intact, are experiencing substantial declines in terrestrial biodiversity due to a variety of interrelated effects of altered fire regimes, grazing and increases in invasive species. These disturbance processes are spatially variable, combine to increase landscape to local-scale landscape heterogeneity, but rarely result in well-defined patch boundaries. We quantified the importance of this heterogeneity for native reptile and small mammal species in a tropical savanna landscape of Queensland, Australia. We used high resolution remote sensing imagery (IKONOS) to map habitat pattern at a 4 m spatial resolution and at variable extents. We found that landscapes dominated by grass or bare ground had low reptile and small mammal diversity, while landscapes with a heterogeneous mix of grass, bare ground and trees had high species diversity and relative abundance of most species. Landscape heterogeneity may increase reptile and small mammal species richness by: (i) increasing the variety and abundance of foraging resources such as seeds and invertebrates; (ii) providing cover from predators and high summer temperatures; and (iii) increasing functional connectivity and dispersal success. The importance of these resources and processes varies among individual species and at different spatial scales, reiterating the need to consider habitat requirements of multiple species in landscape management and conservation planning.     

Changes of isopod assemblages along an urban–suburban–rural gradient in Hungary

Responses of isopod assemblages to urbanisation were studied along an urban–suburban–rural gradient representing a decrease in the intensity of human disturbance. Pitfall trapping collected six species (Armadillidium vulgare, Porcellio scaber, Porcellium collicola, Trachelipus ratzeburgii, Cylisticus convexus, and Trachelipus rathkii). A. vulgare occurred abundantly in all sites reflecting the broad tolerance and invasive nature of this species. Indicator species analysis demonstrated that P. scaber and T. rathkii were significant quantitative character species for the urban site, while T. ratzeburgii was characteristic for the natural habitats (suburban and rural sites). CANOCO revealed that ground and air temperature show positive correlation with the distribution of P. scaber and T. rathkii, and negative correlation with T. ratzeburgii. Nested ANOVA on trap level showed that there were no significant differences between the number of isopod species and individuals, and the diversity of isopod assemblages in the three studied areas. Significant differences were observed at site level. The results did not support the hypothesis that diversity should decrease in response to habitat disturbance. They also contradicted the intermediate disturbance hypothesis; species richness was not the highest in the moderately disturbed suburban area. Multivariate methods detected that the isopod assemblages of the rural and suburban areas were relatively similar, while that of the urban area was relatively separated.     

Selecting terrestrial arthropods as indicators of small-scale disturbance: A first approach in the Brazilian Atlantic Forest

The growing pressure placed by human development on natural resources creates a need for quick and precise answers about the state of conservation of different areas. Thus, identifying and making use of ecological indicators becomes an essential task in the conservation of tropical systems. Here we assess the effects of small-scale disturbance on terrestrial arthropods and select groups that could be used as ecological indicators in the Brazilian Atlantic Forest. Arthropods were sampled within a continuous forest in the Serra do Mar State Park, southeastern Brazil, both in disturbed and undisturbed areas of the reserve. The abundance of exotic species was higher in the disturbed site, and this pattern seems to be an adequate indicator of anthropogenic disturbance. Species richness of Araneae, Carabidae, Scarabaeidae, Staphylinidae, and epigaeic Coleoptera (pooled) was higher in the undisturbed site, while that of fruit-feeding butterflies was higher in the disturbed site. Species richness was not significantly correlated between any pair of taxa. In contrast, species composition was significantly correlated among most groups, and clearly discriminates the disturbed from the undisturbed site. Moreover, fruit-feeding butterflies and epigaeic Coleoptera composition discriminated disturbed and undisturbed sites even when species were grouped into higher taxonomic levels, which may be a way of overcoming the difficulty of identifying arthropod species from poorly studied, species-rich ecosystems. Potential applications for these indicators include the choice and evaluation of sites for the establishment of natural reserves, elaboration of management plans, and the assessment of ecological impacts due to human activities, either for the purposes of licensing or legal compensation.     

Global food security,biodiversity conservation and the future of agricultural intensification

There is vigorous debate about the potential for reforestation to offset losses in biodiversity associated with tropical deforestation, but a scarcity of good data. We quantified developmental trajectories following active restoration (replanting) of deforested pasture land to tropical Australian rainforest, using 20 different bird community indicators within chronosequences of multiple sites. Bird species composition in restored sites (1–24 years old) was intermediate between that of reference sites in pasture and primary rainforest. Total species richness was much less sensitive to land cover change than composition indicators, because of contrasting species-specific response patterns. For example, open-country (grassland/wetland) bird species declined in richness and abundance with increasing site age, while rainforest-dependent species increased. Results from two different landscapes (uplands and lowlands) were remarkably consistent, despite differing bird assemblages. After 10 years, restored sites averaged about half the number of rainforest-dependent bird species typical of rainforest. Mean values at around 20 years overlapped with the “poorest” rainforest reference sites, but projections suggest that >150 years are required to reach mean rainforest levels, and high variability among sites means that many were not on track towards ever achieving a rainforest-like bird community. Regional rainforest endemics were half as likely to occupy older revegetated sites as non-endemic rainforest-dependent species. Between-site variability and slow colonisation by regional endemics strongly constrain the potential of rainforest restoration to offset the biodiversity impacts of tropical deforestation. The results also mean that ongoing monitoring of biodiversity is an essential part of restoration management.     

Oniscidea diversity across three environments in an altitudinal gradient in northeastern Rio Grande do Sul, Brazil

The diversity of Oniscidea across a 1000-m altitudinal gradient comprising three distinct environments—the coastal plain, the highland slopes, and the highlands—was described and analysed. We employed 1 h-long exploratory manual sampling at 41 sites. Fourteen species were identified, of 818 individuals collected. Sampling-effort curves stabilised for all three environments; analytical estimates of species richness did not exceed the observed value. Abundance did not vary significantly among environments, and local species richness differed only marginally. However, the Shannon diversity index for local sites indicated highland slopes to be significantly more diverse than the coastal region; the same was true for bootstrap estimates at the regional level. Two species appeared in all three environments, comprising 72.7% of the abundance. The coastal region and highlands had one exclusive species each, and the highland slopes had three. The first two environments are more similar to each other than to the slopes, although they are not contiguous. The altitudinal gradient of diversity was hump-shaped, because the highland slopes were most diverse. The reasons for this pattern are not biogeographical; that is, the highland slopes are not a contact zone between the highlands and the coast. A complete explanation depends upon better understanding of the effect of soil type and terrain slope on the diversity of terrestrial isopods.     

Invasion success of exotic plants in natural ecosystems: the role of disturbance, plant attributes and freedom from herbivores

Invasion of natural ecosystems by exotic species is a major threat to biodiversity globally. We assessed two alternative (but not exclusive) hypotheses to explain the success of exotic species in urban bushland on low fertility sandstone-derived soils in Sydney, Australia. These were that success of exotic species is promoted by: (1) plant attributes in particular disturbance types; and (2) freedom from herbivores. We tested these at sites subject to different types of disturbance: nutrient and water enrichment (below stormwater outlets), nutrient enrichment (riparian zones of creeks with an urban catchment) and physical disturbance (tracks), and control sites. At each site we estimated percentage cover of all species and surveyed leaves for damage by herbivores. Species were classified as native, non-invasive exotic or invasive exotic. We found that sites without any disturbance did not support exotic plants. Physically disturbed sites on low fertility soils supported only one exotic species, suggesting that nutrient enrichment is a critical prerequisite for exotic species invasion on low fertility soils. Exotic species cover was highest and native species richness most reduced in areas of highest nutrient enrichment. Both invasive exotic and non-invasive exotic species had significantly lower levels of leaf herbivory than native species, implying that release from pests alone cannot account for the success of invasive species. Specific leaf area of invasive exotic species was consistently higher than specific leaf area of non-invasive exotic and native species, regardless of disturbance type. In physically disturbed sites of higher soil fertility, exotic species were small herbs and grasses of long flowering duration and with small unassisted or wind-dispersed seeds. In sites subject to nutrient-enrichment, exotic species were more likely to be climbers, able to propagate vegetatively, and with seeds dispersed by vertebrates. Thus different plant attributes contribute to exotic species success under different disturbance types. The clearest consistent difference we found between invasive exotic and non-invasive exotic species was in specific leaf area, suggesting that large specific leaf area facilitates invasiveness.     

Coarse woody debris,soil properties and snails (Mollusca: Gastropoda) in European primeval forests of different environmental conditions

We studied the snail fauna of four primeval forests of Central Slovakia and focused on the influence of forest type and coarse woody debris (CWD) on species assemblages. We found a total of 3281 individuals from 39 species. Species assemblages differed between the forests. In SW-facing oak forests, CWD enhanced the proportion of forest species such as the wood-grazing Cochlodina laminata and decreased the proportion of euryecious species like the litter-dwelling Punctum pygmaeum. In NE-facing beech forests, hygrophilous species such as Carychium tridentatum dominated the assemblages. This litter-dwelling snail was especially abundant close to CWD. The NE-facing beech forests harbored more species and individuals than the SW-facing oak forests did. CWD enhanced snail abundance, species richness and biodiversity, irrespective of forest type. We found positive correlations for abundance and species richness to the amount of leaf litter, C_org, N_tot, Ca²⁺, and K⁺; snail abundance was also positively correlated to soil pH. All these soil chemical factors were higher close to CWD than distant from CWD.     

A meta-analysis of fauna and flora species richness and abundance in plantations and pasture lands

We conducted a systematic global review of differences between timber plantations and pasture lands in terms of animal and plant species richness and abundance, and assessed the results using meta-analysis techniques. Our principal aim was to test the hypothesis that plantations contain higher species richness or abundance than pasture. Of the 1967 studies of potential relevance, 66 provided biological monitoring information and 36 met the requirements for meta-analyses. Sufficient data were available for meta-analyses to be conducted comparing the species richness and abundance of plantations and pasture lands for five taxonomic groups: plants, invertebrates, reptiles/amphibians, mammals, and birds. Within each taxon there was considerable variation in the difference between species richness and abundance between plantations and pasture lands. Birds and reptile/amphibians exhibited significantly higher species richness, and mammals exhibited significantly higher abundance, in plantations than in pasture lands which lacked remnant vegetation. Reptile/amphibian species richness was significantly higher in plantations in general. No significant differences in species richness were found for mammals, plants, or invertebrates, and no significant differences in abundance were found for birds, reptiles/amphibians, invertebrates, or plants. It is only within the presence of taxonomic caveats (i.e. reptiles/amphibians), or specific landscape features (i.e. absence of remnant vegetation within pasture), that it can be concluded that plantations support higher species richness or abundance than pasture land. We emphasize that caution is warranted when making general statements about the inherent biodiversity value of diverse and broadly-defined land-uses.     

Altitudinal terrestrial isopod diversity

We have assessed the diversity of terrestrial isopods across an elevational and habitat gradient on Mt. Panachaiko (NW Peloponnisos, Greece). Previous knowledge on the biodiversity of this mountain was restricted to very few records of individual species, and no systematic sampling had ever been applied for any animal taxon. We selected the most representative habitat types within an altitudinal range from 750 to 1700 m a.s.l., where we applied qualitative and quantitative monthly sampling using hand collecting and pitfall traps for 6 months during the snow-free period (June–November). We sampled three sites with maquis vegetation, one site with fir forest, one with sparse hawthorn vegetation and two at a highland meadow, and we compared the distribution and abundance patterns of isopod species among these habitat types. Overall, 13 isopod species were found, seven of which were also captured in pitfall traps. One species, Armadillidium lobocurvum, was extremely abundant at the most elevated sites, resulting in very uneven patterns of abundance. The habitat types with higher diversity of isopod species were the sparse hawthorns and the open maquis, and the richest month was July. We also discuss the phenology of the most abundant species at the highland meadows.     

Response of a desert lizard community to habitat degradation: Do ideas about habitat specialists/generalists hold?

We report the impact of human-induced desertification on the species richness, abundance, and composition of sand dune flora and herpetofauna of North Sinai, Egypt. Our hypothesis was that degraded habitats would have reduced vegetation complexity, richness, and abundance, and consequently lower reptile species richness and abundance. We also hypothesized that desert lizards would not follow the typical generalist/specialist responses to habitat degradation found in other biomes. Instead, we predicted that because vegetation loss intensifies the environmental extremity of deserts, those species specialized for open and sandy environments would be more likely to persist in desertified habitats than would desert generalists. Our results showed that areas protected from vegetation loss did not have significantly higher vegetation richness or abundance except for only a few species. However, protected sites did have significantly higher percent vegetation cover and height. Habitat protection clearly had strong effects on the reptile community as species richness and abundances were significantly higher in protected sites. The composition of the reptile community between protected and unprotected sites differed significantly. Contrary to past studies in other environments, desert generalist species were not able to persist in degraded sites and were only found in protected sites. Specialist species were ubiquitous in that they occurred in both areas protected and unprotected from vegetation loss. We propose that the effects of disturbance on species composition (specialists or generalists) depends on whether the disturbance exacerbates or reduces environmental harshness and the conditions that favor specialization. In extreme environments, specialist and generalist responses to habitat degradation are opposite to that of more productive environments.     

Geographic determinants of oribatid mite communities structure and diversity across Europe: a longitudinal perspective

The aim of the study reported here was to assess the impact of climate continentality across Europe on the structure and diversity of oribatid communities. Five sites were chosen along a West–East transect from The Netherlands to the Moscow region in Russia in the zone of deciduous forest. Our results suggest that at the chosen scale climate has a moderate impact on abundance and biomass of oribatid communities. However there is a clear impact of continentality on the functional structure and diversity of oribatid populations expressed as the increase of soil-dwelling species abundance towards the East and the decrease of litter-dwellers. There are also strong indications of a gradual faunistic shift along the transect. Soil type plays a modulating role in oribatid communities composition and species richness.     

Management regimes for a plant invader differentially impact resident communities

Management of plant invaders causes disturbance and the compounding effects of both invasion and management on biodiversity merit rigorous assessment. We explored the impacts of both plant invasion and management disturbance in coastal dune communities of Australia invaded by the introduced shrub bitou bush (Chrysanthemoides monilifera ssp. rotundata). We compared the effects of intensive, manually based invader control with those of extensive control (mainly herbicide spraying from aircraft) across fore dune communities. We examined one management regime, which was typically intensive, in hind dune communities. Our main aim was to test the prediction that intensive methods would achieve better biodiversity outcomes than extensive approaches in fore dune communities. We found that extensive management created native species complements that diverged from non-invaded sites while intensive management approached non-invaded site conditions. However, intensively managed sites were also richer in other exotic species than extensively managed sites. Thus, while biodiversity outcomes were better under intensive management, the risk profile of such sites was increased by the greater array of exotics that could potentially replace the original invader. The positive effects of management evident on some fore dunes were not found in hind dunes, where managed sites had the highest exotic species richness and similar bitou bush seedling abundance as both non-invaded and bitou-invaded sites. Hind dune managed sites were also compositionally distinct from non-invaded sites. Thus fore and hind dune communities exhibited different responses to bitou management regimes.     

Temporal and spatial variations in dominance,diversity and biotic indices along a limestone stream receiving a trout farm effluent

Benthic macroinvertebrate response to organic pollution generated by a trout farm, located in the upper Rio Tajuña (Central Spain), was evaluated by calculating Whittaker's and Camargo's dominance indices; Margalef s, Menhinick's, Camargo's, Shannon's and MacArthur's diversity indices; and several biotic indices, including the Trent Biotic Index (TBI), the Chandler Biotic Score (CBS), the Biological Monitoring Working Party (BMWP), the Average Score Per Taxon (ASPT) and the Overall Quality Rating (OQR). An upstream sampling site (S-1) and three downstream stations placed 10 (S-2), 150 (S-3) and 1000 (S-4) m below the fish farm outlet were selected along the study area. Site S-3 was situated just below a man-made waterfall (1.8 m in height). Winter, spring and summer macrobenthic surveys were conducted during 1986. Plecopterans, ephemeropterans, coleopterans, trichopterans, amphipods and planarians decreased in abundance or were basent at downstream sampling sites, whereas simuliids, leeches, chironomids and tubificid worms increased in abundance. All diversity and biotic indices had highest and lowest values at S-1 and S-2, respectively, and higher values at S-3 (below the waterfall) than at S-4. However, Shannon's and MacArthur's diversity indices and the TBI were less effective in quantifying differences among sampling sites, exhibiting the lowest positive coefficients of linear correlation with species richness and other diversity and biotic indices. Both dominance indices had highest values at S-2, but similar values at S-1, S-3 and S-4. Biotic indices (except the TBI) and Margalef s, Menhinick's and Camargo's diversity indices appear to be the most sensitive measures for assessing macroinvertebrate response to changes in environmental conditions downstream from the fish farm. In addition, temporal variation in species richness, Margalef s index and biotic indices was similar, exhibiting their highest coefficients of variation at S-4. It is concluded that small waterfalls may improve the streamns self-purification of organic pollution generated by trout farms.     

Response of soil micro- and mesofauna to diversity and quality of plant litter

The abundance and functional structure of soil micro- (nematodes) and mesofauna (collembolans and mites) in relation to species diversity and initial C:N ratio of plant litter were studied in a field mesocosm experiment. A total of five litter treatments were applied to generate an increasing diversity of plant species (one, three and 12 species) and/or differences in initial C:N ratio of the litter (low, intermediate and high ratio). Samples were taken 3, 6 and 24 months after the litter exposure. On each sampling date litter and underlying sand samples were taken. Our results showed that litter quality, but not litter diversity was the factor which affected the three animal groups under study. The effect of litter was dependent on the time of litter exposure. Nematode fauna colonized litter earlier than the two mesofaunal groups. Nematodes responded apparently to litter quality gradient at early stages of litter decomposition. Three months after the start of the experiment the highest density of nematodes was noticed in single species litter of Trifolium pratense. Bacterial-feeding nematodes dominated in all litter treatments; on the first sampling date their percent share in Trifolium litter reached even 99.9%. Opposite to nematodes at late stages of litter decomposition the two mesofaunal groups seemed to show some preferences for low quality litter of Festuca rubra. Collembolan and nematode diversity was affected in similar way by the litter quality; the lowest diversity of the animal communities was found in the litter of the lowest initial C:N ratio. Maturity index of nematode communities was found to be a good index to differentiate between litters of different quality. The abundance and community structure of the three animal groups in underlying sandy soil was not significantly influenced by experimental conditions.     

The importance of the gravel excavation industry for the conservation of grassland butterflies

Conservation biology often relies on the protection of (semi)natural habitat remnants. However, the ever increasing human population is taking over natural resources and habitats. Here, contrary to most other studies, we ask how human-associated severe changes in the environment can be used to enrich local biodiversity. We tested if industrial activity (gravel excavation) leads to the creation of habitats that support grassland butterflies and how these areas add to the richness of local species when compared to typical semi-natural habitats (grasslands). We also identified key factors affecting the richness, abundance, diversity and commonness of butterfly species to provide practical recommendations. Species richness, diversity index and the occurrence of rare species were higher in gravel-pit shores than in grasslands. The richness of butterfly species and their abundance were positively affected by the richness of plant species, shrub density and age of the gravel-pit but negatively by the cover of water reservoirs in the surrounding area and the isolation of gravel-pits from grasslands. Butterfly diversity was positively influenced by the richness of plant species and proximity of human settlement but negatively by area of the shore and isolation. Our study is the first one to show the high value of gravel-pits for the conservation of butterflies. We recommend the inclusion of gravel-pits in a system of ecological networks and management of their surroundings to improve the colonization rate of rare species. We suggests that directing interest to the possible positive effects of industrial development on biodiversity may support conservation efforts.     

Effects of agricultural landscape and pesticides on parasitism in native bullfrogs

Native amphibian populations are shrinking worldwide, and both parasitic infections and environmental stress from agriculture have been implicated. We investigated the principal hypothesis that environmental by-products of agricultural activity mediate parasitism in native frogs. Bullfrogs were collected from wetlands with variable landscape disturbance and water quality and examined for helminth parasites. We predicted that pesticide pollution and landscape development would be significant factors shaping the parasite communities and populations. Parasite diversity and species richness were lower in wetlands impacted by both pesticides and land use. Two parasite groups, direct life-cycle nematodes and echinostomes, were common in polluted habitats, potentially increasing frog pathology and mortality risk. In areas with agricultural landscape and reduced forest cover, parasite diversity and species richness were low, perhaps because of less parasite transmission from birds and mammals. This result suggests that land development limits terrestrial vertebrate access to wetlands. Our results indicate that parasite abundance and community structure in wetlands are influenced by factors operating locally within the wetland and more broadly in the surrounding landscape. We suggest that parasite communities in amphibians are effective indicators of ecosystem health and animal biodiversity, and thus useful tools for conservation biology.