Species-specific distribution of two sympatric Maculinea butterflies across different meadow edges

An important consequence of habitat fragmentation is the increase of edge habitats. Environmental factors in the edges are different from those in the interiors, which causes changes in the distribution of plant and animal species. We aimed to study how edges affect the distribution of two butterfly species within meadow fragments. We therefore investigated the effect of distance from edge and edge type (road edge versus tree edge) on two sympatric large blue species (Maculinea teleius and M. nausithous). Our results showed that edge type had contrasting effects on the two species. M. teleius favoured both interiors and road edges, while M. nausithous preferred the tree edges. In the case of the latter species a strong positive edge effect was also found. This kind of within-habitat niche segregation is probably related to the different microenvironmental conditions at the edges. Foodplant density did not seem to limit the distribution of these species. Our results suggest that interiors of meadows are important for M. teleius, while tree edges maintain the habitats of the regionally rarer butterfly, M. nausithous.     

Road density and wetland context alter population structure of a freshwater turtle

Roads are detrimental to wildlife populations that require contiguous networks of terrestrial and aquatic habitats. Many species of freshwater turtles are sensitive to habitat fragmentation caused by roads, and are susceptible to road mortality during overland migrations. The common long‐necked turtle (Chelodina longicollis) is an Australian freshwater turtle that frequently moves between wetlands, and so populations may incur negative impacts from road effects. Here, we assessed the relationship between C. longicollis and road density and landscape variables within populations inhabiting 20 wetlands distributed throughout greater Melbourne, Australia. The size frequency distribution of C. longicollis at sites surrounded by high road densities was skewed towards larger individuals, but there was no difference in the frequency of juveniles between high and low road density sites. Regression modelling revealed a clear positive relationship between road density and carapace length (CL) of C. longicollis; the mean CL at a site with the highest road density was predicted to be 23% greater than mean CL at a site surrounded by no roads. Female CL was also positively related to road density. There was a clear positive relationship between wetland age and CL, although this relationship was not as strong. While there was no relationship evident between road density and the proportion of female C. longicollis at a site, more females were captured at smaller ephemeral sites surrounded by a high proportion of green open space and located near drainage lines. We did not find evidence of sex‐related differences in road effects. These results suggest that roads may be affecting C. longicollis in the study area, but the direct cause of any effects is difficult to identify.     

Avian spatial segregation at edges and interiors of urban parks in Madrid, Spain

Few studies have investigated the effects of urban landscape composition on avian habitat selection at urban-park edges. I assessed how the number of species, density of guilds, and density of individual species varied between edge and interior habitats in six large wooded parks in Madrid (Spain), and analysed such patterns in relation to habitat structure, car traffic, and pedestrian traffic. Few differences in habitat structure were found; whereas car and pedestrian traffic were significantly higher at edges. Species foraging in trees and on the ground, and nesting in trees and in tree cavities had lower numbers and breeding densities at edges, probably as a result of the disturbance from traffic noise and pedestrians. Species highly habituated to human activities (House Sparrows Passer domesticus and Rock Doves Columba livia) displayed opposite patterns, with higher breeding densities at urban-park edges, probably due to their higher foraging opportunities (refuse, people leftovers, deliberate feeding) and nest site availability in adjacent buildings. Urbanisation sprawl may increase the prevalence of edge specialists and diminish the representation of species with specific habitat requirements.     

Roads and bats: a meta‐analysis and review of the evidence on vehicle collisions and barrier effects

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Changes in plant species composition and litter production in response to roads and trails in the laurel forest of Tenerife (Canary Islands)

Abstract

Road density has increased in the Canary Islands' forests during the last century, affecting an unknown amount of forested area. We studied road effects on vegetation in the relict laurel forest of Tenerife. We assessed edge effects on plant species richness, plant composition and litter production. Effects of anthropogenic corridors on vegetation differed between paved roads and unpaved trails. Opportunistic species (shade intolerant) dominated road edges, but composition differed among all sites. Multivariate analysis revealed convergence in species composition along the corridor-interior gradient. For trails, both species richness and litter production did not differ significantly between edge and interior. Road edge effects on vegetation were detectable only within the first 10 m towards the interior. This suggests that the main effects of roads and trails on species richness are limited to the immediate edge of the laurel forest. Litter fall along road edges was half that of the interior. However, no significant differences were detected due to the high variability of the data. A buffer of approximately 10 m would result in the reduction of the total area of the remaining undisturbed laurel forest. Based on these results, the building of new paved roads should not be considered. Low human population inflow into the Anaga Rural Park needs to be maintained on a sustainable basis. Forest managers should take these road/trail effects into account when planning new road openings in this ecosystem.     

An Endangered Arboreal Specialist,the Western Ringtail Possum (Pseudocheirus occidentalis), Shows a Greater Genetic Divergence across a Narrow Artificial Waterway than a Major Road

The fragmentation of habitats by roads and other artificial linear structures can have a profound effect on the movement of arboreal species due to their strong fidelity to canopies. Here, we used 12 microsatellite DNA loci to investigate the fine-scale spatial genetic structure and the effects of a major road and a narrow artificial waterway on a population of the endangered western ringtail possum (Pseudocheirus occidentalis) in Busselton, Western Australia. Using spatial autocorrelation analysis, we found positive genetic structure in continuous habitat over distances up to 600 m. These patterns are consistent with the sedentary nature of P. occidentalis and highlight their vulnerability to the effects of habitat fragmentation. Pairwise relatedness values and Bayesian cluster analysis also revealed significant genetic divergences across an artificial waterway, suggesting that it was a barrier to gene flow. By contrast, no genetic divergences were detected across the major road. While studies often focus on roads when assessing the effects of artificial linear structures on wildlife, this study provides an example of an often overlooked artificial linear structure other than a road that has a significant impact on wildlife dispersal leading to genetic subdivision.     

Change in habitat resources and structure near urban edges and its influence on the squirrel glider (Petaurus norfolcensis) in southeast Queensland,Australia

Urban landscapes often expose wildlife populations to enhanced edge effects where the biotic and abiotic attributes of native ecosystems have been significantly altered. While some species may respond favourably to edges, there are likely to be varying negative consequences for many forest‐dependent species. In particular, marsupial gliders are influenced by changes in forest composition and structure near edges due to highly specific feeding and nesting requirements, and a high reliance on tree cover to traverse a landscape. We addressed this problem using the squirrel glider (Petaurus norfolcensis) in the fragmented urban landscape of southeast Queensland, Australia. Analysis of variance was applied to determine differences in habitat resources and structure in relation to glider presence and trap success rates in forest fragment interiors compared with road (minor & major) and residential edge habitats. We postulate that an increased presence of squirrel gliders in sites adjacent to minor road and residential edges may be due to the availability of additional resources and/or varying dispersal opportunities. Conversely, forest fragment interiors contain a higher abundance of nest hollows and large trees, together with a greater floristic species richness providing more reliable seasonal foraging sources, which may explain the greater trap success rates of squirrel gliders in these sites. We conclude that while forest fragment interiors provide habitat suitable for year‐round use by greater numbers of squirrel gliders, the conservation value of some edge habitats that provide additional resources and dispersal opportunities should not be underestimated for forest‐dependent mammals; however, each edge type must be assessed individually.     

Comparative use of forest habitats by roe deer and moose in a human-modified landscape in southeastern Norway during winter

The negative impact of anthropogenic disturbance and land-use changes on large mammals is generally recognized within conservation biology. In southeastern Norway, both moose (Alces alces) and roe deer (Capreolus capreolus) occur throughout human-modified landscapes, facilitating an interesting comparative study of their habitat use. By using pellet group counts, we looked at the importance of forest structure, vegetation characteristics and human disturbance (e.g., distance to the nearest house, nearest paved road, and nearest edge between field and forest) in shaping the winter distribution of both species at multiple spatial scales, in non-agricultural habitats. Moose occurred more often in areas with higher densities of heather and Vaccinium sp. in the ground layer, and used areas with more open forest structure. The proportion of built-up areas, within a 1,000-m buffer, negatively influenced moose occurrence. Roe deer occurred more often in areas with deciduous trees and patches with juniper and Vaccinium sp. in the ground layer, used areas near roads less, but were significantly associated with areas near the field–forest ecotone. The proportion of built-up areas positively influenced roe deer distribution within a 2,500-m buffer. Roe deer seem to be able to persist in more human-dominated landscapes, possibly due to the availability of field–forest edges providing both high-quality fodder and cover in close proximity. Moose, on the contrary, did not show any preference for areas associated with human disturbance, and their distribution was only associated with patches providing food.     

Effects of habitat fragmentation and road density on the distribution pattern of the moor frog Rana arvalis

1. The effects of habitat fragmentation on the distribution pattern of the moor frog Rana arvalis were investigated. Also, the possible isolation effects of the road network were taken into account.
2. Indications were found that habitat fragmentation partly explains the distribution pattern of the moor frog. The statistical models showed a positive effect of pond size (or marsh area) and a negative effect of road density on the probability of occupation of a moorland pond.
3. Because of the strong correlation between habitat quality variables and isolation variables, no unambiguous effects of isolation, described as the amount of suitable terrestrial habitat (moorland) in the surroundings of a moorland pond in a radius of 100–2000 m, could be demonstrated.
4. Spatial differences in road density can play a role in the selection of optimal locations for nature protection areas. The regression model used in this study predicts a reduced occupation probability in 55% of the study area. In the part of the study area adjacent to a motorway, occupation probability is lowered to less than 30%.
5. European studies of habitat fragmentation on amphibian species revealed a mean distance between occupied ponds of <1 km in all studies. This could be a general rule of thumb for persistent amphibian populations. Effects of pond size on the probability of occupation were more variable.
6. When discussing the effects of habitat fragmentation on amphibians and other ground dwelling species, the negative effects of roads are often underestimated.     

Experimental effects of habitat fragmentation on rove beetles and ants: patch area or edge?

The effects of habitat fragmentation may include the loss of species from isolated fragments or changes in species abundances among habitats that differ in area, structure, or edge characteristics. We measured the species richness and abundance of ground‐dwelling insects in a 1.14‐ha old field that was mowed to produce patches of unmowed vegetation which differed in size, degree of isolation, and the amount of habitat edge. Four treatments – ranging from unfragmented (169‐m²) to highly fragmented (1‐m²) patches – were replicated four times in a Latin square design, and insects were sampled twice during 1995 using 177 pitfall traps. Species richness showed a non‐monotonic response to fragmentation, with the fewest species occurring in the slightly fragmented treatment. Responses of rove beetles and ants, the most species‐rich and abundant taxa, respectively, were similar to the overall insect community but ants had a stronger and more consistent treatment effect in both sample months. Ordinations of ant and rove‐beetle assemblages using nonmetric multidimensional scaling showed that the slightly fragmented treatment differed from other treatments in species occurrence and abundance. The lower species richness in the slightly fragmented treatment was primarily due to a subset of ant and rove beetle species that showed a lower abundance than in other treatments, possibly because this treatment had the greatest amount of habitat edge. We hypothesize that the non‐monotonic species response to fragmentation was due to the differential effects of habitat edge on species movements across the habitat boundary between unmowed patches and mowed areas. A greater effect due to the amount of habitat edge rather than total patch area, at least among the range of patch sizes studied, suggests that the length of habitat edge may be quite important to the distribution and abundance of ground‐dwelling animals in fragmented habitats.     

Spider abundance and diversity in apple orchards under three insect pest management programmes in Washington State,U.S.A.

1 Many apple growers in Washington State, U.S.A. use mating disruption (MD) for control of codling moth, Cydia pomonella (Linnaeus). Fewer applications of synthetic, broad‐spectrum insecticides are made in MD orchards than in orchards under conventional (C) management. Spider abundance and diversity in MD, C and certified organic (O) orchards were compared. Spiders inhabiting the trees (arboreal), the understory vegetation, and the ground surface were studied. 2 Total arboreal spider density and total understory spider density were significantly higher in O orchards than in MD and C orchards. Many species occurred in both the trees and the understory. 3 Arboreal, visually orientated, hunting spiders and arboreal ambushers/runners were significantly more abundant in O orchards compared to C and MD orchards. Visual hunters were significantly more abundant in MD compared to C orchards. Numbers of spiders in two other guilds (web‐makers and nocturnal hunters) showed no statistical differences with respect to orchard management type. 4 The highest density of ground surface‐dwelling spiders occurred in one of the O orchards. Two C orchards had higher densities than any MD orchard. Ground surface species were distinct from those in the understory and the trees. 5 With one exception, an orchard's arboreal fauna was most similar to that of another orchard under the same type of pest management. Three exceptions were noted among comparisons of the understory faunas. The ground surface‐dwelling fauna of one O orchard was distinctive, whereas that in the second O orchard was similar to the C and MD orchards. 6 Reduced use of synthetic, broad‐spectrum insecticides in MD orchards did not result in arboreal spider densities comparable to those found in O orchards. A contributing factor may be that all species were univoltine. Spider populations may thus be severely reduced by even a small number of synthetic, broad‐spectrum insecticide applications and the time required for recovery may be lengthy.     

Edge effects on ground beetles at the woodlot–field interface are short‐range and asymmetrical

• 1 Boundaries between woodlots and agricultural habitats are numerous in temperate agricultural landscapes and influence ecological processes in both woodlots and agricultural habitats.
• 2 We aimed to determine how far the species assemblage of ground beetles in woodlot and open habitats was influenced by the presence of the woodlot–field boundary.
• 3 We studied the distribution of ground beetles on both sides of the boundaries of four woodlots along transects of pitfall traps (n = 140). The depth of edge influence (i.e. the distance from the boundary at which the presence of the boundary has no more significant influence) on the species assemblage of ground beetles in each woodlot and in each agricultural habitat was determined with nonlinear canonical analysis of principal coordinates, an ordination method that is followed by nonlinear regression of the principal coordinates on distance from the boundary.
• 4 The depth of edge influence on the species assemblages of ground beetles was asymmetrical relative to the boundary: it was generally higher and had higher variability in open habitats (14.4 ± 12.3 m) than in woodlots (4.9 ± 2.3 m). Species assemblages of ground beetles in edges were a mix between both adjacent species assemblages. Edge effects in woodlots were deeper in the woodlots exhibiting a deeper penetration of open habitat species. Symmetrically, edge effects in open habitat were deeper in the open habitats with a deeper diffusion of forest species into the open habitat.
• 5 Forest ground beetles were not threatened by edge effects. Rather, edge effects are likely to benefit agriculture, mostly through the dispersal of predatory forest species into agricultural fields.

     

Ecological and morphological diversification within single species and character displacement in Mandarina,endemic land snails of the Bonin Islands

The endemic land snail species Mandarina hahajimana has undergone extensive habitat and morphological diversification within the Hahajima islands in the Bonin archipelago. This species has diversified into populations with ground, arboreal and semi-arboreal life histories. In addition, arboreal populations and semi-arboreal populations show diversification in preferences of species and positions of the tree on which they are found. Shell morphologies of M. hahajimana exhibit remarkable geographical variation, and they have a clear relationship with their life histories. The morphological variation of M. hahajimana results from adaptation to different lifestyles. The habitats of these populations influence the relationships with other species of Mandarina coexisting with M. hahajimana. This suggests that the morphological and ecological divergence within M. hahajimana has been induced by competitive interaction with other species of Mandarina. Character displacement may have played an important role in promoting adaptive radiation of Mandarina in the Bonin Islands.     

Effects of forest fragmentation on small mammals in an Atlantic Forest landscape

Recent studies on the effects of tropical forest fragmentation indicate that fragmented landscapes are complex and heterogeneous systems influenced by factors other than the size or degree of isolation of forest remnants: of particular importance are the quality of the matrix and the edge-induced habitat changes. In order to investigate the influence of these factors, small mammals were surveyed in 36 sites in the landscape of Una, a region that encompasses some of the last and largest Atlantic Forest remnants in northeastern Brazil. Six sites were distributed on each of six landscape components – the interiors and edges of small remnants, the interiors and edges of large remnants, and the most common forested habitats found in the matrix. The survey comprised 46,656 trap-nights and yielded 1725 individuals of 20 species of rodents and marsupials. Results revealed: an increase in beta-diversity caused by fragmentation; the contrasting effects of the altered forested habitats of the matrix, which harbor both forest and disturbance-adapted species; a greater importance of edge effect than of patch size to the observed changes in small mammal community in remnants; an association among terrestrial forest species and among arboreal forest species in terms of the distribution and abundance in the Una mosaic; and a distinctive vulnerability of these two groups of species to fragmentation. Results emphasize the biological importance and conservation value of both fragmented landscapes and small remnants in the Atlantic Forest, as well as the importance of management techniques to control and attenuate edge effects.     

Habitat edges affect patterns of artificial nest predation along a wetland-meadow boundary

Wetland habitats are among the most endangered ecosystems in the world. However, little is known about factors affecting the nesting success of birds in pristine grass-dominated wetlands. During three breeding periods we conducted an experiment with artificial ground nests to test two basic mechanisms (the matrix and ecotonal effects) that may result in edge effects on nest predation in grass-dominated wetland habitats. Whereas the matrix effect model supposes that predator penetrate from habitat of higher predator density to habitat of lower predator density, thus causing an edge effect in the latter, according to the ecotonal effect model predators preferentially use edge habitats over habitat interiors. In addition, we tested the edge effect in a wetland habitat using artificial shrub nests that simulated the real nests of small open-cup nesting passerines. In our study area, the lowest predation rates on ground nests were found in wetland interiors and were substantially higher along the edges of both wetland and meadow habitat. However, predation was not significantly different between meadow and wetland interiors, indicating that both mechanisms can be responsible for the edge effect in wetland edges. An increased predation rate along wetland edges was also observed for shrub nests, and resembled the predation pattern of real shrub nests in the same study area. Though we are not able to distinguish between the two mechanisms of the edge effect found, our results demonstrate that species nesting in wetland edges bordering arable land may be exposed to higher predation. Therefore, an increase in the size of wetland patches that would lead to a reduced proportion of edge areas might be a suitable management practice to protect wetland bird species in cultural European landscapes.     

Living on the verge: are roads a more suitable refuge for small mammals than streams in Mediterranean pastureland?

The retention of natural habitat corridors is a useful and practical conservation tool that can attenuate the effects of habitat loss and fragmentation on wildlife. Linear structures may contribute to the conservation of biodiversity by providing additional habitats for small fauna living in highly modified environments. We assessed the importance of road verges as refuge areas for small mammals, in highly intensified grazed pastures, within a Mediterranean landscape and compared the role of road verges as refuges with that of riparian galleries, which have been described as important shelter locations for small fauna. For this purpose, a small mammal trapping study was undertaken on two road verges and beside two small streams in southern Portugal. We captured 457 individuals of five different species, with Mus spretus the most common species captured, followed by Crocidura russula. Captures were 4.6-fold higher immediately beside both roads and streams than 12 m away in the surrounding matrix. Individuals captured in the matrix presented a smaller body size and lower body condition, suggesting that this suboptimal habitat is occupied mainly by subadults. M. spretus was 46% more abundant by roads than by streams, while C. russula was present in similar numbers in both habitats. M. spretus individuals were larger near streams but exhibited no difference in body condition between habitats. C. russula had a better body condition and slightly higher body lengths at roadsides. Our results show that roadside verges in intensively grazed Mediterranean landscapes act as important refuges and constitute equally vital habitats for small mammals as do riparian vegetation strips in landscapes where other suitable habitats are scarce.     

Forest edges enhance mate‐finding in the invasive European gypsy moth,Lymantria dispar

Habitat type, fragmentation, and edge effects can play important roles in the mate‐finding abilities of many species. These effects can be particularly pronounced in low‐density populations, which are often found at the margins of species' ranges or at the leading edge of an invasion. The European gypsy moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), is a non‐native insect defoliator in the USA and Canada, where flightless females attract male moths through pheromone production and local extirpation of low‐density populations can be due to mate‐finding failure. To assess the effects of habitat edges on the ability of gypsy moths to find mates, we conducted a release experiment with male gypsy moths using female‐baited trap arrays in fields, at forest edges, and in the forest interior. Reduced mate‐finding was expected in fields and near forest edges based on geographic variation in invasion rates, male flight behavior, and pheromone plume dynamics. However, we found that mate‐finding was highest at forest edges, reduced in fields, and lowest within the forest interior. Within an array, traps closest to the forest edge also had the highest mate‐finding, suggesting that habitat characteristics can influence male flight direction in addition to pheromone cues. These results suggest that a moderate level of forest fragmentation enhances mate‐finding ability in the gypsy moth. Understanding the relationship between habitat heterogeneity and mate‐finding success in invasive species can inform predictions of future spread and assist with management plans that target mating disruption.     

Systematic revision of the arboreal snail Satsuma albida species complex (Mollusca: Camaenidae) with descriptions of 14 new species from Taiwan

The taxonomy of the endemic arboreal snail Satsuma albida species complex from Taiwan was unclear due to the animals' highly similar morphology, and their nocturnal and strict arboreal behaviour, leading to difficulties in collecting living specimens. This article is the first comprehensive comparative study on the systematics and taxonomy of this species complex using external morphology, anatomy of the reproductive system and molecular phylogeny. Consequently, two subspecies of S. albida are raised to species status, namely S. insignis and S. mollicula. Fourteen new species are also described. Fourteen of the 17 species showed polymorphism in banding pattern amongst populations and other species retained the whitish unity as seen in S. albida. Distributions of almost all taxa are geographically limited, with the exception of S. polymorpha sp. nov . The phylogeny of these species was reconstructed using 20 morphological characters and molecular data from the partial sequences of mtDNA CO1 and 16S rRNA genes, and the complete ITS2 sequence. The molecular phylogeny revealed three subclades (west, east and polymorpha clade) and revealed that these snails are monophyletic, originating from a ground‐dwelling ancestor. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 437–493.     

Differential effects of anthropogenic edges and gaps on the reproduction of a forest‐dwelling plant: The role of plant reproductive effort and nectar robbing by bumblebees

Forest fragmentation produces sharp changes in the spatial configuration of remnant forest patches, which include the increasing influence of patch edges on the interior of forest patches (‘edge effects’). Human activities responsible for forest fragmentation tend also to change the internal characteristics of remnant patches, for example, through the creation of gaps by selective logging. While edges and gaps can be expected to cause comparable changes in the micro‐environmental conditions of the forest, their effects on forest‐dwelling species and their interactions are not necessarily comparable. This study compares the effect of forest edges and anthropogenic gaps on the reproductive success of a self‐incompatible epiphytic plant (Mitraria coccinea), mediated by changes in its relationship with mutualists (pollinators) and antagonists (flower larcenists). Mitraria coccinea's flowers are pollinated by hummingbirds and robbed by the bumblebee Bombus dahlbomii. Edges and gaps had comparable positive effects on flower production and fruit set; however, nectar robbing was up to sevenfold higher in patches with numerous gaps and resulted in lower reproductive success (fruit set and total fruit crop). Forest fragmentation studies should therefore avoid treating forest remnants as homogeneous units (i.e. focusing exclusively on their characteristics and connectivity), without taking into account the internal heterogeneity caused by anthropogenic pressures (e.g. gaps and edge effects).