Habitat requirements for the conservation of wood cricket (Nemobius sylvestris) (Orthoptera: Gryllidae) on the Isle of Wight, UK

In the UK, wood cricket (Nemobius sylvestris) is a ‘Species of Conservation Concern’, being restricted to only three areas in southern England. Little information is available on the specific habitat requirements of this species. In 2006, a field investigation within three woodlands on the Isle of Wight was undertaken to identify its habitat preferences. Factors positively influencing wood cricket presence within woodlands included the presence of a well-developed leaf litter layer, relatively low ground vegetation cover and height, low canopy cover and relatively short distances between individual populations. Regression models identified the degree of isolation and variables describing vegetation structure as the main predictors for wood cricket presence within woodland fragments. The results of this study indicate the preference of wood cricket for open wooded edges. Conservation efforts for this species should focus on continuation of regular management activities aimed at providing permanent open edge habitat within woodlands, to maintain viable populations.     

Habitat use and dispersal characteristic by <Emphasis Type="Italic">Stethophyma grossum</Emphasis>: the role of habitat isolation and stable habitat conditions towards low dispersal

Species in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, are expected to be in danger of extinction. We hypothesize according to Kisdi’s theory (Am Nat 159:579–596, 2002) that species in fragmented landscapes with isolated habitats in general tend to possess low dispersal. In order to verify this hypothesis we studied the movement patterns of Stethophyma grossum, a hygrophilous species of wetlands, by mark–release–recapture techniques in a landscape with scattered suitable habitats over 3 years. The study focused on the major population in this landscape (site #1) as dispersal behaviour was assumed to be greatest. Actually, marked individuals of S. grossum were never found in any further suitable habitats in close vicinity to site #1. Despite that the peatland meadow of study site #1 was all over covered with homogenous vegetation only 6% (1.8 ha) of the whole area (30 ha) were occupied by S. grossum. The mean recapture rate over 3 years amounted to 39% with no significant differences between males and females. Both covered little distances within their mean range size of 1.8 ha; the median distances were 36.91 m for males and 26.65 m for females. We confirm the hypothesis that sub-populations of species in longstanding naturally isolated habitats, which habitat conditions have been stable; evolved low dispersal with little movements which are routine movements to find mating partners or food.     

Mating system and pollen flow between remnant populations of the endangered tropical tree, <Emphasis Type="Italic">Guaiacum sanctum</Emphasis> (Zygophyllaceae)

Tropical trees are generally long-lived making it difficult to assess the long-term effects of habitat fragmentation on genetic diversity. Maintenance of genetic diversity in fragmented landscapes is largely dependent on the species’ mating system and the degree of genetic connectivity (seed and pollen flow) among fragments. Currently, these parameters are largely unknown for many endangered tropical tree species. Additionally, landscape fragmentation may isolate tropical tree populations from larger, more continuous populations. The role of isolated individuals in pollen transfer within and between remnant populations is not clear. In this study, we estimate the mating system and pollen flow patterns in continuous and remnant populations of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae). Fractional paternity analyses were used to estimate average gene flow distances between fragmented remnant populations and the siring success of an intermediately located, but isolated individual. In these populations, G. sanctum is a mixed-mating species (t _m = 0.72 − 0.95) whose pollen is transported over large distances (>4 km). An isolated tree may have functioned as a stepping-stone between two clusters of individuals, assisting long-distance pollen movement. This individual also sired a disproportionately high number of seeds (13.9%), and is thus an important component of the reproductive success of these populations, thus rejecting Janzen’s “living-dead” hypothesis. The high levels of genetic diversity maintained as a consequence of long-distance pollen-flow suggest that this endangered species may have the potential for future adaptation and population expansion if suitable habitats become available.     

Importance of Interhabitat Gaps and Stepping-Stones for Lesser Woodcreepers (Xiphorhynchus fuscus) in the Atlantic Forest, Brazil

Translocation experiments showed that a woodcreeper bird species is able to move between isolated forest fragments, but this ability is limited by increasing interpatch distances. Larger distances (> 100 m) were overcome by using small stepping‐stones (isolated trees), which enhance connectivity and are useful for the species conservation in fragmented landscapes.     

Movement and dispersal patterns in the bush cricket Pholidoptera griseoaptera: the role of developmental stage and sex

Abstract.  1. To persist in a highly fragmented environment, such as the intensively used agricultural landscapes of Europe, species may need to successfully disperse between sub-populations. This paper describes a capture – mark – resight experiment to investigate movement and dispersal patterns of the flightless bush cricket species Pholidoptera griseoaptera .
2. Movement parameters showed little difference between juveniles and imagos as well as between males and females. Both developmental stages and sexes moved considerable distances, were cap\able of crossing habitat boundaries, and showed successful inter-patch dispersal through the agricultural matrix.
3. The results suggest that P. griseoaptera exhibits movement behaviours that compensate for its inability to fly. It was concluded that the good dispersal ability exhibited by animals of both sexes and developmental stage is an important factor allowing P. griseoaptera to persist in fragmented agricultural landscapes.     

Landscape structure shapes habitat finding ability in a butterfly

Land-use intensification and habitat fragmentation is predicted to impact on the search strategies animals use to find habitat. We compared the habitat finding ability between populations of the speckled wood butterfly (Pararge aegeria L.) from landscapes that differ in degree of habitat fragmentation. Naïve butterflies reared under standardized laboratory conditions but originating from either fragmented agricultural landscapes or more continuous forested landscapes were released in the field, at fixed distances from a target habitat patch, and their flight paths were recorded. Butterflies originating from fragmented agricultural landscapes were better able to find a woodlot habitat from a distance compared to conspecifics from continuous forested landscapes. To manipulate the access to olfactory information, a subset of individuals from both landscape types were included in an antennae removal experiment. This confirmed the longer perceptual range for butterflies from agricultural landscapes and indicated the significance of both visual and olfactory information for orientation towards habitat. Our results are consistent with selection for increased perceptual range in fragmented landscapes to reduce dispersal costs. An increased perceptual range will alter the functional connectivity and thereby the chances for population persistence for the same level of structural connectivity in a fragmented landscape.     

Seed‐dispersal interactions in fragmented landscapes – a metanetwork approach

Mutualistic interactions repeatedly preserved across fragmented landscapes can scale‐up to form a spatial metanetwork describing the distribution of interactions across patches. We explored the structure of a bird seed‐dispersal (BSD) metanetwork in 16 Neotropical forest fragments to test whether a distinct subset of BSD‐interactions may mediate landscape functional connectivity. The metanetwork is interaction‐rich, modular and poorly connected, showing high beta‐diversity and turnover of species and interactions. Interactions involving large‐sized species were lost in fragments < 10 000 ha, indicating a strong filtering by habitat fragmentation on the functional diversity of BSD‐interactions. Persistent interactions were performed by small‐seeded, fast growing plant species and by generalist, small‐bodied bird species able to cross the fragmented landscape. This reduced subset of interactions forms the metanetwork components persisting to defaunation and fragmentation, and may generate long‐term deficits of carbon storage while delaying forest regeneration at the landscape level.     

Can agroforest woodlots work as stepping stones for birds in the Atlantic forest region?

In fragmented landscapes, agroforest woodlots can potentially act as stepping stones facilitating movement between forest fragments. We assessed the influence of agroforest woodlots on bird distribution and diversity in the Atlantic forest region (SE Brazil), and also tested which categories of species can use different types of connection elements, and whether this use is influenced by the distance to large forest patches. We studied two fragmented landscapes, with and without stepping stones linking large fragments, and one forested landscape. Using a point count, a bird survey was undertaken in the fragmented landscapes in five different elements: large remnants (>400 ha), agroforest woodlots (0.4–1.1 ha), small patches (0.5–7 ha), riparian corridor, and pasture areas (the main matrix). Generalist and open-area species were commonly observed in the agroforest system or other connection elements, whereas only a few forest species were present in these connections. For the latter species, the distance of woodlots to large patches was essential to determine their richness and abundance. Based on our results and data from literature, we suggest that there is an optimal relationship between the permeability of the matrix and the efficiency of stepping stones, which occurs at intermediate degrees of matrix resistance, and is species-dependent. Because the presence of agroforest system favors a higher richness of generalist species, they appeared to be more advantageous for conservation than the monoculture system; for this reason, they should be considered as a management alternative, particularly when the matrix permeability requirement is met.     

Dispersal capability in a habitat specialist bush cricket: the role of population density and habitat moisture

1. In fragmented landscapes many insect species depend on a regular exchange of individuals between subpopulations to ensure the persistence of the population. Thus, the ability to disperse is of particular relevance. 2. However, in some insect species mobility is not a fixed trait. Hence, knowing the causes of phenotypic plasticity is of great importance when evaluating whether a species is able to survive in fragmented landscapes or not. 3. A multi‐year field study was conducted to identify possible causes of macroptery in the wing‐dimorphic habitat specialist Metrioptera brachyptera L. and to quantify its dispersal capability (% macropters). Therefore, 746 individuals of the species were caught on 135 plots. Additionally, environmental variables that possibly induce the development of macropters (population density and habitat moisture) were recorded. 4. Dispersal capability of M. brachyptera was very low. Less than 3% were long‐winged. The statistical analysis revealed that the proportion of long‐winged M. brachyptera was strongly correlated with high bush‐cricket densities and not with habitat moisture. 5. The low dispersal capability of M. brachyptera leads to the conclusion that individual exchange between isolated populations is limited or even impossible. Habitat specialists, like M. brachyptera, may thus be unable to respond to rapid changes in the availability of suitable habitats by dispersing, and hence may be especially dependent on habitat management activities that promote the long‐term stability of existing habitat patches.     

Short Rotation Coppice (SRC) Plantations Provide Additional Habitats for Vascular Plant Species in Agricultural Mosaic Landscapes

Increasing loss of biodiversity in agricultural landscapes is often debated in the bioenergy context, especially with respect to non-traditional crops that can be grown for energy production in the future. As promising renewable energy source and additional landscape element, the potential role of short rotation coppice (SRC) plantations to biodiversity is of great interest. We studied plant species richness in eight landscapes (225 km²) containing willow and poplar SRC plantations (1,600 m²) in Sweden and Germany, and the related SRC α-diversity to species richness in the landscapes (γ-diversity). Using matrix variables, spatial analyses of SRC plantations and landscapes were performed to explain the contribution of SRC α-diversity to γ-diversity. In accordance with the mosaic concept, multiple regression analyses revealed number of habitat types as a significant predictor for species richness: the higher the habitat type number, the higher the γ-diversity and the lower the proportion of SRC plantation α-diversity to γ-diversity. SRC plantation α-diversity was 6.9 % (±1.7 % SD) of species richness on the landscape scale. The contribution of SRC plantations increased with decreasing γ-diversity. SRC plantations were dominated more by species adapted to frequent disturbances and anthropo-zoogenic impacts than surrounding landscapes. We conclude that by providing habitats for plants with different requirements, SRC α-diversity has a significant share on γ-diversity in rural areas and can promote diversity in landscapes with low habitat heterogeneity and low species pools. However, plant diversity enrichment is mainly due to additional species typically present in disturbed and anthropogenic environments.     

Patch occupancy by stone martens Martes foina in fragmented landscapes of central Spain: the role of fragment size,isolation and habitat structure

We studied the response to forest fragmentation of a generalist carnivore, the stone marten Martes foina, in highly fragmented landscapes of central Spain. Five different areas (n = 178 fragments) in central Spain were surveyed. This paper analyses the relationship between fragment use by martens (measured through scat presence) and a series of variables related to the size, isolation and vegetation structure of each fragment by means of stepwise logistic regression. Size and isolation have an important effect on stone marten presence in fragments. Our results were similar to those found for other marten species in landscapes with coarse-grain fragmentation, but they contrast with other studies conducted in landscapes with fine-grain fragmentation. These data suggested that in highly fragmented landscapes, size and isolation factors resulting from forest fragmentation were responsible for determining marten responses, irrespective of their habitat generalism. Management policies for the stone marten in highly fragmented scenarios require the maintenance of large forests near continuous forest tracts in mountains or riparian woodlands.     

Protected areas of Borneo fail to protect forest landscapes with high habitat connectivity

Throughout the world, previously extensive areas of natural habitats have been degraded and fragmented, and improving habitat connectivity may help the long-term persistence of species, and their ability to adapt to climate changes. We focused on Borneo, where many remaining areas of tropical forest are highly fragmented, and we assessed the extent to which Protected Areas (PAs) protect highly-connected forest sites. We analysed remotely-sensed land cover data (0.86 km² grid cell resolution) using ‘Zonation’ reserve design software, and we ranked grid cells (rank 0–1) according to forest extent and connectivity. PAs currently cover 9% of Borneo, but <20% of highly-connected cells (i.e. cells with Zonation ranks ≥0.9) lie within PAs. Approximately 65% of highly-connected cells were located above 400 m elevation, although >60% of Borneo’s total land area lies below 200 m and only 15% of highly-connected cells occurred in these low elevation areas. These findings were relatively insensitive to assumptions about species’ dispersal ability (within the range 1–20 km; representing relatively mobile animal species). The percentage of highly-connected grid cells within PAs could rise from <20 to >50% under proposed new PAs (including the ‘Heart of Borneo’ project), although many other highly-connected sites will remain unprotected. On-going land-use changes mean that existing PAs in lowland areas are likely to become increasingly isolated within inhospitable agricultural landscapes, and improving connectivity through reforestation and rehabilitation of degraded forest may be required to maintain the conservation value of these PAs in future.     

Wound reaction after bark harvesting: microscopic and macroscopic phenomena in ten medicinal tree species (Benin)

In Africa, little is known about how the vascular anatomy of medicinal tree species is influenced by bark harvesting, and the ability of species to react against debarking needs to be better understood. This study aims to evaluate the temporal and spatial impact of bark harvesting on wood anatomy and to determine the extent to which a tree’s ability to close the wound after bark harvesting is affected by anatomical changes in the wood. We harvested bark from ten medicinal tree species located in an Isoberlinia doka woodland in Central Benin. Two years after debarking, the wound closure was measured and one tree per species was cut at the wound level to collect a stem disc. On the cross section of each disc, vessel features (area, density and specific conductive area) were measured in the radial direction (before and after wounding) and on three locations around the disc surface. We found that during early wound healing, all species produced vessels with a smaller area than in unaffected wood and this significantly decreased the specific conductive area in eight of the investigated species. However, after 2 years, only six trees had restored their specific conductive area. In addition, a significant positive correlation (r = 0.64, P < 0.005) confirmed the relationship between the specific conductive area and tissue production to close the wound and delineated the study group into two groups of trees. Therefore, we concluded that vessels appeared to be very good anatomical indicators of the tree’s reactions to debarking.     

Assessing range re-expansion and recolonization of human-impacted landscapes by threatened species: a case study of the otter (Lutra lutra) in Italy

Detecting and understanding recoveries of threatened species from past and recent presence/absence data is essential to improving conservation efforts. However, false positive trends may be reported because of false absences in past data, therefore appropriate testing is needed. We tested an expansion/recolonization of the otter (Lutra lutra) populations in Italy from a fragmented distribution outlined in the 1984–1985 period by using Monte Carlo simulations. Land-use changes, human depopulation and decrease in influence of anthropogenic features were investigated as potential drivers of recolonization by using GIS modeling. A survey of the entire Italian range of the otter, conducted in 2002–2004, recorded a 2.2-fold increase in the proportion of occupied 10-km squares and 49 local colonizations. The range size and proportion of urban land-use in the 1984–1985 distribution were smaller (P < 0.05) than those derived from simulated surveys based on 49 random false absences versus colonization events. The distribution range expanded southward and nearly reached the southern margins of the peninsula. Recolonization of moderately urbanized landscapes was not accompanied by human depopulation. According to partial logistic regressions, the pure effect of urban land proportion and industry proximity on otter occurrence probability declined by about 48%, suggesting a decreased impact on the stream habitat. Conversely, natural factors, increased in importance by about 116%. The absence of a significant northward expansion in the 20 year period suggests that northward habitat restoration should be planned to encourage further recolonization. On the other hand, potential urban threats in the newly occupied landscapes should be controlled.     

Population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in a tropical urban‐fragmented landscape

With increasing urbanization, urban‐fragmented landscapes are becoming more and more prevalent worldwide. Such fragmentation may lead to small, isolated populations that face great threats from genetic factors that affect even avian species with high dispersal propensities. Yet few studies have investigated the population genetics of species living within urban‐fragmented landscapes in the Old World tropics, in spite of the high levels of deforestation and fragmentation within this region. We investigated the evolutionary history and population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in Singapore, a highly urbanized island which retains <5% of its original forest cover in fragments. Combining our own collected and sequenced samples with those from the literature, we conducted phylogenetic and population genetic analyses. We revealed high genetic diversity, evidence for population expansion, and potential presence of pronounced gene flow across the population in Singapore. This suggests increased chances of long‐term persistence for the olive‐winged bulbul and the ecosystem services it provides within this landscape.     

Demography,dispersal and movement pattern of <Emphasis Type="Italic">Euphydryas aurinia</Emphasis> (Lepidoptera: Nymphalidae) at the Iberian Peninsula: an alarming example in an increasingly fragmented landscape?

Mediterranean countries like Portugal and Spain, so far characterised by extensive traditional land use over major parts of their territories, have been less affected by species losses. However, they are facing severe changes. As a model organism we chose the butterfly Euphydryas aurinia, highly threatened in Central Europe but still common at the Iberian Peninsula, for a mark-release-recapture survey in the western Algarve. We examined key factors for stabile metapopulation systems to assess the ability of long-term survival in the increasingly fragmented landscapes of the Iberian Peninsula. The density of the examined population was high (ca. 2,200 individuals/ha). However, the MRR-based proportion of individuals moving longer distance classes showed a better fit to the negative exponential function than to the inverse power function implying restricted dispersal behaviour. The orientation pattern of short distance movements (<10 m) proved to be independent from habitat structures. In contrast, longer movements (>10 m) were strongly orientated along the main habitat axes revealing the importance of internal habitat structures for the orientation of dispersing individuals. Based on these data, we discuss the severe consequences for the fauna of the Iberian Peninsula in an increasingly fragmented and monotonous landscape.     

Evaluating contemporary pollen dispersal in two common grassland species Ranunculus bulbosus L. (Ranunculaceae) and Trifolium montanum L. (Fabaceae) using an experimental approach

Pollen flow is a key biological process that connects plant populations, preventing genetic impoverishment and inbreeding. Pollen‐mediated long‐distance dispersal (LDD) events are especially important for plant species in increasingly fragmented landscapes. Patterns of pollen dispersal were directly estimated and dispersal kernels modelled in an experimental population of Ranunculus bulbosus and Trifolium montanum to determine the potential for LDD. Eight and 11 microsatellite markers were used for R. bulbosus and T. montanum, respectively, to run a likelihood‐based paternity analysis on randomly chosen offspring (N_total = 180 per species) from five maternal plants. High rates of selfing were found in R. bulbosus (average 45.7%), while no selfing was observed in T. montanum. The majority (60%) of mating events occurred at very short distances: the median of the observed dispersal distances was 0.8 m in both species, and the average distances were 15.9 and 10.3 m in R. bulbosus and T. montanum, respectively. Modelling the pollen dispersal kernel with four different distribution functions (exponential‐power, geometric, 2Dt and Weibull) indicated that the best fit for both species was given by a Weibull function. Yet, the tail of the T. montanum pollen dispersal kernel was thinner than in R. bulbosus, suggesting that the probability for LDD is higher in the latter species. Even though the majority of pollen dispersal occurred across short distances, the detection of several mating events up to 362 m (R. bulbosus) and 324 m (T. montanum) suggests that pollen flow may be sufficient to ensure population connectivity in these herb species across fragmented grasslands in Swiss agricultural landscapes.     

Recolonization of forest fragments by a native rodent following experimental ‘extinctions’

The movement of organisms between subdivided populations is considered a key influence on the persistence of species in modified landscapes. In particular, the ability to recolonize ‘empty’ fragments of habitat is directly relevant to conservation management, and to understanding the link between pattern and process in metapopulations. We studied the movement and recolonization ability of the bush rat, Rattus fuscipes, in a highly fragmented agricultural landscape in south‐western Victoria, Australia. Populations were monitored in seven small (<2.5 ha) and two large (>49 ha) forest fragments before removal of all residents from four of the small fragments. Subsequent monitoring (for up to 16 months) allowed the detection of colonizing individuals, and comparisons between ‘experimental’ and ‘control’ fragments. Rattus fuscipes readily moved between fragments and successfully recolonized (i.e. both males and females arrived) two of four fragments in which extinctions were simulated. A single male moved into a third experimental fragment. In one fragment, new animals were detected 1 month after the removal of residents, indicating that recolonization can occur rapidly. Dispersers were not a random sample of the population: although both males and females, and adults and sub‐adults were recorded dispersing, adult males in reproductive condition predominated. Functional connectivity appears to be high for R. fuscipes in the study landscape. Results from this manipulative experiment provide direct empirical evidence that a capacity for movement allows recolonization of fragments of suitable habitat and is a key process responsible for species persistence in fragmented landscapes, as predicted by theory.     

Population genetics and fitness in fragmented populations of the dioecious and endangered <Emphasis Type="Italic">Silene otites</Emphasis> (Caryophyllaceae)

Population fragmentation is often correlated with loss of genetic diversity and reduced fitness. Obligate out-crossing (dioecy) is expected to enhance genetic diversity, reduce genetic differentiation, and avoid inbreeding depression through frequent gene flow. However, in highly fragmented populations dioecy has only diminishing effects upon genetic structure as pollination limitations (e.g. flight distance of pollinators) most often restrict inter-population gene flow in insect pollinated species. In fragmented dry grasslands in northeastern Germany, we analysed genetic structure, fitness, and habitat quality of the endangered dioecious Silene otites (Caryophyllaceae). Using AFLP markers, a high level of differentiation among ten populations was found (F _st = 0.36), while the intra-population genetic diversities (H _E = 0.165–0.240) were similar as compared to hermaphroditic species. There was neither a correlation between geographic and genetic distance nor between genetic diversity and population size, which indicates reduced gene flow among populations and random genetic drift. Plant size was positively correlated with genetic diversity. Seed set and number of juveniles were positively related to population size. Higher total coverage resulted in reduced plant fitness, and the number of juveniles was negatively correlated to cryptogam cover. Additionally, we found a sex ratio bias towards more male plants in larger populations. Overall, our results indicate that on a regional geographic scale dioecy does not necessarily prevent genetic erosion in the case of habitat fragmentation, especially in the absence of long distance seed and pollen dispersal capacity.