Genetic erosion in a stenotopic heathland ground beetle (Coleoptera: Carabidae): a matter of habitat size?

Two centuries ago large areas of north-west Europe were covered by coherent heathlands which hosted numerous specialized species. Changes in land use made heathlands fragmented and rare, consequently, they are in the focus of nature conservation efforts today. But how large should remaining heathland patches be in order to secure the survival of populations of specialized species? We investigated the genetic diversity at five allozyme loci of Poecilus lepidus, a flightless and stenotopic heathland ground beetle. 29 populations from differently sized heathland patches in north-west Germany were analyzed. Results show a weak but significant genetic differentiation and no evidence for isolation by distance or other patterns of spatial autocorrelation. Linear regression analysis revealed significant relationships between patch size, allelic richness, number of alleles and expected heterozygosity. These findings are explained by severe habitat fragmentation together with strong fluctuations in population size which have been reported for this species in the past. To conserve the vast majority of the species’ genetic diversity for a period of 100 years we suggest to maintain heathland patches of at least 50 ha in size.     

The elytra-to-body binding mechanism of the flightless rainforest species Tabarus montanus Kaszab (Coleoptera: Tenebrionidea)

The elytra-to-body binding mechanism of the flightless rainforest species Tabarus montanus Kaszab (Coleoptera: Tenebrionidea) is described. Previously, studies on this complex character system in tenebrionids have focused mostly on either fully-winged or flightless, desert-dwelling species with a hermetically sealed subelytral cavity. Data presented here show that the rainforest species Ta. montanus has permanently joined interlocking macrostructures between the two elytra along the midline and between the elytral epipleuron and the sides of the body. These are very similar adaptations to ones found in flightless desert tenebrionids. Frictional patches of microtrichia, previously reported in all wing-folding beetle suborders including flightless taxa, are completely absent in Ta. montanus. This constitutes the first report of the complete loss of frictional microtrichia patches in a beetle with fully-developed elytra. Sensory organs (hair sensilla), usually involved in the correct positioning of the elytra over the beetles’ body at rest are also absent in Ta. montanus. The significance of these results relating to the evolution of the tenebrionid subelytral cavity is discussed.     

Woodland fragmentation affects space use of Eurasian red squirrels

When habitats become fragmented, variation in patch size and quality are expected to impose changes on the spacing pattern and social organization of animal populations. General theory predicts different possible responses including shrinking home ranges (fission response), increasing range overlap (fusion) and incorporation of multiple patches in the home range (expansion response) as fragmentation increases. We studied space use and social organization in a metapopulation of red squirrels (Sciurus vulgaris) in 15 woodland fragments differing in size and tree species composition. Home ranges and core areas of males were larger than females, and fragmentation had different and complex effects on the spacing pattern of both sexes. In food-supplemented patches, high densities led to increased intra-sexual overlap. In linear-shaped patches, squirrels used smaller home ranges and core areas and had lower male–male and male–female overlap levels, independent of patch quality or size. Home range and core area size of males increased with patch size, and male core areas overlapped extensively those of other males and females. Hence males seemed to show a fission response only in some patches. In contrast, home range and core area size of females was not related with patch size, but decreased with habitat quality, supporting predictions of a fusion response and intra-sexual defense of food-based core areas. Hence, where patch size and shape strongly affected space use of male red squirrels, social organization of females was only affected in small, food-supplemented patches, suggesting that the basic spatio-social organization of adult females is very resistant to fragmentation.     

What determines the distribution of a flightless bush-cricket (<Emphasis Type="Italic">Metrioptera brachyptera</Emphasis>) in a fragmented landscape?

Based on metapopulation theory, isolation, patch size and habitat quality within patches have recently been identified as the most critical parameters determining the persistence of species. In the special case of flightless and sedentary Orthoptera species, taking into account the low dispersal ability, species survival probably depends more on habitat quality than on isolation. The aim of this study was to document how landscape (patch size, isolation and climate) and microhabitat (vegetation structure, microclimate and land use) factors influence patch occupancy and population densities, respectively, of a flightless bush-cricket (Metrioptera brachyptera) in fragmented calcareous grasslands. In summer 2005 patch occupancy of M. brachyptera was assessed in 68 calcareous grassland patches of the Diemel Valley (central Germany). Among these, 26 patches with 80 plots were selected to characterise M. brachyptera habitats in detail. On each plot, bush-cricket density was sampled in an area of 20 m² using a 0.5 m² box quadrat. At the landscape level (patches) in 46 (68%) of 68 studied calcareous grassland patches M. brachyptera was present. Patch occupancy increased with annual precipitation and patch size but was independent of altitude, annual temperature and isolation. At the microhabitat level (plots), population density of M. brachyptera decreased with land-use intensity and increased with vegetation height. In addition, a high litter accumulation was adverse for M. brachyptera. Given the low explanatory power of isolation for patch occupancy, conservation of flightless and sedentary insects, such as M. brachyptera, should primarily focus on improving habitat quality. For M. brachyptera and other stenotopic calcareous grassland species we therefore recommend traditional rough grazing with sheep, which creates a heterogenous habitat structure and avoids the accumulation of too much litter.     

Landscape configuration determines gene flow and phenotype in a flightless forest-edge ground-dwelling bush-cricket, Pholidoptera griseoaptera

Spatial configuration of habitats influences genetic structure and population fitness whereas it affects mainly species with limited dispersal ability. To reveal how habitat fragmentation determines dispersal and dispersal-related morphology in a ground-dispersing insect species we used a bush-cricket (Pholidoptera griseoaptera) which is associated with forest-edge habitat. We analysed spatial genetic patterns together with variability of the phenotype in two forested landscapes with different levels of fragmentation. While spatial configuration of forest habitats did not negatively affect genetic characteristics related to the fitness of sampled populations, genetic differentiation was found higher among populations from an extensive forest. Compared to an agricultural matrix between forest patches, the matrix of extensive forest had lower permeability and posed barriers for the dispersal of this species. Landscape configuration significantly affected also morphological traits that are supposed to account for species dispersal potential; individuals from fragmented forest patches had longer hind femurs and a higher femur to pronotum ratio. This result suggests that selection pressure act differently on populations from both landscape types since dispersal-related morphology was related to the level of habitat fragmentation. Thus observed patterns may be explained as plastic according to the level of landscape configuration; while anthropogenic fragmentation of habitats for this species can lead to homogenization of spatial genetic structure.     

Overwintering ability and habitat preference of <Emphasis Type="Italic">Morimus asper</Emphasis>: a two-year mark-recapture study with implications for conservation and forest management

Morimus asper is a saproxylic longhorn beetle associated with mature forests. Its flightless condition makes its colonization of new trees in fragmented areas difficult. Our 2-year mark-recapture study revealed new information about the survival ability, population dynamics and habitat preference of M. asper in three beech forests of central Italy. Daily surveys were performed from May to July in 2013 and 2014, inspecting suitable trees for hosting the species. A low percentage of overwintered adults was observed for both sexes, with a very long lifespan: 282–409 days. Almost all individuals were recaptured on the tree of their first capture, and dispersal (20–451 m) was recorded only in thirteen individuals. Adult phenology showed two peaks of activity (middle of May and middle of June). Population estimates varied significantly according to site and year. Mean daily temperature affected recapture probability and total captures (optimal range of 15–26?°C). The species showed preference for huge lying trees, branches on the ground, a low percentage of debarked surface and high canopy closure. M. asper showed a high survival probability, but the few movements observed, combined with its flightless condition, suggest strongly that this species has a low dispersal ability, highly threatened by local fragmentation. Furthermore, almost all captures were made on the same tree, making this a “key tree” for population viability. Forest management techniques should retain many lying trees, abundant coarse woody debris and a dense canopy that ensures a ‘cooler’ temperature in the understory, favouring M. asper and its conservation.     

Spatial ecology of host–parasitoid interactions: a threatened butterfly and its specialised parasitoid

Habitat conservation for threatened temperate insect species is often guided by one of two paradigms: a metapopulation approach focusing on patch area, isolation and number; or a habitat approach focusing on maintaining high quality habitat for the focal species. Recent research has identified the additive and interacting importance of both approaches for maintaining populations of threatened butterflies. For specialised host-parasitoid interactions, understanding the consequences of habitat characteristics for the interacting species is important, because (1) specialised parasitoids are particularly vulnerable to the consequences of fragmentation, and (2) altered interaction frequencies resulting from changes to habitat management or the spatial configuration of habitat are likely to have consequences for host dynamics. The spatial ecology of Cotesia bignellii, a specialist parasitoid of the threatened butterfly Euphydryas aurinia, was investigated at two spatial scales: within habitat patches (at the scale of individual aggregations of larvae, or ‘webs’) and among habitat patches (the scale of local populations). Parasitism rates were investigated in relation to larval web size, vegetation sward height and host density. Within patches, the probability of a larval webs being parasitized increased significantly with increasing number of larvae in the web, and parasitism rates increased significantly with increasing web isolation. The proportion of webs parasitized was significantly and negatively correlated with cluster density. Among habitat patches the proportion of parasitized webs decreased as cluster density increased. Clusters with a high proportion of larval webs parasitized tended to have lower parasitism rates per larval web. These results support the call for relatively large and continuous habitat patches to maintain stable parasitoid and host populations. Conservation efforts directed towards maintenance of high host plant density could allow E. aurinia to reduce parasitism risk, while providing C. bignellii with sufficient larval webs to allow population persistence.     

Flightless insects: a test case for historical relationships of African mountains

Flightless insects give a clearer view of former distribution of montane habitat in Africa compared with highly mobile animals as birds and butterflies because passive long distance transport and long distance dispersal can be discounted. Only a few species in the twenty-one genera under study are shared between neighbouring mountains which can be explained in all cases by a Pleistocene lowering of the montane habitat by 850 m. Therefore a montane forest cover connecting the mountains at colder times as suggested by the pluvial theory can be refuted which is in correspondence with palynological findings suggesting a dry corridor between the mountains. No montane refuge for flightless insects can be identified, because the most species-rich mountain of a genus differs among the genera under study. Instead, each mountain served as a species refuge with a stable habitat. The requirement of a smaller habitat compared to vertebrates is indicated by endemic species on each single mountain suggesting pre-Pleistocene speciation which results even in endemic genera to one mountain. Different small patches of suitable habitat on one mountain could also explain the radiations found in some genera of flightless insects. In some genera species are lacking on Mt Kenya which indicates—with the findings of no endemic passerine bird on the mountain—a probably very dry condition during colder times. On Mt Cameroon no species of the flightless insect genera occurring on the Eastern mountains are found. This contrasts with the existing patterns of birds, grasses and butterflies.     

Modelling mating success of saproxylic beetles in relation to search behaviour, population density and substrate abundance

We compared the efficiency of two mate-finding strategies exploited by representatives of the beetle families Cisidae and Anobiidae (genus Dorcatoma) that live inside fruiting bodies of wood-decaying fungi. In the Cisidae both sexes are attracted to host odour, but no pheromones seem to be present (nonpheromone strategy). In the Dorcatoma species only the females are attracted to host odour, but having found a host they attract males with a sexual pheromone (pheromone strategy). With a simulation model, we compared the efficiency of the two strategies at four densities of trees hosting fungal fruiting bodies and at three relative densities of insects. We found only small differences in efficiency between the two strategies at high relative densities of conspecific individuals, regardless of host tree density. The pheromone strategy was relatively more efficient when the relative density of insects or the density of host trees decreased. Thus, species adopting the nonpheromone strategy are probably more sensitive to habitat fragmentation and more likely to decline and go extinct at low population densities (because of Allee effects) than species using the pheromone strategy. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Sex-specific indicators of landscape use by servals: Consequences of living in fragmented landscapes

The conversion of wetlands and its associated habitat for farming, residential development and commercial purposes has led to many small disconnected patches of native vegetation surrounded by generally inhospitable human altered land uses. Such human interventions pose a serious threat to the survival of wetland dependent indicator species such as the serval (Leptailurus serval) in the Drakensberg Midlands of KwaZulu-Natal, South Africa. To address the effects of habitat fragmentation on serval space use we used GPS fixes of collared individuals for 100 days between May 2013 and January 2014. We tracked five females and eleven male servals with GPS-UHF collars. Fragmentation indices at the class level (wetland, forest with bushland, grassland and cropland) were measured within the collared serval's minimum convex polygon area (MCP) of home range. Serval use points and fragmentation indices were extracted to each sub-landscape unit of 2 km² falling within the MCP home range. The response of serval population to fragmentation indices was analyzed using generalized linear models at three levels: male, female and the overall population. We found that core area of wetland positively explained landscape use by servals. Effects of forest core area, forest proximity and patch richness were important for landscape use by male servals. Male and female serval use declined with increase in complex shapes of forest and grassland, wetland clumpiness for females and overall, and cropland patches for servals overall. Our results showed that wetland is a key determinant for the survival of male and female servals in fragmented landscapes therefore effective conservation of serval population demands adequate viable native habitat.     

Spatial genetic analysis of the grass snake,Natrix natrix (Squamata: Colubridae), in an intensively used agricultural landscape

Both the conversion of natural habitats to farmland and efforts at increasing the yield of existing crops contribute to a decline in biodiversity. As a consequence of land conversion, specialised species are restricted to remnants of original habitat patches, which are frequently isolated. This may lead to a genetic differentiation of the subpopulations. We used seven microsatellite markers to examine the genetic population structure of the grass snake, Natrix natrix (Linnaeus, 1758), sampled in remnants of pristine habitat embedded in an intensively used agricultural landscape in north‐western Switzerland. The study area, a former wetland, has been drained and gradually converted into an agricultural plain in the last century, reducing the pristine habitat to approximately 1% of the entire area. The grass snake feeds almost entirely on amphibians, and is therefore associated with wetlands. In Central Europe, the species shows severe decline, most probably as a result of wetland drainage and decrease of amphibian populations. We found no genetically distinct grass snake populations in the study area covering 90 km². This implies that there is an exchange of individuals between small remnants of original habitat. Thus, gene flow may prevent any genetic differentiation of subpopulations distributed over a relatively large area. Our results show that a specialized snake species can persist in an intensively used agricultural landscape, provided that suitable habitat patches are interconnected. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 51–58.     

Population size, pollination and reproductive success in two endangered Genista species

Habitat fragmentation often leads to small and isolated plant populations as well as decreased habitat quality. These processes can fundamentally disrupt the interactions between plants and pollinators and decrease reproductive success. This concerns especially self-incompatible, non-clonal species that depend on pollination for successful reproduction.In two rare and endangered heathland plant species, Genista anglica and G. pilosa, we examined pollination and reproduction in relation to population size. Eight populations of G. anglica and ten populations of G. pilosa were surveyed in the vicinity of Bremen, NW-Germany. We counted the visits of pollinators (honeybees, bumblebees, and other insects) and determined the reproductive output of the observed shoots.Contrary to our expectation to find increased pollinator visitation rates in larger populations of both Genista species, the number of flower-visiting insects was unrelated to the number of flowering shoots. Increasing shoot length had a positive and increasing temperature a negative impact on the number of visiting honeybees and bumblebees. Despite the general absence of population size effects on pollinator numbers, the number of fruits and seeds in G. anglica increased with increasing population size. Fruit and seed set in G. pilosa were negatively related to the number of ‘other insects’. Our field observations showed that larger populations of both Genista species flowered earlier than smaller populations and much earlier than reported in the literature. Flowering in large populations therefore tends to coincide less well with pollinator abundance, and this may cause a disruption of the temporal coincidence between flowering phenology and pollinator activity.     

Assessment of Habitat Fragmentation and Corridors for an Isolated Subspecies of the Sichuan Golden Snub-Nosed Monkey, <Emphasis Type="Italic">Rhinopithecus roxellana hubeiensis</Emphasis>

Understanding habitat quality and landscape connectivity and exploring corridors connecting habitat patches are crucial for conservation, particularly for species distributed among isolated populations. The Sichuan golden snub-nosed monkey, Rhinopithecus roxellana, is an Endangered primate species endemic to mountainous forests in China. Its easternmost distribution lies in the Shennongjia area, which harbors an isolated subspecies, R. roxellana hubeiensis. Unfortunately, it has experienced significant habitat loss, fragmentation, and dramatic population decline in recent decades, primarily due to increased human disturbance. To quantify habitat quality, identify suitable habitat patches, and detect possible linkages among these patches for R. roxellana hubeiensis, we conducted habitat suitability assessments and landscape connectivity analyses in the Shennongjia area based on a set of environmental factors. We created a habitat quality model and a movement cost surface for the Shennongjia area based on a habitat suitability index, graph theory, expert knowledge, field experience, and information from the literature. Our results show that suitable habitat for R. roxellana hubeiensis in Shennongjia is fragmented and limited, and that this is particularly true for highly suitable habitats. We detected six core habitat patches and six least-cost paths and corridors. Our study does not provide accurate distributions of the monkeys and their habitat use. However, it identifies the most feasible and traversable habitats and corridors, which should be conservation priorities for this subspecies, and provides valuable guidance for reevaluating habitat conservation plans.     

A Rapid,Strong, and Convergent Genetic Response to Urban Habitat Fragmentation in Four Divergent and Widespread Vertebrates

Background

Urbanization is a major cause of habitat fragmentation worldwide. Ecological and conservation theory predicts many potential impacts of habitat fragmentation on natural populations, including genetic impacts. Habitat fragmentation by urbanization causes populations of animals and plants to be isolated in patches of suitable habitat that are surrounded by non-native vegetation or severely altered vegetation, asphalt, concrete, and human structures. This can lead to genetic divergence between patches and in turn to decreased genetic diversity within patches through genetic drift and inbreeding.

Methodology/Principal Findings

We examined population genetic patterns using microsatellites in four common vertebrate species, three lizards and one bird, in highly fragmented urban southern California. Despite significant phylogenetic, ecological, and mobility differences between these species, all four showed similar and significant reductions in gene flow over relatively short geographic and temporal scales. For all four species, the greatest genetic divergence was found where development was oldest and most intensive. All four animals also showed significant reduction in gene flow associated with intervening roads and freeways, the degree of patch isolation, and the time since isolation.

Conclusions/Significance

Despite wide acceptance of the idea in principle, evidence of significant population genetic changes associated with fragmentation at small spatial and temporal scales has been rare, even in smaller terrestrial vertebrates, and especially for birds. Given the striking pattern of similar and rapid effects across four common and widespread species, including a volant bird, intense urbanization may represent the most severe form of fragmentation, with minimal effective movement through the urban matrix.     

At the landscape level,birds respond strongly to habitat amount but weakly to fragmentation

Aim

It is usually thought that habitat fragmentation acts negatively on species survival, and consequently, on biodiversity. Recent literature challenges whether habitat fragmentation per se affects species richness, beyond the effect of habitat area. Theoretical studies have suggested that fragmentation may matter most when the amount of available habitat is small or at intermediate levels. However, a recent review suggests that the effect of fragmentation on species richness is usually positive. Here, we dissect the richness–fragmentation relationship. What is the effect size? Does it depend upon the amount of habitat cover? How do individual species respond to fragmentation?

Methods

Applying a macroecological approach, we empirically related avian richness and the probability of occurrence (p_occ) of individual species to fragmentation (number of patches), after controlling for habitat amount in 991 landscapes, each 100‐km², in southern Ontario, Canada.

Results

Species richness was strongly related to total habitat amount, but habitat fragmentation had no detectable additional effect. Individual species’ p_occ related strongly to habitat amount. For some species, p_occ also related secondarily to habitat fragmentation within landscapes. Logistic models revealed that p_occ related significantly negatively to fragmentation after controlling for habitat amount for only ~13% of forest‐ and 18% of open‐habitat species bird species. However, p_occ related significantly positively to fragmentation for even greater proportions of species, including some red‐listed species. Fragmentation effects were not stronger at low or intermediate levels of habitat amount within landscapes.

Conclusion

In earlier studies, negative effects of isolation were observed at the patch level in experimental manipulations. However, at the landscape level, avian species richness in southern Ontario apparently responds primarily to habitat amount and negligibly to fragmentation. We argue that the evidence is inconsistent with the hypothesis that reducing habitat fragmentation per se would be an effective conservation strategy for birds at the landscape level.

     

Landscape genetics of a recent population extirpation in a burnet moth species

The intensification of agricultural land use over wide parts of Europe has led to the decline of semi-natural habitats, such as extensively used meadows, with those that remain often being small and isolated. These rapid changes in land use during recent decades have strongly affected populations inhabiting these ecosystems. Increasing habitat deterioration and declining permeability of the surrounding landscape matrix disrupt the gene flow within metapopulations. The burnet moth species Zygaena loti has suffered strongly from recent habitat fragmentation, as reflected by its declining abundance. We have studied its population genetic structure and found a high level of genetic diversity in some of the populations analysed, while others display low genetic diversity and a lack of heterozygosity. Zygaena loti was formerly highly abundant in meadows and along the skirts of forests. However, the species is currently restricted to isolated habitat remnants, which is reflected by the high genetic divergence among populations (F _ST: 0.136). Species distribution modelling as well as the spatial examination of panmictic clusters within the study area strongly support a scattered population structure for this species. We suggest that populations with a high level of genetic diversity still represent the former genetic structure of interconnected populations, while populations with low numbers of alleles, high F _IS values, and a lack of heterozygosity display the negative effects of reduced interconnectivity. A continuous exchange of individuals is necessary to maintain high genetic variability. Based on these results, we draw the general conclusion that more common taxa with originally large population networks and high genetic diversity suffer stronger from sudden habitat fragmentation than highly specialised species with lower genetic diversity which have persisted in isolated patches for long periods of time.     

Strong genetic differentiation on a fragmentation gradient among populations of the heterocarpic annual Catananche lutea L. (Asteraceae)

In landscapes which are predominately characterised by agriculture, natural ecosystems are often reduced to a mosaic of scattered patches of natural vegetation. Species with formerly connected distribution ranges now have restricted gene flow among populations. This has isolating effects upon population structure, because species are often confined by their limited dispersal capabilities. In this study, we test the effects of habitat fragmentation, precipitation, and isolation of populations on the genetic structure (AFLP) and fitness of the Asteraceae Catananche lutea. Our study area is an agro-dominated ecosystem in the desert–Mediterranean transition zone of the Southern Judea Lowlands in Israel. Our analysis revealed an intermediate level of intra-population genetic diversity across the study site with reduced genetic diversity on smaller scale. Although the size of the whole study area was relatively small (20?×?45?km), we found isolation by distance to be effective. We detected a high level of genetic differentiation among populations but genetic structure did not reflect spatial patterns. Population genetic diversity was correlated neither with position along the precipitation gradient nor with different seed types or other plant fitness variables in C. lutea.     

The Implications of Habitat Management on the Population Viability of the Endangered Ohlone Tiger Beetle (Cicindela ohlone) Metapopulation

Despite their role in providing ecosystem services, insects remain overlooked in conservation planning, and insect management approaches often lack a rigorous scientific basis. The endangered Ohlone tiger beetle (Cicindela ohlone) occurs in a 24-km² area in Santa Cruz County, California. The once larger metapopulation now consists of subpopulations inhabiting five patches of coastal prairie where it depends on bare ground for mating, foraging, and oviposition. Human activities have eliminated natural disturbances and spread invasive grasses, reducing C. ohlone''s bare-ground habitat. Management actions to restore critical beetle habitat consist of cattle and horse grazing, maintaining slow bicycle speeds on occupied public trails, and artificial creation of bare-ground plots. Recreational biking trails help maintain bare ground, but can cause beetle mortality if left unregulated. We tracked C. ohlone survivorship and estimated fecundity for three years. We then constructed a stage-structured population projection matrix model to estimate population viability among the five patches, and to evaluate the success of management interventions. We demonstrate that habitat creation, regulation of bicycle speed, and migration between patches increase C. ohlone survival and population viability. Our results can be directly applied to management actions for conservation outcomes that will reduce species extinction risk and promote recolonization of extirpated patches.     

Habitat connectivity, more than species’ biology, influences genetic differentiation in a habitat specialist, the short-eared rock-wallaby (Petrogale brachyotis)

It is difficult to assess the relative influence of anthropogenic processes (e.g., habitat fragmentation) versus species’ biology on the level of genetic differentiation among populations when species are restricted in their distribution to fragmented habitats. This issue is particularly problematic for Australian rock-wallabies (Petrogale sp.), where most previous studies have examined threatened species in anthropogenically fragmented habitats. The short-eared rock-wallaby (Petrogale brachyotis) provides an opportunity to assess natural population structure and gene flow in relatively continuous habitat across north-western Australia. This region has reported widespread declines in small-to-medium sized mammals, making data regarding the influence of habitat connectivity on genetic diversity important for broad-scale management. Using non-invasive and standard methods, 12 microsatellite loci and mitochondrial DNA were compared to examine patterns of population structure and dispersal among populations of P. brachyotis in the Kimberley, Western Australia. Low genetic differentiation was detected between populations separated by up to 67?km. The inferred genetic connectivity of these populations suggests that in suitable habitat P. brachyotis can potentially disperse far greater distances than previously reported for rock-wallabies in more fragmented habitat. Like other Petrogale species male-biased dispersal was detected. These findings suggest that a complete understanding of population biology may not be achieved solely by the study of fragmented populations in disturbed environments and that management strategies may need to draw on studies of populations (or related species) in undisturbed areas of contiguous habitat.     

Conservation of remnant populations of Colchicum autumnale – The relative importance of local habitat quality and habitat fragmentation

Semi-natural habitat is extremely vulnerable to habitat fragmentation and degradation since its socio-economic value has decreased substantially during the last century in most parts of Europe. We evaluated the relative effects of habitat fragmentation and local environmental conditions on population structure and reproductive performance of the long-lived corm geophyte Colchicum autumnale in 17 highly fragmented populations. Habitat isolation did not affect patch occupancy, population structure or plant performance. In contrast, population size and local environment strongly affected population structure and reproductive performance. Densities of all life stages increased with increasing population size. Large populations also showed a higher reproductive performance and a larger proportion of new recruits. Relationships with local growth conditions pointed towards the importance of an open grassland sward for flower and fruit set and the presence of microsites for successful sexual recruitment. These results suggest that the distribution of C. autumnale consists of an assemblage of basically unconnected populations that are remnants of formerly larger populations. This is in accordance with the species' ability to grow clonally, allowing long-term persistence under deteriorating conditions that occurred during a long period of habitat fragmentation. In conclusion, our results indicate that local habitat and population size are more important than habitat fragmentation (i.e. calcareous grassland isolation and surface area) and argue in favour of a management that is primarily focused on local habitat restoration. This is preferentially accomplished by reintroducing grazing practices, complemented by regular setback of spontaneous succession towards forest.