Levels Of Habitat Fragmentation Research Articles

The future of plant diversity within a Mediterranean endemism centre: Modelling the synergistic effects of climate and land-use change in Peloponnese, Greece

Climate- and land-use change stand as primary threats to terrestrial biodiversity. Yet, their synergistic impacts on species distributions remain poorly understood. To address this knowledge gap, we conducted the first-ever comprehensive species distribution analysis on an entire regional endemism centre within an eastern Mediterranean country, incorporating dynamic land-use/land-cover change data together with climate change scenarios. Specifically, we apply species distribution modelling and spatial data analysis techniques to compare the individual and synergistic effects of these environmental drivers on the endemic vascular flora of Peloponnese, focusing on potential range contractions, altitudinal shifts, and habitat fragmentation levels. Moreover, we identify fine-scale present and potential future endemism hotspots within our study area, incorporating taxonomic and phylogenetic information. Overall, we aim to enhance our current understanding of endemism patterns and contribute to the development of future-proof conservation strategies for safeguarding Greece's endangered endemic flora. The integration of land-use change projections with climate change yielded less severe impacts compared to the effects anticipated when considering climatic variables alone. Most taxa are expected to undergo significant range declines and nearly half might experience increased habitat fragmentation, due to the synergistic effects of climate- and land-use change. We identified endemism hotspots, which are concentrated in or along the main Peloponnesian mountain massifs. However, our predictions indicate that areas presently recognized as endemism hotspots will undergo a concerning area decline, across all future scenarios considered in this study. Our findings highlight the importance of including dynamic land-use variables alongside climatic predictors when projecting species distributions under global change. Moreover, we showed that endemism hotspots are not static and considering their potential geographic shifts is paramount to delineate effective forward-looking conservation strategies.

Food availability, plant diversity, and vegetation structure drive behavioral and ecological variation in Endangered Coimbra-Filho's titi monkeys.

There is wide variability in primate behavior and ecology. Understanding how frugivorous primates behave under different habitat fragmentation levels is key for effective conservation and management of species and their habitats. We evaluated the seasonality in activity budget, diet, and ranging behavior of two groups of Endangered Coimbra-Filho's titi monkeys (Callicebus coimbrai). One group inhabited a 14-ha forest fragment, whereas the other lived in a 522-ha fragment. We measured the monthly density of trees and lianas available as food sources over 8 months. We also collected behavioral and group location data every 5 min, from dawn to dusk, using the scan sampling method. The two forest fragments differed seasonally in the number of fruiting food-resource available. In the 14-ha fragment, we found that the time spent by titi monkeys feeding, foraging, resting, and traveling differed seasonally. In the 522-ha fragment, titi monkeys exhibited seasonal differences in time spent sleeping, socializing, foraging, and revisiting food sources. In both titi monkey groups, diets varied seasonally. Our findings indicate that Coimbra-Filho's titi monkeys can exhibit behavioral flexibility in their activity budgets, diets, and movement patterns. Such flexibility is important for this species to survive in fragmented habitats and may be linked to three key factors: species-specific resource availability, plant species diversity, and the vegetation structure of each forest fragment.

Fine-scale spatial genetic structure, mating, and gene dispersal patterns in Parkia biglobosa populations with different levels of habitat fragmentation.

PremiseA good understanding of genetic variation and gene dispersal in tree populations is crucial for their sustainable management, particularly in a context of rapid environmental changes. West African Sudanian savannahs are being fragmented and degraded, partly due to expansion of crop cultivation and monocultures that reduce tree density and may impact pollinators. The population dynamics of important indigenous trees could also be affected. We investigated the influence of habitat fragmentation on patterns of genetic diversity and gene dispersal of a key Sudanian agroforestry tree species, Parkia biglobosa.MethodsUsing 10 highly polymorphic nuclear microsatellites, we genotyped 2475 samples from reproductive trees, seedlings, and embryos in four tree populations presenting different levels of habitat fragmentation.Results Parkia biglobosa presented similar high genetic diversity across the four populations studied. Genetic diversity and inbreeding were similar between adults and embryo cohorts. In all four populations, the selfing rate was less than 1%. The effective number of pollen donors per tree was high (N EP~ 18–22), as was the pollen immigration rate (from 34 to 74%). Pollen dispersal was characterized by a fat‐tailed distribution with mean estimates exceeding 200 m. In three populations, stem diameter had a pronounced effect on male reproductive success. Here, the highest male reproductive success was observed in trees with a diameter at breast height between 60 and 75 cm.ConclusionsAt the scale analyzed, fragmentation does not seem to pose limitations to gene flow in any of the sites investigated, regardless of the landscape configuration associated with the different tree stands. The study provides useful insights on the reproductive biology of an important tree species in the West African savannahs.

Ranging behavior of European rabbits (Oryctolagus cuniculus) in urban and suburban landscapes

Various mammals, particularly carnivores, reportedly establish smaller home ranges in urban compared with rural areas. This may be because urban environments provide optimal resources within a small area, negating the requirement to range further, or because habitat fragmentation constrains ranging behavior. Comparable information on urban populations of herbivorous mammalian species (such as European rabbits) is scarce. To fill this knowledge gap, we radio-tracked 13 individuals (seven females and six males) equipped with radio collars in a suburban and an urban study site in the city of Frankfurt am Main in Germany during the reproductive season (March to September) of 2012. The study sites differed in levels of habitat fragmentation. We report the smallest home ranges ever described for this species, with mean 95% minimum convex polygons (MCPs) covering 0.50 ha, while no consistent differences between sites were uncovered. We occasionally tracked individuals crossing streets underground (in burrows), suggesting that streets may restrict the ranging behavior of rabbits—and possibly other burrowing species—to a much lesser extent than previously thought. We conclude that heterogeneous landscape structures, made up of a diverse mosaic of buildings, parks, and gardens, provide sufficient food and shelter in close proximity to burrows at both study sites. Therefore, our data support the hypothesis that optimal resources constrain ranges in this case rather than habitat fragmentation.

Habitat fragmentation and eradication of invading insect herbivores

Abstract Invasions by non‐native pests and diseases represent serious threats to biodiversity, agriculture and human health. Under current border arrival rates associated with international trade not all such invasions can be prevented, so early detection and eradication (forced extinction) are important strategies for preventing establishment and long‐term impacts. Removal of host plants has historically been a common tool used alone and in concert with other tools for eradication of plant pests but there is little scientific theory specific to the management of invasive species to guide the application of this eradication strategy. We drew upon extensive conservation biology literature documenting the effect of habitat destruction or fragmentation driving extinction. We applied a previously developed spatially explicit model of gypsy moth, Lymantria dispar, spatial dynamics to explore how fragmentation affects population persistence. This model accounts for a component Allee effect driven by mate‐finding failure that interacts with dispersal. We observed a nonlinear dependency of population persistence on the fraction of habitat cover and the level of habitat fragmentation. Simulation of active habitat fragmentation via the removal of habitat in swaths of varying widths or the application of pesticide in varying swaths showed that removal of hosts or pesticide application in narrow swaths (i.e. 40 m wide) caused the greatest probabilities of extinction. Generally, habitat removal was more effective than one‐off pesticide treatments at causing extinction. Synthesis and applications. Spatially explicit modelling of Allee dynamics in invading gypsy moth populations showed that host removal can be an effective method to eradicate invasive plant‐feeding insects especially when habitat fragmentation is applied at a desirable level. Furthermore, this can be used as an alternative to, or in conjunction with, pesticide treatments, to provide more options for carrying out eradications and to increase the probability of eradication success.

Movement Patterns of the Eastern Chipmunk (<i>Tamias striatus</i>) in Four Fragmented Landscapes of Prince Edward Island, Canada

The analysis of animal movement patterns can provide important information on animals’ responses to habitat features. In this study, the movement paths of eastern chipmunks (Tamias striatus) were examined in four landscapes, with different levels of habitat fragmentation, using either fluorescent powdering or spool-and-line tracking. Descriptions of the tree and ground vegetation communities were performed in the vicinity of the trail to obtain information on habitat use and habitat selection. Several key movement variables were calculated, including the total path length, net distance, fractal dimension, and radius of gyration. Despite statistically significant differences in some of the movement metrics between the four landscapes, the overall movement patterns were generically the same for all of chipmunk paths examined in this study. The data were compared to trends expected based on random or correlated random walks, as well as Lévy-walk models. The mean squared net displacement did not support the correlated random walk predictions, except at smaller spatial scales, but overall demonstrated Lévy-like super diffusive behaviour. Lévy-like patterns were also confirmed from the move-length distributions that demonstrated truncated-tail power-law behaviour. Although this would suggest invariance of the movement patterns at all spatial scales studied, fractal analysis revealed at least two transitions in movement patterns at scales of around 2 and 5 m. The transition point at 2 m was negatively correlated with the density of small trees, while the transition at ~5 m was positively correlated with the spatial distribution of large trees. As the habitat-preference data showed that small trees are among the least preferred habitat component, while large trees were among the most preferred habitat, chipmunks are likely to alter their movement behaviour to avoid small trees, and attracted towards large trees possibly to avoid predators. Overall, we determined three principal domains of movement: at smaller spatio-temporal scales, foraging activities dominate and the movement is highly correlated but also random; at intermediate spatial scales, chipmunks may be moving to avoid predators, using different environmental cues, and the movement is more directed (but still influenced by vegetation patterns at intermediate scales); at larger spatio-temporal scales, the movement is dominated by long-range/long-term memory and homing to burrows and other key habitat features, such as food caches, drives more directed movement. The fact that scale-dependent movement mechanisms could give rise to LW patterns is consistent with recent studies.

Distribution of the meadow lizard in Europe and its realized ecological niche model

ABSTRACTOne of the most interesting but elusive members of the European herpetofauna is the meadow lizard (Darevskia praticola). It is a small, ground dwelling, predominantly forest living lacertid, for which many ecological and biological data are still missing. Moreover, at least for the western part of the species range (south-eastern Europe) its distribution and environmental associations are insufficiently known, likely due to difficulties in detection even with intensive field sampling. Here, we complemented the available literature records with our personal observations and explored the effects of environmental factors shaping the species ecological niche and distribution in Europe using the ecological niche modelling approach from Maxent software. The new records of the meadow lizard fill a gap in its known distribution. The most suitable habitats are in central and eastern Serbia, south-western Romania, and central, southern and south-western Bulgaria. Mean temperature of the coldest quarter, vegetation and slope had the strongest effect in defining the meadow lizard’s ecological niche. Niche suitability increased with the increase in forest cover and slope, while the temperature showed a bell-shaped response with a rather narrow tolerance range for temperature. Contrary to expectations, precipitation seemed to have no contribution to the species occurrence. Ecological niche model performance increased with a higher resolution of predictor variables despite the lower number of available occurrence records, although the slope variable had a greater predictive power when calculated at a lower resolution. Interestingly, high resolution vegetation variables (30 m) were able to show some level of habitat fragmentation, which likely resulted from deforestation. Overall, our results epitomize the effects of limited sampling on the biogeography inference of elusive species while having significant repercussions on conservation priorities and management of the species.

Interspecific variation in ploidy as a key plant trait outlining local extinction risks and community patterns in fragmented landscapes

Abstract Polyploidy is associated with a plethora of phenotypic and genetic changes yielding transformative effects on species' life‐history and ecology. These biological attributes can contribute to the success of species on ecological timescales, as observed in the invasion success or rapid environmental and climatic adaptation of polyploids. However, to date there has been a distinct lack of empirical evidence linking species' local extinction risk, species distributions and community structure in fragmented landscapes with interspecific variation in ploidy. We aimed to investigate the relationship between levels of habitat fragmentation and patterns in both diversity and the frequency of species with different ploidy levels. We included additional persistence‐ and dispersal related life‐history traits, to establish the relative importance of ploidy in determining species richness and frequencies following habitat fragmentation. We therefore collected plant community presence‐absence data and landscape data from grassland fragments from south‐central Sweden. Community‐level analysis uncovered that interspecific variation in ploidy proved the strongest predictor of plant community species richness and turn‐over across grassland fragments. Local extinction risk decreased as ploidy increased, with diploids most prone to local extinction. In the species‐level analysis, ploidy outweighed the combined explanatory power of commonly used life‐history traits such as clonality, dispersal mechanism and mating system; key predictors of plant species distributions across fragmented landscapes. Ploidy appears to capture parallel variation in a series of advantageous genetic and life‐history mechanisms which operate on ecological timescales, emerging as the strongest predictor of local extinction risk even after accounting for variation in other crucial life‐history traits. Our results therefore highlight the importance of genomic traits such as ploidy and total chromosome number as valuable factors explaining and predicting local extinction risk in fragmented landscapes. A plain language summary is available for this article.

Testing time-geographic density estimation for home range analysis using an agent-based model of animal movement

ABSTRACTTime-geographic density estimation (TGDE) is a method of movement pattern analysis that generates a continuous intensity surface from a set of tracking data. TGDE has recently been proposed as a method of animal home range estimation, where the goal is to delineate the spatial extents that an animal occupies. This paper tests TGDE’s effectiveness as a home range estimator using simulated movement data. First, an agent-based model is used to simulate tracking data under 16 movement scenarios representing a variety of animal life history traits (habitat preferences, homing behaviour, mobility) and habitat configurations (levels of habitat fragmentation). Second, the accuracy of TGDE is evaluated for four temporal sampling frequencies using three adaptive velocity parameters for 30 sample data sets from each scenario. Third, TGDE accuracy is compared to two other common home range estimation methods, kernel density estimation (KDE) and characteristic hull polygons (CHP). The results demonstrate that TGDE is the most effective at estimating core areas, home ranges and total areas at high sampling frequencies, while CHP performs better at low sampling frequencies. KDE was ineffective across all scenarios explored.

Level of habitat fragmentation determines its non-linear relationships with plant species richness, frequency and density at desertified grasslands in Inner Mongolia, China

Level of habitat fragmentation determines its non-linear relationships with plant species richness, frequency and density at desertified grasslands in Inner Mongolia, China

Assessing habitat fragmentation of the KwaZulu-Natal Sandstone Sourveld, a threatened ecosystem

Background: The KwaZulu-Natal Sandstone Sourveld (KZN SS) is a grassland ecosystem categorised as endangered by the terms of the National Environmental Management: Biodiversity Act (Act 10 of 2004). Pressure from urbanisation has led to the remaining areas of the KZN SS being physically fragmented, causing low connectivity levels which have diminished the biological persistence of this ecosystem.Objectives: This study aimed to quantify the overall level of habitat fragmentation of the KZN SS and determine the level of connectivity within the ecosystem, and patches of the KZN SS occurring in the eThekwini Municipal area. Using graph theory, we compared the effectiveness of broad-scale and fine-scale data sets in quantifying habitat fragmentation.Methods: The Conefor Sensinode software, which employs the bases of graph theory, was chosen to aid in assessing fragmentation levels. The integral index of connectivity (IIC) (values range from 0 to 1, with 1 highlighting optimal connectivity) was chosen as the best index to determine landscape connectivity.Results: The KZN SS was shown to be highly fragmented, especially at dispersal distances less than 500 m. This resulted in very low connectivity levels, with the highest IIC value recorded at 0.0063. Moreover, the use of either fine-scale or broad-scale data to measure connectivity differed substantially at 1000 m.Conclusion: Broad-scale data were shown to overestimate habitat fragmentation and underestimate landscape connectivity. A more apt description of KZN SS connectivity levels was realised with fine-scale data. This study recommends that crucial KZN SS patches be prioritised to safeguard this endangered ecosystem.

Flight Morphology, Compound Eye Structure and Dispersal in the Bog and the Cranberry Fritillary Butterflies: An Inter- and Intraspecific Comparison.

Understanding dispersal is of prime importance in conservation and population biology. Individual traits related to motion and navigation during dispersal may differ: (1) among species differing in habitat distribution, which in turn, may lead to interspecific differences in the potential for and costs of dispersal, (2) among populations of a species that experiences different levels of habitat fragmentation; (3) among individuals differing in their dispersal strategy and (4) between the sexes due to sexual differences in behaviour and dispersal tendencies. In butterflies, the visual system plays a central role in dispersal, but exactly how the visual system is related to dispersal has received far less attention than flight morphology. We studied two butterfly species to explore the relationships between flight and eye morphology, and dispersal. We predicted interspecific, intraspecific and intersexual differences for both flight and eye morphology relative to i) species-specific habitat distribution, ii) variation in dispersal strategy within each species and iii) behavioural differences between sexes. However, we did not investigate for potential population differences. We found: (1) sexual differences that presumably reflect different demands on both male and female visual and flight systems, (2) a higher wing loading (i.e. a proxy for flight performance), larger eyes and larger facet sizes in the frontal and lateral region of the eye (i.e. better navigation capacities) in the species inhabiting naturally fragmented habitat compared to the species inhabiting rather continuous habitat, and (3) larger facets in the frontal region in dispersers compared to residents within a species. Hence, dispersers may have similar locomotory capacity but potentially better navigation capacity. Dispersal ecology and evolution have attracted much attention, but there are still significant gaps in our understanding of the mechanisms of dispersal. Unfortunately, for many species we lack detailed information on the role of behavioural, morphological and physiological traits for dispersal. Our novel study supports the existence of inter- and intra-specific evolutionary responses in both motion and navigation capacities (i.e. flight and eye morphology) linked to dispersal.

To what extent could edge effects and habitat fragmentation diminish the potential benefits of land sparing?

Land sharing and land sparing are contrasting proposals for minimising the impacts of agriculture on wild species. Edge effects (biophysical gradients near habitat boundaries) might reduce population sizes on spared land, particularly in highly-fragmented landscapes, so might change conclusions about whether land sparing or land sharing is better for species' persistence. We assessed this possibility by modelling the population sizes of 120 Ghanaian bird species in the presence of a range of hypothetical edge effects under land-sparing and land-sharing strategies, and at different levels of habitat fragmentation and agricultural production. We found that edge effects can reduce population densities on spared land, and in highly-fragmented landscapes can – at modest levels of agricultural production combined with high edge penetration distances – cause the optimal strategy to switch from land sparing to land sharing. Nevertheless, land sparing maximised population sizes for more species in most cases tested. This conclusion was best supported for sensitive species with small global geographical ranges, which are likely to include those of greatest future conservation concern. The size of patches of spared land affected conservation outcomes: population sizes were maximised under a land-sparing strategy that spared large blocks of natural habitat of ~1000 or, better, ~10,000ha. To effect land sparing in practice would require policies that promoted both increases in agricultural yield and the establishment or protection of natural habitats on spared land. Because the optimum scale of patches of spared land for edge-sensitive species is generally larger than the size of individual farms, policies that facilitate coordinated action by farmers or other land managers might be required.

Landscape genetics and genetic structure of the southern torrent salamander, Rhyacotriton variegatus

Landscape genetic methods can be used to identify the most effective conservation measures to maintain functional connectivity among populations. Analyses of habitat factors that facilitate or restrict gene flow are particularly useful for species with specific habitat requirements and low dispersal rates. Rhyacotriton variegatus is a salamander species with low desiccation tolerance and a restricted geographic range, limited to the Pacific Northwest. Thus, we predicted that genetic distance would be positively correlated with climate and landscape variables that increase risk of desiccation. Two genetic distance measures, pairwise FST and proportion of shared alleles (DPS), suggested that gene flow was low among 19 sampling localities (367 total individuals) and genetic structure was high overall (DPS = 0.636 ± 0.010, FST = 0.330 ± 0.011; mean ± SD). Using both least-cost path and Circuitscape models of landscape resistance, we found that low stream cover, low canopy cover, high heat-load index, and short frost-free period all restricted gene flow among populations. We suggest that the conservation status of this species be revisited given this evidence of high genetic structure within the species, the level of habitat fragmentation in their range, and their reliance on dense canopy cover for dispersal. Maintaining stream corridors with buffers of dense canopy cover may maximize connectivity despite the pressures of timber harvest and urbanization.

Spatial pattern of habitat quality modulates population persistence in fragmented landscapes

AbstractHabitat quality is one of the important factors determining population dynamics and persistence, yet few studies have examined the effects of spatial heterogeneity in within‐patch habitat quality. In this paper, we use a spatially explicit agent‐based model to investigate how habitat fragmentation and spatial pattern of within‐patch habitat quality affect population dynamics and long‐term persistence. We simulate three levels of habitat fragmentation (ranges from continuous to highly fragmented) and three types of spatial patterns in habitat quality within patches (i.e., negatively autocorrelated, randomly distributed, and positively autocorrelated). Hypothetical species differ in their niche specialization. The results demonstrate explicitly that the spatial pattern of within‐patch habitat quality plays an important role in modulating the effects of habitat fragmentation on populations. Populations become less variable in size, and experience lower probability of extinction in landscapes with positively autocorrelated within‐patch habitat quality. Specifically, specialized species are more vulnerable to habitat fragmentation, but this vulnerability is greatly mitigated by positively autocorrelated habitat quality within patches, in other words, exhibiting higher resistance to habitat fragmentation. The findings of this study suggest that managing habitat quality in existing habitat remnants is important to preserve species in habitats undergoing fragmentation, particularly for those with specialized habitat requirements.

Habitat restoration will help some functional plant types persist under climate change in fragmented landscapes

AbstractIn the next century, global climate change is predicted to have large influences on species' distributions. Much of the research in this area has focused on predicting the areas where conditions will be suitable for the species in future, and thus the potential distribution of the species. However, it is equally important to predict the relative abilities of species to migrate into new suitable areas as conditions shift, while accounting for dynamic processes, such as dispersal, maturation, mortality, and reproduction, as well as landscape characteristics, such as level of habitat fragmentation and connectivity. In this study, we developed a spatially explicit individual‐based model that addresses these factors. As a motivating case study, we based aspects of the model on southwest Australia, a global biodiversity hotspot, but stress that the results obtained are generalizable beyond this region. Using the model, we enhanced current understanding of climate change impacts by investigating how and to what extent the functional traits of plant species affect their ability to move with climate change across landscapes with various levels of fragmentation. We also tested the efficacy of strategic restoration, such as planting corridors to increase connectivity among fragments. We found that even if the landscape is fully intact, only an average of 34.2% of all simulated functional groups had a good chance of successfully tracking climate change. However, our study highlights the power of strategic restoration as a tool for increasing species persistence. Corridors linking fragments increased species persistence rates by up to 24%. The lowest persistence rates were found for trees, a functional group with high dispersal but also long generation times. Our results indicate that for trees intervention techniques, such as assisted migration might be required to prevent species losses.

Current status of vertebrate diversity in anthropogenic and natural ecosystems in south-western Sri Lanka

Fragmentation of natural habitats is one of the major threats to long term conservation of biodiversity in Sri Lanka. Establishing corridors to link these natural habitat patches is one of the simplest strategies that can be used to address this threat. However, it is not possible to establish forest corridors everywhere and therefore alternate strategies need to be developed. This study was undertaken to test whether agroecosystems could be used as permeable matrices to link natural habitat patches. Four sites with different land use types were selected in the south-western region of Sri Lanka, where the highest level of habitat fragmentation occurs. These four sites represent three agro-ecosystems (tea, rubber and oil palm) and a natural ecosystem. Presence of herpetofauna, birds and large mammals in these four sites were enumerated using the quadrate sampling method (8 x 8 m) for herpetofauna and the line transect method for birds and mammals. At each site, sampling was carried out from September 2002 to November 2004. A total of 187 species of vertebrates were recorded from the four sites. This comprised 53 species of herpetofauna (41 species of reptiles and 12 species of amphibians), 99 species of birds and 35 species of mammals. Overall species richness (178) as well as the species richness of each of the three major taxa studied, namely, herpetofauna (51), birds (97) and mammals (30) were found to be the highest in the natural forest compared to the three agro-ecosystems. The agro-ecosystems were used by a large number of vertebrate species. However, the species assemblage in these agro-ecosystems was dominated by common species and comprised a few species that are threatened or endemic to Sri Lanka, compared to the natural forest. Therefore, it can be concluded that agro-ecosystems are important for maintaining population densities of common species. Further, this study clearly demonstrates the value of natural forests for preservation of threatened and endemic vertebrates. Since agro-ecosystems are not utilized by highly specialized threatened and endemic species, it is unlikely that this type of land use will create a permeable matrix among fragmented natural forests for such species. Keywords : Agro-ecosystems, fragmentation, linking forest fragments, species richness. DOI: http://dx.doi.org/10.4038/jnsfsr.v39i4.3886 J.Natn.Sci.Foundation Sri Lanka 2011 39 (4): 383-389

Effects of current and historic habitat fragmentation on the genetic structure of the sand goby Pomatoschistus minutus (Osteichthys, Gobiidae)

Habitat fragmentation is a major force that will influence the evolution of a species and its distribution range. Pomatoschistus minutus, the sand goby, has a North Atlantic–Mediterranean distribution and shows various level of habitat fragmentation along its geographic repartition. The use of mitochondrial sequences of the cytochrome b (cyt b) gene and two co-dominant sets of nuclear markers (introns and microsatellites) allowed us to describe the relationships between P. minutus populations belonging to several different geographical regions of Europe and to assess the structure of populations inhabiting the Golfe du Lion, along the French Mediterranean coast. The present study confirms that the taxon located in the Adriatic Sea (Venice) should be considered as a distinct species, separated approximately 1.75 Mya. The comparison of P. minutus between the Atlantic and western Mediterranean coasts using polymorphic co-dominant markers revealed that they belong to two demographically independent units, and thus could be considered as well as distinct species, more recently separated (0.3 Mya). The Pleistocene glaciations seem therefore to have played an important role in the diversification of this complex. Finally, at a regional scale in the Golfe du Lion, P. minutus appears to form a single huge homogeneous population.

A meta‐analysis of dispersal in butterflies

Dispersal has recently gained much attention because of its crucial role in the conservation and evolution of species facing major environmental changes such as habitat loss and fragmentation, climate change, and their interactions. Butterflies have long been recognized as ideal model systems for the study of dispersal and a huge amount of data on their ability to disperse has been collected under various conditions. However, no single 'best' method seems to exist leading to the co-occurrence of various approaches to study butterfly mobility, and therefore a high heterogeneity among data on dispersal across this group. Accordingly, we here reviewed the knowledge accumulated on dispersal and mobility in butterflies, to detect general patterns. This meta-analysis specifically addressed two questions. Firstly, do the various methods provide a congruent picture of how dispersal ability is distributed across species? Secondly, is dispersal species-specific? Five sources of data were analysed: multisite mark-recapture experiments, genetic studies, experimental assessments, expert opinions, and transect surveys. We accounted for potential biases due to variation in genetic markers, sample sizes, spatial scales or the level of habitat fragmentation. We showed that the various dispersal estimates generally converged, and that the relative dispersal ability of species could reliably be predicted from their relative vagrancy (records of butterflies outside their normal habitat). Expert opinions gave much less reliable estimates of realized dispersal but instead reflected migration propensity of butterflies. Within-species comparisons showed that genetic estimates were relatively invariable, while other dispersal estimates were highly variable. This latter point questions dispersal as a species-specific, invariant trait.

Two ecologically‐divergent generalist predators have different responses to landscape fragmentation

We conducted three replicated field experiments to test the population response of two ecologically‐divergent wolf spider species (Hogna helluo and Pardosa milvina) to three correlates of landscape fragmentation: area reduction, spatial subdivision, and increased edge to core ratio. We selected these two species because they differ in vagility and habitat selectivity. Hogna helluo is relatively large, averse to disturbed substrata, and has poor colonization abilities. Conversely, Pardosa is small, vagile, and will use barren, disturbed areas. In a test for the effect of area reduction on populations of the two wolf spiders, we destroyed 0%, 20% or 80% of randomly selected habitat islands in replicated experimental landscapes. We found that population densities of Hogna declined significantly, even at the lowest level of area reduction (20%), and that there was an increase in numbers of Pardosa. In a test for the response to an increase in landscape subdivision, we created four levels of habitat fragmentation in replicate plots. We found a significant decline in Hogna populations with increasing fragmentation. Pardosa populations did not respond to the fragmentation. In the third experiment we kept landscape area and subdivision constant, but manipulated the edge‐to‐core ratio. We found that populations of Hogna declined sharply with increasing edge, and that populations of Pardosa did not respond. These two syntopic wolf spiders have distinctly different responses to landscape fragmentation.