Ecological strategies in stable and disturbed environments depend on species specialisation

Ecological strategies are integral to understanding species survival in different environments. However, how habitat specialisation is involved in such strategies is not fully understood, particularly in heterogeneous and disturbed environments. Here, we studied the trait associations between specialisation, dispersal ability, competitiveness, reproductive investment and survival rate in a spatially explicit metacommunity model under various disturbance rates. Though no unique trait values were associated with specialisation, relationships were uncovered depending on environmental factors. We found strong trait associations mainly for generalist species, while specialist species exhibited a larger range of trait combinations. Trait associations were driven first by the disturbance rate and second by species' dispersal ability and generation overlap. With disturbance, low dispersal ability was strongly selected against, for specialists as well as for generalists. Our results demonstrate that habitat specialisation is critical for the emergence of trait strategies in metacommunities and that disturbance in interaction with dispersal ability limits not only the range of trait values but also the type of possible trait associations.     

Responses of 'resistant' vertebrates to habitat loss and fragmentation: the importance of niche breadth and range boundaries

Abstract. An ability to predict species' sensitivities to habitat loss and fragmentation has important conservation implications, and numerous hypotheses have been proposed to explain interspecific differences observed in human-dominated landscapes. We used occupancy data collected on 32 species of vertebrates (16 mammals and 16 amphibians) in an agricultural landscape of Indiana, USA, to compare hypotheses that focus on different causal mechanisms underlying interspecific variation in responses to habitat alteration: (1) body size; (2) morphology and development; (3) behaviour; (4) niche breadth; (5) proximity to range boundary; and multiple-process models combining main effects and interactions of hypotheses (1)–(2) and (4)–(5). The majority of habitat alteration occurred over a century ago and coincided with extinction of several species; thus, our study dealt only with variation in responses of extant species that often are considered 'resistant' to human modifications of native habitat. Corrected Akaike scores and Akaike weights provided strongest support for models incorporating niche breadth and proximity to range boundary. Measures of dietary and habitat breadth obtained from the literature were negatively correlated with sensitivity to habitat alteration. Additionally, greater sensitivity was observed for species occurring at the periphery of their geographical ranges, especially at northern or western margins. Body size, morphological, developmental and behavioural traits were inferior predictors of tolerance to fragmentation for the species and landscape we examined. Our findings reinforce the importance of niche breadth as a predictor of species' responses to habitat alteration. They also highlight the importance of viewing the effects of habitat loss and fragmentation in a landscape within a biogeographical context that considers a species' level of adaptation to local environmental conditions.     

Ecological Predictors of Extinction Risk in the Flora of Lowland England, UK

We used historical and contemporary records to determine the scale of plant extinction in Bedfordshire and Northamptonshire, and to assess whether extinct species share a range of ecological and phytogeographical traits. Since 1700 both counties have lost 94 species (11% of their native floras) with the rate of extinction increasing from 3.8 to 4.8 species per decade in the 19th century to 6–8 species per decade after 1950. The most important predictors of extinction risk were English range size and traits associated with habitat specialisation and competitive ability: poor competitors (i.e. short stress-tolerators) associated with open habitats with very low or high pH and soil moisture (e.g. lowland bogs, dwarf-shrub heath and acid and calcareous grassland) were much more likely to have become extinct in the study region than would have been expected by chance alone. Many of these species have very localised distributions and/or occur at the northern, southern or eastern edges of their range in southern England (i.e. Northern and Oceanic). In contrast, there was no clear or significant relationship between extinction and dispersal ability or reproductive mode. These findings, which parallel national trends, indicate that habitat loss and eutrophication have been the main causes of population extinction in lowland England over the last 300 years. However, more fine-scaled studies are required to assess whether ‘low-level’ stresses, such as habitat fragmentation, climate change and atmospheric pollution, are having additional impacts on populations already severely depleted by habitat loss, as well as to quantify changes in the abundance of more widespread species which are known to have declined over the same period.     

Confounding factors in the detection of species responses to habitat fragmentation

Habitat loss has pervasive and disruptive impacts on biodiversity in habitat remnants. The magnitude of the ecological impacts of habitat loss can be exacerbated by the spatial arrangement -- or fragmentation -- of remaining habitat. Fragmentation per se is a landscape-level phenomenon in which species that survive in habitat remnants are confronted with a modified environment of reduced area, increased isolation and novel ecological boundaries. The implications of this for individual organisms are many and varied, because species with differing life history strategies are differentially affected by habitat fragmentation. Here, we review the extensive literature on species responses to habitat fragmentation, and detail the numerous ways in which confounding factors have either masked the detection, or prevented the manifestation, of predicted fragmentation effects.Large numbers of empirical studies continue to document changes in species richness with decreasing habitat area, with positive, negative and no relationships regularly reported. The debate surrounding such widely contrasting results is beginning to be resolved by findings that the expected positive species-area relationship can be masked by matrix-derived spatial subsidies of resources to fragment-dwelling species and by the invasion of matrix-dwelling species into habitat edges. Significant advances have been made recently in our understanding of how species interactions are altered at habitat edges as a result of these changes. Interestingly, changes in biotic and abiotic parameters at edges also make ecological processes more variable than in habitat interiors. Individuals are more likely to encounter habitat edges in fragments with convoluted shapes, leading to increased turnover and variability in population size than in fragments that are compact in shape. Habitat isolation in both space and time disrupts species distribution patterns, with consequent effects on metapopulation dynamics and the genetic structure of fragment-dwelling populations. Again, the matrix habitat is a strong determinant of fragmentation effects within remnants because of its role in regulating dispersal and dispersal-related mortality, the provision of spatial subsidies and the potential mediation of edge-related microclimatic gradients.We show that confounding factors can mask many fragmentation effects. For instance, there are multiple ways in which species traits like trophic level, dispersal ability and degree of habitat specialisation influence species-level responses. The temporal scale of investigation may have a strong influence on the results of a study, with short-term crowding effects eventually giving way to long-term extinction debts. Moreover, many fragmentation effects like changes in genetic, morphological or behavioural traits of species require time to appear. By contrast, synergistic interactions of fragmentation with climate change, human-altered disturbance regimes, species interactions and other drivers of population decline may magnify the impacts of fragmentation. To conclude, we emphasise that anthropogenic fragmentation is a recent phenomenon in evolutionary time and suggest that the final, long-term impacts of habitat fragmentation may not yet have shown themselves.     

Fragment size does not matter when you are well connected: effects of fragmentation on fitness of coexisting gypsophiles

Most habitat fragmentation studies have focused on the effects of population size on reproductive success of single species, but studies assessing the effects of both fragment size and connectivity, and their interaction, on several coexisting species are rare. In this study, we selected 20 fragments along two continuous gradients of size and degree of isolation in a gypsum landscape in central Spain. In each fragment, we selected 15 individuals of each of three dominant gypsophiles (Centaurea hyssopifolia, Lepidium subulatum and Helianthemum squamatum, 300 plants per species, 900 plants in total) and measured several reproductive traits: inflorescence number, fruit set, seed set and seed mass. We hypothesised that plant fitness would be lower on small and isolated fragments due to an interaction between fragment size and connectivity, and that response patterns would be species‐specific. Overall, fragment size had very little effect on reproductive traits compared to that of connectivity. We observed a positive effect of fragment connectivity on C. hyssopifolia fitness, mediated by the increased seed predation in plants from isolated fragments, resulting in fewer viable seeds per capitulum and lower seed set. Furthermore, seed mass was lower in plants from isolated fragments for both C. hyssopifolia and L. subulatum. In contrast, few reproductive traits of H. squamatum were affected by habitat fragmentation. We discuss the implications of species‐specific responses to habitat fragmentation for the dynamics and conservation of gypsum plant communities. Our results highlight the complex interplay among plants and their mutualistic and antagonistic visitors, and reinforce the often‐neglected role of habitat connectivity as a key component of the fragmentation process.     

Neither species geographic range size,climatic envelope,nor intraspecific leaf trait variability capture habitat specialization in a hyperdiverse Amazonian forest

Many plant species exhibit strong association with topographic habitats at local scales. However, the historical biogeographic and physiological drivers of habitat specialization are still poorly understood, and there is a need for relatively easy‐to‐measure predictors of species habitat niche breadth. Here, we explore whether species geographic range, climatic envelope, or intraspecific variability in leaf traits is related to the degree of habitat specialization in a hyperdiverse tropical tree community in Amazonian Ecuador. Contrary to our expectations, we find no effect of the size of species geographic ranges, the diversity of climate a species experiences across its range, or intraspecific variability in leaf traits in predicting topographic habitat association in the ~300 most common tropical tree species in a 25‐ha tropical forest plot. In addition, there was no phylogenetic signal to habitat specialization. We conclude that species geographic range size, climatic niche breadth, and intraspecific variability in leaf traits fail to capture the habitat specialization patterns observed in this highly diverse tropical forest.     

Role of movement,interremnant dispersal and edge effects in determining sensitivity to habitat fragmentation in two forest‐dependent rodents

Abstract Habitat fragmentation and disturbance affect patterns of habitat use, animal movement and spatial behaviour and might have significant effects upon population dynamics and trends, and ultimately population persistence. Previous studies have suggested that the ability to disperse between remnants and a positive or neutral response to edges should be associated with species capable of persisting in remnant habitat. Using both radiotracking and trapping data, movement patterns, dispersal and response to habitat edges of Rattus fuscipes were examined within forests, corridors, remnants and pastures in south‐east Queensland, Australia. Rattus fuscipes has previously been shown to be robust to the effects of habitat fragmentation; however, contrary to expectations, R. fuscipes was found to be sensitive to edges, and no evidence of interremnant dispersal was detected, despite interremnant distances that were substantially smaller than the distances R. fuscipes was found to move in continuous habitat. Using only trapping data, the same factors were examined in relation to Melomys cervinipes, a species sensitive to fragmentation. Melomys cervinipes was found to utilize edge habitat, but no evidence of interremnant dispersal was detected, although the capacity to detect such movement was limited by low abundance in remnants where M. cervinipes was extant, and the species absence from many remnants. Movement patterns, interremnant dispersal capacity, and sensitivity to edges did not prove to be good predictors of these species responses to habitat fragmentation. Alternative explanations, such as population fluctuation and the capacity for rapid population growth in remnants for these two species, and the influence habitat quality has on these parameters should be investigated.     

中国蜥蜴类生活史和生态学特征数据集

截至2020年底, 中国共有226种蜥蜴类(不包括外来入侵种), 是世界上蜥蜴类多样性最丰富的国家之一。系统整理中国现有蜥蜴类的特征数据在物种起源与进化、形成与灭绝、保护生物学等研究中具有重要意义。但是, 目前还没有关于我国蜥蜴类生活史、生态学和地理分布等物种特征的完整数据库。本文通过系统查阅文献和数据资料, 共收集整理了中国现有226种本土蜥蜴类19个特征数据: 描述年份、中国受威胁等级、全球受威胁等级、是否中国特有种、是否岛屿特有种、平均体长、平均体重、食性、窝卵数、繁殖模式、四肢发育、活动时间、栖息生境、栖息地类型、栖息地宽度、海拔分布范围、地理分布范围、动物地理界和分布省份。在上述特征中, 除了四肢发育、描述年份、是否中国特有种、是否岛屿特有种和分布省份外, 其余特征数据均存在不同程度的缺失, 数据完整度为47.14%-100%。本数据集是目前关于中国蜥蜴类最新和最全的物种特征数据库, 可为我国蜥蜴类生态学、进化生物学、生物地理学和保护生物学等研究领域提供数据支持。     

Fragmentation in calcareous grasslands: species specialization matters

Habitat fragmentation resulting from anthropogenic land-use change may negatively affect both biodiversity and ecosystem structure and function. However, susceptibility to fragmentation varies between species and may be influenced by for instance specialization, functional traits and trophic level. We examined how total and specialist species richness, species composition and functional trait composition at two trophic levels (vascular plants and sap-feeding hoppers) vary with habitat fragmentation (patch size and connectivity) in dry calcareous grasslands in southeast Norway. We found that fragmentation affected plant and hopper species composition both totally and of habitat specialists, but with a net species loss only for the specialists, indicating greater susceptibility of specialized species. Reductions in patch size and increasing isolation negatively affected plant specialists with different sets of traits, effectively reducing the number of species with trait combinations suitable to persist in small and isolated patches. Fragmentation influenced trait composition of the total hopper community, but not of habitat specialists. A lesser degree of habitat association could explain why hoppers, despite belonging to a higher tropic level, seemed to be less susceptible to fragmentation than plants. Nonetheless, our study shows that habitat fragmentation affects both species richness, species composition and trait composition of plants and hoppers, indicating that fragmentation leads not only to a loss of species, but also alters dominance hierarchies and the functionality of grassland communities.     

Human pressures predict species’ geographic range size better than biological traits

Geographic range size is the manifestation of complex interactions between intrinsic species traits and extrinsic environmental conditions. It is also a fundamental ecological attribute of species and a key extinction risk correlate. Past research has primarily focused on the role of biological and environmental predictors of range size, but macroecological patterns can also be distorted by human activities. Here, we analyse the role of extrinsic (biogeography, habitat state, climate, human pressure) and intrinsic (biology) variables in predicting range size of the world's terrestrial mammals. In particular, our aim is to compare the predictive ability of human pressure vs. species biology. We evaluated the ability of 19 intrinsic and extrinsic variables in predicting range size for 4867 terrestrial mammals. We repeated the analyses after excluding restricted‐range species and performed separate analyses for species in different biogeographic realms and taxonomic groups. Our model had high predictive ability and showed that climatic variables and human pressures are the most influential predictors of range size. Interestingly, human pressures predict current geographic range size better than biological traits. These findings were confirmed when repeating the analyses on large‐ranged species, individual biogeographic regions and individual taxonomic groups. Climatic and human impacts have determined the extinction of mammal species in the past and are the main factors shaping the present distribution of mammals. These factors also affect other vertebrate groups globally, and their influence on range size may be similar as well. Measuring climatic and human variables can allow to obtain approximate range size estimations for data‐deficient and newly discovered species (e.g. hundreds of mammal species worldwide). Our results support the need for a more careful consideration of the role of climate change and human impact – as opposed to species biological characteristics – in shaping species distribution ranges.     

Meta-analysis reveals impacts of disturbance on reptile and amphibian body condition

Ecosystem disturbance is increasing in extent, severity and frequency across the globe. To date, research has largely focussed on the impacts of disturbance on animal population size, extinction risk and species richness. However, individual responses, such as changes in body condition, can act as more sensitive metrics and may provide early warning signs of reduced fitness and population declines. We conducted the first global systematic review and meta-analysis investigating the impacts of ecosystem disturbance on reptile and amphibian body condition. We collated 384 effect sizes representing 137 species from 133 studies. We tested how disturbance type, species traits, biome and taxon moderate the impacts of disturbance on body condition. We found an overall negative effect of disturbance on herpetofauna body condition (Hedges' g = −0.37, 95% CI: −0.57, −0.18). Disturbance type was an influential predictor of body condition response and all disturbance types had a negative mean effect. Drought, invasive species and agriculture had the largest effects. The impact of disturbance varied in strength and direction across biomes, with the largest negative effects found within Mediterranean and temperate biomes. In contrast, taxon, body size, habitat specialisation and conservation status were not influential predictors of disturbance effects. Our findings reveal the widespread effects of disturbance on herpetofauna body condition and highlight the potential role of individual-level response metrics in enhancing wildlife monitoring. The use of individual response metrics alongside population and community metrics would deepen our understanding of disturbance impacts by revealing both early impacts and chronic effects within affected populations. This could enable early and more informed conservation management.     

Habitat disturbance and hydrological parameters determine the body size and reproductive strategy of alluvial ground beetles

Environmental variability is the main driver for the variation of biological characteristics (life-history traits) of species. Therefore, life-history traits are particularly suited to identify mechanistic linkages between environmental variability and species occurrence and can help in explaining ecological patterns. For ground beetles, few studies directly related species traits to environmental variables. This study aims to analyse how life-history traits of alluvial ground beetles are controlled by environmental factors. I expected that the occurrence of species and the occurrence of specific traits are closely related to hydrological and disturbance parameters. Furthermore I expected most of the trait-variation to be explained by a combination of environmental variables, rather than by their isolated effects. Ground beetles were sampled in the year 2005 in floodplain grassland along the Elbe River in Germany. I used redundancy analysis to quantify the effects of hydrological, sediment, and disturbance related parameters on both species occurrence and species traits. I applied variation partitioning to analyse which environmental compartments explain most of the trait variation. Species occurrence and trait variation were both mainly controlled by hydrological and flood disturbance parameters. I could clearly identify reproductive traits and body size as key traits for floodplain ground beetles to cope with the environmental variability. Furthermore, combinations of hydrological, habitat disturbance, habitat type, and species diversity parameters, rather than their isolated effects, explained large parts of ground beetle trait variation. Thus, a main conclusion of this study is that ground beetle occurrence is mainly determined by complex, multi-scale interactions between environmental variability and their life-history traits.     

How species traits and affinity to urban land use control large-scale species frequency

Aim Although urban areas only occupy c. 2.8% of the earth's land surface, urbanization threatens biodiversity as areas of high human population density often coincide with high biodiversity. Therefore, nature conservation should concentrate on both remote areas and densely populated regions. Protecting rare plant species in rural and urban areas can contribute to the protection of biodiversity. We therefore need to understand why species are rare. Studies on causes of rarity often concentrate on either plant traits or extrinsic threats (such as habitat fragmentation or nitrogen enrichment). However, there are only a few studies that combine traits and extrinsic threats, although such analyses might clarify causes of rarity. We assessed how the affinity of vascular plant species to urban land use (‘urbanity’) interacts with plant traits in determining species frequency. Location Germany, resolution c. 12 km × 11 km. Methods Species with a low frequency may be rare because they occur in rare habitats or because of other reasons, although their habitat is frequent. Therefore, we calculated the frequency of species corrected for habitat frequency, i.e. relative species frequency. We explained relative species frequency by the interactions of species traits and species affinity to urban land use using generalized linear models. Simultaneous autoregressive error models controlled for phylogenetic relationships of species. Results Relative species frequency depends on species affinity to urban land use, independent of the different interactions between traits and urbanity used as predictors. The higher the urbanity the higher is species frequency. Urbanity interacts with species preferences towards temperature and soil acidity. Moreover, dispersal, nitrogen preferences and origin explain relative species frequency, amongst others. Main conclusions Many rare species, especially those preferring cool or acidic habitats might already have disappeared from urban areas. Analyses that combine species traits and environmental effects can explain the causes of rarity and help to derive better conservation strategies.     

Life-history traits associated with fragmentation vulnerability of lizards in the Thousand Island Lake, China

Following habitat fragmentation, the remnant faunal community will undergo a period of species loss or 'relaxation.' Theory predicts that species with particular life-history traits, such as a small population size, small geographical range, low fecundity and large body size, should be more vulnerable to fragmentation. In this study, we investigated the relationships between the above life-history traits and the fragmentation vulnerability index (the number of islands occupied) of five lizard species inhabiting recently isolated land-bridge islands in the Thousand Island Lake, China. Data on life-history traits were collected from field surveys (population density) and from the literature (body size, clutch size and geographical range size). The species–area relationships for lizards sampled from the mainland versus on the islands differed significantly (i.e. the number of species inhabiting islands was decreased relative to similar-sized areas on the mainland), indicating that species extinction has occurred on all of the study islands following isolation. For the fragmentation vulnerability index, model selection based on Akaike's information criterion identified natural density at mainland sites as the best correlate of vulnerability to fragmentation, supporting the hypothesis that rare species are most vulnerable to local extinction and will be lost first from fragmented landscapes. In contrast, there was little evidence for an effect of lizards' snout–vent length, clutch size or geographical range size on fragmentation vulnerability. Identification of species traits that render some species more vulnerable to fragmentation than others has important implications for conservation and can be used to aid direct management efforts.     

Eutrophication and fragmentation are related to species’ rate of decline but not to species rarity: results from a functional approach

Due to ubiquitous eutrophication and fragmentation, many plant species are actually threatened in Europe. Most ecosystems face an overall nutrient input leading to changes in species composition. Fragmentation is effectively influencing species survival. We investigate if two different measures of species performance of 91 calcareous grassland species–rate of decline and rarity—are related to comparable traits and hence processes. On the one hand we expected that species rate of decline is mainly determined by the processes of eutrophication and fragmentation. On the other hand we hypothesized that the importance of site characteristics may overwhelm the effect of eutrophication and fragmentation for species rarity. Hence, we compared persistence traits responding to eutrophication, dispersal traits being related to fragmentation and ecological site factors for decreasing and increasing species and for rare and common species. The results suggest that increasing species had better means of long-distance dispersal and were more competitive than decreasing species. In contrast, there were hardly any differences in traits between rare and common species, but site characteristics were related to species rarity. Rare species were in the main those with ecological preferences for warm, dry, light and nutrient poor conditions. This study may represent a basis for the assessment of plant species threat. Applying the deduced knowledge about the life history of decreasing versus increasing species to habitat-scale approaches it is possible to predict which species may become threatened in the future simply from the combination of their trait values. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Does wing morphology affect recolonization of restored farmland by ground‐dwelling beetles?

Revegetation of previously cleared land is widely used to increase habitat area and connectivity of remnant vegetation for biodiversity conservation. Whether new habitat attracts or supports fauna depends on the dispersal traits of those fauna as well as the structure and composition of the surrounding landscape. Here, we examined wing morphology as a key dispersal trait for beetles in a revegetated landscape and asked, first, how it was related to phylogeny (family), trophic position, and body size. Second, we asked if wing morphology of recolonizing (or persisting) beetles varied with habitat characteristics at multiple scales, from microhabitat to landscape context. Third, we examined how common winged and wingless species responded to habitat at multiple scales. We measured the wing morphology of ground‐dwelling beetles from a restoration chronosequence, including paddocks, “young” revegetation (8–11 years old), “old” revegetation (14–19 years old), and fenced remnant vegetation. We found that body size and family membership were significant predictors of winglessness, with wingless species of carabids and curculionids being larger than their winged counterparts. We found no difference in the number of sites occupied by winged and wingless species, and no relationship between the wing morphology traits represented in different locations and habitat characteristics or landscape context. Furthermore, the most abundant species of both winged and wingless ground‐dwelling beetles had relatively little affinity to any habitat successional stage. Thus, despite intrinsic differences in wing morphology among species of ground‐dwelling beetle, we found no evidence that flight‐related dispersal limitations influenced recolonization (or persistence) in this landscape.     

Extensive gaps and biases in our knowledge of a well‐known fauna: implications for integrating biological traits into macroecology

Aim Ecologists seeking to describe patterns at ever larger scales require compilations of data on the global abundance and distribution of species. Comparable compilations of biological data are needed to elucidate the mechanisms behind these patterns, but have received far less attention. We assess the availability of biological data across an entire assemblage: the well‐documented demersal marine fauna of the United Kingdom. We also test whether data availability for a species depends on its taxonomic group, maximum body size, the number of times it has been recorded in a global biogeographic database, or its commercial and conservation importance. Location Seas of the United Kingdom. Methods We defined a demersal marine fauna of 973 species from 15 phyla and 40 classes using five extensive surveys around the British Isles. We then quantified the availability of data on eight key biological traits (termed biological knowledge) for each species from online databases. Relationships between biological knowledge and our predictors were tested with generalized linear models. Results Full data on eight fundamental biological traits exist for only 9% (n= 88) of the UK demersal marine fauna, and 20% of species completely lack data. Clear trends in our knowledge exist: fish (median biological knowledge score = six traits) are much better known than invertebrates (one trait). Biological knowledge increases with biogeographic knowledge and (to a lesser extent) with body size, and is greater in species that are commercially exploited or of conservation concern. Main conclusions Our analysis reveals deep ignorance of the basic biology of a well‐studied fauna, highlighting the need for far greater efforts to compile biological trait data. Clear biases in our knowledge, relating to how well sampled or ‘important’ species are suggests that caution is required in extrapolating small subsets of biologically well‐known species to ecosystem‐level studies.     

Detecting Fragmentation Extinction Thresholds for Forest Understory Plant Species in Peninsular Spain

Ecological theory predicts that fragmentation aggravates the effects of habitat loss, yet empirical results show mixed evidences, which fail to support the theory instead reinforcing the primary importance of habitat loss. Fragmentation hypotheses have received much attention due to their potential implications for biodiversity conservation, however, animal studies have traditionally been their main focus. Here we assess variation in species sensitivity to forest amount and fragmentation and evaluate if fragmentation is related to extinction thresholds in forest understory herbs and ferns. Our expectation was that forest herbs would be more sensitive to fragmentation than ferns due to their lower dispersal capabilities. Using forest cover percentage and the proportion of this percentage occurring in the largest patch within UTM cells of 10-km resolution covering Peninsular Spain, we partitioned the effects of forest amount versus fragmentation and applied logistic regression to model occurrences of 16 species. For nine models showing robustness according to a set of quality criteria we subsequently defined two empirical fragmentation scenarios, minimum and maximum, and quantified species’ sensitivity to forest contraction with no fragmentation, and to fragmentation under constant forest cover. We finally assessed how the extinction threshold of each species (the habitat amount below which it cannot persist) varies under no and maximum fragmentation. Consistent with their preference for forest habitats probability occurrences of all species decreased as forest cover contracted. On average, herbs did not show significant sensitivity to fragmentation whereas ferns were favored. In line with theory, fragmentation yielded higher extinction thresholds for two species. For the remaining species, fragmentation had either positive or non-significant effects. We interpret these differences as reflecting species-specific traits and conclude that although forest amount is of primary importance for the persistence of understory plants, to neglect the impact of fragmentation for some species can lead them to local extinction.     

Enhanced reproductive success revealed key strategy for persistence of devastated populations in Himalayan food‐deceptive orchid,Dactylorhiza hatagirea

Anthropogenic disturbances adversely affect populations of rare and endemic plants, resulting in reduction of their population size and performance. Among different plant groups, deceptive terrestrial orchids are vulnerable and possess greater extinction risks because of rarity in occurrence. To understand the response of food‐deceptive terrestrial orchids to disturbances, we selected Dactylorhiza hatagirea as our representative species, which is endemic to Himalaya, and studied its natural populations. This species is rare for being habitat specific, pollination limited and threatened in its natural habitats. We tested the hypothesis that disturbances lead to reduction in population size and plant performance of food‐deceptive terrestrial orchids. For assessing the impact of disturbance, two contrasting groups, heavily devastated (HD) and lightly devastated (LD), were identified on the basis of frequency and intensity of disturbance (harvesting of plant for tubers) by interviewing local people, medicinal plant extractors and shepherds. HD sites, in comparison to LD sites, were found to have smaller population sizes, but showed an increase in plant growth traits (plant height, specific leaf area, leaf N and specific shoot length). Similarly, plants at HD sites were found to have invested less in inflorescence (inflorescence size, inflorescence length, inflorescence length fraction and flowers per length), but despite that showed higher reproductive success. This was a clear indication of enhanced performance of its populations driven by disturbances. Our findings suggested that food‐deceptive species in small populations tend to reduce the probability of population extinction and have the capability to recover rapidly if conserved in time.     

Species diversity and persistence in restored and remnant tallgrass prairies of North America: a function of species' life history, habitat type, or sampling bias?

1. The re-assembly of native animal communities in restored landscapes is a relatively unexplored phenomenon for many taxa. Specifically, ecologists lack the ability to generalize about how species traits, habitat size, habitat type (here, remnant prairie vs. restored grassland), and temporal variation interact to affect species diversity or species' persistence probabilities. 2. To investigate these relationships, moth communities from 10 prairie remnants and restorations were sampled over a 3-year interval and a combination of NMDS ordination, logistic regression, and repeated measures anova were used to test hypotheses regarding how life history variables and habitat characteristics determine the degree to which restored habitats develop a moth fauna similar to remnants. 3. Within sampling years, restored tallgrass prairies that were >or= 7 years old possessed lepidopteran species assemblages that were generally similar to those in prairie remnants. Community similarity, however, was driven by common moth species likely to also occur in the surrounding agricultural habitat. Species persistence was significantly influenced by a series of trait combinations identified using principal components analysis. Temporal variation independent of habitat type or patch size was the most significant determination of variation in species composition among sites. 4. These results suggest that lepidopteran persistence in restored landscapes is at least partially determined by species' life history attributes. The correlation between sampling year and species richness suggests that both weather effects on species voltinism and interannual differences in sampling bias may make it difficult for land managers to detect changes in species abundance following disturbance or habitat management. 5. Species may not necessarily possess specific life history traits that reduce extinction risk or enhance recolonization probabilities in the highly modified agricultural landscape of the Midwestern USA. Rather, voltinism, fecundity, body size, and host plant specialization may influence the ability of species to maintain populations in the greater agricultural landscape or to escape mass mortality following disturbances imposed by prairie management.