Spatial Patterns Of Species Distribution Research Articles

Comparative Spatial Distribution of Sucking Insect-Pest-Complex in Summer and Monsoon Cowpea [Vigna unguiculata (L.) Walp.

Background: Pulse crops are known as an important dietary source of proteins for a major part of the vegetarian population across the globe; especially in India. Legume crops help restoration of soil fertility through symbiotic nitrogen fixation. Spatial distribution is an important aspect as it interprets the interaction between individuals of the species and their habitat. The biological reason of aggregation is highly unpredictable and it depends on behavioural pattern of the insect; therefore, spatial distribution accounts for informative description of organisms. Methods: In order to study the spatial distribution of sucking pests of cowpea, a field trial was laid out during Zaid and Kharif separately at the Instructional Farm of Rajasthan College of Agriculture, Udaipur in 2019 and 2020. Cowpea variety Pusa Komal was cultivated in 6 plots each of 3 m x 3 m with the row to row and plant to plant spacing of 50 cm and 10 cm, respectively. Different distribution pattern were used to determine spatial distribution pattern of species of insect fauna associated with cowpea during the summer and monsoon season. Result: The spatial distribution for most the insect pest complex was contagious during both the respective seasons. All positive IDM (index of clumping) values confirmed the clumping of the pest during the season. The mean crowding index was more than unity, indicated clumped interaction.

The particular species determining spatial heterogeneity in shady and terrace on the Qinghai-Tibetan Plateau, China

Spatial patterns of plant species and patchy community are important properties in grasslands. However, research regarding spatial patterns of formed patches with various species has not fully advanced until now. Our purpose is to clarify differences in spatial pattern formed by species and community constructed under shady and terrace habitats. The three common Kobresia-Carex patches (Size 1, 0.6–0.9 m2; Size 2, 3.0–3.8 m2 and Size 3, 6.5–8.8 m2) were selected in shady and terrace on the Qinghai-Tibetan Plateau, and corresponding quadrats of 1m×1m, 2m×2m and 3m×3m were placed for S1, S2 and S3 patches, respectively. The surveyed quadrats were divided into 20cm×20cm large cells (L-cells), and further divided into four 10cm×10cm small cells (S-cells). We used the binary occurrence system (presence/absence data) to record occurrences of all species in S-cells. The analysis shows that the power law model was well able to determine the spatial distribution pattern of species or patchy community in shady and terrace. All species and patches show aggregated distribution in shady and terrace habitats. In the shady habitat, the relative spatial heterogeneity (ε) of individual plant species was lowest at presence frequency (P) of 0.1–0.3, whereas in the terrace habitat ε was lowest at P <0.1, and ε increased monotonically with increasing P. For most dominant species, P and ε values were higher in terrace than those in shady. We concluded that the dominant species largely determine spatial heterogeneity of the Kobresia-Carex patches, while companion and rare species have weak influence on the community-level heterogeneity in shady and terrace habitats.

Niche filtering, competition and species turnover in a metacommunity of freshwater molluscs

Metacommunity structure reflects the interplay of various processes, including niche filtering, extinction/colonization and interspecific interactions. Spatial patterns of species distributions are often analyzed to infer these processes. However, such inferences rely on often unrealistic equilibrium assumptions, and remain ambiguous, as different processes can produce similar patterns. Temporal data may improve these inferences. For example, stochastic species turnover may occur in local communities, while, on the long run, temporal changes are kept within limits set by locally available niches. Our objective is to explore how the joint analysis of spatial and temporal patterns can clarify the contribution of different processes to metacommunity structure. We recorded the occurrences of 21 freshwater mollusc species, and environmental data, in 250 sites over 17 successive years in a network of ponds in Guadeloupe (Lesser Antilles). We analyzed variation in α and β‐diversities in space and time, and used a joint‐species distribution mode to characterize species–environment and species–species relationships. Local communities showed pronounced temporal variation reflecting both imperfect species detection and true stochastic species turnover. On the long term however, local communities were largely controlled by niche filtering along two main environmental gradients, one driven by site connectivity, the other by hydrological stability and aquatic vegetation. Two gastropod clades, caenogastropods and pulmonates, showed contrasted spatio–temporal distributions resulting from different responses to these gradients, and these distributions seemed little altered by interspecific competition. Our study illustrates the benefit of using spatiotemporal metacommunity data to discern long‐term impacts of niche filtering and species interactions behind short‐term stochasticity.

Spatial Distribution and Species Association of Dominant Tree Species in Huangguan Plot of Qinling Mountains, China

The spatial distribution pattern and population structure of trees are shaped by multiple processes, such as species characteristics, environmental factors, and intraspecific and interspecific interactions. Studying the spatial distribution patterns of species, species associations, and their relationships with environmental factors is conducive to uncovering the mechanisms of biodiversity maintenance and exploring the underlying ecological processes of community stability and succession. This study was conducted in a 25-ha Qinling Huangguan forest (warm-temperate, deciduous, broad-leaved) dynamic monitoring plot. We used univariate and bivariate g(r) functions of the point pattern analysis method to evaluate the spatial distribution patterns of dominant tree species within the community, and the intra- and interspecific associations among different life-history stages. Complete spatial randomness and heterogeneous Poisson were used to reveal the potential process of community construction. We also used Berman’s test to determine the effect of three topographic variables on the distribution of dominant species. The results indicated that all dominant species in this community showed small-scale aggregation distribution. When we excluded the influence of environmental heterogeneity, the degree of aggregation distribution of each dominant species tended to decrease, and the trees mainly showed random or uniform distribution. This showed that environmental heterogeneity significantly affects the spatial distribution of tree species. Dominant species mainly showed positive associations with one another among different life-history stages, while negative associations prevailed among different tree species. Furthermore, we found that the associations between species were characterized by interspecific competition. Berman’s test results under the assumption of complete spatial randomness showed that the distribution of each dominant species was mainly affected by slope and convexity.

Effects of plant interactions on the populations of the endangered Fagus pashanica

Background Examining the spatial patterns of species distributions and their underlying processes is important for characterising population dynamics and can provide novel insights for conservation management. However, little attention has been paid to spatial distribution patterns of endangered species. Aims We quantified the effects of plant interactions and environmental heterogeneity on the spatial distribution of endangered Fagus pashanica in communities, to reveal the processes which may account for its population dynamics. Methods We collected spatial coordinates of each tree in communities at three elevations and evaluated the effects of plant interactions and environmental heterogeneity using point pattern analysis. Results Dispersal limitation rather than habitat filtering shaped the spatial patterns of F. pashanica at all three elevations. Intraspecific competition in F. pashanica was found to be significant at middle- and high elevations; interspecific interactions were not significant at any of the three elevations. Conclusions Intraspecific competition significantly affected the spatial patterns of F. pashanica. Dispersal limitation appear to lead to aggregation, while at small spatial scales intraspecific interactions are likely to decrease aggregation due to potential density-dependent thinning effects.

亚热带不同纬度森林群落物种空间分布格局

PDF HTML阅读 XML下载 导出引用 引用提醒 亚热带不同纬度森林群落物种空间分布格局 DOI: 10.5846/stxb202106121570 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（32060305）；广西自然科学基金面上项目（2020GXNSFAA159108，2022GXNSFAA035583） Spatial distribution patterns of forest community species at different latitudes in the subtropics Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨我国亚热带森林群落中物种空间分布格局特点及其成因，揭示其共性规律和个性差异，为相关区域的生物多样性保护和监测工作提供科学依据。选取我国亚热带不同纬度的6个1 hm2典型森林群落中所有胸径（DBH，Diameter at Breast Height）≥ 1 cm的物种为研究对象；采用L （t）方程统计所有监测物种的空间分布格局类型，为满足L （t）方程的统计精度，将各群落中多度≥10株的植物以物种为单位统计，多度<10株的低多度物种和单个体物种则以种组为单位进行空间点格局分析；并对物种多度、胸径与空间聚集程度的度量指标L10进行相关性分析。结果表明：（1）亚热带不同纬度群落中多度≥10株物种的空间分布格局表现出相似的尺度依赖性规律：显著聚集分布比例随尺度增大而降低，不同纬度群落的变化幅度存在差异，纬度较低的群落稳定性更强。（2）各群落中低多度种组空间分布格局表现出小尺度显著聚集分布，大尺度随机分布的尺度效应，但尺度效应在不同纬度群落间存在差异；各群落的单个体种组空间分布格局均以随机分布为主。（3）不同纬度群落物种多度与空间聚集程度之间均存在负相关关系，物种多度对空间聚集程度的影响随纬度从高到低逐渐减弱。（4）较高纬度群落物种胸径与空间聚集程度之间存在负相关关系；随纬度从高到低，物种胸径对空间聚集程度影响水平逐渐降低。对亚热带不同纬度森林群落物种空间分布格局形成原因的进一步探讨，认为由纬度差异引起的生境异质性是影响群落物种空间分布格局产生过程的主要因素，此外，林型、扩散限制、密度制约和随机作用是影响各群落物种空间格局成因及多样性维持的次要因素。 Abstract:This study was conducted to investigate the characteristics of species spatial distribution patterns and their causes in subtropical forest communities in China. It also revealed the common patterns and individual differences in the spatial distribution patterns of species in different forest communities in the subtropics. The purpose of the study was to provide a scientific basis for biodiversity conservation and monitoring in the relevant regions. All species with diameter at breast height (DBH) ≥ 1 cm in six typical forest communities of 1 hm2 at different latitudes in subtropical China were selected for the study. The L(t) function was used to count the spatial distribution pattern types of all the monitored species. In order to meet the statistical precision of the L(t) function, the plants with abundance ≥ 10 plants in each community were counted as species, and low abundance species with abundance < 10 plants and single individual species were analyzed as species groups for spatial point pattern analysis; and the correlation between species abundance, DBH and the metric of spatial aggregation degree, L10, was analyzed. The results showed that:(1) The spatial distribution patterns of species with abundance ≥ 10 plants in communities at different latitudes in the subtropics showed similar scale-dependent patterns:the proportion of significantly aggregated distributions decreased with increasing scale, the magnitude of change in communities at different latitudes differed, and communities at lower latitudes were more stable. (2) The spatial distribution pattern of low abundance species groups in each community showed the scale effect of small-scale significantly aggregated distribution and large-scale random distribution, but the scale effect differed among communities at different latitudes; the spatial distribution pattern of individual species groups in each community was mainly random distribution. (3) There was a negative correlation between species abundance and spatial aggregation in communities at different latitudes, and the effect of species abundance on spatial aggregation diminished with latitude from high to low. (4) There was a negative correlation between DBH and the degree of spatial aggregation in communities at higher latitudes; the level of influence of DBH on the degree of spatial aggregation gradually decreased with higher to lower latitudes. The spatial distribution patterns of species in forest communities at different latitudes in the subtropics were further explored. It was concluded that habitat heterogeneity caused by latitudinal differences was the main factor influencing the process of spatial distribution patterns of community species, while forest type, dispersal limitation, density constraint and stochastic effects were secondary factors affecting the causes of spatial patterns of species and maintenance of diversity in each community. 参考文献 相似文献 引证文献

Threshold dynamics of a reaction-diffusion-advection Leslie-Gower predator-prey system

&lt;p style='text-indent:20px;'&gt;In this paper, we investigate the global dynamics of a Leslie-Gower predator-prey system in advective homogeneous environments. We discuss the existence and uniqueness of positive steady-state solutions. We study the large time behavior of solutions and establish threshold conditions for persistence and extinction of two species when they live in open advective environments. Numerical simulations indicate that the introduction of advection leads to the evolution of spatial distribution patterns of species and specially it may induce spatial separation of the prey and predator under some conditions.&lt;/p&gt;

Effectively inferring overall spatial distribution pattern of species in a map when exact coordinate information is missing

Abstract Mapping and comparing biodiversity in space is a routine task in ecological research. However, accurate biodiversity mapping requires exact distributional information as inputs. When exact geographical coordinate information is missing or when only coarse distribution of species is available at the quadrat or plot level, how can we effectively infer and compare spatial distributional patterns of species with reasonable accuracy while controlling the confounding impacts of scale dependency? A crossing‐scale coefficient of variation (CCV) is calculated for three simple diversity indices, the Shannon, Gini–Simpson and reciprocal‐Simpson evenness indices, from the quadrat‐based biodiversity data over varying sampling grain sizes for subtly measuring overall spatial distributional pattern of species in a survey map. Extensive numerical simulations showed that, when the overall distribution of organisms was regular, CCV tended to be very small, for all the three evenness indices. By contrast, when the distribution was highly aggregate, CCV tended to be large. Finally, an intermediate CCV was observed when organism distribution was random. To this end, all the three evenness indices can detect the subtle change on aggregate or regular distribution. Among the indices, the Gini–Simpson evenness index is the most insensitive to both the change of population size of species and the number of sampling grain sizes used. Compared to available spatial statistic metrics that requires exact geographical coordinates as inputs, CCV is a useful metric for assessing the overall spatial distribution pattern of a species across sampling plots in which exact spatial coordinates of each individual are unavailable. Empirical applications of the CCV metric showed that plants in habitat patches extensively managed by humans can present very aggregate distributional pattern, being counterintuitive to the usual expectation that plants in cultivated or planted land should present regular distributional pattern. The present study recommends one effective tool, the combination of CCV and evenness indices, for exploring the overall spatial distributional pattern of a single species under the quadrat‐sampling scheme. The proposed method is particularly suitable to handle ecological data for which the finest‐scale distributional coordinate information of each individual of species is missing.

Influence of the soil on the spatial structure of forest species – preliminary results in a terra firme secondary forest plot, Amapá, Brazil

In recent years there has been increasing interest in the relationships between edaphic factors in tropical forests due to the complexity and the dynamic nature of plant interactions with the physical environment. This research sought to investigate the correlation of edaphic factors with the spatial distribution patterns of the 16 main tree species in a dense ombrophilous forest of terra firme in Macapá, Amapá, Brazil. Forty subplots along a topographic gradient were installed for floristic studies as well as to collect composite soil samples. The spatial distribution pattern was described by the Payandeh and Morisita indexes. Canonical correspondence analysis (CCA) and geostatistical techniques were used to describe the relationship between species distribution and environmental variables. It was confirmed that the factors influencing the spatial behaviour of plants in the vegetation can be associated with both the endogenous (dispersion mode) and exogenous (the environmental conditions to which they are subjected) processes. Variations in spatial distribution patterns of species in relation to existing environmental heterogeneity were observed based on the CCA, mainly associated with the contents of pH, potential acidity, organic matter (OM), phosphorus (P) and potassium (K) in soil. Finally, based on ordinary kriging there was evidence that the OM contents in the soil presented a spatial dependence structure in the vegetation. Our findings show that natural disturbances (e.g. natural fall of trees) and human land use (e.g. logging) induce changes in species composition and abiotic resource availability. The results highlight the importance of understanding the processes that influence the strengthening of environment–plant interactions by the lasting effects of successional recovery.

Predicting hotspots for threatened plant species in boreal peatlands

Understanding the spatial patterns of species distribution and predicting suitable habitats for threatened species are central themes in land use management and planning. In this study, we examined the geographic distribution of threatened mire plant species and identified their national hotspots, i.e. areas with high amounts of suitable habitats for threatened mire plant species. We also determined the main environmental correlates related to the distribution patterns of these species. The specific aims were to: (1) identify the environmental variables that control the distribution of threatened peatland species in a boreal aapa mire zone, Finland; and (2) to identify the richness patterns and hotspots of threatened species. Our results showed that the combination of individual species models offers a useful tool for identifying landscape-scale richness patterns for threatened plant species. The modeling performance was high across the modelled species, and the richness patterns generated by single models coincide with the expected richness pattern based on expert knowledge. The method is therefore a powerful tool for basic biodiversity applications. In cases where reliable models for species occurrences and hotspots can be produced, these models can play a significant role in land-use planning and help managers to meet different conservation challenges.

Incorporating the geometry of dispersal and migration to understand spatial patterns of species distributions

Dispersal and migration can be important drivers of species distributions. Because the paths followed by individuals of many species are curvilinear, spatial statistical models based on rectilinear coordinates systems would fail to predict population connectivity or the ecological consequences of migration or species invasions. I propose that we view migration/dispersal as if organisms were moving along curvilinear geometrical objects called smooth manifolds. In that view, the curvilinear pathways become the ‘shortest realised paths’ arising from the necessity to minimise mortality risks and energy costs. One can then define curvilinear coordinate systems on such manifolds. I describe a procedure to incorporate manifolds and define appropriate coordinate systems, with focus on trajectories (1D manifolds), as parts of mechanistic ecological models. I show how a statistical method, known as ‘manifold learning’, enables one to define the manifold and the appropriate coordinate systems needed to calculate population connectivity or study the effects of migrations (e.g. in aquatic invertebrates, fish, insects and birds). This approach may help in the design of networks of protected areas, in studying the consequences of invasion, range expansions, or transfer of parasites/diseases. Overall, a geometrical view to animal movement gives a novel perspective to the understanding of the ecological role of dispersal and migration.

Hydrologic refugia, plants, and climate change.

Climate, physical landscapes, and biota interact to generate heterogeneous hydrologic conditions in space and over time, which are reflected in spatial patterns of species distributions. As these species distributions respond to rapid climate change, microrefugia may support local species persistence in the face of deteriorating climatic suitability. Recent focus on temperature as a determinant of microrefugia insufficiently accounts for the importance of hydrologic processes and changing water availability with changing climate. Where water scarcity is a major limitation now or under future climates, hydrologic microrefugia are likely to prove essential for species persistence, particularly for sessile species and plants. Zones of high relative water availability - mesic microenvironments - are generated by a wide array of hydrologic processes, and may be loosely coupled to climatic processes and therefore buffered from climate change. Here, we review the mechanisms that generate mesic microenvironments and their likely robustness in the face of climate change. We argue that mesic microenvironments will act as species-specific refugia only if the nature and space/time variability in water availability are compatible with the ecological requirements of a target species. We illustrate this argument with case studies drawn from California oak woodland ecosystems. We posit that identification of hydrologic refugia could form a cornerstone of climate-cognizant conservation strategies, but that this would require improved understanding of climate change effects on key hydrologic processes, including frequently cryptic processes such as groundwater flow.

Temporal variation in phytoplankton beta diversity patterns and metacommunity structures across subtropical reservoirs

Summary Analysing the beta diversity components and spatial patterns of species distribution may provide key insights into how local communities respond to human‐induced environmental changes. Indeed, analysing temporal variation in spatial patterns of species distribution may reveal trends of biotic homogenisation and its likely causes. We used an eight‐year phytoplankton data set generated from to 17 reservoirs in Brazil to analyse the temporal variability in beta diversity and its turnover and nestedness components. This data set was also used to determine metacommunity structures across these subtropical reservoirs. We tested whether there was any long‐term temporal trend in beta diversity that might be indicative of biotic homogenisation or differentiation. We also tested how temporal variation was related to climatic conditions, environmental heterogeneity, productivity and cyanobacterial dominance. Lastly, we verified whether the phytoplankton metacommunity showed non‐random structure. We did not find supporting evidence for biotic homogenisation among the reservoirs. Rather, we did find that nestedness decreased during the study. Environmental heterogeneity was the main variable positively related to phytoplankton beta diversity, while high ammonium concentration and cyanobacterial abundance were negatively correlated with spatial variation among the reservoirs. Despite the noticeable temporal variation in metacommunity structures, the phytoplankton species responded similar to latent environmental gradients. Clementsian patterns found mainly in fall and winter were consistent with differences in species composition between sites, reinforcing the role of environmental filtering in driving changes in these metacommunities. Our results suggest that eutrophication control is essential to prevent biotic homogenisation, at least in our study system. We also highlight that metacommunity patterns detected in snapshot surveys should not be extrapolated temporally.

Investigating distribution pattern of species in a warm-temperate conifer-broadleaved-mixed forest in China for sustainably utilizing forest and soils

The maintaining mechanisms and potential ecological processes of species diversity in warm temperate- conifer-broadleaved-mixed forest are far from clear understanding. In this paper, the relative neighborhood density Ω was used to analyze the spatial distribution patterns of 34 species with ≥11 individuals in a warm- temperate-conifer-broadleaved-mixed forest, northern China. Then we used canonical correspondence analysis (CCA) and Torus-translation test (TTT) to explain the distribution of observed species. Our results show that aggregated distribution is the dominant pattern in warm-temperate natural forest and four species regular distribution at the spatial scale >30m. The aggregated percentage and intensity decline with spatial scale, abundance and size classes increasing. Rare species are aggregated more than intermediate and abundant species. These results prove sufficiently the effects existence of scale separation, self-thinning and Janzen-Connell hypothesis. In addition, functional traits (dispersal modes and shade tolerance) also have a significant influence on distribution of species. The results of CCA confirm that slope and convexity are the most important factors affecting the distribution of tree species distribution, elevation and slope of shrub species though the combination of topographic variables only explained 1% of distribution of tree species and 2% of shrub species. Most species don't have habitat preference; however 47.1% (16/34) species including absolutely dominant tree (Pinus tabulaeformis and Quercus wutaishanica) and shrub species (Rosa xanthina) and most other species with important value in the front, are strongly positively or negatively associated with at least one habitat. The valley and ridge are most distinct habitat with association of 12 species in the plot. However, high elevation slope with 257 quadrats is the most extensive habitat with only four species. Therefore, there is obvious evidence that habitat heterogeneity play an important role on shaping spatial distribution of species in warm temperate forest. Our research results provide significant evidence that dispersal limitation and habitat heterogeneity have a contribution jointly to regulating the spatial distribution pattern of species in warm-temperate-forest in China.

Space‐time investigation of the effects of fishing on fish populations

Species distribution models (SDMs) are important statistical tools for obtaining ecological insight into species-habitat relationships and providing advice for natural resource management. Many SDMs have been developed over the past decades, with a focus on space- and more recently, time-dependence. However, most of these studies have been on terrestrial species and applications to marine species have been limited. In this study, we used three large spatio-temporal data sources (habitat maps, survey-based fish density estimates, and fishery catch data) and a novel space-time model to study how the distribution of fishing may affect the seasonal dynamics of a commercially important fish species (Pacific Dover sole, Microstomus pacificus) off the west coast of the USA. Dover sole showed a large scale change in seasonal and annual distribution of biomass, and its distribution shifted from mid-depth zones to inshore or deeper waters during late summer/early fall. In many cases, the scale of fishery removal was small compared to these broader changes in biomass, suggesting that seasonal dynamics were primarily driven by movement and not by fishing. The increasing availability of appropriate data and space-time modeling software should facilitate extending this work to many other species, particularly those in marine ecosystems, and help tease apart the role of growth, natural mortality, recruitment, movement, and fishing on spatial patterns of species distribution in marine systems.

Spatial extent of biotic interactions affects species distribution and abundance in river networks: the freshwater pearl mussel and its hosts

AbstractAimAt what spatial extent are biotic interactions discernible influences on the distribution and abundance of species in river networks? We address this question with analyses of data from river networks for Margaritifera margaritifera, a freshwater mussel that passes its larval stage attached to a host fish.LocationTwenty river networks in Galicia, north‐western Spain.MethodsA maximum‐entropy approach was implemented to model the species’ distribution. Geostatistical mixed models were used to analyse the mussel's abundance in dendritic river networks. Predictor variables included the abundance and biomass of host fish (biotic interactions) and abiotic predictors for climate, geology and land‐form.ResultsMaxent models of species distribution were improved by 4.5% in terms of the area under the receiver‐operating characteristic curve (AUC) by the inclusion of biotic interactions. Host‐fish predictors contributed 63% of the Maxent model prediction of mussel presence. A geostatistical mixed model explained 52% of the variance in mussel abundance when including all the mussel abundance sites in the study area; abiotic predictors had no significance and salmonid biomass and resident trout population density were the only significant biotic predictors, together explaining 2.4% of the variance. An autocovariate representing biotic interactions between mussels and fish explained 11.7% of the variance. Using only sites where migratory host fish were present (n = 149), a mixed model explained more variance (78%) and the contribution from the autocovariate for parasite–host interactions was about three times larger than for the model including all sites (n = 419). The spatial autocorrelation from mussel–fish interactions had a spatial extent (geostatistical range) greater than 15 km.Main conclusionsInteractions between mussels and their larval hosts in river networks are manifested in spatial patterns of species distribution and abundance in this region, encompassing 20 river networks. The directional topology of dendritic river networks strongly supports the upstream dispersal of mussels by parasitized host fish as a component of spatial autocorrelation in mussel abundance.

Genetic structuring across marine biogeographic boundaries in rocky shore invertebrates.

Biogeography investigates spatial patterns of species distribution. Discontinuities in species distribution are identified as boundaries between biogeographic areas. Do these boundaries affect genetic connectivity? To address this question, a multifactorial hierarchical sampling design, across three of the major marine biogeographic boundaries in the central Mediterranean Sea (Ligurian-Tyrrhenian, Tyrrhenian-Ionian and Ionian-Adriatic) was carried out. Mitochondrial COI sequence polymorphism of seven species of Mediterranean benthic invertebrates was analysed. Two species showed significant genetic structure across the Tyrrhenian-Ionian boundary, as well as two other species across the Ionian Sea, a previously unknown phylogeographic barrier. The hypothesized barrier in the Ligurian-Tyrrhenian cannot be detected in the genetic structure of the investigated species. Connectivity patterns across species at distances up to 800 km apart confirmed that estimates of pelagic larval dispersal were poor predictors of the genetic structure. The detected genetic discontinuities seem more related to the effect of past historical events, though maintained by present day oceanographic processes. Multivariate statistical tools were used to test the consistency of the patterns across species, providing a conceptual framework for across-species barrier locations and strengths. Additional sequences retrieved from public databases supported our findings. Heterogeneity of phylogeographic patterns shown by the 7 investigated species is relevant to the understanding of the genetic diversity, and carry implications for conservation biology.

Patterns of genetic connectivity in invertebrates of temperate MPA networks

Temperate reefs are among the most threatened marine habitats due to impacts caused by high density of human settlements, coastal development, pollution, fisheries and tourism. Networks of marine protected areas (MPAs) are an important tool for ensuring long-term health and conservation of ecological processes in the marine environment. Design of the MPA network has to be based on deep understanding of spatial patterns of species distribution, and on the make-up of connectivity among populations. Most benthic invertebrates are sessile and/or sedentary in the adult phase, and their dispersal relies mainly on the gametes and/or larval behaviours. Genetic markers allow us to quantify gene flow and structuring among populations, and to infer patterns of genetic connectivity. Based on the information available in the peer reviewed literature on genetic connectivity in benthic invertebrates of temperate MPAs, we provide a comment about the gaps and the needs. Moreover, we propose a rationale to plan and optimise future studies on this topic. A conceptual framework for planning effective studies on genetic connectivity in an MPAs network is provided, including general recommendations on sampling design, key species and molecular markers to use.

Modelling species distributions with remote sensing data: bridging disciplinary perspectives

Modelling species distributions with remote sensing data: bridging disciplinary perspectives

Effect of Landscape Structure on Species Diversity

The effects of habitat fragmentation and their implications for biodiversity is a central issue in conservation biology which still lacks an overall comprehension. There is not yet a clear consensus on how to quantify fragmentation even though it is quite common to couple the effects of habitat loss with habitat fragmentation on biodiversity. Here we address the spatial patterns of species distribution in fragmented landscapes, assuming a neutral community model. To build up the fragmented landscapes, we employ the fractional Brownian motion approach, which in turn permits us to tune the amount of habitat loss and degree of clumping of the landscape independently. The coupling between the neutral community model, here simulated by means of the coalescent method, and fractal neutral landscape models enables us to address how the species–area relationship changes as the spatial patterns of a landscape is varied. The species–area relationship is one of the most fundamental laws in ecology, considered as a central tool in conservation biology, and is used to predict species loss following habitat disturbances. Our simulation results indicate that the level of clumping has a major role in shaping the species–area relationship. For instance, more compact landscapes are more sensitive to the effects of habitat loss and speciation rate. Besides, the level of clumping determines the existence and extension of the power-law regime which is expected to hold at intermediate scales. The distributions of species abundance are strongly influenced by the degree of fragmentation. We also show that the first and second commonest species have approximately self-similar spatial distributions across scales, with the fractal dimensions of the support of the first and second commonest species being very robust to changes in the spatial patterns of the landscape.