Species richness, environmental heterogeneity and area: a case study based on land snails in Skyros archipelago (Aegean Sea, Greece)

Aim To test the performance of the choros model in an archipelago using two measures of environmental heterogeneity. The choros model is a simple, easy‐to‐use mathematical relationship which approaches species richness as a combined function of area and environmental heterogeneity. Location The archipelago of Skyros in the central Aegean Sea (Greece). Methods We surveyed land snails on 12 islands of the archipelago. We informed the choros model with habitat data based on natural history information from the land snail species assemblage. We contrast this with habitat information taken from traditional vegetation classification to study the behaviour of choros with different measures of environmental heterogeneity. R² values and Akaike's information criterion (AIC) were used to compare the choros model and the Arrhenius species–area model. Path analysis was used to evaluate the variance in species richness explained by area and habitat diversity. Results Forty‐two land snail species were recorded, living in 33 different habitat types. The choros model with habitat types had more explanatory power than the classic species–area model and the choros model using vegetation types. This was true for all islands of the archipelago, as well as for the small islands alone. Combined effects of area and habitat diversity primarily explain species richness in the archipelago, but there is a decline when only small islands are considered. The effects of area are very low both for all the islands of the archipelago, and for the small islands alone. The variance explained by habitat diversity is low for the island group as a whole, but significantly increases for the small islands. Main conclusions The choros model is effective in describing species‐richness patterns of land snails in the Skyros Archipelago, incorporating ecologically relevant information on habitat occupancy and area. The choros model is more effective in explaining richness patterns on small islands. When using traditional vegetation types, the choros model performs worse than the classic species–area relationship, indicating that use of proxies for habitat diversity may be problematic. The slopes for choros and Arrhenius models both assert that, for land snails, the Skyros Archipelago is a portion of a larger biogeographical province. The choros model, informed by ecologically relevant habitat measures, in conjunction with path analysis points to the importance of habitat diversity in island species richness.     

The invasive dark falsemussel <Emphasis Type="Italic">Mytilopsis leucophaeata</Emphasis> (Bivalvia: Dreissenidae): a literature review

This paper reviews literature from the Americas and Europe on the dark falsemussel Mytilopsis leucophaeata (Conrad in J Acad Nat Sci Phila 6(2):256–268, 1831), including data collected in its native habitat in the Americas that appear as incidental information in published reports. Mytilopsis leucophaeata is a poorly studied dreissenid bivalve that is native to mainly oligohaline–mesohaline regions of estuaries in North America. In its native habitat, it usually occurs in very low numbers and has rarely been mentioned in field survey reports. However, occasionally in its native habitat and often in habitats where it has been introduced (as in Europe and Brazil), it may undergo population irruptions for no clear reason. This review describes habitat characteristics, environmental tolerances, and biological and ecological attributes of the species. The assembled information reveals the species to be euryhaline and eurythermal, with an unexplained ability to persist in its native estuaries even though it is relatively short-lived and usually uncommon.     

Field surveys and revegetation experiments show that simulation of topographical habitat features could improve the chances of successful restoration for the threatened succulent Juttadinteria albata

Species with highly restricted ranges are disproportionately at risk of extinction, particularly where habitat loss occurs as a result of mining. Postmining restoration of rare species populations is considered as an appropriate response to counter such threats, but requires a careful, evidence‐based, and information‐driven approach. The economically important diamond mining at Sendelingsdrif in the southern Namib Desert occurs in the highly diverse Succulent Karoo Biome and threatens a significant part of the population of the narrow endemic succulent plant species Juttadinteria albata. To decrease the inherent risks of restoring such a rare species, we studied the habitat features of premining J. albata populations and experimentally tested whether some features could assist future reintroductions in postmining substrates. Plots where J. albata occurred were mostly south‐ to west‐facing and had among others higher rock cover and steeper slopes than plots where J. albata plants were absent. A revegetation experiment, with J. albata cuttings that were established on postmining substrate mounds, revealed that plants on steeper slopes, facing south to west, grew faster than plants on other slopes and aspects. Slope and aspect are therefore important habitat properties to recreate when restoring J. albata populations. These, and other preferred habitat properties such as higher levels of organic C, should now be tested in larger‐scale field trials. Validation of habitat requirements of J. albata through the revegetation experiment has decreased the risks at least partially and provides additional empirical evidence of the importance of establishing reference conditions to enhance ecological restoration.     

基于生态位模型的艾比湖鹅喉羚生境评价

明确物种生境空间分布格局及其与环境因素的关系,对了解该物种的生境需求和适宜生境空间分布至关重要。生境评价和预测是对物种进行有效保护的基础。以鹅喉羚(Gazella subgutturosa)为研究对象,以其重要栖息地新疆博州艾比湖国家级湿地自然保护区为研究区域,选取115个鹅喉羚分布点数据和23个环境变量因子,应用MAXENT模型分析其生境空间分布及主要影响因子,划分了鹅喉羚在研究区域的适宜生境,并对它的栖息地特征进行了分析。探讨了鹅猴羚生境选择与环境因子的关系。结果表明:气温日较差是影响鹅喉羚生境分布的主要环境因子。植被类型,坡度和最干月降水量对艾比湖鹅喉羚的生境选择影响不大。除了温度和降水在内的19项生物气候变量是鹅猴羚选择生境的重要因素之外,海拔和坡向等地形特征也影响鹅猴羚的生境选择性。鹅喉羚的高度适宜生境区主要分布在研究区域的北部和东部,中度及低度适宜生境区则分布于高度适宜生境区的边缘,而非适宜生境区主要集中在西部地区。研究不仅提供了鹅喉羚在艾比湖的实际分布状况及其栖息地特征,也为鹅喉羚在栖息地方面的研究,即鹅猴羚的栖息地选择和环境因子的关系方面提供了一个重要的依据。     

基于模糊物元模型的桃儿七潜在地理分布研究

桃儿七(Sinopodophyllum hexandrum(Royle)Ying)为小檗科多年生草本植物,是我国传统濒危藏药。依据模糊物元模型建立桃儿七分布点位以及其产量数据与12个气候环境因子之间的模糊隶属函数,采用最大信息熵模型确定评价指标权重,利用GIS空间分析功能确定我国西部7省桃儿七生境适宜性空间分布。研究表明研究区桃儿七不适宜生境面积占研究区总面积的61.76%;低适宜生境占20.11%;中适宜生境占7.70%;高适宜生境占10.43%,主要集中在青藏高原东缘的四川、甘肃、青海境内次生植被丰富、地形复杂的高海拔地区。结果显示基于GIS与模糊物元构建的生境适宜性评价模型可以准确的对我国西部7省桃儿七生境适宜性做出科学综合评价,量化适宜生境面积和空间分布,为其资源保护和管理提供科学依据。     

Maximum entropy model: Estimating the relative suitability of cetacean habitat in the northern Savu Sea,Indonesia

An understanding of cetacean distribution is necessary to gain insights into crucial ecological processes for species conservation management. However, cetacean habitat preference and distribution in the northern Savu Sea, Indonesia, are still poorly understood. We use maximum entropy modeling with five environmental predictors to describe habitat preference and distribution of seven cetacean species in the northern Savu Sea. Our study confirms that static predictors are the most important variables in explaining habitat preferences of seven cetacean species in the northern Savu Sea. Seasonally, each cetacean species has a different environmental preference. Globicephala macrorhynchus prefers the open nearshore areas adjacent to deep waters. Stenella attenuata is associated with nearshore habitats and higher productivity areas. Stenella longirostris prefers nearshore habitat during coastal upwelling events. Tursiops truncatus prefers nearshore sheltered habitat. Grampus griseus habitats are highly related to depth and steep gradients around the isobaths of 200–1,000 m. Feresa attenuata are associated with deep waters and cooler sea temperature. Pseudorca crassidens prefers protective bays with productive waters. This study provides important information for reviewing marine spatial plans of the northern Savu Sea, specifically on managing species fisheries interaction, optimizing surveillance, and regulating marine traffic.     

The geographic distribution and ecological preferences of the American dog tick,Dermacentor variabilis (Say), in the U.S.A.

Equine piroplasmosis (EP), caused by two parasitic organisms, Theileria equi and Babesia caballi, is a tick‐borne disease of recent concern in horses in the U.S.A. Outbreaks of EP have been detected in Florida, Missouri, Kansas and Texas. In 2009, EP transmission in Texas occurred through the adults of two tick species, Amblyomma mixtum [formerly known as Amblyomma cajennense (Fabricius, 1787)] Koch (Ixodida: Ixodidae) and Dermacentor variabilis (Say) (Ixodida: Ixodidae), the American dog tick (ADT). In this study, we developed a continent‐scale map for the distribution of the EP vector species D. variabilis, using a presence‐only modelling approach to assess the habitat preferences of this tick. We used identification records from our tick geodatabase of locations in which the presence of the ADT had been noted. The potential distribution of the ADT in the U.S.A. was estimated from environmental factors using the maximum entropy approach based on localities in which there is a high probability of occurrence according to habitat suitability. Elevation and temperature were found to be biologically significant environmental variables influencing the presence of this tick species. Properly designed and constructed probability surfaces using maximum entropy offer one useful approach to the mapping of distribution ranges of tick species based on suitable habitat in the U.S.A.     

Distribution patterns of wintering sea ducks in relation to the North Atlantic Oscillation and local environmental characteristics

Twelve species of North American sea ducks (Tribe Mergini) winter off the eastern coast of the United States and Canada. Yet, despite their seasonal proximity to urbanized areas in this region, there is limited information on patterns of wintering sea duck habitat use. It is difficult to gather information on sea ducks because of the relative inaccessibility of their offshore locations, their high degree of mobility, and their aggregated distributions. To characterize environmental conditions that affect wintering distributions, as well as their geographic ranges, we analyzed count data on five species of sea ducks (black scoters Melanitta nigra americana, surf scoters M. perspicillata, white-winged scoters M. fusca, common eiders Somateria mollissima, and long-tailed ducks Clangula hyemalis) that were collected during the Atlantic Flyway Sea Duck Survey for ten years starting in the early 1990s. We modeled count data for each species within ten-nautical-mile linear survey segments using a zero-inflated negative binomial model that included four local-scale habitat covariates (sea surface temperature, mean bottom depth, maximum bottom slope, and a variable to indicate if the segment was in a bay or not), one broad-scale covariate (the North Atlantic Oscillation), and a temporal correlation component. Our results indicate that species distributions have strong latitudinal gradients and consistency in local habitat use. The North Atlantic Oscillation was the only environmental covariate that had a significant (but variable) effect on the expected count for all five species, suggesting that broad-scale climatic conditions may be directly or indirectly important to the distributions of wintering sea ducks. Our results provide critical information on species–habitat associations, elucidate the complicated relationship between the North Atlantic Oscillation, sea surface temperature, and local sea duck abundances, and should be useful in assessing the impacts of climate change on seabirds.     

Acoustic telemetry survey of the dusky grouper (Epinephelus marginatus) in the Marine Reserve of Cerbère-Banyuls: informations on the territoriality of this emblematic species

The Marine Reserve of Cerbère-Banyuls represents a refuge for dusky grouper populations (Epinephelus marginatus). Density survey and observation of the reproductive behavior of this species have been conducted there for the last 30 years. However, information on the behavior or habitat utilization for this species during winter time is limited. We conducted acoustic telemetry surveys from September 2005 to June 2006 in the Marine Reserve of Cerbère-Banyuls for a dusky grouper population. Six groupers were tagged and followed within the integral reserve and in the adjacent partial reserve. The results from the tracking of these individuals indicated that the largest dusky groupers are sedentary fishes with a high degree of site fidelity and a high sensitivity to variations of environmental conditions such as storms. This together with the life history characteristics of this species encourages the conservation and the protection of essential habitats of this species. Acoustic tracking coupled to the use of a fixed Kernel can be proposed to follow fish populations. To cite this article: J. Pastor et al., C. R. Biologies 332 (2009).     

新疆卡拉麦里山有蹄类野生动物自然保护区啮齿动物群落多样性及其与环境因子的关系

啮齿动物的群落结构受生态环境特征影响,并能反映环境变化规律。为探讨啮齿动物群落多样性及其与环境因子间的关系,利用铗捕法获得了新疆卡拉麦里山有蹄类野生动物自然保护区9种生境类型的环境因子及啮齿动物群落结构数据。2019-2020年春、夏季,共布设样地291块,有效铗日55269个,调查总面积176.875 km²,记录了啮齿类分布的12个环境因子。捕获啮齿动物419只,分属1目4科10属12种,优势种为三趾跳鼠（Dipus sagitta）和五趾跳鼠（Allactaga sibirica）,分别占捕获总个体数的34.13%和27.68%。分析结果显示,卡山自然保护区啮齿类捕获率最高的生境类型为沙漠（2.18%）;捕获鼠种的主要分布型为耐旱型（98.09%）。12个环境因子在9个生境类型中均呈极显著差异（P<0.01）,说明该保护区啮齿动物分布的生境异质性高。冗余分析表明,海拔高度、植被种类、灌木盖度和灌木高度是决定啮齿动物群落结构最主要的4个环境因子,其中植被种数与啮齿类群落多样性呈正相关,随着植被种数数值的增加,除优势度指数外,其它多样性指数随之增加。     

Habitat distribution modelling,under the present climatic scenario,of the threatened endemic Iberian Delphinium fissum subsp. sordidum (Ranunculaceae) and implications for its conservation

We modelled the potential habitat of a threatened species D. fissum subsp. sordidum, an endemic hemicryptophyte with a disjunct distribution in the Iberian Peninsula. Maxent was used to predict the subspecies habitat suitability by relating field sample-based distributional information with environmental and topographic variables. Our results suggest that the model performed well, predicting with high accuracy the current distribution of the species. The variables that most contributed to the model were Mean Temperature of Wettest Quarter (MTWtQ), Precipitation of Warmest Quarter (PWmQ), Temperature Annual Range (TAR) and Slope (Slo). These variables are biological significant for the taxon, as they have decisive influence in the critical stages of germination and fruiting. The current and potential distributional areas identified by the model fall mainly in regions with some degree of environmental protection, with some exceptions. A recovery plan for the species should be considered. Species Distribution Modelling cannot substitute long-term monitoring programmes, yet it is a useful tool for identifying appropriate areas of taxon occurrence, and thus allow for efficient use of the economic and human resources.     

Habitat use by five sympatric Australian freshwater crayfish species (Parastacidae)

1. The Grampians National Park in Victoria is a ‘hot spot’ for freshwater crayfish diversity, with seven species from six genera occurring in sympatry. Few studies have examined how multiple species of freshwater crayfish co‐exist across landscapes consisting of a mosaic of perennial and seasonal habitats. Despite their endemicity and likely key role in freshwaters, the ecology and biology of these crayfish remains unknown. 2. This study determined the distribution and habitat use of five crayfish species (Euastacus bispinosus, Cherax destructor, Geocharax falcata, Gramastacus insolitus and Engaeus lyelli). Seasonal sampling surveys ascertained whether crayfish distribution was related to habitat type, environmental or physicochemical variables, catchment or season. 3. Distribution was directly related to habitat type and the environmental and physicochemical variables that characterised habitats. Engaeus lyelli, G. falcata and G. insolitus occurred predominantly in floodplain wetlands and flooded vegetation habitats, E. bispinosus occurred only in flowing soft‐sediment channels and C. destructor was found in all catchments and habitat types studied. Gramastacus insolitus co‐occurred with G. falcata at all sites except two, so no distinct habitat separations were apparent for these two species. 4. A high percentage cover of boulders was the best indicator of crayfish absence, and discriminated between habitat types and crayfish species: it was probably a surrogate for a larger range of environmental and physicochemical variables. Catchment and season did not affect crayfish distribution. 5. These crayfish species varied in their degree of habitat specialisation from strongly generalist (C. destructor) to occupying only a specific habitat type (E. bispinosus). Some species appeared specialised for seasonal wetlands (G. insolitus and G. falcata). Overlap in site occupancy also varied: G. insolitus and G. falcata distributions were strongly associated, whereas C. destructor appeared to occur opportunistically across habitats, both alone and co‐occurring with all the other species. 6. Management strategies to conserve multiple species of crayfish co‐existing within landscapes will need to incorporate a range of perennial and seasonal habitat types to ensure sufficient space is available for species to maintain different occupancy patterns. Given that water resources are under increasing pressure and are strongly regulated within the Grampians National Park, this may present a conservation challenge to water managers in this location.     

Occurrence of Larca lata H.J. Hansen (Pseudoscorpionida: Garypidae) and Allochernes wideri C.L. Koch (Pseudoscorpionida: Chernetidae) in tree hollows in relation to habitat quality and density

Many beetles associated with old trees are on national red lists, but pseudoscorpions living in similar habitats have received little attention. This study reports the habitat and occurrence patterns of two species of pseudoscorpions living in hollow trees. Their occurrence has been assessed by sieving wood mould from 274 oaks in southeastern Sweden and from museum specimens collected in Sweden. Larca lata is confined to hollow oaks with a large girth and a plentiful supply of wood mould. Allochernes wideri is much less particular about wood mould volume, trunk diameter and tree species. Larca lata inhabits hollow trunks with characteristics that are typical of very old trees, whereas A. wideri predominantly occurs in trunks in an earlier stage of hollow formation. Larca lata was almost exclusively found in larger assemblages of hollow oaks, which suggests long-term survival may be difficult when the network of suitable hollow trees is too sparse. Larca lata is a rare species in Europe and probably vulnerable to extinction, since it is dependent on a habitat which has declined severely in the last few centuries.     

Biogenic habitat creation affects biomass–diversity relationships in plant communities

Biogenic habitat creation refers to the ability of some organisms to create, maintain or destroy habitats. These habitat changes affect species diversity of natural communities, but it remains to be elucidated if this process also affects the link between ecosystem functions and species diversity. Based on the widely accepted positive relationships between ecosystem functions and species diversity, we hypothesize that these relationships should be different in biogenically created habitat patches as compared to unmodified habitat patches. We tested this hypothesis by assessing the effects of a high-Andean cushion plant, Azorella madreporica, which creates habitat patches with different environmental conditions than in the surrounding open areas with reduced vegetation cover. We used observational and experimental approaches to compare the plant biomass–species richness relationships between habitat patches created by A. madreporica cushions and the surrounding habitat without cushion plants. The observational assessment of these relationships was conducted by counting and collecting plant species within and outside cushion patches. In the experiment, species richness was manipulated within and outside cushion patches. The cushion plant itself was not included in these approaches because we were interested in measuring its effects. Results of both approaches indicated that, for a given level of species richness, plant biomass within cushions was higher than in the surrounding open areas. Furthermore, both approaches indicated that the shape of plant biomass–species richness curves differed between these habitat types. These findings suggest that habitat modifications performed by A. madreporica cushions would be positively affecting the relationships between ecosystem functions and species diversity.     

Habitat size determine algae biomass in tank-bromeliads

The primary goal of this study was to evaluate the relative importance of habitat physical properties, bottom-up and top-down factors, and their interaction on algae biomass in tank-bromeliads. We sampled algae biomass (chlorophyll-a concentration), micro-metazoan density, mosquito abundance, and several environmental variables, including nutrient concentrations and characteristics of the habitat physical structure, in a survey of 64 tank-bromeliads of four different species (Aechmea nudicaulis, Aechmea lingulata, Neoregelia cruenta, and Vriesea neoglutinosa). We analyzed the complete and individual bromeliad species datasets using an information-theoretic model selection approach (Akaike’s information criterion). Bromeliad species, maximum water volume, and bromeliad diameter comprised the best model for determining chlorophyll-a concentrations for the complete dataset. The maximum water volume also comprised the best model to explain chlorophyll-a concentrations in three of four bromeliad species datasets. Interactions between consumers and nutrient concentration were included in the subsequent models, but they were not statistically significant. Taken together, these results demonstrate that the impact of habitat size on the associated autotrophic biomass occurs possibly via changes in community susceptibility to disturbances, particularly drought. We can conclude that habitat size is more important than resource availability or herbivory on phytotelm autotrophic biomass regulation in these natural microcosms.     

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

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

Grouse moor management: habitat and conservation implications for invertebrates in southern Scotland

The distribution of ground beetle, rove beetle, spider and plant bug species assemblages, and the occurrence of other beetle species, was investigated in a five-year survey of a grouse moor in the Scottish borders, some of which was managed by burning, cutting and herbicide application. Multivariate analyses were used to assess the relationship between assemblage distribution and a number of environmental variables. The management of dry Calluna moor had a positive effect on the habitat diversity for ground beetles and plant bugs but had little effect on rove beetles and spiders. A total of 39 nationally rare and scarce species (38 beetle, 1 plant bug) was recorded in the survey. The most important habitat present was on streamside sites, especially sediment. A number of these rarer species were restricted to sites managed by burning and cutting but other species were only found on unmanaged wet Calluna moor. Molinia-dominated moor was generally of poorer quality than Calluna sites, with fewer rare and scarce species and lower site rarity values based on the ground beetle species recorded. The highest median site rarity scores were for dry, open, managed Calluna sites. In order to maximise both habitat diversity and the incidence of rare and scarce species on grouse moor, a mosaic of both managed and undisturbed patches differing in soil characteristics, plant composition and vegetation structure appears to be required.     

Quantifying the activity levels and behavioural responses of butterfly species to habitat boundaries

1. The ability of species' to undergo climate‐driven range shifts across fragmented landscapes depends on their dispersal ability as well as the structure of the landscape. For species' range shifts to occur, individuals must first leave suitable habitat to seek new habitat; this is likely to depend on the rate of movement of individuals within habitat and the likelihood that a boundary is crossed, once it is encountered. For three species of butterfly with contrasting histories of recent range expansion, we examined the propensity of individuals to move within a habitat and their responses to habitat boundaries. 2. We quantified the extent to which Plebejus argus (Linnaeus) (a declining habitat specialist), Aricia agestis (Schiffermuller) (an expanding generalist) and Polymmatus icarus (Rottemburg) (a geographically ubiquitous generalist) crossed habitat boundaries into unsuitable habitat and moved within suitable habitat. The observed movement was then related to individual and environmental conditions. 3. Species differed in their activity levels in accordance within their recent distribution patterns (P. icarus > A. agestis > P. argus). Our results for P. argus suggest that movement may be motivated by nectar‐seeking, and that males generally move more than females. All three species tended to avoid crossing habitat boundaries; however the proportion of individuals crossing habitat boundaries did not differ significantly among species. 4. We conclude that levels of activity within a habitat, which will affect the frequency with which individuals encounter habitat boundaries, rather than behavioural responses to the boundaries, may be important drivers of distribution change.     

Change in cyanobacterial biovolume due to preservation by Lugol's Iodine

Cyanobacterial biovolume is used as a guide to the public health risk from these organisms for users of potable and recreational waters. Most routine surveillance programs preserve phytoplankton samples before analysis. We tested the effect of Lugol's Iodine, a common preservative, on the cell biovolume of four common freshwater cyanobacteria, Microcystis aeruginosa, Anabaena circinalis, Cylindrospermopsis raciborskii and Aphanocapsa incerta. Linear dimensions and cell area were measured with an image analyser. All four species shrank after preservation. The magnitude of shrinkage varied with species and preservation time but was not affected by Lugol's concentration. The maximum shrinkage in each species was a 30–40% reduction compared to the live cell biovolume. These results suggest shrinkage can be a greater source of uncertainty in estimating the biovolume of toxigenic cyanobacteria in aquatic environments than natural variability in the cell dimensions, instrument precision or cell counting. Standardised cyanobacterial biovolume lists based on agreed geometric shapes and formulae would improve the value of this information for public health risk assessment.