Ecogeographical Variables Research Articles

Ontogenetic changes in intralimb proportions in a Romano‐Christian period sample from the Dakhleh Oasis, Egypt

The purpose of this study is to document the appearance of adult patterns in intralimb indices during ontogeny in a skeletal sample from the Kellis 2 cemetery, Dakhleh Oasis, Egypt. In addition, this study explores evolvability in intralimb indices to understand relative differences in sensitivity to ecogeographic variables. Brachial and crural indices were compared across age cohorts with Welch's ANOVA tests and post-hoc Dunnett-Tukey-Kramer (DTK) pairwise multiple comparison tests. Spearman's rank correlation coefficients were used to examine developmental conservation and evolvability in intralimb proportions. Brachial and crural indices are greatest in the fetus/perinate cohort as compared to all other cohorts, decrease during infancy and early childhood, and increase during middle/late childhood. The adult pattern in the brachial index is first evident in infancy, but is not maintained throughout development. Conversely, the adult pattern in the crural index appears during early childhood and is maintained throughout development. The brachial index shows a higher degree of evolvability than the crural index in utero. The shifting pattern in intralimb proportions during development in the Kellis 2 sample is similar to that previously reported from globally diverse samples, which likely reflects the differential growth acceleration of proximal and distal intralimb skeletal elements during ontogeny. The brachial index may be more responsive to climatic conditions while the crural index may be more conserved due to functional demands. The data indicate that Kellis 2 juveniles were under strong selective pressures from climatic factors.

Ecogeography of the genus Sticta (lichenized Ascomycota: Lobariaceae) in Colombia

Colombia is a megadiverse country, but with a substantial gap in the taxonomic and ecological knowledge of fungi and lichens. Thus, the objective of the present study was an ecogeographical analysis of the Sticta species in Colombia. The data included macrodistribution (with respect to mountain ranges and life zones) and microhabitat preferences (light, substrate) and were obtained from field work and herbarium collection labels (completed by comparison with modern geographic and vegetation maps), for 103 species of Sticta currently recognized in Colombia (plus seven additional biotypes with different photobionts or reproductive mode). Using non-metric multidimensional scaling (NMS), correlations between ecogeographical variables and species were established, and ecotypes were delimited. Colombian species of Sticta showed distinct distribution patterns relative to altitude, mountain ranges, life zones, as well as light exposure and substrate, forming several distinct groups. Cyanobacterial species tend to have wider distribution ranges than green algal species. We concluded that the orogeny of the Northern Andes substantially affected speciation of the genus Sticta and its ecogeographical differentiation.

Genetic characterization of Turkish cultivated emmer wheat [Triticum turgidumL. ssp.dicoccon(Schrank) Thell.] landraces based on isoenzyme analysis

Nineteen landrace populations of Turkish cultivated emmer wheat [Triticum turgidum L. ssp. dicoccon (Schrank) Thell.] were characterized in terms of three isoenzyme [Endopeptidase-1, Aminopeptidase-1 and Aminopeptidase-2] systems, by isoelectric focusing gel electrophoresis. For overall loci, the mean number of alleles and effective alleles were observed as 2.00 and 1.37, respectively. The mean value of gene diversity and average gene diversity, in overall loci, were detected as 0.23 and 0.07, respectively. Actual genetic differentiation and gene flow between different populations were calculated as 0.19 and 0.11, respectively. Pearson's correlation and multiple regression analyses indicated that eco-geographical variables have significant effects on isoenzyme genetic diversity. Landraces that have desirable agronomical and immunological resistance traits that makes them adaptable to climate change and different eco-geographical conditions are important genetic resources to utilise for the improvement of future crops of modern wheat varieties. There is a need to assess the genetic structure and genetic composition of important agronomical characters and to determine the magnitude of the genetic diversity currently conserved in the germplasm of landraces, both in farm fields and in ex situ collections and finally, strategies for the effective use of landraces, particularly of emmer wheat, should be planned and implemented in Turkey were discussed.

Inter-specific and seasonal comparison of the niches occupied by small cetaceans off north-west Iberia

Knowledge of species' ecological niches can be used to assess ecological interactions between different taxa. Sixteen species of cetaceans have been recorded in Galician waters and niche partitioning is expected to occur among these species in order to allow them to co-exist. In this study, the niches occupied by five of the most commonly encountered odontocete species off Galicia (NW Iberia) were compared, based on seven ecogeographic variables, using a PCA-based methodology and Classification trees. Significant differences in niche centres and niche widths were found among all the species. During the summer, the harbour porpoise occupied the narrowest and most differentiated niche when compared to the rest of the species. Three species could be compared during the winter, when long-finned pilot whales preferred colder and less variable water temperatures than did common dolphins. Seasonal differences in habitat preferences were found for bottlenose dolphins. A higher degree of specialisation was found during the summer, resulting in stronger differences in habitat use in this season, which may be related to an increment in resource availability during the upwelling period (April–September). The PCA-based methodology used in this study provides an effective multivariate approach to explore niche partitioning between co-existing species.

Projecting current and potential future distribution of the Fire-bellied toad Bombina bombina under climate change in north-eastern Germany

Environmental change is likely to have a strong impact on biodiversity, and many species may shift their distribution in response. In this study, we aimed at projecting the availability of suitable habitat for an endangered amphibian species, the Fire-bellied toad Bombina bombina, in Brandenburg (north-eastern Germany). We modelled a potential habitat distribution map based on (1) a database with 10,581 presence records for Bombina from the years 1990 to 2009, (2) current estimates for ecogeographical variables (EGVs) and (3) the future projection of these EGVs according to the statistical regional model, respectively, the soil and water integrated model, applying the maximum entropy approach (Maxent). By comparing current and potential future distributions, we evaluated the projected change in distribution of suitable habitats and identified the environmental variables most associated with habitat suitability that turned out to be climatic variables related to the hydrological cycle. Under the applied scenario, our results indicate increasing habitat suitability in many areas and an extended range of suitable habitats. However, even if the environmental conditions in Brandenburg may change as predicted, it is questionable whether the Fire-bellied toad will truly benefit, as dispersal abilities of amphibian species are limited and strongly influenced by anthropogenic disturbances, that is, intensive agriculture, habitat destruction and fragmentation. Furthermore, agronomic pressure is likely to increase on productive areas with fertile soils and high water retention capacities, indeed those areas suitable for B. bombina. All these changes may affect temporary pond hydrology as well as the reproductive success and breeding phenology of toads.

Habitat and distribution of post-recruit life stages of the squid Loligo forbesii

This study models habitat preferences of the squid Loligo forbesii through its post-recruitment life cycle in waters around Scotland (UK). Trawl survey and market sample data from 1985 to 2004 are used to model seasonal habitats of immature, maturing and mature squid (maturity being inferred from size and season). Squid presence–absence and catch rate in areas of presence were analysed using generalised additive models, relating spatiotemporal patterns of distribution and abundance to ecogeographic variables. For all maturity classes, higher abundance in winter and spring (i.e., quarters 1 and 2) was associated with deeper water while higher abundance in summer and autumn (quarters 3 and 4) was associated with shallower water, consistent with seasonal onshore-offshore migrations but suggesting that most spawning may take place in deeper waters. The preferred SST range was generally 8–8.75°C while preferred salinity values were below 35‰ in winter and summer and above 35‰ in spring and autumn. Squid were positively associated with gravel substrate and negatively associated with mud. Seasonal changes in habitat use were more clearly evident than changes related to inferred maturity, although the two effects cannot be fully separated due to the annual life cycle. Habitat selection for this species can be satisfactorily modelled on a seasonal basis; predictions based on such models could be useful for fishers to target the species more effectively, and could assist managers wishing to protect spawning grounds. The extent to which this approach may be useful for other cephalopods is discussed.

Estimating patterns of reptile biodiversity in remote regions

AbstractAimThe incompleteness of information on biodiversity distribution is a major issue for ecology and conservation. Researchers have made many attempts to quantify the amount of biodiversity that still remains unknown. We evaluated whether models that integrate ecogeographical variables with measures of the effectiveness of sampling can be used to estimate biodiversity patterns (species richness) of reptiles in remote areas that have received limited surveys.LocationThe Western Palaearctic (Europe, Northern Africa, the Middle East and Central Asia).MethodsWe gathered data on the distribution of turtles, amphisbaenians and lizards. We used regression models integrating spatial autocorrelation (spatial eigenvector mapping and Bayesian autoregressive models) to analyse species richness, and identified relationships between species richness, ecogeographical features and large‐scale measures of accessibility.ResultsThe two regression techniques were in agreement. Known species richness was dependent on ecogeographical factors, peaking in areas with high temperature and annual actual evapotraspiration, and intermediate cover of natural vegetation. However, richness declined sharply in the least accessible areas. Our models revealed regions where reptile richness is likely to be higher than currently known, particularly in the biodiversity hotspots in the south of the Arabian Peninsula, the Irano‐Anatolian region, and the Central Asian mountains. An independent validation data set, with distribution data collected recently throughout the study region, confirmed that combining accessibility measures with ecogeographical variables allows a good estimate of reptile richness, even in remote areas that have received limited monitoring so far. Some remote regions that support very rich communities are covered very little by protected areas.Main conclusionsIntegrating accessibility measures into species distribution models allows biologists to identify areas where current knowledge underestimates the actual richness of reptiles. Our study identifies regions requiring future biodiversity research, proposes a novel approach to biodiversity prediction in poorly studied areas, and identifies potential regions for conservation.

Factors influencing the distribution of leopard in a semiarid landscape of Western India

Previously, factors governing distribution of leopard (Panthera pardus fusca) in forest habitats of the Indian subcontinent were unknown. The present study assessed the influence of different ecogeographic variables determining the distribution of leopards in and around Sariska Tiger Reserve through MaxEnt habitat suitability model based on camera trapping method. Camera trapping was used to collect presence/absence information in the study area from December 2008 to June 2010. Information of 11 macrohabitat characteristics and variables (habitat types, prey species, Normalized Difference Vegetation Index (NDVI), elevation, livestock, village, water source, etc.) were collected along with leopard presence data. The probability of presence of leopards increased with decreasing distance to water and increasing encounter rate of peafowl (Pavo cristatus), chital (Axis axis), sambar (Rusa unicolor), and wild pig (Sus scrofa). It was found that the probability of presence of leopards increased with increasing area of Zizyphus mixed forest patches and NDVI. Results of this study showed that the probability of presence of leopards was higher in habitat types with intermediate cover, high wild prey base, and water sources. They also indicated that leopards are not always ‘generalists’ showing some degree of specialization, at least in their choice of habitat, and this information is useful for conserving leopard in human-dominated landscapes.

Molecular phylogeny and ecogeography of Onobrychis viciifolia Scop. (Fabaceae) based on nrDNA ITS sequences and genomic ISSR fingerprinting

AbstractIn this study 40 specimens from 8 representative Iranian populations of Onobrychis viciifolia SCOP. were collected from their natural habitats. The specimens were biometrically assessed using 43 quantitative and 15 qualitative morphological characters. At each sample site we recorded ecogeographical variables. In order to evaluate the difference between the variation due to phenotypic responses and genetic adaptation, we generated nucleotide sequence data from the internal transcribed spacer of the nuclear rDNA genes (ITS) and carried out genomic fingerprints using inter‐simple sequence repeat PCR (ISSR). Cluster analysis of morphological characters divided the eight populations into three major groups. Leaf length, leaflet length and width, calyx length, plant height, and stem length were introduced as diagnostic characters for three different morphological groups. Furthermore, canonical correspondence analysis (CCA) of ecogeographical data showed correlations between morphological variations and ecogeographical factors. Clay%, saturation percentage (SP), total neutralizing value (TNV%), texture, minimum temperature, and geographic separation were the main environmental variables associated with morphological groups of O. viciifolia. ISSR analysis revealed three main groups which are in correspondence with morphological groups, indicating that the three morphological groups have been shaped by genetic and phenotypic responses to environmental conditions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Habitat Suitability Model for Black Rhinoceros in Augrabies Falls National Park, South Africa

To assist with identifying land for reintroduction, a habitat suitability model (HSM) for black rhinoceros (Diceros bicornis) was developed in the arid Augrabies Falls National Park, South Africa, from records of sightings, feeding trails and dung middens. Logistic regression and Bayesian Information Criterion were employed to construct and select the best HSM from >35 eco-geographical variables. The modelled and the observed distributions of black rhinos did not differ (P = 0.323) and k-fold cross-validation confirmed the model's ability to predict the distribution of independent data. The HSM consisted of five variables: availability and equitability of three preferred foods, distance to roads, habitat heterogeneity, slope and shade. The variables ‘distance to water’ and ‘rockiness’ were also included in the confidence set of models. Only 50% of the study area had a habitat suitability exceeding 11%, but featured 89% of rhino locations. Of 10 vegetation communities, two with high volumes of favourite foods were preferred. Feeding areas with a high density of preferred food plants were also highly preferred. The riverine vegetation community was not preferred, because its abundant browse was not of the preferred species. The apparent avoidance of roads warrants more research and the attention of park managers.

High-molecular-weight glutenin subunit variation in Turkish emmer wheat [Triticum turgidum L. ssp. dicoccon (Schrank) Thell.] landraces

The genetic diversity of high-molecular-weight (HMW) glutenin subunits in 18 cultivated emmer wheat landrace populations, originating from Turkey, was investigated using sodium dodecyl sulphate polyacrylamide gel electrophoresis. The mean number of alleles (n a) and effective alleles (n ea) were observed as 3.67 and 1.53, respectively. The mean values of expected heterozygosity (gene diversity) (H e) and average heterozygosity (H e,av) were calculated as 0.31 and 0.12, respectively. Actual genetic differentiation (D) and gene flow (N m) between the different populations were observed as 0.24 and 0.16, respectively. Statistical analysis of Pearson’s correlation, multiple regressions and principal component analysis indicated that eco-geographical variables have a significant effect on HMW-glutenin diversity. Considering the dramatic decrease in genetic diversity of modern high-yielding cultivars, the conservation of genetic diversity in these wheat landraces, and in other old cultivars, is important for improving modern monocultures and their ability to resist biotic and abiotic conditions caused by climate changes, thus generating a wide adaption to a variety of environmental conditions. Adoptation measures for germplasm conservation of Turkish emmer wheat landraces and utilisation of their germplasm for improvement of modern wheat varieties were discussed in this study.

Predicting successful replacement of forest invaders by native species using species distribution models: The case of Pittosporum undulatum and Morella faya in the Azores

Invasive alien species have taken the place of native forest species worldwide, and particularly in island systems like the Azores. Species distribution models could be used to support the design of control strategies, including the definition of target areas. In this study we used species distribution modelling, performed with the ecological-niche factor analysis (ENFA) approach. Pittosporum undulatum is the most widespread woody invader in the Azores where it is considered as one of the priority species for control actions. On the other hand, Morella faya is a native woody plant facing several threats, including plant invasions. This paper aims to evaluate whether and where areas currently occupied by P. undulatum could also be favorable habitat for M. faya, thus providing support for future management actions. Occurrence data on P. undulatum and M. faya from a forest inventory were randomly split into training and testing datasets. Twenty six ecogeographical variables were used together with the training datasets in modelling. The modelling results were validated based on the continuous Boyce curve calculated with the testing datasets. We selected and compared the models of the highest predictive power and robustness for both species to define where M. faya could inhabit areas currently occupied by P. undulatum. The two species have quite similar environmental preferences, which correspond mainly to coastal lowlands and forested habitats characterized by relatively high temperature and wide ranges of low relative humidity values. The main difference between both species is that M. faya was considered more specialized according to current data. M. faya could potentially be used to replace P. undulatum in up to 24% of the Azorean area currently invaded, mostly in São Jorge and Pico Islands. According to our results, the ENFA modelling approach revealed to be a useful tool in the design of more efficient management strategies for woody plant invaders.

Environmental Effects on Vertebrate Species Richness: Testing the Energy, Environmental Stability and Habitat Heterogeneity Hypotheses

BackgroundExplaining species richness patterns is a central issue in biogeography and macroecology. Several hypotheses have been proposed to explain the mechanisms driving biodiversity patterns, but the causes of species richness gradients remain unclear. In this study, we aimed to explain the impacts of energy, environmental stability, and habitat heterogeneity factors on variation of vertebrate species richness (VSR), based on the VSR pattern in China, so as to test the energy hypothesis, the environmental stability hypothesis, and the habitat heterogeneity hypothesis.Methodology/Principal FindingsA dataset was compiled containing the distributions of 2,665 vertebrate species and eleven ecogeographic predictive variables in China. We grouped these variables into categories of energy, environmental stability, and habitat heterogeneity and transformed the data into 100×100 km quadrat systems. To test the three hypotheses, AIC-based model selection was carried out between VSR and the variables in each group and correlation analyses were conducted. There was a decreasing VSR gradient from the southeast to the northwest of China. Our results showed that energy explained 67.6% of the VSR variation, with the annual mean temperature as the main factor, which was followed by annual precipitation and NDVI. Environmental stability factors explained 69.1% of the VSR variation and both temperature annual range and precipitation seasonality had important contributions. By contrast, habitat heterogeneity variables explained only 26.3% of the VSR variation. Significantly positive correlations were detected among VSR, annual mean temperature, annual precipitation, and NDVI, whereas the relationship of VSR and temperature annual range was strongly negative. In addition, other variables showed moderate or ambiguous relations to VSR.Conclusions/SignificanceThe energy hypothesis and the environmental stability hypothesis were supported, whereas little support was found for the habitat heterogeneity hypothesis.

Definition of critical summer and fall habitat for bowhead whales in the eastern Canadian Arctic

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 17:1-16 (2012) - DOI: https://doi.org/10.3354/esr00403 Theme Section: Beyond marine mammal habitat modeling: applications for ecology and conservation Definition of critical summer and fall habitat for bowhead whales in the eastern Canadian Arctic Benjamin Wheeler1,*, Marianne Gilbert2, Stephen Rowe3 1Hemmera, 1380 Burrard St., Suite 250, Vancouver, British Columbia V6Z 2H3, Canada 2Stantec, 4370 Dominion St., 5th floor, Burnaby, British Columbia V5G 4L7, Canada 3Integrated Informatics Inc., 268 Duckworth Street, St. John’s, Newfoundland A1C 5W1, Canada *Email: wheelerbena@gmail.com ABSTRACT: Bowhead whale Balaena mysticetus critical habitat was identified as a key information gap by the Eastern Arctic Bowhead Whale Recovery Team. To fill this gap, data on eastern Canadian Arctic (ECA) bowhead whales and their habitat were collected and analyzed. We selected governmental, private, and historical whaling bowhead location datasets which differed in temporal and spatial extent, sample size, and quality. Sufficient data were available only for the ‘reduced-ice’ period (June to October) and pooled by month. Data for 6 ecogeographical variables (EGVs) were integrated into a geographical information system (GIS): sea surface temperature, chlorophyll, ice, depth, slope, and distance to shore. A monthly ecological niche factor analysis was performed for each whale and EGV dataset to determine habitat suitability in the ECA. Eleven habitat suitability models were produced, and a composite map of predicted high suitability habitat, for all 5 months, was developed. Twenty-one areas within the ECA were identified as highly suitable habitat and ranked according to analytical confidence. Six critical habitats were identified and are supported by recent scientific evidence and Inuit knowledge. Recently, the population estimate, conservation status, and management of the Eastern Canada−West Greenland bowhead population have changed dramatically (bowhead whales of this population also inhabit the ECA). In parallel, evidence of ecological change from climate warming has increased and associated loss of sea ice is anticipated to increase interactions between bowheads and anthropogenic activity. As envisioned by the recovery team, this study provides resource managers with a timely tool for population recovery, conservation, and protection. KEY WORDS: Eastern Canadian Arctic · Bowhead whale · Critical habitat · Ecological niche modeling · Ecological niche factor analysis · Habitat suitability · Species recovery · Management · Climate change Full text in pdf format NextCite this article as: Wheeler B, Gilbert M, Rowe S (2012) Definition of critical summer and fall habitat for bowhead whales in the eastern Canadian Arctic. Endang Species Res 17:1-16. https://doi.org/10.3354/esr00403 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 17, No. 1. Online publication date: April 12, 2012 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2012 Inter-Research.

Habitat preferences and evidence for niche partitioning amongst cetaceans in the waters between Gabon and Angola, eastern tropical Atlantic

The habitat preferences and niches of eight cetacean species inhabiting eastern tropical Atlantic waters between Angola and Gabon (1°N–11°S latitude) were examined. A total of 2873 cetacean sightings, recorded between January 2004 and June 2009, was assigned to 10 × 10 km grid cells and linked to four ecogeographical variables (EGVs): water depth, seabed slope, sea surface temperature (SST) and relative frontal strength. Classification trees revealed that the habitat preferences (in terms of the habitats sampled) of most species were primarily determined by SST (for Bryde's whale, sperm whale, short-finned pilot whale and common dolphin) and water depth (for Risso's dolphin, bottlenose dolphin and Atlantic spotted dolphin). Seabed slope was the most important EGV describing the presence of the striped dolphin. A principal component analysis was used to compare the niches of the species with respect to the four EGVs. Nineteen species pairs (68%) differed significantly in median principal component (PC) score for the first PC axis, suggesting differences in their niche centres for that axis. Sixteen species pairs (57%) differed significantly in PC score variance suggesting differences in the niche widths along the first PC axis. Water depth and SST were the most important variables for the first PC axis. Together, these results suggest that cetacean species inhabiting the eastern tropical Atlantic exhibit interspecific variation in their habitat preferences, and so differ in the niches that they occupy. These differences are most likely related to variation in prey species and foraging strategy.

Parapatric species and the implications for climate change studies: a case study on hares in Europe

AbstractParapatry is a biogeographical term used to refer to organisms whose ranges do not overlap, but are immediately adjacent to each other; they only co‐occur – if at all – in a narrow contact zone. Often there are no environmental barriers in the contact zones, hence competitive interaction is usually advocated as the factor that modulates species distribution ranges. Even though the effects of climate change on species distribution have been widely studied, few studies have explored these effects on the biogeographical relationships between closely related, parapatric, species. We modelled environmental favourability for three parapatric hare species in Europe – Lepus granatensis, L. europaeus and L. timidus – using ecogeographical variables and projected the models into the future according to the IPCC A2 emissions scenario. Favourabilities for present and future scenarios were combined using fuzzy logic with the following aims: (i) to determine the biogeographical relationships between hare species in parapatry, that is L. granatensis/L. europaeus and L. europaeus/L. timidus and (ii) to assess the effects of climate change on each species as well as on their interspecific interactions. In their contact area L. granatensis achieved higher favourability values than L. europaeus, suggesting that if both species have a similar population status, the former species may have some advantages over the latter if competitive relationships are established. Climate change had the most striking effect on the distribution of L. timidus, especially when interspecific interactions with L. europaeus were taken into account, which may compromise the co‐existence of L. timidus. The results of this study are relevant not only for understanding the distribution patterns of the hares studied and the effects of climate change on these patterns, but also for improving the general application of species distribution models to the prediction of the effects of climate change on biodiversity.

Morphological diversity and phenotypic plasticity in the threatened British white‐clawed crayfish (Austropotamobius pallipes)

ABSTRACT Relocation of threatened populations is a common method employed in conservation. However, environmental differences in the new habitat may reduce the survival of relocated populations, while phenotypic plasticity may enhance the likelihood of establishment of relocated populations in their novel environment. Conservation of the British white‐clawed crayfish (Austropotamobius pallipes; IUCN Red Data List – Endangered) often involves relocation of threatened populations into isolated ponds (Ark Sites), where risk of competition with invasive crayfish is minimized. In this study, the morphology (using 12 morphometric variables) of A. pallipes in wild populations was investigated with respect to eco‐geographic variables. A field cage experiment was carried out to compare the relative survival, growth, and change in morphology of crayfish from lotic (stream) and lentic (pond) donor habitats following relocation to a lentic recipient habitat. In the wild, lentic crayfish were broader than their lotic counterparts, which may reflect an increase in branchial (gill) volume in adaptation to an oxygen‐poor benthic environment. In the relocation experiment there was no difference in the length, growth, or survival of animals from relocated lentic, lotic, or control populations. However, crayfish derived from a lotic population showed an increase in carapace width and areola width over the 4‐month growing season following relocation. This evidence for phenotypic plasticity suggests that crayfish are resilient to relocation, and that they can adapt morphologically to novel environmental conditions. Relocation of threatened populations of A. pallipes may therefore prove a useful technique in the conservation of white‐clawed crayfish populations within the UK. Copyright © 2012 John Wiley & Sons, Ltd.

Scale- and resolution-invariance of suitable geographic range for shorebird metapopulations

The habitat suitability of a shorebird metapopulation is studied as a function of the scale (extent) and resolution (grain-size) of the environmental covariates with a maximum entropy species distribution model ( MaxEnt) for integration with climate change simulations. For this study, the species considered is the Snowy Plover ( Charadrius a. nivosus), which is a threatened shorebird whose geographic range spans the northwest and southwestern gulf coasts of Florida. The habitat suitability is analyzed at different resolutions by coarsening the classes of the ecogeographical variables with two algorithms: (i) preserving the information of each class at the finer resolution (conservative algorithm); and (ii) considering the most frequent class (majority algorithm). Ultimately, the most suitable habitat is found to be estuarine and ocean beaches made of alkaline medium and fine white sand and silt. The model fit to the observed species distribution decreases with the resolution. Due to the loss of the physical habitat (barrier islands) resulting from the coarsening operation, there is a threshold below which the model fails to predict the species distribution. As a result, the suitable geographic range is resolution-invariant below a resolution-threshold that is determined by the geomorphological features of the landscape rather than by biological constrains. This result holds for both the coarsening algorithms, however the conservative algorithm allows a continuous mapping of the habitat suitability. The suitable geographical range is found to be scale- and resolution-invariant, yet the habitat suitability at-a-point appears scale-dependent due to the strong heterogeneity of the ecogeographical variables. The scale- and resolution-invariance of the suitable geographic range appears a universal result for metapopulations of different species. This is important for reducing the uncertainty of population viability models that are based also on the choice of extent and grain-size of habitat predictions. However, attention must be paid in choosing a resolution that is not too large in order to correctly represent the physical habitat of the species. This implies a potential increase in the effectiveness of conservation campaigns to face the threats of climate change, such as sea-level rise for the Snowy Plover.

A tribute to Hubert Saint Girons: niche separation between Vipera aspis and V. berus on the basis of distribution models

AbstractInterspecific competition in contact areas is a major topic in ecological studies. A number of studies were carried out on European vipers, focusing on contact areas between two or three species characterized as appropriate by ecological needs more or less similar. The aim of this study is to extend the analysis of this topic to the case of Vipera aspis and V. berus in an alpine area of northern Italy, by comparing suitability models to verify which ecological factors affect their occurrence and to assess a possible niche separation. Potential distribution was modelled using the maximum entropy method, using six non-correlated ecogeographical variables as predictors. The models fitted well for both species (mean AUC = 0.926; 87.4% of testing data correctly classified). The most informative variables were: habitat, altitude and solar radiation for the asp viper; altitude and habitat for the adder. Deciduous woods, meadows and urban areas had a positive effect on V. aspis distribution as wetlands, meadows and rocks vegetation did on V. berus. However, the variable best separating the species was the elevation, the adder occurring more frequently at higher altitude than the asp viper. Our data showed that the two vipers were mutually exclusive, as already observed by Saint Girons in 1975. Vipera aspis is more thermophilic and lives at low altitude, while Vipera berus lives under cool and humid areas typical of alpine pastures. A similar pattern were found in the contact areas between European vipers belonging to the V. aspis and Pelias group respectively.

Genetic structure and ecogeographical adaptation in wild barley (Hordeum chilenseRoemer et Schultes) as revealed by microsatellite markers

BackgroundMulti-allelic microsatellite markers have become the markers of choice for the determination of genetic structure in plants. Synteny across cereals has allowed the cross-species and cross-genera transferability of SSR markers, which constitute a valuable and cost-effective tool for the genetic analysis and marker-assisted introgression of wild related species. Hordeum chilense is one of the wild relatives with a high potential for cereal breeding, due to its high crossability (both interspecies and intergenera) and polymorphism for adaptation traits. In order to analyze the genetic structure and ecogeographical adaptation of this wild species, it is necessary to increase the number of polymorphic markers currently available for the species. In this work, the possibility of using syntenic wheat SSRs as a new source of markers for this purpose has been explored.ResultsFrom the 98 wheat EST-SSR markers tested for transferability and polymorphism in the wild barley genome, 53 primer pairs (54.0%) gave cross-species transferability and 20 primer pairs (20.4%) showed polymorphism. The latter were used for further analysis in the H. chilense germplasm. The H. chilense-Triticum aestivum addition lines were used to test the chromosomal location of the new polymorphic microsatellite markers. The genetic structure and diversity was investigated in a collection of 94 H. chilense accessions, using a set of 49 SSR markers distributed across the seven chromosomes. Microsatellite markers showed a total of 351 alleles over all loci. The number of alleles per locus ranged from two to 27, with a mean of 7.2 alleles per locus and a mean Polymorphic Information Content (PIC) of 0.5.ConclusionsAccording to the results, the germplasm can be divided into two groups, with morphological and ecophysiological characteristics being key determinants of the population structure. Geographic and ecological structuring was also revealed in the analyzed germplasm. A significant correlation between geographical and genetic distance was detected in the Central Chilean region for the first time in the species. In addition, significant ecological influence in genetic distance has been detected for one of the population structure groups (group II) in the Central Chilean region. Finally, the association of the SSR markers with ecogeographical variables was investigated and one marker was found significantly associated with precipitation. These findings have a potential application in cereal breeding.