Niche Distribution Research Articles

Predicting the past distribution of species climatic niches

ABSTRACTPredicting past distributions of species climatic niches, hindcasting, by using climate envelope models (CEMs) is emerging as an exciting research area. CEMs are used to examine veiled evolutionary questions about extinctions, locations of past refugia and migration pathways, or to propose hypotheses concerning the past population structure of species in phylogeographical studies. CEMs are sensitive to theoretical assumptions, to model classes and to projections in non‐analogous climates, among other issues. Studies hindcasting the climatic niches of species often make reference to these limitations. However, to obtain strong scientific inferences, we must not only be aware of these potential limitations but we must also overcome them. Here, I review the literature on hindcasting CEMs. I discuss the theoretical assumptions behind niche modelling, i.e. the stability of climatic niches through time and the equilibrium of species with climate. I also summarize a set of ‘recommended practices’ to improve hindcasting. The studies reviewed: (1) rarely test the theoretical assumptions behind niche modelling such as the stability of species climatic niches through time and the equilibrium of species with climate; (2) they only use one model class (72% of the studies) and one palaeoclimatic reconstruction (62.5%) to calibrate their models; (3) they do not check for the occurrence of non‐analogous climates (97%); and (4) they do not use independent data to validate the models (72%). Ignoring the theoretical assumptions behind niche modelling and using inadequate methods for hindcasting CEMs may well entail a cascade of errors and naïve ecological and evolutionary inferences. We should also push integrative research lines linking macroecology, physiology, population biology, palaeontology, evolutionary biology and CEMs for a better understanding of niche dynamics across space and time.

An R 0 theory for source–sink dynamics with application to Dreissena competition

Source–sink dynamics may be ubiquitous in ecology. We developed a theory for source–sink dynamics using spatial extensions of the net reproductive value, R 0, which has been used elsewhere to define fitness, disease eradication, population growth, and invasion risk. R 0 decomposes into biologically meaningful components—lifetime reproductive output, survival, and dispersal—that are widely adaptable and easily interpreted. The theory provides a general quantitative means for relating fundamental niche, biotic interactions, dispersal, and species distributions. We applied the methods to Dreissena and found a resolution to a paradox in invasion biology—competitive coexistence between quagga (Dreissena bugensis) and zebra (D. polymorpha) mussels among lakes despite extensive niche overlap within lakes. Source–sink dynamics within lakes between deepwater and shallow habitats, which favor quagga and zebra mussels, respectively, yield a metacommunity distribution where quagga mussels dominate large lakes and zebra mussels dominate small lakes. The source–sink framework may also be useful in spatial competition theory, habitat conservation, marine protected areas, and ecological responses to climate change.

Present and Active: Digital Publishing in a Post-print Age

Digital publishing is changing the way in which research, particularly in the humanities, is being undertaken and it offers a range of transformative possibilities and challenges to traditional disciplines and to the nature of the printed text. The technical manipulation of information and the construction of new content that can be customised, modified, disseminated, and accessed within a global, distributed network provide new opportunities for the humanities researcher. As a way of illustrating our argument, we discuss the Children's Literature Digital Resources (CLDR) project, with with we are involved, and explore a range of emerging new media and their impact on research in the humanities and education.

Grinnellian and Eltonian niches and geographic distributions of species

In the recent past, availability of large data sets of species presences has increased by orders of magnitude. This, together with developments in geographical information systems and statistical methods, has enabled scientists to calculate, for thousands of species, the environmental conditions of their distributional areas. The profiles thus obtained are obviously related to niche concepts in the Grinnell tradition, and separated from those in Elton's tradition. I argue that it is useful to define Grinnellian and Eltonian niches on the basis of the types of variables used to calculate them, the natural spatial scale at which they can be measured, and the dispersal of the individuals over the environment. I use set theory notation and analogies derived from population ecology theory to obtain formal definitions of areas of distribution and several types of niches. This brings clarity to several practical and fundamental questions in macroecology and biogeography.

Predicting the potential spatial distributions of epiphytic lichen species at the landscape scale

Abstract:The potential spatial distributions of six epiphytic lichen species were assessed in Switzerland (41 000 km2) as a function of various key climatic drivers and forest types using logistic regression models. Cetrelia cetrarioides is ‘near threatened’, Lobaria pulmonaria is ‘vulnerable’, and Graphis scripta, Hypogymnia physodes, Lecanora cadubriae, Letharia vulpina are not endangered according to the Red List assessment based on IUCN criteria. Lichen presence and absence were derived from the SwissLichens database that contains spatially explicit information on both species presence and absence.The spatial lichen niches are predicted with R2 values between 0·5 and 0·75 and AUC values between 0·63 and 0·94. Model evaluation shows that the models perform well.Lichenologists reviewed the spatial predictions of lichen species on the basis of their expert knowledge and concluded that parsimonious regression models may suffice for successful prediction of the potential spatial niche distributions of epiphytic lichen species.

Co‐occurrence based assessment of habitat generalists and specialists: a new approach for the measurement of niche width

Summary Much ecological theory is based on the characterization of ecological habits of species as ‘generalist’ or ‘specialist’, but standard measures for placing species along a generalist‐specialist gradient do not exist. We introduce a method for quantifying habitat specialization (i.e. relative niche widths) using species co‐occurrence data. Generalists should co‐occur with many species, whereas specialists should co‐occur with relatively few species, given equal plot occurrences. We quantify this concept using a generalist‐specialist metric (θ) derived from a beta diversity statistic. We evaluate the ability of our generalist‐specialist metric to correctly rank species according to simulated (known) niche widths. Our technique is generally robust to a wide variety of niche distribution structures and sampling designs, but surveys strongly biased toward certain habitats can undermine the ability of θ to accurately describe niche widths for underrepresented species. We apply our technique to three spatially nested surveys of the large woody flora (> 1 cm d.b.h.) of the south‐eastern USA. For each dataset we rank the generalist‐specialist tendencies of all species of non‐trivial occurrences, including 113 species across the Southeast, 71 species of southern Appalachian forests, and 44 species of the 6800‐ha Joyce Kilmer‐Slickrock Wilderness Area (NC and TN, USA). Rankings of species’θ‐values were generally consistent among datasets of different spatial extent. Generalist species (e.g. Ilex opaca, Ulmus rubra, Morus rubra, Prunus serotina, Acer rubrum) were often those with large geographical ranges, particularly for θ‐values from the largest dataset, and overall were more likely to be bird‐dispersed, deciduous, and shade tolerant. South‐eastern specialist species (e.g. Taxodium spp., Abies fraseri, Quercus laevis, Pinus pungens, Pinus palustris) were those associated with stressful or unusual conditions, such as a long duration of flooding, high fire frequency, or extreme cold or dry climates. Our study demonstrates that increasingly available, large‐survey datasets can contribute niche‐related species information in the absence of detailed environmental or habitat measurements. Applications include new assessments of relationships between species traits, ecological and environmental tolerances, and species packing in different assemblages.

Ecological Niche and Geographic Distribution of Human Monkeypox in Africa

Monkeypox virus, a zoonotic member of the genus Orthopoxviridae, can cause a severe, smallpox-like illness in humans. Monkeypox virus is thought to be endemic to forested areas of western and Central Africa. Considerably more is known about human monkeypox disease occurrence than about natural sylvatic cycles of this virus in non-human animal hosts. We use human monkeypox case data from Africa for 1970–2003 in an ecological niche modeling framework to construct predictive models of the ecological requirements and geographic distribution of monkeypox virus across West and Central Africa. Tests of internal predictive ability using different subsets of input data show the model to be highly robust and suggest that the distinct phylogenetic lineages of monkeypox in West Africa and Central Africa occupy similar ecological niches. High mean annual precipitation and low elevations were shown to be highly correlated with human monkeypox disease occurrence. The synthetic picture of the potential geographic distribution of human monkeypox in Africa resulting from this study should support ongoing epidemiologic and ecological studies, as well as help to guide public health intervention strategies to areas at highest risk for human monkeypox.

RELATING PLANT TRAITS AND SPECIES DISTRIBUTIONS ALONG BIOCLIMATIC GRADIENTS FOR 88 LEUCADENDRON TAXA

Convergence between species niches and biological traits was investigated for 88 Leucadendron taxa in the Cape Floristic region. First, niche separation analysis was performed to relate species' niche positions/breadths with bioclimatic gradients. These gradients of aridity, seasonality of water availability, heat, and cold stress explained almost all variation in niche distributions. Species present in zones of extreme aridity or temperature exhibited narrower niche breadths than species situated in moderate sites, suggesting that stress-tolerant species do not occupy broad environmental ranges. Second, species niche positions were related to selected biological traits. Species of arid sites had significantly lower blade areas than did species of moist sites, confirming a functional trade-off between stress tolerance and productivity for leaf design. Species dispersal mode was correlated to species niche positions on the aridity gradient, suggesting allometrically determined correlations between leaf design and the design of reproductive structures. Species niche positions were also correlated with flowering traits, with species that initiate flowering in winter found under Mediterranean climate influence and species that initiate flowering in spring in sites with greater summer rainfall input. By interrelating species niche positions on bioclimatic gradients with selected biological traits, we explored a novel biogeographical approach to understanding species distributions.

Predicting distributions of known and unknown reptile species in Madagascar.

Despite the importance of tropical biodiversity, informative species distributional data are seldom available for biogeographical study or setting conservation priorities. Modelling ecological niche distributions of species offers a potential solution; however, the utility of old locality data from museums, and of more recent remotely sensed satellite data, remains poorly explored, especially for rapidly changing tropical landscapes. Using 29 modern data sets of environmental land coverage and 621 chameleon occurrence localities from Madagascar (historical and recent), here we demonstrate a significant ability of our niche models in predicting species distribution. At 11 recently inventoried sites, highest predictive success (85.1%) was obtained for models based only on modern occurrence data (74.7% and 82.8% predictive success, respectively, for pre-1978 and all data combined). Notably, these models also identified three intersecting areas of over-prediction that recently yielded seven chameleon species new to science. We conclude that ecological niche modelling using recent locality records and readily available environmental coverage data provides informative biogeographical data for poorly known tropical landscapes, and offers innovative potential for the discovery of unknown distributional areas and unknown species.

Silicified Microbes in a Geyser Mound: The Enigma of Low-Temperature Cyanobacteria in a High-Temperature Setting

A geyser mound, which has formed around the vent of an abandoned well-bore in the Tokaanu geothermal area (North Island, New Zealand) over the last 50 years, is formed primarily of white opal-A along with lesser amounts of black opal-A, reticulate, amorphous or poorly crystalline clay, halite, and scattered detrital quartz grains. Despite the boiling water ejected from the vent, at least 19 taxa of silicified microbes are present in the geyserite. Calothrix , Phormidium , and Synechococcus dominate. Other microbes, including local concentrations of diatoms, are widely scattered. The dominance of cyanobacteria is enigmatic given that these microbes typically are found in cooler water environments (< 60°C) on the medial to distal parts of geyser and hot-spring discharge aprons. The proximal zone around a geyser vent is environmentally unstable because it oscillates between periodic eruptions of boiling water and cooler phases in accord with the eruptive cycle of the geyser. Thus, the environmental niches on a geyser mound are temporally and spatially variable. The periodicity, duration, and magnitude of the eruptions, and the dispersal patterns of boiling water during eruptions control the distribution of the microenvironmental niches and their temporal changes. Dispersal and cooling of the ejected water will, for example, be controlled by factors such as height of the erupted water, ambient air temperature, and prevailing wind direction. Biotas compatible with relatively cool waters may thrive on geyser mounds because they inhabit areas that are not inundated constantly by boiling water. Their development and the sinter fabrics that they generate in the proximal zone of a geyser vent means that ancient deposits must be interpreted with caution.

Morphology and coexistence of congeneric ectoparasite species: reinforcement of reproductive isolation?

Assuming that differences or similarities in morphology among congeneric parasite species living in the same habitat are not a random pattern, several hypotheses explaining morphological differences were tested: (i) reproductive isolation, (ii) niche restriction resulting from competition, and (iii) niche specialization. Congeneric monogenean (platyhelminth) ectoparasites parasitizing the gills of one host species were used as an ecological model. Morphometric distances of the attachment organ and morphometric distances of the copulatory organ between species pairs were calculated, Levin's niche size and Renkonen niche overlap indices were applied. Our results support the prediction that the function of niche segregation is to achieve reproductive isolation of related species in order to prevent hybridization (reinforcement of reproductive barriers). Parasite species living in the same niche differ greatly in the size of copulatory organ. Moreover, species coexistence is facilitated by an increase in morphometric distances of copulatory organ and niche centre distances. Our results also show that species living in overlapping niches have similar attachment organs, which supports the prediction that morphologically similar species have the same ecological requirements within one host and suggests small effects of interspecific competition for the evolution of morphological diversity of attachment organs. Specialist adaptations also seem to facilitate species coexistence and affect the niche distribution within host species. Parasite species that can colonize more than one host species, i.e. generalists, occupy more distant niches within host species than strictly host-specific parasites.

Niche differentiation and distribution of Carex curvula along a bioclimatic gradient in the southwestern Alps

Abstract. Carex curvula is a dominant sedge of European alpine tundra, exhibiting two morphological forms: C. curvula ssp. curvula (Ccc) and C. curvula ssp. rosae (Ccr). In this paper, we attempt to explore whether Ccc and Ccr are ecotypes or vicariant forms and whether between‐ and within‐regional distribution patterns can be explained by variations in the amount of available habitats and/or by changes in niche attributes. The study area covered three bioclimatically distinct regions of the southwestern Alps in which local abundances of Ccc and Ccr strongly differ.The realized niche of both forms was investigated by a direct gradient analysis performed on an extensive floristic and environmental data set. We found no evidence of niche overlap between Ccc and Ccr as their distribution curves differ strongly along disturbance, mesotopography and soil acidity gradients. We investigated the effect of region on the structure of local scale variables tables. Highly concordant patterns among regions were found, except that optimal habitat conditions for Ccc were infrequent in the southernmost regions. We compared the ecological behaviour of range centre and range margin populations of each form. We found a narrower ecological amplitude for Ccr in the northern part of its range, whereas for Ccc the niche breadth of range‐margin populations was not reduced compared to range centre populations. At its southern range limit, Ccc mostly occupies ecologically marginal habitats.We conclude that Ccc and Ccr represent ecotypes, not vicariant forms. Finally, we suggest that habitat availability, resulting from the interplay of regional‐scale and local‐scale variables, satisfactorily explains the distributional patterns of Carex curvula ecotypes in the southwestern Alps.

Niche differentiation and distribution of Carex curvula along a bioclimatic gradient in the southwestern Alps

Abstract Carex curvula is a dominant sedge of European alpine tundra, exhibiting two morphological forms: C. curvula ssp. curvula (Ccc) and C. curvula ssp. rosae (Ccr). In this paper, we attempt to explore whether Ccc and Ccr are ecotypes or vicariant forms and whether between- and within-regional distribution patterns can be explained by variations in the amount of available habitats and/or by changes in niche attributes. The study area covered three bioclimatically distinct regions of the southwestern Alps in which local abundances of Ccc and Ccr strongly differ. The realized niche of both forms was investigated by a direct gradient analysis performed on an extensive floristic and environmental data set. We found no evidence of niche overlap between Ccc and Ccr as their distribution curves differ strongly along disturbance, mesotopography and soil acidity gradients. We investigated the effect of region on the structure of local scale variables tables. Highly concordant patterns among regions were found,...

The effect of temperature on growth of juvenile bloater

The bloater (Coregonus hoyi), which feeds mainly on invertebrates and in turn is eaten by lake trout (Salvelinus namaycush) and burbot (Lota lota), is a major trophic integrator in coldwater ecosystems in the upper Great Lakes. To better understand their thermal niche and habitat distribution, we acclimated groups of yearling bloater to 3, 5, 10, 15, 20, or 25°C and then fed them ad libitum for 35 days. Bloater increased in length and weight at all of the test temperatures and at the end of the study were heaviest and longest at 15–20°C. The specific growth rate was highest at 20°C and progressively lower at 15, 25, 10, 5, and 3°C. A curve fitted to the specific growth rate data indicated that the optimum temperature for growth was 18.6°C. Our results are in agreement with other published information on the thermal ecology of juvenile bloater.

Spatial structure of community of darkling beetles (Coleoptera: Tenebrionidae) in the Negev Highlands, Israel

The distribution of niches in resource space of darkling beetles of Negev desert, Israel were studied using discriminant analysis. Seventeen environmental variables (substrate structure and vegetation) were measured at 375 plots within 15 grids. The first three discriminant axes account for 77% of the variance and reflect a soil structure gradient from sand to clay (the first axis), a gradient of increasing productivity (the second axis), and a type of vegetation architecture (the third axis). Abundance and biomass of tenebrionids increased linearly along the first, the second and the third axes. Species richness and diversity had a slanting parabola shape along the substrate axis and increased along the productivity axis. There were two distinct spatial guilds of tenebrionid species. One guild was composed by species that preferred sandy‐gravel soils, and another guild consisted of species that preferred clay soils. Niche overlapping of the “sandy‐gravel” species was lower than that of the “clay” species. Niches of the “sandy‐gravel” species were randomly distributed in the resource space. Those of the “clay” species formed a tight cluster with most niches placed in the center of the space, representing the centrifugal type of organization. The conformity of the guild structure with the different types of organization was supported by comparisons between empirical data and stochastic models. The border between these two guilds matches with proposed earlier biogeographical boundary (Ramon‐Zohar line).

A stochastic ecological model

By including under the name ‘niches’ all the beneficial and adverse factors or attributes for an ecological system that contribute or affect the biomasses of the species in that system, the contributory functions of these factors, together with their distributions in spatial region, have been proposed. From the random nature of these functions, termed as ‘random causes’ for the ecosystem, the stochastic evolution equations for the biodensities of the spreading species have been deduced. These equations are found to be very general in nature and also describe the nonlocal contributions of the biodensities. They can produce stochastic partial differential equations for the biodensities of the species for various ecological systems. Finally, it has been discussed how the experimental values of the population growth and spread over a region with the niche distribution therein, can determine the ecological niche-contribution functions to the species of the system. The stationary or equilibrium transition probabilities for the general ecological systems are also given.

Population structure ofArmillariaspecies in several forest types

Population structure of Armillaria calves- cens, A. gemina, A. gallica and A. ostoyae in New York was studied in plots established at six sites and tran- sects at three others. No significant differences among species in size or density of genets (identified by so- matic incompatibility) was detected. The size distri- bution of genets revealed a high frequency of very small genets (mostly associated with single sample points) and a uniformly lower frequency of larger gen- ets ranging up to 670 m2 (44 m long). Density of genets (including all Armillaria species) was higher in plots with more species of Armillaria. There was little spatial overlap between genets regardless of species. Five of 33 pairs of isolates from within roots and from su- perficial, associated rhizomorphs consisted of differ- ent species; the other 28 pairs were comprised of sin- gle genets. The data suggest that expansion beyond the initial resource unit is a critical phase in the de- velopment of genets and are consistent with patchwise distribution of niches that differentiate Armillaria spe- cies in these stands. Evidence from two plots, in which A. ostoyae apparently colonized planted stands of co- nifers on sites previously unforested or supporting hardwoods, supports the concept that basidiospores are important in the population structure of Armillaria species and the epidemiology of the diseases they cause.

Analysis of Spatial Organization of a Desert Rodent Community in Bolson de Mapimi, Mexico

We studied the distribution of niches in resource space and niche patterns of a 12-species community of desert rodents by use of canonical-variate and principal-component analyses. Fourteen characters of the environment, measured at 475 sample plots within 19 1-ha grid areas (474 captures of rodents on plots), and eight morphological indicators of niches were used. The first three canonical axes of resource space accounted for 81% of the variance; each of the axes is identified by one of the characteristics of the substrate and one to two characteristics of the vegetation. There was a high level of continuity in distribution of species in the resource space. The lowest values of coefficients of variation of niche overlap and of distances between niche centers characterize a group of the nearest-neighbor species. There was a marked negative correlation of morphological distances to the nearest neighbor with the distances between the same species in the resource space. This evidence indicates certain limitations of ecological similarity of cohabitating species. Negative correlations between niche breadth and the position of the niche in resource space, and between the maximal density of population and niche breadth, are demonstrated.

Oviposition behavior and its relation to egg niche location in the yellowheaded borer,dirphya nigricornis

The oviposition behavior of the yellowheaded borer,Dirphya nigricornis Olivier (Coleoptera: Cerambycidae), on coffee plants consists of the following phases: physical search of the tips by the tarsi and by vision, preparation of the chosen ovipositional site with the mandibles, and egg deposition and sealing. This period lasts 11.3 ± 1.8 min (all values ± S.E.), and is comprised of a search period of 3.0 ± 0.5 min, a gnawing period of 1.0 ± 0.2 min, an egg deposition period of 5.0 ± 0.1 min, and a sealing period of 2.0 ± 0.3 min. Within that time, the females are able to integrate various plant factors such as preferability of distal tip internodes, their green color and girths of 0.9 ± 0.1 cm, and the possibility of peeling the bark with the least force; these external factors, in addition to the length of the green primordial tissue, may account for the abundance and distribution of the egg niches on internode tips.

Seasonal distribution and abundance of immature stages of the yellow-headed borer Dirphya nigricornis Olivier (Coleoptera, Cerambycidae) on coffee

Seasonal occurrence of the beetle, Dirphya nigricornis Olivier, was monitored in the field for 3 years. Two coffee varieties, French mission and SL34 with capped and uncapped canopies respectively, were used to estimate the egg niches in two coffee estates at Ruiru, Kenya. The total egg niches in the short and long rainy seasons represented low infestation (1.56–8.21%), which was nearly stable throughout the study period, 1982–1984. In some cases, however, seasonal significant (P = 0.05) variety-to-variety differences existed between egg niches at each studied site. The distribution of the egg niches of D. nigricornis occurred on branches between the 1st and 21st internodes of primary and tertiary shoots of either variety. Egg niches were negatively correlated (r = -0.44 to r = -0.99, 19d.f.) to internode position in all five categories of the shoots examined. The beetle therefore concentrates infestation and does not place its progeny randomly on coffee shoots.