A numerical analysis of the mesoscale distribution patterns of vascular plants in the subarctic Kevo Nature Reserve, northern Finland

Different numerical techniques were used to detect and describe the major ecological-biogeographical patterns of vascular plant distributions at the meso-scale level in a subarctic region in Finland. The distribution patterns of 231 native taxa in 362 1 km² grid squares of the Kevo Nature Reserve were analysed by two-way indicator species analysis and detrended correspondence analysis, and were subsequently related to twenty-eight geographical, topographical, geological, and vegetational variables using simple discriminant functions and canonical correspondence analysis with associated Monte Carlo permutation tests.
The floristic variation detected reflects variations in environmental factors operative at the regional and local scales. No major broad-scale coherent geographical patterns were detected; instead, the spatial distribution of the grids with a similar floristic composition shows a scattered distribution. All the numerical techniques reveal a major gradient from alpine areas to lowland sites with rivers and rocky outcrops, and the most important explanatory variables for predicting the main floristic variation are all associated with altitude. The floristic patterns represented by the second ordination gradient mainly correlate with the abundance of mires. Partial ordinations indicate that both the geographical and geological variables explain relatively little of the species distributional patterns.
Although the meso-scale approach reveals much about the plant-environment relationships in the study area, the floristic variation appears to be determined mainly by fine-scale factors. In the most heterogeneous grids, the grid size used fails to detect accurately the ecological patterns of the species present.     

Modeled global invasive potential of Asian gypsy moths, Lymantria dispar

Asian populations of gypsy moths, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), remain poorly characterized – indeed, they are not presently accorded any formal taxonomic status within the broader species. Their ecology is similarly largely uncharacterized in the literature, except by assumption that it will resemble that of European populations. We developed ecological niche models specific to Asian populations of the species, which can in turn be used to identify a potential geographic distributional area for the species. We demonstrated statistically significant predictivity of distributional patterns within the East Asian range of these populations; projecting the Asian ecological niche model to Europe, correspondence with European distributions was generally good, although some differences may exist; projecting the ecological niche model globally, we characterized a likely potential invasive distribution of this set of populations across the temperate zone of both Northern and Southern Hemisphere.     

Pleistocene fragmentation of Amazon species' ranges

Historical patterns of connection and isolation of the impressive biological diversity of the Amazon Basin have been the subject of extensive debate, based on evidence drawn from distributional patterns of endemic species, vegetation histories from palynological studies, and geological studies. We develop species-specific ecological niche models based on current occurrence patterns of 17 species of birds and woody plants, which we project onto modelled Pleistocene (Last Glacial Maximum) climatic patterns to reconstruct past potential distributions of each species. Forest species' distributions showed fragmentation at Last Glacial Maximum and these fragments were coincident spatially, whereas savanna species showed no clear trends. Our results suggest that past climate changes fragmented forest species' ranges within a matrix of uncertain composition.     

Modelling the distribution of a threatened habitat: the California sage scrub

Aim Using predictive species distribution and ecological niche modelling our objectives are: (1) to identify important climatic drivers of distribution at regional scales of a locally complex and dynamic system – California sage scrub; (2) to map suitable sage scrub habitat in California; and (3) to distinguish between bioclimatic niches of floristic groups within sage scrub to assess the conservation significance of analysing such species groups. Location Coastal mediterranean‐type shrublands of southern and central California. Methods Using point localities from georeferenced herbarium records, we modelled the potential distribution and bioclimatic envelopes of 14 characteristic sage scrub species and three floristic groups (south‐coastal, coastal–interior disjunct and broadly distributed species) based upon current climate conditions. Maxent was used to map climatically suitable habitat, while principal components analysis followed by canonical discriminant analysis were used to distinguish between floristic groups and visualize species and group distributions in multivariate ecological space. Results Geographical distribution patterns of individual species were mirrored in the habitat suitability maps of floristic groups, notably the disjunct distribution of the coastal–interior species. Overlap in the distributions of floristic groups was evident in both geographical and multivariate niche space; however, discriminant analysis confirmed the separability of floristic groups based on bioclimatic variables. Higher performance of floristic group models compared with sage scrub as a whole suggests that groups have differing climate requirements for habitat suitability at regional scales and that breaking sage scrub into floristic groups improves the discrimination between climatically suitable and unsuitable habitat. Main conclusions The finding that presence‐only data and climatic variables can produce useful information on habitat suitability of California sage scrub species and floristic groups at a regional scale has important implications for ongoing efforts of habitat restoration for sage scrub. In addition, modelling at a group level provides important information about the differences in climatic niches within California sage scrub. Finally, the high performance of our floristic group models highlights the potential a community‐level modelling approach holds for investigating plant distribution patterns.     

Eroding abodes and vanished bridges: historical biogeography of the substrate specialist pebble-mound mice (Pseudomys)

Aim  To determine whether the pronounced ecological importance of pebble mounds to pebble-mound mice ( Pseudomys ) is manifest in their continental biogeography.
Location  Northern Australia.
Methods  A GIS-based comparison was made between the habitats contained within the potential climatic distributions of mice, representing a null hypothesis of no habitat selection, and their actual distributions based on all known location records.
Results  All species had a clear preference for hilly, rocky landscapes with a surficial cover dominated by bedrock. Simple vegetation communities with relatively open eucalypt overstorey and grassy understorey were preferred. Highly degraded rocks and aggradational surfaces and plains were avoided. The extent of the summer monsoon may be important in determining the southern limits of the group's distribution. Major disjunctions between species were attributable to the presence of clay plains and sand sheets.
The behavioural requirement of pebble-mound mice for mounds determines their population distribution pattern and the distribution of the different species within the genus.
Main conclusions  The behavioural need for pebble mounds drives the distributional pattern of populations and species of pebble-mound mice. The initial spread of pebble-mound mice probably occurred during the late Pliocene or earliest Pleistocene. There has predominantly been degradation of the potential distribution of the group since that time due to the stability of Australian landscapes and Pleistocene planation and sand sheet development over large areas of northern Australia. This process is ongoing, and past regions of rocky contact between current distributions have disappeared, while the distributional limits of several species are steadily being reduced by erosion of hills and the spread of dune fields.     

Climatic niche divergence explains angiosperm diversification across clades in China

Diversification rates are critically important for understanding patterns of species richness among clades. However, the effects of climatic niche width on plant diversification rates remain to be elucidated. Based on the phylogenetic, climatic, and distributional information of angiosperms in China, a total of 26 906 species from 182 families were included in this study. We aimed to test relationships between diversification rate and climatic niche width and climatic niche width related variables (including climatic niche divergence, climatic niche position, geographic extent, and climatic niche evolutionary rate) using phylogenetic methods. We found that climatic niche divergence had the largest unique contribution to the diversification rate, while the unique effects of climatic niche width, climatic niche position, geographic extent, and climatic niche evolutionary rate on the diversification rate were negligible. We also observed that the relationship between diversification rate and climatic niche divergence was significantly stronger than the null assumption (artefactual relationship between diversification and clade-level climatic niche width by sampling more species). Our study supports the hypothesis that wider family climatic niche widths explain faster diversification rates through a higher climatic niche divergence rather than through higher geographic extent, higher climatic niche evolutionary rate, or separated climatic niche position. Hence, the results provide a potential explanation for large-scale diversity patterns within families of plants.     

Factors influencing forage selection by the North American beaver (Castor canadensis)

Across their range, a large number of biotic and abiotic factors are known to influence the choice of browse plant and the foraging behaviour of the North American beaver (Castor canadensis). We used generalized linear mixed-effects models to investigate sets of variables that may influence the foraging choices of beaver: forage species, distance of forage from water, forage density, and site. Communities across the study sites in central British Columbia, Canada, were dominated by Salix sitchensis, Salix lucida, and Alnus spp. Density had no impact on forage selection, while site, distance from water, and species identity all influenced the foraging decisions of beaver. We postulated that these factors may be ordered hierarchically: large-scale factors, such as site, followed by the medium-scale distance from water, and species of plant at the finest scale. Forage items in some sites had a higher probability of being browsed than in others, while in all sites the probability of being browsed decreased with increasing distance from water. Beaver appeared to be foraging as “picky” generalists; of the 9 plant species examined, 3 species of Salix (S. scouleriana, S. drummondiana and S. sitchensis) were selected by beaver, Salix bebbiana was avoided, and 5 species were neither selected for nor against. Browse selection within the genus Salix implied that beaver were able to differentiate among closely related species. Detailed information on forage selection is a crucial first step in designing and interpreting models that predict large-scale distributional patterns of beaver.     

Predicting changes in Fennoscandian vascular-plant species richness as a result of future climatic change

It is anticipated that future climatic warming following the currently enhanced greenhouse effect will change the distribution limits of many vascular plant species. Using annual accumulated respiration equivalents, calculated from January and July mean temperatures and total annual precipitation, simple presence–absence response surface plots are constructed for 1521 native vascular-plant species in 229 75×75-km grid squares within Fennoscandia. The contemporary occurrences in relation to present-day climate and to predicted changes in climate (and hence annual accumulated respiration equivalents) are used to predict possible future immigrations and extinctions within each grid square. The percentage of potential change in species richness for each grid square is estimated from these predictions. Results from this study suggest a mean increase in species richness per grid square of 26%. Increases in species richness are greatest in the southern parts of the alpine/boreal regions in Fennoscandia. There are ten species that potentially may become extinct in Fennoscandia as a result of predicted climatic warming. Possible conservation strategies to protect such endangered species are outlined.     

Strengthening forecasts of climate change impacts with multi‐model ensemble averaged projections using MAGICC/SCENGEN 5.3

Climate output from general circulation models (GCMs) is being used with increasing frequency to explore potential climate change impacts on species’ distributional range shifts and extinction probability. However, different GCMs do not perform equally well in their ability to hindcast the key climatic factors that potentially influence species distributions. Previous research has demonstrated that multi‐model ensemble forecasts perform better than any single GCM in simulating observed conditions at a global scale. MAGICC/SCENGEN 5.3 is a freeware climate model ‘emulator’ that generates multi‐model ensemble forecasts, conditional on regional and/or global performance, for up to twenty GCMs. In combination with a new application ‘M/SGridder’, this software can be used to produce down‐scaled ensemble forecasts, which minimize climate‐model‐related uncertainty, for a range of ecological problems.     

Pollen–plant–climate relationships in sub-Saharan Africa

Aim  To demonstrate that incorporating the bioclimatic range of possible contributor plants leads to improved accuracy in interpreting the palaeoclimatic record of taxonomically complex pollen types.
Location  North Tropical Africa.
Methods  The geographical ranges of selected African plants were extracted from the literature and geo-referenced. These plant ranges were compared with the pollen percentages obtained from a network of surface sediments. Climate-response surfaces were graphed for each pollen taxon and each corresponding plant species.
Results  Several patterns can be identified, including taxa for which the pollen and plant distributions coincide, and others where the range limits diverge. Some pollen types display a reduced climate range compared with that of the corresponding plant species, due to low pollen production and/or dispersal. For other taxa, corresponding to high pollen producers such as pioneer taxa, pollen types display a larger climatic envelope than that of the corresponding plants. The number of species contained in a pollen taxon is an important factor, as the botanical species included in a taxon may have different geographical and climate distributions.
Main conclusions  The comparison between pollen and plant distributions is an essential step towards more precise vegetation and climate reconstructions in Africa, as it identifies taxa that have a high correspondence between pollen and plant distribution patterns. Our method is a useful tool to reassess biome reconstructions in Africa and to characterize accurately the vegetation and climate conditions at a regional scale, from pollen data.     

Forecasting Climate Change Effects on Salamander Distribution in the Highlands of Central Mexico1

A generalized decline of amphibian populations is occurring worldwide. The causes for such a decline are not completely understood; however, climate change has been identified as a possible cause for amphibian extinction, among others. Ecological niche modeling has proven to be a useful tool to predict potential distribution of species in the context of climatic changes. In this paper, we used the Genetic Algorithm for Rule‐set Prediction (GARP) to model the potential distributions of two species of plethodontid salamanders: Pseudoeurycea cephalica and P. leprosa. We projected their potential distributions under climatic scenarios expected in 50 yr based on a conservative scenario of global climate change and assuming a moderate dispersal ability for both species. Our analyses suggest that climate change effects may pose an additional long‐term risk to both species of plethodontid salamanders, with a more dramatic scenario in the case of P. leprosa. By the year 2050, this species may lose almost 75 percent of its distributional area, and this projection is even worse when deforestation (in the way it is occurring at present) is considered within the predicted model. Our results concur with those obtained for species with limited dispersal capability because they do not track changing climates, but rather face a loss of distributional area. The survival of these species is not secure, even though their potential distributional area falls within a considerable number of natural protected areas.     

Leaf hydraulic vulnerability to drought is linked to site water availability across a broad range of species and climates

Background and Aims

Vulnerability of the leaf hydraulic pathway to water-stress-induced dysfunction is a key component of drought tolerance in plants and may be important in defining species'' climatic range. However, the generality of the association between leaf hydraulic vulnerability and climate across species and sites remains to be tested.

Methods

Leaf hydraulic vulnerability to drought (P50_leaf, the water potential inducing 50 % loss in hydraulic function) was measured in a diverse group of 92 woody, mostly evergreen angiosperms from sites across a wide range of habitats. These new data together with some previously published were tested against key climate indices related to water availability. Differences in within-site variability in P50_leaf between sites were also examined.

Key Results

Values of hydraulic vulnerability to drought in leaves decreased strongly (i.e. became more negative) with decreasing annual rainfall and increasing aridity across sites. The standard deviation in P50_leaf values recorded within each site was positively correlated with increasing aridity. P50_leaf was also a good indicator of the climatic envelope across each species'' distributional range as well as their dry-end distributional limits within Australia, although this relationship was not consistently detectable within sites.

Conclusions

The findings indicate that species sorting processes have influenced distributional patterns of P50_leaf across the rainfall spectrum, but alternative strategies for dealing with water deficit exist within sites. The strong link to aridity suggests leaf hydraulic vulnerability may influence plant distributions under future climates.     

Thermal sensitivity of cold climate lizards and the importance of distributional ranges

One of the fundamental goals in macroecology is to understand the relationship among species’ geographic ranges, ecophysiology, and climate; however, the mechanisms underlying the distributional geographic patterns observed remain unknown for most organisms. In the case of ectotherms this is particularly important because the knowledge of these interactions may provide a robust framework for predicting the potential consequences of climate change in these organisms. Here we studied the relationship of thermal sensitivity and thermal tolerance in Patagonian lizards and their geographic ranges, proposing that species with wider distributions have broader plasticity and thermal tolerance. We predicted that lizard thermal physiology is related to the thermal characteristics of the environment. We also explored the presence of trade-offs of some thermal traits and evaluated the potential effects of a predicted scenario of climate change for these species. We examined sixteen species of Liolaemini lizards from Patagonia representing species with different geographic range sizes. We obtained thermal tolerance data and performance curves for each species in laboratory trials. We found evidence supporting the idea that higher physiological plasticity allows species to achieve broader distribution ranges compared to species with restricted distributions. We also found a trade-off between broad levels of plasticity and higher optimum temperatures of performance. Finally, results from contrasting performance curves against the highest environmental temperatures that lizards may face in a future scenario (year 2080) suggest that the activity of species occurring at high latitudes may be unaffected by predicted climatic changes.     

Factors influencing the distributional abundance of two trophic guilds of Peruvian cricetid rodents

The distributional abundance of 13 species of southern Peruvian rodents is significantly correlated with altitude and patterns of vegetation but vegetation is a better predictor than altitude. Coincidental reversals in the altitudinal trends of both vegetation and rodents demonstrate that rodents are responding to vegetation patterns. Abundance and diversity of rodents are greatest around 4000 m elevation which coincides with the region of greatest vegetational abundance and seasonally heavy rainfall.
The rodent communities consist of two separate feeding guilds, omnivores and insectivores and these guilds show distinctly different distributional patterns. Insectivorous species are strongly associated with the zone of seasonally heavy rainfall (4000 m) whereas omnivorous rodents are relatively abundant over a broader spectrum of elevations and habitats. In a previous study of these same communities, we showed a correspondence between rodent morphology and their diets. This study reveals a correspondence between distributional abundance of the various species and their diets. We conclude that the distributional abundance of southern Peruvian rodents is related to the physiological constraints imposed by altitude (climate) and the distributional abundance of food resources.     

Explaining Andean megadiversity: the evolutionary and ecological causes of glassfrog elevational richness patterns

The Tropical Andes are an important global biodiversity hotspot, harbouring extraordinarily high richness and endemism. Although elevational richness and speciation have been studied independently in some Andean groups, the evolutionary and ecological processes that explain elevational richness patterns in the Andes have not been analysed together. Herein, we elucidate the processes underlying Andean richness patterns using glassfrogs (Centrolenidae) as a model system. Glassfrogs show the widespread mid‐elevation diversity peak for both local and regional richness. Remarkably, these patterns are explained by greater time (montane museum) rather than faster speciation at mid‐elevations (montane species pump), despite the recency of the major Andean uplift. We also show for the first time that rates of climatic‐niche evolution and elevational change are related, supporting the hypothesis that climatic‐niche conservatism decelerates species' shifts in elevational distributions and underlies the mid‐elevation richness peak. These results may be relevant to other Andean clades and montane systems globally.     

Non‐neutrality in forest communities: evolutionary and ecological determinants of tree species abundance distributions

The unified neutral theory of biodiversity and biogeography provides a promising framework that can be used to integrate stochastic and ecological processes operating in ecological communities. Based on a mechanistic non‐neutral model that incorporates density‐dependent mortality, we evaluated the deviation from a neutral pattern in tree species abundance distributions and explored the signatures of historical and ecological processes that have shaped forest biomes. We compiled a dataset documenting species abundance distributions in 1168 plots encompassing 16 973 tree species across tropical, temperate, and boreal forests. We tested whether deviations from neutrality of species abundance distributions vary with climatic and historical conditions, and whether these patterns differ among regions. Non‐neutrality in species abundance distributions was ubiquitous in tropical, temperate, and boreal forests, and regional differences in patterns of non‐neutrality were significant between biomes. Species abundance evenness/unevenness caused by negative density‐dependent or abiotic filtering effects had no clear macro‐scale climatic drivers, although temperature was non‐linearly correlated with species abundance unevenness on a global scale. These findings were not significantly biased by heterogeneity of plot data (the differences of plot area, measurement size, species richness, and the number of individuals sampled). Therefore, our results suggest that environmental filtering is not universally increasing from warm tropical to cold boreal forests, but might affect differently tree species assembly between and within biomes. Ecological processes generating particularly dominant species in local communities might be idiosyncratic or region‐specific and may be associated with geography and climate. Our study illustrates that stochastic dynamical models enable the analysis of the interplay of historical and ecological processes that influence community assemblies and the dynamics of biodiversity.     

A dynamic multi‐scale occupancy model to estimate temporal dynamics and hierarchical habitat use for nomadic species

Distribution models are increasingly being used to understand how landscape and climatic changes are affecting the processes driving spatial and temporal distributions of plants and animals. However, many modeling efforts ignore the dynamic processes that drive distributional patterns at different scales, which may result in misleading inference about the factors influencing species distributions. Current occupancy models allow estimation of occupancy at different scales and, separately, estimation of immigration and emigration. However, joint estimation of local extinction, colonization, and occupancy within a multi‐scale model is currently unpublished. We extended multi‐scale models to account for the dynamic processes governing species distributions, while concurrently modeling local‐scale availability. We fit the model to data for lark buntings and chestnut‐collared longspurs in the Great Plains, USA, collected under the Integrated Monitoring in Bird Conservation Regions program. We investigate how the amount of grassland and shrubland and annual vegetation conditions affect bird occupancy dynamics and local vegetation structure affects fine‐scale occupancy. Buntings were prevalent and longspurs rare in our study area, but both species were locally prevalent when present. Buntings colonized sites with preferred habitat configurations, longspurs colonized a wider range of landscape conditions, and site persistence of both was higher at sites with greener vegetation. Turnover rates were high for both species, quantifying the nomadic behavior of the species. Our model allows researchers to jointly investigate temporal dynamics of species distributions and hierarchical habitat use. Our results indicate that grassland birds respond to different covariates at landscape and local scales suggesting different conservation goals at each scale. High turnover rates of these species highlight the need to account for the dynamics of nomadic species, and our model can help inform how to coordinate management efforts to provide appropriate habitat configurations at the landscape scale and provide habitat targets for local managers.     

Translating niche features: Modelling differential exposure of Argentine reptiles to global climate change

Global climate change affects the distributions of ectotherms and may be the cause of several conservation problems, such as great displacement of climatic suitable spaces for species and, consequently, important reductions of the extent of liveable places, threatening the existence of many of them. Species exposure (and hence vulnerability) to global climate change is linked to features of their climatic niches (such as the relative position of the inhabited localities of each species in the climatic space), and therefore to characteristics of their geographic ranges (such as the extent of the distributions or altitudinal range inhabited by the species). In order to analyze the pattern of response of Argentine reptiles to global climate change, we ran phylogenetic generalized least squares models using species exposure to global climate change as a response variable, and (i) niche properties (breadth and position of the species in the climate space) and (ii) general features of the distribution of species (maximum latitude, altitudinal range, maximum elevation, distributional range and proximity to the most important dispersal barrier) as predictors. Our results suggest that the best way to explain climate change exposure is by combining breadth and position of climatic niche of the species or combining geographic features that are indicators of both niche characteristics. Our best model shows that in our study area, species with the narrowest distributional ranges that also inhabit the highest elevations are the most exposed to the effects of global climate change. In this sense, reptile species from Yungas, Puna and Andes ecoregions could be especially vulnerable to the effects of climate change. We believe that these types of models may represent an interesting tool for determining species and places particularly threatened by the effects of global climate change, which should be strongly considered in conservation planning.     

Is geographic variation within species related to macroevolutionary patterns between species?

The relationship between microevolution and macroevolution is a central topic in evolutionary biology. An aspect of this relationship that remains very poorly studied in modern evolutionary biology is the relationship between within‐species geographic variation and among‐species patterns of trait variation. Here, we tested the relationship between climate and morphology among and within species in the salamander genus Plethodon. We focus on a discrete colour polymorphism (presence and absence of a red dorsal stripe) that appears to be related to climatic distributions in a common, wide‐ranging species (Plethodon cinereus). We find that this trait has been variable among (and possibly within) species for >40 million years. Furthermore, we find a strong relationship among species between climatic variation and within‐species morph frequencies. These between‐species patterns are similar (but not identical) to those in the broadly distributed Plethodon cinereus. Surprisingly, there are no significant climate–morphology relationships within most other polymorphic species, despite the strong between‐species patterns. Overall, our study provides an initial exploration of how within‐species geographic variation and large‐scale macroevolutionary patterns of trait variation may be related.     

Relative importance of host tree species and environmental gradients for epiphytic species composition, exemplified by pyrenomycetes s. lat. (Ascomycota) on Salix in central north Scandinavia

According to the continuum concept of vegetation, variation in species composition is primarily determined by complex environmental gradients. Species-gradient relationships of ground-dwelling, independent organisms are studied at scales ranging from centimetres to continents. In this study we use a balanced data set for pyrenomycetes on Salix to address if how the current species-gradient paradigm needs to be modified to apply to assemblages of organisms that are dependent on other organisms for their existence. The data from a transect across central-north Scandinavia included variation along climatic gradients in oceanicity (from oceanic to continental vegetation sections), and temperatures (from south boreal to alpine vegetation zones) and among five common and widely distributed Salix host species ( Salix caprea agg., S. glauca ssp. glauca , S. lapponum , S. myrsinifolia agg. and S. pentandra ). Ten individuals of each Salix host species were selected and carefully examined for pyrenomycetes within each combination of section and zone. Data for 28 species in the 28 combinations of section, zone and host were subjected to ordination and constrained ordination analyses. Host species was the most important source of variation in species composition, followed by zone and section which are the same major regional gradients that are important to plants. We use examples to discuss the contribution of local ecological and substrate gradients to the high variation explained by host species, concluding that host specificity per se occurs for these partly parasitic fungi. We therefore suggest that in order to account for variation in composition of species assemblages with strong degree of host dependence, general rules for species-gradient relationships need to be extended by inclusion of host specificity as separate factor.