The region effect on mesoscale plant species richness between eastern Asia and eastern North America

The greater number of plant species in temperate eastern Asia compared to eastern North America has been ascribed to both local environment and regional characteristics, but the relative contributions of each have not been resolved. In this analysis, we related species richness of flowering plants in mesoscale floras (<10⁴ km²) dominated by temperate forest vegetation to area, elevation, latitude, and several climate variables. When analyses were conducted separately within each region, area and, in eastern Asia, elevation, were the primary determinants of species richness. It appears that the number of species in mesic temperate floras within these regions is largely unrelated to the relatively narrow range of local climate factors associated with these floras. Analysis of covariance of the logarithm of species richness with the logarithm of area (b=0.148) and climate measurements as independent variables revealed a region effect, with species richness in eastern Asia exceeding that in eastern North America by 0.294 log₁₀ units, or a factor of 2.0. Similar regional differences in species richness were apparent in floras compiled from larger areas. Understanding differences in plant species richness between regions requires consideration of regional influences, whose effects should be tested in comparative analyses based on floristic surveys of ecologically characterized small areas.     

Persistence on inselbergs: the role of obligate seeders and resprouters

Aim To investigate if the current theories associated with recruitment strategies are sufficient to explain differences in the proportions of obligate seeders and resprouters on inselbergs and in the matrix. Location The New England Batholith of eastern Australia. Methods The importance of life form and regenerative response of flora species are compared for twenty‐four archipelagos of inselbergs habitat islands and for their adjacent matrix. Forward stepwise multiple linear regression is used to correlate measured and modelled variables with differences in the proportional abundance of obligate seeders on inselbergs at three levels of sampling. Results A total of 216 inselbergs were surveyed and information on 826 vascular plant species was collated. Herbs were the most common life form both on and off inselbergs. There were generally more shrubs on inselbergs than in the matrix. Resprouters were more common everywhere. However, obligate seeders were proportionately more common on inselbergs. The degree of insularity of outcrop floras accounted for 23–37% of the variance in the proportional abundance of obligate seeders at three sampling scales. Main conclusions A model is proposed whereby the mechanisms that influence the abundances of obligate seeders and resprouters are different on inselbergs and in the matrix. Inselberg environments are harsh, arid, have limited safe recruitment sites and below ground resources, but are not light limited. In such habitats, obligate seeders with persistence life‐history traits are favoured. Within the matrix in eastern Australia frequent biomass removal disturbances occur (such as fire) and resprouting is advantageous. High turnover obligate seeders with no persistence life‐history traits can be favoured in the matrix with a reduced disturbance regime and where competition for light still occurs. Some of these matrix obligate seeders occur on inselbergs due to their infrequent disturbance regimes.     

The effect of the taxon and geographic range size of host eucalypt species on the species richness of gall-forming insects

Abstract This field study was designed to test whether the taxonomic group and geographic range size of a host plant species, usually found to influence insect species richness in other parts of the world, affected the number of gall species on Australian eucalypts. We assessed the local and regional species richness of gall-forming insects on five pairs of closely related eucalypt species. One pair belonged to the subgenus Corymbia, one to Monocalyptus, and three to different sections of Symphyomyrtus. Each eucalypt pair comprised a large and a small geographic range species. Species pairs were from coastal or inland regions of eastern Australia. The total number of gall species on eucalypt species with large geographic ranges was greater than on eucalypt species with small ranges, but only after the strong effect of eucalypt taxonomic grouping was taken into account. There was no relationship between the geographic range size of eucalypt species and the size of local assemblages of gall species, but the variation in insect species composition between local sites was higher on eucalypt species with large ranges than on those with small ranges. Thus the effect of host plant range size on insect species richness was due to greater differentiation between more widespread locations, rather than to greater local species richness. This study confirms the role of the geographic range size of a host plant in the determination of insect species richness and provides evidence for the importance of the taxon of a host plant.     

Do climatically similar regions contain similar alien floras? A comparison between the mediterranean areas of central Chile and California

Aim Taxonomic comparisons of alien floras across climatically similar regions have been proposed as a powerful approach for increasing our understanding of plant invasions across scales. However, detailed comparisons between the alien biotas of climatically similar regions are scarce. This study aims to compare the taxonomic patterns of alien species richness in mediterranean‐type climate areas of central Chile and California, in order to better understand how climatically similar regions converge or diverge in terms of their alien flora. Location Central Chile and California, United States. Methods We compared the alien floras of the state of California in the United States and central Chile, considering within‐region variation and taxonomic composition up to the species level. To test for within‐region variation, administrative units and counties were grouped within seven latitudinal bands for each region. We tested for differences in the relative contributions of the various origins of the naturalized species to each region. We used a family naturalization index to establish which families had relatively higher numbers of naturalized species in each region. We evaluated the similarity, using cluster analyses with Jaccard’s similarity index, of alien taxa between regions and latitudinal bands using presence–absence matrices at the species, genus and family levels. We used principal components analysis to determine the presence of a compositional gradient including all latitudinal bands. Results We recorded 1212 alien plant species in California and 593 in central Chile, of which 491 are shared between the two regions. These figures include 25 species that are native to California and 37 that are native to Chile. A comparison between the alien floras of central Chile and California reveals three major trends: (1) higher naturalized species diversity for California than for Chile, at all taxonomic levels; (2) differences in the proportion of species according to origin, with America, Africa, Asia and Australia providing a larger number of species in California than in Chile; (3) segregation between regions in terms of taxonomic composition of their alien flora, and a rather weak differentiation within regions; and (4) a trend towards higher similarity between the alien floras of latitudinal bands associated with higher levels of human disturbances. Main conclusions The alien floras of central Chile and California are significantly different, but this difference diminishes in highly disturbed areas. Thus, the current high levels of species movement caused by globalization, together with increasing levels of anthropogenic disturbances, should reduce the differentiation of the alien floras in these regions, increasing overall biotic homogenization.     

Phytogeography, range size and richness of Australian endemic Sauropus (Euphorbiaceae)

Aim To investigate the distribution of Australian species of Sauropus. The information obtained is used to (1) identify areas of highest richness and centres of endemism, (2) investigate latitudinal gradients of richness and range size, (3) determine the types of rarity shown, and (4) provide hypotheses on historical biogeography of the genus within Australia. Location Australia. Methods Specimens from 17 herbaria and field searches were examined and label and field information collated on distribution, habit and habitat. Distribution information was used to map all species within 784 grid cells of 1° × 1° and within the 97 Australian ‘ecological regions’. Morphometric cluster analysis of species was conducted using Kulczynski association and flexible UPGMA on 23 character states. Simple regression was used to correlate species richness, density and range size to changes in latitude. CLIMEX is used to match the climate of the region of highest richness in Australia with other areas of the world. Results Species richness was highest within the tropical north of Australia, and most species were associated with tropical savanna woodlands. Two areas were identified as centres of endemism and these corresponded closely to areas of high species richness. Four morphological groups were identified. One species (Sauropus trachyspermus) was found to be widespread, however all other species had small geographical ranges. Species richness and range size were significantly correlated with changes in latitude. Ten species were found to be of the rarest type, warranting conservation initiatives. Main conclusions Two regions of high richness and endemism of Sauropus occur, Thailand and Australia. Within Australia, the Kakadu‐Alligator River and the Cairns‐Townsville areas were identified as centres of endemism and high species richness for Sauropus. Australian Sauropus in general occur in similar communities and climates as other members of the genus elsewhere. Ten of the 27 species of Australian endemic Sauropus are extremely rare and warrant conservation initiatives. Correlations of latitude to species richness are potentially due to Sauropus radiating from the climatically stable top end of Australia. Increasing range size in more southern latitudes may also be due to stability of climates in the top end or because there is more available land area at these latitudes. Sauropus micranthus, the only non‐endemic species, is probably a more recent invader from the Tertiary period when tropical rain forests where more extensive and congruent with those of New Guinea.     

Species richness, species range size and ecological specialisation among African primates: geographical patterns and conservation implications

The geographical distribution of species richness and species range size of African anthropoid primates (catarrhines) is investigated and related to patterns of habitat and dietary niche breadth. Catarrhine species richness is concentrated in the equatorial regions of central and west Africa; areas that are also characterised by low average species range sizes and increased ecological specificity. Species richness declines with increasing latitude north and south of the equator, while average species range size, habitat and dietary breadth increase. Relationships between species richness, species range size and niche breadth remain once latitudinal and longitudinal effects have been removed. Among areas of lowest species richness, however, there is increased variation in terms of average species range size and niche breadth, and two trends are identified. While most such areas are occupied by a few wide-ranging generalists, others are occupied by range-restricted specialist species. That conservation efforts increasingly focus on regions of high species richness may be appropriate if these regions are also characterised by species that are more restricted in both their range size and their ecological versatility, although special consideration may be required for some areas of low species richness.     

The effects of host-plant distribution and local abundance on the species richness of agromyzid flies attacking British umbellifers

Abstract. 1. The number of agromyzid species (Diptera: Agromyzidae) attacking British Umbelliferae generally increases with the size of the geographic range of the host, measured as occupied 10 km squares in the Atlas of the British Flora (Lawton & Price, 1979). 2. In the present study we tried to explain the large, residual variation in this species—area relationship using two new variables, namely the local abundance of the host plant, and the number of habitats within which it grows. 3. Local abundance was estimated from eight floras that map plant distributions within English countries by tetrads (2 times 2 km squares). Local abundance was defined as: Total number of occupied tetrads Total number of available tetrads within occupied 10 km squares 4. The number of habitats occupied by each host plant was taken from the only county flora to record plant habitats objectively, that for Warwickshire. 5. We expected to find a correlation between local abundance and the residuals from the national species—area relationship, with locally scarce plants having fewer agromyzids than expected from the sizes of their national ranges, and vice versa. 6. What we found was that size of geographic range and local abundance were highly correlated; hence their relative contributions to agromyzid species richness were difficult to disentangle. Residuals from the national species—area relationship were positively correlated with local abundance, but the relationship marginally failed to achieve statistical significance (P= 0.06). 7. In contrast, the number of habitats occupied by each species of umbellifer in Warwickshire had a marked effect upon agrornyzid species richness, with plants that grow in more habitats supporting more species of insects. Not surprisingly, local abundance and number of habitats occupied were highly correlated. 8. Lawton & Price's observation that aquatic umbellifers are faunally impoverished now emerges as part of the general effect of number of habitats occupied by the host plants on agromyzid species richness. 9. Once the number of habitats occupied by each host plant in Warwickshire was entered into a multiple regression, the effect of size of host geographic range on agromyzid species richness was no longer statistically significant. 10. A combination of the number of habitats occupied, and leaf-form of the host (the latter taken from Lawton & Price, 1979), explains 61% of the variation in agromyzid species richness on British Umbelliferae.     

Disparity between range map- and survey-based analyses of species richness: patterns, processes and implications

Species richness patterns are characterized either by overlaying species range maps or by compiling geographically extensive survey data for multiple local communities. Although, these two approaches are clearly related, they need not produce identical richness patterns because species do not occur everywhere in their geographical range. Using North American breeding birds, we present the first continent‐wide comparison of survey and range map data. On average, bird species were detected on 40.5% of the surveys within their range. As a result of this range porosity, the geographical richness patterns differed markedly, with the greatest disparity in arid regions and at higher elevations. Environmental productivity was a stronger predictor of survey richness, while elevational heterogeneity was more important in determining range map richness. In addition, range map richness exhibited greater spatial autocorrelation and lower estimates of spatial turnover in species composition. Our results highlight the fact that range map richness represents species coexistence at a much coarser scale than survey data, and demonstrate that the conclusions drawn from species richness studies may depend on the data type used for analyses.     

Richness of species and growth-forms within sclerophyll and mesophyll vegetation in eastern Australia

Abstract The patterns in total species richness and in the richness of the dominant growth-forms of vegetation communities of coastal sclerophyll and mesophyll vegetation in eastern Australia are examined. Plant species richness data were obtained from two 500 m² quadrats from 50 sites within a single geographical region north of Sydney, New South Wales. Concentrically nested subquadrats within each quadrat enabled the determination of species-area relationships for total species richness and its components. Three growth-forms were examined (trees, shrubs and ground cover) and patterns in the richness of these components were compared to those exhibited by total species richness. Total species richness was higher in sclerophyll communities on Hawkesbury Sandstone soils than in adjacent mesophyll communities on Narrabeen shales and sandstones. Significant patterns in total species richness within the two soil types were also found. Shrub and ground cover species richness showed strong correlations with total species richness, with higher richness in the sclerophyll communities. However, tree species richness contributed little to the patterns in total species richness. The results of this study suggest that differential patterns in the components of total species richness must be taken into account for effective modelling of natural areas based on species richness and diversity parameters.     

Crossing the (Wallace) line: local abundance and distribution of mammals across biogeographic barriers

Past and ongoing vertebrate introductions threaten to rearrange ecological communities in the Indo‐Malay Archipelago, one of Earth's most biodiverse regions. But the consequences of these translocations are difficult to predict. We compared local abundance and distributions in four tropical mammal lineages that have crossed from Asia to Wallacea or New Guinea. The local abundance of macaques (Macaca spp.), which naturally crossed Wallace's Line, was higher in Sulawesi (east of the line; mean = 3.7 individuals per camera station, 95% CI = 2.2: 5.1) than in Borneo (west of the line; mean = 1.1, CI = 0.8: 1.4), but the local abundance of Malay civets (Viverra tangalunga), Rusa deer, and Sus pigs was similar in their native ranges and where they had been introduced by humans east of Wallace's Line. Proximity to rivers increased Malay Civet local abundance and decreased the local abundance of pigs in parts of their introduced ranges (Maluku and New Guinea, respectively), while having no effect on local abundance in their native ranges (Borneo) or other areas where they have been introduced (Sulawesi). That local abundance was higher east of Wallace's Line in just one of four mammal lineages is consistent with findings from plant invasions, where most species have similar abundance in their native and introduced ranges. However, species’ ecology may change as they enter new communities, for example, their patterns of abundance at local scales. This could make it difficult to predict community structure in the face of ongoing species introductions.     

Contrasting alien and native plant species–area relationships: the importance of spatial grain and extent

Aim The proportion of alien plant species in floras is increasingly being used to indicate the threat of invasions to native species and/or the homogenization of biodiversity. However, this indicator is only valuable if it is independent of the spatial extent and grain of observation. This study tested the equivalence of native and alien species–area relationships (SARs) in order to assess the support for scale invariance in the proportion of alien species in floras. Location England, UK. Methods Nested SARs were generated by assessing the richness of native and alien plant species drawn from the New atlas of the British and Irish flora for six areas comprising 100, 400, 900, 1600, 2500 and 3600 km² with each larger area containing all smaller areas. Five replicate sets of nested areas encompassing northern, southern, eastern, western and central regions were chosen. For each set of nested areas, the log‐transformed species richness was regressed on log‐transformed area to fit a power function to the SAR. Results Native and alien plant SARs reveal consistent differences in slope, highlighting that the proportion of alien species is a function of spatial grain. Aliens are more rare than natives and have higher spatial turnover leading to faster accumulation of species as area increases. However, equivalent samples drawn from a larger spatial extent reveal similar alien and native SARs. Main conclusions The significant differential scale dependence in native and alien species richness observed in this study reflects dissimilar influences of regional drivers such as habitat, but potentially also propagule pressure and introduction history, that leads to the relative rarity and high spatial turnover of alien species. Maps of invasion hotspots that identify areas where the proportion of the alien flora is particularly high should therefore be treated with considerable caution since patterns across most grains used for species monitoring will be scale dependent.     

Explaining species richness from continents to communities: the time-for-speciation effect in emydid turtles

Speciation is the process that ultimately generates species richness. However, the time required for speciation to build up diversity in a region is rarely considered as an explanation for patterns of species richness. We explored this "time-for-speciation effect" on patterns of species richness in emydid turtles. Emydids show a striking pattern of high species richness in eastern North America (especially the southeast) and low diversity in other regions. At the continental scale, species richness is positively correlated with the amount of time emydids have been present and speciating in each region, with eastern North America being the ancestral region. Within eastern North America, higher regional species richness in the southeast is associated with smaller geographic range sizes and not greater local species richness in southern communities. We suggest that these patterns of geographic range size variation and local and regional species richness in eastern North America are caused by glaciation, allopatric speciation, and the time-for-speciation effect. We propose that allopatric speciation can simultaneously decrease geographic range size and increase regional diversity without increasing local diversity and that geographic range size can determine the relationship between alpha, beta, and gamma diversity. The time-for-speciation effect may act through a variety of processes at different spatial scales to determine diverse patterns of species richness.     

Species richness and distribution of eastern Australian lake chironomids and chaoborids

1. Chironomids and chaoborids were collected across eastern Australia and Tasmania in dune, glacial, sinkhole and maar lakes. Based on sampling exuviae from these relatively undisturbed freshwater lakes, we observed that species richness on the Australian continent was substantially greater than previously reported, and challenge the long‐standing view that chironomid species richness is depauperate in Australian lakes, compared with the northern hemisphere. 2. While chironomid species richness was equivalent across the four geographical regions sampled (tropical northern Queensland, Fraser Island, south‐eastern mainland Australia and Tasmania), there were only five ‘cosmopolitan’ species found across all regions. In general, species distributions were more closely associated with geographical region than with lake characteristics, and there were species assemblage differences among biogeographical regions. More than half of the 134 identified species were restricted to a single geographical region. Overall, Tasmanian lakes had the highest proportion of locally endemic species. 3. Latitude and altitude more strongly influenced species assemblages than did lake chemistry, although species richness sometimes varied among lake geomorphic types within a region.     

Interspecific competition constrains local abundance in highly suitable areas

Sites with high environmental suitability for species’ occurrence, in terms of abiotic conditions, may hold populations with higher local abundances by increasing reproductive and survival rates and decreasing extinction rate. Interspecific competition, however, may affect this relationship. Here we tested the hypothesis that local abundance of the gray slender opossum Marmosops incanus is affected by the local richness of potential competitors and environmental suitability derived from ecological niche models (ENMs). We also discuss the ability of distinct modelling methods to predict species’ abundance. We compiled occurrence records and information about M. incanus’ relative abundance from museums and published articles. Environmental suitability was derived from five algorithms using seven environmental predictors. To assess our hypothesis, we chose the best statistical models among generalised linear models and quantile regressions, and then tested whether the effects of richness of competitors on local abundance are stronger under highly suitable conditions. We found that environmental suitability given by presence-only methods are positively related to the maximum abundance of M. incanus. That is, species’ local abundance is low when suitability is low but can be either low or high when suitability is high. The richness of competitors, in turn, explains the abundance variation within sites with high environmental suitability. We strongly recommend that the relationship between abundance and suitability must be carefully interpreted when using ENMs to predict species’ distribution because biotic interactions can be the main driver of local abundance within highly suitable environments.     

Local ecological impacts of regional biodiversity on reef fish assemblages

Aim We examined comparative data for cryptobenthic reef fishes to determine how variation in regional species richness relates to local species richness, abundance, and taxonomic and trophic composition, and to test whether systems with higher species richness exhibit finer habitat partitioning. Locations Lizard Island, Great Barrier Reef (GBR), Australia; Bahía de Loreto, Gulf of California (GoC), Mexico. Methods Cryptobenthic reef fish assemblages from four habitats (coral heads, rubble, and horizontal and vertical surfaces of boulders) were collected using clove oil. Differences in density, species richness and biomass were examined between regions and among habitats. Habitat associations were identified for each habitat/location based on multivariate ordination, and the statistical significance of patterns was tested using analysis of similarity (ANOSIM). In addition, the trophic group composition of the assemblages for both regions was examined. Results A total of 91 species in 20 families were recorded (GBR, 66 species; GoC, 25 species). Total and habitat species richness were higher on the GBR, whereas biomass was higher in the GoC. No difference in fish density between regions was found. Habitat division among assemblages was greater in the depauperate GoC. Only coral head associations proved to be distinctive on the GBR, whereas three sample groups were found in the GoC (coral heads, horizontal boulders and vertical boulders/rubble). Trophic composition in the two regions was markedly different, with omnivores dominating the GBR fauna and planktivores the GoC. Main conclusions A positive regional–local relationship in fish diversity was found between regions, but fish abundance in both regions remained similar. Contrary to expectations, habitat partitioning, at a community level, was greater in the depauperate GoC. Differences in trophic composition and patterns of habitat use appear to reflect the disparate history of the regions, whereas patterns of abundance may reflect the influence of fundamental relationships between size and abundance in communities. This study highlights the potential of reef faunas to conform to universal numerical trends while maintaining an ability to respond ecologically to local/evolutionary influences. The GoC fauna appears to be exceptionally vulnerable to natural and anthropogenic disturbance owing to the high numerical dominance of habitat‐specific species and to the limited potential for functional redundancy within the system.     

Evolution of termite functional diversity: analysis and synthesis of local ecological and regional influences on local species richness

Aim To (1) describe termite functional diversity patterns across five tropical regions using local species richness sampling of standardized areas of habitat; (2) assess the relative importance of environmental factors operating at different spatial and temporal scales in influencing variation in species representation within feeding groups and functional taxonomic groups across the tropics; (3) achieve a synthesis to explain the observed patterns of convergence and divergence in termite functional diversity that draws on termite ecological and biogeographical evidence to‐date, as well as the latest evidence for the evolutionary and distributional history of tropical rain forests. Location Pantropical. Methods A pantropical termite species richness data set was obtained through sampling of eighty‐seven standardized local termite diversity transects from twenty‐nine locations across five tropical regions. Local‐scale, intermediate‐scale and large‐scale environmental data were collected for each transect. Standardized termite assemblage and environmental data were analysed at the levels of whole assemblages and feeding groups (using components of variance analysis) and at the level of functional taxonomic groups (using correspondence analysis and canonical correspondence analysis). Results Overall species richness of local assemblages showed a greater component of variation attributable to local habitat disturbance level than to region. However, an analysis accounting for species richness across termite feeding groups indicated a much larger component of variation attributable to region. Mean local assemblage body size also showed the greater overall significance of region compared with habitat type in influencing variation. Ordination of functional taxonomic group data revealed a primary gradient of variation corresponding to rank order of species richness within sites and to mean local species richness within regions. The latter was in the order: Africa > south America > south‐east Asia > Madagascar > Australia. This primary gradient of species richness decrease can be explained by a decrease in species richness of less dispersive functional taxonomic groups feeding on more humified food substrates such as soil. Hence, the transects from more depauperate sites/regions were dominated by more dispersive functional taxonomic groups feeding on less humified food substrates such as dead wood. Direct gradient analysis indicated that ‘region’ and other large‐scale factors were the most important in explaining patterns of local termite functional diversity followed by intermediate‐scale geographical and site variables and, finally, local‐scale ecological variables. Synthesis and main conclusions Within regions, centres of termite functional diversity lie in lowland equatorial closed canopy tropical forests. Soil feeding termite evolution further down food substrate humification gradients is therefore more likely to have depended on the long‐term presence of this habitat. Known ecological and energetic constraints upon contemporary soil feeders lend support for this hypothesis. We propose further that the anomalous distribution of termite soil feeder species richness is partly explained by their generally very poor dispersal abilities across oceans. Evolution, radiation and dispersal of soil feeder diversity appears to have been largely restricted to what are now the African and south American regions. The inter‐regional differences in contemporary local patterns of termite species richness revealed by the global data set point to the possibility of large differences in consequent ecosystem processes in apparently similar habitats on different continents.     

Plant species radiations: where,when, why?

The spatial and temporal patterns of plant species radiations are largely unknown. I used a nonlinear regression to estimate speciation and extinction rates from all relevant dated clades. Both are surprisingly high. A high species richness can be the result of either little extinction, thus preserving the diversity that dates from older radiations (a 'mature radiation'), or a 'recent and rapid radiation'. The analysis of radiations from different regions (Andes, New Zealand, Australia, southwest Africa, tropics and Eurasia) revealed that the diversity of Australia may be largely the result of mature radiations. This is in sharp contrast to New Zealand, where the flora appears to be largely the result of recent and rapid radiations. Mature radiations are characteristic of regions that have been climatically and geologically stable throughout the Neogene, whereas recent and rapid radiations are more typical of younger (Pliocene) environments. The hyperdiverse Cape and Neotropical floras are the result of the combinations of mature as well as recent and rapid radiations. Both the areas contain stable environments (the Amazon basin and the Cape Fold Mountains) as well as dynamic landscapes (the Andes and the South African west coast). The evolution of diversity can only be understood in the context of the local environment.     

The performance of range maps and species distribution models representing the geographic variation of species richness at different resolutions

Aim The method used to generate hypotheses about species distributions, in addition to spatial scale, may affect the biodiversity patterns that are then observed. We compared the performance of range maps and MaxEnt species distribution models at different spatial resolutions by examining the degree of similarity between predicted species richness and composition against observed values from well‐surveyed cells (WSCs). Location Mexico. Methods We estimated amphibian richness distributions at five spatial resolutions (from 0.083° to 2°) by overlaying 370 individual range maps or MaxEnt predictions, comparing the similarity of the spatial patterns and correlating predicted values with the observed values for WSCs. Additionally, we looked at species composition and assessed commission and omission errors associated with each method. Results MaxEnt predictions reveal greater geographic differences in richness between species rich and species poor regions than the range maps did at the five resolutions assessed. Correlations between species richness values estimated by either of the two procedures and the observed values from the WSCs increased with decreasing resolution. The slopes of the regressions between the predicted and observed values indicate that MaxEnt overpredicts observed species richness at all of the resolutions used, while range maps underpredict them, except at the finest resolution. Prediction errors did not vary significantly between methods at any resolution and tended to decrease with decreasing resolution. The accuracy of both procedures was clearly different when commission and omission errors were examined separately. Main conclusions Despite the congruent increase in the geographic richness patterns obtained from both procedures as resolution decreases, the maps created with these methods cannot be used interchangeably because of notable differences in the species compositions they report.     

Plant diversity,biogeography and environment in Iberia: Patterns and possible causal factors

Abstract. We associated patterns of plant diversity with possible causal factors by considering 93 local regions in the Iberian Peninsula and Balearic Islands with respect to biogeography, environmental favourability, and environmental heterogeneity, and their relationship with measured species diversity at four different scales: mean local species richness standardized at a grain of 100 m², total species richness in a community type within a region (regional community richness), mean compositional similarity, and mosaic diversity. Local regions in biogeographic transition zones to the North African and Atlantic floras had higher regional community richness and greater mosaic diversity than did non‐transitional regions, whereas no differences existed in mean local species richness or mean compositional similarity. Mean local species richness was positively related to environmental favourability as measured by actual evapotranspiration, but negatively related to total precipitation and temporal heterogeneity in precipitation. Mean local species richness was greatest in annual grassland and dwarf shrubland communities, and on calcareous bedrock types. Regional community richness was similarly related to actual evapotranspiration and total precipitation, but in addition was positively related to spatial heterogeneity in topography and soil water holding capacity. Mean compositional similarity decreased with increasing spatial heterogeneity and temperature seasonality. Mosaic diversity, a measure of complexity, increased with increasing local and regional richness. We hypothesize that these relationships can be explained by four ecological and evolutionary classes of causal factors: numbers of individuals, intermediate environments, limits to adaptation, and niche variation. These factors operate at various scales and manifest themselves in various ways. For example, at the site level, apparently processes that increase the number of individuals increase mean local species richness, but at the level of the entire region no such effects were found.     

Habitat management to reduce competitive interactions: case study of native and invading cottontails

Habitat management recommendations are often based on best available science determined through retroductive and inductive hypotheses. Such recommendations are not frequently tested, potentially resulting in the implementation of unreliable practices for management of imperiled species. The New England cottontail (Sylvilagus transitionalis) is an imperiled shrubland-obligate species whose recovery efforts include habitat management and restoration. Researchers suggest former best management practices for the species may result in ecological traps and new recommendations have been developed. We evaluated these newly revised best management practices designed to retain higher tree canopy closure to promote New England cottontails without encouraging eastern cottontails (Sylvilagus floridanus). We compared New England and eastern cottontail density between management plots (tree canopy thinned with all downed trees left on the ground, with or without invasive shrub treatment) and control plots (unmanaged) and examined the influence of management on resource selection and survival. Management strategies retaining higher canopy closure promoted stronger selection by New England cottontails than by eastern cottontails. Catch per unit effort of New England cottontails was greater than for eastern cottontails in management plots (P = 0.002). For both species, the proportion of the 95% home range overlapping managed areas was greater than the proportion of managed area in the habitat patch; however, for the 50% core area of the home range, this was only true for New England cottontails. When post-treatment canopy cover was >75%, New England cottontails selected canopy-thinning treatments without invasive shrub removal over unmanaged areas, but selection by eastern cottontails was unaffected by management treatment or canopy cover. Survival probability of both species was high and uncorrelated with time spent in management areas. Survival probability decreased as the average distance a rabbit moved in a 7-day period increased. Our results illustrate the need to revise management strategies that emphasize eliminating canopy cover when improving New England cottontail habitat is an objective, particularly where they are sympatric with eastern cottontails.