Patterns Of Species Turnover Research Articles

Global patterns of the beta diversity–energy relationship in terrestrial vertebrates

Patterns in beta diversity or species turnover, describing the change in species composition between places, have their wide implication for ecological and evolutionary issues. It is thought that beta diversity increases with increasing energy availability, but very few studies have directly tested this hypothesis. We examined the beta diversity–energy relationship for four classes of terrestrial vertebrates (mammals, birds, reptiles, and amphibians) in ecoregions across the world. The relationship was examined for each class in each of six biogeographic realms. We show that beta diversity is generally higher in areas with higher energy availability, measured as annual potential evapotranspiration. A higher level of beta diversity in areas with higher energy availability may have contributed to the well-known latitudinal diversity gradient (i.e., species richness increases towards the equator).

Ecological impacts of tropical forest fragmentation: how consistent are patterns in species richness and nestedness?

Large areas of tropical forest now exist as remnants scattered across agricultural landscapes, and so understanding the impacts of forest fragmentation is important for biodiversity conservation. We examined species richness and nestedness among tropical forest remnants in birds (meta-analysis of published studies) and insects (field data for fruit-feeding Lepidoptera (butterflies and moths) and ants). Species-area relationships were evident in all four taxa, and avian and insect assemblages in remnants typically were nested subsets of those in larger areas. Avian carnivores and nectarivores and predatory ants were more nested than other guilds, implying that the sequential loss of species was more predictable in these groups, and that fragmentation alters the trophic organization of communities. For butterflies, the ordering of fragments to achieve maximum nestedness was by fragment area, suggesting that differences among fragments were driven mainly by extinction. In contrast for moths, maximum nestedness was achieved by ordering species by wing length; species with longer wings (implying better dispersal) were more likely to occur at all sites, including low diversity sites, suggesting that differences among fragments were driven more strongly by colonization. Although all four taxa exhibited high levels of nestedness, patterns of species turnover were also idiosyncratic, and thus even species-poor sites contributed to landscape-scale biodiversity, particularly for insects.

Correction

Previous article FreeCorrectionAnna Papadopoulou, Ioannis Anastasiou, Foteini Spagopoulou, Malda Stalimerou, Sofia Terzopoulou, Anastasios Legakis, and Alfried P. VoglerAnna Papadopoulou1. Department of Entomology, Natural History Museum, London, United Kingdom2. Division of Biology, Imperial College London, Silwood Park Campus, Ascot, United Kingdom Search for more articles by this author , Ioannis Anastasiou3. Department of Biology, University of Athens, Panepistimioupolis, Athens, Greece Search for more articles by this author , Foteini Spagopoulou3. Department of Biology, University of Athens, Panepistimioupolis, Athens, Greece Search for more articles by this author , Malda Stalimerou3. Department of Biology, University of Athens, Panepistimioupolis, Athens, Greece Search for more articles by this author , Sofia Terzopoulou3. Department of Biology, University of Athens, Panepistimioupolis, Athens, Greece Search for more articles by this author , Anastasios Legakis3. Department of Biology, University of Athens, Panepistimioupolis, Athens, Greece Search for more articles by this author , and Alfried P. Vogler1. Department of Entomology, Natural History Museum, London, United Kingdom2. Division of Biology, Imperial College London, Silwood Park Campus, Ascot, United Kingdom Search for more articles by this author Original articleTesting the Species–Genetic Diversity Correlation in the Aegean Archipelago: Toward a Haplotype-Based Macroecology?PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreAfter the publication of “Testing the species–genetic diversity correlation in the Aegean archipelago: toward a haplotype-based macroecology?” by Anna Papadopoulou et al. (American Naturalist 178:241–255), the authors discovered a typographical error, which does not affect any results or conclusions of the article.In table A2 in the online appendix, four rows need to be corrected. The correct rows follow:Table A2. Taxonomic species and morphospecies collected from each of the 15 central Aegean islands AndrosAno KoufonisiAntiparosDonoussaHerakleiaIkariaKosMilosMykonosNaxosParosPatmosSerifosSifnosTínosTurkeyM. GreeceGraecopachys quadricollis (Brülle 1832)XX XX X XX XXX XPachyscelis villosa (Drapiez 1820)X XX XXXXX Raiboscelis azureus (Brullé 1832)X X XX X XX X Raiboscelis coelestinus (Wahl 1838) X X X X X View Table Image Previous article DetailsFiguresReferencesCited by The American Naturalist Volume 178, Number 4October 2011 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/662555 Views: 197Total views on this site Citations: 4Citations are reported from Crossref HistorySubmitted July 26, 2011Accepted July 26, 2011Published online September 13, 2011 © 2011 by The University of Chicago. All rights reserved.PDF download Crossref reports the following articles citing this article:Andrés Baselga, Carola Gómez‐Rodríguez, Miguel B. Araújo, Adrián Castro‐Insua, Miguel Arenas, David Posada, Alfried P. Vogler Joint analysis of species and genetic variation to quantify the role of dispersal and environmental constraints in community turnover, Ecography 2022, no.55 (Mar 2022).https://doi.org/10.1111/ecog.05808Andrea Freijeiro, Andres Baselga Spatial and environmental correlates of species richness and turnover patterns in European cryptocephaline and chrysomeline beetles, ZooKeys 597 (Jun 2016): 81–99.https://doi.org/10.3897/zookeys.597.6792Andrés Baselga, Carola Gómez-Rodríguez, Alfried P. Vogler Multi-hierarchical macroecology at species and genetic levels to discern neutral and non-neutral processes, Global Ecology and Biogeography 24, no.88 (May 2015): 873–882.https://doi.org/10.1111/geb.12322Andrés Baselga, Tomochika Fujisawa, Alexandra Crampton-Platt, Johannes Bergsten, Peter G. Foster, Michael T. Monaghan, Alfried P. Vogler Whole-community DNA barcoding reveals a spatio-temporal continuum of biodiversity at species and genetic levels, Nature Communications 4, no.11 (May 2013).https://doi.org/10.1038/ncomms2881Related articlesTesting the Species–Genetic Diversity Correlation in the Aegean Archipelago: Toward a Haplotype-Based Macroecology?17 Jul 2015The American Naturalist

Species richness and turnover patterns in European tenebrionid beetles

Abstract. 1. We used a hyperdiverse invertebrate group, tenebrionid beetles, to test competing hypotheses about the factors correlated with the spatial variation in species richness and composition across Europe.2. We considered the following hypotheses for explaining variation in species richness, (i) spatial heterogeneity, (ii) environmental energy, and (iii) dispersal limitation and post‐glacial recolonisation, and the following hypotheses for variation in species composition, (i) current climate, (ii) Pleistocene glaciations, and (iii) neutral dynamics.3. We used inventories of 36 European territories, built from a database containing the distributions of 1010 species or subspecies. Area, spatial position, and topographical and climatic variables were used as predictors in regression (richness) and constrained analysis of principal coordinates (composition) analyses.4. The latitudinal richness gradient found in European tenebrionids was mostly explained by the joint effect of environmental and spatial variables, supporting the climate and incomplete recolonisation hypotheses.5. A parabolic relationship of endemism with longitude points to the presence of centres of endemism in the Iberian Peninsula and the Balkans. Current climatic conditions alone were not sufficient to explain spatial turnover patterns of European tenebrionids, which are largely influenced by spatial factors.6. Both the Pleistocene glaciations and neutral hypotheses were supported, but the fact that turnover is not uniform across Europe suggests that the historical effects of Pleistocene glaciations had a deeper impact on tenebrionid assemblages than neutral dynamics. Thus, variation in species richness seems more directly controlled by climatic factors, whereas geographical constraints related to dispersal limitation or stochastic colonisation events influenced species composition.

Coastal dry forests in northern Mozambique

Background and aims - The Coastal Forests of Eastern Africa, stretching along the Indian Ocean coastline from Somalia to Mozambique, are considered by Conservation International to be a global biodiversity hotspot - an area of high diversity and endemism under increasing threat. Although the largest remaining extent of these forests is reported to be found in Mozambique, very little is known on their extent, condition and composition here. In addition, the term 'coastal forest' has been used in different ways by different authors. This paper defines and characterises coastal dry forests found in northern Mozambique and assesses their present extent, botanical composition, conservation importance and the threats to these forests. Methods - The study area of 18,150 km2 lies in Cabo Delgado Province in north-east Mozambique, adjacent to Tanzania. Its limits are determined primarily by geological substrate and landform. Four smaller study sites were chosen covering a range of landforms. Manual interpretation of satellite imagery dating from 1999-2002 was used to calculate possible previous and present extent of 'dense vegetation'. Extensive field collecting was used in determining botanical composition and distribution patterns. IUCN Red List assessments were carried out on selected species using distributional criteria. Results - Dry forests similar to those in southern Tanzania are found widely scattered across coastal Cabo Delgado, sitting in a matrix of miombo woodland and other vegetation types. However, forest cover is not as extensive was believed. We calculate that the original extent of 'dense vegetation cover', which includes coastal dry forest, was 6087 km2. Owing to clearance over the last 150 years this is now only 1182 km2, of which perhaps only 400 km2 is moderately-intact dry forest. In this southern part of their range such forests are essentially dry, not moist and mesic, and dominated by a high proportion of deciduous or sclerophyllous evergreen trees. The plant species composition differs significantly from that of the surrounding woodlands. There is a marked change in species composition between forest patches along the coast, and they contain numerous species with restricted global distribution. Since 2003, 68 species new to Mozambique have been recorded from Cabo Delgado in addition to 36 possible new species. Many new records are of species previously only known from south-eastern Tanzania. Previously recorded patterns of restricted distribution and high species turnover between forest patches in Kenya and Tanzania are confirmed. Seven coastal forest species were assessed as Endangered. Regional context and conservation - Coastal dry forests are discussed in relation to the more widespread 'sand forests' of the continental interior of south-central Africa, and shown to have similarities in ecology, species composition, soils and ecology. Very little of the present extent of coastal forests in Mozambique lies within protected areas. The threats to their continued existence in the face of exploitation for timber, agriculture and oil exploration are outlined.

Disentangling the effects of geographic distance and environmental dissimilarity on global patterns of species turnover

ABSTRACTAim To distinguish the effects of geographic distance and environmental dissimilarity on global patterns of species turnover in four classes of terrestrial vertebrates (mammals, birds, reptiles and amphibians).Location Six hundred and sixty terrestrial ecoregions across the globe.Methods We calculated species turnover between each pair of ecoregions, using the Jaccard index (J). We selected seven variables to quantify environment in each ecoregion, and subjected the environmental values to a principal components analysis. For each realm, we applied multiple regression analysis relating the natural logarithm of the Jaccard index (lnJ) to geographic distance alone and in combination with differences in the environment variables measured as principal components (PC). We used partial correlations to partition variance in lnJ between unique contributions of distance and environmental PC scores, the covariation between distance and environment, and unexplained variance. To examine the latitude and species turnover relationship, we regressed lnJ on latitude with distance between ecoregions being included as a covariate.Results The natural logarithm of the Jaccard index (lnJ) decreased significantly with increasing geographic distance for all vertebrate classes in each zoogeographic realm, and the slopes of the relationships per 1000 km ranged from −0.251 to −1.043. With environmental differences included in the analysis, both geographic distance and environmental differences were substantial predictors of lnJ for every combination of taxon and realm. On average, the unique contribution of geographic distance to variation in species turnover between ecoregions was about 1.4 times that of the environmental differences between ecoregions. Species turnover generally decreased with increasing latitude when controlling for geographic distance. The value of lnJ for each vertebrate class was highly and positively correlated with those of the other vertebrate classes.Main conclusions Our analyses suggest that both dispersal‐based and niche‐based processes have played important roles in determining faunal similarities among vertebrate assemblages at the spatial scale examined. Furthermore, reptiles and amphibians exhibited greater distance‐independent faunal heterogeneity among ecoregions and greater turnover among ecoregions with respect to geographic and environmental distance than birds and mammals.

Properties of Similarity Indices under Niche-Based and Dispersal-Based Processes in Communities

Little is known about the combined impact of habitat filtering and dispersal limitation on species turnover patterns. To gain new insights, we constructed a spatially explicit community model wherein we controlled dispersal distances, the strength of habitat filtering, and the grain of habitat heterogeneity to study the distance decay of several (dis)similarity indices. The impact of habitat filtering is dependent on the ratio between the grain of habitats and the mean dispersal distance. The behavior of (dis)similarity indices varies. First, incidence-based measures of species overlap are less affected by habitat filtering than are abundance-based indices. Second, species identity-based indices, derived from population genetics' F(ST), show interesting capacities to infer dispersal processes under neutrality but are also highly sensitive to habitat filtering. All indices except F(ST)-related indices under neutrality are very sensitive to overall species richness. Hence, community patterns showing contrasted diversity levels should be compared with caution. Partitioning similarity indices within and between habitats appears to be an efficient approach to assess the strength of habitat filtering, and we show that a torus-translation test is powerful for this purpose. We finally highlight the need for further analytical studies to achieve theoretical expectations of similarity decay under dispersal and niche processes.

Patterns of plant species turnover along grazing gradients

Questions: How are plant species distributed along grazing gradients? What is the shape of species richness patterns? How can we test for the existence of potential discontinuities in species turnover pattern? Location: Semi-deserts in the eastern Caucasus, Azerbaijan, Gobustan district. Methods: We studied the distribution of vascular plant species along transects 900-m long, perpendicular to five farms, and estimated grazing intensity as current livestock units per distance. We modelled species response curves with Huismann–Olff–Fresco (HOF) models and calculated species turnover by accumulating the first derivatives of all response curves. To test for potential discontinuities in changes of vegetation composition along the grazing gradient, we introduce a new null model based on the individualistic continuum concept that uses permutations of the observed pattern of species responses. Results: Most species show a sigmoidal negative response to grazing intensity, while a few species respond with a unimodal pattern. The monotonic decrease in species richness with increasing grazing intensity marks a process of overgrazing that leads to the complete extirpation of plant species. Although the species turnover pattern shows a clear peak, it does not deviate significantly from the null model of individualistic continuous changes. Conclusions: Our approach offers a method for differentiating between transition zones and continuous shifts in species composition along ecological gradients. It also provides a valuable tool for rangeland management to test state-and-transition concepts and gives deeper insights into ecological processes affected by grazing.

PLANKTIC FORAMINIFERAL SPECIES TURNOVER ACROSS DEEP-SEA APTIAN/ ALBIAN BOUNDARY SECTIONS

A major planktic foraminiferal species turnover accompanied by a dramatic reduction in shell size, a fundamental change in shell architecture, and a precipitous drop in the abundance of planktic relative to benthic species occurs across the Aptian/Albian boundary interval (AABI) at globally distributed deep-sea sections. Extinction of the large and distinctive planktic foraminifer Paraticinella eube-jaouaensis , used to denote a level at or near the Aptian/ Albian boundary, coincides with the extinctions of relatively long-ranging Aptian species of Hedbergella and Globiger-inelloides . At Deep Sea Drilling Project (DSDP) Site 511 (southern South Atlantic), which is the most complete and best preserved of the studied AABI sections, the Aptian assemblage is of low diversity and species are replaced by initially one and then two very small, smooth-surfaced, thin-walled species of Microhedbergella n. gen. The oldest species of this genus, Mi. miniglobularis n. sp., probably descended from Hedbergella praelippa n. sp. and is the nominate taxon for a new lowermost Albian interval zone and is considered ancestral to several small, gradually evolving microperforate species, including Mi. praeplanispira n. sp., Mi. pseudopla-nispira n.sp., and Mi. pseudodelrioensis n. sp., which range into the middle and upper Albian. The small hedbergellids that characterize the Mi. miniglobularis Interval Zone at Site 511 have also been identified from samples taken just above the Kilian black shale level in the Vocontian Basin of southeast France. The Albian record at Site 511 reveals a gradual increase in planktic foraminifera shell size and assemblage dominance, as well as the gradual evolution during the middle Albian of species characterized by a finely perforate, pustulose test. Taxa with this shell infrastructure are included in Muricohedbergella n. gen. A new “ Ticinella yezoana ” Partial Range Zone is erected at Site 511 for correlation of the middle-upper Albian at high latitudes. At Ocean Drilling Program (ODP) Site 1049 (western North Atlantic), which also yields well-preserved foraminifera across the AABI, Aptian species of Hedbergella , Globiger-inelloides , and Pseudoguembelitria blakenosensis n. gen., n. sp. are replaced by lower Albian assemblages composed only of two minute species of Microhedbergella . However, this boundary section is considered incomplete because of the absence of the Mi. miniglobularis Zone. A new upper lower Albian Ti. madecassiana Zone is defined at Site 1049 for the interval between the lowest occurrence (LO) of the nominate taxon and the LO of Ti. primula , the nominate species of the middle Albian Ti. primula Zone. The AABI at DSDP Site 545 (eastern North Atlantic) has a major unconformity spanning the uppermost Aptian through the upper Albian. A black shale sequence previously placed in the lower Albian and designated as Oceanic Anoxic Event 1b is now determined to be latest Aptian in age. The AABI at ODP Site 763 (southeast Indian Ocean) is also marked by an unconformity between the upper Aptian Pa. eubejouaensis Zone and the lower Albian Mi. rischi Zone. This site needs further study to resolve whether overlap of species from both zones is the result of downslope reworking or an exception to the pattern of abrupt species turnover observed at the other deep-sea sites. The dramatic changes in planktic foraminiferal assemblages across the AABI suggest major changes in carbonate chemistry, vertical stratification, or productivity in the surface mixed layer occurred during the last 1 myr of the Aptian. Understanding the cause or causes for these changes will require much further investigation.

Quantifying the influence of environmental texture on the rate of species turnover: evidence from two habitats

The environmental texture hypothesis (ETH) proposes that the spatial geometry or texture of the environment influences the rate at which species are accumulated in space or time. Specifically, the ETH suggests that regions, and spatial scales, that exhibit a larger rate of environmental distance decay (DD) should exhibit more rapid rates of species turnover. The ETH should apply over any range of scales where the environment is driving species distributions. To examine the relevance of the ETH at local spatial scales, we tested for a positive relationship between the rate of change in soil chemical properties and vascular plant species composition in grassland and woodland habitats. We recorded presence–absence data along a 1.883 km transect in each habitat and estimated the rate of turnover and environmental DD for spatial lags of 1–41 m. We found that the soil environment explained spatial patterns of species composition more accurately in the grassland habitat compared to the woodland habitat. Consequently the rate of change in soil properties as a function of spatial distance was significantly positively correlated with the rate of species turnover in the grassland but not the woodland. Our study suggests that one of the central premises of the ETH is relevant for local patterns of species turnover if the environment appears to influence species composition.

Low beta diversity of Maastrichtian dinosaurs of North America

Beta diversity is an important component of large-scale patterns of biodiversity, but its explicit examination is more difficult than that of alpha diversity. Only recently have data sets large enough been presented to begin assessing global patterns of species turnover, especially in the fossil record. We present here an analysis of beta diversity of a Maastrichtian (71-65 million years old) assemblage of dinosaurs from the Western Interior of North America, a region that covers approximately 1.5 x 10(6) km(2), borders an epicontinental sea, and spans approximately 20 degrees of latitude. Previous qualitative analyses have suggested regional groupings of these dinosaurs and generally concluded that there were multiple distinct faunal regions. However, these studies did not directly account for sampling bias, which may artificially decrease similarity and increase turnover between regions. Our analysis used abundance-based data to account for sampling intensity and was unable to support any hypothesis of multiple distinct faunas; earlier hypothesized faunal delineations were likely a sampling artifact. Our results indicate a low beta diversity and support a single dinosaur community within the entire Western Interior region of latest Cretaceous North America. Homogeneous environments are a known driver of low modern beta diversities, and the warm equable climate of the late Cretaceous modulated by the epicontenental seaway is inferred to be an underlying influence on the low beta diversity of this ancient ecosystem.

Hot, dry and different: Australian lizard richness is unlike that of mammals, amphibians and birds

ABSTRACTAims (1) To map the species richness of Australian lizards and describe patterns of range size and species turnover that underlie them. (2) To assess the congruence in the species richness of lizards and other vertebrate groups. (3) To search for commonalities in the drivers of species richness in Australian vertebrates.Location Australia.Methods We digitized lizard distribution data to generate gridded maps of species richness and β‐diversity. Using similar maps for amphibians, mammals and birds, we explored the relationship between species richness and temperature, actual evapotranspiration, elevation and local elevation range. We used spatial eigenvector filtering and geographically weighted regression to explore geographical patterns and take spatial autocorrelation into account. We explored congruence between the species richness of vertebrate groups whilst controlling for environmental effects.Results Lizard richness peaks in the central deserts (where β‐diversity is low) and tropical north‐east (where β‐diversity is high). The intervening lowlands have low species richness and β‐diversity. Generally, lizard richness is uncorrelated with that of other vertebrates but this low congruence is strongly spatially structured. Environmental models for all groups also show strong spatial heterogeneity. Lizard richness is predicted by different environmental factors from other vertebrates, being highest in dry and hot regions. Accounting for environmental drivers, lizard richness is weakly positively related to richness of other vertebrates, both at global and local scales.Main conclusions Lizard species richness differs from that of other vertebrates. This difference is probably caused by differential responses to environmental gradients and different centres of diversification; there is little evidence for inter‐taxon competition limiting lizard richness. Local variation in habitat diversity or evolutionary radiations may explain weak associations between taxa, after controlling for environmental variables. We strongly recommend that studies of variation in species richness examine and account for non‐stationarity.

Patterns of ant species diversity and turnover across 2000 km of Amazonian floodplain forest

AbstractAim To determine the effect and relative importance of geographic and local environmental factors on species richness and turnover of ant assemblages in floodplain forests across the Amazon basin.Location Twenty‐six mature forest sites scattered along the entire extension of the Amazon River in Brazil. The study area encompassed nearly 18° of longitude and 3.5° of latitude.Methods Systematic collections of ants were performed at each site during the low‐water season (i.e. when forests are not inundated) using three complementary sampling methods. We used variance partitioning techniques to assess the relative effects of the spatial (latitude and longitude) and environmental (rainfall, length of the dry season and flood height) variables on ant species richness and composition.Results There was a twofold variation in the number of species per site, which was largely explained by inter‐site variations in rainfall seasonality and flooding intensity. In general, there were more species at sites located in the western part of the basin, where the dry season is less severe, or near the river estuary, where precipitation is also high and flooding is less intense. Ant community composition was also affected by environmental heterogeneity. For instance, some species only occurred at those sites less affected by the river’s seasonal flooding, whereas others were mostly associated with the drier or wetter regions of the basin. In addition, the turnover of species increased significantly as geographic distances increased. Nevertheless, the rate of change was small given that many species had a broad distribution across the study area.Main conclusions Ant distribution patterns along the floodplain forests of the Amazon appear to be controlled to a relatively large extent by the current gradient in flooding intensity and – most importantly – in precipitation. Altered rainfall regimes resulting from global warming and land‐use change thus have the potential to influence these patterns.

Biodiversity in a forest-agriculture mosaic – The changing face of West African rainforests

The biodiversity of West African rainforests is globally significant but poorly described, little understood in terms of its functional significance, and under threat from forest loss and degradation. Estimates suggest that about 10 million ha of forest may have been lost in the 20th Century, and around 80% of the original forest area is now an agriculture-forest mosaic. These highly modified forests provide food, fuel, fibre and a range of ecosystem services for over 200 million people. As a consequence, the future of biodiversity in the region is intimately linked with the lives and livelihoods of local people. The available evidence suggests that forest loss and degradation has been caused primarily by agricultural expansion, sometimes facilitated by other human activities such as wood extraction. This expansion is a response to the demand generated by a growing and increasingly urbanised human population, but has been exacerbated by small increases in crop yields over recent decades. We synthesize and review our state of knowledge on the value of human-modified habitats for forest biodiversity in the region. Data on biodiversity are patchy, but we show that across plant, invertebrate and vertebrate groups, there is a significant loss of forest species as tree cover is reduced and vegetation structure simplified. Agricultural expansion clearly causes significant local biodiversity loss. We argue that replicated landscape-scale studies are now needed that describe changes across a range of biodiversity groups (above and below ground) in relation to land-use and landscape context to address knowledge gaps and biases. Such descriptive studies need to be complemented by a deeper understanding of the causes of species turnover patterns, together with work on the consequences of biodiversity loss for ecosystem function and services. Biodiversity conservation in the region is becoming increasingly embedded within a more multi-functional view of agriculture-forest mosaics that attempts to recognise and value the range of services provided by tree cover and other land-uses. This relatively new perspective has the potential, at least in principle, to re-shape the drivers of land-use change because tree cover can generate additional revenue through carbon trading or certification schemes. It will become clearer over the coming decades whether this potential can be realised, but the implications for biodiversity conservation in the region are potentially profound. The socio-economic processes that have driven forest loss and degradation in West Africa are having an increasing impact on the relatively undisturbed rainforest of the Congo Basin. We conclude by pointing out that while West African forest landscapes are a potent reminder of what might happen in Central Africa in the near future, they also provide insights for developing policies and practice that might avoid comparable levels of forest loss and degradation.

Spectral variation versus species β-diversity at different spatial scales: a test in African highland savannas

Few studies exist that explicitly analyse the effect of grain, i.e. the sampling unit dimension, on vascular plant species turnover (beta-diversity) among sites. While high beta-diversity is often a result of high environmental heterogeneity, remotely sensed spectral distances among sampling units may be used as a proxy of environmental gradients which spatially shape the patterns of species turnover. In this communication, we aimed to (i) test the potential relation between spectral variation and species beta-diversity in a savanna environment and to (ii) investigate the effect of grain on the achieved patterns. Field data gathered by the BIOTA Southern Africa biodiversity monitoring programme were used to model the relation between spectral variation and species turnover at different spatial grains (10 m x 10 m and 20 m x 50 m). Our results indicate that the overall fit was greater at the larger grain size, confirming the theoretical assumption that using a lower grain size would generally lead to a higher noise in the calculation of species turnover. This communication represents one of the first attempts at relating beta-diversity to spectral variation, while incorporating the effects of grain size in the study. The results of this study could have significant implications for biodiversity research and conservation planning at a regional or even larger spatial scale.

Patterns of species turnover in plant‐pollinator communities along a precipitation gradient in Patagonia (Argentina)

AbstractRecent studies have assessed the influence of different types of gradients (e.g. altitudinal, latitudinal and temporal, among others) on the structure and function of community‐level plant‐pollinator webs. Although the importance of humidity as a major driver of species‐richness gradients worldwide has been stressed by recent reviews, no studies have been specifically designed to address the influence of precipitation gradients on pollination webs. In the present paper we describe for the first time the turnover of species of plants and their associated flower visitors between eight communities located along a steep precipitation gradient in north‐west Patagonia, Argentina. Our results show that: (i) there is a high spatial turnover of plant communities and their associated pollinators; (ii) this turnover is strongly related to precipitation changes across the region; and (iii) the turnover rate is similar for plants and pollinators. Our results support the view that the precipitation gradient is a significant factor associated with the regional turnover of plants and their pollinators in the temperate forests of southern South America.

Patterns of species richness and turnover along the pH gradient in deciduous forests: testing the continuum hypothesis

AbstractQuestion: (i) How do species richness and species turnover change along a pH gradient? (ii) What are possible driving factors behind these patterns? (iii) Can the observed patterns be explained by an individualistic continuum concept that postulates independence of species responses and constant turnover rates?Location: Semi‐natural, deciduous hardwood forests in NW Germany (558 plots).Methods: The instantaneous rate of compositional turnover is measured by the sum of slope angles of modelled response curves (119 understorey species) at any point along the pH gradient. Total turnover rate, positive turnover rate (species increasing in probability of occurrence) and negative turnover rate (species decreasing in probability of occurrence) are calculated separately. Species richness is modelled using Poisson regression and by calculating the sum of predicted probabilities at any gradient point. Turnover rates are compared with those calculated from a null model based on a Gaussian community model. Soil chemical analyses of 49 plots are used to interpret biodiversity patterns.Results: Species richness shows a hump‐shaped relation to pH(CaCl2) with a minor decline at approximately pH>5.0. The decline is possibly due to the confounding influence of water regime and local species pool effects. Increasing richness from pH 2.5 to 4.7 can be traced back to positive turnover exceeding negative turnover. Peaks in turnover rates, dominated by positive turnover, are located at pH 3.7 and 2.8, where turnover rates considerably exceed rates derived from the null model. The turnover pattern can be related to soil chemical conditions, e.g. decreasing base saturation, Al and H+ toxicity and the occurrence of mor.Conclusions: The high turnover rates and the massive imbalance in positive and negative turnover rates found in deciduous forests cannot be explained by the individualistic continuum concept. Physiological constraints at the gradient limits and species pool effects could be responsible for this. Their role should be considered more explicitly in vegetation concepts dealing with the continuum‐discontinuum controversy. The presented approach can be regarded as a comprehensive analytical tool for a better understanding of biodiversity patterns along environmental gradients by linking species richness, turnover and response curve types.

Understanding fragmentation: snails show the way

Understanding fragmentation: snails show the way

Fragmentation and pre‐existing species turnover determine land‐snail assemblages of tropical rain forest

AbstractAim The main aims of the study were: (1) to investigate the effect of fragment age in relation to other patch‐ and landscape‐scale measures of forest fragmentation, and (2) to assess the relative importance of fragmentation, habitat degradation (i.e. degradation caused by selective logging and past shifting cultivation) and putative pre‐existing species turnover in structuring current land‐snail assemblages.Location South‐western Sri Lanka.Methods The land‐snail fauna was sampled using standardized belt transects. Fifty‐seven transects were sampled in 21 lowland rain forest fragments (c. 1–33,000 ha). The spatial arrangement of fragments in the study area was explicitly considered in an effort to take into account the non‐random nature of fragmentation and degradation and the possibility that current species composition may reflect patterns of species turnover that existed prior to fragmentation. The data set of 57 land‐snail species and 28 environmental and spatial variables was analysed using canonical correspondence analysis and partial canonical correspondence analysis.Results Fragment age, mean shape complexity (i.e. a landscape‐scale measure of shape complexity), altitude, and the spatial variables x (longitude), y (latitude) and y2 explained significant variation in land‐snail species composition. None of the three nominal variables quantifying habitat degradation was significantly correlated with variation in species composition. The independent effects of fragment age and mean shape complexity were similar. The combined effect of the spatial variables alone was larger than the independent effects of fragment age, mean shape complexity or altitude, but was of the same order of magnitude. The total variation explained by the spatial variables was comparable to the total non‐spatial variation accounted for by fragment age, mean shape complexity and altitude.Main conclusions Fragment age was found to be one of only two key determinants (the other was shape complexity at the landscape scale) driving fragmentation‐related changes in community composition. The influence of pre‐fragmentation patterns of species turnover on assemblage structure can be stronger than the effects of fragmentation measures, such as age, and may override the effects of forest degradation. Thus, strong patterns of pre‐existing turnover may potentially confound interpretation of the effects of forest fragmentation and degradation.

Diversity, endemism and species turnover of millipedes within the south‐western Australian global biodiversity hotspot

AbstractAim To examine how current and historical environmental gradients affect patterns of millipede (Diplopoda) endemism and species turnover in a global hotspot of floristic diversity, and to identify regions of high endemism and taxonomic distinctness for conservation management.Location South‐western Australia.Methods Museum database records of millipedes (subclasses Pentazonia and Helminthomorpha), supplemented with extensive fieldwork, were used to map species richness, species turnover (β‐diversity), weighted endemism, average taxonomic distinctness and variation in taxonomic distinctness in half‐degree grid squares (c.2500 km2). Generalized linear models were used to examine relationships between these parameters with rainfall (present day and historical), topography and human disturbance (clearing for agriculture and urbanization).Results Millipede species richness, particularly within the order Spirostreptida, and millipede endemism were positively associated with large within‐cell differences in elevation (mountainous regions). Large variation in taxonomic distinctness (unevenness in the taxonomic tree) in higher‐rainfall areas was mainly due to speciation within the Spirostreptida genusAtelomastix. Hotspots of millipede endemism and taxonomic distinctness were identified within three categories of importance: primary (Stirling Range East, Cape Le Grand, Cape Arid, Walpole, Porongurups), secondary (Mount Manypeaks, Bremer Bay, Stirling Range West, Duke of Orleans Bay, Ravensthorpe, Albany, Busselton) and tertiary (Nornalup). A species turnover boundary was positively associated with rainfall, broadly located in the transition zone of 300–600 mm year−1.Main conclusions The current lack of knowledge on the endemism of invertebrates hampers their incorporation into conservation planning. With this knowledge we can identify global biodiversity hotspots and, at a smaller scale, significant conservation areas within a region. Here we have shown that weighted endemism and taxonomic distinctness are useful tools in identifying centres of high endemism and speciation for millipedes within the south‐west Australian hotspot. Moreover, it is unlikely that either vertebrates or vascular plants will be useful surrogates for identifying significant areas for invertebrate conservation. While other workers have shown that vascular plants, mammals and frogs have different centres of endemism within south‐west Australia, our results show that centres of endemism for millipedes encompass all of these plus other areas.