Niche conservatism and species richness patterns of squamate reptiles in eastern and southern Africa

Niche conservatism has been proposed as a mechanism influencing large‐scale patterns of taxonomic richness. We document the species richness patterns of five monophyletic squamate reptile groups (gekkonids, cordylids‐scincids, lacertids, chameleons and alethinophidian snakes) in eastern and southern Africa, and explore if observed patterns reflect niche conservatism processes. We quantified richness and its relationships with current climatic conditions by gridding species' range maps at 110 × 110 km. Also, dated phylogenies and palaeoclimatic reconstructions, coupled with evidence from the fossil record, were used to approximate the areas and climate characteristics in which each group originated and/or radiated. Mean species richness and geographically corrected confidence intervals in current climate types were calculated for each group in order to establish their climatic preferences. On average, the species richness of older groups (gekkonids, cordylids‐scincids and lacertids) was lower in equatorial climates and higher in arid and temperate conditions, whereas more recent groups (chameleons and alethinophidian snakes) were richer in equatorial and temperate climates and less rich in arid conditions. Across all groups, higher richness was associated with climatic characteristics similar to those prevailing at the time in which each group originated/radiated. The congruence of the current climates where reptile groups are richer and the past climates amidst which those groups originated is consistent with an explanation for their diversity gradients based on niche conservatism.     

Plio-Pleistocene Carnivora of northwestern Africa: A short review

The fossil record of northwestern African carnivores is very patchy. The richest assemblage is that of the Late Pliocene of Ahl al Oughlam, with more than 20 species belonging to the main modern families. Some additions to its study are made here. The rather poor Early Pleistocene faunas are mainly marked by the arrival of a large Canis. A fauna of modern type, with example, the duo Hyaena–Crocuta, settles in the Earliest Pleistocene site of Tighenif, where some older elements linger on (Homotherium), beside some taxa of doubtful affinities, like a large Panthera, and a strange canid close to Nyctereutes, dominant at this site as well as at the slightly younger ones of Thomas and Oulad Hamida Quarries in Casablanca. All these faunas consist mostly of African taxa, together with a Palaearctic component whose importance increases towards the end of the Pleistocene.     

Climate-based models of spatial patterns of species richness in Egypt's butterfly and mammal fauna

Aim  Identifying areas of high species richness is an important goal of conservation biogeography. In this study we compared alternative methods for generating climate-based estimates of spatial patterns of butterfly and mammal species richness.
Location  Egypt.
Methods  Data on the occurrence of butterflies and mammals in Egypt were taken from an electronic database compiled from museum records and the literature. Using M axent , species distribution models were built with these data and with variables describing climate and habitat. Species richness predictions were made by summing distribution models for individual species and by modelling observed species richness directly using the same environmental variables.
Results  Estimates of species richness from both methods correlated positively with each other and with observed species richness. Protected areas had higher species richness (both predicted and actual) than unprotected areas.
Main conclusions  Our results suggest that climate-based models of species richness could provide a rapid method for selecting potential areas for protection and thus have important implications for biodiversity conservation.     

Amniotes through major biological crises: faunal turnover among Parareptiles and the end‐Permian mass extinction

Abstract: The Parareptilia are a small but ecologically and morphologically diverse clade of Permian and Triassic crown amniotes generally considered to be phylogenetically more proximal to eureptiles (diapsids and their kin) than to synapsids (mammals and their kin). A recent supertree provides impetus for an analysis of parareptile diversity through time and for examining the influence of the end‐Permian mass extinction on the clade’s origination and extinction rates. Phylogeny‐corrected measures of diversity have a significant impact on both rates and the distribution of origination and extinction intensities. Time calibration generally results in a closer correspondence between origination and extinction rate values than in the case of no time correction. Near the end‐Permian event, extinction levels are not significantly higher than origination levels, particularly when time calibration is introduced. Finally, regardless of time calibration and/or phylogenetic correction, the distribution of rates does not differ significantly from unimodal. The curves of rate values are discussed in the light of the numbers and distributions of both range extensions and ghost lineages. The disjoint time distributions of major parareptile clades (e.g. procolophonoids and nycteroleterids‐pareiasaurs) are mostly responsible for the occurrence of long‐range extensions throughout the Permian. Available data are not consistent with a model of sudden decline at the end‐Permian but rather suggest a rapid alternation of originations and extinctions in a number of parareptile groups, both before and after the Permian/Triassic boundary.     

Regional patterns of diversity and estimates of global insect species richness

The total number of insect species in the world is an important if elusive figure. We use a fresh approach to estimate global insect species richness, based on biogeographic patterns of diversity of well or better documented taxa. Estimates generated by various calculations, all variations on a theme, largely serve to substantiate suggestions that insect species are likely to number around 10 million or less.     

Weak links: 'Rapoport's rule' and large-scale species richness patterns

Many hypotheses have been proposed to explain regional species richness patterns. Among these, ‘Rapoport's rule’ has sparked considerable controversy by stating that the latitudinal gradient in species richness can be explained indirectly as a function of narrower geographic ranges for species at low latitudes. Annual climatic variability, or deviation from mean climatic conditions, has been hypothesized to moderate this phenomenon. Furthermore, taxa that avoid much of this seasonality, such as temperate zone insects that enter diapause or species that migrate, were predicted to show reduced latitudinal gradients in richness. I test the suggested link between ‘Rapoport's rule’ and species richness for two higher level insect taxa as well as for the class Mammalia. Although these taxa exhibit the well-known latitudinal gradient in species richness, simple annual climatic variability and deviation from mean annual climatic conditions provide very poor predictions of species richness in each of them. Potential evapotranspiration, a measurement of ambient climatic energy, explains most of the observed variance in regional species richness patterns for all three taxa, consistent with the species richness-energy hypothesis. I find no support for an indirect link between ‘Rapoport's rule’ and terrestrial species richness patterns in North America.     

Spider family composition and species richness patterns in two savannah habitats along the eastern coastal plain of Africa

The spider faunas of two savannah reserves along the eastern coastal plain of Africa are compared. Species richness was higher in the tropical area, with 493 species (54 families) from Mkomazi Game Reserve, Tanzania. Species richness was also high in the subtropics, with a total of 431 species (46 families) recorded from Ndumo Game Reserve, South Africa. Spider community structure was remarkably similar in the two reserves, with Salticidae, Gnaphosidae, Thomisidae, Theridiidae and Araneidae the most species‐rich families in both reserves. Eleven of the fourteen most species rich families were the same. A similar proportion of families were represented by singleton and doubleton species. A genus‐ and species‐level comparison of ten spider families indicates that while there is considerable overlap in the generic composition of the reserves (Sorensen’s Quotient of similarity: all >0.650 except Linyphiidae, 0.166; Corinnidae, 0.500) there is little overlap between the species occurring in the two sites (0.000–0.571), which was particularly evident in the more species‐rich families. A comparison of diversity of 57 families in each reserve with the spider biodiversity in the two sub‐regions suggests that local biodiversity is largely determined by regional biogeographical influences rather than local ecological factors.     

Predicting patterns of plant species richness in megadiverse South Africa

Using new tools (boosted regression trees) in predictive biogeography, with extensive spatial 23 distribution data for >19 000 species, we developed predictive models for South African plant species richness patterns. Further, biome level analysis explored possible functional determinants of country‐wide regional species richness. Finally, to test model reliability independently, we predicted potential alien invasive plant species richness with an independent dataset. Amongst the different hypotheses generally invoked to explain species 30 diversity (energy, favorableness, topographic heterogeneity, irregularity and seasonality), results revealed topographic heterogeneity as the most powerful single explanatory variable for indigenous South African plant species richness. Some biome‐specific responses were observed, i.e. two of the five analyzed biomes (Fynbos and Grassland) had richness best explained by the “species‐favorableness” hypothesis, but even in this case, topographic heterogeneity was also a primary predictor. This analysis, the largest conducted on an almost exhaustive species sample in a species‐rich region, demonstrates the preeminence of topographic heterogeneity in shaping the spatial pattern of regional plant species richness. Model reliability was confirmed by the considerable predictive power for alien invasive species richness. It thus appears that topographic heterogeneity controls species richness in two main ways: firstly, by providing an abundance of ecological niches in contemporary space (revealed by alien invasive species richness relationships) and secondly, by facilitating the persistence of ecological niches through time. The extraordinary richness of the South African Fynbos biome, a world‐renowned hotspot of biodiversity with the steepest environmental gradients in South Africa, may thus have arisen through both mechanisms. Comparisons with similar regions of the world outside South Africa are needed to confirm the generality of topographic heterogeneity and favorableness as predictors of plant richness.     

Carnivora from the Plio-Pleistocene hominin site of Drimolen, Gauteng, South Africa

Drimolen is one of the newest and most productive hominin sites in South Africa, and is dated on faunal grounds between 2.0 Ma to 1.5 Ma. This paper provides the first overview of the Carnivora from Drimolen, updating the previously published preliminary faunal list, and describing all currently prepared craniodental and postcranial material. The Drimolen specimens are described in comparison with other modern and fossil South African carnivore material. The carnivores cover a range of taxa including hyaenids, felids, canids and herpestids. Most notable amongst these are the sabretooth Dinofelis aff. piveteaui craniodental and postcranial remains, which are described in detail, and a Chasmaporthetes nitidula cranium. The genus Chasmaporthetes is found at three other sites in the area - Sterkfontein, Swartkrans and Coopers D. There are two models for the geographic origin of Dinofelis piveteaui, in that it may have arisen in either eastern or southern Africa. These possibilities are discussed in the light of the new South African Dinofelis material, as the Drimolen material appears to represent a more primitive form with affinities with D. piveteaui. Fossil leopard material from Kromdraai B and Drimolen is also discussed, as the metapodia assigned to P. pardus from these two sites are very small, but lie within the variation of modern leopards. Such size differences in fossil postcrania may have implications for the niches that these animals may have occupied in the past.     

欧亚大陆东部毛茛科植物多样性格局及主导因子

毛茛科是真双子叶植物的基部类群之一, 包含多种药用植物, 具有较高的保护价值, 但关于毛茛科物种多样性和谱系多样性大尺度格局及其影响因子的研究还比较匮乏, 特别是以较高分辨率分布数据为基础的物种多样性格局研究尚未见报道。本文旨在: (1)建立欧亚大陆东部毛茛科植物分布数据库, 估算不同生活型物种多样性和谱系多样性格局, 并探究格局的形成机制。(2)分析毛茛科物种多样性和谱系多样性的相关关系, 确定多样性热点地区, 为毛茛科保护规划提供依据。根据中国、哈萨克斯坦、吉尔吉斯斯坦、塔吉克斯坦、土库曼斯坦、乌兹别克斯坦、蒙古和俄罗斯等国家的区域和地方植物志, 建立了“欧亚大陆东部地区毛茛科物种分布数据库”。该数据库包含了欧亚大陆东部地区1,688种毛茛科物种的分布数据, 空间分辨率为100 km × 100 km。在此基础上, 估算了毛茛科全部及不同生活型的物种多样性和谱系多样性格局, 并利用广义线性模型和等级方差分离方法分析了毛茛科物种和谱系多样性格局与环境因子的关系。最后比较了物种多样性和谱系多样性的相关关系, 确定了毛茛科的古热点地区。结果显示: (1)欧亚大陆东部毛茛科植物物种和谱系多样性均呈明显的纬度格局, 且在山区具有较高的多样性。(2)毛茛科植物物种和谱系多样性受现代气候、地形异质性和末次冰期以来的气候变化的共同影响, 但不同影响因子的相对贡献率在物种和谱系多样性及不同生活型之间差异显著。(3)中高纬度地区的谱系多样性高于给定物种数的预期, 是毛茛科的古热点地区, 在毛茛科保护规划中应受到重视。     

Mammals of Australian islands: factors influencing species richness

Distribution patterns of indigenous non-volant terrestrial mammals on 257 Australian islands were examined in relation to environmental parameters and the effects of human-induced disturbance during prehistoric and historic times on island species numbers. Species occurrence for individual species, for taxonomic and trophic groups, and for all species together was related to environmental parameters using regression analysis and the extreme-value function model. Patterns of occurrence were examined separately within three major biogeographic regions derived by pattern analysis. The number of species known to have occurred on these islands during historic times was adequately predicted from area alone. No statistically significant improvement in predicted species number was gained by including island elevation, mean annual rainfall, isolation from the mainland or the number of potentially competing species present on the island. Similarly, no single factor other than area was found to influence consistently the presence of individual species. We conclude that the occurrence of indigenous non-volant terrestrial mammal species on these islands indicates a relictual rather than equilibrial fauna. Visitation by Aboriginal people during prehistoric times did not significantly increase mammal extinctions on islands. Examination of patterns of species richness for a given area on a regional basis showed that islands in and around Bass Strait and Tasmania (Bass Region) were the most species-rich, islands off the northern coasts were slightly less rich, and islands off the south western coasts had fewest species. This is in contrast to the usual latitudinal gradient in species richness patterns. However, islands off the northern and eastern coasts had an overall greater number of different species. When considered in relation to the number of different species of mammals occurring within each region, islands of a given size in Bass Region typically bore a higher proportion of this species pool than other regions. The Bass Region was found to be particularly rich in macropoid herbivores and dasyurid carnivores and insectivores. Analyses indicated that there is a very strong relationship between the presence of exotics as a whole and the local extinction of native mammals. Many mammal species formerly widespread on the Australian mainland are now restricted totally to islands (nine species) or are threatened with extinction on the mainland and have island populations of conservation significance (ten species). In all, thirty-five islands protect eighteen taxa of Australian threatened mammals. The land-use and management of these islands is of considerable importance to nature conservation. The introduction of exotic mammals to these islands should be prevented; any introductions that occur should be eradicated immediately.     

Effect of sampling grain on patterns of species richness and turnover in Amazonian forests

Grain (size of sampling units) affects the spatial resolution at which ecological patterns can be observed and analysed, and potentially has an important effect on the results of broad‐scale studies on diversity gradients. Here we examine the effect of grain on patterns of species richness and turnover in lowland rainforests of western Amazonia (Peru and Colombia). We inventoried pteridophytes (ferns and lycophytes), melastomes (Melastomataceae) and palms (Arecaceae) in four line transects of 22–29 km length. Different grains were obtained by aggregating original 100‐m‐long sampling units into larger segments up to 19.2 km long. With any given grain and plant group, local species richness varied considerably both within and among transects, and a transect segment that was species‐rich with one grain could be relatively species‐poor with another. Which transect had the highest vs lowest mean species richness per sampling unit (α richness) differed among plant groups. It also varied to some degree with grain, as transects differed in how rapidly local species richness increased with increasing grain. Patterns of species turnover were more consistently correlated among plant groups than patterns of species richness were, and NMDS ordinations were rather similar with all grains and plant groups. Floristic heterogeneity within the Amazonian terra firme rainforest seems to contain a general compositional pattern that is sufficiently robust to be detectable with various sampling schemes, but patterns of species richness appear more case‐specific. Therefore, using one plant group as an indicator for patterns in other plant groups can be expected to work better for species turnover than for species richness.     

Effects of historical and contemporary factors on global patterns in avian species richness

Aim  The aim of this study was to determine how regional and historical factors influence global patterns in avian species richness.
Location  Global.
Methods  Using a comprehensive data set including 710 World Wildlife Fund terrestrial ecoregions covering nearly all the land surface of the Earth, avian species richness was compared among six biogeographical regions after accounting for sample area, elevational range and climate. Analysis of variance and multiple regressions were used. Spatial autocorrelation in model residuals was accounted for.
Results  Significant effects of region on avian species richness were found in nearly all comparisons between biogeographical regions.
Main conclusions  Regional and historical processes have played a role in regulating large-scale avian species richness patterns across the globe. Avian species richness in different regions of the world cannot be accurately predicted by a single global model. Avian species richness in areas of similar environments may differ substantially between regions, and thus avian species richness in one biogeographical region cannot be predicted using the richness–environment relationship derived from the data of another biogeographical region, even one with similar environments.     

The challenge of accurately documenting bee species richness in agroecosystems: bee diversity in eastern apple orchards

Bees are important pollinators of agricultural crops, and bee diversity has been shown to be closely associated with pollination, a valuable ecosystem service. Higher functional diversity and species richness of bees have been shown to lead to higher crop yield. Bees simultaneously represent a mega‐diverse taxon that is extremely challenging to sample thoroughly and an important group to understand because of pollination services. We sampled bees visiting apple blossoms in 28 orchards over 6 years. We used species rarefaction analyses to test for the completeness of sampling and the relationship between species richness and sampling effort, orchard size, and percent agriculture in the surrounding landscape. We performed more than 190 h of sampling, collecting 11,219 specimens representing 104 species. Despite the sampling intensity, we captured <75% of expected species richness at more than half of the sites. For most of these, the variation in bee community composition between years was greater than among sites. Species richness was influenced by percent agriculture, orchard size, and sampling effort, but we found no factors explaining the difference between observed and expected species richness. Competition between honeybees and wild bees did not appear to be a factor, as we found no correlation between honeybee and wild bee abundance. Our study shows that the pollinator fauna of agroecosystems can be diverse and challenging to thoroughly sample. We demonstrate that there is high temporal variation in community composition and that sites vary widely in the sampling effort required to fully describe their diversity. In order to maximize pollination services provided by wild bee species, we must first accurately estimate species richness. For researchers interested in providing this estimate, we recommend multiyear studies and rarefaction analyses to quantify the gap between observed and expected species richness.     

Spatial patterns of invertebrate species richness in a river: the relationship between riffles and microhabitats

This study describes the pattern of invertebrate species richness in a river reach with large differences in habitat complexity at two, hierarchically nested, spatial scales. The aim was to determine whether the mass effect was likely to be increasing invertebrate species richness in epilithic microhabitats in this river. The mass effect is the process by which the species richness of a patch is increased when it acts as a ‘sink’ for species generated by ‘source’ patches. Microhabitat patch types in Mountain River, Tasmania, were distinguished on the basis of physical structure and orientation on the river bed. They were nested within two types of riffle with contrasting structural complexity: bedrock and boulder-cobble riffles. It was hypothesized that microhabitats with high species richness would act as source patches, contributing species to other microhabitats (sinks) and thereby increasing their species richness. Microhabitat sampling was carried out in four consecutive seasons and rarefaction was used to estimate riffle-scale species richness. Analysis of variance ( ANOVA ) was used to compare the identical microhabitats present in the contrasting riffle types, to detect evidence of the mass effect in either riffle type. The more structurally complex boulder-cobble riffles had higher species richness than did bedrock riffles. Amongst the microhabitats, the spaces beneath the cobbles had the most species. Microhabitats accounted for a higher percentage of the variation in species richness than did differences between riffles of the same type. No evidence was found for the operation of the mass effect in either riffle type. The majority of species found only in boulder-cobble riffles were unique to the beneath-cobble microhabitat and appeared to be unable to colonize other microhabitats, even as transients. In Mountain River, small-scale habitat characteristics appeared to be more important than larger-scale effects in determining microhabitat species richness.     

Plio-Pleistocene climatic change in the Turkana Basin (East Africa): evidence from large mammal faunas

We investigated palaeoclimatic change in the Turkana Basin during the Pliocene climatic shift toward increased aridity in Africa. We analyzed the palaeoecology of this area using mammal faunas as environmental indicators. Twenty Plio-Pleistocene fossil assemblages and a comparative dataset of 16 modern localities covering a wide range of climatic and ecological conditions across Africa were analyzed. We constructed community profiles using taxonomic variables which reflect ecological information. Principal component analysis and bivariate correlation were used to study changes in the community structure of these mammalian faunas and to draw palaeoenvironmental inferences. Subsequently, least-squares regressions yielded climatic estimates (annual rainfall and drought length) for the studied period. An additional set of 8 modern faunas was used to validate these regression models. The climatic estimates showed a drying trend throughout the sequence. The biomes in the Turkana Basin changed from semi-evergreen rain forest to deciduous woodland and savanna during the middle-late Pliocene. This was the most important climatic shift detected in our study. Evidence suggests a continuous presence of savannas from 2.5 million years ago onwards. This pattern of climatic change is consistent with isotopic evidence on global climate, and with independently derived regional palaeoenvironmental evidence (i.e., micromammals, palaeovegetation, soil carbonates and palaeosols).