Global concordance in diversity patterns of vascular plants and terrestrial vertebrates

The factors that determine large-scale patterns of species richness are poorly understood. In particular, biologists have not determined the relative roles of taxon-specific characteristics that influence diversification and distribution, and region-specific features that promote and constrain diversity. We show that the numbers of species of vascular plants and of four terrestrial vertebrate taxa (mammals, birds, reptiles and amphibians) vary in parallel across 296 geographic areas covering most of the globe, even after accounting for sample area, climate, topographic heterogeneity and differences between continents. Thus, a common set of regional characteristics and processes appears to shape patterns of species richness in a diverse set of taxa, despite substantial differences in their biological traits.     

A global model of island biogeography

Aim The goal of our study was to build a global model of island biogeography explaining bird species richness that combines MacArthur and Wilson's area–isolation theory with the species–energy theory. Location Global. Methods We assembled a global data set of 346 marine islands representing all types of climate, topography and degree of isolation on our planet, ranging in size from 10 ha to 800,000 km². We built a multiple regression model with the number of non‐marine breeding bird species as the dependent variable. Results We found that about 85–90% of the global variance in insular bird species richness can be explained by simple, contemporary abiotic factors. On a global scale, the three major predictors — area, average annual temperature and the distance separating the islands from the nearest continent — all have constraining (i.e. triangular rather than linear) relationships with insular bird species richness. We found that the slope of the species–area curve depends on both average annual temperature and total annual precipitation, but not on isolation. Insular isolation depends not only on the distance of an island from the continent, but also on the presence or absence of other neighbouring islands. Range in elevation — a surrogate for diversity of habitats — showed a positive correlation with bird diversity in warmer regions of the world, while its effect was negative in colder regions. We also propose a global statistical model to quantify the isolation‐reducing effect of neighbouring islands. Main conclusions The variation in avian richness among islands worldwide can be statistically explained by contemporary environmental variables. The equilibrium theory of island biogeography of MacArthur and Wilson and the species–energy theory are both only partly correct. Global variation in richness depends about equally upon area, climate (temperature and precipitation) and isolation. The slope of the species richness–area curve depends upon climate, but not on isolation, in contrast to MacArthur and Wilson's theory.     

Dragging into the open: the polythetic nature of areas of endemism

Areas of endemism represent territories (no matter the size) of non-random overlap in the geographic distribution of two or more taxa, reflecting a common spatial history of these taxa. The common spatial history is a result of different processes that connect areas of endemism to evolutionary theory. Numerous and diverse definitions of areas of endemism have been proposed. All of them have used as the conceptual foundation of the definition a certain degree of non-random congruence of geographic distribution amongst at least two taxa. ‘Certain degree’ means that geographic congruence does not demand complete agreement on the boundaries of those taxa's distributions at all possible scales of mapping. The words ‘certain degree’ mask the polythetic nature of areas of endemism. The polythetic characterization of areas of endemism implies that each locality of the study area has a large number of a set of species. Each species of this set is present in many of those localities and, generally, none of those species is present in every locality of the area. The converse will be a monothetic nature of areas of endemism where a taxon or group of taxa is present in all the localities of the study area. We propose here that the expansion of the definition of areas of endemism, including their polythetic characterization, will improve understanding of large biogeographic areas such as realms, regions, provinces, and districts, and will increase the scientific content (e.g., predictive capability and explanatory power) of areas of endemism.     

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.     

中国新石器时代以来淡水及河口鱼类考古遗存的地理分布及其生物地理学意义

考古遗址中出土的鱼类遗存是探讨现生种类在历史时期的地理分布的重要资料。本文系统整理了中国新石器时代至明代考古遗址中出土的淡水及河口鱼类考古遗存记录, 对比了鉴定至物种的遗存记录分布与现状分布, 探讨了个别物种古今分布变迁的可能成因。结果显示: (1)目前中国淡水及河口鱼类考古遗存共鉴定记录了72个类群, 分属于8目12科, 其中以鲤形目的类群数量最多(43); 鉴定至物种的共42种, 其中以鲤(Cyprinus carpio)和青鱼(Mylopharyngodon piceus)的出土遗址(群)数量最多(各46个)。(2)有淡水及河口鱼类遗存出土记录的遗址中, 属新石器时代的遗址(群)数量最多(68), 从这些遗址(群)中出土鉴定的类群数(60)也在各时期中居于首位。(3)淡水及河口鱼类遗存鉴定记录的类群最多的流域是长江流域(55个), 其次为淮河流域(24个)和黑龙江流域(22个); 而南海流域、西南流域和台湾岛流域各仅有1个类群。(4)有8个物种在其现存自然分布范围以外的流域至少有1处遗存鉴定记录: 团头鲂(Megalobrama amblycephala)、须鲫(Carassioides acuminatus)、龙州鲤(Cyprinus longzhouensis)、鳙(Aristichthys nobilis)、草鱼(Ctenopharyngodon idella)、青鱼、黄鳝(Monopterus albus)和日本花鲈(Lateolabrax japonicas); 除草鱼和青鱼之外, 其余6种在其各自现存分布区以北的流域至少有1处遗存记录。研究结果表明, 中国新石器时代以来的淡水及河口鱼类考古遗存记录所展现的区系地理格局整体上与现今格局一致。个别物种在历史时期的分布较现今分布区范围更广, 这可能是因为遗存出土地区的古气候普遍较现今温暖, 亦或是因其后气候变化或水系变迁使部分鱼类的分布区变狭窄。     

Effects of seasonality on the species–area relationship: a case study with birds in urban parks

Aim To examine how parameters of the species–area curve and factors determining bird species richness are affected by seasonality. Location One hundred and thirty urban parks of the city of Valencia (Spain) ranging between 0.03 and 18.6 ha. Methods Bird censuses were conducted monthly during 1998 and 2004. For each park, 27 variables were recorded as measures of size, structure and isolation. Linear regression was used to test for patterns in species richness relative to independent variables. The results of each season were compared. Results Curves corresponding to the breeding period (spring–summer) had significantly higher intercepts, but slopes did not change across seasons. Turnover rates of resident species were dependent on patch size and isolation considering spring, but not autumn, from different years. Additionally, turnover rates in spring were lower in parks in close proximity to others than in isolated ones. In all seasons, the number of bird species showed a strong relationship with park area, which explained c. 60% of the variation in species numbers. Habitat variables and park isolation explained a small amount of the variation in species numbers. The data did not give support to the random placement hypothesis. Main conclusions The overall conclusions of this study give little support to the possible influence of seasonality on species–area relationship or on the three main hypotheses explaining it. This lack of influence of seasonality could be explained by the seasonal stability of the bird populations of the parks within the study area as a consequence of different factors, mainly the characteristics of the species pool, similarity in the features of the parks irrespective of their size, and stability of resources and conditions across seasons. The question of whether this lack of influence of seasonality on the species–area relationship occurs in those ecological systems that have a larger seasonal variation than the urban parks of the study area remains unresolved. Closer examination of the seasonal patterns reported in this study is likely to be useful in increasing our understanding of the species–area relationship.     

The other face of Lyell: historical biogeography in his Principles of geology

Although some excellent articles about Lyell's work have been published, they do not explicitly deal with Lyell's biogeographical conceptions. The purpose of this paper is to analyse Lyell's biogeographical model in terms of its own internal structure. Lyell tried to explain the distribution of organisms by appealing to a real cause (climate). However, he was aware that environmental conditions were clearly insufficient to explain the existence of biogeographical regions. Lyell's adherence to ecological determinism generated strong tensions within his biogeographical model. He shifted from granting a secondary weight to dispersal to assigning it a major role. By doing so, Lyell was led into an evident contradiction. A permanent tension in Lyell's ideas was generated by the prevalent explanatory pattern of his time. The explanatory model based on laws did not produce satisfactory results in biology because it did not deal with historical processes. We may conclude that the knowledge of organic distribution interested Lyell as long as it could be explained by the uniformitarian principles of his geological system. The importance of the second volume of the Principles of geology lies in its ample and systematic argumentation about the geographical distribution of organisms. Lyell established, independently from any theory about organic change, the first version of dispersalist biogeography.     

The Arctic Oscillation predicts effects of climate change in two trophic levels in a high-arctic ecosystem

During recent decades there has been a change in the circulation of atmospheric pressure throughout the Northern Hemisphere. These variations are expressed in the recently described Arctic Oscillation (AO), which has shown an upward trend (associated with winter warming in the eastern Arctic) during the last three decades. We analysed a 12‐year time series on growth of Cassiope tetragona (Lapland Cassiope) and a 21‐year time series on abundance of a Svalbard reindeer population. High values of the AO index were associated with reduced plant growth and reindeer population growth rate. The North Atlantic Oscillation index was not able to explain a significant proportion of the variance in either plant growth or reindeer population fluctuations. Thus, the AO index may be a better predictor for ecosystem effects of climate change in certain high‐arctic areas compared to the NAO index.     

The quest for a null model for macroecological patterns: geometry of species distributions at multiple spatial scales

There have been several attempts to build a unified framework for macroecological patterns. However, these have mostly been based either on questionable assumptions or have had to be parameterized to obtain realistic predictions. Here, we propose a new model explicitly considering patterns of aggregated species distributions on multiple spatial scales, the property which lies behind all spatial macroecological patterns, using the idea we term 'generalized fractals'. Species' spatial distributions were modelled by a random hierarchical process in which the original 'habitat' patches were randomly replaced by sets of smaller patches nested within them, and the statistical properties of modelled species assemblages were compared with macroecological patterns in observed bird data. Without parameterization based on observed patterns, this simple model predicts realistic patterns of species abundance, distribution and diversity, including fractal-like spatial distributions, the frequency distribution of species occupancies/abundances and the species–area relationship. Although observed macroecological patterns may differ in some quantitative properties, our concept of random hierarchical aggregation can be considered as an appropriate null model of fundamental macroecological patterns which can potentially be modified to accommodate ecologically important variables.     

The distribution and biology of nomadic birds in the Karoo, South Africa

Dryland nomadic bird species, as a proportion of all bird species in a biome in southern Africa, are highest in the arid grassland and arid and semi-arid Karoo in South Africa. Nomadic birds, of which the most widespread species is the greybacked finchlark Eremopterix verticalis (Smith), are most frequently observed in the north-central and north western Nama Karoo. The species richness of nomadic species is inversely correlated with species richness of all bird species in the Karoo. Since the distribution of nomadic birds is in areas where rainfall is patchy, low (<250 mm per year) and aseasonal, this supports the idea that fewer species are able to cope with resources that are patchy in time and space, and that there has been selection for nomadism in the species that are able to use patchy environments. Species richness and abundance of nomadic birds is negatively correlated with rainfall amount but positively correlated with the coefficient of variation of the rainfall and with rainfall in autumn. The frequency of nomadic birds is inversely correlated with altitude range; nomadic species are most often recorded in structurally simple habitats (shrubland and grassland) on open plains. Most nomadic bird species in the Karoo are granivorous. Perennial desert grasses are important components of the habitat and diet of small nomadic granivores, and also provide nest sites and nest material. Nomadic birds can breed throughout the year, without a clearly defined ‘season’ in both the Succulent and Nama Karoo. Average clutch sizes do not differ significantly between resident and all nomadic species in the arid and semi-arid Karoo. Nomadism is an evolutionary stable strategy for individual species only when extremes in environmental conditions are frequent enough, and unpredictable enough, to maintain movements to high resource patches or to maintain dispersal away from low resource patches. If high rainfall years are too regular or infrequent, or peaks in fluctuations of resources in the environment too low, or rainfall patches are randomly distributed, nomadism would not be maintained as part of the individual behaviour pattern.     

The global distribution of ecosystems in a world without fire

This paper is the first global study of the extent to which fire determines global vegetation patterns by preventing ecosystems from achieving the potential height, biomass and dominant functional types expected under the ambient climate (climate potential). To determine climate potential, we simulated vegetation without fire using a dynamic global-vegetation model. Model results were tested against fire exclusion studies from different parts of the world. Simulated dominant growth forms and tree cover were compared with satellite-derived land- and tree-cover maps. Simulations were generally consistent with results of fire exclusion studies in southern Africa and elsewhere. Comparison of global 'fire off' simulations with landcover and treecover maps show that vast areas of humid C(4) grasslands and savannas, especially in South America and Africa, have the climate potential to form forests. These are the most frequently burnt ecosystems in the world. Without fire, closed forests would double from 27% to 56% of vegetated grid cells, mostly at the expense of C(4) plants but also of C(3) shrubs and grasses in cooler climates. C(4) grasses began spreading 6-8 Ma, long before human influence on fire regimes. Our results suggest that fire was a major factor in their spread into forested regions, splitting biotas into fire tolerant and intolerant taxa.     

Apes in a changing world – the effects of global warming on the behaviour and distribution of African apes

Aim In this study we use a modelling approach to identify: (1) the factors responsible for the differences in ape biogeography, (2) the effects that global warming might have on distribution patterns of African apes, (3) the underlying mechanisms for these effects, and (4) the implications that behavioural flexibility might be expected to have for ape survival. All African apes are highly endangered, and the need for efficient conservation methods is a top priority. The expected changes in world climate are likely to further exacerbate the difficulties they face. Our study aims to further understand the mechanisms that link climatic conditions to the behaviour and biogeography of ape species. Location Africa. Method We use an existing validated time budgets model, derived from data on 20 natural populations of gorillas (Gorilla beringei and Gorilla gorilla) and chimpanzees (Pan troglodytes and Pan paniscus), which specifies the relationship between climate, group size, body weight and time available for various activities, to predict ape distribution across Africa under a uniform worst‐case climate change scenario. Results We demonstrate that a worst‐case global warming scenario is likely to alter the delicate balance between different time budget components. Our model points to the importance of annual temperature variation, which was found to have the strongest impact on ape biogeography. Our simulation indicates that rising temperatures and changes in rainfall patterns are likely to have strong effects on ape survival and distribution, particularly for gorillas. Even if they behaved with maximum flexibility, gorillas may not be able to survive in most of their present habitats if the climate was to undergo extreme changes. The survival of chimpanzees was found to be strongly dependent on the minimum viable group size required. Main conclusions Our model allows us to explore how climatic conditions, individual behaviour and morphological traits may interact to limit the biogeographical distributions of these species, thereby allowing us to predict the effects of climate change on African ape distributions under different climate change regimes. The model suggests that climate variability (i.e. seasonality) plays a more important role than the absolute magnitude of the change, but these data are not normally provided by climate models.     

The influence of the light environment and photosynthesis on oxidative signalling responses in plant–biotrophic pathogen interactions

Plants grow in a constantly fluctuating environment, which has driven the evolution of a highly flexible metabolism and development necessary for their sessile lifestyle. In contrast to the situation in the natural world, the detailed dissection of the regulatory networks that govern plants' responses to abiotic insults and their interaction with pathogens have been studied almost exclusively in controlled environments where a single challenge has been applied. However, the question arises of how such pathways operate when the plant is subjected to multiple stresses, especially where the expression of overlapping gene sets and common signalling molecules, such as reactive oxygen species (ROS), are implicated. This review will focus on the responsiveness of leaves to their light environment and how this might influence both basal and induced resistance to infection by biotrophic pathogens. While several signalling pathways operate in a complex network of defence responses, the functioning of the salicylic acid (SA) signalling pathway will receive specific consideration. This is because information is becoming available of its role in abiotic stress responses and it dependency on light. This article covers several topics, some of which formerly have received scant attention. These include the effects of infection on photosynthetic performance and carbohydrate metabolism, the parallels between the induction of acclimation to high light and immunity to pathogens, the role of light in the functioning of the SA signalling pathway and the light sensitivity of lesion formation and the use of lesion mimic mutants and transgenic plants. Finally, a model is proposed that attempts to extrapolate these controlled environment-based studies to the functioning of defences against pathogens in a field-grown crop.     

The data void in modeling current and future distributions of tropical species

Conserving biodiversity in the face of climate change requires a predictive ecology of species distributions. Nowhere is this need more acute than in the tropics, which harbor the majority of Earth's species and face rapid and large climate and land‐use changes. However, the study of species distributions and their responses to climate change in high diversity tropical regions is potentially crippled by a lack of basic data. We analyzed a database representing more than 800 000 unique geo‐referenced natural history collections to determine what fraction of tropical plant species has sufficient numbers of available collections for use in the habitat or niche models commonly used to predict species responses to climate change. We found that more than nine out of 10 species from the three principle tropical realms are so poorly collected (n < 20 records) that they are essentially invisible to modern modeling and conservation tools. In order to predict the impact of climate change on tropical species, efforts must be made to increase the amount of data available from tropical countries through a combination of collecting new specimens and digitizing existing records.     

The ecology of saprophagous macroarthropods (millipedes,woodlice) in the context of global change

Millipedes (Diplopoda) and woodlice (Crustacea, Isopoda), with a total of about 15000 described species worldwide, contribute substantially to invertebrate biodiversity. These saprophagous macroarthropods, which are key regulators of plant litter decomposition, play an important role in the functioning of terrestrial ecosystems in tropical and temperate areas. Herein we review current knowledge on the effects of climate, food quality and land cover on millipede and woodlouse species to explore their potential responses to global change. Essentially similar trends are observed in the two taxa. Experiments have shown that climate warming could result in higher rates of population growth and have positive effects on the abundance of some temperate species. This is consistent with signs of northward expansion in Europe, although the mechanisms of dispersal remain unclear. The generality of this finding is evaluated in relation to the life histories and geographical distributions of species. At low latitudes, interactions with more severe droughts are likely and could affect community composition. Elevated atmospheric CO₂ levels and changes in plant community composition are expected to alter leaf litter quality, a major determinant of macroarthropod fertility via the link with female adult body size. Although food quality changes have been shown to influence population growth rates significantly, it is proposed that the effects of warming will be probably more important during the coming decades. Land cover changes, mainly due to deforestation in the tropics and land abandonment in Europe, are critical to habitat specialists and could override any other effect of global change. Habitat destruction by man may be the main threat to macroarthropod species, many of which are narrow endemics. At the landscape scale, habitat heterogeneity could be a good option for conservation, even at the cost of some fragmentation. Two principal areas are identified which require further work: (i) the effects of climate change across broader geographic ranges, and on species with different ecologies and life histories; (ii) the effects of global change on both macroarthropods and their natural enemies (predators, parasites and pathogens), to improve predictions in field situations.     

The relative role of relatives in conspecific brood parasitism

Conspecific brood parasites lay their eggs in the nests of other females in the same population, leading to a fascinating array of possible ‘games’ among parasites and their hosts ( Davies 2000 ; Lyon & Eadie 2008 ). Almost 30 years ago, Andersson & Eriksson (1982) first suggested that perhaps this form of parasitism was not what it seemed—indeed, perhaps it was not parasitism at all! Andersson & Eriksson (1982) observed that conspecific brood parasitism (CBP) was disproportionally common in waterfowl (Anatidae), a group of birds for which natal philopatry is female‐biased rather than the more usual avian pattern of male‐biased natal philopatry. Accordingly, Andersson (1984) reasoned (and demonstrated in an elegantly simple model) that relatedness among females might facilitate the evolution of CBP—prodding us to reconsider it as a kin‐selected and possibly cooperative breeding system rather than a parasitic interaction. The idea was much cited but rarely tested empirically until recently—a number of new studies, empowered with a battery of molecular techniques, have now put Andersson’s hypothesis to the test ( Table 1 ). The results are tantalizing, but also somewhat conflicting. Several studies, focusing on waterfowl, have found clear evidence that hosts and parasites are often related ( Andersson & Åhlund 2000 ; Roy Nielsen et al. 2006 ; Andersson & Waldeck 2007 ; Waldeck et al. 2008 ; Jaatinen et al. 2009 ; Tiedemann et al. 2011 ). However, this is not always the case ( Semel & Sherman 2001 ; Anderholm et al. 2009 ; and see Pöysa 2004 ). In a new study reported in this issue of Molecular Ecology, Jaatinen et al. (2011a) provide yet another twist to this story that might explain not only why such variable results have been obtained, but also suggests that the games between parasites and their hosts—and the role of kinship in these games—may be even more complex than Andersson (1984) imagined. Indeed, the role of kinship in CBP may be very much one of relative degree!

Table 1. A summary of recent studies that have tested for evidence of relatedness between hosts and parasites in avian conspecific brood parasites