The role of climate,water and biotic interactions in shaping biodiversity patterns in arid environments across spatial scales

Aim

Desert ecosystems, with their harsh environmental conditions, hold the key to understanding the responses of biodiversity to climate change. As desert community structure is influenced by processes acting at different spatial scales, studies combining multiple scales are essential for understanding the conservation requirements of desert biota. We investigated the role of environmental variables and biotic interactions in shaping broad and fine‐scale patterns of diversity and distribution of bats in arid environments to understand how the expansion of nondesert species can affect the long‐term conservation of desert biodiversity.

Location

Levant, Eastern Mediterranean.

Methods

We combine species distribution modelling and niche overlap statistics with a statistical model selection approach to integrate interspecific interactions into broadscale distribution models and fine‐scale analysis of ecological requirements. We focus on competition between desert bats and mesic species that recently expanded their distribution into arid environment following anthropogenic land‐use changes.

Results

We show that both climate and water availability limit bat distributions and diversity across spatial scales. The broadscale distribution of bats was determined by proximity to water and high temperatures, although the latter did not affect the distribution of mesic species. At the fine‐scale, high levels of bat activity and diversity were associated with increased water availability and warmer periods. Desert species were strongly associated with warmer and drier desert types. Range and niche overlap were high among potential competitors, but coexistence was facilitated through fine‐scale spatial partitioning of water resources.

Main conclusions

Adaptations to drier and warmer conditions allow desert‐obligate species to prevail in more arid environments. However, this competitive advantage may disappear as anthropogenic activities encroach further into desert habitats. We conclude that reduced water availability in arid environments under future climate change projections pose a major threat to desert wildlife because it can affect survival and reproductive success and may increase competition over remaining water resources.     

Mean species responses predict effects of environmental change on coexistence

Environmental change research is plagued by the curse of dimensionality: the number of communities at risk and the number of environmental drivers are both large. This raises the pressing question if a general understanding of ecological effects is achievable. Here, we show evidence that this is indeed possible. Using theoretical and simulation-based evidence for bi- and tritrophic communities, we show that environmental change effects on coexistence are proportional to mean species responses and depend on how trophic levels on average interact prior to environmental change. We then benchmark our findings using relevant cases of environmental change, showing that means of temperature optima and of species sensitivities to pollution predict concomitant effects on coexistence. Finally, we demonstrate how to apply our theory to the analysis of field data, finding support for effects of land use change on coexistence in natural invertebrate communities.     

A long-term association between global temperature and biodiversity, origination and extinction in the fossil record

The past relationship between global temperature and levels of biological diversity is of increasing concern due to anthropogenic climate warming. However, no consistent link between these variables has yet been demonstrated. We analysed the fossil record for the last 520 Myr against estimates of low latitude sea surface temperature for the same period. We found that global biodiversity (the richness of families and genera) is related to temperature and has been relatively low during warm 'greenhouse' phases, while during the same phases extinction and origination rates of taxonomic lineages have been relatively high. These findings are consistent for terrestrial and marine environments and are robust to a number of alternative assumptions and potential biases. Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner. Our findings may have implications for extinction and biodiversity change under future climate warming.     

全球气候变化对沈阳地区春玉米生长的可能影响

利用玉米（Ｚｅａ ｍａｙｓ Ｌ．）生长生理生态学模拟模型（ＭＰＥＳＭ）,分别模拟了未来气候变化的１２种气候条件下（ＣＯ２浓度倍增,平均气温上升１．５℃、３．０℃和４．５℃,降水量增加２０％、减少２０％、减少４０％和降水量不变）,沈阳地区土壤湿度、玉米发育和玉米生长的变化,并与当前条件下进行了比较,以评价玉米生长对各气候因子变化的敏感性和全球气候变化下沈阳地区春玉米的生长趋势。研究表明：土壤湿度对降     

Geographical variation and environmental correlates of functional trait distributions in palms (Arecaceae) across the New World

Functional traits play a key role in driving biodiversity effects on ecosystem functioning. Here, we examine the geographical distributions of three key functional traits in New World palms (Arecaceae), an ecologically important plant group, and their relationships with current climate, soil and glacial–interglacial climate change. We combined range maps for the New World (N = 541 palm species) with data on traits (leaf size, stem height and fruit size), representing the leaf–height–seed plant strategy scheme of Westoby, to estimate median trait values for palm species assemblages in 110 × 110‐km grid cells. Spatial and non‐spatial multi‐predictor regressions were used with the Akaike Information Criterion to identify minimum adequate models. Present‐day seasonality in temperature and precipitation played a major role in explaining geographical variation of all traits. Mean annual temperature and annual precipitation were additionally important for median leaf size. Glacial–interglacial temperature change was the most important predictor for median fruit size. Large‐scale soil gradients played only a minor role overall. These results suggest that current climate (larger median trait values with increasing seasonality) and glacial–interglacial temperature change (larger median fruit size with increasing Quaternary temperature anomaly) are important drivers for functional trait distributions of New World palms. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 602–617.     

Cyanobacterial ecology across environmental gradients and spatial scales in China's hot and cold deserts

Lithic photoautotrophic communities function as principal primary producers in the world's driest deserts, yet many aspects of their ecology remain unknown. This is particularly true for Asia, where some of the Earth's oldest and driest deserts occur. Using methods derived from plant landscape ecology, we measured the abundance and spatial distribution of cyanobacterial colonization on quartz stony pavement across environmental gradients of rainfall and temperature in the isolated Taklimakan and Qaidam Basin deserts of western China. Colonization within available habitat ranged from 0.37+/-0.16% to 12.6+/-1.8%, with cold dry desert sites exhibiting the lowest abundance. Variation between sites was most strongly correlated with moisture-related variables and was independent of substrate availability. Cyanobacterial communities were spatially aggregated at multiple scales in patterns distinct from the underlying rock pattern. Site-level differences in cyanobacterial spatial pattern (e.g. mean inter-patch distance) were linked with rainfall, whereas patchiness within sites was correlated with local geology (greater colonization frequency of large rocks) and biology (dispersal during rainfall). We suggest that cyanobacterial patchiness may also in part be self-organized - that is, an outcome of soil water-biological feedbacks. We propose that landscape ecology concepts and models linking desert vegetation, biological feedbacks and ecohydrological processes are applicable to microbial communities.     

全球气候变化对沈阳地区春玉米生长的可能影响

Physiological ecology simulation modelling of maize growth (MPESM) was used to simulate the variation of soil moisture, maize development and maize growth under twelve prescribed climate scenarios, which include doubling CO2, raising mean temperature by 1.5 ℃, 3.0 ℃ and 4.5 ℃, and changing precipitation by 0, +20%, -20%, and -40%. The simulated results were compared with that of the present climate, to assess the sensitivity of maize to climatic change. The analysis indicated that soil moisture is sensitive to reduced precipitation, maize development is sensitive to the rise of temperature, and maize growth is affected greatly by temperature elevation and precipitation variation, which cancel out the positive effects of CO2 elevation. It was found that with the severe change of climate, the leaf biomass, the female fringe biomass, and the leaf area index would decline greatly, and the biomass of stem and root would increase greatly. The average yield of maize will decline between 5% and 30%.     

Predicted effects of climate factors on mountain species are not uniform over different spatial scales

The selection of relevant factors and appropriate spatial scale(s) is fundamental when modelling species response to climate change. We evaluated whether the effects of climate factors on species distribution/occurrence are consistently modelled over different spatial scales in birds, and used a two‐scale approach to identify species–climate correlations unlikely to represent causal effects. We used passerine birds inhabiting mountain grassland in the Apennines (Italy) as a model. We surveyed four grassland species at 400 sampling points, and built habitat selection models (territory scale) and distribution models (seven algorithms, landscape scale). We compared the effect of climatic predictors on occurrence/distribution highlighted by models over the two spatial scales, and with the effects supposed a priori based on the climatic niche of each species. Models at the territory level included at least one climatic predictor for three species; the observed effect of climatic predictors was seldom consistent with supposed effects. At the broadest scale, distribution models for all species included climatic predictors, with varying consistence with supposed effects and findings at the finer scale. Despite the importance of climate for species distribution, occurrence could be more directly related to other factors, with important implications for understanding/predicting the impacts of climate/environmental changes. Our approach revealed key variables for grassland birds, and highlighted the scale‐dependent perceived importance of climate. At the local scale, climate effects were weak or hard to interpret. We found a general lack of consistence between supposed and observed effects at the territory level, and between landscape and territory models. Our results show the importance of predicting the potential effect of climatic factors prior to the analyses, carefully selecting ecologically meaningful variables and scales, and evaluating the nature and scale of climate–species links. We call for caution when predicting under future climates, especially when mechanistic effects and consistency across scales are lacking.     

Phenological indices of avian reproduction: cryptic shifts and prediction across large spatial and temporal scales

Climate change‐induced shifts in phenology have important demographic consequences, and are frequently used to assess species' sensitivity to climate change. Therefore, developing accurate phenological predictions is an important step in modeling species' responses to climate change. The ability of such phenological models to predict effects at larger spatial and temporal scales has rarely been assessed. It is also not clear whether the most frequently used phenological index, namely the average date of a phenological event across a population, adequately captures phenological shifts in the distribution of events across the season. We use the long‐tailed tit Aegithalos caudatus (Fig. 1) as a case study to explore these issues. We use an intensive 17‐year local study to model mean breeding date and test the capacity of this local model to predict phenology at larger spatial and temporal scales. We assess whether local models of breeding initiation, termination, and renesting reveal phenological shifts and responses to climate not detected by a standard phenological index, that is, population average lay date. These models take predation timing/intensity into account. The locally‐derived model performs well at predicting phenology at the national scale over several decades, at both high and low temperatures. In the local model, a trend toward warmer Aprils is associated with a significant advance in termination dates, probably in response to phenological shifts in food supply. This results in a 33% reduction in breeding season length over 17 years – a substantial loss of reproductive opportunity that is not detected by the index of population average lay date. We show that standard phenological indices can fail to detect patterns indicative of negative climatic effects, potentially biasing assessments of species' vulnerability to climate change. More positively, we demonstrate the potential of detailed local studies for developing broader‐scale predictive models of future phenological shifts.     

Environmental variation and population responses to global change

Species' responses to environmental changes such as global warming are affected not only by trends in mean conditions, but also by natural and human‐induced environmental fluctuations. Methods are needed to predict how such environmental variation affects ecological and evolutionary processes, in order to design effective strategies to conserve biodiversity under global change. Here, we review recent theoretical and empirical studies to assess: (1) how populations respond to changes in environmental variance, and (2) how environmental variance affects population responses to changes in mean conditions. Contrary to frequent claims, empirical studies show that increases in environmental variance can increase as well as decrease long‐term population growth rates. Moreover, environmental variance can alter and even reverse the effects of changes in the mean environment, such that even if environmental variance remains constant, omitting it from population models compromises their ability to predict species' responses to changes in mean conditions. Drawing on theory relating these effects of environmental variance to the curvatures of population growth responses to the environment, we outline how species' traits such as phylogenetic history and body mass could be used to predict their responses to global change under future environmental variability.     

中国裸子植物的物种多样性格局及其影响因子

物种多样性的大尺度空间格局是宏观生态学和生物地理学研究的核心问题之一。本文利用中国裸子植物分布数据, 结合气候、地形等环境信息, 分析了中国裸子植物物种多样性的大尺度格局及其影响因素, 比较了不同类群之间物种多样性格局和主导因子的差异, 并探讨了裸子植物在植物区系中所占比重的地理格局。结果表明, 中国裸子植物的物种多样性总体上呈现南高北低的趋势, 物种多样性在横断山区最高。在裸子植物的三个主要类群中, 松柏亚纲的物种多样性格局与整体相似, 买麻藤亚纲的多样性高值区则出现在中国西北部的干旱地区, 苏铁亚纲的分布区较为狭窄, 主要集中在南方地区。线性回归分析结果表明, 空间异质性和降水因子对中国裸子植物多样性格局的解释率最高, 末次冰期以来的气温变化、海拔高差和能量因子次之。这表明中国裸子植物物种多样性的格局受到了多种因素的影响, 其中空间异质性和降水因子影响最大。进一步分析发现, 物种多样性格局的主导因子在不同类群之间具有显著差异, 这可能反映了这些类群的进化历史以及生理适应的差异。裸子植物与被子植物的比例具有明显的空间格局: 在东部、南部气候环境优越的地区, 裸子植物与被子植物的比例低于0.06; 而在西部、北部等气候环境比较恶劣的地区, 裸子植物的比例则显著上升。回归分析表明, 能量和水分因子显著影响了裸子植物与被子植物的比例。随着能量的降低和降水的减少, 裸子植物与被子植物的比例会显著升高, 这可能是由于被子植物在温暖湿润地区具有较强竞争优势, 但裸子植物对极端环境具有更好的适应。     

Possible effects of global environmental changes on Antarctic benthos: a synthesis across five major taxa

Because of the unique conditions that exist around the Antarctic continent, Southern Ocean (SO) ecosystems are very susceptible to the growing impact of global climate change and other anthropogenic influences. Consequently, there is an urgent need to understand how SO marine life will cope with expected future changes in the environment. Studies of Antarctic organisms have shown that individual species and higher taxa display different degrees of sensitivity to environmental shifts, making it difficult to predict overall community or ecosystem responses. This emphasizes the need for an improved understanding of the Antarctic benthic ecosystem response to global climate change using a multitaxon approach with consideration of different levels of biological organization. Here, we provide a synthesis of the ability of five important Antarctic benthic taxa (Foraminifera, Nematoda, Amphipoda, Isopoda, and Echinoidea) to cope with changes in the environment (temperature, pH, ice cover, ice scouring, food quantity, and quality) that are linked to climatic changes. Responses from individual to the taxon-specific community level to these drivers will vary with taxon but will include local species extinctions, invasions of warmer-water species, shifts in diversity, dominance, and trophic group composition, all with likely consequences for ecosystem functioning. Limitations in our current knowledge and understanding of climate change effects on the different levels are discussed.     

Invasive termites in a changing climate: A global perspective

Termites are ubiquitous insects in tropical, subtropical, and warm temperate regions and play an important role in ecosystems. Several termite species are also significant economic pests, mainly in urban areas where they attack human‐made structures, but also in natural forest habitats. Worldwide, approximately 28 termite species are considered invasive and have spread beyond their native ranges, often with significant economic consequences. We used predictive climate modeling to provide the first global risk assessment for 13 of the world's most invasive termites. We modeled the future distribution of 13 of the most serious invasive termite species, using two different Representative Concentration Pathways (RCPs), RCP 4.5 and RCP 8.5, and two projection years (2050 and 2070). Our results show that all but one termite species are expected to significantly increase in their global distribution, irrespective of the climatic scenario and year. The range shifts by species (shift vectors) revealed a complex pattern of distributional changes across latitudes rather than simple poleward expansion. Mapping of potential invasion hotspots in 2050 under the RCP 4.5 scenario revealed that the most suitable areas are located in the tropics. Substantial parts of all continents had suitable environmental conditions for more than four species simultaneously. Mapping of changes in the number of species revealed that areas that lose many species (e.g., parts of South America) are those that were previously very species‐rich, contrary to regions such as Europe that were overall not among the most important invasion hotspots, but that showed a great increase in the number of potential invaders. The substantial economic and ecological damage caused by invasive termites is likely to increase in response to climate change, increased urbanization, and accelerating economic globalization, acting singly or interactively.     

Bioenergy production potential of global biomass plantations under environmental and agricultural constraints

We estimate the global bioenergy potential from dedicated biomass plantations in the 21st century under a range of sustainability requirements to safeguard food production, biodiversity and terrestrial carbon storage. We use a process‐based model of the land biosphere to simulate rainfed and irrigated biomass yields driven by data from different climate models and combine these simulations with a scenario‐based assessment of future land availability for energy crops. The resulting spatial patterns of large‐scale lignocellulosic energy crop cultivation are then investigated with regard to their impacts on land and water resources. Calculated bioenergy potentials are in the lower range of previous assessments but the combination of all biomass sources may still provide between 130 and 270 EJ yr^?1 in 2050, equivalent to 15–25% of the World's future energy demand. Energy crops account for 20–60% of the total potential depending on land availability and share of irrigated area. However, a full exploitation of these potentials will further increase the pressure on natural ecosystems with a doubling of current land use change and irrigation water demand. Despite the consideration of sustainability constraints on future agricultural expansion the large‐scale cultivation of energy crops is a threat to many areas that have already been fragmented and degraded, are rich in biodiversity and provide habitat for many endangered and endemic species.