Mercury in Nelson's Sparrow subspecies at breeding sites

Background

Mercury is a persistent, biomagnifying contaminant that can cause negative effects on ecosystems. Marshes are often areas of relatively high mercury methylation and bioaccumulation. Nelson''s Sparrows (Ammodramus nelsoni) use marsh habitats year-round and have been documented to exhibit tissue mercury concentrations that exceed negative effects thresholds. We sought to further characterize the potential risk of Nelson''s Sparrows to mercury exposure by sampling individuals from sites within the range of each of its subspecies.

Methodology/Principal Findings

From 2009 to 2011, we captured adult Nelson''s Sparrows at sites within the breeding range of each subspecies (A. n. nelsoni: Grand Forks and Upham, North Dakota; A. n. alterus: Moosonee, Ontario; and A. n. subvirgatus: Grand Manan Island, New Brunswick) and sampled breast feathers, the first primary feather (P1), and blood for total mercury analysis. Mean blood mercury in nelsoni individuals captured near Grand Forks ranged from 0.84±0.37 to 1.65±1.02 SD ppm among years, between 2.0 and 4.9 times as high as concentrations at the other sites (P<0.01). Breast feather mercury did not vary among sites within a given sampling year (site means ranged from 0.98±0.69 to 2.71±2.93 ppm). Mean P1 mercury in alterus (2.96±1.84 ppm fw) was significantly lower than in any other sampled population (5.25±2.24–6.77±3.51 ppm; P≤0.03).

Conclusions/Significance

Our study further characterized mercury in Nelson''s Sparrows near Grand Forks; we documented localized and potentially harmful mercury concentrations, indicating that this area may represent a biological mercury hotspot. This finding warrants further research to determine if wildlife populations of conservation or recreational interest in this area may be experiencing negative effects due to mercury exposure. We present preliminary conclusions about the risk of each sampled population to mercury exposure.     

Community assembly during vegetation succession after metal mining is driven by multiple processes with temporal variation

The mechanisms governing community assembly is fundamental to ecological restoration and clarification of the assembly processes associated with severe disturbances (characterized by no biological legacy and serious environmental problems) is essential. However, a systematic understanding of community assembly in the context of severe anthropogenic disturbance remains lacking. Here, we explored community assembly processes after metal mining, which is considered to be a highly destructive activity to provide insight into the assembly rules associated with severe anthropogenic disturbance. Using a chronosequence approach, we selected vegetation patches representing different successional stages and collected data on eight plant functional traits from each stage. The traits were classified as establishment and regenerative traits. Based on these traits, null models were constructed to identify the processes driving assembly at various successional stages. Comparison of our observations with the null models indicated that establishment and regenerative traits converged in the primary stage of succession. As succession progressed, establishment traits shifted to neutral assembly, whereas regeneration traits alternately converged and diverged. The observed establishment traits were equal to expected values, whereas regenerative traits diverged significantly after more than 20 years of succession. Furthermore, the available Cr content was linked strongly to species'' ecological strategies. In the initial stages of vegetation succession in an abandoned metal mine, the plant community was mainly affected by the available metal content and dispersal limitation. It was probably further affected by strong interspecific interaction after the environmental conditions had improved, and stochastic processes became dominant during the stage with a successional age of more than 20 years.     

Traits of benthic macroinvertebrates in semi-natural French streams: an initial application to biomonitoring in Europe

• 1 The methods used to indicate the biological state of streams are often based on taxonomic composition, and the abundance of species or other taxa. This ‘taxonomic structure’ varies among ecoregions and cannot be applied to wider geographical areas. Therefore, we assessed the species traits of benthic macroinvertebrates from semi‐natural reference sites as a potential benchmark for large‐scale biomonitoring. Our purpose was to assess the stability of community structure, based on the representation of taxa and of traits, across large gradients of geology (sedimentary to granitic), altitude (65–1982 m), geographical coordinates (0° 48′ W to 7° 20′ E and 42° 52′ to 48° 44′ N), stream order (1–5) and slope (0.5–60‰).
• 2 We used invertebrate abundance data from the 62 most natural French stream sites available. These abundance data served to weight the occurrence of ‘biological’ traits, such as reproductive characteristics, mobility, resistance forms, food, feeding habits, respiration, and ‘ecological’ traits, such as preferences for temperature, trophic level, saprobity, biogeographic distribution, longitudinal zonation, substratum and current velocity.
• 3 Multivariate analyses of taxonomic composition demonstrated a clear site gradient from lowlands to uplands and from calcareous to granitic geology. In contrast, community structure based on both biological and ecological traits was stable across environmental gradients.
• 4 The frequency distribution of biological traits indicated that the stream benthos of the ‘reference sites’ had a mixture of categories which confirmed theoretical predictions for temporally stable and spatially variable habitats. A mixture of ecological trait categories also occurred at our reference sites. Thus, semi‐natural benthic macroinvertebrate communities are functionally diverse. Moreover, we included an initial application of these traits to a case of slightly to moderately polluted sites to show that the impact of humans significantly changes this natural functional diversity.
• 5 Future studies should focus on the potential for various biological and ecological traits to discriminate different human impacts on the benthic macroinvertebrates of running waters, and on the integration of this functional application into a general ‘reference‐condition’ approach.

     

鄱阳湖湿地大型底栖无脊椎动物多样性对群落次级生产力及稳定性的影响

理解生物多样性对生态系统功能及稳定性的影响对于制定有效的保护管理策略有重要意义。然而,目前生物多样性与群落生产力、稳定性的关系仍存在争议。在鄱阳湖湿地布设30个采样点,于2019年秋季开展大型底栖无脊椎动物群落野外调查。基于底栖动物群落数据,采用广义加性模型分析物种、谱系、功能多样性对鄱阳湖湿地底栖动物群落次级生产力与稳定性的影响。结果表明:底栖动物群落的次级生产力与反映物种多样性的指数(Simpson多样性指数、Shannon-Wiener多样性指数、Pielou均匀度指数)、分类多样性指数、平均分类差异指数、功能丰富度指数等呈显著的负相关,其中Pielou均匀度指数与次级生产力的相关度最高(r²=0.33)。功能多样性对群落次级生产力的空间分异有最高的解释度(r²=0.75)。P/B值(次级生产力与生物量之比代表群落稳定性)与物种、谱系、功能多样性指数均呈正相关,其中功能丰富度与P/B值的相关度最高(r²=0.22)。反映物种多样性的三个指数总体上对P/B值的空间分异解释度最高(r²=0.37)。谱系多样性与次级生产力、P/B值的相关性相对较弱。生物多样性指数总体分别解释了次级生产力和群落稳定性中81.9%、54.8%的变异。上述研究结果表明,生物多样性与群落生产力、稳定性的关系可能因具体的生物群落而异。研究结果对于鄱阳湖湿地的底栖生物多样性保护有参考价值。     

Plant morphometric traits and climate gradients in northern China: a meta-analysis using quadrat and flora data

Background and Aims

The collection of field data on plant traits is time consuming and this makes it difficult to examine changing patterns of traits along large-scale climate gradients. The present study tests whether trait information derived from regional floras can be used in conjunction with pre-existing quadrat data on species presence to derive meaningful relationships between specific morphometric traits and climate.

Methods

Quadrat records were obtained for 867 species in 404 sites from northern China (38–49°N, 82–132°E) together with information on the presence/absence of key traits from floras. Bioclimate parameters for each site were calculated using the BIOME3 model. Principal component analysis and correlation analysis were conducted to determine the most important climate factors. The Akaike Information Criterion was used to select the best relationship between each trait and climate. Canonical correspondence analysis was used to explore the relationships between climate and trait occurrence.

Key Results

The changing abundance of life form, leaf type, phenology, photosynthetic pathway, leaf size and several other morphometric traits are determined by gradients in plant-available moisture (as measured by the ratio of actual to potential evapotranspiration: α), growing-season temperature (as measured by growing degree-days on a 0 ° base: GDD₀) or a combination of these. Different plant functional types (PFTs, as defined by life form, leaf type and phenology) reach maximum abundance in distinct areas of this climate space: for example, evergreen trees occur in the coldest, wettest environments (GDD₀ < 2500 °Cd, α > 0·38), and deciduous scale-leaved trees occur in drier, warmer environments than deciduous broad-leaved trees. Most leaf-level traits show similar relationships with climate independently of PFT: for example, leaf size in all PFTs increases as the environment becomes wetter and cooler. However, some traits (e.g. petiole length) display different relationships with climate in different PFTs.

Conclusions

Based on presence/absence species data and flora-based trait assignments, the present study demonstrates ecologically plausible trends in the occurrence of key plant traits along climate gradients in northern China. Life form, leaf type, phenology, photosynthetic pathway, leaf size and other key traits reflect climate. The success of these analyses opens the possibility of using quadrat- and flora-based trait analyses to examine climate–trait relationships in other regions of the world.     

Using Plant Functional Traits and Phylogenies to Understand Patterns of Plant Community Assembly in a Seasonal Tropical Forest in Lao PDR

Plant functional traits reflect different evolutionary responses to environmental variation, and among extant species determine the outcomes of interactions between plants and their environment, including other plant species. Thus, combining phylogenetic and trait-based information can be a powerful approach for understanding community assembly processes across a range of spatial scales. We used this approach to investigate tree community composition at Phou Khao Khouay National Park (18°14’-18°32’N; 102°38’- 102°59’E), Laos, where several distinct forest types occur in close proximity. The aim of our study was to examine patterns of plant community assembly across the strong environmental gradients evident at our site. We hypothesized that differences in tree community composition were being driven by an underlying gradient in soil conditions. Thus, we predicted that environmental filtering would predominate at the site and that the filtering would be strongest on sandier soil with low pH, as these are the conditions least favorable to plant growth. We surveyed eleven 0.25 ha (50x50 m) plots for all trees above 10 cm dbh (1221 individual trees, including 47 families, 70 genera and 123 species) and sampled soils in each plot. For each species in the community, we measured 11 commonly studied plant functional traits covering both the leaf and wood economic spectrum traits and we reconstructed a phylogenetic tree for 115 of the species in the community using rbcL and matK sequences downloaded from Genebank (other species were not available). Finally we compared the distribution of trait values and species at two scales (among plots and 10x10m subplots) to examine trait and phylogenetic community structures. Although there was strong evidence that an underlying soil gradient was determining patterns of species composition at the site, our results did not support the hypothesis that the environmental filtering dominated community assembly processes. For the measured plant functional traits there was no consistent pattern of trait dispersion across the site, either when traits were considered individually or when combined in a multivariate analysis. However, there was a significant correlation between the degree of phylogenetic dispersion and the first principle component axis (PCA1) for the soil parameters. Moreover, the more phylogenetically clustered plots were on sandier soils with lower pH. Hence, we suggest that the community assembly processes across our site may reflect the influence of more conserved traits that we did not measure. Nevertheless, our results are equivocal and other interpretations are possible. Our study illustrates some difficulties in combining trait and phylogenetic approaches that may result from the complexities of integrating spatial and evolutionary processes that vary at different scales.     

Disturbance regime changes the trait distribution,phylogenetic structure and community assembly of tropical rain forests

A rapidly increasing effort to merge functional community ecology and phylogenetic biology has increased our understanding of community assembly. However, studies using both phylogenetic‐ and trait‐based methods have been mainly conducted in old‐growth forests, with fewer studies in human‐disturbed communities, which play an increasingly important role in providing ecosystem services as primary forests are degraded. We used data from 18 1‐ha plots in tropical old‐growth forests and secondary forests with different disturbance histories (logging and shifting cultivation) and vegetation types (tropical lowland and montane forests) on Hainan Island, southern China. The distributions of 11 functional traits were compared among these six forest types. We used a null model approach to assess the effects of disturbance regimes on variation in response and effect traits and community phylogenetic structure across different stem sizes (saplings, treelets, and adult trees) and spatial scales (10–50 m). We found significant differences in the distribution of functional traits in highly disturbed lowland sites versus other forest types. Many individuals in highly disturbed lowland sites were deciduous, spiny, with non‐fleshy fruits and seeds dispersed passively or by wind, and low SLA. The response traits of coexisting species were clustered in all sites except for highly disturbed lowland sites where evenness was evident. There were different distributions of effect traits for saplings and treelets among different forest types but adult trees showed stronger clustering of trait values with increasing spatial scale among all forest types. Phylogenetic clustering predominated across all size classes and spatial scales in the highly disturbed lowland sites, and evenness in other forest types. High disturbance can lead to abiotic filtering, generating a community dominated by closely related species with disturbance‐adapted traits, where biotic interactions play a relatively minor role. In lightly disturbed and old growth forests, multiple processes simultaneously drive the community assembly, but biotic processes dominate at the fine scale.     

Endocrine mechanisms,behavioral phenotypes and plasticity: known relationships and open questions

Behavior of wild vertebrate individuals can vary in response to environmental or social factors. Such within-individual behavioral variation is often mediated by hormonal mechanisms. Hormones also serve as a basis for among-individual variations in behavior including animal personalities and the degree of responsiveness to environmental and social stimuli. How do relationships between hormones and behavioral traits evolve to produce such behavioral diversity within and among individuals? Answering questions about evolutionary processes generating among-individual variation requires characterizing how specific hormones are related to variation in specific behavioral traits, whether observed hormonal variation is related to individual fitness and, whether hormonal traits are consistent (repeatable) aspects of an individual's phenotype. With respect to within-individual variation, we need to improve our insight into the nature of the quantitative relationships between hormones and the traits they regulate, which in turn will determine how they may mediate behavioral plasticity of individuals. To address these questions, we review the actions of two steroid hormones, corticosterone and testosterone, in mediating changes in vertebrate behavior, focusing primarily on birds. In the first part, we concentrate on among-individual variation and present examples for how variation in corticosterone concentrations can relate to behaviors such as exploration of novel environments and parental care. We then review studies on correlations between corticosterone variation and fitness, and on the repeatability over time of corticosterone concentrations. At the end of this section, we suggest that further progress in our understanding of evolutionary patterns in the hormonal regulation of behavior may require, as one major tool, reaction norm approaches to characterize hormonal phenotypes as well as their responses to environments.In the second part, we discuss types of quantitative relationships between hormones and behavioral traits within individuals, using testosterone as an example. We review conceptual models for testosterone-behavior relationships and discuss the relevance of these models for within-individual plasticity in behavior. Next, we discuss approaches for testing the nature of quantitative relationships between testosterone and behavior, concluding that again reaction norm approaches might be a fruitful way forward.We propose that an integration of new tools, especially of reaction norm approaches into the field of behavioral endocrinology will allow us to make significant progress in our understanding of the mechanisms, the functional implications and the evolution of hormone–behavior relationships that mediate variation both within and among individuals. This knowledge will be crucial in light of already ongoing habitat alterations due to global change, as it will allow us to evaluate the mechanisms as well as the capacity of wild populations to adjust hormonally-mediated behaviors to altered environmental conditions.     

Kin selection,species richness and community

Can evolutionary and ecological dynamics operating at one level of the biological hierarchy affect the dynamics and structure at other levels? In social insects, strong hostility towards unrelated individuals can evolve as a kin-selected counter-adaptation to intraspecific social parasitism. This aggression in turn might cause intraspecific competition to predominate over interspecific competition, permitting coexistence with other social insect species. In other words, kin selection—a form of intra-population dynamics—might enhance the species richness of the community, a higher-level structure. The converse effect, from higher to lower levels, might also operate, whereby strong interspecific competition may limit the evolution of selfish individual traits. If the latter effect were to prove more important, it would challenge the common view that intra-population dynamics (via individual or gene selection) is the main driver of evolution.     

Which Way Is Down? Positional Distortion in the Tilt Illusion

Contextual information can have a huge impact on our sensory experience. The tilt illusion is a classic example of contextual influence exerted by an oriented surround on a target''s perceived orientation. Traditionally, the tilt illusion has been described as the outcome of inhibition between cortical neurons with adjacent receptive fields and a similar preference for orientation. An alternative explanation is that tilted contexts could produce a re-calibration of the subjective frame of reference. Although the distinction is subtle, only the latter model makes clear predictions for unoriented stimuli. In the present study, we tested one such prediction by asking four naive subjects to estimate three positions (4, 6, and 8 o''clock) on an imaginary clock face within a tilted surround. To indicate their estimates, they used either an unoriented dot or a line segment, with one endpoint at fixation in the middle of the surround. The surround''s tilt was randomly chosen from a set of orientations (±75°, ±65°, ±55°, ±45°, ±35°, ±25°, ±15°, ±5° with respect to vertical) across trials. Our results showed systematic biases consistent with the tilt illusion in both conditions. Biases were largest when observers attempted to estimate the 4 and 8 o''clock positions, but there was no significant difference between data gathered with the dot and data gathered with the line segment. A control experiment confirmed that biases were better accounted for by a local coordinate shift than to torsional eye movements induced by the tilted context. This finding supports the idea that tilted contexts distort perceived positions as well as perceived orientations and cannot be readily explained by lateral interactions between orientation selective cells in V1.     

Biogeography of the livebearing fish Poecilia gillii in Costa Rica: are phylogeographical breaks congruent with fish community boundaries?

One of the original goals of phylogeography was to use genetic data to identify historical events that might contribute to breaks among communities. In this study, we examine the phylogeography of a common livebearing fish ( Poecilia gillii ) from Costa Rica. Our goal was to determine if phylogeographical breaks in this species were congruent with previously defined boundaries among four fish community provinces. We hypothesized that if abiotic factors influence both community boundaries and genetic structuring in P. gillii then we might find four clades within our focal species that were geographically separated along community boundary lines. Similarly, we expected to find most of the genetic variation in P. gillii partitioned among these four geographical regions. We generated DNA sequence data (mitochondrial cytochrome b and nuclear S7 small ribosomal subunit) for 260 individuals from 42 populations distributed across Costa Rica. We analysed these data using phylogenetic (parsimony and likelihood) and coalescent approaches to estimate phylogenetic relationships among haplotypes, patterns of gene flow and effective population size . Contrary to our expectations, we did not find four monophyletic groups that mapped cleanly to our geographical community provinces. However, one of our clades was restricted to a single province, suggesting that common earth history events could be responsible for both genetic structuring in P. gillii and fish community composition in this area. However, our results show a complex pattern of gene flow throughout other regions in Costa Rica where genetic structuring is not predicted by community province boundaries.     

Genome-wide association study of relative telomere length

Telomere function is essential to maintaining the physical integrity of linear chromosomes and healthy human aging. The probability of forming proper telomere structures depends on the length of the telomeric DNA tract. We attempted to identify common genetic variants associated with log relative telomere length using genome-wide genotyping data on 3,554 individuals from the Nurses'' Health Study and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial that took part in the National Cancer Institute Cancer Genetic Markers of Susceptibility initiative for breast and prostate cancer. After genotyping 64 independent SNPs selected for replication in additional Nurses'' Health Study and Women''s Genome Health Study participants, we did not identify genome-wide significant loci; however, we replicated the inverse association of log relative telomere length with the minor allele variant [C] of rs16847897 at the TERC locus (per allele β = −0.03, P = 0.003) identified by a previous genome-wide association study. We did not find evidence for an association with variants at the OBFC1 locus or other loci reported to be associated with telomere length. With this sample size we had >80% power to detect β estimates as small as ±0.10 for SNPs with minor allele frequencies of ≥0.15 at genome-wide significance. However, power is greatly reduced for β estimates smaller than ±0.10, such as those for variants at the TERC locus. In general, common genetic variants associated with telomere length homeostasis have been difficult to detect. Potential biological and technical issues are discussed.     

Trait means or variance—What determines plant species' local and regional occurrence in fragmented dry grasslands?

One of the few laws in ecology is that communities consist of few common and many rare taxa. Functional traits may help to identify the underlying mechanisms of this community pattern, since they correlate with different niche dimensions. However, comprehensive studies are missing that investigate the effects of species mean traits (niche position) and intraspecific trait variability (ITV, niche width) on species abundance. In this study, we investigated fragmented dry grasslands to reveal trait‐occurrence relationships in plants at local and regional scales. We predicted that (a) at the local scale, species occurrence is highest for species with intermediate traits, (b) at the regional scale, habitat specialists have a lower species occurrence than generalists, and thus, traits associated with stress‐tolerance have a negative effect on species occurrence, and (c) ITV increases species occurrence irrespective of the scale. We measured three plant functional traits (SLA = specific leaf area, LDMC = leaf dry matter content, plant height) at 21 local dry grassland communities (10 m × 10 m) and analyzed the effect of these traits and their variation on species occurrence. At the local scale, mean LDMC had a positive effect on species occurrence, indicating that stress‐tolerant species are the most abundant rather than species with intermediate traits (hypothesis 1). We found limited support for lower specialist occurrence at the regional scale (hypothesis 2). Further, ITV of LDMC and plant height had a positive effect on local occurrence supporting hypothesis 3. In contrast, at the regional scale, plants with a higher ITV of plant height were less frequent. We found no evidence that the consideration of phylogenetic relationships in our analyses influenced our findings. In conclusion, both species mean traits (in particular LDMC) and ITV were differently related to species occurrence with respect to spatial scale. Therefore, our study underlines the strong scale‐dependency of trait‐abundance relationships.     

Pleistocene climate fluctuations as the major driver of genetic diversity and distribution patterns of the Caspian green lizard,Lacerta strigata Eichwald, 1831

Green lizards of the genus Lacerta have served as excellent models for studying the impact of Pleistocene climatic oscillations on genetic structures. The Caspian green lizard, Lacerta strigata, occupies various habitats across the Caucasus and the South Caspian Sea, with the Hyrcanian Forests and north of the Alborz Mountains forming the core of the range. This study aimed to re‐examine the phylogenetic relationships of L. strigata with other congeneric members and to assess the genetic structure and historical demography of the species. Furthermore, Species Distribution Models (SDMs) were performed to infer the species'' potential habitat suitability and were then projected on climate scenarios reflecting current and past (6 ky and 21 ky before present) conditions. A total of 39 individuals collected from most of the distribution range, together with additional lacertid species sequences from the GenBank database, were examined using mtDNA (Cyt b and 12S ribosomal RNA) and nuclear (C‐mos and β‐fibrinogen) sequence data. Based on the phylogenetic analyses, L. strigata was found to be a sister taxon to all other members of the genus. The species included two main clades (regional western and eastern) that diverged in a period between the Early and Middle Pleistocene. Based on the BBM and S‐Diva analyses, both dispersal and vicariance events explained the phylogeographic structure of the species in the Hyrcanian Forests. The historical demographic analyses using Bayesian skyline plots showed a mild increase in the effective population size from about 120 Kya for the western regional clade. According to phylogeographic structures and SDMs evidence, as in other species within the region, it appears that the south of the Caspian Sea (Hyrcanian Forests), and the Alborz Mountains acted as multiple refugia during cold periods and promoted expansion outwards amid the warm periods. Overall, the results provided evidence that the genetic structure of the species has been influenced by the Pleistocene climatic fluctuations.     

The distribution,abundance and seasonality of pelagic marine invertebrate larvae in the maritime Antarctic

A survey of pelagic larvae was undertaken between November 1992 and February 1995 at Signy Island, Antarctica (60° 43 minutes S, 45° 36 minutes W). A diver-towed net and hand-held plankton pump were used at five sites of varying depths (6 to 30 m) and benthic substrata, in a combination of monthly and fortnightly samples. Overall larval ecological diversity was much higher than expected, with 131 morphologically distinct larval forms collected, apparently representing most of the benthic phyla present. The species richness observed is comparable with levels recorded at temperate latitudes, and higher than Arctic data and the implications for Thorson''s rule (the inferred cline of reduced pelagic larval diversity towards high latitudes) is discussed. Larval abundances were low (mean 2.6 individuals per cubic metre) which were two to six orders of magnitude lower than peaks in comparable data from temperate and tropical zones. We suggest that the low abundances recorded are a reflection of both slow developmental rates and a high dilution of larvae, reducing synchrony and spreading larvae over larger distances. Three seasonal periods, during which different larval types occur, have been identified. Summer, late summer and winter spawning strategies were discernable, and in some groups larvae occurred throughout the year.     

Plant Functional Traits Show Non-Linear Response to Grazing

The trait-based approach aims to detect functional patterns in vegetation beyond specific sites or taxa. In most cases, plant traits are assumed to be linearly related to environmental gradients such as grazing intensity. To generalize results beyond specific sites, it is important to know to which extent environment-trait relationships are non-linear. Non-linearity can be a source of inconsistency among different studies according to length and studied portion of a gradient. In this study, we test if and to what extent traits relate non-linearly to a grazing gradient using data from a grassland-matorral interface in the Mediterranean rangeland of “La Crau” (SE France). Because quantification of grazing by itinerant sheep flocks is difficult, we use a marker plant, Phillyrea angustifolia, and several independent pasture indicators to estimate grazing intensity. First, we related traits to grazing using a multivariate three-table ordination method (RLQ), which assumes linear reactions of traits. To evaluate the importance of non-linearity, we applied generalized additive models (GAMs) to our data. This revealed that a third of traits studied here showed non-linear relationships to grazing. These non-linear responses cover a large spectrum including seed mass, life form, phenology dispersal- and leaf traits. The high part of non-linear relations compromises a general assumption of linear trait-environment relationships. Future works should therefore more often consider non-linear relationships using methods with no constraints on shape of response, e.g., GAM in the analysis of functional trait studies. In this way, non-linear relationships can reveal new aspects of species and community response to global change and deepen our understanding of trait-environment relations.     

Molecular evidence for hybridization in Colias (Lepidoptera: Pieridae): are Colias hybrids really hybrids?

Gene flow and hybridization among species dramatically affect our understanding of the species as a biological unit, species relationships, and species adaptations. In North American Colias eurytheme and Colias eriphyle, there has been historical debate over the extent of hybridization occurring and the identity of phenotypically intermediate individuals as genetic hybrids. This study assesses the population structure of these two species to measure the extent of hybridization and the genetic identity of phenotypic intermediates as hybrids. Amplified fragment length polymorphism (AFLP) marker analysis was performed on 378 specimens collected from northern California and Nevada. Population structure was inferred using a Bayesian/Markov chain Monte Carlo method, which probabilistically assigns individuals to genetic clusters. Three genetic clusters provided the best fit for the data. C. eurytheme individuals were primarily assigned to two closely related clusters, and C. eriphyle individuals were mostly assigned to a third, more distantly related cluster. There appeared to be significant hybridization between the two species. Individuals of intermediate phenotype (putative hybrids) were found to be genetically indistinguishable from C. eriphyle, indicating that previous work based on the assumption that these intermediate forms are hybrids may warrant reconsideration.     

钱塘江中游水生昆虫群落功能多样性对土地利用变化的响应

基于11个反映水生昆虫生活史、对外界抵抗力和生理特征的生物学性状,应用目前国际上通用的fourth-corner统计方法,系统研究了浙江省钱塘江中游流域水生昆虫功能多样性对土地利用变化的响应.结果表明： 部分生物学性状对土地利用变化敏感,且其随人类干扰强度的变化所发生的改变与预期吻合,其最大个体长度逐渐下降,呼吸方式从以鳃呼吸为主转变为以表皮呼吸为主,掘穴者数量显著增加.参照点的功能多样性指数(Rao值)显著高于干扰点(P<0.001).说明人类活动引起的土地利用变化导致溪流水质和栖境质量下降,引起群落的变异和对生物性状组成的筛选,最终导致水生昆虫群落功能多样性改变.生物性状及功能多样性是未来评价生态健康的潜在指标.     

Predicting small‐mammal responses to climatic warming: autecology,geographic range,and the Holocene fossil record

Forecasting how species will respond to climatic change requires knowledge of past community dynamics. Here we use time‐series data from the small‐mammal fossil records of two caves in the Great Basin of the American West to evaluate how contrasting and variable local paleoclimates have shaped small‐mammal abundance dynamics over the last ～7500 years of climatic change. We then predict how species and communities will respond to future scenarios of increased warming and aridity coupled with continued spread of an invasive annual grass (Bromus tectorum). We find that most community‐level responses to climatic change occur in the mammalian abundance structure at both sites; the dominance of the community by individuals from species with a southern geographic affinity increases with climatic warming. This suggests that responses occurred in situ rather than by the immigration of new taxa over this time interval. Despite predictability at the community‐scale, species‐level relationships between abundance and climate are variable and are not necessarily explained by a species' geographic affinity. Species present at both sites, however, exhibit remarkably similar responses to climate at each site, indicating that species autecology (specifically dietary functional group) is important in determining response to climatic warming. Regression‐tree analyses show remarkable concordance between the two cave faunas and highlight the importance of a granivorous dietary strategy in this desert ecosystem. Under projections of increased temperature and decreased precipitation over the next 50 years, our results indicate that granivores should thrive as communities become more dominated by individuals with a southern geographic affinity. Granivores, however, are negatively impacted by the invasion of cheatgrass. The last century of anthropogenic impacts has thus placed granivores at a greater risk of extinction than predicted under climate‐only scenarios.