Body size‐dependent responses of a marine fish assemblage to climate change and fishing over a century‐long scale

Commercial fishing and climate change have influenced the composition of marine fish assemblages worldwide, but we require a better understanding of their relative influence on long‐term changes in species abundance and body‐size distributions. In this study, we investigated long‐term (1911–2007) variability within a demersal fish assemblage in the western English Channel. The region has been subject to commercial fisheries throughout most of the past century, and has undergone interannual changes in sea temperature of over 2.0 °C. We focussed on a core 30 species that comprised 99% of total individuals sampled in the assemblage. Analyses showed that temporal trends in the abundance of smaller multispecies size classes followed thermal regime changes, but that there were persistent declines in abundance of larger size classes. Consistent with these results, larger‐growing individual species had the greatest declines in body size, and the most constant declines in abundance, while abundance changes of smaller‐growing species were more closely linked to preceding sea temperatures. Together these analyses are suggestive of dichotomous size‐dependent responses of species to long‐term climate change and commercial fishing over a century scale. Small species had rapid responses to the prevailing thermal environment, suggesting their life history traits predisposed populations to respond quickly to changing climates. Larger species declined in abundance and size, reflecting expectations from sustained size‐selective overharvesting. These results demonstrate the importance of considering species traits when developing indicators of human and climatic impacts on marine fauna.     

'Back to the future': how archaeological remains can describe salmon adaptation to climate change

A strategy for species to survive climate change will be to change adaptively their way of life. Understanding rapid adaptation to climate change is therefore a priority for current research. In this issue, Turrero et al. (2012) use an original approach to unravel life history trait responses to climate change in two fish species (Salmo trutta and S. salar). Going against the flow, the authors adopt the strategy of going back to the future by investigating the responses of fish to the warming periods that followed the Last Glacial Period (approximately 30-20,000 years BP). To do this, they analysed Salmo vertebrae from well-dated archaeological sites in northern Spain in order to uncover key life history traits, which they then compared to those of contemporary specimens. They found that, as the climate got warmer, Salmo species tended to reduce the time spent in growing areas and reached spawning areas at a younger age; this tendency began approximately 15,000 years BP and accelerated in contemporary periods. The implication is a lower age at maturity and a lower reproductive success, which they tentatively related to recent declines in population growth rate. This innovative study demonstrates how changes in life history traits are linked both to the population growth rate and to the evolutionary rate under climatic constraints, which may serve as a basis for future conservation research.     

Life‐history innovation to climate change: can single‐brooded migrant birds become multiple breeders?

When climatic conditions change and become outside the range experienced in the past, species may show life‐history innovations allowing them to adapt in new ways. We report such an innovation for pied flycatchers Ficedula hypoleuca. Decades of breeding biological studies on pied flycatchers have rarely reported multiple breeding in this long‐distance migrant. In two populations, we found 12 recent incidents of females with second broods, all produced by extremely early laying females in warm springs. As such early first broods are a recent phenomenon, because laying dates have gradually advanced over time, this innovation now allows individual females to enhance their reproductive success considerably. If laying dates continue advancing, potentially more females may become multiple breeders and selection for early (and multiple) breeding phenotypes increases, which may accelerate adaptation to climatic change.     

植物功能性状对全球气候变化的指示作用研究进展

以大气CO2浓度升高、大气温度升高、干旱胁迫加剧及紫外辐射增强为特征的全球变化对陆地生态系统产生巨大影响,植物作为陆地生态系统的重要组成部分,其功能性状对全球变化的指示作用为探寻全球变化规律、减缓气候变化提供了科学依据。该文主要综述了植物生理功能性状改变(形态变化、气孔调节、光合结构及光合途径改变和植物光合、呼吸速率及水分生理变化等)和物候功能性状改变对全球变化的指示作用,以及植物群落物种丰富度或数量增加等群落特征变化对全球气候变暖的指示作用。最后指出,完善植物功能性状指标和建立从植物个体、群落到生态系统功能的网络指示系统是今后植物功能性状指示研究的发展方向。     

降水梯度带榆树枝叶协作关系的区域分异规律

伴随着降水特征变化(如干旱、干季延长或干湿交替加剧), 与之相耦合的植物功能性状也将随之发生变异, 继而引发植物功能性状的协作关系(单个器官内或多个器官间)发生相应调整, 以此为基础的植物行为和适应策略随之改变。但对这一过程背后的数量关系和作用机制仍然不清楚。以功能性状为切入点, 沿降水梯度带跨区域原位测量共有种对气候环境的特异性反应, 量化这些特异性反应背后的性状-环境关系, 阐明其调控机制, 揭示共有种功能性状及其适应策略的区域分异规律, 将为气候治理提供数据支撑和坚实的科学基础。该研究在中国东南至西北的降水梯度带上选取10个样地, 以样带共有种榆树(Ulmus pumila)为实验对象, 测量其枝和叶共28个功能性状。分析了榆树枝和叶性状以及性状间权衡关系的区域分异规律, 进一步量化不同器官(枝和叶)间功能性状协作关系沿降水梯度带的区域分异, 揭示了榆树对不同水分环境的适应策略。结果表明: (1)在湿润区, 榆树枝条具有最大的输水效率(K_s)和最小的栓塞抗性(P₅₀); 随降水量减少, 叶片厚度、叶组织紧密度增加, 榆树的抗旱能力增强。(2)在整个降水梯度带上, 榆树同一器官(枝)内及不同器官(枝和叶)间均存在效率-安全权衡; 但在区域尺度上, 这种权衡关系随降水量的减少而解耦。(3)枝和叶功能性状相关分析表明: 在整个降水梯度带上, 最大净光合速率(P_n)和比叶质量(LMA)均与K_s负相关, 与P₅₀正相关。榆树通过枝水分运输能力和叶功能性状(叶片厚度和气孔打开比率)协同调控光合能力, 枝和叶功能性状的调整与协作是榆树适应不同水分环境的重要机制。     

Do species’ traits predict recent shifts at expanding range edges?

Although some organisms have moved to higher elevations and latitudes in response to recent climate change, there is little consensus regarding the capacity of different species to track rapid climate change via range shifts. Understanding species' abilities to shift ranges has important implications for assessing extinction risk and predicting future community structure. At an expanding front, colonization rates are determined jointly by rates of reproduction and dispersal. In addition, establishment of viable populations requires that individuals find suitable resources in novel habitats. Thus, species with greater dispersal ability, reproductive rate and ecological generalization should be more likely to expand into new regions under climate change. Here, we assess current evidence for the relationship between leading-edge range shifts and species' traits. We found expected relationships for several datasets, including diet breadth in North American Passeriformes and egg-laying habitat in British Odonata. However, models generally had low explanatory power. Thus, even statistically and biologically meaningful relationships are unlikely to be of predictive utility for conservation and management. Trait-based range shift forecasts face several challenges, including quantifying relevant natural history variation across large numbers of species and coupling these data with extrinsic factors such as habitat fragmentation and availability.