Marine fisheries as ecological experiments

There are many examples of ecological theory informing fishery management. Yet fisheries also provide tremendous opportunities to test ecological theory through large-scale, repeated, and well-documented perturbations of natural systems. Although treating fisheries as experiments presents several challenges, few comparable tests exist at the ecosystem scale. Experimental manipulations of fish populations in lakes have been widely used to develop and test ecological theory. Controlled manipulation of fish populations in open marine systems is rarely possible, but fisheries data provide a valuable substitute for such manipulations. To highlight the value of marine fisheries data, we review leading ecological theories that have been empirically tested using such data. For example, density dependence has been examined through meta-analysis of spawning stock and recruitment data to show that compensation (higher population growth) occurs commonly when populations are reduced to low levels, while depensation (the Allee effect) is rare. As populations decline, spatial changes typically involve populations contracting into high-density core habitats while abandoning less productive habitats. Fishing down predators may result in trophic cascades, possibly shifting entire ecosystems into alternate stable states, although alternate states can be maintained by both ecological processes and continued fishing pressure. Conversely, depleting low trophic level groups may affect central-place foragers, although these bottom–up effects rarely appear to impact fish—perhaps because many fish populations have been reduced to the point that they are no longer prey limited. Fisheries provide empirical tests for diversity–stability relations: catch data suggest that more diverse systems recover faster and provide more stable returns than less diverse systems. Fisheries have also provided examples of the tragedy of the commons, as well as counter-examples where common property resources have been managed successfully. We also address two barriers to use of fisheries data to answer ecological questions: differences in terminology for similar concepts and misuse of records of fishery landings (catch data) as a proxy for biomass trends.     

Maternal survival costs in an asocial mammal

Maternal characteristics, social dynamics, and environmental factors can all influence reproduction and survival and shape trade‐offs that might arise between these components of fitness. Short‐lived mammals like the golden‐mantled ground squirrel (GMGS; Callospermophilus lateralis) tend to maximize effort toward current reproduction at the expense of survival but may be complicated by other aspects of the species’ life history and environment. Here, we use 25 years of data (1995–2020) collected from a population of GMGS at the Rocky Mountain Biological Research Laboratory in Gothic, Colorado, to test the effect of several maternal characteristics (e.g., age, experience, and timing of litter emergence), social context (e.g., litter sex ratio and kin density), and environmental context (e.g., date of bare ground and length of vegetative growing season) on survival of reproductive female GMGS using Cox proportional hazard models. Our results indicated that social dynamics (i.e., density) and environmental conditions (i.e., standardized first day of permanent snow cover and length of growing season) explained significant variation in annual maternal survival, while maternal characteristics did not. A higher density of related breeding females and the total number of females (both related and unrelated to the focal mother) were associated with an increase in the mortality hazard. A later standardized date of the first day of permanent snow cover and a shorter growing season both reduced the maternal mortality hazard. Together, our results suggest that factors extrinsic to the squirrels affect maternal survival and thus may also influence local population growth and dynamics in GMGS and other short‐lived, territorial mammal species.     

Personality predicts ectoparasite abundance in an asocial sciurid

Parasitism is a consequence of complex interactions between host, parasite, and their shared environment, and host behavior can influence parasite risk. Animal personality (i.e., consistent behavioral differences that are repeatable across time and context) can influence parasitism with more explorative individuals typically hosting greater parasite loads. Host “sociality” is known to impact parasite risk with more social individuals typically at higher risk of acquiring or transmitting parasites, but other behaviors could also be important. We quantified personality in least chipmunks (Tamias minimus), including repeatability of behavioral traits, and determined whether these personality traits affected ectoparasite prevalence and abundance. We measured personality using standardized hole‐board tests and quantified ectoparasitism of 39 least chipmunks over 2 years at a site in southeastern Manitoba, Canada. We found that activity and exploration were repeatable within the context of the hole‐board test for least chipmunks, which suggests that these traits reflect personality. More exploratory individuals hosted a greater abundance of ectoparasites compared to less exploratory individuals. Our results are consistent with past studies implicating personality as a factor in host–parasite dynamics and suggest that exploration may be an important behavioral correlate of parasite acquisition.     

社会-生态系统恢复力的测量方法综述

恢复力和社会-生态系统研究的理论及实践近年来在西方较为流行,然而经过几十年发展,学术界仍旧没有对恢复力的概念达成一致,相应的测量方法更是多种多样。基于恢复力理论对系统相对稳定状态和边界的假设以及恢复力概念3个阶段的演变和理论的发展,总结了测量恢复力的5种方法,得出恢复力测量的3个发展现状或趋势:阈值和断裂点方法依旧是量化恢复力的基本方法;恢复力测量从关注时间转向空间,关注生态转向社会和社会-生态;复杂学和多学科融合的方法是未来发展的主要方向。     

Wind as an ecological factor

Wind has long been regarded as an important ecological factor in forests owing to the dramatic damage hurricanes can wreak. However, the long-term wind regime of a site also exerts a strong influence on the growth of trees. A relatively large amount is known about the acclimation of trees to wind but less about intra- or interspecific adaption to high winds. In fact, changes resulting from the effect of wind may have a greater effect on the ecology of forests than the more acute effects of destructive stroms. Improved understanding of the mechanical effects of wind is helping foresters manage their plantations and may help us to account better for local and geographical variations in forest ecology.     

Time as an ecological constraint

Conventional approaches to population biology emphasise the roles of climatic conditions, nutrient flow and predation as constraints on population dynamics. We argue here that this focus has obscured the role of time as a crucial constraint on species' abilities to survive in some habitats. Time constraints may be particularly intrusive both for species that live in intensely bonded groups (where the need to devote time to social interaction may ultimately limit the size of group that a species can maintain in a particular habitat) and for taxa that face constraints on the length of the active day. We use a linear programming approach that allows us to specify both how time allocations to different activities are influenced by local environmental and climatic variables and how these in turn limit group size and population density. The linear programming approach identifies the realizable niche space within which a species can maintain coherent groups that are larger than the minimum viable group size (or density). This approach thus allow us to understand better why a given taxon can survive in some habitats but not others, as well as the demographic stress that a population may face. In addition, they also allow us to evaluate the implications of both past and future climate change for a taxon's ability to cope with particular habitats.     

Captive biology of an asocial mustelid; Mustela erminea

Successful captive reproduction, management, and exhibition of ermine (Mustela erminea) are unreported. Wild ermine are solitary and asocial specialist predators of small vertebrates. In captivity they alternate brief periods of frenetic activity with long periods of inactivity, are furtive, and because of interindividual aggressiveness, are managed as solitary animals. These species-specific traits have precluded ermine as an ideal animal for captive management and public exhibition. Here we present observations of gestation and litter size, neonatal reproduction, male reproductive variance, and a possible correlation between diet and female reproductive success. We also describe methods of husbandry and of exhibit animal rotation which enhances visitor viewing of the animal.     

Predicting the spread of an invasive plant: combining experiments and ecological niche model

Rapid evolutionary adjustments to novel environments may contribute to the successful spread of invasive species, and can lead to niche shifts making range dynamics unpredictable. These effects might be intensified by artificial selection in the course of breeding efforts, since many successful plant invaders were deliberately introduced and cultivated as ornamentals. We hypothesized that the invasion success of Buddleja davidii, the ornamental butterfly bush, is facilitated by local adaptation to minimum temperatures and thus, exhibits unpredictable range dynamics. To assess the potential effects of adaptive evolution and artificial selection on the spread of B. davidii, we combined a common garden experiment investigating local adaptation to frost, with ecological niche modelling of the species’ native and invasive ranges. We expected that populations naturalized in sub‐continental climate are less susceptible to frost than populations from oceanic climate, and that the invasive range does not match predictions based on climatic data from the native range. Indeed, we revealed significant variation among invasive B. davidii populations in frost resistance. However, frost hardiness was not related to geographic location or climatic variables of the populations’ home site, suggesting that invasive B. davidii populations are not locally adapted to minimum temperatures. This is in line with results of our ecological niche model that did not detect a niche shift between the species’ native range in China, and its invasive range in Europe and North America. Furthermore, our niche model showed that the potential invasive range of B. davidii is still not completely occupied. Together with the frost resistance data obtained in our experiment, the results indicate that climatic conditions are currently not limiting the further spread of the species in Europe and North America.     

Rapid evolution as an ecological process

Rapid evolution of interspecific interactions (during a timespan of about 100 years) has the potential to be an important influence on the ecological dynamics of communities. However, despite the growing number of examples, rapid evolution is still not a standard working hypothesis for many ecological studies on the dynamics of population structure or the organization of communities. Analysis of rapid evolution as an ecological process has the potential to make evolutionary ecology one of the most central of applied biological sciences.     

Manganese as an ecological factor in salt marshes

The plant available manganese concentration (Mn²⁺) of salt-marsh sediments was compared to that of acidic and neutral soils. The mean soil-manganese concentration was higher in the top 1 cm of salt-marsh soil than in the neutral soil and comparable to that of the acidic soil (0–5 cm). A peak in the soil-manganese concentration in the upper marsh was observed one week after the spring tide but this effect was not evident in the lower marsh. Despite these differences, there was no correlation between mean manganese concentration and position on the marsh.The response to manganese of salt-marsh halophytes was studied by measuring growth and root elongation in a range of Mn²⁺ concentrations with and without sodium chloride. Although there was a differential response to manganese between salt-marsh species, manganese resistance was not related to position on the marsh. Most of the species investigated were tolerant of Mn²⁺ at concentrations higher than normally recommended for plant growth. Moreover a salt-marsh ecotype of Festuca rubra was found to have a higher manganese resistance than an inland ecotype of the same species.When sodium chloride was included in the growth medium, salt-marsh plants had a greatly increased resistance to manganese associated with a reduced uptake. This effect is reflected in the tissue-manganese concentration which was lower than in Deschampsia flexuosa although both groups of plants were exposed to a similar range of Mn²⁺ concentrations. It is concluded that sodium chloride markedly reduces the phytotoxicity of manganese in salt marshes.Nomenclature following Clapham, Tutin & Warburg (1968). Flora of the British Isles.The work was carried out while one of us (C. E. Singer) was in receipt of an SERC studentship, which is gratefully acknowledged.     

Rescue of social motility lost during evolution of Myxococcus xanthus in an asocial environment

Replicate populations of the social bacterium Myxococcus xanthus underwent extensive evolutionary adaptation to an asocial selective environment (liquid batch culture). All 12 populations showed partial or complete loss of their social (S) motility function after 1,000 generations of evolution. Mutations in the pil gene cluster (responsible for type IV pilus biogenesis and function) were found to be at least partially responsible for the loss of S motility in the majority of evolved lines. Restoration (partial or complete) of S motility in the evolved lines by genetic complementation with wild-type pil genes positively affected their fruiting body development and sporulation while negatively affecting their competitive fitness in the asocial regime. This genetic tradeoff indicates that mutations in the pil region were adaptive in the asocial selective environment. This finding was confirmed by experiments showing that defined deletions of pil gene regions conferred a competitive advantage under asocial conditions. Moreover, an amino acid substitution in an evolved genotype was located in a region predicted by genetic complementation analysis to bear an adaptive mutation.     

京津冀城市群城市化强度与生态韧性的耦合协调分析

探索市域尺度与格网尺度下城市化强度与生态韧性之间的作用机制,对提高生态韧性水平、提升城市发展质量、促进城市群可持续发展具有重要意义。以京津冀城市群为研究区,基于2000—2020年土地利用数据、人口密度数据和社会经济数据,尝试构建一套完整的城市化强度与生态韧性指标体系。利用景观安全度模型修正了“规模-密度-形态”生态韧性方法,以市域尺度与格网尺度对比分析为手段,结合耦合协调度模型与Tapio解耦模型,探究二者的时空分异格局及协同演化特征。结果表明：(1)不同尺度下,城市化强度和生态韧性在全局上变化趋势相反且错位关系明显,北京、天津城市化强度高而生态韧性较低;格网尺度下,城市化强度与生态韧性的分布形状存在差异：城市化强度多呈现中心-外围空间分布,生态韧性呈多样化、零散化特征。(2)不同尺度下,城市化强度与生态韧性的耦合协调度逐年增强,北京、天津最高,廊坊、石家庄、衡水、沧州次之,邯郸、邢台相对较低;格网尺度下,局部区域出现特殊现象：北京、天津中部出现初级协调、轻度失调;邯郸、邢台小部分区域达到良好协调。(3)城市化强度与生态韧性的脱钩关系处于良性发展状态,弱脱钩、扩张负脱钩呈上升变化,而...     

Patterns of relatedness and parentage in an asocial, polyandrous striped hyena population

We investigated patterns of relatedness and reproduction in a population of striped hyenas in which individuals are behaviourally solitary but form polyandrous spatial groups consisting of one adult female and multiple adult males. Group-mate males were often close relatives, but were unrelated or distantly related in some cases, indicating that male coalitions are not strictly a result of philopatry or dispersal with cohorts of relatives. Most male-female pairs within spatial groups were unrelated or only distantly related. Considering patterns of relatedness between groups, relatedness was significantly higher among adult males living in non-neighbouring ranges than among neighbouring males. Mean relatedness among male-female dyads was highest for group-mates, but relatedness among non-neighbouring males and females was also significantly higher than among dyads of opposite-sex neighbours. Female-female relatedness also increased significantly with increasing geographic separation. These unusual and unexpected patterns may reflect selection to settle in a nonadjacent manner to reduce inbreeding and/or competition among relatives for resources (both sexes), or mates (males). Finally, resident males fathered the majority of the resident female's cubs, but extra-group paternity was likely in 31% of the cases examined, and multiple paternity was likely in half of the sampled litters.     

Iterated prisoner's dilemma in an asocial world dominated by loners, not by defectors

Cooperation among genetically unrelated individuals can arise when pairs of individuals interact repeatedly in the Prisoner’s Dilemma. However, the conditions allowing the evolution of reciprocal cooperation become extremely restrictive as the size of the cooperative group increases, because defectors can exploit cooperators more efficiently in larger groups. Here we consider three strategies: Tit for Tat, defector, and loner. Loner beats defector in a non-cooperative world. However, a cooperative strategy Tit for Tat (TFT₀) that stops cooperation after the first iteration when there is at least one defector in the group, can invade a world of loners, even in sizable groups, if both the TFT₀ and the defector strategies arise at the same frequency by mutation.     

黄河流域城市生态韧性时空演变及其影响因素

城市作为最复杂的社会生态系统,在经历经济快速积累、城镇化加快推进的同时,面临着资源短缺、环境污染、生物多样性锐减等生态环境挑战,增强城市生态韧性对城市可持续发展至关重要。从韧性的内涵角度评估城市生态韧性水平,探究城市防范内外生态风险能力的时空特征,剖析城市生态韧性差异的影响机制,对实施城市生态文明建设与风险防控具有指导意义。基于"演化韧性"视角从"抵抗-响应-转型"三个能力构建城市生态韧性指标体系,以黄河流域七大城市群59个地级市2011-2020年面板数据为例,运用熵权-逼近理想解排序法(熵权-TOPSIS法)、传统和空间马尔可夫链,在对黄河流域城市生态韧性进行定量测算的基础上,分析其时空特征。最后利用面板分位数回归深入探索黄河流域城市生态韧性影响因素的分段效应,提高对城市生态韧性影响机制的认识。结果表明:(1)2011-2020年,城市生态韧性均值在(0.092,0.125)范围内,呈现缓慢增长态势;离散程度呈倒"U"型变化特征趋势;空间上,城市生态韧性表现为"下游强、上中游弱",城市群内部以省会城市为核心向外围地级市递减,"中心-外围"的分布格局明显。(2)城市生态韧性主要在相邻等级之间进行递次转移,仍未实现跨等级转移,具有"路径依赖"和"自身锁定"特征;地理空间背景在城市生态韧性动态演变过程中发挥着重要作用,表现为"强强联合、低低临近"的集聚效应。(3)影响因素方面,经济发展水平、科技创新对城市生态韧性具有显著促进作用;产业结构对城市生态韧性表现为显著抑制作用,人口密度和环境规制对城市生态韧性不同分位点的影响作用存在显著的异质性。研究结果可为黄河流域全面推进生态保护与建设"韧性城市"提供一定的科学参考和理论依据。     

Zebra finches are bolder in an asocial, rather than social, context

Despite an expanding interest in animal personalities, the influence of social interactions and sex differences on individual differences in behaviour remains poorly understood. Using the social zebra finch (Taeniopygia guttata), we tested for behavioural differences in exploration of a novel environment and objects, between individuals of both sexes in relation to a social context; the presence of three male companions, three female companions or no companion birds. We predicted that the presence of conspecific companions should result in focal birds reacting to novelty by exploring more extensively because the companion birds contribute to anti-predator vigilance behaviour and because social isolation often causes behavioural inhibition in social species. We found that exploratory behaviour of focal individuals was significantly reduced in the presence of conspecific companions, irrespective of the companion's sex. Moreover, we found a weak trend towards females being more exploratory than males, irrespective of the social context. These results demonstrate the importance of considering the social context in animal personality studies and of exploring sex differences in personalities.