暂无摘要。

Climate change affects populations over broad geographic ranges due to spatially autocorrelated abiotic conditions known as the Moran effect. However, populations do not always respond to broad-scale environmental changes synchronously across a landscape. We combined multiple datasets for a retrospective analysis of time-series count data (5-28 annual samples per segment) at 144 stream segments dispersed over nearly 1,000 linear kilometers of range to characterize the population structure and scale of spatial synchrony across the southern native range of a coldwater stream fish (brook trout, Salvelinus fontinalis), which is sensitive to stream temperature and flow variations. Spatial synchrony differed by life stage and geographic region: it was stronger in the juvenile life stage than in the adult life stage and in the northern sub-region than in the southern sub-region. Spatial synchrony of trout populations extended to 100-200 km but was much weaker than that of climate variables such as temperature, precipitation, and stream flow. Early life stage abundance changed over time due to annual variation in summer temperature and winter and spring stream flow conditions. Climate effects on abundance differed between sub-regions and among local populations within sub-regions, indicating multiple cross-scale interactions where climate interacted with local habitat to generate only a modest pattern of population synchrony over space. Overall, our analysis showed higher degrees of response heterogeneity of local populations to climate variation and consequently population asynchrony than previously shown based on analysis of individual, geographically restricted datasets. This response heterogeneity indicates that certain local segments characterized by population asynchrony and resistance to climate variation could represent unique populations of this iconic native coldwater fish that warrant targeted conservation. Advancing the conservation of this species can include actions that identify such priority populations and incorporate them into landscape-level conservation planning. Our approach is applicable to other widespread aquatic species sensitive to climate change.

Hawai\'i is home to \'o\'opu nākea (Awaous stamineus), a culturally significant, endemic, goby that exhibits an amphidromous life cycle characterized by a marine larval stage followed by post-larval recruitment to streams, where they live to become reproductive adults. However, it was recently suggested that their migration to the ocean might not be obligatory, as originally thought. Despite their importance in Hawaiian traditions and the ecology of Hawaiian freshwater ecosystems, we still lack a full understanding of their migratory patterns and life history due to the difficulties in determining the environmental migratory cues that set the timing and location of their migratory paths. This study examined environmental factors, such as mean annual rainfall, streamflow, and water chemistry, to determine if they play a role in whether A. stamineus spend their larval period in the ocean or their entire life cycle in freshwater streams. We sampled A. stamineus (n = 90) from three streams (Kahana, Kahalu\'u, and Waimānalo) on the island of O\'ahu, Hawai\'i that represented the range of hydroclimatic gradient in wet-habitat conditions on the windward side of the island and characterized their migratory pattern using elemental analysis of sagittae, the largest pair of otoliths (calcareous ear structures). Based on otolith strontium:calcium and barium:calcium ratios, we determined if individuals spent their larval period in the ocean or the stream. We found that 100% of individuals displayed clear evidence of marine residence during their larval phase, regardless of the environmental factors the fish experienced. This study highlights the necessity of stream-ocean connectivity for the survival of A. stamineus and emphasizes the importance of stream-mouth conservation and management as it is a critical transition zone in stream-ocean-stream migratory pathways.

Extensive distribution of widespread species and the loss of native species driven by anthropogenic disturbances modify community similarity, resulting in a decrease or increase in community distinctiveness. Data from four basins in the Wannan Mountains, China, were used to evaluate the effects of low-head dams on patterns of fish faunal homogenization and differentiation based on abundance data. We aimed to examine the spatial changes in taxonomic and functional similarities of fish assemblages driven by low-head dams and to examine whether the changes in the similarity of fish assemblages differed between taxonomic and functional components. We found that low-head dams significantly decreased the mean taxonomic similarity but increased the mean functional similarity of fish assemblages in impoundments using abundance-based approaches, suggesting that taxonomic differentiation accompanied functional homogenization in stream fish assemblages. These results show the importance of population abundance in structuring fish faunal homogenization and differentiation at small scales, especially when the major differences among assemblages are in species abundance ranks rather than species identities. Additionally, we also found only a weak positive correlation between changes in mean taxonomic and functional similarities, and partial pairs exhibited considerable variation in patterns of fish faunal homogenization and differentiation for taxonomic and functional components. In conclusion, this study highlighted that the observed taxonomic differentiation of current fish assemblages (short-term phenomenon) is probably an early warning sign of further homogenization in regions where native species are completely predominated and that changes in taxonomic similarity cannot be used to predict changes in functional similarity.

Environmental filtering, spatial factors and species interactions are fundamental ecological mechanisms for community organisation, yet the role of such interactions across different environmental and spatial settings remains mostly unknown. In this study, we investigated fish community organisation scenarios and seasonal species-to-species associations potentially reflecting biotic associations along the Qiupu River (China). Based on a latent variable approach and a tree-based method, we compared the relative contribution of the abiotic environment, spatial covariates and potential species associations for variation in the community structure, and assessed whether different assembly scenarios were modulated by concomitant changes in the interaction network structure of fish communities across seasons. We found that potential species associations might have been underestimated in community-based assessments of stream fish. Omnivore species, since they have more associations with other species, were found to be key components sustaining fish interaction networks across different stream orders. Hence, we suggest that species interactions, such as predation and competition, likely played a key role in community structure. For instance, indices accounting for network structure, such as connectance and nestedness, were strongly correlated with the unexplained residuals from our latent variable approach, thereby re-emphasising that biotic signals, potentially reflecting species interactions, may be of primary importance in determining stream fish communities across seasons. Overall, our findings indicate that interaction network structures are a powerful tool to reflect the contribution of potential species associations to community assembly. From an applied perspective, this study should encourage freshwater ecologists to empirically capture and manage biotic constraints in stream ecosystems across different geographical and environmental settings, especially in the context of the ever-increasing impacts of human-induced local extinction debts and species invasions.

Monitoring long-term changes in aquatic biodiversity requires the effective use of historical data that were collected with different methods and varying levels of effort. Aggregating data into different spatial scales can control for such differences and provide a robust framework for monitoring distribution trends. We used a quantitative, multi-scale assessment to evaluate the potential drivers of distribution change for 60 fish species at three spatial scales, using 503 unique sampling events conducted between 1931 and 2019 in a stream biodiversity hotspot (French Creek, Pennsylvania, U.S.A). Trends delineated at multiple scales demonstrated that only one cyprinid species consistently declined through time. In contrast, several species, particularly centrarchids (bass and sunfish), appeared to increase with time. However, evidence for species\' increases varied among the different spatial scales, and our observations suggest that differences in effort and detection across time periods may contribute to patterns of species increases. There was agreement among scales that agricultural land use, non-native brown trout (Salmo trutta), and anthropogenic barriers did not explain patterns in biodiversity change from the distribution trends in this study. The lack of species declines is likely due to the limited levels of historical impacts in the watershed compared with other locations in the region that experienced more acute pollution bottlenecks. Species increases were most prevalent for sportfish and baitfish species, suggesting that distribution increases were human mediated. Similar multi-scale assessments should provide more robust insight into patterns of biodiversity loss and distribution changes by maximizing the use of historical data.

Animals can play important roles in cycling nutrients [hereafter consumer-driven nutrient dynamics (CND)], but researchers typically simplify animal communities inhabiting dynamic environments into single groups that are tested under relatively static conditions. We propose a conceptual framework and present empirical evidence for CND that considers the potential effects of spatially overlapping animal groups within dynamic ecosystems. Because streams can maintain high biomass of mussels and fish, we were able to evaluate this framework by testing if biogeochemical hotspots generated by stable aggregations of mussels attract fishes. We predicted that spatial overlap between these groups may increase the flux of mineralized nutrients. We quantified how different fish assemblage biomass was between mussel bed reaches and reaches without mussels. We compared fish and mussel biomass at mussel beds to test whether differences in animal biomass mediate their contributions to nutrient cycling through nitrogen and phosphorous excretion. We estimated areal excretion rates for each group by combining biomass estimates with measured excretion rates. Fish biomass was homogeneously distributed, except following a period of low flow when fish were more concentrated at mussel beds. Mussel biomass was consistently an order of magnitude greater than fish biomass and mussel areal excretion rates exceeded fish excretion rates. However, the magnitude of those differences varied spatially and temporally. Mussel excretion stoichiometry varied with changes in assemblage composition, while fish excretion stoichiometry varied little. Biogeochemical hotspots associated with mussels did not generally overlap with fish aggregations, thus, under these conditions, animal processes appear to exert additive ecosystem effects.

To explore the sexual dimorphism of Tanichthys albonubes and its relationship with swimming performances, the morphological characteristics of fins and trunks of male and female T. albonubes were measured and analyzed by using multivariate statistical analysis methods, aiming to explore the difference and its mechanism of swimming performance between male and female under different selected pressure in long-term evolution period and then, providing meaningful information for the protection of T. albonubes. The results showed that body lengths, head depths and breadths, caudal fin areas, distances of snout tip to occipital bone terminus and ventral fin origin to dorsal fin terminus had no significant difference between male and female T. albonubes. The females had significantly higher values in head depths, body breadths, distances of ventral fin origin to dorsal fin origin, snout tip to dorsal fin and to anal fin origin, occipital bone terminus to dorsal fin origin than those in the males. However, head lengths, pectoral fin, dorsal fin, ventral fin and anal fin areas were significantly lower in the females. The results of principal component analysis showed that the contribution rate of the first principal component (PC1) was 74.2%. Obviously loading factors were body lengths, depths and breadths, head lengths, breadths and depths and the distances of each fin mainly reflecting body overall characteristic parameters of T. albonubes. For the second principal component (PC2), the contribution rate was 15.7% and the obviously loading factors were pectoral fin, dorsal fin, ventral fin and anal fin areas which mainly reflected the characteristic parameters of fins. The gender identification of T. albonubes was indistinguishable on PC1, but could be obviously distinguished from PC2. Accuracy rates of sexual discriminant equation which was established by pectoral fin, dorsal fin, ventral fin and anal fin areas and body breadths were 91.8%-92.5%. The results of swimming performance showed that burst swimming speeds (Uburst) had no significant difference between male and female T. albonubes. However, the critical swimming speeds (Ucrit) were significantly decreased in the females than in the males. The findings indicated that the sexual dimorphism of T. albonubes was mainly concentrated on fin characteristics associating with swimming performance. Also having lower Ucrit due to its lower pectoral fins areas than the male, the female T. albonubes had longer hindquarters cadres to ensure high Uburst which facilitated them to avoid predators and other emergency events in volatile streams. Larger fin areas than in the female caused higher Ucirt in the male contributing to chasing female in breeding period and other persistent exercises.
为了解唐鱼两性异形及其与游泳能力关系,检测了性成熟阶段唐鱼躯干部和鱼鳍形态特征以及爆发游泳速度(Uburst)和临界游泳速度(Ucrit)在雌雄之间的差异,旨在从形态适应角度探究长期进化中雌雄唐鱼各自面对选择压力所产生的游泳能力差异及其机制,从而为野生唐鱼保护提供基础数据.结果表明: 雌性唐鱼的体长、头高、头宽、尾鳍面积以及吻端至枕骨后末端、腹鳍起点至背鳍末端等长度均与雄性无显著差异.而体高、体宽、腹鳍起点至背鳍起点等反映腹腔大小的形态参数以及吻端至背鳍起点、吻端至臀鳍起点、枕骨后末端至背鳍起点等反映躯干部大小的形态参数均显示为雌性显著大于雄性,但头长以及胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积均显示为雄性显著大于雌性.对所有数据进行主成分分析,结果显示第1主成分贡献率为74.2%,负载量较大的是体长、头长、头高、体高、头宽、体宽以及各鳍之间距离等主要反映唐鱼躯干整体特征的参数;第2主成分贡献率为15.7%,负载量较大的是胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积等主要反映鱼鳍特征的参数.唐鱼性别在第1主成分上无法区分,但在第2主成分却可以明显区分.根据体宽、胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积等建立的性别判别方程对雌雄判断准确率达到91.8%～92.5%.唐鱼游泳能力测定结果显示,雌性Uburst与雄性无显著差异,但Ucrit显著小于雄性.以上结果表明,雌雄唐鱼两性异形主要集中在与游泳能力相关的鱼鳍特征上.相比雄性,雌性唐鱼虽然胸鳍等鱼鳍面积较小导致其Ucrit小于雄性,却具有更长的躯干部以保证其同样具有较高的爆发游泳能力,从而有利于在流速波动很大的溪流中躲避捕食和进行其他应急活动;相比雌性,雄性唐鱼则具有较大的鱼鳍面积保证其Ucrit高于雌性,以利于日常活动及在繁殖过程中追逐雌性等相对持久性游泳运动.

Conserving native biodiversity in the face of human- and climate-related impacts is a challenging and globally important ecological problem that requires an understanding of spatially connected, organismal-habitat relationships. Globally, a suite of disturbances (e.g., agriculture, urbanization, climate change) degrades habitats and threatens biodiversity. A mosaic approach (in which connected, interacting collections of juxtaposed habitat patches are examined) provides a scientific foundation for addressing many disturbance-related, ecologically based conservation problems. For example, if specific habitat types disproportionately increase biodiversity, these keystones should be incorporated into research and management plans. Our sampling of fish biodiversity and aquatic habitat along ten 3-km sites within the Upper Neosho River subdrainage, KS, from June-August 2013 yielded three generalizable ecological insights. First, specific types of mesohabitat patches (i.e., pool, riffle, run, and glide) were physically distinct and created unique mosaics of mesohabitats that varied across sites. Second, species richness was higher in riffle mesohabitats when mesohabitat size reflected field availability. Furthermore, habitat mosaics that included more riffles had greater habitat diversity and more fish species. Thus, riffles (<5% of sampled area) acted as keystone habitats. Third, additional conceptual development, which we initiate here, can broaden the identification of keystone habitats across ecosystems and further operationalize this concept for research and conservation. Thus, adopting a mosaic approach can increase scientific understanding of organismal-habitat relationships, maintain natural biodiversity, advance spatial ecology, and facilitate effective conservation of native biodiversity in human-altered ecosystems.

Controlling for imperfect detection is important for developing species distribution models (SDMs). Occupancy-detection models based on the time needed to detect a species can be used to address this problem, but this is hindered when times to detection are not known precisely. Here, we extend the time-to-detection model to deal with detections recorded in time intervals and illustrate the method using a case study on stream fish distribution modeling. We collected electrofishing samples of six fish species across a Mediterranean watershed in Northeast Portugal. Based on a Bayesian hierarchical framework, we modeled the probability of water presence in stream channels, and the probability of species occupancy conditional on water presence, in relation to environmental and spatial variables. We also modeled time-to-first detection conditional on occupancy in relation to local factors, using modified interval-censored exponential survival models. Posterior distributions of occupancy probabilities derived from the models were used to produce species distribution maps. Simulations indicated that the modified time-to-detection model provided unbiased parameter estimates despite interval-censoring. There was a tendency for spatial variation in detection rates to be primarily influenced by depth and, to a lesser extent, stream width. Species occupancies were consistently affected by stream order, elevation, and annual precipitation. Bayesian P-values and AUCs indicated that all models had adequate fit and high discrimination ability, respectively. Mapping of predicted occupancy probabilities showed widespread distribution by most species, but uncertainty was generally higher in tributaries and upper reaches. The interval-censored time-to-detection model provides a practical solution to model occupancy-detection when detections are recorded in time intervals. This modeling framework is useful for developing SDMs while controlling for variation in detection rates, as it uses simple data that can be readily collected by field ecologists.