Alien Fishes in Natural Streams: Fish Distribution, Assemblage Structure, and Conservation in the Cosumnes River, California, U.S.A.

The Cosumnes River is the largest stream without a major dam on its mainstem in the Sacramento–San Joaquin drainage, central California, U.S.A. We studied its fishes over a 3-year period to answer the following questions: (1) Was the native fish fauna still present? (2) Why were alien fishes so abundant in a river system with a 'natural' flow regime, which elsewhere has been shown to favor native fishes? (3) Were there assemblages of fishes that reflected environmental differences created by the underlying geology? (4) Were there features of the watershed that consistently favored native fishes or that could be managed to favor native fishes? Of the 25 species collected, 17 were alien species; 14 species (five native) were abundant or widely distributed enough to use in detailed analyses. Of the native species, only rainbow trout, Oncorhynchus mykiss, still occupied much of its native range in headwater streams. Other native species have been extirpated or persisted mainly above barriers to alien invasions. The most widely distributed alien species was redeye bass, Micropterus coosae, previously unknown from the river, whose abundance was associated with low-numbers of native species. Other aliens were found primarily in low-land habitats on the valley floor or foothills. Canonical Correspondence Analysis indicated that both native and alien species located on environmental gradients determined largely by elevation, temperature, flow, and emergent vegetation, but the associations with these variables were not strong. While most alien fishes were found in lowland sections of river flowing through agricultural regions, the general relationships between species abundance and landscape-level variables were weak. Assemblages of fishes were poorly defined mixtures of native and alien species. The strikingly distinct geological regions of the basin no longer supported distinct fish assemblages. Species distributions were highly individualistic, reflecting dynamic patterns of introductions, invasions, and local extinctions, as well as physiological tolerances and life history patterns. Most native fishes are likely to persist in the Cosumnes River only if summer flows are increased and if populations above natural barriers are protected from further invasions by alien species, especially redeye bass. General conclusions from this study include: (1) altered habitats can support native species under some circumstances; (2) new fish assemblages with characteristics of 'natural' communities are likely to develop in invaded systems; (3) restoring flow regimes to favor native fishes may require restoring minimum summer flows as well as high channel-forming flows. However, reversing or even reducing, the impact of the predatory redeye bass, pre-adapted for California streams, is probably not possible.     

Comparison of Leaf Litter Decomposition Rates in Restored and Mature Riparian Forests on the Sacramento River, California

One of the largest riparian restoration projects in the United States is currently taking place in California on the Sacramento River. Nearly 2,000 ha of land adjacent to the river channel have been revegetated with native riparian species in an effort to reestablish riparian forests. The objective of this study was to compare leaf litter decomposition rates in restored riparian forests to those in mature, naturally established riparian forests, in order to monitor the development of this ecosystem function in restored forests. Leaf litter decomposition rates were measured over 1 year in six restored riparian forests (4, 7, and 9 years old) and two mature remnant riparian forests (>50 years old), in order to test two hypotheses: (1) decomposition rates of restored and mature forests are significantly different and (2) decomposition rates in the chronosequence of restored forests are moving along a trajectory, approaching the decomposition rates characteristic of mature forests as they age. Statistical analyses revealed no significant differences in annual decay rates among the four different forest ages and no trajectory among leaf litter decomposition rates in restored forests. These results suggest that a functionally equivalent process of leaf litter decomposition occurs in both restored and naturally established forests and show promise for the efficiency of nutrient cycling processes in these restored forests.     

Fish Communities and Their Associations with Environmental Variables, Lower San Joaquin River Drainage, California

Twenty sites in the lower San Joaquin River drainage, California, were sampled from 1993 to 1995 to characterize fish communities and their associations with measures of water quality and habitat quality. The feasibility of developing an Index of Biotic Integrity was assessed by evaluating four fish community metrics, including percentages of native fish, omnivorous fish, fish intolerant of environmental degradation, and fish with external anomalies. Of the thirty-one taxa of fish captured during the study, only 10 taxa were native to the drainage. Multivariate analyses of percentage data identified four site groups characterized by different groups of species. The distributions of fish species were related to specific conductance, gradient, and mean depth; however, specific conductance acted as a surrogate variable for a large group of correlated variables. Two of the fish community metrics – percentage of introduced fish and percentage of intolerant fish – appeared to be responsive to environmental quality but the responses of the other two metrics – percentage of omnivorous fish and percentage of fish with anomalies – were less direct. The conclusion of the study is that fish communities are responsive to environmental conditions, including conditions associated with human-caused disturbances, particularly agriculture and water development. The results suggest that changes in water management and water quality could result in changes in species distributions. Balancing the costs and benefits of such changes poses a considerable challenge to resource managers.     

Variation in Condition Factor and Growth in Young-of-Year Fishes in Floodplain and Riverine Habitats of the Cosumnes River, California

Condition factors and growth rates of postlarval (young-of-year) fishes in a Central California river were compared in order to determine the relative importance of floodplain and riverine habitats for rearing. Sampling took place between April and June of 2001 and 2002 in the lower Cosumnes River and its floodplain. Sacramento splittail showed higher condition and length increment in floodplain habitats of than in riverine habitats. Sacramento suckers showed differences in condition between sites, but suckers from the floodplain had lower weight increments than those from the river. The weight increment in Sacramento splittail was not significantly different between habitats. In addition, two alien species, common carp and golden shiner, had similar condition factors and growth rates. This study shows the usefulness of condition factor and growth rate in evaluating the importance of different habitats for early life history stages of fishes.     

黄河干流鱼类群落特征及其历史变化

为了解黄河干流鱼类群落现状及其历史变化,于2008年春季(5-6月)和秋季(9-11月)开展了黄河干流鱼类调查。共记录到鱼类54种,隶属于7目13科43属,其中该流域特有种4种。种类组成以鲤形目为主,占总数的68.5%。上游物种少,群落较为简单,中游和下游物种丰富,群落较为复杂并且较相似,种数自上游至下游逐渐增加。黄河鱼类在洄游、摄食、繁殖及栖息习性等方面呈现多样化特征。调查河段渔获物组成虽存在差异,但都以黄颡鱼属(Pelteobagrus spp.)、鲇(Silurus asotus)、鲫(Carassius auratus)以及鮈亚科等小型鱼类为主,小型化现象明显。对比历史资料分析显示,黄河鱼类物种多样性和资源量均呈明显下降趋势,特有种鱼类退化尤为显著,推测水资源过度开发、大量水工建筑、水体污染以及不合理利用等人为因素是导致变化的主要原因。     

Recent,small beginnings: genetic analysis suggests Catostomus rimiculus (Klamath smallscale sucker) in the Smith River,California, are introduced

Identification of introduced species can be important to understanding ecological systems and meeting conservation and management goals, but the process can be surprisingly challenging. The Klamath smallscale sucker Catostomus rimiculus seems likely to be native to the Smith River because the drainage separates two basins believed to be within the fish's native range, the Rogue and Klamath rivers. Further, C. rimiculus is broadly distributed in the Smith River, and the indigenous Dee-ni’ People of the Smith River have a unique word for sucker. Nonetheless, a historical survey of fishes that described C. rimiculus from the Rogue and Klamath rivers did not include C. rimiculus among the fishes of the Smith River. To determine whether the genetic structure of the Smith River C. rimiculus reflects expectations for a native sucker population, the authors of this study examined variation in microsatellite and mitochondrial genetic markers from the Smith River and surrounding drainages. The genetic analyses revealed a pattern consistent with extreme founder effects in Smith River C. rimiculus, as would be expected from a single introduction of six or fewer effective individuals. The sharing of a high-frequency haplotype between the Smith River and Klamath River that is not detected in the Rogue River suggests the Klamath River as the likely source for the introduction. The findings highlight that local-scale introductions can be easily overlooked because the newly established populations can appear to be parts of contiguous natural distributions.     

Age, Growth, and Gonadal Characteristics of Adult Bighead Carp, Hypophthalmichthys nobilis, in the Lower Missouri River

Bighead carp were introduced into Arkansas in 1973 to improve water clarity in production ponds. Bighead carp subsequently escaped aquaculture facilities in the early 1980's and dispersed into the Mississippi and Missouri rivers. The first documentation of bighead carp reproduction in the Mississippi River system was in 1989. The population has increased in the Missouri River as is evident in their increased proportion in the commercial harvest since 1990. The effect of this exotic planktivore on native ecosystems of the U.S. has not been examined. Basic biological data on bighead carp Hypophthalmichthys nobilis in the Missouri River are needed to predict potential ecological problems and provide a foundation for manipulative studies. The objectives of this study were to assess age, growth, and gonadal characteristics of bighead carp in the Missouri River. Adult bighead carp in our sample varied from age 3 to age 7 and length varied from 475 to 1050mm. There was a large variation in length at age, and overall bighead carp exhibited fast growth. For example, mean back-calculated length at age 3 was 556mm. The sample was dominated by bighead carp from the 1994 year class. There was no difference in gonad development (i.e., gonadal somatic index, egg diameter) between winter and spring samples. Length of male bighead carp and GSI were not significantly correlated; however, females exhibited a positive linear relationship between length and GSI. In each ovary, egg diameter frequencies exhibited a bimodal distribution, indicating protracted spawning. Mean fecundity was 226213, with a maximum fecundity of 769964. Bighead carp in the Missouri River have similar life history characteristics to Asian and European populations. They have become well established in the Missouri River and it is likely that dispersal and population density will increase.     

Exotic plant species of the St Lawrence River wetlands: a spatial and historical analysis

Aim To evaluate the importance (number of species, plant cover) of the exotic flora in seven well‐defined sectors of one of the most important transportation waterways in North America. To determine the impact of exotic species on wetland plant diversity and reconstruct the spread of some invasive species. Location St Lawrence River, southern Québec. Methods The exotic flora (vascular plants) of wetlands bordering the St Lawrence River was studied using 713 sampling stations (25 m²) along a 560‐km long corridor. Results Exotic species represent 13.7% of the vascular flora of the St Lawrence wetlands. The relative plant cover occupied by exotic species is high in some of the fluvial sectors (42–44%), but low (6–10%) in the estuarine sectors. Wetlands (marshes) surrounding islands were particularly susceptible to invasion by exotic plants. Historical, abiotic and landscape factors may explain the differences observed between sites. Purple loosestrife (Lythrum salicaria L.) is the most common exotic species of the St Lawrence wetlands, but other species, namely flowering‐rush (Butomus umbellatus L.) and reed canary grass (Phalaris arundinacea L.) are much more invasive. There is no linear relationship between the exotic species cover and the diversity of wetland plants; low diversity sites can be dominated by either exotic or native plant species. In the other sites, exotic species generally have little impact on plant communities and can contribute to increase diversity. Common reed (Phragmites australis (Cav.) Trin. ex Steudel) and reed canary grass, both considered as exotic species in this study, clearly have a stronger impact on plant diversity than flowering‐rush and purple loosestrife. Main conclusions This study shows that the global impact of an invader cannot be adequately evaluated with only a few highly invaded sites. While nationwide strategies have been developed to control exotic species, large surveys are essential to adapt them to regional particularities.     

Abundance Patterns of Landbirds in Restored and Remnant Riparian Forests on the Sacramento River, California, U.S.A.

Riparian vegetation along the Sacramento River—California's largest river—has been almost entirely lost, and several wildlife species have been extirpated or have declined as a result. Large-scale restoration efforts are focusing on revegetating the land with native plants. To evaluate restoration success, we conducted surveys of landbirds on revegetated and remnant riparian plots from 1993 to 2003. Our objectives were to estimate population trends of landbirds, compare abundance patterns over time between revegetated and remnant riparian forests, and evaluate abundance in relation to restoration age. Of the 20 species examined, 11 were increasing, 1 was decreasing (Lazuli Bunting [ Passerina amoena ]), and 8 showed no trend. The negative trend for Lazuli Bunting is consistent with information on poor reproductive success and with Breeding Bird Survey results. There was no apparent guild association common to species with increasing trends. Nine species were increasing on revegetated and remnant plots, four were increasing on revegetated plots only, three were increasing on remnant plots only, the Lazuli Bunting was decreasing on both, and three species were stable on both. Although many species were increasing at a faster rate on revegetated plots, their abundance did not reach that of the remnant plots. For revegetated plots, "year since planting" was a strong predictor of abundance trends for 13 species: positive for 12, negative for 1. Our study shows that restoration activities along the Sacramento River are successfully providing habitat for a diverse community of landbirds and that results from bird monitoring provide a meaningful way to evaluate restoration success.     

Fish Communities of the Sacramento River Basin: Implications for Conservation of Native Fishes in the Central Valley, California

The associations of resident fish communities with environmental variables and stream condition were evaluated at representative sites within the Sacramento River Basin, California between 1996 and 1998 using multivariate ordination techniques and by calculating six fish community metrics. In addition, the results of the current study were compared with recent studies in the San Joaquin River drainage to provide a wider perspective of the condition of resident fish communities in the Central Valley of California as a whole. Within the Sacramento drainage, species distributions were correlated with elevational and substrate size gradients; however, the elevation of a sampling site was correlated with a suite of water-quality and habitat variables that are indicative of land use effects on physio-chemical stream parameters. Four fish community metrics – percentage of native fish, percentage of intolerant fish, number of tolerant species, and percentage of fish with external anomalies – were responsive to environmental quality. Comparisons between the current study and recent studies in the San Joaquin River drainage suggested that differences in water-management practices may have significant effects on native species fish community structure. Additionally, the results of the current study suggest that index of biotic integrity-type indices can be developed for the Sacramento River Basin and possibly the entire Central Valley, California. The protection of native fish communities in the Central Valley and other arid environments continues to be a conflict between human needs for water resources and the requirements of aquatic ecosystems; preservation of these ecosystems will require innovative management strategies.     

上海苏州河治理中鱼类多样性及群落结构变化

为了评估近20年来上海苏州河环境综合整治过程中鱼类多样性的变化状况, 本文于2019年6月(夏季)和9月(秋季)对苏州河13个断面的鱼类样本进行了采集, 对鱼类多样性和群落结构作了分析。结果显示, 2次采集共获得鱼类样本10,102号, 隶属于8目15科37属45种。夏季和秋季, 上游8个断面的鱼类均为36种, 下游5个断面则为12种和15种。从上游到下游, Shannon-Wiener多样性指数(H')、Margalef种类丰富度指数(D)和Simpson优势度指数(C)总体呈逐渐降低的趋势。相对重要性指数(IRI)显示, 夏秋两季上游断面共同的优势种为似鳊(Pseudobrama simoni), 下游为鲫(Carassius auratus)和泥鳅(Misgurnus anguillicaudatus)。丰度生物量曲线表明, 全河段鱼类群落结构总体上并不稳定, 特别是夏季的下游河段。Cluster聚类和非参数多维标度排序分析可明显将鱼类群落分为上游群组(I)与下游群组(II), 似鳊、泥鳅、鲫、光泽黄颡鱼(Pelteobagrus nitidus)和兴凯鱊(Acheilognathus chankaensis)等是造成群组间差异性的主要分歧种。与2001年的43种、2006年的28种相比, 本次调查的物种数出现了明显回升, 特别是下游河段。这种上游鱼类向下游迁移的趋势, 预示着下游中心城区与上游郊区河段的水质差别正在缩小, 水生态系统恢复迹象明显。本文认为, 上下游之间鱼类群落结构差异的缩小以及翘嘴鲌(Culter alburnus)、红鳍原鲌(Cultrichthys erythropterus)、棒花鱼(Abbottina rivularis)、子陵吻虾虎鱼(Rhinogobius giurinus)等在下游河段的出现, 可作为苏州河综合整治效果的重要生态标志。     

Spatial and temporal variation of fish communities in secondary channels of the San Juan River, New Mexico and Utah

Spatial and temporal variation of fish communities in four secondary channels of the San Juan River between Shiprock, NM and Bluff, UT were investigated from July 1993 through November 1994. Fish abundance and habitat availability data were collected to determine if physical attributes of sites influenced spatial and temporal variation in their fish communities. Stability of habitat was shown to positively influence the stability of the fish community. Analysis of variance revealed greater spatial than temporal variation in the abundance of red shiner, Cyprinella lutrensis, fathead minnow, Pimephales promelas, and flannelmouth sucker Catostomus latipinnis, while speckled dace, Rhinichthys osculus showed greater temporal variation. Ordination, using detrended correspondence analysis, revealed variation in fish communities by site, date, and sample year. Spatial variation was greatest during low-flow periods when the greatest differences in habitat among the four sites occurred. Spring runoff had the greatest temporal effect on the fish communities in secondary channels and appeared to reset the communities by displacing those species that were less resistant to increased current velocities. This annual event may help maintain native fish species adapted to these conditions in the San Juan River while moderating the abundance of nonnative fish species.     

Marine range shifts and species introductions: comparative spread rates and community impacts

Aim Shifts in species ranges are a predicted and realized effect of global climate change; however, few studies have addressed the rates and consequence of such shifts, particularly in marine systems. Given ecological similarities between shifting and introduced species, we examined how our understanding of range shifts may be informed by the more established study of non‐native species introductions. Location Marine systems world‐wide. Methods Database and citation searches were used to identify 129 marine species experiencing range shifts and to determine spread rates and impacts on recipient communities. Analyses of spread rates were based on studies for which post‐establishment spread was reported in linear distance. The sizes of the effects of community impacts of shifting species were compared with those of functionally similar introduced species having ecologically similar impacts. Results Our review and meta‐analyses revealed that: (1) 75% of the range shifts found through the database search were in the poleward direction, consistent with climate change scenarios, (2) spread rates of range shifts were lower than those of introductions, (3) shifting species spread over an order of magnitude faster in marine than in terrestrial systems, and (4) directions of community effects were largely negative and magnitudes were often similar for shifters and introduced species; however, this comparison was limited by few data for range‐shifting species. Main conclusions Although marine range shifts are likely to proceed more slowly than marine introductions, the community‐level effects could be as great, and in the same direction, as those of introduced species. Because it is well‐established that introduced species are a primary threat to global biodiversity, it follows that, just like introductions, range shifts have the potential to seriously affect biological systems. In addition, given that ranges shift faster in marine than terrestrial environments, marine communities might be affected faster than terrestrial ones as species shift with climate change. Regardless of habitat, consideration of range shifts in the context of invasion biology can improve our understanding of what to expect from climate change‐driven shifts as well as provide tools for formal assessment of risks to community structure and function.     

Small founding number and low genetic diversity in an introduced species exhibiting limited invasion success (speckled dace, Rhinichthys osculus)

Molecular evaluations of successful invaders are common, however studies of introduced species that have had limited invasion success, or have died out completely, are rare. We studied an introduced population of speckled dace (Rhinichthys osculus) from northern California, USA that has rapidly increased in abundance but remained restricted to a 25-km stretch of river since its introduction in the mid-1980s. Field and laboratory analyses indicate that invasion success of speckled dace is constrained by the combined effects of multiple predators. The role of bottleneck effects associated with the introduction has not been studied. We assayed variation in seven microsatellite loci and one mitochondrial DNA gene in the introduced population and nine putative source populations to identify the source population and evaluate bottleneck effects. The Trinity River system was supported as the source owing to its genetic similarity and geographic proximity to the introduced population. Consistent with a bottleneck, the introduced population exhibited reduced allelic and haplotype richness in comparison to source populations. Estimates of the genetically effective number of individuals founding the introduced population using nuclear coalescent analyses and a mitochondrial simulation procedure were highly concordant in suggesting that the initial colonizing group was comprised of about 10 individuals. A bottleneck effect in an exotic species exhibiting limited invasion success has rarely been documented and thus introduction of speckled dace represents an important model system for future investigation. Establishing a relationship between genetic diversity and factors limiting invasion success in this system (e.g., predator avoidance) will help determine the extent to which genetic diversity loss has constrained invasion success in speckled dace.     

The Genus Uroleucon Mordvilko (Insecta, Aphidoidea) in South America, with a key and descriptions of four new species

Uroleucon is one of only two genera of Aphidinae to have undergone significant speciation in South America, with a group of about 14 endemic, morphologically similar species feeding on native Compositae, especially Baccharis . Multivariate morphometrics (canonical variates analysis, CVA) was used to discriminate between these species and compare them with the North American subgenus Lambersius , in which most of them have hitherto been placed. It is concluded that they probably form a separate monophyletic group. Four new species are described in this group— brevisiphon, essigi, petrohuense and pseudomuennosum— and five names are placed in synonymy. Of the other species of Uroleucon in South America, U. lizerianum is widespread and feeds on many species of native and introduced Compositae; it is morphometrically inseparable from the North American species U. ambrosiae and is probably an introduced form of that species, but has consistently fewer secondary rhinaria. A key is provided to the 19 available species of Uroleucon recorded from South America.     

Length-weight relationships of six fish species from the Xiangjiang River in Guangxi region,China

This study aimed to estimate the parameters of length-weight relationships (LWRs) for six freshwater fish species that inhabit in the Xiangjiang River of Guangxi region, China. The specimens were sampled in April, July, and October 2014 and in January 2015 using electrofishing (CWB-2000P, China; 12 V import, 250 V export) and traps (mesh size 8.5 mm; length 200 m) at five sampling sites. For each sampling site, a trap was settled on one nearshore zone of the river for 24 hr, and the electrofishing was applied within 30 min from downstream to upstream with 200 m long. Standard length was measured (be accurate to 0.1 cm) and total weight determined (be accurate to 0.1 g) after preservation in formaldehyde (10%). The values for the parameter b of the length-weight relationships were estimated together with the coefficient of determination scores. In addition, this study provides a new tentative LWRs for the six species.     

Assessing the diversity and distribution of Cephalothrix species (Nemertea: Palaeonemertea) in European waters by comparing different species delimitation methods

Soft‐bodied marine taxa, like ribbon worms (Nemertea), often lack clear diagnostic morphological characters impeding traditional species delimitation. Therefore, recent studies concentrated on molecular genetic methods to solve taxonomic issues. Different delimitation methods were employed to explore species boundaries and the presence of cryptic species. However, the performance of the different delimitation methods needs to be tested. A particularly promising nemertean genus in this regard is the palaeonemertean genus Cephalothrix that is commonly found in European waters. In order to gain information on the number and distribution of European cephalotrichids and to test different tree‐based and non‐tree‐based delimitation methods, we analyzed a dataset comprising the barcoding region of the mitochondrial cytochrome c oxidase subunit I (COI) of 215 European Cephalothrix specimens, of which 78 were collected for this study. Our results show the presence of 12–13 European lineages of which several can be assigned to known European species. Analyzing a second dataset comprising 74 additional sequences from the Pacific and the Atlantic Oceans helped identify some of the unassigned European specimens. One resulting clade seems to represent a non‐native introduced Cephalothrix species, while another has never been recorded from Europe before. In our analysis, especially the tree‐based methods and the phylogenetic analysis proved to be a useful tool when delimiting species. It remains unclear whether the different identified clades result from cryptic speciation or from a high genetic variability of the COI gene.     

Impact of Oreochromis niloticus (Linnaeus, 1758) (Pisces: Cichlidae) invasion on taxonomic and functional diversity of native fish species in the upper Kabompo River,northwest of Zambia

Invasive alien species have been revealed to drastically alter the structure of native communities; however, there is scarce information on whether taxonomic and functional spaces occupied by native species are equally filled by exotic species. We investigated the diversity of native species to understand the impact of exotic Oreochromis niloticus in the upper Kabompo River, northwest of Zambia using taxonomic and functional diversity indices. To achieve this, two tests were performed (Test 1, compared natives in invaded and uninvaded sections; Test 2, compared natives in invaded section). A total of 17 species were collected for functional diversity computation, out of which fourteen (14) functional trait measurements linked to feeding, locomotion, and life history strategy were taken. Findings revealed that taxonomic and functional diversity values changed with invasion in both tests. Taxonomic diversity was 15% more in invaded than uninvaded sections in Test 1 and was not consistent across sampling points of invaded section in Test 2. Invaded areas were taxonomically less diverse, but functionally diverse in both tests. The analysis of similarity and nonmetric multidimensional scaling revealed no difference in Bray–Curtis similarity assemblages in both tests. Our findings revealed that exotic species more often occupy unfilled gaps in the communities often occupied by the native species; this is achieved by occupying functional spaces. Overall, changes in taxonomic and functional diversity of native species documented here partially confirmed impacts of O. niloticus invasion. Therefore, we recommend a multifaceted approach to assess cumulative impacts of invasion on native species.     

新薛河底栖动物物种多样性与功能多样性研究

研究功能多样性与物种多样性关系及其随环境梯度的变化规律,有助于理解生物在群落中的共存机制;然而,二者间关系的研究在淡水生态学中尚鲜见报道。通过对新薛河典型河段(A缓流河段、B断流河段、C有机污染河段、D对照河段、E人为干扰河段)底栖动物季节性调查,就物种多样性和功能多样性时空动态及关系进行了研究。结果表明:在空间序列上,物种多样性指数在B河段均最低,表明间歇性断流对物种多样性影响重大。功能丰富度在D河段最高,A河段最低;功能均匀度在A河段高于其他河段;功能分离度在A、B河段最高,D河段最低。在时间序列上,物种丰富度和Shannon指数均值在10月份最低,4月份最高;均匀度指数在12月份最低,10月份最高。3个功能多样性指数于各季节间差异显著、相互独立,主要受水文条件和底栖动物生活史影响。相关分析表明,功能多样性指数间无显著相关性;功能丰富度同物种丰富度和Shannon指数相关显著,功能均匀度同物种均匀度相关显著。逐步回归分析发现,功能丰富度受物种丰富度和Shannon指数影响显著,功能均匀度受物种均匀度影响显著;功能多样性和物种多样性指数间拟合度总体不高。研究结果进一步表明:相对物种多样性,功能多样性对生境梯度变化响应更加全面。