鸭绿江口湿地鸻鹬类停歇地的生物生态研究

鸭绿江口湿地是鸻鹬类在东亚一澳大利亚北迁路线上的最重要停歇地,潮间带上的双壳类、腹足类、多毛类等底栖动物为鸻鹬类提供了能量保障.2010年3月-2011年6月对鸭绿江口潮间带的生物生态进行了调查研究.研究结果表明,生物群落结构相对简单,主要以双壳类、腹足类和多毛类为主,优势种演替明显,系统具有低多样性低密度的特点.鸻鹬类能量补充来源相对匮乏,饵料生物量的更新速度较慢,所提供的能值也相对较低,江户明樱蛤、青蛤(幼体)和长吻沙蚕是鸻鹬类的主要食物来源.鸻鹬类主要集中在低潮带下区觅食,在北迁高峰期对低潮带下区饵料生物影响较显著,尤其对江户明樱蛤丰度影响最明显.泥螺作为优势种,生态位最宽,分布于整个调查断面和潮带,但因体表分泌一种毒性粘液而不被鸻鹬类取食.饵料生物的种群补充能力较强,在鸻鹬类迁徙高峰期之后,饵料丰度和生物量又会恢复到正常水平.虽然目前人类对鸻鹬类的威胁显现较小,但使人类一生态系统一滨鸟之间持续和谐统一,必须综合考量鸭绿江口湿地包括人类在内的生态系统各关键组分之间的生态关联,兼顾生态系统的完整性和人类社会经济发展的可持续性.     

Interim Response of Wading Birds (Pelecaniformes and Ciconiiformes) and Waterfowl (Anseriformes) to the Kissimmee River Restoration Project,Florida, U.S.A

Success of the Kissimmee River Restoration Project will be evaluated in part by monitoring populations of wading birds (Pelecaniformes and Ciconiiformes) and waterfowl (Anseriformes). These two waterbird guilds were integral components of the pre‐channelization river–floodplain ecosystem, and both declined substantially following channelization. Restoration is expected to attract wading birds and waterfowl by reintroducing naturally fluctuating water levels, seasonal hydroperiods, and historic vegetation communities. Post‐construction aerial surveys (November 2001 to May 2008) within the Phase I restoration area indicate that the abundance and species richness of both wading birds and waterfowl have shown a positive restoration response thus far. Dry season abundance of aquatic wading birds and waterfowl has exceeded restoration expectations (≥30.6 birds/km² and ≥3.9 birds/km², respectively) each year since the completion of restoration Phase I in 2001. While there has been a significant positive restoration effect on waterfowl abundance, waterfowl species richness (n = 6) has not yet reached the restoration expectation of ≥13 species. Abundance of the terrestrial cattle egret (Bubulcus ibis), which increased dramatically after the majority of floodplain wetlands were converted to cattle pastures in the channelized system, has shown a significant negative response to restoration. It is anticipated that completion of the remaining phases of restoration (II/III), and implementation of the Kissimmee River Headwaters Revitalization water regulation schedule by 2019, will further increase and improve habitat for wading birds and waterfowl by reestablishing floodplain hydrology that more closely mimics historical conditions.     

Spatial heterogeneity in recruitment of larval trematodes to snail intermediate hosts

Spatial variation in parasitism is commonly observed in intermediate host populations. However, the factors that determine the causes of this variation remain unclear. Increasing evidence has suggested that spatial heterogeneity in parasitism among intermediate hosts may result from variation in recruitment processes initiated by definitive hosts. I studied the perching and habitat use patterns of wading birds, the definitive hosts in this system, and its consequences for the recruitment of parasites in snail intermediate hosts. Populations of the mangrove snail, Cerithidea scalariformis, collected from mangrove swamps on the east coast of central Florida are parasitized by a diverse community of trematode parasites. These parasites are transmitted from wading birds, which frequently perch on dead mangrove trees. I tested the hypothesis that mangrove perches act as transmission foci for trematode infections of C. scalariformis and that the spatial variation of parasitism frequently observed in this system is likely to emanate from the distribution of wading birds. On this fine spatial scale, definitive host behaviors, responding to a habitat variable, influenced the distribution, abundance and species composition of parasite recruitment to snails. This causal chain of events is supported by regressions between perch density, bird abundance, bird dropping density and ultimately parasite prevalence in snails. Variation between prevalence of parasites in free-ranging snails versus caged snails shows that while avian definitive hosts initiate spatial patterns of parasitism in snails through their perching behaviors, these patterns may be modified by the movement of snail hosts. Snail movement could disperse their associated parasite populations within the marsh, which may potentially homogenize or further increase parasite patchiness initiated by definitive hosts.     

Design of the dike-pond system in the littoral zone of a tributary in the Three Gorges Reservoir, China

The Three Gorges Dam is the greatest water control project in the world with the largest fresh water littoral zone. Emergence of the littoral zone during the growing season provides some plants with the opportunity to complete their growth cycle, but the fluctuating water level also brings about some environmental problems, such as soil erosion, water pollution, and biodiversity reduction. A series of cascading terraced ponds located in the littoral zone of a secondary branch of the Yangtze River at Laotudi Bay was designed to be a dike-pond system for resolving the environmental problems of this special littoral zone while also making use of resources in an eco-friendly manner. The design of the dike-pond system is described in detail in this article, and some monitoring protocols are recommended for evaluating the environmental benefits of the system. The economic value of the dike-ponds was estimated to be about ¥125,986. Due to the ecological management mode adopted, 14 species of wild aquatic plants and 6 species of wading birds were found in the dike-pond system, in contrast to 9 species of wild aquatic plants and 3 species of wading birds in a comparable conventional farming area. It is hoped that dike-pond ecological engineering will be instrumental in reducing water pollution and increasing biodiversity in the littoral zone of the Three Gorges Reservoir.     

Diversification in a fluctuating island setting: rapid radiation of Ohomopterus ground beetles in the Japanese Islands

The Japanese Islands have been largely isolated from the East Asian mainland since the Early Pleistocene, allowing the diversification of endemic lineages. Here, we explore speciation rates and historical biogeography of the ground beetles of the subgenus Ohomopterus (genus Carabus) based on nuclear and mitochondrial gene sequences. Ohomopterus diverged into 15 species during the Pleistocene. The speciation rate was 1.92 Ma(-1) and was particularly fast (2.37 Ma(-1)) in a group with highly divergent genitalia. Speciation occurred almost solely within Honshu, the largest island with complex geography. Species diversity is highest in central Honshu, where closely related species occur parapatrically and different-sized species co-occur. Range expansion of some species in the past has resulted in such species assemblages. Introgressive hybridization, at least for mitochondrial DNA, has occurred repeatedly between species in contact, but has not greatly disturbed species distinctness. Small-island populations of some species were separated from main-island populations only after the last glacial (or the last interglacial) period, indicating that island isolation had little role in speciation. Thus, the speciation and formation of the Ohomopterus assemblage occurred despite frequent opportunities for secondary contact and hybridization and the lack of persistent isolation. This radiation was achieved without substantial ecological differentiation, but with marked differentiation in mechanical agents of reproductive isolation (body size and genital morphology).     

The time of divergence between the two species of uacari monkeys: Cacajao calvus and Cacajao melanocephalus

It has been suggested in the literature that primates of the genus Cacajao have been restricted to flooded-forest habitats of western Amazonia since their split from the Chiropotes line in the Tertiary. It has been proposed further that the differentiation of the two species of this genus, Cacajao melanocephalus and Cacajao calvus, occurred during the Pleistocene period as a result of the fragmentation of the Amazon forest and the isolation of populations in these forest fragments or refuges. However, recent evidence has shown that at least C. melanocephalus is not dependent on flooded-forest habitats, and molecular analysis of mitochondrial DNA shows that the two species had already differentiated during the Pliocene, thus Pleistocene glaciations do not explain the speciation in Cacajao. Considering that C. melanocephalus and its closest relative, Chiropotes, inhabit terra firme forests, it is suggested that preference for flooded-forest habitats may be an apomorphy in C. calvus.     

Genetic divergence and migration patterns in a North American passerine bird: implications for evolution and conservation

Like many other migratory birds, the black-throated blue warbler (Dendroica caerulescens) shows pronounced differences in migratory behaviour and other traits between populations: birds in the southern part of the breeding range have darker plumage and migrate to the eastern Caribbean during the winter, whereas those in the north have lighter plumage and migrate to the western Caribbean. We examined the phylogeography of this species, using samples collected from northern and southern populations, to determine whether differentiation between these populations dates to the Pleistocene or earlier, or whether differences in plumage and migratory behaviour have arisen more recently. We analysed variation at 369 bp of the mitochondrial control region domain I and also at seven nuclear microsatellites. Analyses revealed considerable genetic variation, but the vast majority of this variation was found within rather than between populations, and there was little differentiation between northern and southern populations. Phylogeographic analyses revealed a very shallow phylogenetic tree, a star-like haplotype network, and a unimodal mismatch distribution, all indicative of a recent range expansion from a single refugium. Coalescent modelling approaches also indicated a recent common ancestor for the entire group of birds analysed, no split between northern and southern populations, and high levels of gene flow. These results show that Pleistocene or earlier events have played little role in creating differences between northern and southern populations, suggesting that migratory and other differences between populations have arisen very recently. The implications of these results for the evolution of migration and defining taxonomic groups for conservation efforts are discussed.     

Out of America: ancient DNA evidence for a new world origin of late quaternary woolly mammoths

Although the iconic mammoth of the Late Pleistocene, the woolly mammoth (Mammuthus primigenius), has traditionally been regarded as the end point of a single anagenetically evolving lineage, recent paleontological and molecular studies have shown that successive allopatric speciation events must have occurred within Pleistocene Mammuthus in Asia, with subsequent expansion and hybridization between nominal taxa [1, 2]. However, the role of North American mammoth populations in these events has not been adequately explored from an ancient-DNA standpoint. To undertake this task, we analyzed mtDNA from a large data set consisting of mammoth samples from across Holarctica (n = 160) and representing most of radiocarbon time. Our evidence shows that, during the terminal Pleistocene, haplotypes originating in and characteristic of New World populations replaced or succeeded those endemic to Asia and western Beringia. Also, during the Last Glacial Maximum, mammoth populations do not appear to have suffered an overall decline in diversity, despite differing responses on either side of the Bering land bridge. In summary, the "Out-of-America" hypothesis holds that the dispersal of North American woolly mammoths into other parts of Holarctica created major phylogeographic structuring within Mammuthus primigenius populations, shaping the last phase of their evolutionary history before their demise.     

Pleistocene glaciation explains the disjunct distribution of the Chestnut‐vented Nuthatch (Aves,Sittidae)

Pleistocene climatic oscillations have played an important role in shaping many species’ current distributions. In recent years, there has been increasing interest in studying the effects of glacial periods on East Asian birds. Integrated approaches allow us to study past distribution range changes due to Pleistocene glaciation, and how these changes have affected current population genetic structure, especially for species with unusual distribution patterns. The Wuyi disjunction is the disjunct distribution of birds between the Wuyi Mountains in south‐eastern China and south‐western China. Although several species exhibit the Wuyi disjunction, the process behind this unusual distribution pattern has remained relatively unstudied. Therefore, we used the Chestnut‐vented Nuthatch Sitta nagaensis as a model species to investigate the possible causes of the Wuyi disjunction. Based on phylogenetic analyses with three mitochondrial and six nuclear regions, the Wuyi population of the Chestnut‐vented Nuthatch was closely related to populations in mid‐Sichuan, from which it diverged approximately 0.1 million years ago, despite the long geographical distance between them (over 1,300 km). In contrast, geographically close populations in mid‐ and southern Sichuan were genetically divergent from each other (more than half a million years). Ecological niche modelling suggested that the Chestnut‐vented Nuthatch has experienced dramatic range expansions from Last Interglacial period to Last Glacial Maximum, with some range retraction following the Last Glacial period. We propose that the Wuyi disjunction of the Chestnut‐vented Nuthatch was most likely due to recent range expansion from south‐western China during the glacial period, followed by postglacial range retraction.     

Evaluating two new methods for capturing large wetland birds

ABSTRACT.   Waterbird research increasingly involves capturing birds to measure attributes of individuals and for attachment of telemetry devices, but there are few established techniques for capturing wading birds away from their nests. We describe the construction and testing of a new trapping technique for wading birds based on a small flip trap. Our trap was developed to capture wading birds in the Florida Everglades in water less than 30 cm deep, but could also be used to capture other waterbirds and upland species. The primary advantages of this new trap design are its ability to be easily concealed, ability to selectively capture birds, low injury rate, ease of resetting the trap after captures, minimal training requirements for operator, capacity to be fired remotely, and moderate cost. We also evaluated the effectiveness of using a net gun to capture wading birds in wetlands. Our results demonstrated that the net gun was the most effective method for capturing large numbers of wading birds, however, the modified flip trap provides a safer alternative that may be appropriate for endangered species.     

Responses of an African wading bird community to resource pulses are related to foraging guild and food‐web position

1. The immediate impacts of nutrient inputs on aquatic systems are well documented, but the ways in which resource pulses affect the wider food web of water‐associated vertebrates remain obscure. 2. We monitored the wading bird community of Barberspan, a natural freshwater lake and Ramsar wetland in South Africa, before, during and after the addition of a pulse of nutrients in the form of a sewage overspill from an upstream processing facility. We counted waders at 13 points around the lake over 3 years, every 2 months from March 2007 to March 2010, and sampled water quality during all counting periods from January 2008 to January 2010. 3. We used our data to test the hypothesis that wading birds that forage directly at lower trophic levels and/or on prey populations that have fast turnover rates, such as those of phytoplankton and invertebrates, will be more heavily influenced by nutrient addition than birds that forage on species with lower turnover rates and/or at higher trophic levels (such as frogs and fish). 4. During the sampling period Barberspan experienced a significant, nutrient‐driven decline and subsequent recovery in dissolved oxygen and pH. This trend was mirrored by significant changes in the wading bird community. Partial Mantel tests and Canonical Correspondence Analysis (CCA) showed that the nutrient pulse had marked short‐term, negative impacts on both the diversity and the abundance of medium‐sized, shoreline foragers such as scolopacids (e.g. sandpipers). 5. Our analysis supports the proposal that both food‐web position and the turnover rate of the prey population are strong influences on ecological responses to resource pulses. Analysis of time series of principal components that describe community composition suggested that recovery of the prey base was rapid and that the bird community was able to respond via immigration. These results must, of course, be considered provisional in the absence of replicated experimental data. 6. More generally, we interpret our results as suggesting that two different mechanisms act in different directions to determine the sensitivity of secondary and tertiary consumers to changes in their prey. First, for ‘earlier’ consumers (i.e. that forage lower in the food web), there are (on average) fewer generalist consumers and fewer stored nutrients in the intervening trophic levels. This increases the sensitivity of earlier consumer populations to changes in the composition of the primary consumer community. Second, the dynamics of prey populations lower in the food web tend to be faster, making recovery faster and serving to decrease the sensitivity of earlier consumers to perturbations. These dynamics may obscure the impacts of nutrient pulses in cases where additional analysis of system trajectories is not undertaken.     

Where and when does a ring start and end? Testing the ring-species hypothesis in a species complex of Australian parrots

Speciation, despite ongoing gene flow can be studied directly in nature in ring species that comprise two reproductively isolated populations connected by a chain or ring of intergrading populations. We applied three tiers of spatio-temporal analysis (phylogeny/historical biogeography, phylogeography and landscape/population genetics) to the data from mitochondrial and nuclear genomes of eastern Australian parrots of the Crimson Rosella Platycercus elegans complex to understand the history and present genetic structure of the ring they have long been considered to form. A ring speciation hypothesis does not explain the patterns we have observed in our data (e.g. multiple genetic discontinuities, discordance in genotypic and phenotypic assignments where terminal differentiates meet). However, we cannot reject that a continuous circular distribution has been involved in the group's history or indeed that one was formed through secondary contact at the 'ring's' east and west; however, we reject a simple ring-species hypothesis as traditionally applied, with secondary contact only at its east. We discuss alternative models involving historical allopatry of populations. We suggest that population expansion shown by population genetics parameters in one of these isolates was accompanied by geographical range expansion, secondary contact and hybridization on the eastern and western sides of the ring. Pleistocene landscape and sea-level and habitat changes then established the birds' current distributions and range disjunctions. Populations now show idiosyncratic patterns of selection and drift. We suggest that selection and drift now drive evolution in different populations within what has been considered the ring.     

Phylogeography of the tree lizard, Urosaurus ornatus: responses of populations to past climate change

Isolation due to both geological barriers and range contractions during the Pleistocene glacial maxima has been an important cause of diversification of arid-adapted species in the North American deserts. Tree lizards, Urosaurus ornatus, are distributed across much of the southwestern arid regions and can tolerate a wide range of environments. Thus, they may have avoided large-scale shifts in distribution caused by Pleistocene climate change and any subsequent evolutionary impacts. Cytochrome b sequences were sampled from U. ornatus across the northern part of their range to test if current structure of these populations resulted from post-Pleistocene range expansion and habitat fragmentation, or prior geological isolation. Phylogenetic analyses found geographical structuring of populations consistent with a model of long-term geographical isolation corresponding to each of the desert regions. The two post-Pleistocene hypotheses were not well supported as estimated times of divergence predated the retreat of the last continental ice sheet. Populations in different regions were impacted by different processes. Southern populations of U. ornatus appear to have remained largely independent of more derived northern and eastern populations during Pleistocene climate change, while populations in regions containing more derived populations showed evidence of more recent range expansion (Colorado Plateau). As populations of U. ornatus attest to, the complex and dynamic history of the southwestern USA has left a deep-rooted and multifaceted imprint on genetic and phylogeographical structure of the species living there.     

长洲水利枢纽建坝后对库区水鸟影响的预测分析

长洲水利枢纽库区分布有41种水鸟,其中38种是涉禽,它们主要栖息于河谷带。环境影响评价分析表明,大坝建成蓄水后将给涉禽带来很不利的影响。由于生境的改变,库区水鸟群落将发生变化,涉禽的种类和数量将减少,而游禽的种类和数量将增多。建议开展受威胁的珍稀水鸟海南鳽(Gorsachius magnificus)的生态生物学研究,以便提出有效的保护措施。     

Morphological and phylogenetic evidence for hybridization and introgression in a sea star secondary contact zone

Abstract. Glacial cycles and other climatic events have been widely invoked as factors promoting divergence, secondary contact, and hybridization between populations of terrestrial organisms, but the origin and fate of secondary contact in the sea is much less well understood. We studied the distribution of morphological and genetic variation in a northwest Atlantic zone of secondary contact between congeneric sea stars of Asterias that probably separated after the Pliocene as part of the trans-Arctic interchange. These species have similar reproductive biology and can hybridize in the laboratory. However, multivariate analysis of morphological traits scored from sea stars inside and outside the zone of secondary contact clearly indicated two clusters of phenotypes that corresponded to the two taxonomic species. A quantitative analysis of this clustering pattern did not support the hypothesis of a third grouping that might correspond to intermediate hybrid phenotypes. Known F₁ hybrids from laboratory matings grouped with one of the two taxonomic species. However, a survey of mtDNA sequence variation clearly indicated that ∼13% of individuals of one species ( Asterias forbesi ) are descendants of hybridization events that resulted in introgression of haplotypes of Asterias rubens into populations of A. forbesi . We conclude that morphological phenotypes are inadequate to identify hybrids of Asterias and their descendants, and that hybridization and introgression might be common in this secondary contact zone.     

Can ecosystem services be integrated with conservation? A case study of breeding waders on grassland

We review published studies to show that changes in soil moisture levels have significant impacts on a range of wading bird species that use UK lowland grassland, including wet grassland, and obtain their food predominantly by probing the soil. We examine both the hydrological and the ecological literature and assess how management options could alter (1) ecosystem services (via water quality and flooding) and (2) habitat quality for wading birds. The combination of biodiversity goals with broader ecosystem services has been widely advocated and we suggest that appropriate management at multiple scales (e.g. small‐scale: ponds; large‐scale: integrated washlands) could potentially provide both ecosystem services and habitat for wading grassland birds. However, there is only a limited base of evidence on which to assess the potential linkage between these two areas, particularly for non‐wading bird species. Future work should be directed at identifying (1) how crop yield, ecosystem services and biodiversity relate to each other, (2) the extent of land needed to be managed to benefit these multiple purposes and bring about measurable gain (e.g. one or two ponds may make significant inroads in reducing run‐off and pollution but make little difference to wading birds) and (3) solutions to the challenges of setting up management options at large spatial scales (e.g. catchments).     

Phylogeographic and population genetic analyses reveal Pleistocene isolation followed by high gene flow in a wide ranging,but endangered,freshwater mussel

Freshwater organisms of North America have had their contemporary genetic structure shaped by vicariant events, especially Pleistocene glaciations. Life history traits promoting dispersal and gene flow continue to shape population genetic structure. Cumberlandia monodonta, a widespread but imperiled (IUCN listed as endangered) freshwater mussel, was examined to determine genetic diversity and population genetic structure throughout its range. Mitochondrial DNA sequences and microsatellite loci were used to measure genetic diversity and simulate demographic events during the Pleistocene using approximate Bayesian computation (ABC) to test explicit hypotheses explaining the evolutionary history of current populations. A phylogeny and molecular clock suggested past isolation created two mtDNA lineages during the Pleistocene that are now widespread. Two distinct groups were also detected with microsatellites. ABC simulations indicated the presence of two glacial refugia and post-glacial admixture of them followed by simultaneous dispersal throughout the current range of the species. The Ouachita population is distinct from others and has the lowest genetic diversity, indicating that this is a peripheral population of the species. Gene flow within this species has maintained high levels of genetic diversity in most populations; however, all populations have experienced fragmentation. Extirpation from the center of its range likely has isolated remaining populations due to the geographic distances among them.     

Population differentiation and evolution in the common guillemot Uria aalge

Common (Uria aalge) and Brünnich's guillemots (U. Iomvia) are colonial seabirds that nest in temperate to arctic oceans throughout the Northern hemisphere. They are very similar in the characteristics of ecology, demography and life history that are thought to determine the extent of differentiation among populations, yet geographic variation in morphology is notably greater in common guillemots. Despite evidence of strong natal philopatry, previous analyses of allozymes and the mitochondrial cytochrome b gene revealed little genetic differentiation among North Atlantic colonies of Brünnich's guillemots. To determine if the more extensive morphological variability in common guillemots reflects greater genetic variability, we sequenced part of the cytochrome b gene for 160 common guillemots from 10 colonies distributed throughout the Northern hemisphere. Genotype frequencies and phylogenetic relationships among genotypes both indicated that Atlantic and Pacific populations are genetically distinct. Genetic divergence among genotypes suggested that differentiation of these populations has resulted from separation by Pleistocene glaciers and the Bering Landbridge, as well as by currently unsuitable breeding habitat in the Arctic Ocean. Cytochrome b genotype frequencies also differed among Atlantic colonies, and appeared to define a cline similar to that described for morphological characters. Analyses of sequence variation suggested that this variation probably results from secondary contact between two refugial populations from the Pleistocene glaciations, rather than from isolation by distance or selection. In contrast, the Atlantic population of Brünnich's guillemots appears to have arisen through recent expansion of a single homogeneous refugial population.     

Genetic divergence and introgressive hybridization betweenAlnus sinuata andA. crispa (Betulaceae)

The actinorhizal genusAlnus contains numerous taxa that have been morphologically classified into different subgenera, species and subspecies. The genetic divergence has been evaluated within subg.Alnobetula between the parapatric taxaAlnus sinuata andA. crispa, using diversity of allozyme markers at 15 structural loci among 20 populations. Evidence for introgressive hybridization at the overlap of their ranges was noted in three populations. However, the width of the hybrid zone appeared tenuous. The average genetic distance derived from the comparisons of conspecific populations was much smaller than the interspecific distance (D = 0.047). This allelic divergence was also paralleled with larger amounts of allelic and genotypic diversity within and among populations ofA. sinuata, which are occupying a more heterogenous ecological niche. It is proposed that the repeated advances and retreats of the ice sheet during the Pleistocene may have promoted the divergence and allopatric evolution of these subspecies, and that secondary contact may have occurred repeatedly during the interglacial periods. The dynamic-equilibrium model would predict in such cases that narrow hybrid zones, formed at the contact of parapatric ranges, would impede gene exchange between parental taxa by selection against hybrids. The results obtained in this study seemed concordant with this hypothesis, as they were also in agreement with the existent taxonomical treatment of these taxa based on morphology.     

Top–down control by great blue herons Ardea herodias regulates seagrass‐associated epifauna

Top predators can influence the structure and function of plant and animal communities. In coastal marine systems, fish, shark and mammal population declines are major drivers of recent ecosystem‐level change. Cascading effects of predatory wading birds, however, are less understood, even though wading bird populations have declined in many regions. We quantified the effects of predation by the piscivorous great blue heron Ardea herodias fannini on fish, invertebrates and epiphytes living in eelgrass Zostera marina. We found that herons forage on benthic fish in seagrass meadows, and foraging intensity increased from late spring until midsummer. When we experimentally excluded herons, benthic fish abundance increased, and the invertebrate assemblage shifted to more shrimp‐dominated assemblages while grazing gammarid amphipod abundance declined. These shifts were associated with reduced epiphyte abundance when herons were excluded, reflecting a four‐level trophic cascade and mediated by shifts in the grazer assemblage. In summary, we found that a piscivorous wading bird species exerts top down control in a subtidal seagrass ecosystem. Losses and recovery of wading birds could have ecosystem‐level ecological consequences that may need to be considered in the context of concern for overfishing and predator recovery in marine coastal management.