ENDANGERED LIGHT‐FOOTED CLAPPER RAIL AFFECTS PARASITE COMMUNITY STRUCTURE IN COASTAL WETLANDS

We conducted a Before‐After‐Control‐Impact (BACI) study using larval digeneans infecting the California horn snail,Cerithidea californica, to evaluate the success of an ecological restoration project at Carpinteria Salt Marsh in California, USA. Digenean trematodes are parasites with complex life cycles requiring birds and other vertebrates as final hosts. We tested two hypotheses for prevalence and species richness of larval trematodes inC. californica: (1) prior to the restoration, sites to be restored would have lower trematode prevalence and species richness relative to unimpacted control sites, and (2) that these differences would diminish after restoration. The sites to be restored were initially degraded for trematode species. They had a mean trematode prevalence (12%) and species richness (4.5 species) that were lower than control sites (28% trematode prevalence and 7 species). Despite the differences in prevalence, the proportional representation of each trematode species in the total community was similar between sites to be restored and control sites. Over the six years following restoration, trematode prevalence nearly quadrupled at restored sites (43%) while the prevalence at control sites (26%) remained unchanged. In addition, species richness at restored sites doubled (9 species), while species richness at the control sites (7.8 species) did not change. Immediately after restoration, the relative abundance of trematode species using fishes as second intermediate hosts declined while those using molluscs as second intermediate hosts increased. Trematode communities at restored and control sites gradually returned to being similar. We interpret the increase in trematode prevalence and species richness at restored sites to be a direct consequence of changes in bird use of the restored habitat. This study demonstrates a new comparative technique for assessing wetlands, and while it does not supplant biotic surveys, it informs such taxonomic lists. Most importantly, it provides a synthetic quantification of the linkages among species in wetland food webs.

We assessed how spatial and temporal heterogeneity and competition structure larval trematode communities in the pulmonate snail Lymnaea stagnalis . To postulate a dominance hierarchy, mark-release-recapture was used to monitor replacements of trematode species within snails over time. In addition, we sampled the trematode community in snails in different ponds in 3 consecutive years. A total of 7,623 snails (10,382 capture events) was sampled in 7 fishponds in the Jindřichův Hradec and Třeboň areas in South Bohemia (Czech Republic) from August 2006 to October 2008. Overall, 39% of snails were infected by a community of 14 trematode species; 7% of snails were infected with more than 1 trematode species (constituting 16 double- and 4 triple-species combinations). Results of the null-model analyses suggested that spatial heterogeneity in recruitment among ponds isolated trematode species from each other, whereas seasonal pulses in recruitment increased species interactions in some ponds. Competitive exclusion among trematodes led to a rarity of multiple infections compared to null-model expectations. Competitive relationships among trematode species were hypothesized as a dominance hierarchy based on direct evidence of replacement and invasion and on indirect evidence. Seven top dominant species with putatively similar competitive abilities (6 rediae and 1 sporocyst species) reduced the prevalence of the other trematode species developing in sporocysts only.

Loss and modification of tidal marsh habitat has contributed to the decline of marsh bird species. For many marsh birds that inhabit tidal ecosystems, little information exists on habitat use, particularly in relation to movement and response to prey availability. In this study, radio-telemetry was used to investigate home range size, movement patterns and response of Clapper Rails (Rallus longirostris) to prey availability within tidal marshes in coastal Mississippi. Mean fixed kernel 95% home range for breeding Clapper Rails was 1.37 ha ± SE 0.27 (N = 10 birds) with a 50% core use area 0.32 ha ± SE 0.07 (N = 10 birds), which are estimates similar to those obtained throughout this species' range. The extent of Clapper Rail movements during the incubation period was negatively correlated with density of fiddler crab burrows within 50 m of nest sites. Clapper Rails' use of marsh edge decreased relative to tidal height. Use of this habitat type may have been further restricted during the first few weeks of the parental-care period when adults were caring for recently fledged young. Collectively these results illustrate the importance of edge and interior marsh habitats and may provide an explanation for the variation in Clapper Rail densities found within and between tidal marsh systems.

Charlie's Pond (North Carolina) harbors a diverse community of trematodes that infect the planorbid snail Helisoma anceps. Research at the Pond began in 1984 and serves as a foundation on which to investigate long-term changes in trematode communities. In 2002, 2005, and 2006 average size and fecundity of H. anceps were calculated each month, and seasonal trends analyzed with randomization tests. Concomitantly, trematode infections were recorded, and the community composition compared to those from previous studies. Helisoma anceps in 2002, 2005, and 2006 were smaller and less fecund than snails in 1984. The trematode community was consistently diverse, with 11 species recovered in 2006 versus 7 in 1984. However, the prevalence of Halipegus occidualis was much lower than previously observed (60% in 1984) and never exceeded 20% during the latter years. The decline of emergent vegetation is likely contributing to these changes. Aquatic macrophytes increase the surface area for growth of periphyton, the food source of these snails. Limited food supplies result in lower snail growth rates and fecundity. Similarly, emergent vegetation creates foci of transmission for H. occidualis between the frog definitive host and the snail intermediate host. When these areas are lost from the Pond, probability of transmission is reduced, and prevalence in the snail declines.

The feeding habits of five nominal subspecies of clapper rails (Rallus longirostris Boddaert) collected in tidal marshes along the Gulf and Atlantic coasts of the United States are compared. Data on the food from the stomachs of 183 rails were analyzed and the earlier literature critically reviewed. During the warmer months (May through early fall), crabs, predominantly Uca spp., comprised the major part of the food items found. Limited data on a few rails collected during late fall and winter, when Uca spp. are not usually available, indicate that snails then become a major part of the clapper rail’s diet during that part of the year. Earlier studies, which describe the food or feeding habits of clapper rails, are reviewed and the food habits and trophic relationships of some other tidal marsh consumers are discussed. Data from this and previous studies indicate that clapper rails are opportunistic omnivores, and occupy a relatively broad niche within tidal marsh ecosystems. A comparison of available data of the food of five clapper rail subspecies of the eastern United States indicates no distinct differences in their feeding behavior. Differences in the kinds of food eaten appear to simply reflect the types of marsh habitat (fresh, brackish, polyhaline) or geographical location (temperate, subtropical, tropical) in which a particular clapper rail population occurs. The food habits of the king rail are compared with those of the clapper rail and problems concerning the taxonomic status of the “subspecies” of Rallus longirostris are briefly discussed.

Much of North America’s tidal marsh habitat has been significantly altered by both natural and man-made processes. Thus, there is a need to understand the trophic ecology of organisms endemic to these ecosystems. We applied carbon (δ 13C) and nitrogen (δ 15N) stable isotope analysis, along with isotope mixing models, to egg yolk, liver, and muscle tissues of clapper rails (Rallus longirostris) and their likely prey items. This analysis enabled us to explore variation in trophic niche and diet composition in this important marsh bird in two northern Gulf of Mexico tidal marshes that are river and ocean-dominated. For the river-associated estuary, δ 13C and δ 15N of egg yolks, liver, and pectoral muscle tissue samples provided evidence that clapper rails maintained a similar diet during both the winter and the breeding season. A trophic link between C3 primary productivity and the clapper rail’s diet was also indicated as the δ 13C of clapper rail egg yolks related negatively with the aerial cover of C3 macrophytes. Clapper rails from the ocean-dominated estuary had a narrower trophic niche and appeared to be utilizing marine resources, particularly, based on modeling of liver stable isotope values. Variation in stable isotope values between egg yolk and liver/muscle in both systems suggests that endogenous resources are important for egg production in clapper rails. These results demonstrate that diet composition, prey source, and niche width of clapper rails can vary significantly across different estuaries and appear to be influenced by hydrological conditions.

Hybridization is common in bird populations but can be challenging for management, especially if one of the two parent species is of greater conservation concern than the other. King rails (Rallus elegans) and clapper rails (R. crepitans) are two marsh bird species with similar morphologies, behaviors, and overlapping distributions. The two species are found along a salinity gradient with the king rail in freshwater marshes and the clapper in estuarine marshes. However, this separation is not absolute; they are occasionally sympatric, and there are reports of interbreeding. In Virginia, USA, both king and clapper rails are identified by the state as Species of Greater Conservation Need, although clappers are thought to be more abundant and king rails have a higher priority ranking. We used a mitochondrial DNA marker and 13 diagnostic nuclear single nucleotide polymorphisms (SNPs) to identify species, classify the degree of introgression, and explore the evolutionary history of introgression in two putative clapper rail focal populations along a salinity gradient in coastal Virginia. Genetic analyses revealed cryptic introgression with site‐specific rates of admixture. We identified a pattern of introgression where clapper rail alleles predominate in brackish marshes. These results suggest clapper rails may be displacing king rails in Virginia coastal waterways, most likely as a result of ecological selection. As introgression can result in various outcomes from outbreeding depression to local adaptation, continued monitoring of these populations would allow further exploration of hybrid fitness and inform conservation management.

Haemulids (grunts) represent one of the most diverse families of marine fishes. Even though haemulids are well represented in Mexico along the Pacific and Gulf of Mexico coasts, as well as in the Caribbean Sea, their trematode fauna has been scarcely studied. Here, 8 species of Haemulon from the Puerto Morelos Reef National Park (PMRNP), Quintana Roo were analyzed to describe their trematode species composition and the patterns of their community structure at both, infracommunity and component community levels. Eleven species of trematodes from the gastrointestinal tract of their hosts were identified. Overall, 16 new host records are reported in this study. Eight of the 11 trematode species are reported in the PMRNP for the first time. All trematode species were considered as rare species, with prevalence values < 20%. Species accumulation curves showed that 3 of the 6 host species, i.e., H. flavolineatum, H. plumierii, and H. sciurus, reached an asymptote, and only their trematode community structure was analyzed. Communities were species-poor and dominated by a single trematode species, with low diversity values at both, infracommunity and component community levels. Trematode communities differ among species of grunts analyzed in this study, indicating that ecological factors such as feeding habits, geographic distribution, and host vagility play a major role structuring these communities.

Extensive data characterizing larval trematode communities in marine gastropods do not exist for many systems. The purpose here is to report on the infections encountered in Delaware Ilyanassa obsoleta and to compare this trematode community with certain others that have been well studied. Over 15 yr, 11,774 I. obsoleta from 9 different estuarine habitats were examined. Trematode parasitism, sex, and size were determined for each snail. In the total collection, 9 trematode species were encountered; 51.04% of snails were infected with 1 or more species. The sexes were equally susceptible to being parasitized. Smaller snails were less likely to be infected than larger ones. Juvenile snails can be infected, but few have been colonized because of the short time they have been exposed to infective stages. Other studies of trematodes in this snail have revealed few multispecies infections. In contrast, they were strikingly common in this study (12.57% of all snails). Himasthla quissetensis seldom infects the same snail with Lepocreadium setiferoides or Austrobilharzia variglandis, but other species combinations can coexist. The important element in this trematode community seems to be time. The observed frequencies of different infracommunities (single and multispecies combinations) in samples of snails are considered to result from a variety of causes. These include commonness of the trematode species in the system, where and how the sample was collected, definitive host behavior, the low probability of a snail becoming infected, the long life of the snail and its infections, the vagility of the snail, and the incompatibility of certain species in terms of infecting the same snail.

Coupled impacts of sea-level rise and tidal marsh restoration on endangered California clapper rail

We sampled clapper rail (Rallus crepitans) feathers from museum specimens collected between 1965 and 2010 to investigate changes in mercury (Hg) availability in coastal marshes of New Hanover County, North Carolina. Stable isotope analysis (δ(13)C and δ(15)N) was conducted to control for dietary shifts that may have influenced Hg exposure. Hg concentrations ranged from 0.96 to 9.22μg/g (ppm), but showed no significant trend over time; diet (δ(15)N) or foraging habitat (δ(13)C) also provided little to no explanatory power to the variation in Hg concentrations among clapper rails. Our findings suggest the bioavailability of Hg to clapper rails in coastal North Carolina salt marshes has remained consistent over time, despite the global trend of increasing mercury in many other bird species, providing an excellent baseline for any future assessment of Hg availability to salt marsh birds in coastal North Carolina.

Of the 18 trematode species that use the horn snail, Cerithidea californica, as a first intermediate host, 6 have the potential to use raccoons as a final host. The presence of raccoon latrines in Carpinteria Salt Marsh, California, allowed us to investigate associations between raccoons and trematodes in snails. Two trematode species, Probolocoryphe uca and Stictodora hancocki, occurred at higher prevalences in snails near raccoon latrines than in snails away from latrines, suggesting that raccoons may serve as final hosts for these species. Fecal remains indicated that raccoons fed on shore crabs, the second intermediate host for P. uca, and fish, the second intermediate host for S. hancocki. The increase in raccoon populations in the suburban areas surrounding west coast salt marshes could increase their importance as final hosts for trematodes in this system.

BackgroundAnalysis of the data available from traditional faunistic approaches to mollusc-trematode systems covering large spatial and/or temporal scales in Europe convinced us that a parasite community approach in well-defined aquatic ecosystems is essential for the substantial advancement of our understanding of the parasite response to anthropogenic pressures in urbanised areas which are typical on a European scale. Here we describe communities of larval trematodes in two lymnaeid species, Radix auricularia and Lymnaea stagnalis in four man-made interconnected reservoirs of the Ruhr River (Germany) focusing on among- and within-reservoir variations in parasite prevalence and component community composition and structure.ResultsThe mature reservoir system on the Ruhr River provides an excellent environment for the development of species-rich and abundant trematode communities in Radix auricularia (12 species) and Lymnaea stagnalis (6 species). The lake-adapted R. auricularia dominated numerically over L. stagnalis and played a major role in the trematode transmission in the reservoir system. Both host-parasite systems were dominated by bird parasites (13 out of 15 species) characteristic for eutrophic water bodies. In addition to snail size, two environmental variables, the oxygen content and pH of the water, were identified as important determinants of the probability of infection. Between-reservoir comparisons indicated an advanced eutrophication at Baldeneysee and Hengsteysee and the small-scale within-reservoir variations of component communities provided evidence that larval trematodes may have reflected spatial bird aggregations (infection 'hot spots'). Two life history groupings of dominant species, the 'cyprinid' and 'anatid' parasites, that depict two aspects of progressive eutrophication in this mature reservoir system, were identified.ConclusionsWe conclude that trematode communities in the lake-adapted R. auricularia are better suited for monitoring the effect of environmental change on host-parasite associations in the reservoir system on the Ruhr River and other similar systems due to the important role of this host in trematode transmission in lakes. Whereas variations in trematode community diversity and abundance may indicate the degree of eutrophication on a larger scale (among reservoirs), the infection rates of the two life history groups of dominant species, the 'cyprinid' and 'anatid' assemblages, may be particularly useful in depicting environmental variability, eutrophication effects and infection 'hot spots' on smaller spatial scales.

Coastal ecosystems are threatened by growing pressures related to global change. The evaluation of an ecosystem’s biodiversity and status is by consequence of increasing importance to assess potentially undergone changes and predict their future trajectory for management and conservancy purposes. Biotic indicators sensitive to ecosystem changes are thus continuously sought for. Trematode parasite communities were examined as potential indicators of environmental changes, considering that the achievement of their complex life cycle is modulated by several factors. Indeed, the rule for trematode is that each species complete their cycle by a succession of three different host species and two free-living stages, thus depending on several biotic and abiotic factors. To this end, we examined the trematode community infecting the common cockle in Banc d’Arguin, Arcachon Bay, France. Monthly data extending over 16 years and sampled at a single station were compared to field book notes describing the changes of the closely surrounding landscape. In 2021, we also sampled cockles at 15 stations presenting different substrate features along the bank. Over time, seven out of nine changes of the trematode community structure presented concordances with changes in landscape. We hypothesize this was related to the environment heterogeneous substrate (i.e., temporal succession of oyster parks, bare sands and seagrass) with cascading effects on host populations. However, some changes could not solely be explained by changes in landscape. Our spatial study showed that the trematode communities exhibited intricate infection patterns with a complex interaction between substrate heterogeneity and larval dispersal ability of parasites. Thus, trematode communities might be potential indicators of subtle changes in the environment. However, it remains unclear which scale of environmental changes trematodes are actually sensitive to.

Clapper rails (Rallus longirostris) were used as an indicator species of estuarine marsh habitat quality because of their strong site fidelity and predictable diet consisting of mostly benthic organisms. Mercury (Hg) and the polychlorinated biphenyl (PCB) Aroclor 1268 concentrations were determined for sediments, crabs, as well as clapper rail adults and chicks collected from salt marshes associated with the LCP Superfund site in Brunswick, Georgia. Home ranges were established for adult rails, and sediment and crab samples were taken from each individual's range. The study was designed to minimize the spatial variability associated with trophic transfer studies by choosing an endpoint species with a potentially small home range and specifically sampling its foraging range. The mean home range for clapper rails was 1.2 ha with a median of 0.28 ha. Concentrations of Hg and Aroclor 1268 were shown to increase with each trophic level. Transfer factors between media followed the same pattern for both contaminants with the highest between fiddler crabs and clapper rail liver. Hg and PCB transfer factors were similar between sediment to fiddler crab and fiddler crab to muscle, however the PCB transfer factor from fiddler crabs to liver was over twice as large as for Hg. PCB congener profiles did not significantly differ between media types.