Occurrence of Rhagoletis species in Newfoundland

The presence of Rhagoletis fruit flies in Newfoundland, Canada, was investigated by rearing large numbers of the fruits of known and potential host plant species. Three Rhagoletis species, R. tabellaria (Fitch), R. basiola (Osten Sacken), and the cherry pest species R. fausta (Osten Sacken), were found to occur naturally in Newfoundland, representing a range extension of some 500 km for R. tabellaria and R. basiola. Rhagoletis fausta had previously been reported from sticky traps used to monitor R. mendax Curran, which is not known from the province. To investigate the route by which the two new species may have colonized Newfoundland, R. tabellaria adults were sequenced for a mitochondrial genome fragment (COI–tRNA‐Leu–COII–tRNA‐Lys). This sample was genetically identical or similar to samples from other widely distributed sites in North America, suggesting that the presence of R. tabellaria in Newfoundland is the result of postglacial dispersal rather than survival in a glacial refugium. The implications of these findings for Rhagoletis management in Canada are discussed.     

Permeability of Neotropical agricultural lands to a key native ungulate—Are well‐connected forests important?

Much of what remains of the Earth's tropical forests is embedded within agricultural landscapes, where forest is reduced and fragmented. As native forest ungulates are critical to maintaining forest function, it is imperative to understand how this functional group responds to declines in forest cover and connectivity resulting from agricultural expansion. We addressed this issue by evaluating selection of forest cover and forest connectivity by a key native ungulate of Neotropical forests, the white‐lipped peccary (Tayassu pecari Link 1795, Tayassuidae, Cetartiodactyla), in agricultural landscapes of Brazil. We evaluated selection using compositional analysis at two hierarchical levels, landscape, and home range. From 2013 to 2019, we GPS‐tracked eight white‐lipped peccary herds in Southwest Brazil, resulting in a total of 14,460 GPS locations. We found that herds can live in landscapes with a wide range of forest cover (35%–81% of home ranges covered by native forest), with significant, but not strong, selection at the landscape level (p = .045). Nevertheless, herds strongly select for forest cover within their home ranges (81%–97% of locations within native forest; highly significant selection at the home‐range level: p = .008). As for connectivity, herds significantly select the largest, most connected forest fragments at the landscape level (p = .04), but not at the home‐range level (p = .07). Our results support that Neotropical forests within agricultural landscapes need to be well connected in order to preserve this key native ungulate and maintain long‐term forest function. Abstract in Portuguese is available with online material.     

Unveiling trade‐offs in resource selection of migratory caribou using a mechanistic movement model of availability

Habitat selection is a multi‐level, hierarchical process that should be a key component in the balance between food acquisition and predation risk avoidance (food–predation trade‐off). However, to date, studies have not fully elucidated how fine‐ and broad‐scale habitat decisions by individual prey can help balance food versus risk. We studied broad‐scale habitat selection by Newfoundland caribou Rangifer tarandus, focusing on trade‐offs between predation risk versus access to forage during the calving and post‐calving period. We improved traditional measures of habitat availability by incorporating fine‐scale movement patterns of caribou into the availability kernel, thus enabling separation of broad and fine scales of selection. Remote sensing and field surveys served to create a spatio‐temporal model of forage availability, whereas GPS telemetry locations from 66 black bears Ursus americanus and 59 coyotes Canis latrans provided models of predation risk. We then used GPS telemetry locations from 114 female caribou to assess food–predation trade‐offs through the prism of our refined model of caribou habitat availability. We noted that migratory movements of caribou were oriented mainly towards habitats with abundant forage and lower risk of bear and (to a lesser extent) coyote encounter. These findings were generally consistent across caribou herds and would not have been evident had we used traditional methods instead of our refined model when estimating habitat availability. We interpret these findings in the context of stereotypical migratory behaviour observed in Newfoundland caribou, which occurs despite the extirpation of wolves Canis lupus nearly a century ago. We submit that caribou are able to balance food acquisition against predation risk using a complex set of factors involving both finer and broader scale selection. Accordingly, our study provides a strong argument for using refined habitat availability estimates when assessing food–predation trade‐offs.     

A hitchhiker’s guide to the Maritimes: anthropogenic transport facilitates long‐distance dispersal of an invasive marine crab to Newfoundland

Aim To determine timing, source and vector for the recent introduction of the European green crab, Carcinus maenas (Linnaeus, 1758), to Newfoundland using multiple lines of evidence. Location Founding populations in Placentia Bay, Newfoundland, Canada and potential source populations in the north‐west Atlantic (NWA) and Europe. Methods We analysed mitochondrial and microsatellite genetic data from European and NWA populations sampled during 1999–2002 to determine probable source locations and vectors for the Placentia Bay introduction discovered in 2007. We also analysed Placentia Bay demographic data and shipping records to look for congruent patterns with genetic analyses. Results Demographic data and surveys suggested that C. maenas populations are established and were in Placentia Bay for several years (c. 2002) prior to discovery. Genetic data corroboratively suggested central/western Scotian Shelf populations (e.g., Halifax) as the likely source area for the anthropogenic introduction. These Scotian Shelf populations were within an admixture zone made up of genotypes from both the earlier (early 1800s) and later (late 1900s) introductions of the crab to the NWA from Europe. Placentia Bay also exhibited this mixed ancestry. Probable introduction vectors included vessel traffic and shipping, especially vessels carrying ballast water. Main conclusions Carcinus maenas overcame considerable natural barriers (i.e., coastal and ocean currents) via anthropogenic transport to become established and abundant in Newfoundland. Our study thus demonstrates how non‐native populations can be important secondary sources of introduction especially when aided by human transport. Inference of source populations was possible owing to the existence of an admixture zone in central/western Nova Scotia made up of southern and northern genotypes corresponding with the crab’s two historical introductions. Coastal vessel traffic was found to be a likely vector for the crab’s spread to Newfoundland. Our study demonstrates that there is considerable risk for continued introduction or reintroduction of C. maenas throughout the NWA.     

Spangled perch (Leiopotherapon unicolor) in the southern Murray‐Darling Basin: Flood dispersal and short‐term persistence outside its core range

The spangled perch Leiopotherapon unicolor is considered a rare vagrant in the southern Murray‐Darling Basin, Australia, due to its intolerance of the relatively cool water temperatures that prevail during winter months. This study details 1342 records of the species from 68 locations between 2010 and 2014 outside its accepted ‘core adult range’ following widespread flooding during 2010 and 2011. Although records of the species declined over 2013, L. unicolor remained resident in the southern Murray‐Darling Basin as of April 2014. The species persisted in several locations for three consecutive winters with recruitment documented at two sites. This study represents the first identification of the dispersal of large numbers of L. unicolor into the southern Murray‐Darling Basin, persistence beyond a single winter, and recruitment by the species in habitats south of its recognized ‘core adult range’. Targeted research would determine the potential for predicted environmental changes (artificially warmer drainage wetlands, climate change and greater floodplain connectivity) to facilitate longer term persistence and range expansion by the species in the southern Murray‐Darling Basin.     

Multilocus phylogeography and population structure of common eiders breeding in North America and Scandinavia

Aim Glacial refugia during the Pleistocene had major impacts on the levels and spatial apportionment of genetic diversity of species in northern latitude ecosystems. We characterized patterns of population subdivision, and tested hypotheses associated with locations of potential Pleistocene refugia and the relative contribution of these refugia to the post‐glacial colonization of North America and Scandinavia by common eiders (Somateria mollissima). Specifically, we evaluated localities hypothesized as ice‐free areas or glacial refugia for other Arctic vertebrates, including Beringia, the High Arctic Canadian Archipelago, Newfoundland Bank, Spitsbergen Bank and north‐west Norway. Location Alaska, Canada, Norway and Sweden. Methods Molecular data from 12 microsatellite loci, the mitochondrial DNA (mtDNA) control region, and two nuclear introns were collected and analysed for 15 populations of common eiders (n = 716) breeding throughout North America and Scandinavia. Population genetic structure, historical population fluctuations and gene flow were inferred using F‐statistics, analyses of molecular variance, and multilocus coalescent analyses. Results Significant inter‐population variation in allelic and haplotypic frequencies were observed (nuclear DNA F_ST = 0.004–0.290; mtDNA Φ_ST = 0.051–0.927). Whereas spatial differentiation in nuclear genes was concordant with subspecific designations, geographic proximity was more predictive of inter‐population variance in mitochondrial DNA haplotype frequency. Inferences of historical population demography were consistent with restriction of common eiders to four geographic areas during the Last Glacial Maximum: Belcher Islands, Newfoundland Bank, northern Alaska and Svalbard. Three of these areas coincide with previously identified glacial refugia: Newfoundland Bank, Beringia and Spitsbergen Bank. Gene‐flow and clustering analyses indicated that the Beringian refugium contributed little to common eider post‐glacial colonization of North America, whereas Canadian, Scandinavian and southern Alaskan post‐glacial colonization is likely to have occurred in a stepwise fashion from the same glacial refugium. Main conclusions Concordance of proposed glacial refugia used by common eiders and other Arctic species indicates that Arctic and subarctic refugia were important reservoirs of genetic diversity during the Pleistocene. Furthermore, suture zones identified at MacKenzie River, western Alaska/Aleutians and Scandinavia coincide with those identified for other Arctic vertebrates, suggesting that these regions were strong geographic barriers limiting dispersal from Pleistocene refugia.     

Depth and temperature associations of haddock Melanogrammus aeglefinus off southern Newfoundland

Using data collected as part of offshore surveys conducted during 1972–2013, haddock Melanogrammus aeglefinus association patterns with depth and temperature in southern Newfoundland waters, the northern extremity of the species' range in the western Atlantic Ocean, were quantified. They were typically concentrated in the deep warm waters along the narrow shelf slope in North‐west Atlantic Fisheries Organization Divisions 3O and 3P with individuals moving seasonally into the shallow waters of the banks as they warmed. While M. aeglefinus were found over a range of depths and temperatures, they were primarily located at depths deeper and temperatures warmer than the median sampled. Analyses demonstrated that of the two hydrographic variables assessed, temperature was most influential in structuring distribution, with individuals appearing to change depth in order to maintain similar temperature throughout the year. Melanogrammus aeglefinus were found predominantly in temperatures of c. 4–8° C which often represented some of the warmest waters available. Differences in fish‐habitat association patterns in relation to sex or maturity status were not readily apparent from the analyses. Warming conditions off Newfoundland and Labrador in recent years might be predicted to improve local M. aeglefinus productivity.     

Annual trend of fish assemblages associated with FADs in the southern Tyrrhenian Sea

A study on fish assemblage associated with fish aggregating devices (FADs) in Sicily was carried out between January 2000 and January 2001. With a fortnightly periodicity, 156 experimental hauls were carried out by means of a purse seine in a FAD‐containing marine section banned to commercial fishing. A total of 14 229 fish specimens belonging to six families and 10 species was found. These species were Balistes carolinensis, Caranx crysos, Naucrates ductor, Seriola dumerili, Seriola fasciata, Tachurus picturatus, Coryphaena hippurus, Schedophilus ovalis, Thunnus thynnus, Polyprion americanus and showed all young‐of‐the‐year undergoing a rapid growth. The applied ordination technique highlighted the existence of four assemblage periods describing the annual trend. The results confirm that fish assemblages associated with FADs are related to season, following a fish colonization tied to natural recruitment. Comparison of the ecological indices across the four periods showed that the assemblages in the periods from summer to winter were more structured than those in spring. The quantity of individuals also showed a strong variation peaking in the summer period. The results of this study reveal that FADs represent a particular nursery area for the associated species that could influence their survival.     

Characteristics and Antioxidant Activity of Lignans in Schisandra chinensis and Schisandra sphenanthera from Different Locations

Twenty Schisandra samples were collected from different locations. Contents of 7 lignans in the samples were determined and analyzed by HPLC method coupled with hierarchical clustering analysis (HCA) and principal component analysis (PCA), and the antioxidant capacity of Schisandra from the different locations was evaluated by reducing power, ferric thiocyanate (FTC) and 2,2′‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. The results showed that there was a significant difference in the content of lignans between Schisandra chinensis and Schisandra sphenanthera. The Schisandra sphenanthera samples in the southwest of China were significantly different from those from the other locations. The antioxidant capacity of Schisandra chinensis was significantly superior to that of Schisandra sphenanthera, and the main antioxidant components were schisandrol A, schisandrol B and schisandrin B based on the result of discrimination analyses. The differences in the chemical composition and antioxidant activity of lignans in Schisandra chinensis and Schisandra sphenanthera from the different locations were investigated in this study, which may provide an experimental basis for the quality control of Schisandra.     

Re‐evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP

Terfelt, F, Bagnoli, G. & Stouge, S. 2011: Re‐evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP. Lethaia, Vol. 45, pp. 227–237. In 2000, the International Union of Geological Sciences (IUGS) ratified the decision from the International Working Group on the Cambrian–Ordovician Boundary (COBWG) to place the Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System in the Green Point section, Newfoundland, Canada, at a point coinciding with the first appearance of the conodont Iapetognathus fluctivagus. However, a restudy of the conodont successions from Green Point shows that this species is not present at the boundary interval, and as a consequence the section does not fulfil the biostratigraphical requirements of a GSSP. The GSSP horizon as now defined is based on a level part‐way through the range of I. preaengensis– a species with lower first appearance datum (FAD). The true FAD of I. fluctivagus is above the FAD of planktonic graptolites and well above the FAD of I. preaengensis. As a consequence of these problems, a restudy of the GSSP section and the other sections in the Cow Head Group is necessary. A redefinition of the GSSP horizon is suggested. The following four alternative horizons have potential as new horizons for the GSSP level: the FAD of Cordylodus intermedius; the FAD of Cordylodus andresi; the FAD of Eoconodontus notchpeakensis; and the FAD of the agnostoid Lotagnostus americanus. □Boundary, Cambrian, conodont, Global boundary Stratotype Section Point, Iapetognathus, Ordovician.     

A new record of whale shark Rhincodon typus in Brazilian waters: a report of association with Caranx crysos

In May 2011, a Rhincodon typus was sighted on the continental shelf of the central Brazilian coast, in the vicinity of a gas platform. During the video record, an interspecific following association was observed between a Caranx crysos school and the R. typus.     

An introduced population of Chorda asiatica (Chordaceae,Laminariales) in Puget Sound,Pacific coast of North America

Northeastern Pacific Ocean and northwestern Atlantic Ocean populations of Chorda species, which have not been examined in previous phylogenetic studies, were investigated. All specimens that were collected in Hood Canal, Puget Sound, WA, USA, Pacific coast of North America, showed identical ITS‐5.8S rDNA sequences, and they were included in the clade of Japanese Chorda asiatica. With morphological data added to the molecular data, they were identified as C. asiatica and were concluded to be non‐indigenous populations, most likely introduced with oyster spat together with Sargassum muticum. Specimens collected in New York, NY, USA, Atlantic coast of North America, were genetically closest to C. filum from Newfoundland and were identified as C. filum. The genetic divergence of the North Atlantic populations of C. filum was relatively small compared to that of Japanese C. asiatica considering their broader distributional ranges on both sides of the Atlantic.     

Stable isotopes can be used to infer the overwintering locations of prebreeding marine birds in the Canadian Arctic

Although assessments of winter carryover effects on fitness‐related breeding parameters are vital for determining the links between environmental variation and fitness, direct methods of determining overwintering distributions (e.g., electronic tracking) can be expensive, limiting the number of individuals studied. Alternatively, stable isotope analysis in specific tissues can be used as an indirect means of determining individual overwintering areas of residency. Although increasingly used to infer the overwintering distributions of terrestrial birds, stable isotopes have been used less often to infer overwintering areas of marine birds. Using Arctic‐breeding common eiders, we test the effectiveness of an integrated stable isotope approach (13‐carbon, 15‐nitrogen, and 2‐hydrogen) to infer overwintering locations. Knowing the overwinter destinations of eiders from tracking studies at our study colony at East Bay Island, Nunavut, we sampled claw and blood tissues at two known overwintering locations, Nuuk, Greenland, and Newfoundland, Canada. These two locations yielded distinct tissue‐specific isotopic profiles. We then compared the isotope profiles of tissues collected from eiders upon their arrival at our breeding colony, and used a k‐means cluster analysis approach to match arriving eiders to an overwintering group. Samples from the claws of eiders were most effective for determining overwinter origin, due to this tissue's slow growth rate relative to the 40‐day turnover rate of blood. Despite taking an integrative approach using multiple isotopes, k‐means cluster analysis was most effective when using 13‐carbon alone to assign eiders to an overwintering group. Our research demonstrates that it is possible to use stable isotope analysis to assign an overwintering location to a marine bird. There are few examples of the effective use of this technique on a marine bird at this scale; we provide a framework for applying this technique to detect changes in the migration phenology of birds' responses to rapid changes in the Arctic.     

PMERGE: Computational filtering of paralogous sequences from RAD‐seq data

Restriction‐site associated DNA sequencing (RAD‐seq) can identify and score thousands of genetic markers from a group of samples for population‐genetics studies. One challenge of de novo RAD‐seq analysis is to distinguish paralogous sequence variants (PSVs) from true single‐nucleotide polymorphisms (SNPs) associated with orthologous loci. In the absence of a reference genome, it is difficult to differentiate true SNPs from PSVs, and their impact on downstream analysis remains unclear. Here, we introduce a network‐based approach, PMERGE that connects fragments based on their DNA sequence similarity to identify probable PSVs. Applying our method to de novo RAD‐seq data from 150 Atlantic salmon (Salmo salar) samples collected from 15 locations across the Southern Newfoundland coast allowed the identification of 87% of total PSVs identified through alignment to the Atlantic salmon genome. Removal of these paralogs altered the inferred population structure, highlighting the potential impact of filtering in RAD‐seq analysis. PMERGE is also applied to a green crab (Carcinus maenas) data set consisting of 242 samples from 11 different locations and was successfully able to identify and remove the majority of paralogous loci (62%). The PMERGE software can be run as part of the widely used Stacks analysis package.     

Assessing the geographic range of Black‐fronted Ground‐Tyrants (Muscisaxicola frontalis) using extralimital and winter range occurrence records and ecological niche modeling

ABSTRACT Estimating the geographic range of a species can be complicated by insufficient occurrence data and a lack of information about range limit determinants. Accurate estimates of species distributions are needed to assess the impacts of anthropogenic actions and for exploring evolutionary and ecological processes that maintain biological diversity. After documenting several extralimital locations for Black‐fronted Ground‐Tyrants (Muscisaxicola frontalis; Tyrannidae), we questioned the accuracy of the current winter range estimate. We provide specimen and observation records from central and southern Peru that represent new information about the winter distribution of Black‐fronted Ground‐Tyrants. We used ecological niche models generated from new extralimital records and records from the winter range to assess the current range estimate. We also tested winter and extralimital niche models for model equivalency using a resampling technique available through Maxent and ENM Tools. Niche models developed with locations from the winter range predicted with high probability (>90%) the area of the extralimital records. Reciprocally, niche models developed with the extralimital locations predicted the majority of the winter range locations, although the probability was lower for some locations and the most southerly points were not included in the prediction. The test for model equivalency did not distinguish the two models, suggesting the possibility that the extralimital records were from poorly sampled areas of the true winter range. Smaller scale habitat associations of Black‐fronted Ground‐Tyrants, such as a preference for sparsely vegetated slopes, were documented that were more specific than published accounts. Finally, we present the first case of frugivory in Muscisaxicola with the identification of Cumulopuntia boliviana ignescens (Cactaceae) seeds and pericarp in all five stomach samples of Black‐fronted Ground‐Tyrants collected in southern Peru.     

Diet of young-of-the-year bluefin tuna, Thunnus thynnus (Linnaeus, 1758), in the southern Tyrrhenian (Mediterranean) Sea

The diet of juvenile bluefin tuna (Thunnus thynnus) caught 2 to 8 miles off NE Sicily was investigated in order to improve knowledge of the species’ early life history. From 1998 to 2000, 107 specimens ranging from 63 to 495 mm (total length) were fished between July and November. Fishes were caught by trolling line or purse seine in a Fish Aggregating Devices (FADs) area 2 to 8 miles offshore and as by‐catch of the purse‐seine sardine fishery 2 to 4 miles offshore. Most frequently found items in the T. thynnus stomachs were fishes (84.5%), crustaceans (54.6%) and cephalopods (50.5%). The largest contribution in weight was provided by cephalopods (47.3%) and fishes (46.5%), while the most abundant items were fishes (51%), cephalopods (27.2%) and crustaceans (21.1%). These results suggest that young‐of‐the‐year tuna have an essentially piscivorous diet, although invertebrate prey provide a substantial contribution to the food array. Prey show little relationship with FADs, although one prey species (blue runner, Caranx crysos) is associated with FADs in the Mediterranean.     

The influence of non‐climate predictors at local and landscape resolutions depends on the autecology of the species

Species distribution models have come under criticism for being too simplistic for making robust future forecasts, partly because they assume that climate is the main determinant of geographical range at large spatial extents and coarse resolutions, with non‐climate predictors being important only at finer scales. We suggest that this paradigm might be obscured by species movement patterns. To explore this we used contrasting kangaroo (family Macropodidae) case studies: two species with relatively small, stable home ranges (Macropus giganteus and M. robustus) and three species with more extensive, adaptive ranging behaviour (M. antilopinus, M. fuliginosus and M. rufus). We predicted that non‐climate predictors will be most influential to model fit and predictive performance at local spatial resolution for the former species and at landscape resolution for the latter species. We compared residuals autocovariate – boosted regression tree (RAC‐BRT) model statistics with and without species‐specific non‐climate predictors (habitat, soil, fire, water and topography), at local‐ and landscape‐level spatial resolutions (5 and 50 km). As predicted, the influence of non‐climate predictors on model fit and predictive performance (compared with climate‐only models) was greater at 50 compared with 5 km resolution for M. rufus and M. fuliginosus and the opposite trend was observed for M. giganteus. The results for M. robustus and M. antilopinus were inconclusive. Also notable was the difference in inter‐scale importance of climate predictors in the presence of non‐climate predictors. In conclusion, differences in autecology, particularly relating to space use, may contribute to the importance of non‐climate predictors at a given scale, not model scale per se. Further exploration of this concept across a range of species is encouraged and findings may contribute to more effective conservation and management of species at ecologically meaningful scales.     

Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Shifting prey availability can lead to altered species interactions, indicated by variation in the dietary niche breadth and position of species within an assemblage. On the Newfoundland coast, annual inshore spawning migration of the dominant forage fish, Capelin Mallotus villosus, provides an excellent opportunity to investigate the influence of varying prey availability on dietary niche breadth and position among species. During June–August 2017, we investigated species‐ and assemblage‐level dietary responses to shifting Capelin availability of three Capelin‐eating, sympatrically breeding auk species, the Atlantic Puffin Fratercula arctica, Razorbill Alca torda and Common Murre Uria aalge. The diet of Leach's Storm Petrels Oceanodroma leucorhoa, which breed alongside the three auk species but are not known to rely on Capelin, was also examined to determine dietary shifts throughout breeding that were unrelated to Capelin availability. We quantified stable isotope ratios (δ¹⁵N, δ¹³C) in seabird blood components (plasma, cellular component) collected both before and after spawning Capelin arrived in the study area and compared isotopic niche breadth within a Bayesian framework. At the species level, auk trophic position increased and isotopic niche breadth narrowed after Capelin arrived, suggesting a more Capelin‐based diet. Simultaneously, trophic diversity of the auk assemblage, reflecting the extent of spacing among niches of species, decreased after spawning Capelin arrived inshore. Contrastingly, increased trophic position but broader isotopic niche breadth during higher relative to lower Capelin availability for Leach's Storm Petrel confirm that this species is probably not affected by the inshore arrival of Capelin, but instead that isotopic changes may be more related to a shift in breeding stage to chick‐rearing. Overall, our findings reiterate the importance of Capelin as a prey resource for breeding auks in coastal Newfoundland, but that the degree of reliance on Capelin varies among species, possibly allowing coexistence of these ecologically similar species. The findings highlight potential changing species interactions, such as increased competition, under declines in Capelin biomass.     

Insect diversity and trophic structure differ on native and non‐indigenous congeneric rushes in coastal salt marshes

Displacement of native plant species by non‐indigenous congeners may affect associated faunal assemblages. In endangered salt marshes of south‐east Australia, the non‐indigenous rush Juncus acutus is currently displacing the native rush Juncus kraussii, which is a dominant habitat‐forming species along the upper border of coastal salt marshes. We sampled insect assemblages on multiple plants of these congeneric rushes in coastal salt marshes in Sydney, New South Wales, Australia, and compared the abundance, richness, diversity, composition and trophic structure between: (i) J. acutus and J. kraussii at invaded locations; and (ii) J. kraussii at locations either invaded or not invaded by J. acutus. Although J. acutus supported a diverse suite of insects, species richness and diversity were significantly greater on the native J. kraussii. Moreover, insect assemblages associated with J. kraussii at sites invaded by J. acutus were significantly different from, and more variable than, those on J. kraussii at non‐invaded sites. The trophic structure of the insect assemblages was also different, including the abundance and richness of predators and herbivores, suggesting that J. acutus may be altering consumer interactions, and may be spreading in part because of a reduction in herbivory. This strongly suggests that J. acutus is not playing a functionally similar role to J. kraussii with respect to the plant‐associated insect species assemblages. Consequently, at sites where this non‐indigenous species successfully displaces the native congener, this may have important ecological consequences for community composition and functioning of these endangered coastal salt marshes.