We compared species composition, relative abundances, and species richness of reference‐site fish assemblages to fish samples collected from Pinelands streams that displayed a range of water quality and watershed land‐use characteristics. We used detrended correspondence analysis (DCA) and principal component analysis (PCA) to relate community gradients to a complex watershed disturbance gradient characterized by increasing pH, specific conductance, and the percentage of developed and agricultural land in a drainage basin. Native species occurred across a range of conditions and dominated all sites. The major difference between reference‐site assemblages and those found in degraded streams was the occurrence of nonnative species at the degraded sites. Species whose occurrence within New Jersey is generally limited to the Pinelands were more frequently found at reference sites compared with disturbed sites, but these differences were not statistically significant. Based on relative abundance, only two native species displayed a clear affinity to either the disturbed or undisturbed end of the watershed gradient. Species richness did not clearly distinguish reference sites from degraded sites. Neither species composition nor species richness was related to stream size. Species composition based on presence/absence provided as good an estimate of Pinelands watershed disturbance as did relative abundance. The study demonstrates that ordination of presence/absence or relative abundance data using DCA provides a good measure of Pinelands watershed conditions. When evaluating assemblages found at both reference sites and degraded sites, our approach can provide at least part of the basis for developing regional metrics to assess the status of species‐poor fish communities or ranking biological samples based on inherent community attributes.
Reptiles are increasingly of conservation concern due to their susceptibility to habitat loss, emerging disease, and harvest in the wildlife trade. However, reptile populations are often difficult to monitor given the frequency of crypsis in their life history. This difficulty has left uncertain the conservation status of many species and the efficacy of conservation actions unknown. Environmental DNA (eDNA) surveys consistently elevate the detection rate of species they are designed to monitor, and while their use is promising for terrestrial reptile conservation, successes in developing such surveys have been sparse. We tested the degree to which inclusion of surface and soil eDNA sampling into conventional artificial‐cover methods elevates the detection probability of a small, cryptic terrestrial lizard, Scincella lateralis. The eDNA sampling of cover object surfaces with paint rollers elevated per sample detection probabilities for this species 4–16 times compared with visual surveys alone. We readily detected S. lateralis eDNA under cover objects up to 2 weeks after the last visual detection, and at some cover objects where no S. lateralis were visually observed in prior months. With sufficient sampling intensity, eDNA testing of soil under cover objects produced comparable per sample detection probabilities as roller surface methods. Our results suggest that combining eDNA and cover object methods can considerably increase the detection power of reptile monitoring programs, allowing more accurate estimates of population size, detection of temporal and spatial changes in habitat use, and tracking success of restoration efforts. Further research into the deposition and decay rates of reptile eDNA under cover objects, as well as tailored protocols for different species and habitats, is needed to bring the technique into widespread use.
The composition and diversity of metazoan parasite communities in naturally depauperate ecosystems are rarely studied. This study describes the composition of helminth endoparasite communities infecting fish that are part of naturally acidic stream ecosystems in the coastal-plains region of the State of New Jersey (USA) known as the Pinelands, and compares the diversity of parasites between six streams that differ in anthropogenic disturbance. A total of 514 fish were examined representing 6 species native but restricted to the Pinelands region, 5 species native and widespread throughout the region and State, and 6 species introduced to the Pinelands and State. Fish (prevalence: 78%) were infected with 18 helminth endoparasite species. In most streams, prevalence of infection, mean abundance, and total number of individuals for the 5 most common parasites were higher in pirate perch, a native fish species. The diversity of helminth endoparasite communities measured as species richness and Shannon index was higher in degraded streams, and especially in native or introduced fish at these sites. Parasite diversity was positively correlated with anthropogenic disturbance, which was measured by water pH, water conductance, and the proportion of agricultural and developed land surrounding streams. Helminth community composition included parasites intimately tied to trophic interactions in food webs, and disturbance to these ecosystems results in changes to these communities. Understanding structure and function of animal communities from these naturally depauperate ecosystems is important before continued anthropogenic changes result in the extirpation or extinction of their unique fauna.
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