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We sampled benthic macroinvertebrates and structural habitat characteristics in Ridge and Valley streams of the Lookout Creek watershed (Tennessee River drainage) and evaluated them in relation to landscape features in their respective drainage areas. Reach-specific estimates of EPT family richness (number of families found in the insect orders Ephemeroptera, Plecoptera, and Trichoptera) varied from 6 to 11; intolerant-family richness varied from 1 to 7. We observed relationships among catchment landscape features and stream-reach conditions (Spearman's correlation analysis: P < 0.05). Agricultural and residential building densities in the catchment (number of building units per ha) were inversely correlated with EPT and intolerant-family richness, while streambed substrate size was directly correlated with EPT family richness. Agricultural land cover (% area) was inversely correlated with large woody structure in the stream. Findings from this study illustrate the sensitivity of benthic macroinvertebrate assemblages to stream habitat degradation in relation to agricultural and residential land-use patterns in watersheds.
Coastal ecotones, where marine aquatic and terrestrial habitats interact, are productive systems that often contain abundant and diverse assemblages of invertebrate and vertebrate species and their predators. The availability of allochthonous inputs in combination with resident prey items within tidal marshes could lead to heightened density of terrestrial predators, although research into the ecology of coastal terrestrial predators is sparse. Given the use of coastal impoundments by culturally and economically important waterfowl, some managers are (or are considering) lethally removing terrestrial mammalian carnivores out of concern they are consuming waterfowl species during the overwintering and spring recruitment periods. We conducted a study to determine terrestrial carnivore diets within tidal impoundments in South Carolina during the 2018–2019 winter and spring seasons and compared dietary breadth and overlap among predators. We determined that Lynx rufus (Bobcat) and Procyon lotor (Raccoon), and, to a lesser extent, Canis latrans (Coyote) used coastal impoundments and consumed a diversity of food items that varied between seasons. Bobcat diet was primarily composed of small- to medium-sized mammalian prey, the relative frequency of occurrence of those items being 77% and 65% of scats during winter and spring respectively. The relative frequency of birds in Bobcat diet was higher in spring (32%) compared to winter (18%), with a majority being composed of songbirds and waterbirds, and waterfowl only accounting for 6% of their diet across both seasons. Raccoon diets were primarily composed of vegetation and crustaceans, 2 items not consumed by Bobcats, suggesting the 2 species generally maintain different dietary niches. Small mammals were the only dietary item of potential overlap between these species, but Bobcats were more likely to consume meso-mammals in winter while Raccoons were more likely to consume small mammals in spring. In addition to providing support for dietary niche partitioning as a coexistence mechanism for Bobcats and Racoons in our system, our results suggest that Bobcats (as well as Raccoons) are not predating important waterfowl species within these managed impoundments during these seasons, likely limiting the need for future lethal predator-control strategies.
Cardisoma guanhumi (Blue Land Crab) is a semi-terrestrial crab commonly found from Brazil northwards to the Gulf of Mexico, the Caribbean, and southern Florida in the United States. The northern extent of its range along the eastern seaboard of the United States had been documented as Vero Beach, FL, in 1962; however, in August 2022, South Carolina Department of Natural Resources officials received a series of unsolicited reports of this species, prompting them to examine its distribution. A total of 53 verified Blue Land Crab sightings were reported from September to November 2022 in South Carolina. These results indicate that the Blue Land Crab is widely distributed in South Carolina, an area outside of its historical native range.
Hydrocotyle bonariensis (Largeleaf Pennywort) is a clonal perennial herb often found within its native range in multiple habitats that may differ in environmental factors. Plants can respond to the local environment through phenotypic plasticity, which results in different phenotypes in response to different environmental factors. The aim of this study was to determine the role of phenotypic plasticity in the ability of Largeleaf Pennywort to occupy multiple habitats in coastal Georgia, specifically coastal sand dune and inland coastal plain habitats. We assessed leaf morphology for plants in both their native habitats and also under greenhouse conditions in response to different soils and salt spray. Results showed marked differences in leaf morphology between plants in the different native habitats, and the greenhouse study suggested that plants responded plastically to soil through tissue modifications related to water storage. These results indicate that phenotypic plasticity likely plays an important role in the ability of Largleaf Pennywort to occupy multiple habitats in coastal Georgia.
Persistent soil seed banks are a mechanism by which plant populations, especially those of pioneer species, replenish themselves after disturbance. Germination, and therefore aboveground replenishment, is linked to the abundance and vertical distribution of viable seeds in the soil, but it is unclear how different types of disturbance influence seed-bank structure. This distinction is critical for conservation, as anthropogenic sources increasingly alter the types of disturbance that ecosystems experience. We characterized the vertical structure of the seed banks of Paronychia chartacea (Papery Whitlow-wort) and Hypericum cumulicola (Highlands Scrub St. John's Wort), 2 federally endangered herbs endemic to Florida scrub, in habitats that experience fire (scrub habitat) and vehicle disturbance (roadsides). Within populations of each species in each habitat, we collected soil from 4 soil depths. We used microscopy and a germination study to measure total and viable seed density, then related these values to habitat, soil depth, and aboveground vegetation density. The vertical structure of viable seeds in the seed bank did not significantly differ between the 2 habitats. The top 4 centimeters of soil contained the majority of viable seeds for both species in both habitats, and viable seeds were denser in scrub habitat compared to roadsides. Roadsides contained relatively depauperate seed banks compared to natural, interior scrub. Abundance of viable seeds did not relate to aboveground vegetation density, possibly reflecting higher germination or recruitment on roadsides. This finding calls into question the long-term stability of apparently healthy roadside populations of endemic herbs, and necessitates further research into how seed banks influence the dynamics of these vulnerable species.
Hibernacula used for overwintering by federally endangered Myotis sodalis (Indiana Bat) in Arkansas are well documented and biennially monitored, but little is known about this population's migration paths and summer habitat. Revealing spring migratory behaviors and maternity colony locations of female Indiana Bats informs conservation and management efforts and contributes to our understanding of the species across its range. Radio telemetry has been used to document the behaviors of many bat species and, recently, aerial-based tracking methods have increased our understanding of the migratory habits of female Indiana Bats. During the spring migration periods of 2018–2021, we used aerial- and ground-based telemetry methods to follow female Indiana Bats as they commenced migration from Arkansas caves. Bats migrated north into Missouri, east and south across Arkansas, and southwest into Oklahoma. We located and confirmed a previously unknown maternity colony and documented a southerly range expansion for the species in Arkansas. We also tracked an individual bat to Oklahoma, representing the first confirmed summer use by female Indiana Bats in Oklahoma. Bats used 9 different tree species that we categorized as staging, migration, layover, or arrival roosts. The results of this study provide valuable regional information for the southwestern periphery of the species' range and facilitates conservation and management decisions made by natural resource agencies across the state of Arkansas.
Clay models are a popular technique for studying predation in nature due to their ease of deployment and minimal disruption of natural processes, but a drawback is the ambiguity of identifying predators based on bite marks. However, it is possible to amplify and sequence environmental DNA (eDNA) from these bite marks and to identify the predators responsible for attacking models. In this study, we sought to test the effectiveness of using eDNA from clay models as a means of identifying predators. We deployed in the field molded clay models that resemble Plethodon ventralis (Southern Zigzag Salamander). We then extracted eDNA from visible bite marks, amplified and sequenced the 12S rRNA mitochondrial locus on an Illumina MiSeq, and used BLAST to determine the identity of representative sequences. We identified likely predators as Procyon lotor (American Raccoon), Didelphis virginiana (Virginia Opossum), Turdus migratorius (American Robin), and Tamias striatus (Eastern Chipmunk). We believe that this technique is helpful for adding a layer of specificity to predation studies using clay models, albeit with a few potential pitfalls that we discuss.
Aratus pisonii (Mangrove Tree Crab), an arboreal crab local to neotropical mangrove forests, has increasingly been observed in salt marshes north of its historically documented range. Vertical structures, like docks and break walls, are known to serve as habitat alternatives to mangrove trees, and may therefore facilitate the spread of Mangrove Tree Crabs in suboptimal salt marsh habitat. However, the role intertidal woody habitat plays in assisting the spread of this species has not been investigated. A survey of built and woody habitats on Sapelo Island, GA, revealed multiple Mangrove Tree Crab year classes at built sites, but near total absence in woody habitats. This study also offers the northernmost evidence for reproduction for this species, and it presents the first evidence of a Mangrove Tree Crab in woody habitat north of the mangrove range.
I conducted surveys of breeding birds in the central business districts of 10 small cities and towns in the northern Pee Dee region of North Carolina and South Carolina from 13 April to 7 May 2023 (25 consecutive days) to examine if this regional study would be concordant with earlier studies conducted at Rockingham, NC. I used a modification of the spot-mapping method for those I considered common species: if there were 3 or more territories (≥ 3.0 T), I only designated it as 3 territories except for Turdus migratorius (American Robin). I tallied the exact number of territories (= 0.5–2.5 T) for less common species. I documented 32 territorial species (27 native suburban adapters, 5 exotic urban invaders) in the 10 small cities and towns. Average species richness across all towns was 16.4 (min–max = 11–19) and was not correlated with plot size. The most abundant and widespread species were resident habitat generalists (present in every town): 3 suburban adapters (Thryothorus ludovicianus [Carolina Wren], Mimus polyglottos [Northern Mockingbird], and Cardinalis cardinalis [Northern Cardinal]) and 3 urban invaders (Sturnus vulgaris [European Starling], Passer domesticus [House Sparrow], and Haemorhous mexicanus [House Finch]); Zenaida macroura (Mourning Dove) was absent only from downtown Wadesboro. The 13 least common species (5 residents, 8 Neotropical migrants) each had territories in 3 or fewer towns and had fewer than 3 territories in those towns. The 3 other Neotropical migrants (Chaetura pelagica [Chimney Swift], Myiarchus crinitus [Great Crested Flycatcher], and Dumetella carolinensis [Gray Catbird]) nesting on these plots were common species (more abundant and widely distributed). Results from this regional study in 2023 in 1 habitat type were generally concordant with earlier results from Rockingham. Dissimilarities in species composition among towns as measured by pairwise Jaccard distances increased with distance between towns in the northern Pee Dee region. American Robin and Quiscalus quiscula (Common Grackle) continued to be absent from Rockingham in 2023. However, American Robins nested in 7 other towns, and Common Grackles nested in 2 towns (Laurinburg, Maxton); the latter species only nested in colonies in low exotic vegetation.
Modeling population dynamics in response to various threats or potential management actions has become an increasingly common aspect of conservation programs for imperiled species. However, these models typically require a detailed understanding of various demographic processes that are often challenging to quantitatively assess. We combined data from the published literature (n = 4) with data collected from preserved specimens (n = 6) to model the relationship between female body size and clutch size in Ambystoma cingulatum (Frosted Flatwoods Salamander). We found a positive effect of body size on clutch size (z-score = 9.4, P < 0.001). This relationship can now be incorporated into ongoing efforts to model the population dynamics of flatwoods salamanders, reducing uncertainty and improving stakeholders' ability to make management decisions for this imperiled species.
Predation can play a significant role on survival during migration as birds find themselves competing for resources in unfamiliar habitats. Here we describe the first documented observation of a Buteo platypterus (Broad-winged Hawk) predating an Archilochus colubris (Ruby-throated Hummingbird) during autumn migration. To our knowledge, this is the first documented record of any Buteo sp. hawk predating any Trochilidae (hummingbird). While predation on hummingbirds likely represents a minor source of mortality, identifying sources of predation and mortality is important in understanding the risk of migration for any species.
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