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Predation on Notophthalmus viridescens viridescens (Red-spotted Newt) is rare due to their toxic skin excretions, which provide chemical defense against potential predators. Here we document the occurrence of the Red-spotted Newt in the stomach contents of Lepomis macrochirus (Bluegill) and L. auritus (Redbreast Sunfish), common sunfishes within an urban watershed in Columbus, GA.
I report here the first documentation of Aphelocoma coerulescens (Florida Scrub-Jay) nesting in a human-made structure. A pair of color-banded Florida Scrub-Jays built a nest atop an air compressor, which was sheltered from the elements by wooden latticework and a plywood roof, in a suburban neighborhood in Charlotte County, FL. More attention is warranted towards the study of nest-site selection and nesting success of Florida Scrub-Jays in the suburbs and other atypical habitats where they commonly occur.
Data from recently discovered daily-work logs of US Forest Service (USFS) researcher Russell R. Reynolds enabled me to clarify a study I published a decade ago on a 1930s-vintage unmanaged, second-growth Pinus (pine)—hardwood stand in southeastern Arkansas. Though still too vague to reveal every detail, Reynolds' work logs confirmed a number of assumptions in the original paper and provided me with the background information to herein describe a more precise sampling framework for this 1930s-era study plot.
On 24 February 2014, commercial fishers caught an unusually large Hypophthalmichthysnobilis (Bighead Carp) from an oxbow lake in northwestern Mississippi. We examined it to determine age, gonadal development, and fecundity. The specimen was 1316 mm total length, 49.7 kg, and 11 years old. It had asymmetric ovaries that collectively represented 15.7% of the body weight, with an estimated 1.9 to 2.7 million eggs, ∼40% of which were mature. The data we collected for size, age, and fecundity were all at or near maximum values known for the species. This specimen demonstrates that for life-history studies and demographic models to be representative of introduced populations, rare or hard-to-catch large specimens are required due to their influence on estimates of longevity, mortality, and fecundity.
GULF OF MEXICO NATURAL HISTORY AND THE DEEPWATER HORIZON OIL SPILL SPECIAL ISSUE SERIES
During the Deepwater Horizon incident in 2010, ∼1.8 million gallons of Corexit® dispersants were approved for use directly onto the released oil. Callinectes sapidus (Blue Crab) megalopae are pelagic and, therefore, likely to be one of the first organisms exposed to spilled oil and applied dispersants in open-ocean and nearshore waters. In this study, we examined acute toxicity of Corexit 9500, Corexit 9527, and MicroBlaze® (a microbial surfactant) alone and in combination with crude oil. We adapted methods from the established 48-h copepod toxicological assay and exposed Blue Crab megalopae for 48 h to varying dosages of each treatment. Oil treated with dispersant was more toxic than either oil or dispersant alone (48-h LC50 = 29.8 mg/L vs. 55.9 mg/L and 37.5–59.1 mg/L, respectively), and MicroBlaze was essentially non-toxic (48-h LC50: 7643 mg/L). Corexit 9527 was more toxic than Corexit 9500 both in solutions with oil and alone (48-h LC50 = 37.5 mg/L vs. 51.8 mg/L and 59.1 mg/L, respectively). Exposure to these toxicants not only induced mortality at certain dosage levels, but life-stage transitioning also seemed to be effected. The decreased ability to metamorphose, however, was not affected in a typical gradient manner, as with mortality; those that were exposed to a toxicant, overall, exhibited a decreased occurrence of metamorphosis (37% average decrease). This study provides essential baseline data needed for further investigations to determine optimal dosing of dispersants and balancing of dispersant use and dosage with anticipated crab-fishery impacts.
Cyzicus mexicanus (Mexican Clam Shrimp) is a small crustacean with a bivalve carapace. It was previously known from freshwater vernal pools in 18 US states, 2 Canadian provinces, and numerous Mexican states prior to our 2010 discovery in Shelby County, AL. This new state record extends the range of the Mexican Clam Shrimp farther into the southeastern US than previously documented.
Microstegium vimineum (Japanese Stiltgrass) is an invasive, annual C4 grass that frequently forms dense populations along roads in the eastern US. We examined data from a survey that included 768 forested sites in western North Carolina, and carried out a transplant experiment to test (1) if the distribution of Japanese Stiltgrass is associated with roads and (2) if roadsides differ from forest interiors in terms of the frequency, abundance, and individual vigor of the species. Japanese Stiltgrass abundance was positively associated with total road length within watersheds. The species was much more common and abundant on roadsides than in forest interiors. Greenhouse-established individuals of Japanese Stiltgrass that we transplanted onto roadsides grew larger than those we transplanted in forest interiors. The 2 groups had similar survival rates. Our results suggest that roads promote the spread of Japanese Stiltgrass and that individuals and populations are more robust on roadsides than in forest interiors. However, the species can grow in forest interiors, suggesting its lower abundance and size there may result from limitations in dispersal, germination, or resource acquisition.
The substrata of fluvial systems can be altered by human disturbance in watersheds. This disturbance often results in a reduction of habitat diversity and subsequent reductions in species diversity. Restoration efforts in impacted areas require a thorough understanding of the characteristics of exemplary stream habitat in the region as well as habitat requirements of taxa targeted by specific restoration efforts. The Little Coal River, WV, has historically been disturbed by various land-use practices resulting in near homogeneity of the riverbed substratum such that it is composed almost everywhere primarily of fine-particle or sand-substrate classes. Restoration of an 8-km section of the Little Coal River was attempted with the installation of a series of natural material instream-structures. We monitored the riverbed substratum, including sediment size-class data, prior to and after installation of these structures for a 2-year period to evaluate their effectiveness in restoring overall habitat heterogeneity. Our GIS analysis of the data suggested that approximately 80% of the riverbed substratum was composed of fine-particle or sand substrate classes prior to the natural material structure addition. After 2 years, these 2 substrate classes had decreased by nearly 25%, suggesting that restoration efforts reduced the overall percent composition of fine-particle and sand-substrate classes and increased overall habitat heterogeneity. Our analysis of these data indicate that the natural material instream structures installed in the Little Coal River achieved the objective of promoting downstream movement of some fineparticle and sand substrate that characterized the system (i.e., via sediment transport) and increased substratum heterogeneity.
Forested wetlands represent some of the most distinct environments in the Lower Mississippi Alluvial Valley. Depending on season, water in forested wetlands can be warm, stagnant, and oxygen-depleted, yet may support high fish diversity. Fish assemblages in forested wetlands are not well studied because of difficulties in sampling heavily structured environments. During the April–July period, we surveyed and compared the water quality and assemblages of small fish in a margin wetland (forested fringe along a lake shore), contiguous wetland (forested wetland adjacent to a lake), and the open water of an oxbow lake. Dissolved-oxygen levels measured hourly 0.5 m below the surface were higher in the open water than in either of the forested wetlands. Despite reduced water quality, fish-species richness and catch rates estimated with light traps were greater in the forested wetlands than in the open water. The forested wetlands supported large numbers of fish and unique fish assemblages that included some rare species, likely because of their structural complexity. Programs developed to refine agricultural practices, preserve riparian zones, and restore lakes should include guidance to protect and reestablish forested wetlands.
Rynchops niger (Black Skimmer) is a colonial-nesting seabird that nests on open, sandy or gravel beaches. In densely populated Pinellas County, FL, Black Skimmer colonies often occur on municipal beaches where there is relatively little mammalian predation, but intense predation by Corvus ossifragus (Fish Crow) and Leucophaeus atricilla (Laughing Gull). In 2013, a previously successful Black Skimmer colony experienced high egg-loss due to Fish Crow predation. To determine if effigies would decrease egg depredation in the middle of the breeding season, we monitored the number of crow-foraging passes over the colony and number of eggs taken before and after we placed 6 crow effigies among the nests. During 36 hours of monitoring, we observed 83 foraging passes and 28 eggs being taken by Fish Crows. Neither foraging passes nor eggs taken decreased after the placement of the effigies, and the Black Skimmers abandoned their nests. Future research should focus on other methods to limit nest predation after the onset of the breeding season.
We collected 18 Anaxyrus terrestris (Southern Toad) in March and May 2014 and July 2015 from Topsail Hill Preserve State Park, Walton County, FL, and examined them for helminth and arthropod parasites. Fourteen toads (78%) were infected or infested with parasites as follows: 2 (11%) with Megalodiscus temperatus, 1 (6%) with tetrathyridia of Mesocestoides sp., 3 (17%) with Cylindrotaenia americana, 2 (11%) with 3rd-stage larval Physaloptera sp., 9 (50%) with Cosmocercoides variabilis, 10 (55%) with Oswaldocruziapipiens, and 2 (11%) with larval Hannemania hegeneri chigger mites. We observed multiple infections/infestations of helminths and/or arthropods in 7 (39%) of these hosts. Herein, we report 5 new host and 2 new geographic-distribution records.
Laurel wilt disease (LWD), caused by the fungus Raffaelea lauricola and transmitted by Xyleborus glabratus (Redbay Ambrosia Beetle [RAB]), has killed millions of Persea borbonia (Redbay) trees throughout the southeastern Coastal Plain. Laurel wilt also has been detected in Sassafras albidum (Sassafras) in widely dispersed locations across the southeastern US. We established long-term laurel wilt disease-progression plots in Redbay and Sassafras stands in southeastern Georgia and monitored them through 4 years to document mortality rates and investigate long-term effects of LWD on Redbay and Sassafras survival and regeneration. Laurel wilt disease killed 87.3% of Redbay and 79.5% of Sassafras trees in the plots. The time from initial LWD detection to inactivity (no new mortality) in Redbay stands ranged from 1.1 to 3.6 years, with rate of disease progression positively related to host-tree size and abundance. Larger trees died at a higher rate in both Redbay and Sassafras stands, and mortality curves were similar for both species. All diseased Redbay trees died to the ground level, but the majority produced persistent below-ground basal sprouts, rapidly providing potential replacement stems. Few below-ground basal sprouts were observed on Sassafras trees killed by LWD, but over a quarter had epicormic shoots that survived up to several years after infection, and small trees remained alive on most sites, suggesting some level of tolerance to LWD. Substantial numbers of RAB were only captured in baited traps located adjacent to plots in an advanced-active stage of disease progression with abundant infested trees, both in Redbay and Sassafras stands. However, lingering presence of small numbers of RAB in post-epidemic areas and scattered LWD mortality in small-sized Redbay regeneration sprouts and seedlings suggest that secondary disease cycles may occur as Redbay trees there reach greater numbers and size in the future. Documentation of RAB and LWD spreading in Sassafras in the absence of Redbay supports concern that LWD will continue to spread into areas with abundant, large Sassafras trees, which would increase the probability that RAB and LWD will expand into extensive populations of other laurel species present in the western US and Central and South America.
Percina aurolineata (Percidae: subgenus Hadropterus) (Goldline Darter) is a federally threatened species that currently exists in disjunct populations in the Coosawattee River, GA, and Cahaba River, AL. These 2 Mobile Basin drainages are home to considerable endemism, and these disjunctions may actually represent cryptic diversity within Goldline Darter. We examined sequence data from the mitochondrial cytochrome b gene (cyt b) and nuclear recombination-activation gene exon 1 (RAG1) from specimens (n = 34) collected from 4 streams in the Coosawattee River drainage and 4 streams in the Cahaba River drainage for the purpose of assessing phylogenetic structure and genetic divergence to test the hypothesis that the disjunct populations of Goldline Darter represent a single species. Specimens from each of the rivers sampled were not resolved as a clade in any analysis. For cyt b, divergence within the Coosawattee was 0.8%, divergence within the Cahaba was 0.3%, and net divergence between populations was 0.4%. For RAG1, divergence within the Coosawattee was 0.0%, divergence within the Cahaba was 0.1%, and net divergence between populations was 0.0%. We detected a unique allele for RAG1 with a frequency of 0.559 in the Cahaba specimens. No clades were resolved that contained specimens representative of only one locality and the difference between mean divergence among and within rivers was low; thus, these results support the hypothesis that the disjunct populations of Goldline Darter represent a single species and an evolutionarily significant unit. The divergence of allele frequencies among Cahaba and Coosawattee for RAG1 qualifies them as separate management units, and future conservation efforts should manage them as such.
Bats in the genus Corynorhinus possess a suite of morphological characters that permit them to effectively use both gleaning and aerial-hawking foraging strategies to capture Lepidoptera. Consequently, they occupy a specialized feeding niche within North American bat assemblages and are of particular interest for dietary studies. We collected fecal pellets from a colony of C. rafinesquii (Rafinesque's Big-Eared Bat) at Mammoth Cave National Park during August–October 2011 and amplified cytochrome-c oxidase subunit 1 fragments of prey from these pellets. We used the Barcode of Life Database to identify prey, and evaluated the size of prey species based on published values. The mean wingspan of prey we recorded from our samples was smaller than average values reported for Rafinesque's Big-Eared Bat using traditional methods (P ≤ 0.01), suggesting that surveys of culled insect parts beneath roosting sites may lead to biased estimates of the size and breadth of prey species eaten by gleaning bats. Mean wingspan of lepidopteran prey consumed by Rafinesque's Big-Eared Bat in our study was larger (P ≤ 0.01) than values reported for the Myotis septentrionalis (Northern Long-Eared Bat ), which is a smaller, sympatric gleaner in eastern North America. Further, comparisons of our diet data with abundance of prey suggest macrolepidopteran taxa are consistently consumed by Rafinesque's Big-Eared Bat to greater degree than microlepidotera. Our findings suggest that North American Corynorhinus consume a wider range of sizes and species of Lepidoptera than previously reported in studies based solely on identification of culled prey-wings beneath feeding roosts.
This 4-y study monitored 6 sites located in the upper watershed of the Strawberry River, AR, where multiple types of best-management practices (BMPs) were implemented in an attempt to alleviate the impacts of cattle grazing on adjacent waterways. The water-quality variables we assessed included turbidity, total suspended solids (TSS), and concentrations of NO2-, NO3-, PO43-, Escherichia coli, and chlorophyll-a. We calculated the average annual sediment loading for comparison to published acceptable total-maximum annual load (TMAL). The mean values detected for most parameters that we assessed were within acceptable state limits and reference-stream values for the Ozark Highlands ecoregion. Following BMP implementation, all sites showed significant increases in at least one variable, and the concentration of E. coli for 3 of the sampling locations exceeded the maximum allowable concentration. The estimated sediment loading was within the accepted TMAL. We conclude that implementation of BMPs was not effective at improving water quality during the time-frame of our study. Our results suggest that maintaining desired water quality in this watershed may require the use of BMPs that are: (a) specifically targeted to limit the parameters of concern (e.g., E.coli), and (b) implemented in specific locations of concern rather than dispersed throughout the watershed. We also offer suggestions for future studies of this type to improve the study design in an effort to more efficiently and effectively determine the impact of BMP implementation.
An unknown population of Medionidus simpsonianus (Ochlockonee Moccasinshell) was discovered in the lower Ochlockonee River downstream of Jackson Bluff Dam in 2014. This discovery confirms that the species is extant, extends its known range by nearly 100 rkm, and represents only the second known collection of this species in the lower Ochlockonee River Basin. Ochlockonee Moccasinshell is endemic to the Ochlockonee River Basin (ORB) in Florida and Georgia. It was historically known from 9 locations in the upper ORB upstream of Lake Talquin and from 1 record in the lower ORB downstream of Jackson Bluff Dam. Collections of Ochlockonee Moccasinshell decrease in regularity after 1950, and the last record of a live individual was 1995. We surveyed 55 sites downstream of Jackson Bluff Dam in a reach of river having received little effort in the last 20 years. We employed visual/tactile searches using mask and snorkel from shore to a depth of 2.5 m and found 22 live individuals of Ochlockonee Moccasinshell at 9 locations from 47–65 river km (rkm) downstream of Jackson Bluff Dam. Further survey effort is needed to update the status and range of Ochlockonee Moccasinshell and other freshwater mussel populations of the lower ORB.
Bees play a key role in agriculture, directly affecting the production of over one-third of the human food supply. Apis mellifera (Honey Bee), the chief pollinator used in commercial agriculture, has been in decline. Reliance on a single species for the pollination of a significant portion of commercial agriculture can be dangerous. One alternative to using Honey Bees as the main commercial pollinator is native bees. In this study, we document native bee species diversity and abundance throughout the 2010 growing season (March through October) at 4 North Georgia Malus domestica (Apple) orchards. The 4 study sites included 2 large-scale orchards (Mercier Orchards and Hillside Orchards) and 2 small-scale orchards (Mountain View Orchards and Tiger Mountain Orchards). A comprehensive sampling methodology using pan-traps, vane-traps, malaise traps, and sweep-netting was performed at each orchard on 8 separate collection days. A total of 1817 bees were identified to species. These bees comprised 128 species in 28 genera in 5 families. Several native bee species were quite common and widespread at all 4 orchards. These native bee species included: Andrena crataegi, A. perplexa, Lasioglossum imitatum, L. pilosum, and Xylocopavirginica (Eastern Carpenter Bee). Andrena crataegi was identified as the best native bee candidate for Apple pollination in North Georgia due to its abundance, wide-spread distribution in Georgia Apple orchards, and its life-history characteristics.
Back-calculation of length-at-age from otoliths and spines is a common technique employed in fisheries biology, but few studies have compared the precision of data collected with this method for catfish populations. We compared precision of back-calculated lengths-at-age for an introduced Ictalurus furcatus (Blue Catfish) population among 3 commonly used cross-sectioning techniques. We used gillnets to collect Blue Catfish (n = 153) from Lake Oconee, GA. We estimated ages from a basal recess, articulating process, and otolith cross-section from each fish. We employed the Frasier-Lee method to back-calculate length-at-age for each fish, and compared the precision of back-calculated lengths among techniques using hierarchical linear models. Precision in age assignments was highest for otoliths (83.5%) and lowest for basal recesses (71.4%). Back-calculated lengths were variable among fish ages 1–3 for the techniques compared; otoliths and basal recesses yielded variable lengths at age 8. We concluded that otoliths and articulating processes are adequate for age estimation of Blue Catfish.
This study provides the first comparison of historical (1979–1994) and recent (2012–2013) breeding distributions of Lanius ludovicianus (Loggerhead Shrike) at a single location in southeastern North America. I conducted roadside and area searches for Loggerhead Shrikes in the spring (April—early June 2012 and late March—early May 2013) in Richmond County, NC, and small areas of 4 adjacent counties. Most of the study area is within the Sandhills, a subregion of the Coastal Plain. I documented a total of 44–45 breeding territories in 2012–2013, of which 36–38 (82–84%) were in the Sandhills, where I estimated the recent breeding density to be 3.2–3.4 pairs/100 km2. In both years, a smaller percentage of confirmed historic breeding sites were occupied in the Piedmont compared to the Sandhills portion of the study area, and the Piedmont had a much lower breeding density (0.6–0.8 pairs/100 km2). Sixteen of 22 (73%) confirmed historical breeding sites were occupied (n = 10) or retained suitable breeding habitat (n = 6) for Loggerhead Shrikes in 2012–2013. The breeding population in the sampled portion of the Sandhills has apparently declined slowly yet is still fairly stable, an unexpected result based on sharp declines of Loggerhead Shrikes in the Atlantic Coastal Plain for over the past 40 years as documented by coarse-scale surveys (breeding bird surveys, Christmas bird counts, spring bird counts). This study reaffirms the importance of conducting fine-scale surveys to produce a precise estimate of a persistent population in a geographically restricted area.
For amphibian species suspected of undergoing enigmatic declines, it is important to determine the effort required to confidently establish species absence. Desmognathus auriculatus (Southern Dusky Salamander) has purportedly gone from being quite common throughout the southeastern US Coastal Plain to now being enigmatically rare. We used repeated standardized surveys of 5 historically occupied streams and their adjacent riparian zones between 2007 and 2010 to estimate detection rate of Southern Dusky Salamanders. We detected Southern Dusky Salamanders at 3 of 5 historic sites. Mean detection rate across streams known to be occupied at least once during the study was moderately low (mean ± 1 SE = 0.20 ± 0.12 for a double-sampled 50-m survey), improved at 2 sites with increasing time since drought, and varied among streams. For comparison, we evaluated detection rates of several other stream salamanders and found those rates to range from 0.37 (± 0.07) for Eurycea quadridigitata (Dwarf Salamander) to 0.08 (± 0.01) for Siren intermedia (Lesser Siren). Based on mark—recapture along a 200-m section of stream and the associated riparian habitat at the site where Southern Dusky Salamanders were most often detected, we estimated 43 (± 15) and 97 (± 161) individuals to be present February—May 2009 and October 2009–May 2010, respectively. Despite abundant adults, Southern Dusky Salamanders were the only species that we failed to detect as larvae; however, we observed many newly metamorphosed Southern Dusky Salamanders–usually under logs with saturated soil and often near entrances to crayfish burrows. Our results generally support the characterizations of Southern Dusky Salamanders as having become enigmatically uncommon. Because landcover change in the study area has been minimal, we suspect habitat damage from Sus scrofa (Feral Pig) may be responsible for the variation in Southern Dusky Salamander presence and abundance among sites. Because of the low detectability of Southern Dusky Salamanders, future work to identify factors driving Southern Dusky Salamander distribution and abundance will require intensive sampling at sites to provide robust estimates of occupancy or population size.
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