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Abundance, diversity, and richness of herpetofaunal species were compared between burned and unburned bottomland hardwood stands at Di-Lane Plantation Wildlife Management Area (WMA) in Burke County, Georgia, from July to October 2001. Two trap clusters, each consisting of a drift fence pitfall array, four coverboards, and three polyvinyl chloride (PVC) pipe refugia, were randomly placed within each of three burned and three unburned stands. Habitat variables were measured within a 0.04-ha circular plot centered on each trap cluster. A total of 346 individuals, representing 21 species, was captured in 348 array nights. Amphibian abundance, diversity, and richness were similar between burned and unburned stands. Reptile abundance and diversity were greater in burned stands, whereas reptile species richness was similar between burned and unburned stands. Winter burns did not significantly affect coarse woody debris volumes between burned and unburned stands and may have accounted for similar amphibian abundance, diversity, and richness. Greater reptile abundance and diversity in burned stands likely was a result of decreased ground cover providing greater thermoregulatory opportunities.
The Tallapoosa darter (Etheostoma tallapoosae) is only found in the Piedmont portion of the Tallapoosa River system which spans Georgia and Alabama. Particularly in western Georgia headwaters, the habitat of this darter is potentially threatened by human population growth. The purpose of this study was to assess the extent of genetic variation and genetic structuring of this species to determine if those populations at greatest risk are genetically unique and would thus raise conservation concerns. Mitochondrial control region and cytochrome b sequences were determined for thirteen populations spanning the length of this species' range. Phylogenetic analysis and analysis of molecular variance shows that while the populations in western Georgia headwaters are not genetically unique, the Tallapoosa darter population is subdivided into genetically divergent populations that can be designated as management units for future monitoring of the species.
The objective of this study is to investigate hydrocarbon species and amounts released by red mangrove foliage and determine if these quantities warrant future research on atmospheric chemical processing of these compounds. The field investigation took place during July 2001 at Key Largo, Florida Bay, Florida. Foliage still attached to plants was enclosed in cuvettes while air of known flow rates circulated around leaves to study hydrocarbon emissions. Cuvette air samples underwent gas chromatographic analyses to determine species and amounts of hydrocarbons released by mangrove foliage. Red mangrove foliage emits isoprene and trace amounts of the monoterpenes of α-pinene, β-pinene, camphene, and d-limonene. The mangrove flowers released these latter compounds in amounts ranging from 0.5 to 10 mg (monoterpene) per gram of dry biomass per hour. These fluxes are normalized to the foliage temperature of 30 °C. When normalized to the foliage temperature of 30 °C and light levels of 1000 µmol m−2 s−1, isoprene emission rates as high as 0.092 ± 0.109 µg (isoprene) per gram of dry biomass per hour were measured. Compared to terrestrial forest ecosystems, red mangroves are low isoprene emitters. During peak flowering periods in the summertime, however, red mangroves may emit sufficient amounts of monoterpenes to alter ground-level ozone concentrations and contribute to biogenic aerosol formation.
Lists are presented of 79 species of Florida insects, mostly wasps, that have distinctive dark red markings on a black background. Most of these species have more northern relatives (subspecies or congeners) whose markings are yellow rather than red. This apparent replacement of yellow-marked forms by red-marked forms in Florida has occurred at least 31 times in different lineages. Yellow-marked and red-marked species may be sympatric in Florida. Biogeographic details of the phenomenon are poorly known.
We studied species composition and individual abundance of copepods in the surficial aquifer northeast of Everglades National Park. We identified the spatial distribution of subsurface habitats by assessing the depth of the high porosity layers in the limestone along a canal system, and we used copepods to assess the exchange between surface water and ground water along canal banks, at levels in the wells where high porosity connections to the canals exist. Surface- and ground-water taxa were defined, and species composition was related to areal position, sampling depth, and time. Subsurface copepod communities were dominated by surface copepods that disperse into the aquifer following the groundwater seepage along canal L-31N. The similarities in species composition between wells along canal reaches, suggest that copepods mainly enter ground water horizontally along canals via active and passive dispersal. Thus, the copepod populations indicate continuous connections between surface- and ground waters. The most abundant species were Orthocyclops modestus, Arctodiaptomus floridanus, Mesocyclops edax, and Thermocyclops parvus, all known in literature from surface habitats; however, these species have been collected in ground water in ENP. Only two stygophiles were collected: Diacylcops nearcticus and Diacyclops crassicaudis brachycercus.
Restoration of the Everglades ecosystem requires a mosaic of data to reveal a complete picture of this complex system. The use of copepods as indicators of seepage could be a tool in helping to assess the direction and the duration of surface and ground water exchange.
We located the endangered rock vole, Microtus chrotorrhinus, at 3 of 59 sites in mixed mesophytic forests in the southern Appalachians. Rock voles were always found within mixed mesophytic habitats characterized by yellow birch, Betula alleghaniensis, rather than mixed mesophytic habitats dominated by other tree species. We compared the tree communities, microhabitat features, and small mammals found within three groups of habitats: sites where M. chrotorrhinus was found, yellow birch habitats where M. chrotorrhinus was not found, and other mixed mesophytic habitats where M. chrotorrhinus was not found. Sites occupied by M. chrotorrhinus had greater amounts of large, rocky substrate, greater incidence of moss, and a more northwest aspect than yellow birch and other mixed mesophytic sites without M. chrotorrhinus. Moreover, sites with rock voles had larger trees and were significantly older than sites without M. chrotorrhinus. Red-backed voles, Clethrionomys gapperi, are readily sampled by live-trap methods and were significantly more abundant at sites with M. chrotorrhinus, and may thus be a promising indicator species. Our results suggest that mixed mesophytic forests, especially older stands dominated by yellow birch and rocky substrate, should be managed with care to preserve M. chrotorrhinus habitat.
We present a case study from three topographically distinct stands in an old-growth cross timbers forest in north central Oklahoma. We determined the primary mode of reproduction, i.e., sprouting versus seedling, and population dynamics of small Quercus marilandica and Q. stellata reproduction (≤ 1 m height) in relation to previous disturbance events and changes in site conditions. Approximately 99 percent of the reproduction were of sprout origin and most were stump sprouts (root crown diameter > 5 cm). Surprisingly, root sprouts were an important component of reproduction across stands, comprising 24 and 30 percent of stems for Q. marilandica and Q. stellata, respectively. Mode of reproduction varied by stand, with seedling sprouts (root crown diameter ≤ 5 cm) occurring more frequently on the most xeric site. Stem growth rates increased from xeric to mesic stands and were highest for stump sprouts. Stem longevity was similar across stands and mode of reproduction and was probably limited by low available light. Despite the relatively short life span of aboveground stems (x̄ ∼6 years), tap-roots of seedling sprouts were capable of prolonged persistence (x̄ ∼20 years) through recurrent dieback and sprouting. Stem age structure indicated disturbance encouraged sprouting, as evidenced by increasing populations following fire and declining densities in the absence of perturbation. Seedling establishment for both species appeared to be episodic, as determined by age of tap-roots. Establishment by acorns probably provides a minimal input to oak populations on a yearly basis, but is an important component in the auto-accumulation of oak reproduction over time.
We sampled a population of two species of hylid treefrogs using 90 vertical ground-placed PVC pipes of 3 diameters positioned along a 1500-m transect at a forest-open pond ecotone in north-central Florida in order to identify potential capture biases. We recorded 1,981 treefrog observations (778 unmarked, 1,203 recaptures) in 8 months. Our results identified species-specific seasonal and weather-related variation in capture by pipe diameter and pipe location. These biases may limit the usefulness of this sampling technique when monitoring long-term treefrog population status and trends.
Arthropods compose a large proportion of biological diversity and play important ecological roles as decomposers, pollinators, predators, prey, and nutrient cyclers. We sampled ground-occurring macroarthropods in intact gaps created by wind disturbance, in salvage-logged gaps, and in closed canopy mature forest (controls) during June 1998–May 1999 using drift fences with pitfall traps. Basal area of live trees, shade, and leaf litter coverage and depth were highest in controls and lowest in salvaged gaps. Coarse woody debris (CWD) cover was greater in intact gaps than in salvaged gaps or controls, but decay was more advanced and CWD had less bark in controls than gaps. We captured 2,390 grams (dry biomass) of > 28,000 macroarthropods in 21 orders and 66 identified families. Among orders, Coleoptera (36.4%), Hymenoptera (12.2 %), Orthoptera (11.7%), Araneae (7.1%), Julida (5.9%), Spirobolida (5.7%), and Scolopendromorpha (5.5%) were numerically dominant, whereas Coleoptera (44.0%), Spirobolida (19.9%), Orthoptera (12.8%), Julida (6.8%), and Scolopendromorpha (5.0%) composed the majority of dry biomass. Total macroarthropod abundance and biomass were greater in forested controls than in intact or salvage-logged gaps, and was highest in summer, followed by fall, then spring, and lowest in winter. Differences among treatments were attributable to a higher abundance of Carabidae, Julida, Scolopendromorpha, Spirobolidae, and Araneae in forested controls than in gaps. Sclerosomatidae and Gryllidae were more abundant in salvaged gaps than in intact gaps or controls. Overall, mid-sized macroarthropods were more abundant than small (< 5 mm) or large (≥ 30 mm) macroarthropods, but those ≥ 15.0 mm were more abundant in the controls. Small macroarthropods were most abundant in fall and winter, but those ≥ 5.0 mm were most abundant in summer and fall. Important questions that remain include whether reductions in macroarthropod numbers and biomass at the levels observed are likely to adversely impact vertebrate predators, and at which scales do impacts become a conservation issue.
Yellow jackets (Hymenoptera: Vespidae) are attracted to the typically ant-dispersed seeds of trilliums and will take seeds from ants in the genus Aphaenogaster. To determine if yellow jacket, Vespula maculifrons (Buysson), presence interferes with seed foraging by ants, we presented seeds of Trillium discolor Wray to three species (A. texana carolinensis Wheeler, Formica schaufussi Mayr, and Solenopsis invicta Buren) of seed-carrying ants in areas where vespids were present or excluded. We found that interspecific aggression between yellow jackets and ants is species specific. Vespid presence decreased average foraging time and increased foraging efficiency of two of the three ant species studied, a situation that might reflect competition for a limited food source. We also found that yellow jackets removed more seeds than ants, suggestive that vespids are important, albeit underestimated, components of ant-seed mutualisms.
Procambarus (Ortmannicus) verrucosus Hobbs, first identified from specimens collected in Alabama south of Tuskegee in the Alabama River drainage, has been collected from five locations in two Georgia counties in the Chattahoochee River drainage. Associated crayfish species and a possible ecological equivalent are identified. Under laboratory conditions, P. verrucosus specimens reproduced from May through August. It appears that the Georgia range of this species may be quite limited, rendering this a species of possible conservation concern.
Hellbender salamander (Cryptobranchus alleganiensis) populations have received considerable attention over the last few decades and recent studies show declines. We compared C. alleganiensis populations and habitat characteristics of the Little River (LR) in the Great Smoky Mountains National Park (GSMNP) of Tennessee, with those of the North Fork of the White River (NFWR), Missouri. We also compared the results of two different sampling methods for obtaining small individuals < 20 cm total length (TL) and gilled larvae. There was no significant difference in the frequency of larvae and adults in LR. There were highly significant differences in the frequency of larvae and adults in the NFWR population and in the proportion of larvae and adults between LR and NFWR. The stream bottom substrate, especially the deep gravel beds of the NFWR, provided a more secure larval habitat than in the LR. We believe this secure larval habitat was a major factor in maintaining large adult populations in NFWR. The less secure larval habitat within the LR makes larvae more susceptible to capture, and coupled with reduced crayfish populations, translates to fewer adult C. alleganiensis. Larvae were more efficiently collected by skin-diving than wading and turning rocks in these habitats. With the exception of the LR population, which is composed of 48% gilled or gilled sized larvae, all recorded populations are almost entirely composed of adult and sub-adult age groups and small larvae, especially gilled larvae are either uncommon or unknown.