Of American black bears (Ursus americanus) killed by vehicles in Florida from 1976 to 2003, 45% were from the population in central Florida centered in Ocala National Forest (ONF). This area contains ...8 of the state's 15 most severe roadkill areas. More bears were killed along State Road 40 (SR-40), which bisects this population, than along any other road in the state. Interest in widening this road provided an opportunity to document bear movements and the frequency with which they crossed SR-40 when average annual daily traffic (AADT) volume was at each of two levels: 5,100 vehicles per day (vpd) in ONF and 15,700 vpd in the adjacent community of Lynne. We analyzed the locations of 86 radiocollared bears (33 F∶40 M in ONF and 13 F in Lynne) and monitored them 1–3 times/week from May 1999 through May 2003. Forty-eight bears crossed SR-40 a minimum of 388 times. ONF female bears were 2.9 times more likely than Lynne females to cross SR-40, but this rate was only marginally significant. ONF male bears were 4.3 times more likely to cross SR-40 than ONF females and 12.3 times more likely to cross than were Lynne females. We documented the mortality of 7 radiocollared bears by vehicles, 4 males in ONF and 3 females in Lynne. There were no deaths of ONF females due to vehicular collisions, but female bears in Lynne died from vehicle collisions at near the rate of ONF male bears. We recommend that a minimum of 6 crossing structures be incorporated along this highway to reduce the effect of highway expansion on the Ocala population of Florida black bears.
Palaeogene dolostones from the sub-surface of Florida are ideal for the study of dolomite maturation because they record the early stages of a secondary dolomite overprint without destruction by ...later diagenetic overprints. Two distinct dolomite textures occur in the dolostones of the Upper Eocene Ocala and Lower Oligocene Suwannee limestones in west-central Florida: a porous and permeable sucrosic dolomite and a less porous and relatively impermeable indurated non-sucrosic dolomite. In both textures, the initial matrix dolomite is dully luminescent, whereas the secondary overprint is dominantly luminescent cement in the Suwannee and only neomorphic luminescent dolomite in the Ocala. The abundance of luminescent dolomite ranges from 2% to 38%, which translates to 1·6 km³ of material in the Suwannee and 13·5 km³ in the Ocala. Extrapolated trace-element contents (Sr and Na) and δ¹⁸O values for the matrix and luminescent end-members indicate a marine origin for the matrix dolomite in both units, and a freshwater-seawater mixing-zone origin for the secondary luminescent dolomites. The δ¹⁸O values indicate that a saline, middle mixing-zone environment overprinted the Suwannee but a more dilute mixing zone affected the Ocala. Fluid-fluid mixing models constrained by modern Floridan aquifer hydrochemistry and extrapolated ⁸⁷Sr/⁸⁶Sr values of the luminescent phases indicate that the mixing zones operated during the Late Miocene to Pliocene in the Ocala and affected the Suwannee in the Pliocene. The luminescent Suwannee mixing-zone cement reduced porosity up to threefold and permeability up to 100-fold, which converted many sucrosic dolomites to indurated dolomites. By contrast, the neomorphic luminescent Ocala dolomite did not have an appreciable impact on the maturations. Although freshwater-seawater mixing zones were not the sites of the initial dolomitization, the mixing-zone environment did dramatically overprint and mature the regionally widespread dolomites of the Ocala and Suwannee limestones. This maturation occurred shortly after formation of the proto-Floridan aquifer; the timing suggests the matrix dolomites were 'ripe' for alteration and that the only prerequisite for mixing-zone dolomite is pre-existing dolomite substrates to reduce kinetic barriers. In contrast to recent claims, the results of this study demonstrate that mixing zones can be effective in forming regionally significant amounts of secondary dolomite and influencing the petrophysical maturation of dolomite bodies.
Eogenetic karst lies geographically and temporally close to the depositional environment of limestone in warm marine water at low latitude, in areas marked by midafternoon thunderstorms during a ...summer rainy season. Spring hydrographs from such an environment in north‐central Florida are characterized by smooth, months‐long, seasonal maxima. The passage of Hurricanes Frances and Jeanne in September 2004 over three field locations shows how the eogenetic karst of the Upper Floridan Aquifer responds to unequivocal recharge events. Hydrographs at wells in the High Springs area, Rainbow Springs, and at Morris, Briar, and Bat Caves all responded promptly with a similar drawn‐out rise to a maximum that extended long into the winter dry season. The timing indicates that the typical hydrograph of eogenetic karst is not the short‐term fluctuations of springs in epigenic, telogenetic karst, or the smoothed response to all the summer thunderstorms, but rather the protracted response of the system to rainfall that exceeds a threshold. The similarity of cave and noncave hydrographs indicates distributed autogenic recharge and a free communication between secondary porosity and permeable matrix—both of which differ from the hydrology of epigenic, telogenetic karst. At Briar Cave, drip rates lagged behind the water table rise, suggesting that recharge was delivered by fractures, which control the cave’s morphology. At High Springs, hydrographs at the Santa Fe River and a submerged conduit apparently connected to it show sharp maxima after the storms, unlike the other cave hydrographs. Our interpretation is that the caves, in general, are discontinuous.
One of the main populations of the Florida scrub-jay (Aphelocoma coerulescens), a federally threatened species, occurs on Ocala National Forest, Florida. We determined the nest daily survival rate ...(DSR) of 474 nests of Florida scrub-jays in stands subject to sand pine reforestation management after timber harvesting or wildfire on Ocala National Forest. We used the information-theoretic approach with logistic-exposure modeling to determine the most likely models to account for DSR for the incubation and nestling stages separately. The models consisted of 4 components (temporal, management, habitat, and helpers) with each consisting of one to several specific variables. In the incubation stage all the best models included the temporal component alone or in concert with the habitat, helpers, or habitat and helpers components. Model averaging in the incubation stage indicated support for the year and day × year in the temporal component and stand age in the habitat component. In the nestling stage, top models all included the temporal component alone or with helpers or habitat, helpers, and the interaction of habitat and helpers. Model averaging in the nestling stage showed support for the year, nest age, and to a lesser extent day in the temporal component and helpers. The management component, which consisted of no site preparation, wildfire burn, post-harvest burn, chop and seed, or seed only, had little influence on nest survival for the incubation or nestling stages. However, we identified several other management factors that may increase Florida scrub-jay populations despite having no effect on DSR. First, the proportion of Florida scrub-jay nests was significantly higher than expected in burned habitat based on habitat availability, indicating a potential preferred nesting habitat conducive to population growth. Second, incubation stage DSR with respect to stand age (habitat component) declined to stand age 10 yr and then began to increase, which may be attributed to the higher bird population in the prime habitat in the middle stand ages. The denser population may result in more competition for resources, and possibly may attract more predators, resulting in a lower DSR. Thus, although DSR may be lower at the mid-stand ages, the overall population may actually be optimal. Therefore, to increase the Florida scrub-jay population on Ocala National Forest, we recommend maintaining a mosaic of stands ≤20 yr of age and emphasizing natural reseeding and site preparation via burning.
Oyenaster oblidus, Ocalaster timucum, and Ocalaster seloyi are new genera and species of the family Goniasteridae (Asteroidea) described from the Eocene Ocala Limestone of Florida. Although the ...fossil record of asteroids is sketchy, goniasterids appear to have been important contributors to marine communities since at least the Middle Jurassic. Similarities between living goniasterids and their fossil precursors indicate that plesiomorphy and convergence have been important in family history, and as a result, taxonomic interpretation is challenging. Even partial fossil goniasterids are rare, forcing systematists to rely heavily on isolated marginal ossicles, although some authors have expressed the need for caution. Building around three new taxa, we suggest that broader approaches can aid systematic interpretation of all crown-group asteroids. We also suggest that the inevitably idiosyncratic interpretations of marginal-based systematics can be partially tested using blind evaluations.
A molecular and isotopic study of sediment cores from a sinkhole lake, Mud Lake, Florida, USA, was performed in order to relate documented changes in the regional terrestrial vegetation and water ...table over the last ∼5500 years to molecular and isotopic proxies for biological sources of organic matter to the lake sediments. Temporal shifts in the source of organic matter to the sediment, as determined by the stable carbon-isotope composition of bulk organic matter and biomarkers, correspond with previously defined regional scale transitions in forest ecosystems (
Quercus to
Pinus at ∼5500
14C yr BP and
Taxodium expansion at 2500
14C yr BP) and coincident increases in the Floridan water table. The
δ
13C values for total sedimentary organic carbon showed a shift from terrestrial and aquatic macrophyte sources (−27.8‰, in sediments dated at ∼5400
14C yr BP) within the basal peat, to a cyanobacterial-dominated sapropel (−18.1‰) at the surface. A comparison of the δ
13C values of bulk sediment and biomarkers representative of cyanobacterial and algal input (e.g. 7- and 8-methylheptadecane and the
n-alkane C
17) indicates that the present shallow lake was fully developed by ∼2400
14C yr BP. Differences among the
δ
13C values of specific biomarkers derived from vascular plants (C
29 and C
31
n-alkanes and CuO lignin oxidation products) and from cyanobacteria and algae are nearly equivalent in magnitude to the shift recorded in
δ
13C of TOC, indicating their effective use as source proxies in this system.
The neogastropod genus Conus is likely the most diverse marine animal genus, but has an Eocene to Pleistocene fossil record that remains poorly understood. We discuss the fossil record of Eocene ...Conus from Florida and recognize three species: Conus sauridens Conrad, 1833, and two new species, Conus palmerae and Conus alleni. We also re-describe C. sauridens, identify its likely synonyms, and add new information about its geographic range. The new species C. palmerae is restricted to the upper Eocene Ocala Limestone of Florida, while C. alleni new species occurs in the upper Eocene Ocala Limestone of Florida and the upper Eocene Moodys Branch Formation of Louisiana.
The Late Eocene Ocala Limestone is part of the Upper Floridan Aquifer, and in west-central Florida the Ocala forms a subregional semi-confining unit that separates underlying and overlying highly ...transmissive zones. In portions of the same area, the lower half of the Ocala is dolomitized and fractures are observed in cores. Where present, the fractures should locally enhance the hydraulic conductivity of the dolomite and could enhance vertical leakage through the semi-confining Ocala interval.
Triaxial strength tests and Brazilian Disc tensile tests were conducted on a suite of 2.5-cm diameter dolomite core plugs from five boreholes. Samples were texturally subdivided on the basis of degree of induration into three general categories: friable sucrosic dolomite with high porosity, moderately indurated dolomite with intermediate porosity, and tightly indurated dolomite with low porosity. Results indicate elevated cohesion magnitude and tensile strength as the degree of induration increases and secondarily as abundance of moldic porosity decreases. Sucrosic and moderately indurated dolomites are most likely to fracture due to their low cohesion strength, followed by tightly indurated dolomites with high moldic porosity. Tightly indurated dolomite with little or no moldic porosity is the least likely to fracture.
Degree of dolomite induration is a function of the lime precursor's depositional fabric. Thus, combining strength data with known stratigraphic patterns in depositional textures allows for prediction of mechanical units and fractured horizons in the Ocala dolomites, and provides insight into regions of potentially increased hydraulic conductivity.
Colonial metazoans that lived symbiotically with hermit-crabs create striking and distinctive fossils. Examples of such fossils recorded (Schindler and Portell, 1993) from Cenozoic deposits in ...Florida include the scleractinian coral Septastrea marylandica (Conrad, 1841) (see Darrell and Taylor, 1989), the hydrozoan Cystactinia ocalana Brooks, 1964, and the bryozoan Hippoporidra edax (Busk, 1859) recorded as H. calcarea (Smitt) by Scolaro, 1970. In all of these fossils, the symbiotic colony covers the entire external surface of a gastropod shell with a thick encrustation. Growth of the colony outwards from the shell aperture in the form of a helicospiral tube greatly extends the size of the chamber available for the hermit-crab occupant. In no known fossil examples of symbioses are the hermit-crabs preserved in situ. However, modern analogues, along with functional morphological considerations, provide good criteria for inferring that this peculiar colonial growth pattern occurred in response to the presence of a symbiotic hermit-crab, at least for examples within the Lower Jurassic-Recent range known for fossil hermit-crabs (see Walker, 1992; Taylor, 1994).
Low nutritional quality of mature plant leaves generally leads to slow growth of herbivores. Slow growth, in turn, is thought to increase the vulnerability of herbivores to their annual enemies. I ...investigated the relative importance of nutritional quality and enemy avoidance to the larvae of a pyralid moth, Omphalocera munroei, that feed almost exclusively on the old leaves of their host plant (Asimina spp.). The effect of leaf age on development rate, the importance of predators and parasitoids as mortality agents, and the interactions between leaf quality and enemy avoidance were studied in field manipulations using larvae placed on naturally growing plants. Larvae of O. munroei developed 20% more slowly on old leaves than they did not young foliage. Predators, which accounted for most of the mortality of O. munroei caterpillars, reached maximum densities at the same time that O. munroei populations peaked. Two aspects of larval feeding behavior, leaf tying and gregarious feeding, reduced the impact of natural enemies. Leaf ties built of old leaves were more effective at reducing predating than were those built of young leaves, probably because old leaves maintained their shape, while young leaves wilted, following feeding by O. munroei. The greater rigidity of old leaves, however, required that O. munroei feed in groups of at least 20 caterpillars, which could then pull the leaves together. A group size of 20 coincided with the mean size of egg masses laid by females in the field. Given a choice, larvae preferred nutritionally poor old leaves arranged to form a shelter rather than nutritionally superior young leaves without shelter, indicating that protection from enemies was more important than nutrient to the larvae. The results also suggest that slow growth need not invariably lead to greater exposure of herbivores to natural enemies.
