A biogeographical profile of the sand cockroach Arenivaga floridensis and its bearing on origin hypotheses for Florida scrub biota

Florida scrub is a xeric ecosystem associated with the peninsula's sand ridges, whose intermittent Pliocene–Pleistocene isolation is considered key to scrub endemism. One scrub origin hypothesis posits endemics were sourced by the Pliocene dispersal of arid‐adapted taxa from southwestern North America; a second invokes Pleistocene migration within eastern North America. Only one study to date has explicitly tested these competing hypotheses, supporting an eastern origin for certain scrub angiosperms. For further perspective, we conducted a genetic analysis of an endemic arthropod, the Florida sand cockroach (Arenivaga floridensis), with two aims: (1) to reconstruct the peninsular colonization and residence history of A. floridensis and (2) determine whether its biogeographic profile favors either origin hypothesis. We sequenced the cox2 mitochondrial gene for 237 specimens (65 populations) as well as additional loci (cox1, nuclear H3) for a subset of Florida roaches and congeners. Using Network and Bayesian inference methods, we identified three major lineages whose genetic differentiation and phylogeographical structure correspond with late Pliocene peninsula insularization, indicating Arenivaga was present and broadly distributed in Florida at that time. Stem and crown divergence estimates (6.36 Ma; 2.78 Ma) between A. floridensis and western sister taxa span a period of extensive dispersal by western biota along an arid Gulf Coast corridor. These phylogeographical and phylogenetic results yield a biogeographic profile consistent with the western origin hypothesis. Moreover, age estimates for the roach's peninsular residence complement those of several other endemics, favoring a Pliocene (or earlier) inception of the scrub ecosystem. We argue that eastern versus western hypotheses are not mutually exclusive; rather, a composite history of colonization involving disparate biotas better explains the diverse endemism of Florida scrub.     

Degradation of 1,3-Dichloropropene (1,3-D) in Soils with Different Histories of Field Applications of 1,3-D

Laboratory experiments were conducted to determine the mineralization rates of 1,3-dichloropropene (1,3-D) in surface and subsurface soil samples collected from three sites in Florida with different histories of 1,3-D exposure. Mineralization rates of uniformly labeled ¹⁴C-1,3-D in surface and subsurface samples collected from two of the three sites, one of which was treated with 1,3-D only once and the other which had not been treated with the chemical for 5 years, were similar to the corresponding samples collected from untreated plots, and the rates generally decreased with soil depth. Initial mineralization rates in surface and subsurface samples collected from the site that had repeatedly been treated with 1,3-D at least 6 of the past 12 years were more rapid than those in either the corresponding untreated samples or in samples collected from the two other sites. Not only were the initial mineralization rates in soil samples collected from this site greater, but also the disappearance rates of cis- and trans-l,3-D were greater than in the corresponding untreated samples. Trans-1,3-D was degraded much more rapidly in the enhanced soil than was the cis- form. In addition, no or little trans-3-chloroallyl alcohol (CAA), the hydrolysis product of trans-l,3-D, was formed; large amounts of cis-3-CAA, the hydrolysis product of cis-1,3-D, were detected. This suggest that biological hydrolysis is responsible for the hydrolysis of trans-l,3-D to trans-3-CAA in enhanced soil and chemical hydrolysis is responsible for the hydrolysis of cis- and trans-l,3-D to 3-CAA in nonenhanced soil.     

The relationship between the soil seed bank and above-ground vegetation of a coastal barrier island

Abstract. The germinable soil seed bank is described from a coastal barrier island off the northwest coast of Florida, USA. Soil samples collected from seven vegetation types, recently deposited dredge spoil and unvegetated areas in autumn 1990 and spring 1991 were placed out in greenhouse trays. 110 taxa germinated from the samples with the largest number (41) being C₃ perennial dicots. The largest number of taxa germinated from dry (57) and wet (54) swales, the fewest (one species: Heterotheca subaxillaris) from strand. Similarity of seed bank densities to above-ground species cover was low (Jaccard's Index = 0.36), not different between vegetation types, but higher in the autumn than in the following spring. Compositional gradients in the seed bank and above-ground vegetation determined using DCA ordination were highly correlated and related to distance from mean high water, and plot elevation. At the landscape scale, the seed bank provided an equally clear delineation of vegetation types to that based upon the above-ground vegetation. The seed bank of low disturbance, late-succession vegetation types (wooded dunes, swales, marshes) was well developed (high species richness, emergent density, and percentage annual species) with the exception that the large-seeded woody species (i.e. Quercus spp.) were absent from the wooded dune seed bank. By contrast, a poorly developed and transient seed bank occurred in more frequently disturbed (extensive sand movement, salt spray), early successional dredge spoil, unvegetated areas and strand. These contrasts support a general pattern of increasing seed bank development and a persistent rather than transient seed bank with decreasing disturbance frequency, increasing time since disturbance and successional maturity.     

The mating system of the tropical understory shrub Ardisia escallonioides (Myrsinaceae)

Electrophoretic analysis of progeny arrays was used to determine whether Ardisia escallonioides (Myrsinaceae). a self-compatible tropical understory shrub in south Florida, exhibits a mixed-mating system. Ten seedlings from seven to 16 maternal plants from four populations were analyzed using five polymorphic enzyme systems. Multilocus population out-crossing rates ranged from 0.39 to > 1, with three populations showing high levels of selfing. Both single and multilocus inbreeding coefficients (F) indicated excess homozygosity in seedlings but not adults for three of the four populations. Population outcrossing rate was not positively correlated with increased numbers of flowering plants. The importance of annual variation in population outcrossing rates is discussed with regard to the high temporal variability in seedling recruitment in this species.     

Host-range and cold temperature tolerance of Floracarus perrepae Knihinicki & Boczek (Acari: Eriophyidae), a potential biological-control agent of Lygodium microphyllum (Pteridophyta: Lygodiaceae)

Abstract The leaf galling eriophyid mite Floracarus perrepae is a widespread and damaging herbivore of Old World climbing fern, Lygodium microphyllum , across its native range in tropical and subtropical Asia and Australia; and was therefore selected as a candidate biological-control agent for the invasive fern in Florida, USA. The host testing of F. perrepae focused on Lygodium species from North America and the Neotropics, along with threatened or endangered ferns from Florida. Sporeling ferns were used for the initial no-choice screening and F. perrepae showed normal development on the Florida genotype of L. microphyllum with 33.0 ± 4.6 mites per marginal leaf roll gall, modest development on the North American native Lygodium palmatum with 29.0 ± 9.3 mites per roll, and minor development on six other fern species (4.0–0.3). Leaf rolls were induced only on Lygodium species and full rolls were common only on L. microphyllum . These same six non-target plant species were tested again as more mature plants in both no-choice and choice tests and F. perrepae developed only on L. microphyllum . Lethal minimum temperature and cold stress tests were also conducted on F. perrepae . These tests revealed that it would not likely establish north of USDA hardiness zone 8a (−9.5 to −12.2°C), which means it would not overlap with L. palmatum from temperate North America. Our studies conclude that F. perrepae is specific to L. microphyllum , poses little or no risk to native or cultivated ferns in North and South America, and therefore should be considered for release in Florida.     

Plasmodium (Huffia) hermani sp. n. from wild turkeys (Meleagris gallopavo) in Florida*

SYNOPSIS. Plasmodium (Huffia) hermani sp. n. is described from wild turkeys (Meleagris gallopavo Linnaeus) in Florida. It produces rounded schizonts with 6–14 nuclei arranged peripherally as a rosette and elongate, slender gametocytes with irregular margins. Asexual stages parasitize all cells in the erythrocyte series and, in heavy infections, predominantly occur in erythroblasts and their precursors. Presence and degree of pigmentation vary with maturity of the host cell. Gametocytes occupy erythrocytes only, with pigment dispersed in black granules throughout the cytoplasm. Cells containing schizonts are often rounded and enlarged and those parasitized by gametocytes may be somewhat distorted in shape by lateral hypertrophy. Host cell nuclei may be displaced, but are not distorted, except slightly by pressure from the parasite. Plasmodium hermani differs from P. (Giovannolaia) durae by producing low level (> 6%), nonlethal parasitemias in turkey poults, an absence of phanerozoites in capillary endothelium of the brain and viscera, and inability to infect chicks. Plasmodium hermani is more like P. (Huffia) elongatum in gametocyte morphology, schizogony in all types of erythrocyte precursors, with gametocytes occurring in erythrocytes only, and concentration of schizonts in heavy infections in bone marrow and spleen. It differs from P. elongatum by its lack of infectivity to passeriform and anseriform hosts and by a strong immune response which develops in infected birds.     

Material transfer from water to sediment in Florida lakes

We describe statistical relationships between chemical aspects of surficial sediments from 34 Florida lakes, and trophic state of the overlying waters. Trophic state is expressed by Carlson's TSI-Chl a. The objectives of the study are two-fold: 1) to understand processes that govern the transfer of material across the mudwater interface, and 2) to develop transfer functions for inferring historical TSI measures in chemically analyzed, ²¹⁰Pb-dated cores. Simple regression of organic matter content or nutrient (C, N, P) concentration in surface sediments vs. TSI yields nonsignificant or weak positive correlations. However, using a novel application of ²¹⁰Pb assay, net accumulation rates of the materials are estimated and show a better correlation with trophic state. Cation (Ca, Mg, Fe, K) and sulfur concentrations in surface muds are poorly related to corresponding TSI's. Net accumulation rates of these elements (Ca, Mg, Fe, K, S) are positively correlated (P < 0.01) with TSI-Chl a. Chemical data from the Florida surficial sediment survey suggest that inferred levels of past trophic state should be based on net accumulation rates of chemical constituents rather than their simple sediment concentrations.     

NEW ENDOLITHIC CYANOPHYTES FROM THE NORTH ATLANTIC OCEAN. II. HYELLA GIGAS LUKAS & GOLUBIC SP. NOV. FROM THE FLORIDA CONTINENTAL MARGIN1

A new species of endolithic cyanophyte, Hyella gigas Lukas and Golubic (Order: Pleurocapsales), differs from other species of Hyella by its larger cell and filament dimensions and its laminated, often pigmented sheath. It bores into mollusk shells and other marine carbonate substrates on the east coast of North America, the Bahama Islands and the Northern Mediterranean Sea, where it is found from near mean low water down to 25 m depth. This comparatively shallow maximum depth is probably due to the limited capacity of Hyella gigas to adapt to changing light quality and intensity. We reject the suppression of the genus Hyella as proposed by Drouet and Daily.     

Albumin synthesis during induced and spontaneous metamorphosis in the bullfrog Rana catesbeiana

Treatment of premetamorphic tadpoles with triiodothyronine (T₃) alters the in vivo distribution of radioactive amino acids among serum protein fractions. The effects on the albumin fraction have been interpreted as reflections of the relative rate of synthesis. About 12 hr after intraperitoneal injection of 2.5 × 10^?10 mole of T₃ per gram, there is an increase in the relative rate of albumin synthesis. The effect peaks on day 3 at 5 × the untreated level and returns to near the untreated level by day 6. Continuous immersion in 1 × 10^?7M T₃ results in a similar stimulation of albumin synthesis, but with no decline after day 3. The timing of the response is independent of dose or route of T₃ administration. The effect of T₃ on the relative rate of albumin synthesis is also observed in froglets. There is a 6-fold increase in the relative rate of albumin synthesis during spontaneous metamorphosis peaking at stage XXI and returning to the premetamorphic level by stage XXV. The following was concluded: (1) The increase in the relative rate of albumin synthesis during metamorphosis results from increased endogenous thyroid levels. (2) Following a peak, the decline in albumin synthesis observed in induced and spontaneously metamorphosing animals is a result of decreasing thyroid hormone levels. (3) The effect of T₃ on albumin synthesis may be the summation of two effects, a direct effect of T₃ and a stimulation by amino acids from the resorbing tail. (4) A decreased relative rate of albumin degradation or a sparing of albumin is probably responsible for the elevated relative concentration of albumin in the serum of postmetamorphic animals.     

Ontogeny of prey selection inSirthenea carinata: Generalist juveniles become specialist adults

Prey selection bySirthenea carinata (F.) [Hemiptera: Reduviidae] was investigated using both field captured and laboratory-reared nymphs and adults. Small nymphs (instars 1–3) showed no preference for mole crickets [Orthoptera: Gryllotalpidae: Scapteriscus] as prey overGryllus spp. orAnurogryllus muticus (De Geer) [Orthoptera: Gryllidae]. Larger nymphs (4th and 5th instars) and adults showed a significant preference for mole crickets in the same sort of choice experiments, choosing mole crickets 84% of the time. Laboratory hatchedSirthenea nymphs matured faster on a mixed diet ofGryllus spp.,A. muticus, andScapteriscus spp. Than did siblings fed a diet ofGryllus spp. alone, but no differences were found in size or duration of individual stadia between the diet groups.