James N. Layne

ACORN HARVESTING BY FLORIDA SCRUB JAYS

We documented numbers of acorns eaten, cached, and retrieved by Florida Scrub Jays (Aphelocoma coerulescens coerulescens), through one full annual cycle and part of another, in an oak scrub habitat characterized by abundant and reliable annual acorn crops. Jays consumed acorns during all months, with highest consumption from September through February and lowest in June and July. From August through December, most acorns consumed by jays were picked directly from shrubs; during the remaining 7 mo, acorns were recovered from ground stores. Acorn caching occurred throughout the fall, peaking in September and October. Data pooled across sex and age classes suggest that individual jays, on average, each cached between 6500 and 8000 acorns during fall of 1974. Only about one-third of those acorns were recovered later. Intact acorns recovered by Scrub Jays during fall usually were reburied, but by summer most recovered acorns were con- sumed. Acorn crops in the study area exhibit moderate annual variation but no crop failures. Acorns are available in substantial numbers every year, permitting Florida Scrub Jay territories to serve without fail as year-round warehouses of stored acorns. Those stores provide resources to carry group members through seasons of low arthropod availability, and perhaps facilitate delayed dispersal by juveniles. Use of a habitat characterized by relatively large and dependable annual acorn crops that are evenly dispersed, coupled with caching behavior, may contribute to the maintenance of permanent territoriality and co- operative breeding in this population.

Twenty years of vegetation change in five long-unburned Florida plant communities

Rates and directions of change over a 20-yr interval in five long-unburned (> 60 yr) plant communities were stud- ied using multivariate analyses and compositional vectors. The study sites were located in fire and summer-drought adapted, xerophytic vegetation with many endemics on acidic, nutrient-poor, sandy soils in south-central peninsular Florida. Sizes of individual stems from 72 sets of nested permanent quadrats were measured in 1969, 1979, and 1989. Patterns of vegetation change differed by community. Flatwood and bayhead quadrats showed rapid increases in densities and basal areas of Persea borbonia (red bay). In the southern ridge sandhill community, evergreen clonal Quercus species (oaks) and Pinus clausa (sand pine) increased in dominance and grasses declined. Oaks (especially Q. geminata) also increased in importance in scrubby flatwoods. Sand pine scrub was relatively stable in composition, but experienced marked structural changes due to substantial sand pine mortal- ity (18 % during 1969-1979, 39 % during 1979-1989). Com- positional changes in the absence of fire were greatest whereas structural changes were least in southern ridge sandhill and scrubby flatwoods, both communities which normally receive frequent, recurrent fire. Compositional changes were lowest in sand pine scrub, which is normally infrequently burned. Classic successional patterns such as species replacement, decreases in density, and increases in basal area were gener- ally lacking. Tree densities increased in two of four communi- ty types (southern ridge sandhill, scrubby flatwoods); while basal area declined in the flatwoods/bayhead and sand pine scrub sites. Directions of compositional vectors included di- vergent, opposing, and complex patterns, suggesting vegeta- tion change in the absence of fire has a strong stochastic component.

LONG‐TERM PATTERNS OF ACORN PRODUCTION FOR FIVE OAK SPECIES IN XERIC FLORIDA UPLANDS

The number of seeds produced by a population of woody plants can vary markedly from year to year. Unfortunately, knowledge of the patterns and causes of crop-size variation is limited, and most studies have examined only single species in a single mesic environment. We examined long-term patterns of acorn crop sizes for five species of shrubby oaks in three xeric upland vegetative associations of south-central peninsular Florida for evidence of regular fruiting cycles and in relation to winter temperature and precipitation. Counts of acorns on two white oak species (Quercus chapmanii and Q. geminata) and three red oak species (Q. inopina, Q. laevis, and Q. myrtifolia) were conducted annually from 1969 to 1996 (except in 1991) on grids in southern ridge sandhill, sand pine scrub, and scrubby flatwoods associations. As the result of the dissimilar timing of reproductive events in species of red and white oaks and individual species responses to climatic variables, annual acorn production of red and white oak species in a given vegetation association were not synchronized, which dampened the variability of combined annual acorn production. Consequently, acorns were produced with reasonable abundance every year by at least one species. Oaks of nearly closed-canopy scrub produced fewer acorns than similar-sized oaks of the same species in the more open-canopied sandhill and scrubby flatwoods, suggesting light limitation. We identified regular cycles of acorn production that ranged from 2 to 2.4 yr for white oak species and from 3.6 to 5.5 yr for red oak species and found evidence that annual acorn production is affected by the interactions of precipitation, which is highly variable seasonally and annually in peninsular Florida, with endogenous reproductive patterns. Multiple regression models using precipitation variables accounted for as much as 74% of crop-size variation in Q. inopina, 65% in Q. laevis, 60% in Q. chapmanii, and 44% in Q. geminata, but only 29% for Q. myrtifolia. In contrast, acorn production showed no significant association with minimum winter temperatures. Of the various hypotheses offered to explain supra-annual variation in seed crops, our data are most compatible with the nonadaptive resource-matching hypothesis.

Communal Nesting of Southern Flying Squirrels in Florida

Use of nest boxes by southern flying squirrels ( Glaucomys volans ), with emphasis on communal nesting, was studied for 5 years in southcentral Florida. Of 841 occupied boxes, 11% contained litters, 81% contained aggregations of 2–25 individuals, and 9% contained solitary individuals. Of 676 aggregations, 79% contained only adults, and 21% were comprised of adults and subadults and, rarely, nestlings. At least 16% of the aggregations contained related individuals. Aggregations of adults were significantly smaller ( X = 7.2) than those of mixed-age groups ( X = 9.0). Most aggregations contained both sexes. Sex ratios of original captures of both adults and subadults in communal groups were significantly biased toward males. Communal nesting peaked in January, persisted into spring, and was lowest in September. The proportion of males in aggregations of adults significantly decreased over winter. The population in Florida had a more prolonged period of communal nesting and larger mean size of both cold- and warm-weather aggregations than reported for more northerly populations. The high level of communal nesting in the southern part of the range suggests that, besides a thermoregulatory function, aggregative behavior also may play a significant role in the social organization of populations of flying squirrels.

Structural changes and successional relationships of five Florida Lake Wales Ridge plant communities

GIVENS, K. T., J. N. LAYNE, W. G. ABRAHAMSON AND S. C. WHITE-SCHULER (Department of Biology, Bucknell University, Lewisburg, PA 17837 and Archbold Biological Station, Route 2, Box 180, Lake Placid, FL 33852). Structural changes and successional relationships of five Florida Lake Wales Ridge plant communities. Bull. Torrey Bot. Club 111: 8-18. 1984.-Vegetation of five southern Lake Wales Ridge associations was sampled at Archbold Biological Station, Lake Placid, Florida, in permanent nested quadrats in each of the associations in 1969 and 1979. These associations have been free of fire for over 50 years. Quadrats were sampled for species composition, density, and growth parameters of herbs, shrubs, and trees, and also for percent litter coverage and depth. Several trends were apparent in all the associations examined: (1) substantial thinning of herb and shrub layers with disappearance of several shade-intolerant species; (2) an increase in tree canopy coverage despite extensive shrub thinning, as few trees died in the 10-year study period; (3) an increase in shrub and tree species richness and diversity; (4) increase in litter coverage and depth; and (5) a slow rate of succession, not appreciably different among the five communities. Pairwise comparisons of the 1969 and 1979 Horns Indices from different communities did not reveal support for the successional relationships proposed in the literature.

Nests and Daytime Refugia of Cotton Mice (Peromyscus gossypinus) and Golden Mice (Ochrotomys nuttalli) in South-central Florida

-Daytime refuge selection, nest construction, and patterns of refuge use of cotton mice (Peromyscus gossypinus) and golden mice (Ochrotomys nuttalli) were studied in S-central Florida. Of 95 P. gossypinus refugia examined, 67 were burrows of the gopher tortoise (Gopherus polyphemus), 23 were ground holes, and five were hollow tree cavities. Of 77 0. nuttalli refugia examined, 75 were on the ground under leaf litter and two were aboveground in shrubs. Neither species differed in seasonal refuge selection. Peromyscus gossypinus built platform and spherical nests of saw palmetto (Serenoa repens) fibers, lichens and cotton, and 0. nuttalli built spherical nests of saw palmetto fibers, Spanish moss, leaves, twigs, grasses and cotton. Winter 0. nuttalli nests were significantly larger and heavier than summer nests. Individuals of both species used a similar number of refugia, and refuge fidelity was greater for both species during winter. The greater versatility of refuge selection in P. gossypinus may contribute to its ability to exploit a wider variety of habitats than 0. nuttalli. Based on the extreme differences in refuge selection observed between these species, it is unlikely that competition for daytime refugia occurred in this study.

Variation in tannin activity of acorns of seven species of central Florida oaks

Acorns of seven sympatric species of oaks (Quercus spp.) occurring in central Florida were compared for protein-precipitating ability (PPA). Husks and cotyledons of green and ripe acoms were analyzed. Few significant differences were found between green and ripe acorns of the same species. Cotyledons were significantly higher than husks in PPA in most of the species compared. All species exhibited high intraspecific variability in PPA. Significant differences between species were found in green and ripe cotyledons and in green husks. With the exception ofQ. minima, PPA of ripe cotyledons was higher in the subgenusErythrobalanus (red oaks) than the subgenusQuercus (white oaks).

Post-fire recovery of acorn production by four oak species in southern ridge sandhill association in south-central Florida

We examined post-fire recovery of two components of acorn production (percentage of bearing ramets [stems] and number of acorns per bearing ramet) for four species of oaks in southern ridge sandhill vegetation in south-central peninsular Florida. Annual counts of acorns on two white oaks (Quercus chapmanii and Q. geminata) and two red oaks (Q. laevis and Q. myrtifolia) were conducted annually (except in 1991) on two 2.7-ha grids from 1969 to 1998. A prescribed burn was conducted on one of the grids in May 1993. Newly sprouted ramets of both white oaks produced acorns during the first year following the fire, whereas red oaks required 3 yr (Q. myrtifolia) or 4 yr (Q. laevis) to produce acorns. The difference in the timing of post-fire acorn production between the white and red oak species reflected the difference in the number of years from flower bud initiation to mature acorns in the two groups, with the additional year-long lag in Q. laevis probably attributable to the fact that it is typically a tree rather than a shrub species. The data suggested that percentage of bearing ramets in the smallest size class of the two white oak species was markedly lower in the burned than unburned grid in the first year of post-fire acorn production and higher in the fifth year, but these trends were not evident for the red oaks. Among all four species, differences between mean number of acorns in burned and unburned grids were significant in only two cases (the largest size class of both white oak species in the fifth year). There was no evidence of recruitment from acorns on the burned grid, possibly due to the rapid redevelopment of the shrub layer because of low mortality of the extensive clonal root systems. Rapid post-fire recovery of acorn production in xeric fire-prone habitats is presumably the result of selection to increase the probability of recovery and persistence following sufficiently intense fires that result in high oak mortality. The timing and magnitude of post-fire acorn production in sandhill and other xeric Florida associations has a potential impact on a wide variety of insects, birds, and mammals that feed on acorns, as well as on the species with which they interact.

Relation of ramet size to acorn production in five oak species of xeric upland habitats in south-central Florida

This study examined variation in two components of acorn production. Percentage of bearing ramets (stems) and number of acorns per bearing ramet were examined in five clonal oaks in three xeric habitats of south-central peninsular Florida in relation to ramet size within and between species and vegetative associations. Counts of acorns on two white oaks (Quercus chapmanii and Q. geminata) and three red oaks (Q. inopina, Q. laevis, and Q. myrtifolia) were conducted annually from 1969 to 1996 (except in 1991) on permanent grids in southern ridge sandhill, sand pine scrub, and scrubby flatwoods associations at the Archbold Biological Station, Florida, USA. Percentage of bearing individuals and mean number of acorns per bearing individual increased with increasing ramet size for all species across all vegetation associations. However, in Q. geminata and Q. myrtifolia, acorn production declined in the largest size class (>3.2 m), implying that larger individuals of these clonal species may become senescent. All oak species in sand pine scrub, which had a nearly closed overstory, had lower frequencies of bearing oaks and mean numbers of acorns compared with similar-sized individuals of the same species in the more open-canopied southern ridge sandhill and scrubby flatwoods associations, suggesting light limitation. The annual production of acorns by a given oak species was correlated across vegetative associations and annual acorn production of oak species was correlated for species within the same section. Intermediate-size class oaks contributed the most acorns per unit area, suggesting that stands managed with short fire-return times will provide fewer acorns to wildlife than stands managed to produce more variable distributions of oak size classes. However, our study suggests that long-unburned stands, such as those studied here, will maintain relatively constant levels of acorn production as a consequence of ramet replacement within the clones of these shrubby oaks to create a variable distribution of size classes. Of the oak species studied, Q. myrtifolia had the highest acorn production and the smallest acorns, while Q. laevis had the lowest acorn production and the largest acorns, suggesting an allocation trade-off between acorn numbers and size.

Foraging Site Preferences and Relative Arboreality of Small Rodents in Florida

-Foraging microhabitat preferences of Ochrotomys nuttalli, Peromyscus gossypinus, P. polionotus, Podomys floridanus and Sigmodon hispidus in two major vegetation associations in S-central Florida were studied by placing bait containing different-colored plastic marker on the ground in structurally open and closed sites and in trees and recovering the markers from feces of live-trapped individuals. The average proportion of fecal samples containing marker ranged from 47-74% among the five species. Based on frequencies of different colors of marker in feces, there were no significant differences among species in extent of foraging in open and closed ground sites, and all foraged significantly more on the ground than in trees. Interspecific differences in the amount of arboreal activity were generally consistent with predictions based on the morphology, behavior and ecology of the species, although Ochrotomys foraged more frequently on the ground and the other four species more frequently in trees than expected. The rankings of species in two other measures of arboreal tendency were generally similar to that with marked baits, although Ochrotomys was more arboreal and the other species less so, than in the marked-bait study.