Carl W. Weekley

Assembly, Gene Annotation and Marker Development Using 454 Floral Transcriptome Sequences in Ziziphus Celata (Rhamnaceae), a Highly Endangered, Florida Endemic Plant

Large-scale DNA sequence data may enable development of genetic resources in endangered species, thereby facilitating conservation efforts. Ziziphus celata, a federally endangered, self-incompatible plant species occurring in Florida, USA, is one species for which genetic resources are necessary to facilitate new introductions and augmentations essential for recovery of the species. We used 454 pyrosequencing of a Z. celata normalized floral cDNA library to create a genomic resource for gene and marker discovery. A half-plate GS-FLX Titanium run yielded 655 337 reads averaging 250 bp. A total of 474 025 reads were assembled de novo into 84 645 contigs averaging 408 bp, while 181 312 reads remained unassembled. Forty-seven and 43% of contig consensus sequences had BLAST matches to known proteins in the Uniref50 and TAIR9 annotated protein databases, respectively; many contigs fully represented orthologous proteins in TAIR9. A total of 22 707 unique genes were sequenced, indicating substantial coverage of the Z. celata transcriptome. We detected single-nucleotide polymorphisms and simple sequence repeats (SSRs) and developed thousands of SSR primers for use in future genetic studies. As a first step towards understanding self-incompatibility in Z. celata, we identified sequences belonging to the gene family encoding self-incompatibility. This study demonstrates the efficacy of 454 transcriptome sequencing for rapid gene and marker discovery in an endangered plant.

Species and Vegetation Responses to Prescribed Fire in a Long-Unburned, Endemic-Rich Lake Wales Ridge Scrub

WEEKLEY, C. W. AND E. S. MENGES (Archbold Biological Station, P.O. Box 2057, Lake Placid, FL 33862). Species and vegetation responses to prescribed fire in a long-unburned, endemic-rich Lake Wales Ridge scrub. J. Torrey Bot. Soc. 130: 265-285. 2003.-We studied the effects of prescribed fire on a long-unburned oak scrub on the Lake Wales Ridge of central Florida. We quantified postburn survival of 12 endemic plants by censusing tagged individuals before and after fire, assessed postfire changes in the composition and structure of the scrub community, and investigated the effect of postfire cover changes in subcanopy, shrub, litter, lichen and Polygonella myriophylla on herb abundance. We found that eight of the 12 endemics had postburn resprouting rates varying from -15% to 98%, while four species were killed by fire. Postburn reductions in subcanopy, shrub, litter, lichen and P. myriophylla cover were paralleled by increases in the abundance of scrub herbs. While some scrub herbs resprouted, most postburn increases in herb abundance were due to seedling recruitment.

The breeding system of Ziziphus celata Judd and D.W. Hall (Rhamnaceae), a rare endemic plant of the Lake Wales Ridge, Florida, USA: implications for recovery

Although the rarity of an endangered plant species can seldom be ascribed to its breeding system, knowledge of its breeding system may be critical to its recovery. The federally listed endangered Ziziphus celata (Florida ziziphus), a woody clonal shrub narrowly endemic to xeric upland habitats of the Lake Wales Ridge in central Florida, USA, is known from only five populations, four of which are sterile and perhaps uniclonal. Altogether only 11 genotypes of Florida ziziphus have been identified by allozyme electrophoresis. We studied the breeding system of Florida ziziphus and found that it is an obligate outcrosser and that some genotypes are cross-incompatible. We have been able to demonstrate the cross-compatibility of only 11 of the 44 test crosses performed to date (25%), as measured by fruit yield. Cross-incompatibility is most likely due to shared self-incompatibility (S) alleles among the few remaining genotypes of these fragmented populations. The identification and translocation of compatible mating types to create reproductively viable populations is essential for the recovery of Florida ziziphus.

Comparison of three devices for estimating fire temperatures in ecological studies

Abstract Questions: Are calorimeters and pyrometers accurate and reliable for describing fire parameters in large-scale ecological projects, and can data from them predict data derived from thermocouples? Do mechanical pre-treatments in Florida scrub areas alter fire properties? Location: Lake Wales Ridge, Florida, USA. Methods: We deployed thermocouples attached to digital dataloggers, copper and lacquer paint pyrometers and aluminium can calorimeters filled with water in four areas of undisturbed Florida scrub and sandhill vegetation and in adjoining areas pre-treated with logging, subcanopy felling or mowing. Individual dataloggers were positioned in areas spanning a range of vegetation structure; three calorimeters and three pyrometers were placed with each thermocouple. We also deployed individual calorimeter-pyrometer pairs. Sites were burned, after which we compared methods for characterizing fire, particularly the ability of pyrometers and calorimeters to predict values derived from thermocouples. Results: Pyrometers best predicted peak 1-minute mean temperatures and were least successful at estimating maximums. Calorimeters were associated with the number of minutes maximum temperatures exceeded 60 °C, but were damaged at high residence times and inconsistent at low temperatures. Both pyrometers and calorimeters detected site and treatment differences in fire intensities. These analyses and logistic considerations give pyrometers an edge over calorimeters in situations where dataloggers are impractical. Mechanical pre-treatments to fire altered fire parameters. Mowing reduced fire temperatures but had different effects on areas burned; this was related to the length of time elapsed between mowing and burning. Subcanopy felling increased both fire coverage and temperatures. Conclusion: Pyrometers outperformed calorimeters as a cheap method for describing relative temperature regimes that are a function of both temperature and residence time. Pyrometers were able to demonstrate how mechanical treatments applied prior to prescribed burning altered fire parameters. Pyrometers are a useful tool for investigating biological responses to fire at multiple scales and in heterogeneous vegetation. Abbreviations: AREA60 = the integrated area under the instantaneous temperature curve defined by a threshold of 60 °C; AREA150 = the integrated area under the instantaneous temperature curve defined by a threshold of 150 °C; CALOR = mean percent water loss from calorimeters adjusted for evaporation; MAX = peak instantaneous temperature (°C); MAX60 = number of minutes where the instantaneous temperature > 60 °C; MAX150 = number of minutes where the one minute mean temperature > 150 °C; MEAN = peak one minute mean temperature (°C); MEAN60 = number of minutes where the one minute mean temperature > 60 °C; MEAN150 = number of minutes where the one minute mean temperature > 150 °C; PYRO = median pyrometer reading. Nomenclature: Wunderlin & Hansen (2003).

Variation in soil moisture in relation to rainfall, vegetation, gaps, and time-since-fire in Florida scrub

ABSTRACT Florida scrub is a pyrogenic shrubland ecosystem occurring on well-drained sands derived from contemporary and relictual beach dunes. Despite average annual precipitation > 1300 mm, Florida scrub is dominated by xeromorphic plants. We monitored spatio-temporal variation in soil moisture to determine if the distribution of Florida scrub communities reflects patterns in soil moisture variation. Using frequency domain reflectometry, we measured soil moisture at 24 sampling stations (3 depths per station) in 3 Florida scrub communities (rosemary scrub, scrubby flatwoods, and oak–hickory scrub) at Archbold Biological Station for 3y (October 1998–September 2001). Stations were arrayed to sample 2 microhabitats (gaps, shrubs) and 2 burn histories. Soil moisture closely tracked cumulative rainfall across widely varying precipitation in the 3 y studied. Soil moisture changed through time and differed significantly among habitats; it was generally highest in scrubby flatwoods, particularly during the wettest periods, and lowest in oak–hickory scrub. Soil moisture was generally greater at deeper depths, in more recently burned sites, and in gaps. Burn effects were particularly pronounced in rosemary scrub, where lack of resprouting dominants after fire maintains more distinct, larger gaps. Burn and gap effects were small in absolute terms, but burned sites and gaps consistently had greater soil moisture than unburned and matrix sites. These small differences may be critical to the germination, establishment, and growth of narrowly endemic plants, particularly in Florida rosemary scrub. However, factors such as competition for nutrients, cryptobiotic soil crusts, litter accumulation, gap size, and allelopathy may be more important in influencing distributions of endemic scrub plants.

Herbivory Delays Flowering and Reduces Fecundity of Liatris ohlingerae (Asteraceae), an Endangered, Endemic Plant of the Florida Scrub

Abstract Herbivores may negatively impact plants by reducing biomass and decreasing fecundity. Rare or endangered plants may be particularly vulnerable to herbivore damage. However, plants may compensate for herbivory by increased growth or reproductive output. We investigated compensatory growth and reproductive effort in Liatris ohlingerae (S.F.Blake) B.L.Robe, a federally-listed herb narrowly endemic to pyrogenic Florida scrub on the Lake Wales Ridge, by conducting biweekly surveys of observed herbivory and an herbivore exclusion experiment. In the field surveys, we assessed the effects of vertebrate herbivory (“topping”) and invertebrate leaf herbivory on plant size and fecundity and compared observed levels of herbivory across sites with different disturbance histories (scrub vs. roadside; scrub sites with differing time-since-fire). In the herbivore exclusion experiment, we compared the effects on plant size and fecundity of excluding vertebrate herbivores (toppers) only vs. excluding both vertebrate and invertebrate herbivores. We found that 62% of plants in the survey had one or more topped stems and that topping occurred more frequently in recently burned sites (< 8 years since fire vs. > 14 years since fire) and in scrub than in roadside sites. Topped plants were significantly shorter and had a greater number of stems (untopped plants only produced 1 stem). Topped plants were less likely to flower, began flowering later in the growing season, and produced fewer inflorescences, infructescences, achenes, and full achenes than untopped plants. Fifty-two percent of surveyed L. ohlingerae plants also showed evidence of invertebrate leaf herbivory with a mean of 24% of leaves damaged. Plants damaged by invertebrate herbivores did not differ significantly in growth or reproduction compared with undamaged plants. In the experiment, exclusion of vertebrate herbivores resulted in taller plants, fewer stems, higher flowering frequency, earlier first flowering, and greater production of inflorescences, infructescences, achenes, and full achenes per plant; plants gained no additional benefits when invertebrates were excluded. Our study demonstrates that L. ohlingerae partially compensates for vertebrate herbivore damage at some sites, depending on the disturbance history. There are population level consequences of undercompensation; vertebrate topping resulted in a 30% reduction in mean fecundity. Future research is necessary to determine if undercompensation jeopardizes the long-term persistence of L. ohlingerae populations.

Failure of reproductive assurance in the chasmogamous flowers of Polygala lewtonii (Polygalaceae), an endangered sandhill herb

Hypothetically, a species with both cleistogamous (CL) flowers and delayed selfing chasmogamous (CH) flowers should display high levels of reproductive assurance because, over time, obligate selfing by CL flowers should reduce inbreeding depression and delayed selfing in CH flowers should compensate for the absence of outcross pollen. We used pollinator-exclusion experiments to investigate reproductive assurance in the CH flowers of Polygala lewtonii, an herb with a mixed mating system. We followed CH flowers from bud-break to flower/fruit abscission to quantify fruit initiation and maturation and rates of floral development. We also evaluated the efficacy of the selfing mechanism, conducted pollinator watches to assess the likelihood of pollinator limitation, and performed regression analysis to determine the effect of flower position on fruit production. Pollinator exclusion significantly reduced fruit initiation and maturation. Investigation of floral development demonstrated that the selfing mechanism is largely dysfunctional in CH flowers, indicating the failure of reproductive assurance. Low observed rates of insect visitation appear to contradict high rates of CH fruit production in open-pollinated plants, particularly given the rarity of delayed selfing. In both treatments, flower position significantly affected fruit initiation, suggesting a role for resource limitation in both pollinator-excluded and open-pollinated flowers.

Seedling emergence and survival of Warea carteri (Brassicaceae), an endangered annual herb of the Florida Scrub

Seedling emergence and survival to flowering are critical processes in the life history of annual plants. We eval- uated the importance of year and habitat on seedling emergence and the effects of year, habitat, timing of seedling emer- gence, and seedling density on survival of Warea carteri Small, an annual mustard endemic to Florida scrub. We tagged 1329 seedlings in 78 permanent 0.25 m 2 quadrats in two habitats (scrub and disturbed) between 1999 and 2002 and fol- lowed seedlings monthly. Most (>80%) seedling emergence occurred between September and December. Emergence peaked 2 months earlier and was more variable in disturbed sites than in scrub. Seedling survival among years ranged from 3.5% to 12.0%. Seedling density varied from 1 to 75 per 0.25 m 2 quadrat, with an overall median of 6.0. Survival was not density dependent. Median age at flowering ranged from 11.7 to 15.2 months, with late season recruits most likely to sur- vive to flowering. Warea carteri recruits like a winter annual but flowers like a summer annual. Its delayed germination and a 12-15 month life span contribute to population cycling. Complete reproductive failure in unfavorable years, high seed pro- duction in favorable years, low rates of seed germination, and a persistent seed bank are consistent with predictions for an an- nual species in a variable habitat.

Burning creates contrasting demographic patterns in Polygala lewtonii (Polygalaceae): a cradle-to-grave analysis of multiple cohorts in a perennial herb

Fire drives the population dynamics of many plants. By following successive cohorts of Polygala lewtonii Small (Polygalaceae), a short-lived herb endemic to fire-maintained Florida sandhills, in both burned and unburned microsites, we investigated how fire affected vital rates throughout cohort lifetimes. We followed cohorts from before to 6 years after a prescribed fire in 220 25-cm-radius quadrats, recording survival and seedling recruitment quarterly, and growth and fecundity annually. Fire effects were most pronounced in the first 2 post-burn quarterly censuses, when cohorts in burned (v. unburned) quadrats had seven-fold higher seedling recruitment, significantly higher seedling survival, and a 16.7% gain (v. 1.2% loss) in quadrat occupancy. Plants in burned (v. unburned) quadrats also flowered earlier, were more likely to survive to reproduce and had longer lifespans. The negative effects of density on survival were relaxed in burned quadrats for the first 2 censuses. Burning creates contrasting demographic trajectories for burned v. unburned cohorts. In burned microsites, higher seedling recruitment and survival, earlier flowering and longer lifespans combine to produce a greater contribution to the seedbank and, thus, to population viability. The present study documents the pyro-demographic mechanisms linking the life history of a perennial herb with a frequent fire regime.

Effects of Time-Since-Fire and Microhabitat on the Occurrence and Density of the Endemic Paronychia chartacea ssp. chartacea in Florida Scrub and Along Roadsides

Abstract Conservation of an imperiled plant species requires an understanding of its local occurrence and density in relation to habitat variation. Paronychia chartacea ssp. chartacea is a federally threatened species restricted to gaps in fire-maintained Florida rosemary scrub and to roadside sites that mimic scrub gaps. To assess the effects of time-since-fire and microhabitat on the occurrence and density of Paronychia populations, we conducted surveys of 119 scrub gaps and 16 roadside macroplots. In rosemary scrub, we found that the frequency of gap occupancy decreased with time-since-fire and that Paronychia occurrence and density were greater in the centers of large gaps than in small gaps or large gap edges. In roadside sites, the distance from adjacent rosemary scrub did not affect the presence of Paronychia, but density increased with distance from rosemary scrub vegetation. Paronychia densities in roadside sites were most similar to densities in recently burned rosemary scrub. Time-since-fire and microhabitat quality affect the occurrence and density of Paronychia and should be considered in management of Paronychia populations.