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Premise: Life span varies greatly across plants, with some species being capable of extreme longevity. Yet even long-lived individuals are susceptible to climatic events, fire, and other challenges. We examined rare mortality events and their causes in two long-lived palmettos over four decades., Methods: We monitored the survival of the clonal Serenoa repens and non-clonal, Florida-endemic Sabal etonia from 1981 to 2022 in four habitats along an elevational gradient within the globally imperiled Florida scrub ecosystem. We considered several challenges to palmetto survival, including extreme fires, shading due to lack of fire, droughts, periods of high precipitation, and possible pathogens., Results: Survival of palmettos was remarkably high, and mortality was infrequent (Serenoa: cumulative, 5.7%; annualized, 0%-0.68%; Sabal: cumulative, 3.5%; annualized, 0%-0.43%). Mortality was highest in higher-elevation habitats with greater soil drainage, and smaller palmettos were more likely to die. When subjected to extreme fire, Serenoa suffered greater mortality than Sabal. Mortality in long-unburned habitats with increased shading rivaled that which occurred with extreme fire. There was no evidence of mortality due to lethal bronzing palm disease., Conclusions: Both palmettos had exceptionally low mortality rates, which, coupled with earlier work showing slow rates of transition from seedling to adult and remarkable adult longevity, suggest notably low rates of population turnover. Observed mortality in long-unburned habitats suggests the importance of fire-management planning with prescription burning. Lengthy age to reproduction and/or dependency on clonal propagation limits migration or genetic adaptation to altered conditions caused by climate change., (© 2023 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

Herbivores are among the most pervasive selective forces acting on plants, and the number of plant chemicals that presumably evolved for defense against herbivory is immense. In contrast, biologists are only beginning to appreciate the important roles that architectural traits can play in antiherbivore defense. One putative architectural-resistance trait is the nodding stem apex of some goldenrods (Solidago; Asteraceae). Individuals of S. altissima genets that undergo temporary nodding in the late spring (i.e., "candy-cane" ramets) have been shown to be more resistant than individuals of erect-stemmed genets to certain apex-attacking herbivores. We tested the hypothesis that the greater resistance of candy-cane ramets is accomplished by the ramets' "ducking" from the herbivores. In a greenhouse experiment, nodding candy-cane ramets were significantly more resistant to oviposition by the gall-inducing fly Eurosta solidaginis than were ramets of the same genets that had been experimentally straightened. The straightened candy-cane stems were just as susceptible to ovipositions as were ramets of erect-stemmed genets. Thus, ducking indeed appears to confer a resistance advantage to candy-cane genets of S. altissima.

A main tenet of sex-allocation theory is that environmental stress should lead to increased maleness because reproducing through pollen is generally cheaper than producing fruits and seeds. Though this prediction has held for many species, it has been little tested for gynomonoecious plants, in which individuals produce both female and perfect flowers. We exposed eight ramets of each of 22 genets of a gynomonoecious goldenrod, Solidago altissima (Asteraceae), to a factorial combination of nutrient stress and herbivory by the gall-inducer Eurosta solidaginis (Tephritidae). Nutrient stress alone increased relative femaleness: Stressed ramets produced fewer flowers total and a higher ratio of ray (female) flowers to disk (perfect) flowers. Galling caused no change in fertilized ramets, but the combination of nutrient stress and galling caused an increase in relative maleness: Nutrient-stressed, galled ramets produced fewer flowers total and had a higher disk to ray ratio. In addition to being phenotypically plastic, floral-sex ratio had a great deal of genetic variation, with a broad-sense heritability of 0.68. While the floral-sex ratio responses of gynomonoecious plants may be more complicated than for plants of other breeding systems, they offer the potential to test and refine the already rich body of sex-allocation theory.

Plants of nutrient-poor, arid environments often have leaf traits that include small size, sclerophylly, long life span, low nutrient concentration, and low photosynthetic rate. Hence, the success of two large-leaved palmettos in peninsular Florida's seasonally xeric, nutrient-impoverished uplands seems anomalous, given that their leaves are orders of magnitude larger than the leaves of sympatric species. An examination of a 16-yr data set of leaf traits and leaf life spans across four vegetative associations differing in available light showed that Serenoa repens and Sabal etonia had low rates of leaf production coupled with long leaf life spans reaching 3.5 yr in heavily shaded plants. The adaptation of these palmettos to xeric, nutrient-poor habitats has generated dwarf statures, diminished leaf sizes and numbers, increased leaf life spans, and reduced rates of leaf production relative to other palms and congeners of more mesic sites. Leaf and petiole size, plant leaf canopy area, and leaf life span increased in both palmettos with decreasing available light, helping to compensate for reduced photosynthetic rates under shaded conditions and for the high leaf construction costs of the large, thick palmetto leaves. Large leaf size in these palmettos, likely due to phylogenetic conservatism, is compensated by other leaf traits (e.g., heavily cutinized epidermises, thick laminas) that increase survival in seasonally xeric, nutrient-impoverished environments.

Reproductive output by the Florida-endemic scrub hickory (Carya floridana Sargent) was studied over a 28-yr period in three south-central Florida vegetation associations: southern ridge sandhill, sand pine scrub, and scrubby flatwoods. The objectives were to describe multi-annual patterns of variation in nut production, identify factors involved in this variation, and investigate differences in patterns among associations. Peaks (higher values bracketed by lower values) in nut production occurred in 7 yr in sandhill and scrub and 8 yr in scrubby flatwoods during the 22-yr period for which we had continuous data. Of the total of 22 peaks in the three associations combined, 17 occurred at intervals of 2 or 3 yr, and peaks occurred in the same years in 18 of the 22 cases. Periodicities of nut production generated by spectral analyses (Fourier transforms) generally agreed with the observed peaks. Numbers of nuts per bearing ramet, proportion of ramets bearing nuts, ramet height, and light availability were positively correlated with nut production. Weather variables, specifically winter rainfall and minimum spring temperatures, accounted for a total of about one-quarter to one-half of the variance in nut production depending on the vegetation association. Following a prescribed fire in a sandhill plot, scrub hickory quickly regained fruit production, but over a 5-yr period following the fire nut production by ramets in the largest size class was reduced compared with the unburned control plot.

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.

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.