What kills the virtually immortal palms of the Florida scrub?

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. Meth...

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Bibliographic Details
Published in:American journal of botany 2023-10, Vol.110 (10), p.1-e16234
Main Authors: Abrahamson, Warren G., Abrahamson, Christy R., Koontz, Stephanie M., Tran, Elan H., Menges, Eric S., David, Aaron S.
Format: Article
Language:English
Subjects:
Climate change
Drought
Habitats
Life span
Longevity
Management planning
Mortality
Propagation
Scrub
Seedlings
Serenoa
Shading
Survival
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Summary: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.
ISSN:0002-9122
1537-2197
DOI:10.1002/ajb2.16234