Abstract Detail

Conservation Biology

Yawn, Noah [1], Boyd, Robert [1].

Effects of Herbivory on Demography of a Rare Plant, Trillium pusillum (Melanthiaceae).

The Least Trillium, Trillium pusillum Michaux (Melanthiaceae), is a rare, state-listed, perennial, and charismatic but diminutive member of the Alabama flora. T. pusillum flowers in late spring and the Alabama populations may represent a separate and distinct entity of much greater rarity, Trillium alabamicum, warranting increased conservation concerns. We examined the effects of herbivory on a population of T. pusillum at the Redstone Arsenal in Madison County, Alabama (USA), over a period of 6 years (2016–2021). Ten paired plots containing approximately equal quantities of T. pusillum individuals were randomly assigned treatment as caged or uncaged plots, thereby preventing or allowing herbivory to occur. Plots were visited repeatedly during each growing season to count the numbers of plants in each of three life history stages (e.g., single leaf, 3 leaf, flowering) as well as numbers of fruits produced. We also recorded and counted any plants eaten by herbivores in each visit. Little or no herbivore damage was observed during the first three years of the study (2016–2018). In 2019 and 2020, herbivory became apparent in open plots, with an average of 53% and 24% of total stems, respectively. As a result, sexual reproduction was reduced in open plots; successful fruit production was 19% of total fruits in 2019, with a decrease to 0% in 2020. By 2020, a marked shift in demographic composition and fruit production in comparison to caged plots is quantified by a significant decrease in total flowering plants (i.e., 45 in caged plots compared to 20 in open plots). In 2021, this demographic shift is further exemplified: of 37 flowering stems, only 1 was within a caged plot. However, over all survey years, changes in total number of stems in lower life history stages was not apparent (e.g., caged: 134 single-leaf, 128 three-leaf; open: 198 single-leaf, 112 three-leaf for the 2021 survey year). Thus, herbivory affects T. pusillum in its ability to sexually reproduce, altering overall population demographic composition in plots subject to herbivory over time. We attribute this to the overall energy requirement needed to flower, where repeated herbivory may revert flowering individuals to previous life history stages, hindering their ability to successfully produce seed. These findings suggest improved management practices for imperiled Trillium conservation.

1 - Auburn University, Department Of Biological Sciences, 101 Rouse Life Sciences Bldg, Auburn University, AL, 36849, United States

Keywords:
Trillium
Melanthiaceae
Demographic shift
herbivory
Plant conservation.

Presentation Type: Oral Paper
Session: CB03, Conservation Biology 3
Location: /
Date: Wednesday, July 21st, 2021
Time: 4:30 PM(EDT)
Number: CB03007
Abstract ID:1086
Candidate for Awards:None