Dissertation Research: Life History Responses to Fire in a Clonal Herb, Pityopsis graminifolia

目前还不清楚频繁、低强度(如亚致死)火灾等干扰如何影响植物的生活史进化。禾本科蕨类植物是一种火适应的多年生克隆草本植物，栖息在东南长叶松稀树草原频繁燃烧的沙丘上。该物种的繁殖生物学在两个沙丘群落中有所不同，在两个沙丘群落中对其进行了研究，尽管火灾在两个群落中几乎不会导致成虫死亡或幼苗建立。拟议的研究有两个主要目标。它将首先研究低强度火灾如何改变这两个沙丘禾本科植物种群的有利环境条件。具体地说，将研究火是否以及在多大程度上通过增加每个群落中营养物质的可获得性来降低这种耐胁迫物种的开花和营养繁殖(例如克隆生长)的成本。还将审查这些地点火灾后花卉食草性和种子捕食的影响。鉴于该物种在每个沙丘群落发生火灾后表现出的生殖行为表型变化，将评估它们的影响的意义。结果可能表明植物生命过程中波动的环境条件如何影响生活史进化。这项研究的第二个目标是研究开花和克隆生长的动态如何响应不同历史和进化重要性的火灾(例如，生长季火灾与休眠季节火灾)。特别是，将评估在具有历史重要性的生长季节火灾之后更多的开花和更短持续时间的结果是否减少了该物种的花草和/或种子捕食的影响。这类证据可以为长叶松稀树草原生长季节与休眠季节亚致死火灾的适应意义提供洞察力。

It is not well understood how disturbances such as frequent, low- intensity (e.g. sublethal) fire have influenced life history evolution in plants. Pityopsis graminifolia is a fire-adapted, clonal perennial herb that inhabits frequently burned sandhills in Southeastern longleaf pine savannas. The reproductive biology of this species differs in two sandhill communities in which it has been studied despite the fact that fire results in little adult mortality or seedling establishment in either community. The proposed study has two major objectives. It will first examine how low intensity fires change the favorability of environmental conditions in these two sandhill populations of P. graminifolia. Specifically, if and to what extent fire reduces the cost of flowering and vegetative reproduction (e.g. clonal growth) in this stress-tolerant species by increasing the availability of nutrients in each of these communities will be examined. The impact of floral herbivory and seed predation following fire in each of these sites will also be examined. The significance of their impact in light of the phenotypic variation in reproductive behavior exhibited by this species following fires in each of these sandhill communities will be assessed. Results may indicate how fluctuating environmental conditions during the life of a plant influence life history evolution. The second goal of the study is to address how the dynamics of flowering and clonal growth respond to fires that differ in their historical, evolutionary importance (e.g. growing season vs. dormant season fires). In particular, whether the more profuse flowering and fruiting of shorter duration following historically important growing season fires reduces the impact of floral herbivory and/or seed predation in this species will be assessed. Evidence of this kind could provide insight regarding the adaptive significance of growing season vs. dormant season sublethal fires in longleaf pine savannas.