The phylogenetic history and ecophysiological diversity of Kalmia buxifolia (sand-myrtle)

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Ellen Jean Quinlan (Creator)
Institution
Western Carolina University (WCU )
Web Site: http://library.wcu.edu/
Advisor
Katherine Mathews and Beverly Collins

Abstract: Kalmia buxifolia (sand-myrtle, Ericaceae) exhibits a highly disjunct distribution across the high-elevation rock outcrops of the southern Appalachians, upper monadnocks of the North Carolina Piedmont, pine savannas of the Carolina Coastal Plain, and New Jersey Pine Barrens. Although widely separated, these regions share commonalities in their microclimates, particularly nutrient-poor, acidic soils with low soil water retention. Still, K. buxifolia coastal populations may use water differently from their mountain counterparts that receive much of their water through daily cloud immersion (fog). Previous studies have found significant, among-region variation in morphology, but no clear pattern of genetic divergence using allozymes in K. buxifolia. We hypothesized that there was geographically-based variation in cpDNA haplotypes and drought tolerance between mountain and coastal populations. Additionally, the common hypothesis for rock outcrop floristic divergence predicts that these relationships are relatively young, relics of Pleistocene refugia (<18,000 ybp). The goals of this study were to: 1) Reconstruct the phylogeographic history of K. buxifolia and date the divergence from its alpine sister species K. procumbens; and 2) assess the variation in water-use efficiency (WUE) between the mountain and coastal populations of K. buxifolia over a season. Dating analysis refutes the rock-outcrop hypothesis as it applies to this species, placing the divergence of K. buxifolia and K. procumbens mid-Miocene (~14.9 Ma). Haplotype analysis then indicated four potential refugial sites with the most ancient found on Mount LeConte (GSMNP) and three more recent refugia around the Highlands Plateau, Sufolk escarpment, and New Jersey Pine Barrens, as well as points to an Appalachian corridor as the likely Pine Barrens colonization route. Both species and population level divergences within K. buxifolia seem to coincide with the major climatic shifts from the mid-Miocene to early-Pliocene. WUE results indicate that plant water-use varies geographically within K. buxifolia and that the variation is likely driven by stomatal function rather than morphology. Understanding these phylogenetic and ecophysiological relationships within this species and other similar species is essential when confronted with a once-again changing climate and may be important for developing future management plans.

Additional Information

Publication
Thesis
Language: English
Date: 2018
Keywords
ecophysiology, Kalmia buxifolia, phylogeography, rock outcrop, water-use efficiency

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