Meeting Abstract

67.7  Wednesday, Jan. 6  Rarity as a life-history correlate in Dudleya (Plantae: Crassulaceae) DORSEY, A. E.*; WILSON, P. S.; California State University, Northridge; California State University, Northridge ann.dorsey.88@csun.edu

In this study the life-history tradeoffs and habitats of rare and common species are compared to find how these aspects might affect their geographic prevalences. Nine Dudleya species occurring in and around the Santa Monica Mountains were studied. Five are rare narrow endemics with small localized ranges, one is rare with an intermediate range, and three are common with broader ranges. Life-history traits were studied in wild populations and in cultivated siblings from wild collected seeds. In regard to life-history tradeoffs there were differences in growth and reproduction. The rare species grew to a smaller size and reproduced earlier than common species. The small body size of the rare species resulted in smaller reproductive outputs than the larger-bodied common species. The rare species also tended to have lower seedling survival. Reproductive output and survival affect population size, persistence, and dispersal all of which directly affect species’ distributions. Habitat characteristics were recorded in two or three populations of each study species. The habitat requirements of the study species differed in co-occurring vegetation, soil type, and microclimate. The rare species grow in habitats that do not occur as often as those of the common species contributing to their scarcity. To further understand how habitat may play a role in limiting species’ distributions, the nine species were grown in an inland and a coastal garden. Plants of all species grown in the inland garden were smaller in size than those in the coastal garden. Moreover, the growth disparity between plants in the two gardens was greatest for the rare species. The rare species have a lower tolerance for hot dry conditions compared to the common species. Differences in life-histories resulting from tradeoffs affect the rarity of the species, as well as specialization on rare habitats.