Drivers of reproductive variability in Vaccinium cespitosum and vaccinium vitis-idaea in northeastern Minnesota

Abstract

Multiple factors affect reproductive variability within a population, and understanding these factors is important for making informed land management decisions. I investigated how clonality impacts reproductive variability in Vaccinium cespitosum and Vaccinium vitis-idaea (Ericaceae), and how the history of land management affects reproductive variability in V. cespitosum. Vaccinium populations with a history of land management are expected to have higher reproductive potential than populations that have not been managed, as land management has been shown to positively impact stem, flower, and fruit production. Additionally, both species are partially clonal and are capable of sexual or clonal reproduction. In populations with high clone densities, the likelihood of self-pollination via geitonogamy and subsequent early-acting inbreeding depression increases. Potential impacts due to early acting inbreeding depression include reduced fruit production and reduced fecundity of populations, which reduces the efficacy of land management. I established multiple survey sites (populations) in northeastern and northcentral Minnesota and collected measures of sexual reproductive effort (proportion of flowering ramets and number of flowers per ramet) and sexual reproductive success (percent fruit set, proportion of viable to inviable seeds, and berry mass and diameter) for both species. For V. cespitosum, populations were selected based on contrasting disturbed vs established land management histories. Between study years, land management history and clonality were not significant predictors of reproductive effort or subsequent success. There is a complex interplay of many factors, both large scale, such as yearly climatic conditions and geographic range, and small scale, such as soil nutrient quality, that likely interact to influence reproductive variability among our populations.