Demographic population structure of a leafy epixylic hepatic Anastrophyllum hellerianum (Nees ex Lindenb.) R.M.Schust

Abstract

Understanding the population processes is central when assessing proper conservation acts, especially in the case of species which inhabit temporal and patchy substrates, such as decaying wood. In epixylic bryophytes, however, only little is known of the demographic population structure and within-population dynamics. In this study on a leafy epixylic hepatic, Anastrophyllum hellerianum (Nees ex Lindenb.) R.M.Schust., a set of demographic traits is investigated, including colony area and size, proportions of the sterile, gemmiparous or sexual developmental stages, the shoot size class distribution among the developmental stages, and numbers of asexual propagules present on the shoots. The estimates of mortality are assessed on the basis of the proportions of dead shoots found in the colonies. The size distribution within the developmental stages of this species shows that a certain threshold size is required for both asexual and sexual reproduction. The shoot size is negatively correlated with density, whereas the numbers of asexual gemmae and the proportions of developmental stages are not affected by shoot density. Furthermore, provisional estimates are calculated for the transitions from early developmental stages to reproductively mature stages. The results indicate that the initial phases of the gametophyte development are the most vulnerable.