Population biology of the melon cactus Melocactus violaceus subsp. Violaceus (cactaceae) on a Brazilian sandy coastal plain

Abstract

There is a notable lack of ecological information about South American cacti species and the existing information isn’t evenly distributed among life forms and geographic regions. Here, the population structure of a globose cactus species (Melocactus violaceus) on a Brazilian restinga was described and the patterns presented were compared with those reported to other Melocactus species. Cacti density observed on the study area was lower than that reported to other species of the genus. No association between population density and habitat selection or average diameter was found, implying that denso-dependent factors are not important on this population. The population was dominated by young individuals and fitted a log-normal size distribution, which suggests that it was under constant germination and the establishment of seedlings was not subject to unstable environmental conditions. Following a cohort of M. violaceus through time would provide critical information on the population status of this threatened species.