ABSTRACT Discocactus zehntneri subsp. petr-halfari, an endangered taxon, is represented by a single population in an anthropized area of Bahia, Brazil, where it is suffering due to extreme extractivism. Thus, information about this cactus, such as its reproductive patterns, is urgently needed to support conservation strategies. A population genetics approach was used to determine if this subspecies has a preferential pattern of reproduction. We sampled 18 individuals, both with and without connection to parental plants, from five clumps and assessed their diversity and genetic structure using five ISSR markers. The results revealed two clumps that are genetically supported by the presence of genetically equal individuals. The other three groups presented individuals that are genetically different and similar to individuals in other clumps. These findings suggest that this subspecies has sexual and clonal reproduction and that its environmental distribution might be shaped by events of dispersion. In addition, a possible hybrid origin may explain its rates of genetic diversity. Despite all these factors, this taxon is in danger and so the development of conservation strategies to preserve its population are urgently needed, including in situ and ex situ actions such as the micropropagation in vitro, living collections and cryopreservation.

Abstract Mayacaceae Kunth is an aquatic plant family that currently comprises a single genus, and four to six accepted species. Most of them are widely distributed in the Neotropics, with the exception of Mayaca baumii Gürke, which is endemic to Africa. This family still encompasses taxonomical problems involving mostly nomen- clatural issues and the positioning of the family within the Poales, which remains not definite, though several efforts have being made in this direction. Besides all this, the family also suffers from limited studies with different approaches, such as embryological, palinological, phylogenetic and ecological ones. Considering all this problems, the present work make an overview of Mayacaceae to show the main problems that still surround the family and to indicate some directions for future studies.