The distribution of genetic variability in Baccharis concinna (Asteraceae), an endemic, dioecious and threatened shrub of rupestrian fields of Brazil

Distribution of genetic variability may becorrelated with life history traits, such asreproductive system, pollination, seeddispersal mode, geographical distribution, andlocal abundance. We used RAPD markers to studythe distribution of genetic variability of sixpopulations of Baccharis concinna(Asteraceae), a rare, dioecious and threatenedshrub, endemic to Serra do Cipó,southeastern Brazil, along an altitudinalgradient, ranging from 950 to 1300 m above sealevel. From 113 RAPD markers, 35 wererestricted to one of the six populations.Genetic variability distribution in B.concinna populations was weakly related to thealtitudinal gradient. The largest proportion ofthe genetic variability was due to variationwithin populations (82.82%, P < 0.001), while17.18% (P < 0.001) was due to variation amongpopulations from different elevations.Similarity among populations along thealtitudinal gradient was high, ranging from 65to 74%, suggesting an intensive gene flowamong them or a recent fragmentation of anancient population into many small populations.Dioecy and other life history traits such aswind pollination and seed dispersal mayinfluence the distribution of the geneticvariability in this species. In addition, fireand habitat fragmentation represent otherimportant factors that influence thesurvivorship of this rare and threatenedspecies, and hence the distribution of itsgenetic variability.