Himanshi first of all kindly mention about the species under question. The male and female plant of which species? For a general view if the male and female sex are being determined by different ploidy levels or the set of female plants under study belong to different geographical locations or the transposons are linked to sex chromosome X . or There can be similar other explanations for higher diversity in female plants. Secondly if the ISSR markers used in study are specifically amplifying more in female plants and resulting more number of amplicons then it can also be a probable reason.