Impact of habitat fragmentation on genetic structure of Capparis spinosa populations revealed by ISSR markers

The results from empirical studies on the impact of habitat fragmentation on genetic variation of populations are controversial, ranging from negative to positive effects. This contradiction has been attributed to either species characteristics (e.g. plant life history) or environmental components (e.g. the scale of habitat fragmentation). To examine the role of DNA marker types on these effects, we carried out a comparative study of seven populations of Capparis spinosa L. (caper, Capparaceae) using ISSR markers and compared these results with those obtained previously using RAPD markers. Although both ISSR and RAPD markers showed high consistency and indicated that genetic variation in populations was not correlated with either geographical distance (P ≥ 0.47, P ≥ 0.83; for ISSR and RAPD, respectively) or altitude (P ≥ 0.535, P ≥ 0.419; for ISSR and RAPD respectively), the levels of variation were related to population size. ISSR analysis showed that genetic variation did not significantly differ between small and large populations (P ≥ 0.4149), while RAPD analysis indicated significant effect of population size on this variation (P ≤ 0.002). This may suggest that, in addition to species and environmental components, types of DNA markers used for assessing population genetic variations affect results on the impact of fragmentation on genetic variation.