MITOCHONDRIAL-DNA VARIABLE NUMBER TANDEM REPEATS (VNTRS) - UTILITY AND PROBLEMS IN MOLECULAR ECOLOGY

Analysis of mitochondrial (mt)DNA size polymorphism in the form of var iable number tandem repeats (mtVNTRs) has become an increasingly popul ar methodology for addressing questions in molecular ecology. When det ected by PCR, mtVNTR analysis can provide a sensitive, rapid, and cost -effective measure of genetic variability that may be exploited in stu dies of population differentiation and biogeography. Despite the emerg ence of this approach, there has been little critical evaluation of it s success or utility as a practical tool. In this review, we identify problematic methodological, theoretical and interpretive factors that can influence the utility of mtVNTR analysis. The reliability of the p rocedure is considered in terms of both detection of alleles and scori ng of intra-individual allele frequencies. While many of the potential technical problems of the technique do not raise serious practical co ncerns, this rapid and sensitive methodology is seriously compromised by the difficulty of reliably assessing allele frequencies, of assayin g only germline tissue, and in our ignorance of the mechanisms generat ing mtVNTR diversity. Thus, although there is a considerable potential for mtVNTR pilot studies to assess genetic diversity, the utility of the technique to resolve broader questions in molecular ecology should be treated cautiously until such a time as the system is better under stood.