matK DNA Sequences and Phylogenetic Reconstruction in Saxifragaceae s. str.

Comparative DNA sequencing of matK, a maturase coding gene located within the intron of the chloroplast gene trnK, was evaluated for phylogenetic utility using genera of Saxi- fragaceae s. str. The entire matK gene was sequenced for two members of the family, Sullivantia sullivantii and Saxifraga integrifolia. Comparison of base substitution rates between these two species indicated that matK evolves approximately three-fold faster than rbcL. Comparative sequencing of 754 base pairs within matK was subsequently conducted using 25 genera in Saxifragaceae s. str. and two outgroup taxa. Summed over the 31 taxa sequenced for this 754 base pair region, 40% of the base positions were variable and 15.6% were potentially informative. Five insertion/deletion events of three or six base pairs were also detected. Skewness and randomization tests both suggest that significant non-random structure is present in the matK data set. Parsimony analyses provided 72 most parsimonious trees of 223 steps (excluding autapomorphies) with a consistency index of 0.565. Several well-supported groups of genera are highly concordant with relationships suggested by two other chloroplast DNA data sets: chloroplast DNA restriction sites and rbcL sequences.