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Phylogenetic relationships within Korthalsella (Viscaceae) based on nuclear ITS and plastid trn L ‐ F sequence data
Author(s) -
Molvray Mia,
Kores Paul J.,
Chase Mark W.
Publication year - 1999
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.2307/2656940
Subject(s) - biology , monophyly , phylogenetic tree , genus , evolutionary biology , sister group , taxon , clade , botany , genetics , gene
The nuclear encoded internal transcribed spacer (ITS) region and the plastid encoded trnL‐F region were sequenced for 25 populations of Korthalsella , a genus of reduced, monoecious, Old World misletoes. The molecular study confirms the hypothesis that branch shape and cladotaxy (the arrangement of branches with respect to their parent axis) are unreliable indicators of relationship in the genus and demonstrates that many of the taxa previously recognized are not monophyletic. Both gene regions identify three major subgroups within the genus and find lower level relationships within these subgroups highly correlated with geographic distance. An analysis based upon 18S and rbcL sequences identifies Ginalloa as the sister group to Korthalsella , which together with the branching order within the genus, indicates that Korthalsella originated in Papuasia and aids in elucidating evolution of the peculiar inflorescence structure. There are problems associated with species delimitation when evolutionary units are more restricted than morphological lineages, and justification is offered for recognizing only morphologically diagnosable monophyletic lineages as species. Varying substitution rates and differing modes of inheritance in ITS and trnL‐F result in complementary utility of the two regions for elucidating infrageneric relationships in Korthalsella .