Phylogenetic analyses of nucleotide sequences confirm a unique plant intercontinental disjunction between tropical Africa, the Caribbean, and the Hawaiian Islands

Abstract

Phylogenetic analyses of nucleotide sequences of the internal transcribed spacers and 5.8 regions of the nuclear ribosomal DNA and of the trnH-psbA spacer of the chloroplast genome confirm that the three taxa of the Jacquemontia ovalifolia (Choicy) Hallier f. complex (Convolvulaceae) form a monophyletic group. Levels of nucleotide divergence and morphological differentiation among these taxa support the view that each should be recognized as distinct species. These three species display unique intercontinental disjunction, with one species endemic to Hawaii (Jacquemontia sandwicensis A. Gray.), another restricted to eastern Mexico and the Antilles [Jacquemontia obcordata (Millspaugh) House], and the third confined to East and West Africa (J. ovalifolia). The Caribbean and Hawaiian species are sister taxa and are another example of a biogeographical link between the Caribbean Basin and Polynesia. We provide a brief conservation review of the three taxa based on our collective field work and investigations; it is apparent that J. obcordata is highly threatened and declining in the Caribbean.