KELCHNER, SCOT A.1,2*, JUDY G. WEST1, MIKE C. CRISP2, and ROBERT J. CHINNOCK3. 1Centre for Plant Biodiversity Research, CSIRO Plant Industry, G.P.O. Box 1600, Canberra, ACT 2601, AUSTRALIA; 2Division of Botany and Zoology, The Australian National University, Canberra, AUSTRALIA; 3State Herbarium of South Australia, Adelaide, AUSTRALIA. - The Caribbean Bontia daphnoides and its Australian family Myoporaceae (Lamiales): evidence of an extreme dispersal event from morphological data and rpl16 intron sequences.
The monotypic genus Bontia presents an interesting
biogeographic puzzle. Bontia daphnoides is an endemic of the
Caribbean islands, but is taxonomically classified as a member of the
southern-hemisphere Old World family Myoporaceae. Ninety-five percent
of the 250 species of Myoporaceae (sensu R. J. Chinnock; in review)
are arid/semiarid shrubs and small trees endemic to Australia. Only
six species in the family occur north of the equator, and of these all
but Bontia daphnoides are locally distributed in the western
Pacific. The supposed sister lineage to the family is the semiarid
Central American tribe Leucophylleae (Scrophulariaceae), which shares
anatomical similarities with Myoporaceae. Is the evolutionary history
of the Caribbean Bontia daphnoides truly shared with Australian
Myoporaceae, or has it instead descended from the geographically
neighboring Leucophylleae? As part of an ongoing phylogenetic analysis
of generic relationships in Myoporaceae, our first two data sets
provide some evidence of historical relationships between these
anatomically similar lineages. Parsimony and likelihood topologies
have been constructed for morphological cladistic characters and
aligned rpl16 intron sequences, respectively. In these
topologies, Leucophylleae is a lineage independent of a monophyletic
Myoporaceae (sensu Chinnock), and Bontia is derived from within
the largely arid Australian genus Eremophila. The results
suggest that the current position of Bontia daphnoides in the
eastern Atlantic is due to dispersal from an Australian ancestral
lineage.
Key words: biogeography, Bontia, morphological phylogeny, Myoporaceae, rpl16 intron, transpacific dispersal