A SYSTEMATIC STUDY OF THREE GENERA OF ARALIACEAE ENDEMIC TO OR CENTERED IN NEW CALEDONIA: DELARBREA, MYODOCARPUS, AND PSEUDOSCIADIUM (PHYTOGEOGRAPHY).

摘要

Delarabrea, Myodocarpus, and Pseudosciadium comprise a well-delimited, monophyletic group within Araliaceae. Both Myodocarpus and Pseudosciadium are endemic to the isolated Pacific island of New Caledonia; Delarbrea is centered there, with one subspecies also extending through Vanuatu and the Solomon Islands to the Moluccas and Lesser Sunda Islands, and another species endemic to Queensland, Australia. These genera share a number of features, one of which, the presence of large secretory oil vesicles in the pericarp of their fruit, represents a synapomorphy that distinguishes them from all other members of the family.; A brief summary of the geology, phytogeography, and vegetation of New Caledonia is presented. This is followed by a discussion of the relationships, geographic distribution, and evolution of the group comprising Delarbrea, Myodocarpus, and Pseudosciadium, and a review of morphological and fruit anatomical characters of the individual genera. Phytogeographic and morphological evidence suggests that this group probably represents an old lineage that may have been among the many remnants of the late Cretaceous - early Tertiary flora of Australia that have survived in New Caledonia but were eliminated from Australia after their separation. These data also indicate that Myodocarpus is derived from one of the two other genera or from an ancestor to them, and does not represent a "phylogenetic link" to the related Apiaceae, as suggested by earlier workers. Cytological data indicate that all three genera have a chromosome number of n = 12, supporting the hypothesis that this represents the basic number for Araliaceae.; A systematic revision is presented in which ten species of Myodocarpus and six species of Delarbrea (two of which are further divided into two subspecies each) are recognized; Pseudosciadium is a monotypic genus. Analytical keys are provided to the genera, species, and subspecies. A complete synonymy and detailed description are provided for each taxon, followed by a discussion of its habitat, phenology, and typification, as well as an illustration and distribution map. Three new taxa are discussed (D. paradoxa subsp. depauperata, M. angustialatus, and M. nervatus), and two new combinations are proposed; these will be validly published elsewhere.