Phylogeny of Cucurbitales inferred from nine chloroplast, mitochondrial and nuclear loci
LI-BING ZHANG and SUSANNE S. RENNER. Department of Biology, University of Missouri-St. Louis, St. Louis, MO 63121. Email: [email protected]; [email protected]
Based on rbcL (Setoguchi et al. 1999; Schwarzbach & Ricklefs 2000), Cucurbitales comprise Anisophylleaceae, Begoniaceae, Coriariaceae, Corynocarpaceae, Cucurbitaceae, Datiscaceae, and Tetramelaceae. To further investigate the position of Anisophylleaceae and to approp- riately root a large molecular phylogeny of Cucurbitaceae, we are investigating family relationships in Cucurbitales. Previous molecular data have identified Fagales as the sister clade to Cucurbitales, but prior to our project, Anisophylleaceae had been weakly sampled and only sequenced for rbcL, which provided limited support for the monophyly of Cucurbitales. We have combined nuclear 18S, the chloroplast genes atpB, matK, ndhF, and rbcL, the trnL intron, the rpl20-rps12 and trnL-trnF spacers, and the mitochondrial nad1 b/c intron (together 9302 aligned bp) for 25 representatives of the ingroup families and two fagalean outgroups. Cucurbitales are strongly monophyletic, and Anisophylleaceae are sister to the remaining families, which form a Marah fabaceus trichotomy of (1) Cucurbitaceae, (2) Coriariaceae and Corynocarpaceae, and (3) Begoniaceae Anisophyllea fallax (Datiscaceae, Tetramelaceae). The relationship between the last three families has also been addressed with restriction site and ITS data (Rieseberg et al., 1992; Swensen et al., 1998),as well as flower morphology, which indicated a close relationship of Datiscaceae and Tetramelaceae. With the exception of a few Coriariaceae and Corynocarpaceae, Cucurbitales all have unisexual flowers, and plants are usually monoecious, with repeated shifts to dioecy in Begonia, Cucurbitaceae, Datisca cannabina, and Tetramelaceae. Because molecular data do not yet resolve family
Photo: G. E. Schatz Photo: P. Endress relationships in the Cucurbitales, it is unclear whether the few perfect- flowered Coriariaceae / Corynocarpaceae represent basal lines or reversals from unisexual to perfect flowers. The latter is exceedingly rare, and we are currently exploring additional DNA markers specifically to resolve their position in the order. Juglans nigra Anisophylleaceae Cucurbitaceae Fagus grandifolia
94 Anisophyllea corneri Corynocarpus laevigatus 95 Anisophyllea obtusifolia Begonia evansii Anisophylleaceae 100 Anisophyllea fallax
Combretocarpus rotundatus
100 Begonia herbacea 100 Begonia oxyloba Begoniaceae Hillebrandia sandwicensis 100 Datisca glomerata 100 Datiscaceae Datisca cannabina
Photo: G. C. Linney Octomeles sumatrana 100 Tetramelaceae Photo: B. Glick Tetrameles nudiflora
Coriaria ruscifolia 100 Coriariaceae 100 Coriaria sarmentosa
Corynocarpus laevigatus Corynocarpaceae
Coccinia sessilifolia 100 Begoniaceae Corynocarpaceae Lagenaria brevifolia
Dendrosicyos socotranus
100 Gurania megistantha 100 100 Coriaria myrtifolia Seyrigia humbertii Datisca cannabina Ecballium elaterium Cucurbitaceae
Marah macrocarpus
100 96 Schizopepon bryoniifolius
50 changes 98 Gynostemma pentaphyllum Neoalsomitra sarcophylla 88 Xerosicyos danguyi
(Single most parsimonious tree, CI = 0.72 RI =0.79 bootstraps at branches from 100 replicates)
Photo: G. Gerlach & P. Endress Photo: P. Endress Octomeles sumatrana
Coriariaceae Photo: W. Takeuchi Tetramelaceae Datiscaceae