Hydrostachys

Abstract: Nuclear 26S rDNA sequences were used to corroborate and test previously published matK-rbcL-based hypotheses of phylogenetic relationships in Cornales. Sequences were generated for 53 taxa including Alangium, Camptotheca, Cornus, Curtisia, Davidia, Diplopanax, Mastixia, Nyssa, and four families: Grubbiaceae, Hydrangeaceae, Hydrostachyaceae, and Loasaceae. Fifteen taxa from asterids were used as outgroups. The 26S rDNA sequences were initially analyzed separately and then combined with matK-rbcL sequences, using both parsimony and maximum likelihood methods. Eight strongly supported major clades were identified within Cornales by all analyses: Cornus, Alangium, nyssoids (Nyssa, Davidia, and Camptotheca), mastixioids (Mastixia and Diplopanax), Hydrangeaceae, Loasaceae, Grubbia-Curtisia, and Hydrostachys. However, relationships among the major lineages are not strongly supported in either 26S rDNA or combined 26S rDNA-matK-rbcL topologies, except for the sister relationships between Cornus and Alangium and between nyssoids and mastixioids in the tree from combined data. Discrepancies in relationships among major lineages, especially the placement of the long-branched Hydrostachys, were found between parsimony and maximum likelihood trees in all analyses. Incongruence between the 26S rDNA and matK-rbcL data sets was suggested, where Hydrangeaceae was found to be largely responsible for the incongruence. The long branch of Hydrostachys revealed in previous analyses was reduced significantly with more sampling. Maximum likelihood analysis of combined 26S rDNA-matK-rbcL sequences suggested that Hydrostachys might be sister to the remainder of Cornales, that Cornus-Alangium are sisters, that nyssoids-mastixioids are sisters, and that Hydrangeaceae-Loasaceae are sisters, consistent with previous analyses of matK-rbcL sequence data.

Abstract: DNA sequences of the plastid gene matK were used alone and in combination with rbcL and morphological data in analyses of phylogenetic relationships in Hydrangeaceae. A suggested relationship of Hydrostachys to Hydrangeaceae was examined, but the maximum parsimony analyses of the matK data and the data set that combines matK and rbcL place Hydrostachys outside of Hydrangeaceae. The DNA sequence data sets both alone and in combination produced congruent results. A Jamesia + Fendlera clade (= subfamily Jamesioideae) was the sister of the rest of the family (= subfamily Hydrangeoideae). Two tribes, Philadelpheae and Hydrangeeae, are recognized in Hydrangeoideae. Philadelpheae included three primary clades: (1) Philadelphus + Carpenteria, (2) Deutzia + Kirengeshoma, and (3) Fendlerella + Whipplea. Relationships in Hydrangeeae remain poorly resolved. A Cardiandra + Deinanthe clade was placed robustly as the sister of the rest of the Hydrangeeae only in analyses in which matK sequences were combined with other ...

Abstract: Summary Albach, D. C., Soltis, D. E., Chase, M. W. & Soltis, P. S.: Phylogenetic placement of the enigmatic angiosperm Hydrostachys. - Taxon 50: 781-805. 2001. - ISSN 0040-0262. Hydrostachys, an enigmatic aquatic plant genus from Madagascar and southern to central Africa, has been suggested to be related to Lamiales based on embryology, whereas rbcL sequences have indicated a relationship with Hydrangeaceae (Corales). We investigated these hypotheses by combining rbcL with atpB and ndhF sequences and increased taxon sampling in Hydrangeaceae compared to previous analyses. Rates and patterns of molecular evolution vary across ndhF with the 3' portion giving a different result than the 5' portion. The highly divergent sequences of Hydrostachys make phylogenetic placement difficult, but maximum parsimony and maximum likelihood analyses of combined data sets agree in placing Hydrostachys within Hydrangeaceae, as do separate analyses of rbcL, atpB, and the 5' portion of ndhF. Few morphological and embryological characters support this relationship.

Abstract: Hydrostachys flabellifera, a new species of Hydrostachyaceae found in a stream in Manandriana, Madagascar, is described and illustrated herein. It is similar to H. verruculosa and H. laciniata in morphology, but can be distinguished from them by its leaves with sparsely arranged, flabelliform and palmately parted emergences, obvious rachis and the pattern of segments arranged on the male bracts. Molecular phylogenetic analysis of the nuclear ribosomal internal transcribed spacer (ITS) dataset provides a robust support for it as a new species as well.