Search

Woody stems that have completed some maturation of metaxylem elements should not be capable of further axial extension ("secondary stem lengthening"). However, this mechanism has been claimed by Renninger and Phillips (American Journal of Botany 99: 607-613) to be a feature of the palm Iriartea deltoidea. In response, we describe structural features of palm stems based on extensive known features of their anatomy and development. In addition to the inability of metaxylem vessels to extend after they are mature, fully differentiated fibers of the vascular bundle sheath, which would exist at the time of proposed stem elongation would not be capable of belated extension. "Vessel spirals" claimed by these authors to be capable of stretching to accommodate secondary stem lengthening does not refer to well-established features of the course of vascular bundles. The approach adopted by Renninger and Phillips simply measures stems of different sizes as an implied developmental series. Consequently, results do not take into account changes in the development of the palm stem as it ages. The existence of secondary stem lengthening in the palm Iriartea deltoidea, something never before observed in any tree, cannot occur because it would indeed disrupt mature metaxylem vessels and would also require the secondary extension of mature lignified fibers.

Cladistic analyses are presented of matK sequence data as well as a nonmolecular database for an identical set of exemplar species chosen to represent the core genera or groups of genera in Myrtaceae. Eleven robust clades are recognized on the molecular data. Polyphyly of the previously recognized Metrosideros and Leptospermum alliances is confirmed, and several smaller informal taxonomic groupings are recognized from among the members of the former alliance, i.e., the Tristania, Tristaniopsis, Metrosideros, and Lophostemon groups. The nonmolecular analysis provides only limited resolution of relationships. A degree of congruence exists between the two analyses in that two separate fleshy-fruited clades, the Acmena and Myrtoid groups, are identified, as are the Eucalypt and Tristania groups, and Psiloxylon and Heteropyxis are the first lineages to diverge in both analyses. A combined analysis recognized all 11 clades that received strong support from the molecular data. A high level of homoplasy is revealed in many of the nonmolecular characters when they are examined against the combined estimate of phylogeny.

Morphological and ITS (internal transcribed spacer) sequence data for 40 species of the Austral-Pacific genera Camptacra, Kippistia, Minuria, Peripleura, Tetramolopium, and Vittadinia as well as one semiherbaceous species of Olearia were subjected to cladistic analysis, separately and together. Minuria, Peripleura, and Tetramolopium are paraphyletic as currently defined. Tetramolopium vagans from Australia appears to represent an undescribed genus. Both Kippistia suadefolia and Peripleura diffusa show close affinity to Minuria species, and Minuria macrorhiza appears to contain two distinct but closely related species. Vittadinia and the remaining species of Tetramolopium and Peripleura form a strong affinity group. The distribution of indels and the combined analysis each provide evidence that the Hawaiian and Cook Island species of Tetramolopium are descended from New Guinea species. The combined analysis also suggests that the Cook Island species T. mitiaroense is sister to the Hawaiian clade. Olearia arguta groups strongly with Camptacra and shows no close affinity with either of the arborescent species of Olearia used to root these analyses. Marked homoplasy among morphological characters indicates why generic delimitation in the group has been problematic.

Parsimony analysis of matK and rbcL sequence data, together with a nonmolecular database, yielded a well-resolved phylogeny of Cupressaceae sensu lato. Monophyly of Cupressaceae sensu stricto is well supported, and separate northern and southern hemisphere subclades are resolved, with Tetraclinis within the northern subclade; there is no support for any of the tribes sensu Li. Taxodiaceae comprise five separate lineages. Chamaecyparis nootkatensis falls within Cupressus, clustering with a robust clade of New World species. Libocedrus Florin is paraphyletic and should incorporate Pilgerodendron. Evolution of several characters of wood and leaf anatomy and chemistry is discussed in light of this estimate of the phylogeny; numerous parallelisms are apparent. A new infrafamilial classification is proposed in which seven subfamilies are recognized: Callitroideae Saxton, Athrotaxidoideae Quinn, Cunninghamioideae (Sieb. & Zucc.) Quinn, Cupressoideae Rich. ex Sweet, Sequoioideae (Luerss.) Quinn, Taiwanioideae (Hayata) Quinn, Taxodioideae Endl. ex K. Koch. The rbcL sequence for Taxodium distichum is corrected, and the implications for a previously published estimate of the minimum rate of divergence of the gene since the Miocene are highlighted.