Cone and ovule development inCunninghamiaandTaiwania(Cupressaceae sensu lato) and its significance for conifer evolution

Abstract

We examined the early developmental stages of the seed cones and seeds of two conifer genera, Cunninghamia and Taiwania, using scanning electron microscope (SEM) images of freshly collected material. In recent similar studies, these two taxa were not described. The present paper aims to fill that gap. Both genera appear to have features crucial to the understanding of the evolution of the cupressaceous cone, characteristic of the families Cupressaceae and Taxodiaceae, and provide further evidence for the need to merge these families. These features are: the ovuliferous scale in Cunninghamia develops as a small lobe with each of three ovules; in Taiwania these lobes are absent, but a small ridge could be a vestige of them. In neither of these two genera does an ovuliferous scale develop to maturity and only limited intercalary growth transforms the bracts, of which only their width and final shape distinguishes them from sterile leaves. Thus, the bracts, not the ovuliferous scales, form the mature cone in these two genera. This trend is continued in more derived genera of Cupressaceae. Another key extant taxon that has helped to elucidate the evolution of this type of conifer cone is Sciadopitys; similar studies have already been done on this genus, and we compared our findings to them. We also considered certain fossil Mesozoic conifer cones, which shed further light on the evolution of the cupressaceous cone. The evidence from these various genera strongly indicates that recently reconstructed phylogenies of gymnosperms based on molecular evidence from extant taxa do not reflect the evolution that actually happened. Such studies need to take into account nonmolecular evidence, as detailed here.

Voltziales y Pinales (= Coniferales) de la Formación Cortaderita (Triásico Medio), Argentina, y su implicancia en la reconstrucción de las coníferas triásicas

“…es el más diverso y ampliamente distribuido dentro de las coníferas, con 30 géneros vivientes (Taylor et al, 2009). Dentro del mismo, se incluyen tanto a las antiguas Taxodiaceae (consideradas como el grado basal del linaje) y a las Cupressaceae s.s (consideradas el clado más derivado del grupo) (Eckenwalder, 1976;Gadek et al, 2000;Farjon & Ortiz García, 2003;Farjon, 2005). Los leños de ambos grupos presentan diversas semejanzas; i.e.…”

Whole-Plant Reconstruction and Phylogenetic Relationships of Elatides zhoui sp. nov. (Cupressaceae) from the Early Cretaceous of Mongolia

“…Relationships among taxodiaceous Cupressaceae are not well resolved by analyses of morphological data alone (Farjon et al 2002;Farjon 2005;Escapa et al 2008). We therefore also performed analyses using a molecular scaffold (Springer et al 2001) based on recent studies of conifer phylogeny (Leslie et al 2012;Mao et al 2012), which constrained the relationships of extant taxa to correspond to those recovered from analyses based on molecular phylogenetics.…”

“…ex Endl.) Quinn (Gadek et al 2000) and includes two extant species that are restricted to East Asia (Farjon 2005). Molecular phylogenetics resolves Cunninghamia as the sister group to all other extant Cupressaceae sensu lato (Gadek et al 2000;Rai et al 2008;Leslie et al 2012;Mao et al 2012).…”

Variability of male cones in Chamaecyparis as an example for Cupressaceae male cones

“…JAGEL & STÜTZEL 2001a, 2001bFARJON 2002FARJON , 2003SCHULZ et al 2003) and the morphological work was facilitated by the revision of the Cupressaceae nomenclature (FARJON 2001), information about male cones is less known. To date a lot of species descriptions miss information about the male cones (e.g.…”