Comparative floral structure and systematics in the sarracenioid clade (Actinidiaceae, Roridulaceae and Sarraceniaceae) of Ericales

Abstract

In molecular phylogenetic studies, Actinidiaceae, Roridulaceae and Sarraceniaceae form a strongly supported clade, which is sister to the ericoid clade (Clethraceae, Cyrillaceae and Ericaceae). In pre-molecular classifications, the sarracenioid families were often not affiliated with other ericalean taxa or considered to be closely related with each other, as they differ conspicuously in their habit, mode of nutrient uptake and/or superficial floral structure. In order to interpret the findings of molecular phylogenetic analyses from a morphological point of view, a detailed comparative study of floral morphology, anatomy and histology of these three families is presented. In addition, earlier literature is reviewed. The three families share a series of general and, at the level of Ericales, most likely plesiomorphic floral features, including pentamery, actinomorphy and hypogyny. Other, more specialized features, such as polystemony, choripetaly and integument number, turn out to be homoplasious in the sarracenioid clade. A floral feature shared by the three families is late anther inversion, which, in Ericales, is restricted to the sarracenioids and ericoids. Potential synapomorphies for the sarracenioids include tanniferous floral tissue, vesicles that appear to contain condensed tannins in floral tissue, proximally thick petals, ovules with a nucellar hypostase and the presence of iridoid compounds. For the subclade of Actinidiaceae and Roridulaceae, potential synapomorphies include the presence of raphides and mucilage cells in floral tissue, a secretory inner surface in the gynoecium and the absence of synlateral vasculature in the ovary. Floral features in the clade are discussed and compared with the other families of Ericales. Further structural studies in other clades of Ericales and a well-resolved molecular phylogeny of the order are needed to test the systematic value of these features further. Some features may turn out to be true synapomorphies, whereas others may turn out to be widespread in Ericales and therefore plesiomorphic for the order.

Rariglanda jerseyensis, a new ericalean fossil flower from the Late Cretaceous of New Jersey

“…The matrix comprised 25 taxa (Appendix A), representing exemplar genera from all families and major clades in the core Ericales, and 13 morphological characters (Appendix B). The final morphological matrix included only characters that could be observed in the fossil taxa, and were scored based on published descriptions or matrices (e.g., Luteyn et al 1995;Kron et al 2002;Millan and Crepet 2014;Löfstrand and Schönenberger 2015a), and direct observations from herbarium specimens from BH. All molecular characters were coded as missing for both fossils.…”

Early floral development and androecium organization in the sarracenioid clade (Actinidiaceae, Roridulaceae and Sarraceniaceae) of Ericales

“…The sarracenioid clade consists of three families (Actinidiaceae, Roridulaceae and Sarraceniaceae; Löfstrand & Schönenberger, , b) and is sister to the ericoid clade (Clethraceae, Cyrillaceae and Ericaceae; Schönenberger, Anderberg & Sytsma, ). The sarracenioid and ericoid clades together form the so‐called core Ericales (Schönenberger et al ., ).…”

“…ex. L., are polystemonous (Löfstrand & Schönenberger, ), whereas the ericoid clade is largely characterized by diplostemonous flowers.…”

“…and Saurauia p.p . ; Löfstrand & Schönenberger, ). The perianth is pentamerous in most taxa (variable in Actinidia , Saurauia and Heliamphora ).…”

“…The perianth is pentamerous in most taxa (variable in Actinidia , Saurauia and Heliamphora ). Sepals and petals are free or only basally united in the respective organ whorl (Löfstrand & Schönenberger, ). Stamens are mostly free from each other and the corolla.…”