Comparative floral structure and systematics in the balsaminoid clade including Balsaminaceae, Marcgraviaceae and Tetrameristaceae (Ericales)

Abstract

Based on molecular phylogenetic studies, Balsaminaceae, Tetrameristaceae (including Pellicieraceae) and Marcgraviaceae form the strongly supported first branching clade in the asterid order Ericales. Marcgraviaceae and Tetrameristaceae were proposed to be closely related in pre‐molecular studies, but the systematic position of Balsaminaceae has been controversial for some time and a relationship with the other two families was never suggested in pre‐molecular/pre‐cladistic times. However, interfamilial relationships in the clade are still unclear because of conflicting phylogenetic hypotheses from molecular analyses. In order to assess the validity of these molecular hypotheses from a morphological point of view, the floral morphology, anatomy and histology of Balsaminaceae, Tetrameristaceae and Marcgraviaceae are comparatively studied in detail. In addition, earlier literature is reviewed. The monophyly of the balsaminoid clade is strongly supported by floral structure, and a series of potential floral synapomorphies is identified for the clade. Prominent features shared by the three families include broad and dorsiventrally flattened filaments, thread‐like structures lining the stomia of dehisced anthers, secretory inner morphological surfaces of the gynoecium, ovules intermediate between uni‐ and bitegmic, incompletely tenuinucellar ovules, fruits with persistent style and stigma, seeds lacking endosperm and several anatomical/histological traits. The families are also distinctive because the bracts and/or sepals are petaloid and nectariferous. Further, the floral structure supports a sister group relationship between Balsaminaceae and Tetrameristaceae rather than any of the other possible interfamilial relationships. These two families share a caducous calyx, post‐genital fusion/coherence of filaments and ovary surface, latrorse anther dehiscence, commissural carpel lobes and ovules with a thickened funiculus and a constricted chalazal region. The occurrence of these features in Ericales is discussed. Future structural studies in other ericalean lineages and additional molecular studies are needed to further test these features with respect to their systematic value for the balsaminoid clade. Some may turn out to be true synapomorphies, whereas others may be recognized as plesiomorphies, as they may be more widely spread in Ericales than currently thought. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 325–386.

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

“…For more information on mucilage cells, raphides and stone cells, see, for example, Schönenberger et al . () and von Balthazar & Schönenberger (). For more information on condensed tannins, see Lees, Hinks & Suttill (), Skadhauge, Thomsen & von Wettstein (), Bussotti et al .…”

“…The families and genera of Ericales are highly diverse at all levels of their structure and biology, particularly so at the level of floral structure and function, for which the evolution of many characters shows extensive homoplasy (Schönenberger et al ., ). So far, only the clades comprising Balsaminaceae, Marcgraviaceae and Tetrameristaceae (von Balthazar & Schönenberger, ) and Fouquieriaceae and Polemoniaceae (Schönenberger, ) have been comparatively studied in detail at the floral morphological level.…”

“…As a fourth in a series of studies dealing with comparative floral morphology, anatomy and histology (Schönenberger, ; Schönenberger, von Balthazar & Sytsma, ; von Balthazar & Schönenberger, ), the present study focuses on the sarracenioid clade, comprising the families Actinidiaceae, Roridulaceae and Sarraceniaceae. In pre‐molecular times, the three families were considered to belong to three different plant orders, in two different subclasses of angiosperms: Actinidiaceae in Theales of Dilleniidae, Roridulaceae in Rosales of Rosidae and Sarraceniaceae in Nepenthales of Dilleniidae (Cronquist, ).…”

Divergent genome sizes reflect the infrafamilial subdivision of the neotropical woody Marcgraviaceae

“…Källersjö et al ., ; Nandi, Chase & Endress, ; Savolainen et al ., ; Geuten et al ., ; Soltis et al ., ). This clade is characterized by the possession of raphide sacs that are visible as white pockets in stem sections and by flower morphological traits (von Balthazar & Schönenberger, ). Geuten et al .…”

Asterids

“…Therefore, new comparative morphological and anatomical studies are greatly needed. Here, von Balthazar and Schönenberger () present a comparative study of floral structure of the balsaminoid clade (Ericales). The balsaminoids may serve as a good example of a clade that was first found only based on molecular data and that seemed surprising when considering morphology.…”