The distribution and systematic relevance of the androecial character oligomery

Abstract

Localization of the stamens can be approached by a preliminary distinction between two characters, oligomery and polymery, occurring in two different groups of taxa, respectively the oligomerous complex and the polymerous complex. Oligomery is described by four character states standing in a close semophyletic relationship: diplostemony, obdiplostemony, haplostemony and obhaplostemony. Each character state is analysed for its distribution and systematic value. Diplostemony is the synapomorphic character state for the oligomerous line and has arisen once from a polymerous ancestor or in parallel in different lines. Obdiplostemony arises ontogenetically in three different ways. Loss of one whorl leads either to obhaplostemony, or haplostemony; both character states are believed to represent evolutionary steps of noreturn. Secondary increases and reductions of the stamens within a whorl are seen as expressions of the intrinsic variability of the character states and should not be homologized with them. Stamen numbers can be increased by the building-up of complex primordia or by secondary receptacular growth. Reductions of stamens affect one or two whorls of stamens and are caused by lack of space, interactions with the gynoecium and zygomorphy. The distribution of the different character states of oligomery is presented on Dahlgrenograms and the androecia of a number of families and their relationships are discussed. The interactions between oligomery and polymery are analysed as guidelines for a global phylogeny of the Magnoliatae. 0 1995 The Linnean Society of London

Comparative floral structure and systematics in Crossosomatales (Crossosomataceae, Stachyuraceae, Staphyleaceae, Aphloiaceae, Geissolomataceae, Ixerbaceae, Strasburgeriaceae)

“…Flowers are diplostemonous in Crossosomataceae ( Apacheria , Glossopetalon , Velascoa ; Sosa & Chase, 2003), Stachyurus , and Geissoloma ; obdiplostemonous in Strasburgeria (van Tieghem, 1907; Engler, 1925). Ronse Decraene & Smets (1995) mention obdiplostemony for the apetalous Geissoloma ; however, there is normal alternation of the floral whorls (see Dahlgren & Rao, 1969). It may be argued that the term obdiplostemony is not useful for apetalous flowers.…”

“…Staphyleaceae were compared with Melianthaceae because of the bladder‐like fruits and pinnate leaves. As in Crossosomatales, the sepals are imbricate, and the androecia are often obdiplostemonous (Eckert, 1966; Ronse Decraene & Smets, 1995). The carpels have dorsal ridges and luminous locules that in some taxa taper into the style (Sauer, 1933; Ronse Decraene & Smets, 1999; Ronse Decraene et al ., 2001), seeds are campylotropous (Geraniaceae) (Boesewinkel, 1988).…”

Anacardiaceae

“…3G) and Mangifera, where there are one or more fertile stamens and a series of staminodes, and Fegimanra (Fig. Ronse Decraene and Smets (1995) stated that Anacardiaceae are strictly diplostemonous as compared to Burseraceae, which are all obdiplostemonous, but obdiplostemony was recently reported in the cashew family by Bachelier andEndress (2007, 2009). Ronse Decraene and Smets (1995) stated that Anacardiaceae are strictly diplostemonous as compared to Burseraceae, which are all obdiplostemonous, but obdiplostemony was recently reported in the cashew family by Bachelier andEndress (2007, 2009).…”

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

“…Additional ontogenetic studies and reconstructions of character evolution on a large scale in Ericales are needed to determine unequivocally the origin of the second whorl of stamens in two‐whorled ericalean taxa. If the ancestral state in all (or part of) Ericales is indeed polystemonous androecia, this implies that the various supra‐ and infrafamilial groups of Ericales with two‐whorled androecia evolved independently; for example, Ronse Decraene & Smets (, ) presented a compelling argument that two‐whorled androecia evolved from polystemonous androecia.…”