11 - Floral ontogeny of Acacia celastrifolia: an enigmatic mimosoid legume with pronounced polyandry and multiple carpels

Summary

Introduction

The genus Acacia is among the largest plant genera. It was recently treated either in a broad sense with c. 1450 species (Lewis, 2005) or in a strict sense (Acacia s.s. with c. 987 species). The latter follows the re-typification of Acacia with an Australian type (Orchard and Maslin, 2003; see also Murphy, 2008). According to Maslin (1995), the Australian species A. celastrifolia belongs to the ‘Acacia myrtifolia group’ and is most closely related to A. myrtifolia. In molecular studies, only A. myrtifolia was sampled, which is sister to A. pulchella in the Pulchelloidea clade (e.g. Miller and Bayer, 2001; Miller et al., 2003; Murphy et al., 2010). Molecular sampling of the hitherto unsampled A. celastrifolia is highly desirable in order to verify the hypothesized close relationship with A. myrtifolia (e.g. Maslin, 1995).

Flowers of the genus Acacia s.l. are always found in globular heads or spikes. The flowers are (3–)4–5(–6)-merous, with free or united sepals and small reduced petals, which are postgenitally fused and which split open at anthesis. The androecium is composed of many free stamens (i.e. a polyandrous androecium) and the flower is normally terminated by a single superior carpel.