Originally, the species was described by Seemann (1866) as Cussonia gerrardii Seem.
The species is restricted to a few localities in the eastern region of South Africa, in the provinces of KwaZulu-Natal and Mpumalanga ( Burtt and Dickison, 1975). Seemannaralia gerrardii is a small to medium-sized deciduous tree with palmately lobed leaves. Because Seemannaralia remains a relatively poorly known genus and because of its relevance to general questions about gynoecium evolution in Apiales, a detailed study of flowers and fruits of this plant was conducted. Therefore, Seemannaralia may be highly relevant in showing parallelism in the transformation of the gynoecia in different groups of Apiales. As the embedded position of Seemannaralia within Araliaceae is well confirmed by molecular analyses, and direct relationships to Pittosporaceae are very unlikely ( Wen et al., 2001 Plunkett et al., 2004 a Lowry et al., 2004), the structure of its gynoecium should certainly be regarded as derived from the condition which is typical for the majority of Apiales taxa. This monospecific South African genus reportedly possesses a unilocular gynoecium that should be regarded as having a well-developed symplicate zone with apically attached ovules ( Burtt and Dickison, 1975). In this context, the genus Seemannaralia, a member of Araliaceae that appears to be similar to the Pittosporaceae in the ground plan of its gynoecium, could be important for clarifying the evolutionary pathways of floral features in Apiales.
Some molecular data suggest a basal position for Pittosporaceae in relation to the Araliaceae, Myodocarpaceae and Apiacae ( Andersson et al., 2006 Nicolas and Plunkett, 2009) whereas other phylogenetic studies have placed Pittosporaceae as embedded within the Araliaceae–Apiaceae alliance ( Plunkett et al., 1996 Chandler and Plunkett, 2004). Understanding evolutionary transformations of gynoecia in Apiales is in part complicated by the fact that precise relationships between Pittosporaceae and other monophyletic groups within Apiales have not yet been fully resolved. As Stevens (2009) suggests, ‘floral morphology of Pittosporaceae is quite probably derived, rather than representing the plesiomorphic condition from which the distinctive flowers of evolved’. Although no morphological constraints for such transitions have been suggested ( Weberling, 1989 Erbar and Leins, 1996, 2004 Leins and Erbar, 2004), it is highly questionable whether the condition found in Pittosporaceae should be regarded as ancestral within the Apiales. Narayana and Radhakrishnaiah, 1982 Erbar and Leins, 1996).Īs these two types of gynoecia are distinctive at the family level, a trend of evolutionary transition between them within Apiales could be of phylogenetic interest. As a result, members of this family have unilocular ovaries with a single cavity formed between adjacent carpels (e.g. Unlike these three families, the symplicate zone in gynoecia of the Pittosporaceae is much longer than the synascidiate zone, and the ovules are arranged along this zone. these gynoecia are pseudomonomerous ( Baumann-Bodenheim, 1955 Magin, 1977, 1980). The few known cases of unilocular ovaries in members of Araliaceae and Apiaceae appear to result from carpel reduction, i.e. in a cross-zone (also referred to as a ‘Querzone’ e.g. The Araliaceae, Myodocarpaceae and Apiaceae possess mainly bi- or multilocular ovaries in a gynoecium with a long synascidiate zone and a very short symplicate zone, with the ovules inserted at the transition between the two zones, i.e. In particular, the largest and obviously closely related families of Apiales, namely Araliaceae, Myodocarpaceae and Apiaceae, are similar to each other in the structure of their gynoecia whereas the Pittosporaceae is very distinct from them. Plunkett et al., 2004 a, b Nicolas and Plunkett, 2009), some important aspects of floral evolution in the order remain enigmatic. Although the phylogeny and morphology of the Apiales have been investigated by many botanists, and significant progress has been made in this area of research in recent years (e.g.
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