Introduction

Synima Radlk. is a small genus of Sapindaceae with currently three species recognized (Forster, 2006). All the species occur in north-east Queensland in Australia with S. cordieri (F. Muell.) Radlk. extending to Papua New Guinea and Indonesia (Moluccas and Western New Guinea) (Leenhouts & Adema, 1994). Synima is morphologically closely related to Sarcotoechia Radlk. and Toechmia Radlk. based on their fruits with fleshy valves, hairy inside walls, and seeds usually bearing a small sarcotesta (Reynolds, 1985a: 176; see Adema et al., 1994 for a discussion on the use of sarcotesta instead of aril).

Buerki et al. (2012) published a phylogenetic framework aiming at testing generic monophyly in the Cupania group (corresponding mostly to the tribe Cupanieae Radlk.; Buerki et al., unpubl. data) by focusing on taxa in the southern Pacific islands. This study demonstrated that Synima belonged to clade B together with Sarcotoechia, and Toechmia (Buerki et al., 2012: 115, fig. 2B). Synima was inferred sister to the new genus Neoarytera Callm. et al. endemic to New Caledonia and Vanuatu (Buerki et al., 2020), whereas Toechmia was shown to be sister to the SE Asian and Australian genus Mischocarpus Blume. Finally, Sarcotoechia was inferred to be paraphyletic with S. villosa S.T. Reynolds sister to the New Caledonian genus Storthocalyx Radlk. and S. serrata S.T. Reynolds sister to Synima. Although Sarcotoechia and Synima are morphologically closely related, they can be discriminated by their petal morphology. Synima has crested scales on petals (vs. no petal crests in Sarcotoechia), pericarp that dries thin and wrinkled (vs. not wrinkled) and the seed with a fleshy, yellow-orange sarcotesta that is either small and basal or ± covering the seed (vs. sarcotesta rudimentary or absent) (Reynolds, 1985a, 1985b; Forster, 2006).

Reynolds (1985a: 184) has previously warranted some caution related to the generic placement of Sarcotoechia serrata and an allied species by stating that “Sarcotoechia serrata and S. heterophylla differ from all other species of Sarcotoechia in having serrate or serrulate leaflets, crispate indumentum, very small rudimentary aril [sarcotesta] and slightly larger seed. The testa also is dull compared to the shiny ones of other species and the fruit valves are not fleshy. Until more collections become available both these species are tentatively included under Sarcotoechia because the flowers, especially petals, are those of the genus. The fruits and seeds are unlike any other known Sapindaceae in Australia”.

Based on Radlkofer (1931–1934: 1255, translated from Latin by R. Gereau), Synima is morphologically characterized by “a testa of the seed [that is] drupaceous [and] covered, except for the dorsal groove, with a fleshy layer of tissue almost adnate to the aril”. With the description of two further species in the genus, we know that the sarcotesta is quite variable in Synima. Synima cordieri (F. Muell.) Radlk and S. reynoldsiae have seeds +/- entirely covered by the sarcotesta, whereas in S. macrophylla S.T. Reynolds this structure is small and only at the base of the seed (Forster, 2006). Previous phylogenetic analyses provided strong evidence supporting convergent evolution of fruit morphology in Sapindaceae as shown by the polyphyly of tribes and genera, which were mostly established based on fruit characters (Buerki et al., 2009). This is especially the case in the Cupania group where genera previously assigned to Cupanieae and Schleichereae based on contrasting fruit morphologies (mostly dehiscent fruits with ceraceous, coloured sarcotesta in Cupanieae vs. indehiscent fruit with fleshy, translucent sarcotesta in Schleichereae) were retrieved in the same clade (Buerki et al., 2009, 2011). Phylogenetic analyses of Malagasy taxa inferred species of Neotina Capuron previously classified as Cupanieae nested within species of Tinopsis Radlk. previously classified as Schleichereae (Buerki et al., 2011). A more in-depth morphological analysis recovered distinct floral and vegetative characters supporting the phylogeny (Buerki et al., 2011). What these examples provide is evidence that fruit morphology in Sapindaceae could be deceptive and that emphasis should be shifted towards flower morphology accompanied by key vegetative characters.

While describing both Sacrotoechia heterophylla and S. serrata in Sarcotoechia, Reynolds (1985a: 182, fig. 5C) described both species with petals having “scales densely crispate hairy”, which contradicts her statement that the “petals are those of the genus [Sarcotoechia]” for both species (Reynolds, 1985a: 184). This flowering character is absent in Sarcotoechia and considered as a synapomorphy for Synima. Forster (2006) had the same dilemma in describing S. reynoldsiae, a species long known as Sacrotoechia sp., which he formally described in Synima based notably on the presence of crested scales on petals.

Transfer of Sacrotoechia heterophylla and S. serrata into the genus Synima satisfies monophyly of Sarcotoechia while also maintaining coherent generic morphologies. The new combinations Synima heterophylla (S.T. Reynolds) Callm. & Buerki and S. serrata (S.T. Reynolds) Callm. & Buerki are proposed.

Key to the genus Synima

Adapted from Reynolds (1985b) and Forster (2006).

Fig. 1.

Synima heterophylla (S.T. Reynolds) Callm. & Buerki: A. Inflorescence; B. Branch with juvenile and older leaves. Synima serrata (S.T. Reynolds) Callm. & Buerki: C. Inflorescence; D. Mature fruits; E. Branch with juvenile and older leaves. [A–B: cultivated tree in Airlie Beach from seeds originating from Eungella (West of Mackay, Queensland); C–E: cultivated tree in Atherthon from seeds originating from Gadgarra (Atherthon Tableland, Queensland)] [Photos: A–B: S. and A. Pearson; C–E: G. Sankowsky]

Taxonomy