Phanera

Clark, Ruth P., Mackinder, Barbara A. & Banks, Hannah, 2017, Cheniella gen. nov. (Leguminosae: Cercidoideae) from southern China, Indochina and Malesia, European Journal of Taxonomy 360, pp. 1-37 : 2-4

Phanera circumscription and relationships

Until recently, Phanera was considered to comprise 120–130 lianescent species from southeast Asia and South America ( Lewis & Forest 2005). However, following the segregation of the neotropical species as the genus Schnella ( Trethowan et al. 2015) , Phanera was effectively recircumscribed as a group of ca 90 species, restricted to southeast Asia. This genus, which is most diverse in Malesia, remains the largest of the segregate genera reinstated from Bauhinia s. lat. ( Mackinder & Clark 2014). Nevertheless, Phanera is still a somewhat heterogeneous taxon. In particular, as several authors have already noted, the generic boundary of Phanera with regard to Lasiobema warrants more detailed research ( Hao et al. 2003; Lewis & Forest 2005; Mackinder & Clark 2014; Trethowan et al. 2015). Sinou et al. (2009) indicated, albeit with weak support, that based on a phylogenetic analysis of nucleotide sequence data from the cpDNA trn L-F region, Asian Phanera are closely related to Lasiobema ; although sampling in that study was very limited. Both the close relationship between Phanera and Lasiobema , as well as the wider infrageneric phylogenetic framework of Cercidoideae (the then Cercideae ) resolved by Sinou et al. (2009), were congruent with the findings of Hao et al. (2003) in a phylogenetic study of the Cercidoideae (as the Cercideae ) based on nucleotide data from the Internal Transcribed Spacer (ITS) region. The phylogenetic structure of the main lineages as determined by those two studies is compared ( Fig. 1 ). In Hao et al. (2003), the Schnella lineage was represented by an accession of Bauhinia glabra Jacq. now recognised as Schnella glabra (Jacq.) Dugand. In Sinou et al. (2009) , several accessions of Schnella were sampled and placed together on a lineage labelled as American Phanera in Fig. 1 of that publication.

The study of Hao et al. (2003), designed to investigate the close relationship between SE Asian Phanera and Lasiobema , recovered a strongly supported clade containing 31 accessions, representing 27 species, of which 23 were species of Phanera and four were species of Lasiobema . Neither genus was resolved as individually monophyletic. A plausible evolutionary interpretation of these findings is that neither Phanera nor Lasiobema are natural groups as currently delimited and that, given the morphological diversity that still exists within both genera, a further division of both genera is likely to be necessary if we are to achieve a classification that reflects monophyly. Indeed, Wunderlin et al. (1987) proposed that the Asian species of Phanera (treated by him in that publication under Bauhinia subg. Phanera ) should be further divided among seven sections, and that the species of Lasiobema be placed in three further sections. Larsen (1975) demonstrated two different pollen types in Lasiobema which supported the hypothesis of de Wit (1956) that Lasiobema may be better recognized as two genera based on floral morphology.

Nonetheless, within Phanera s. lat., the species of Phanera sect . Corymbosae de Wit do form a morphologically homogeneous group that is readily identifiable as distinct from all other Phanera diversity. Five species of Phanera sect . Corymbosae were sampled by Hao et al. (2003) and were resolved as a strongly supported (100% bootstrap) monophyletic group and placed as sister to a clade containing all other accessions of Phanera and Lasiobema species. Here we present the case for the recognition of Phanera sect . Corymbosae as a genus in its own right.

Figures

Fig. 1. Comparative topologies of two separate phylogenetic analyses of tribe Cercideae Bronn. A. Topology of the parsimony strict consensus tree based on the nrDNA Internal Transcribed Spacer region (Hao et al. 2003). B. Bayesian majority rule tree topology derived from an analysis of data from the cpDNA trnL-F region (Sinou et al. 2009). Note that the reinstatement of the genus Schnella (Wunderlin 2010) post-dates both phylogenetic studies.