Breynia quadrangularis

Welzen, P. C. van, 2017, Reduction of Breynia subgenus Hemisauropus to B. section Cryptogynium and discussion of the B. quadrangularis complex (Phyllanthaceae), Blumea 62 (2), pp. 90-91 : 91

BREYNIA QUADRANGULARIS COMPLEX

It is obvious that Chakrabarty and colleagues prefer to maintain entities in the Breynia quadrangularis complex (sect. Cryptogynium ) as distinct species ( Chakrabarty & Gangopadhyay 1996, under Sauropus ; Chakrabarty & Balakrishnan 2015), while I ( Van Welzen 2003, under Sauropus ; Van Welzen et al. 2014) regard them as one single, variable species. These species were also partly used as infraspecific entities ( var. compressus , var. puberulus ; see Van Welzen 2003). Time will tell who is cor- rect. I only would like to add three remarks to the discussion. The identification table in Chakrabarty & Balakrishnan (2015) nicely shows that the variability is more or less continuous and the differences do not always seem to be very distinct, especially not between their B. compressa (Müll.Arg.) Chakrab. & N.P.Balakr. and B. concinna (Collett & Hemsl.) Chakrab. & N.P.Balakr. Particularly sepal shapes are difficult as a character, because sepals can become, by exception, free and narrow. This is discussed in Van Welzen et al. (2014: 88), where an ex- ample for B. androgyna (L.) Chakrab. & N.P.Balakr. is provided. What is not obvious from the discussion by Chakrabarty & Balakrishnan (2015), is whether or not the whole distribution and variability of the species complex was covered, as they focus on India. It is unlikely that they have seen material from the species’ full range, because they do not refer to it and they do not acknowledge loans from other herbaria. Quite a number of specimens are known from outside India (see Van Welzen 2003, map 15 under Sauropus quadrangularis ). If the complete variability is not covered then the status of the taxa recognised by Chakrabarty & Balakrishnan (2015) is uncertain as intermediates specimens occur outside and even inside India ( Van Welzen 2003: 367, note 4).

Chakrabarty & Balakrishnan (2015) discuss only differences in morphology. A synthetic approach, also taking into account similarities, may be more clarifying.All other species in section Cryptogynium and subgenus Sauropus have pistillate flowers with horizontal, partly split stigmas resembling a crescent moon. The pistillate flowers in the quadrangularis group have erect, non-crescent moon-like stigmas. This obvious apomorphy, together with transitions between forms, is especially for me important to regard all forms as one, though variable, species. Describing variability is difficult. Two extremes are presented here: splitting into various species ( Chakrabarty & Balakrishnan 2015) or uniting all forms into one ( Van Welzen et al. 2014) with a description of the variability via notes ( Van Welzen 2003). The best way forward will be to use molecular data in a phylogeographic approach to see if the complex contains a single or multiple species. Until such studies have been performed, disagreements like these are likely to persist.