Sauropus androgynus

Welzen, P. C. van, Pruesapan, K., Telford, I. R. H., Esser, H. - J. & Bruhl, J. J., 2014, Phylogenetic reconstruction prompts taxonomic changes in Sauropus, Synostemon and Breynia (Phyllanthaceae tribe Phyllantheae), Blumea 59 (2), pp. 77-94 : 88

Sauropus androgynus complex

Sauropus assimilis , and three samples of Sa. androgynus form a strongly supported clade ( Fig. 3–5 , support in Fig. 3 ). Originally, these species were placed in Sa. sect. (Eu) Sauropus ( Müller Argoviensis 1863, 1866, Hooker 1887). Later Sa. assimilis was placed into Sa. sect. Schizanthi ( Pax & Hoffmann 1922; Table 2) based on having almost free staminate sepals. Sauropus androgynus is widely cultivated from India to Australia, which may explain why it is morphologically variable. Typical are the ovate leaves with gradually tapering apices and the staminate calyx, which is generally completely connate and rather round and varies between 2.5– 20 mm diam ( Fig. 6d ). The very large calyx varies from flat (typical Sa. androgynus ) to recurved (former Sa. retroversus Wight ). The recurved form is thought to be typical for Sri Lanka, but flat and recurved calices are also commonly found in Thailand. A third form in the complex is Sa. assimilis , which typically has free staminate sepal lobes. Free staminate sepal lobes are incidentally found throughout the range of Sa. androgynus . All three forms have the Sa. androgynus type of leaf. Van Welzen (2003) placed Sa. retroversus in synonymy under Sa. androgynus . Analyses of nuclear ( Pruesapan et al. 2012) and chloroplast ( Pruesapan et al. 2008) data found former Sa. retroversus and Sa. assimilis to be sister species, and both in turn sister to typical Sa. androgynus . By contrast Kathriarachchi et al. (2006) found no support for a close relationship between former Sa. retroversus and Sa. androgynus and thus argued that former Sa. retroversus is not a synonym of Sa. androgynus . Yet morphologically, and from our molecular studies, it is very difficult to separate the three forms, as explained above, and no sharp distinction can be made between Sa. androgynus and Sa. retroversus . The two herbarium specimens available from Sri Lanka of Sa. assimilis appear to be an exceptional form of Sa. androgynus , with a deeply divided calyx, and it should be also considered as conspecific with Sa. androgynus . Based on our extensive study of herbarium material, together with morphological and molecular analysis, we here (see below) place Sa. assimilis as synonym under Sa. androgynus .

Figures

Fig. 3 Character state transformations mapped onto one of the MCC trees of the Bayesian phylogenetic analysis of combined morphological and molecular characters (for latter see Pruesapan et al. 2012). Closed circles are non-homoplasious apomorphies, open circles are parallel developments, crosses are reversals and crosses in open circles parallel reversals. State changes are indicated next to the character number. Above the branches posterior probabilities above 0.5. Absent are the characters 3, 9, 12, 13, 18, 25, 26, 33, 37, 38, 41 (see results), while characters 1 and 4 are depicted in Fig. 4, and characters 21–23, 27, 31, and 47 can be found in Fig. 5. The acronyms indicate former sections: CRY = Sa. sect. Cryptogynium, GLO = Sa. sect. Glochidioidei, HEM = Sa. sect. Hemisauropus, SAU = Sa. sect. Sauropus, SCH = Sa. sect. Schizanthi, UNP = unplaced. Clade abbreviations after Pruesapan et al. (2012; Fig. 1).

Fig. 4 The MCC tree of Fig. 3 with character state transformations of: a. leaf size (character 1 and 52, latter with many states to show variation) and b. pres- ence of a rim at the edge of the ovary (character 43). Clade A shows the species of Breynia subg. Sauropus. Clade B shows the species of Breynia subg. Breynia; comprised of clade B1 presenting the species of sect. Cryptogynium and clade B2 presenting the species of sect. Breynia.

Fig. 5 The MCC tree of Fig. 3 with character state transitions in the anther position (char. 31), connation (char. 21) and degree of fusion (char. 22) of the staminate sepals, staminate flower shape (char. 23), the presence of a disc in the staminate flowers (char. 27), and the stigma position (char. 47), ‘-’ indicates that the character is not applicable. Clade A shows the species of Breynia subg. Sauropus. Clade B shows the species of Breynia subg. Breynia; comprised of clade B1 presenting the species of sect. Cryptogynium and clade B2 presenting the species of sect. Breynia.

Fig. 6 a, b: Pistillate flowers with horizontal stigmas and absence (a) or presence (b) of a rim at the edge of the ovary; c–f: staminate flowers with horizontal anthers (c, d) and ascending anthers (e); sepals scales indistinct (c) and lobed (d, e); calyx with a dissected (c) or hardly lobed (d, e) and completely connate sepals (f); a, c: Sa. spatulifolius Beille; b: Sa. hirsutus Beille; d: Sa. androgynus (L.) Merr.; e: Sa. villosus (Blanco) Merr.; f: B. stipitata Müll.Arg. — Photo’s by: a, c, e. Kanchana Pruesapan; b. Bhanumas Chantarasuwan; d. Siriporn Zungsonthiporn.