PHYLLANTHACEAE

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MOERORIS and NELLICA : Recognition of segregate genera in Phyllanthus s.l. for the Flora of the Southeastern United States, with three new combinations needed

Primary authors:Geoffrey A.Levin and Alan S.Weakley

It has been recognized for almost two decades that Phyllanthus L., as generally circumscribed, is paraphyletic because Breynia J.R. Forst. & G. Forst. (including Sauropus Blume ), Glochidion J.R. Forst. & G. Forst. , and Synostemon F. Muell. were derived from within it ( Wurdack et al. 2004; Kathriarachchi et al. 2005; Hoffmann et al. 2006; Kathriarachchi et al. 2006; Falcón et al. 2020). However, it was not until recently that a phylogeny with sufficient taxon sampling and support to allow resolution not only of relationships among the genera, but also within the very large genera Glochidion and Phyllanthus , became available ( Bouman et al. 2021). Although one could argue for recognizing Phyllanthus as comprising all four genera ( Hoffmann et al. 2006; Kathriarachchi et al. 2006), doing so would result in a huge (1200 species) and morphologically heterogeneous genus ( van Welzen et al. 2014); it would also require significant redefinition of infrageneric taxa within Phyllanthus because very few previously recognized subgenera and sections are monophyletic ( Kathriarachchi et al. 2006; Pruesapan et al. 2008, 2012; Bouman et al. 2018; Falcón et al. 2020). An alternative approach is to recognize multiple monophyletic and morphologically diagnosable genera. This has been done by Bouman et al. (2022), who recognized 13 genera in this clade, including 10 from within former Phyllanthus . That approach is accepted here, resulting in three genera being represented by native (and sometimes naturalized) species in the southeastern United States ( Moeroris Raf. , Nellica Raf. , and Phyllanthus s.s.) and four others only by naturalized species ( Breynia , Cicca L., Emblica L., and Glochidion ). It is noted here that for his new genus Nellica, Rafinesque merely mentioned “(n. ind)” and the locality of its type species as “maderaspatana” (aka Chennai, Tamil Nadu, India). Nellica is a Tamil name for gooseberry fruit. Regarding Moeroris, Rafinesque did not provide an etymology. In Latin, moeror (in nominative) means “lamentation,” and moeroris is its genitive form.

Although Bouman et al. (2022) made many new combinations needed for their new classification, they did not make any combinations below the species rank. In order to allow taxonomy to reflect morphological variation within Phyllanthus s.l. species found in the southeastern United States, some new infraspecific combinations are needed. Preparing these new combinations also prompted us to review previous treatments of Phyllanthus abnormis , resulting in a proposed new infraspecific taxon within it.

When recognizing infraspecific taxa, one must decide on rank, i.e., subspecies vs. variety. A common approach is to follow tradition within the specific taxonomic group. However, in Phyllanthus , both ranks have been used. Unfortunately, other than the rule that variety is a lower rank than subspecies ( Turland et al. 2018), there are no accepted definitions of these ranks. Here, we adopt the philosophy that taxa that are show minor or inconsistent morphological differences but are geographically disjunct are recognized as subspecies, whereas those that intergrade morphologically and geographically are treated as varieties. Our choice of rank is also influenced by the degree of morphological difference, with subspecies being more different from each other than are varieties. Clearly, applying these general, community guidelines is often subjective and different rank choices are defensible.