To evaluate the evolutionary relationships among species of
Peperomia subg.
Micropiper, a phylogenetic analysis based on the DNA sequences of plastid regions
atpB-rbcL,
psbK-I,
rpL16,
rpS16,
trnG,
trnK (including
matK),
trnL-L-F, and
trnS-G was conducted using 20 species, in addition to four outgroup species. The
trnK sequences of 46 species and
trnL-L-F sequence of one species were quoted from GenBank and also included in the analysis. The results showed that
P. subg.
Micropiper includes seven major clades, which are also supported by morphological characteristics. They are recognized as sectionequivalent plant groups, namely Alatoid, Blandoid, Glabelloid, Glaucoid, Japonicoid, Lanceolatoid, and Rotundifolioid. A chromosome analysis of the subgenus yielded nine new counts: 2
n = 22 (diploid) for
P. alata,
P. bicolor,
P. diaphanoides,
P. flexicaulis,
P. hylophila,
P. polystachya and
P. prosterata, 2
n = 44(tetraploid) for
P. okinawensis and 2
n = 132 (dodecaploid) for
P. reticulata. Japonicoid, which occurs outside the Americas,
i.e. in Asia, Africa, and the Pacific islands, is tetraploid, decaploid, and dodecaploid (not diploid), while the remaining six plant groups are native to the Americas and diploid (except Glaucoid, which is tetraploid). Further,
P. diaphanoides is conspecific with
P. glabella. Peperomia boninsimensis from the Ogasawara Islands, Japan, is more closely related to Polynesian species than to other Japanese species.
Peperomia okinawensis should be regarded as a variety of
P. japonica.
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