Clymenia (plant)

Cultivated locally for its sweet fruits on a handful of southwestern Pacific islands, Clymenia was originally considered an obscure citrus hybrid. Botanist Tyôzaburô Tanaka noted that Clymenia would hybridize with a few other citrus plants (notably kumquats), but otherwise was generally different from other citrus in many aspects of its appearance. In the 1960s, botanist Walter Tennyson Swingle proposed that Clymenia might belong to a genus of its own. Swingle assumed that Clymenia and citrus evolved from a single common ancestor. Alternatively, Berhow suggested in 2000 that a close relationship existed between Clymenia and kumquat and that it might be a Citrofortunella hybrid.[1]

More recent genomic analysis showed Clymenia to cluster within the genus Citrus in a clade with the Australian and New Guinean limes, which though formerly placed in genera Eremocitrus and Microcitrus are now considered members of Citrus.[2][3][4] Because excluding them would make Citrus paraphyletic, the Clymenia species may likewise belong in Citrus,[2][3] with Clymenia relegated to the status of a subgenus. Genomic analysis also showed Clymenia polyandra to be completely homozygous, proving it to be a distinct species and not a hybrid.[4]

Clymenia forms a shrub or small tree, free of spines. Leaves feature a short, narrow petiole, which sets them apart from most other citrus, especially the papedas native to the same general area. Clymenia fruits are a small hesperidium, very similar to a citrus fruit. Sweet and lemony in flavor, the tangerine-sized fruits are highly segmented, with yellow pulp, and a leathery rind, similar to a true citrus fruit. They contain a large number of polyembryonic seeds. The fruit are eaten by the Bismarck islanders, who call it a-mulis.[1]

Native to a handful of locations on Papua New Guinea and nearby islets, Clymenia is far more tropical than other citrus, and even in subtropical parts of the United States, it can only be grown in a greenhouse. Specimens thrived in greenhouses in Riverside, California, but perished when planted out in the arid climate. They are locally cultivated in indigenous villages, but have never been commercially cultivated. One local name for Clymenia polyandra is a-mulis (Namatanai).[5]

• Pictures of Clymenia in Papua New Guinea.
• Sorting Citrus Relatives
• Clymenia polyandra (Tanaka) Swingle
• Clymenia polyandra