The cardamom conundrum resolved: Recircumscription and placement of Elettaria in the only pantropically distributed ginger lineage

Abstract

The overarching aim of the present study is to sort out the taxonomy of a group of gingers that include the useful and worldwide economically important green cardamom, Elettaria cardamomum, and its wild relatives, to highlight potentially overlooked genetic resources. These species occur naturally in India and Sri Lanka, and our study facilitates more appropriate management priorities for the remaining forest fragments in which they occur. We used NGS Hyb‐Seq methods and sampled four species of the Alpinia I (Fax) clade, six representatives of Aframomum and Renealmia as well as two other basally flowering Sri Lankan species. This is the only pantropically distributed lineage within the entire family, and our result shows that the Alpinia I clade in fact is simply the genus Elettaria (confined to India and Sri Lanka), which is sister to the genera Aframomum (Africa) and Renealmia (Africa and Neotropics). The taxonomic implications are: (1) a recircumscription of Elettaria comprising seven species (E. cardamomum, E. ensal, E. floribunda, E. involucrata, E. rufescens as well as two new species, E. facifera and E. tulipifera described here); (2) the Sri Lankan endemic genus Cyphostigma should be retained; (3) the new monotypic genus, Srilankanthus endemic in Sri Lanka, is described with S. nemoralis, formerly Amomum nemorale, as type. A key is provided to the seven species of Elettaria and lectotypifications are made for five species (Cyphostigma pulchellum, Elettaria floribunda, E. involucrata, E. nemoralis, E. rufescens).