Rediscovery of the originally designated “type specimens” of Isoetes sahyadrii (Isoetaceae—Lycopodiopsida) and its nomenclatural implications

Isoetes sahyadrii was described from a T.S. Mahabale specimen at the same site in southern India from which I. dixitii and I. panchganiensis were subsequently typified. Mahabale indicated that his “type specimens” were deposited in the Gujarat College, Ahmadabad herbarium. The later disappearance of that type material and destruction of the type locality, however, combined with an ambiguous protologue to render I. sahyadrii an unresolved taxon in subsequent Isoetes enumerations. The recent rediscovery of Mahabale’s designated type material at Gujarat College, Ahmadabad has permitted reconsideration of I. sahyadrii in the context of subsequent taxonomic decisions. This study confirms earlier suggestions that I. sahyadrii was erroneously based on a mixture of I. dixitii and I. panchganiensis plants. We conclude that the name I. sahyadrii should have been recognized as having a type representing two different species and, under Art. 9.14, most appropriately to have employed the name for I. dixitii. Intervening lectotypification efforts conducted without the benefit of Mahabale’s designated type specimen, however, resulted first in epitypification of I. sahyadrii with the type of I. panchananii, then with a conserved type, that of I. panchganiensis. Both latter species exhibit morphological characteristics contrary to the predominant elements evident in Mahabale’s recently rediscovered specimen and his published protologue. The successful 2022 proposal to conserve that nomenclature, however, makes further nomenclatural clarification very difficult. Accordingly, we accept the current application of the name to the species previously known as I. panchganiensis.