A New Subspecies and a New Combination in Gymnocalycium sutterianum (Cactaceae, Trichocereeae) from Argentina
The new subspecies Gymnocalycium sutterianum (Schick) Hosseus subsp. arachnispinum Řepka (Cactaceae, Trichocereeae) is described from Córdoba, Argentina. It differs from the nominate subspecies mainly in the following morphological characters: a smaller plant body, shorter distances between areoles, smaller hemispherical tubercles (8–12 mm in diameter), seven to nine shorter spines (7–10 mm) per areole that are shorter and often bent over the tubercles, thinner spines in cross-section 0.25–0.4 mm in diameter, smaller flowers, and pericarp to perigon ratios from 1:2 to 2:3. The new subspecies also differs in genome size and ploidy level (G. sutterianum subsp. sutterianum 2n = 6x, G. sutterianum subsp. arachnispinum 2n = 4x). Moreover, populations of the new subspecies are found in a separate distribution area from that of the nominate subspecies. The new combination G. sutterianum subsp. dolezalii (Halda & Milt) Řepka [≡ G. poeschlii Neuhuber subsp. dolezalii Halda & Milt] is established and the subspecies name is neotypified. A taxonomic key to identify the three subspecies of G. sutterianum is included.