The Struthiopteris spicant (Blechnaceae, Polypodiopsida) complex in Western Europe, with proposals for taxonomic and nomenclatural changes

Abstract

Struthiopteris spicant is a medium-sized, dimorphic fern that occurs mainly in Western Europe and Western North America. The species is quite variable, with several forms differing in frond sizes and degree of dimorphism. In addition to the typical plant, in Europe two other varieties are recognized: the Iberian S. s. var. homophyllum includes plants up to 20 cm, monomorphic or subdimorphic, with fragmented cenosori; the Icelandic S. s. var. fallax comprises very small plants up to 5 cm, monomorphic, with isolated sori. Outstanding questions remain about hybridization among the different forms, their taxonomic status, and the relations between different populations. The present work aims to study additional morphological and anatomical features of the S. spicant complex in Western Europe using a statistical approach, to resolve the taxonomic position of the different forms. We observed traits ranging from the rhizome scales to the spores and used one-way ANOVA to test for significant differences between all varieties and PCA to determine whether plants assigned to different varieties can be classified statistically into distinct groups. We detected significant differences in several of the analysed traits among the varieties in the complex. Qualitative differences in pinna anatomy and epidermal cells also help segregation of the varieties considered. Our results allowed us to propose a new specific status for the Icelandic endemic var. fallax and a new endemic Spanish variety, S. s. var. pradae.

Struthiopteris spicant (L.) Weiss (anteriormente conocido como Blechnum spicant) es un helecho que se distribuye en Europa, Macaronesia y Noroeste de América. Esta especie tiene gran variabilidad fenotípica, lo que ha hecho que se hayan descrito algunas variedades entre las que se encuentran S. spicant var. homophyllum, endemismo ibérico, y S. spicant var. fallax, endemismo islandés. En este trabajo hemos realizado un estudio morfológico y anatómico de este complejo en el oeste de Europa usando una aproximación estadística para resolver la posición taxonómica de las diferentes formas. Esto nos ha permitido redefinir el estatus de la variedad islandesa, pasando a considerarla una especie, S. fallax S. Molino, Gabriel y Galán & Wasowicz, y la descripción de una nueva variedad endémica para la Península Ibérica, S. spicant var. Pradae S. Molino & Gabriel y Galán.