Biometrics of the sporangia and spores of the Parablechnum cordatum complex (Blechnaceae, Polypodiopsida)

Aleksandra Patrjcia Wal,Sonia Molino,Antonio Murciano,Carmen Prada,José María Gabriel Y Galán

doi:10.5209/bocm.73655

Abstract

Parablechnum is the most diverse genus of Blechnaceae (ca. 65 species), with a pantropical distribution and two centers of diversity, in America and in the Austro-Pacific region. The species are dimorphic, with often erect rhizomes and rhizomatic scales, 1-pinnate fronds, with truncate blade at base, conform apex and stalked pinnae. This group presents many taxonomic problems, needing more detailed studies to resolve these conflicts of separation between species. This work deals with the American complex of P. cordatum in which the species P. cordatum, P. schiedeanum, P. chilense, P. falciforme and Blechnum varians are included. A biometric analysis of sporangia and spores, important taxonomic structures in the distinction of ferns, has been carried out. The data were subjected to a one-way analysis of variance and a discriminant analysis. In addition, the spores were observed under a scanning electron microscope to study their ornamentation. Of the characters we have studied thickness of the arcus, number of cells in the arcus, number of cells in the hypostome and major equatorial diameter of the spore have statisticalParablechnum is the most diverse genus of Blechnaceae (ca. 65 species), with a pantropical distribution and two centers of diversity, in America and in the Austro-Pacific region. The species are dimorphic, with often erect rhizomes and rhizomatic scales, 1-pinnate fronds, with truncate blade at base, conform apex and stalked pinnae. This group presents many taxonomic problems, needing more detailed studies to resolve these conflicts of separation between species. This work deals with the American complex of P. cordatum in which the species P. cordatum, P. schiedeanum, P. chilense, P. falciforme and Blechnum varians are included. A biometric analysis of sporangia and spores, important taxonomic structures in the distinction of ferns, has been carried out. The data were subjected to a one-way analysis of variance and a discriminant analysis. In addition, the spores were observed under a scanning electron microscope to study their ornamentation. Of the characters we have studied thickness of the arcus, number of cells in the arcus, number of cells in the hypostome and major equatorial diameter of the spore have statistically supported taxonomic significance and are therefore useful for species separation.

Highlights

Blechnaceae is a subcosmopolitan fern family, with about 265 species (PPG I 2016)
The differences in spore ornamentation, in terms of areolae and filaments, have been mentioned in both Parablechnum schiedeanum (Moran et al 2018) and P. falciforme (Passarelli et al 2010), coinciding our results with those presented in these publications
As for P. cordatum, its ornamentation was described by Prada et al (2008) and Melo da Silva et al (2019), who indicated that the areas between ridges present filaments or that they present discrete filaments dispersed throughout the surface, respectively

Summary

Introduction

Blechnaceae is a subcosmopolitan fern family, with about 265 species (PPG I 2016). The family consists of 25 genera (Gasper et al 2016, 2017; Molino et al 2019). Parablechnum is the most diverse, comprising approximately 65 species with a pan-tropical distribution (Fig. 1), predominantly in the southern hemisphere (Gasper et al 2017). The genus Parablechnum is one of the most complex genera of the Blechnaceae in terms of taxonomy; one of the groups of species that has received the most attention is the P. cordatum (Desv.) Gasper &. P.; Molino, S.; Murciano, A.; Prada, C.; Gabriel y Galán, J.

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