Dendroceros Nees (Dendrocerotaceae, Anthocerotophyta): revisão sub-genérica, tolerância à dessecação e interação com Nostoc sp.

Abstract

Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts) phyla, comprise what we commonly call bryophytes. This group of plants has about 25,000 described species and corresponds to the second largest representative of terrestrial plants. Bryophytes retain ancestral characteristics that helped establish the first plants for land life, such as poikiloidy and desiccation tolerance. Hornworts are a monophyletic group, with five families, 12 genera and 200 to 250 species in the world: with terricolous, saxicolous and epiphytic habits. The gametophyte of these plants can have cyanobacterial colonies (Nostoc), generating an important symbiosis. Its sporophyte differs from other bryophyte phyla in that it grows from a basal meristem, which develops spores with exosporic germination in most of them. The genus Dendroceros has a high diversity, having about 40 species, of which 13 are present in the Neotropics, present mainly in temperate, subtemperate and tropical regions. This genus is the only one exclusively epiphytic, with large multicellular spores and endosporic germination. In the latest update of the world checklist for hornworts and liverworts, the species of Dendroceros were presented, where more than 60% of the species showed large gaps in information. This fact becomes even more worrying at the Neotropical level, as 80% of the reported species need a taxonomic review and phylogeny studies. There are few collections, doubtful determinations, and names or confusing and/or incomplete descriptions, making very clear the urgency and need for a revision of the genus Dendroceros. In this context, the main objectives of this thesis were: 1) Taxonomically and phylogenetically circumscription the genus Dendroceros (Chapter I); 2) Evaluate the effects of desiccation on gametophytes and sporophytes of Dendroceros Nees, the only genus with an epiphytic niche among the Anthocerotophyta (Chapter II); and 3) Investigate and describe the influence of Nostoc sp. in the early stages of development of Dendroceros crispus spores (Chapter III). Thus, in the first chapter presented here, we clarify the main doubts at the subgenus level, and we propose a new circumscription for Dendroceros with four subgenera: subg. Apoceros (eight species), subg. Dendroceros (fourteen species), subg. Nodulusus (five species) and subg. Cichoraceus (monotypic). In the second chapter, we describe conflicting demands between gametophytes and hornworts spores in response to desiccation. Evidencing contrasting life strategies, which are linked with the niche in the Dendroceros, Nothoceros, Phaeoceros and Anthoceros genera. Finally, in the third chapter, we present the effects of the cyanobacterium Nostoc sp. on spores and juvenile gametophytes of Dendroceros crispus and Nothoceros vincentianus. The data gathered in this work show the importance of continuing to study the hornworts, thus increasing efforts to conserve the natural areas they inhabit, such as cloud forests in Colombia and the Atlantic Forest in Brazil. At the same time, this study was relevant to fill important gaps (taxonomic, ecological, and environmental) about the knowledge of Dendroceros in the Neotropics.