Revisão taxonômica das espécies brasileiras de Alternanthera Forssk (Amaranthaceae Juss.)

Abstract

Amaranthaceae is a family of about 180 genera and 2,500 species, divided in 8 subfamilies, and distributed in tropical and temperate areas of both hemispheres. It represents the most species-rich lineage within the Caryophyllales. For Brazil are recognized 158 species in 27 genera, with three endemic, and most of them included in Gomphrenoideae.This subfamily includes two major Brazilian genera,Gomphrena with 45 species and Alternanthera with 36 species. Alternanthera is a monophyletic group of about 100 species of pantropical distribution, characterized by sessile or pedunculate axillaryinflorescences, with the partial inflorescence unit reduced to a single flower. Flowers are sessile or pedicellate, protected by a bract and two bracteoles, bisexual, with (4-)5 tepals, (4-)5 stamens, with fused filaments forming a basal tube, free towards the tube end and alternating with pseudo-staminodes.The latest revision of Alternanthera for Brazil dates backto that of the Flora Brasiliensis,of more than 160 years ago, fully justifyinga new revision, the principal objective of our thesis. It isdivided into four chapters, followingan introduction. Chapter 1 includes a morphological study of the Alternanthera species in Brazil, using 107 characters, of which 99 were considered informative and have been evaluated using DELTA, resulting in a description of vegetative and floral organs of Alternanthera,with the focuson the most important of them for the group's taxonomy anda discussionof their terminology.Chapter 2 isa study of the Alternanthera brasiliana complex of five species, using the statistical exploratory analysis. Only four species in the complexwere recognized, with a proposalto synonymize Alternanthera ramosissimatoA. brasiliana.Chapter 3 is the text of a paperon the new species Alternanthera catingae, submitted for publication in Phytotaxa. Chapter 4 is a revision of the Brazilian species of Alternanthera, based on the study of 1,900 specimens deposited in 19 herbaria and using the adopted typological species concept.In addition to the traditional revisionary methodology, modernanalytic tools were used inthe evaluation of species occurring in Brazil. We recognized 35 species, with one, A.catingae, new to science, synonymizedsix species, and made one new combination. The work should be an important contributionto the study of the Brazilian Amaranthaceae, especially in terms of reaching the objective of making the Flora of Brazil go online in 2020.