Morphological and anatomical patterns in Pontederiaceae (Commelinales) and their evolutionary implications

Abstract

Pontederiaceae include six genera and approximately 35 species of aquatic plants. The family exhibits great variation in morphology that makes the characterization of species and the understanding of infrafamilial relationships difficult. Twenty species were studied from collections made at the reproductive stage, aiming to establish morphological and anatomical patterns to better understand the taxonomy and evolution of the family. In order to include all species of the family, herbarium specimens were analyzed together with information available in the literature. Four morphological patterns were established for the family: Pattern I-stems with short internodes and alternate, petiolate leaves; Pattern II-stems with long internodes and alternate, petiolate leaves; Pattern III-stems with long internodes and alternate, sessile leaves; Pattern IV-stems with long internodes and verticillate, sessile leaves. The stems have atactosteles and in the species of Pattern I they are rhizomatous. The leaf petiole, the reproductive axis, the inflorescence bract petiole and the peduncle have monosteles and are distinguished from one another by the number of rings of collateral vascular bundles, and by the presence or absence of a fistula. The morphological patterns may represent synapomorphies of infrageneric groups and are related to the life form of the species. Based on current phylogenies, Pattern I is a plesiomorphic condition, including emergent species, and Patterns III and IV are the most derived and include submersed species. This is consistent with variation in water availability in the environment having influenced the diversification of Pontederiaceae during the course of their evolution.

The aquatic species Pontederia azurea and P. crassipes (Pontederiaceae) in the Pantanal, Brazil: evidence of how plant structure can simultaneously reflect phylogeny and ecology

“…Primarily aquatic, the sympatric species P. azurea and P. crassipes exhibit distinct phenotypic responses in the Pantanal wetland. Responses such as the ability to elongate and inflate petioles are somewhat a result of their characteristic morphology, which in turn seems to be closely associated with aquatic habitats and life-forms evolved during the evolution of Pontederiaceae (Barrett & Graham 1997;Sousa et al 2016;Pellegrini et al 2018). In contrast, petiole length, leaf blade dimensions, size of lacunae, and lignification of vessel elements seem to be associatedbut not solely -with fluctuations in the water level, as previously suggested for many aquatic species occurring in the Pantanal (see citations throughout this paper).…”

“…The free-floating life-form and inflated petioles of P. crassipes are unique within Pontederiaceae (Sousa et al 2016;Pellegrini et al 2018). Since the emergent life-form has been recognized as plesiomorphic within the family (Barrett & Graham 1997) and P. crassipes is currently the only species placed in the Pontederia subg.…”

Flora do Ceará: Pontederiaceae

“…Além disto, o androceu formado por seis estames e por anteras homomorfas e o ovário com três lóculos multiovulados, gerando um fruto do tipo cápsula loculicida, podem ser considerados caracteres de importância taxonômica. Entretanto, as análises filogenéticas resgatam o gênero como um grupo polifilético, formado por quatro linhagens distintas (Graham et al 2002;Ness et al 2011;Sousa et al 2016a). É um gênero com ampla distribuição, apresentando cerca de seis espécies, todas ocorrendo no Brasil (BFG 2015; Sousa 2017).…”

Flora das cangas da Serra dos Carajás, Pará, Brasil: Pontederiaceae

“…A família apresenta uma grande variedade morfológica e de formas de crescimento, sendo encontradas espécies emergentes, flutuantes livres, flutuantes fixas e submersas (Sousa & Giulietti 2014;Sousa et al 2015). Pontederiaceae é ainda uma das poucas famílias das Angiospermas com espécies tristílicas, apresentando flores com variação no comprimento do estilete e dos filetes (Barrett 1988;Barrett & Graham 1997).…”

“…2016 reduzido a um único estame, sendo esse conjunto de caracteres único entre as Pontederiaceae (Sousa et al 2015). Desta forma, novos trabalhos incluindo dados morfológicos, anatômicos e moleculares estão sendo desenvolvidos na busca de resoluções coerentes e concretas para a relação entre os gêneros de Pontederiaceae (D.J.L.…”