Canary Grasses (Phalaris, Poaceae): biogeography, molecular dating and the role of floret structure in dispersal

Abstract

Canary grasses (Phalaris, Poaceae) include 21 species, widely spread throughout the temperate and subtropical regions of the world with two centres of diversity: the Mediterranean Basin and western North America. The genus contains annual and perennial, endemic, cosmopolitan, wild, and invasive species with diploid, tetraploid and hexaploid cytotypes. As such, Phalaris presents an ideal platform to study diversification via historic hybridization and polyploidy events, and geographical dispersal in grasses. We present the first empirical phylogeographic study for Phalaris testing current, intuitive hypotheses on the centres of origin, historic dispersal events and diversification within a geological timeframe. Bayesian methods (beast, version 1.6.2) were used to establish divergence dates, and dispersal-vicariance analyses (rasp, version 2.1b) were implemented for ancestral node reconstructions. Our phylogeographic results indicate that the genus emerged during the Miocene epoch [20.6-8.4 Ma (million years ago)] in the Mediterranean basin followed by dispersal and vicariance events to Africa, Asia and the Americas. We propose that a diploid ancestor of P. arundinacea migrated to western North America via the Bering Strait, where further diversification emerged in the New World. It appears that polyploidy played a major role in the evolution of the genus in the Old World, while diversification in the New World followed a primarily diploid pathway. Dispersal to various parts of the Americas followed different routes. Fertile florets with hairy protruding sterile lemmas showed significant correlation with wider geographical distribution.

Generation and Characterisation of a Reference Transcriptome for Phalaris (Phalaris aquatica L.)

“…The genus Phalaris (colloquially known as canary grasses) belongs to the tribe Aveneae of the Pooideae (cool-season grass sub-family) of the grass and cereal family Poaceae [10][11][12]. P. aquatica is a tetraploid taxon with a chromosomal constitution of 2n = 4x = 28.…”

Taxonomía del género Phalaris L. (Poaceae: Pooideae: Phalaridinae) en Chile

“…Ambos caracteres son, sin embargo, muy variables. Estudios moleculares y biogeográficos recientes separan ambas especies (Voshell et al 2011, Voshell & Hilu 2014 (Parodi 1939, 1943, Marticorena & Quezada 1985.…”

“…Estos últimos autores mencionan para Chile el ejemplar Garaventa 2837, recolectado en la Región de Valparaíso, Quillota, X-1932 (CONC). Esta especie es extremadamente afín a P. amethystina desde un punto de vista morfológico, pero genéticamente existen diferencias entre ambas, por lo que no podemos descartar su presencia en el país (ver Voshell et al, 2011, Voshell & Hilu 2014 Hierbas perennes, de hasta 90 cm de alto, con engrosamientos bulbosos en la base del tallo. Entrenudos de hasta 14 cm de largo, estriados, glabros.…”

“…Phalaris comprende 21 especies originarias, principalmente, de zonas templadas del hemisferio norte, tanto de la región mediterránea como del sudoeste de los Estados Unidos (Baldini 1995, Tucker 1996, Voshell & Hilu 2014. En Chile el género Phalaris se encuentra distribuido a lo largo de todo el país, desde Arica a Magallanes (18°30'-53°12'S), representado por 9 especies.…”

Ecological niche differentiation of polyploidization is not supported by environmental differences among species in a cosmopolitan grass genus

“…This genus includes 19 species in four different lineages, three of which contain polyploid species (Fig. 1A; Appendix S1, see Supplemental Data with online version of this article), and whose distributions have been studied (Voshell et al, 2011; Voshell and Hilu, 2014), making them an ideal group to investigate these hypotheses. Specifically, we hypothesize that within the genus Phalaris (1) polyploids should inhabit more extreme environments than their diploid congenors; (2) polyploids should have wider environmental niche breadths; (3a) polyploids should occupy distinct environmental niches from their diploid congenors, and (3b) polyploids should have significantly less niche overlap with their diploid congenors than their diploid congenors have with one another.…”