AUTHOR=Ignatov Michael S. , Spirina Ulyana N. , Kolesnikova Maria A. , Larraín Juan , Ignatova Elena A. 

TITLE=Cell Division Patterns in the Peristomial Layers of the Moss Genus Costesia: Two Hypotheses and a Third Solution

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.536862

DOI=10.3389/fpls.2020.536862

ISSN=1664-462X

ABSTRACT=<p>The Chilean endemic genus <italic>Costesia</italic> belongs to the Gigaspermaceae, one of the most basal groups of arthrodontous mosses. While none of the species in this family has a peristome, earlier stages of sporophyte development often disclose its basic structure. The study of <italic>Costesia</italic> sporophytes at the early stages of development was conducted to identify possible similarities with <italic>Diphyscium</italic>, the genus sister to Gigaspermaceae plus all other arthrodontous mosses in the moss phylogenetic tree. <italic>Diphyscium</italic> shares a strongly unequal cell division pattern with the Dicranidae. In groups more closely related to <italic>Diphyscium</italic>, as it is the case of <italic>Costesia</italic>, this pattern is not known. Our study of <italic>Costesia</italic> found only irregular presence of slightly unequal cell divisions that may then be considered as a plesiomorphic state in peristomate mosses. The most frequently present pattern revealed in <italic>Costesia</italic> is common with the Polytrichaceae, a more basal moss group with nematodontous peristomes.</p>