On the systematic position of Discelium (Bryophyta)

Abstract

Results of molecular phylogenetic analysis support the position of the genus Discelium in the group of diplolepideous opposite mosses, Funariidae; however, its affinity is stronger with Encalyptales than with Funariales, where it is currently placed. A number of neglected morphological characters also indicate that Discelium is related to Funariales no closer than to Encalyptales, and thus new order Disceliales is proposed. Within the Encalyptaceae a case of strong sporophyte reduction is revealed. Bryobartramia appeared to be nested in Encalypta sect. Rhabdotheca, thus this genus is synonymized with Encalypta. РезюмеМолекулярно-филогенетический анализ подтвердил положение рода Discelium в группе диплолепидных мхов с перистомом с супротивным расположением его элементов, или подклассе Funariidae, однако указал на родство с порядком Encalyptales, а не с Funariales, в который его обычно относили. Ряд редко учитываемых морфологических признаков также свидетельствует в пользу лишь отдаленного родства с Funariaceae. Предложено выделение Discelium в отдельный порядок Disceliales. В Encalyptaceae выявлен случай сильной редукции спорофита. Выявлено положение Bryobartramia в пределах рода Encalypta, в котором он имеет близкое родство с терминальными группами видов с гетерополярными спорами. Таким образом, Bryobartramia отнесена в синонимы к роду Encalypta.

Peristome development pattern in Encalypta poses a problem: what is the primary peristomial layer in mosses?

“…Although the molecular phylogenetic studies never adressed Encalypta specifically, a rather broad selection of its species was represented in a number of broaded phylogenies (Tsubota et al, 2004;Ignatov et al, 2016), which confirms the general system of the genus worked out already by Philibert (1889), Brotherus (1924), and Horton (1982Horton ( , 1983. Four species of Encalypta were selected for this study in order to include both basal and teminal representatives of the genus: E. procera, one of the basalmost species in the molecular phylogenetic trees (Tsubota et al, 2004); E. longicollis, another species from the basal grade, with the "secondary nematodontous" peristome formed by 4-5 cell layers; E. rhaptocarpa, a representative of the terminal clade, with a well developed endostome and exostome only a little shorter and adhaerent to endostome; and E. vulgaris, a species closely related to the previous one, but eperistomate.…”

“…The close phylogenetic relationship of Encalypta and Funaria is well proved (Cox et al, 2010;Ignatov et al, 2016), while the position of Timmia remains unstable (Budke et al, 2007). Nevertheless, the developmental pattern of Timmia is more similar to Encalypta, as the most conspicuous layer in Timmia is IPL and the divisions in PPL regularly occur (Fig.…”

An attempt to create air sacs in spores? On the unusual spore structure in moss Encalypta longicollis

“…Large spores in mosses usually occur in obligatory epiphytic lineages (Hedenäs, 2012) and in epigeios species of ephemeral life strategy (Furness & Hall, 1981) or growing in xeric environments. In the molecular phylogenetic tree of Encalyptaceae (Ignatov et al, 2016) the basal position is kept by Bryobrittonia (with spores 7 μm in diameter) and E. streptocarpa (with spores 9-15 μm), while in most species of Encalypta spores are 25-40 μm, and in E. brevipes up to 50 μm. The outstandingly large spores of E. longicollis, 55-85(-95) μm, are difficult to link to above mentioned factors: this species is terrestrial and it grows in non-ephemeral habitats.…”

A New Combination in Encalypta (Encalyptaceae, Bryophyta)

“…In a study by Ignatov et al (2016) on the phylogenetic relationships of the genus Discelium Brid., the order Disceliales was described and shown to be sister to the Encalyptales. Furthermore, an accession of the morphologically reduced genus Bryobartramia Sainsbury was included and discovered to be nested within the maximally supported clade corresponding to the genus Encalypta Hedw.…”