The genus Microbryum (Pottiaceae, Bryophyta) in Argentina

Abstract The genus Microbryum is recorded for the first time in Argentina, with a single species Microbryum davallianum. The species differs from others in the genus mainly by stegocarpous capsules, long setae and spore ornamentation. A description, photographs and illustration of the species are provided.


Introduction
Microbryum Schimp. is a genus of the family Pottiaceae that includes 13 species (Crosby et al. 2000;Zander 2007) of annual mosses.It is characterized by small size, costa in cross section rounded to semicircular with a single band of stereids, capsule cleistocarpous or stegocarpous, and peristome (when present) generally rudimentary.The species of the genus inhabit temperate and boreal regions of the world, with preference for dry environments (Chamberlain 1978;Zander 1993;Guerra et al. 2006).
As part of a project that evaluates the diversity of bryophytes in Argentina Northeast (Alvarez & Villalba 2021;Alvarez et al. 2023a; b) some collected specimens were identified as Microbryum davallianum (Sm.) R. H. Zander, a species not recorded for the moss flora of Argentina.Although the species is well known to areas with an old history of bryological expeditions (e.g., Europe, Africa, Asia, North America and Australia), it has only been reported from two collections in South America (Brazil and Chile, Cano & Gallego 2008).The species grows on limestone, sandy, saline or humic soils, often uncovered.
Micrbryum davallianum is here described and illustrated, and some characteristics of its geographical distribution in Argentina are mentioned.

Materials and methods
The specimens were studied morphologically with the conventional techniques proposed by Zander (1993) for Pottiaceae, using stereoscopic magnifying glass Arcano ST30-2L and optical microscope Arcano XSZ107.The identification was made through the keys of Guerra et al. (2006) and Da Costa (2016).The material studied with scanning electron microscopy (JEOL 5800 LV operating at 20 KV) was fixed in FAA, critical-point dried, and then mounted on aluminum discs on double-sided tape, to later be coated with gold-palladium.
Pilkington ( 2022) mentions that M. davallianum is an early colonist of disturbed soils and can be found in a wide variety of habitats, this affirmation is consistent with the environment where our samples were found.The preference of rural habitats is observed in some species of others genus, such as Chenia, Anaschisma and Physcomitrium (Flores & Suárez 2017;Colotti & Suárez 2022;Alvarez et al. 2023a).Microbryum starckeanum, M. curvicollum (Hedw.)R.H. Zander and M. rectum (With.)R.H. Zander, are also found in disturbed habitats (Blockeel et al. 2014;Pilkington 2022).