Hyophila involuta (Hook.) Jaeg.
Rolled-leaf Wet-ground Moss
Gymnostomum involutum, Hyophila tortula
Basis for Listing
Hyophila involuta (rolled-leaf wet-ground moss) has a nearly continuous world distribution, without zonal affinity. It has been recorded regionally from Ontario, Iowa, and Wisconsin. It is a short-lived shuttle species that grows on wet rocks, often in streams (Janssens 2005). In Minnesota, only a single population has been found in The Blufflands of Houston County. Because only one population has been documented in Minnesota, there is too little information available at this time to detect a statewide population trend. Based on its apparent rarity and restrictive habitat requirements, Hyophila involuta was designated of special concern in 2013.
Hyophila involuta is a small plant that grows in loose or dense tufts that are dark green to red-brown or blackish in color (Zander 2007). Plants have distinctly short stems (5-10 mm [0.2-0.4 in]), giving it the appearance of a rosette of basal leaves. Leaves are tightly inrolled at the margins when dry and, as such, are linear and somewhat inconspicuous. When moist, the leaves are wide-spreading and broadly concave, 1.5-2.5 mm (0.06-0.10 in.) in length, oblong-spatulate to obovate, and often mucronate (tipped with a short sharp point; Crum and Anderson 1981). Costa (midrib) is stout, brown, and prominent on the backside of the leaf. Setae (stalks supporting the capsules) are usually solitary, elongate, and often twisted (6-7 mm [0.2-0.3 in]), turning reddish to yellow-brown with age, supporting an erect capsule (1.5-3.0 mm [0.06-0.12 in.]) that is narrowly cylindrical from an indistinct neck (Zander 2007).
Across its range, H. involuta occus on loosely consolidated sedimentary rocks, soft limestone, rocky riverbanks, streamsides, boulders in streams, wet cliffs, and bluffs in shaded woods (Crum and Anderson 1981; Zander 2007). In Ontario, it has also been found growing in abundance on the sides of locks in a canal, probably transported by water and boats travelling through the locks (Ireland and Shchepanek 1993). In Minnesota, it has been found growing on rock in an intermittent stream bed.
Biology / Life History
Plants are dioicous (male and female reproductive organs are on separate plants). Reproduction is primarily by means of numerous gemmae on branched stalks that are common on leaf axils. The name refers to the species’ in-rolled leaf margins. According to Ireland and Shchepanek (1993), the plants found growing on the walls of canal locks in Ontario were reportedly more abundant on walls exposed to a low intensity of sunlight, appearing to thrive in an environment where there is frequent alternation of wetting and drying. In its natural habitat, Hyophila grows in similar environments along creeks and streams, indicating that the plants prefer alternating hydrophytic and xerophytic conditions and perhaps even require them for survival (Ireland and Shchepanek 1993).
Conservation / Management
While further survey work is needed to clarify the species’ abundance and distribution in the state, its specific microhabitat suggests that climate change might eventually stress survival of any existing populations.
Best Time to Search
While Hyophila involuta apparently rarely fruits, it can be searched for anytime from May through September or essentially anytime the ground is not covered by snow.
Erika R. Rowe (MNDNR), 2018
(Note: all content ©MNDNR)