Systematics of Mielichhoferia (Bryaceae: Musci). II. Morphological Variation among Disjunct Populations of M. elongata and M. mielichhoferiana

Abstract

Seventeen gametophytic and five sporophytic traits were measured in North American and European (plus one Asian) populations of Mielichhoferia elongata and M. mielichhoferiana in order to assess morphological differentiation between the species and between disjunct conspecific populations. Gametophyte data were obtained from 65 populations and sporophyte data from 27 populations. The two species could be distinguished by leaf length, costa width, and cell size (length and width of basal and upper cells). Weak correlations between variation in different gametophytic traits resulted in poor resolution of the species by multivariate statistical techniques. North American plants of M. elongata had longer setae, capsules, and exothecial cells than their European coun- terparts. A matrix comparison of distance estimates between populations obtained from sporophytic vs. gametophytic traits showed that characters from the two generations do not provide congruent estimates of phenetic similarity. The genus Mielichhoferia is most diverse in the Andes Mountains of northern South America but is represented by four rare species in temperate to arctic latitudes of North America, Europe, and Asia. The most restricted species, M. tehamensis Show- ers, is only known from a few sites in two adjacent counties of California near Mt. Lassen, the south- ernmost volcanic peak of the Cascade Range. The remaining three species are more widespread but have highly disjunctive ranges and are nowhere common. Mielichhoferia macrocarpa (Hook. ex Drumm.) Bruch & Schimp. ex Jaeg. & Sauerb. is perhaps the rarest of the group, known only from a few widely scattered sites from Greenland to Alaska, and south to Colorado and Utah. It has also been reported from northern Russia and the Sayan