New Names in North American Myosurus (Ranunculaceae)

Abstract

The name Myosurus aristatus Bentham is illegitimate, and the North American material often treated as M. aristatus is conspecific with M. apetalus Gay of Chile. The name Myosurus apetalus var. borealis Whittemore is described for the North American taxon previously treated as M. aristatus subsp. aristatus, and the new combination M. apetalus var. montanus (G. R. Campbell) Whittemore is made for the taxon previously treated as M. aristatus subsp. montanus (G. R. Campbell) D. E. Stone. The genus Myosurus L. (Ranunculaceae) consists of ca. 15 species found in temperate regions of both hemispheres (Mabberley, 1993). The genus is often considered taxonomically difficult, since the plants are predominantly self-fertilizing and interspecific hybridization is not uncommon (Stone, 1959). However, the North American species are relatively well understood, due largely to the work of Stone (1957, 1959, 1960). One of the North American species has commonly been known under the name Myosurus aristatus Bentham (Campbell, 1952; Davis, 1952; Dorn, 1984, 1992; Hitchcock & Cronquist, 1964; Kearney & Peebles, 1964; Munz & Keck, 1959). However, this name is illegitimate, having been published originally as an avowed substitute for the legitimate name M. apetalus Gay (type from Chile). The North and South American plants have been considered conspecific by Lourteig (1951), Raven (1963), Weber & Wittmann (1992), and Wilken (1993). Stone (1957, 1960) recognized two subspecies, M. aristatus subsp. aristatus and M. aristatus subsp. montanus (G. R. Campbell) D. E. Stone, differing in characters of the sepals and fruiting heads. However, names for these taxa in M. apetalus have never been published. Campbell (1952) considered M. apetalus to be a purely South American species and listed five supposed differences between it and M. aristatus of North America: achenes more than 50 per head in M. apetalus, fewer than 50 in M. aristatus; achene beaks 0.5 mm long in M. apetalus, 1-1.5 mm in M. aristatus; scapes only slightly exceed leaves in M. apetalus, 2-3 times longer in M. aristatus; sepals 3-5-nerved in M. apetalus, 1-nerved in M. aristatus; sepals retained on fruiting spikes in M. apetalus, shed after anthesis in M. aristatus. However, Campbell had little material from South America, and apparently the revision of the South American species by Lourteig (1951) was not available at the time of Campbell's study. The plants are more variable than Campbell indicated. The number of achenes per head varies from 15 to 100 in South American material; sepals in the South American plant may be either retained on the fruiting spikes or shed after anthesis; the achene beaks vary from 0.2 to 0.9 mm long, 0.3-0.9 times as long as the achene body, in the South American plant, while they are usually longer (0.6-1.4 mm long, 0.5-1.0 tim s as long as the achene body) in North American material; the scapes at most slightly exceed the l aves in South American specimens, while they are often, but not always, longer in North America; the sepals are 3-5-nerved in the South American plant, similar to sepals of the North American M. aristatus subsp. montanus but unlike the strongly 1-nerved sepals of M. aristatus subsp. aristatus sensu Stone. Since none of the differences between North and S uth American material are absolute, but all overlap, I agree with Lourteig (1951), Raven (1963), Weber & Wittmann (1992), and Wilken (1993) that they are best considered conspecific. However, since several characters show different (though overlapping) ranges of variation on the two continents, separation of the species into varieties seems appropriate. These taxa have been fully described and illustrated by Lourteig (1951), Campbell (1952), and Stone (1957), and a full treatment of the genus in North America north of Mexico will be published (Whittemore, in press). However, the necessary nomenclature must first be validated. Myosurus apetalus Gay, Fl. Chil. 1: 31. 1845. Myosurus aristatus Bentham ex Hooker f. London J. Bot. 6: 458. 1847, illegitimate, earlier name included. TYPE: Chile. Prov. de Coquimbo, damp places in the Cordilleras de las Patos, elev. 11,200 ft., C. Gay (no longer extant?). NOVON 4: 77-79. 1994. This content downloaded from 157.55.39.105 on Fri, 13 Jan 2017 18:14:20 UTC All use subject to http://about.jstor.org/terms