Notes on the Fan-Leaflet Group of Moonworts in North America with Descriptions of Two New Members

Abstract

This paper deals with the Lunaria Group of moonworts, in particular the taxa that cluster around the Mingan moonwort, Botrychium minganense Victorin. We define the Lunaria Group as those moonworts with fan-shaped leaflets that more or less resemble B. lunaria (L.) Sw. The pinnae of the trophophore (leafy portion) may be fan-shaped, wedge-shaped, and/or spoonshaped, the veins dichotomous and lacking a distinct midrib, in contrast to the Lanceolatum Group in which the pinnae are linear, lanceolate, or ovate, the veins pinnately arranged and having a midrib. Whether or not these are truly natural groups is not yet known. It is possible that the flabellate pinna structure may result from homoplasy, rather than similarity by descent from a common ancestor. For example, the American winter grapefern, Botrychium lunarioides (Michx.) Sw., belongs to a very distinct section (Sceptridium) of the genus Botrychium but its pinnae have the same structure as B. lunaria. Frere Marie Victorin's (1927) publication of his new species, B. minganense, met with prolonged disagreement. By some it was associated with B. onondagense Underw., which is now considered to be a mere deep shade form of B. lunaria. Clausen (1938) believed that B. minganense freely intergraded with B. lunaria, and Morton (1952) wrote that the two taxa were scarcely distinguishable. Fernald (1950) reduced B. minganense to the status of a barely separable form. In 1952, W. Wagner & Lord (1956) studied the plants involved, in their natural habitats, and concluded that Victorin had actually been correct, and that B. minganense differs from B. lunaria in no less than 14 characters, including the chromosomes which number n = 90 rather than n = 45. Our more recent investigations confirm that, although widespread, B. minganense is endemic in North America, but B. lunaria is not only circumboreal, but occurs also in the southern hemisphere. Except for one species, B. boreale Sim, endemism in moonworts is practically unknown in the Old World. There are, however, only a few species. In North America, on the other hand, there is a remarkably diverse assortment of moonworts, including 14 endemics already published plus two more to be described here. The members of the Lunaria Group of moonworts now known in the United States and Canada include B. lunaria, B. minganense, B. crenulatum W. Wagner (Wagner & Wagner, 1981), and B. ascendens W. Wagner (Wagner & Wagner, 1986). The distinctness of the new ones discussed below has been solidly documented in only the past three years although it had been suspected earlier. A brief key to mature plants of this group is given here in the hope of promoting general interest and efforts by field workers to discover new populations of these rare and usually local plants.