Two Gymnocarpium Hybrids New to the Iowa Pteridophyte Flora

Abstract

-A survey of over 100 algific talus slope sites in northeastern Iowa for individuals of the genus Gymnocarpium revealed the presence of two additional taxa in the Iowa Pteridophyte flora. Gymnocarpium xbrittonianum (Sarvela) Pryer & Haufler was located at two adjacent sites in Clayton County, where it is disjunct approximately 300 km from the nearest reported stations in northernmost Wisconsin. Gymnocarpium Xintermedium Sarvela was located at individual sites in Clayton and Dubuque Counties. The Driftless Area populations for this taxon are disjunct from the northern shore of Lake Superior. Until recently, only two taxa from the genus Gymnocarpium were reported from Iowa: G. dryopteris (L.) Newman and G. robertianum (Hoffm.) Newman (Peck, 1976, 1983, 1989). Recent taxonomic work by Pryer (1993) and Pryer and Haufler (1993) has demonstrated that at least five species and five hybrids occur in North America. During survey work from 1985-1991 on northeastern Iowa algific (cold producing) talus slopes (Frest, 1981), a number of specimens from Gymnocarpium populations were observed and collected. Examination of these materials, housed in the R.V. Drexler Herbarium (COE) at Coe College, Cedar Rapids, Iowa, revealed two additional Gymnocarpium taxa from the state. Gymnocarpium xbrittonianum (Sarvela) Pryer & Haufler is composed of sterile, robust Gymnocarpium individuals that appear to be hybrids between the boreal G. dryopteris and the Pacific Northwest G. disjunctum (Rupr.) Ching (Pryer, 1993; Pryer and Haufler, 1993). The closest published records for this taxon to Iowa exist along the southern shore of Lake Superior. Large Gymnocarpium individuals with aborted spores were located on 7 July 1990 on an algific talus slope at Bixby State Preserve in Clayton County (Sec. 23, Lodomillo Township, Nekola & Thomson s.n. [COE 8499]). These specimens were examined by Kathleen Pryer in the spring of 1991 and identified as the first collection of G. xbrittonianum from Iowa. An extensive search for additional populations was made in the summer of 1991 on over 100 algific talus slope sites throughout northeastern Iowa. Only one additional clone, found on an algific slope 0.5 km east of the original colony, was located in Clayton County (Sec. 23, Lodomillo Township, Nekola s.n.[COE 9415]). Additionally, a third clone likely exists in the same valley, 1 km east of the original colony, but could not be definitively verified due to the early date of collection, which precluded the presence of mature spores. This taxon must be considered one This content downloaded from 207.46.13.150 on Thu, 28 Jul 2016 05:28:57 UTC All use subject to http://about.jstor.org/terms AMERICAN FERN JOURNAL: VOLUME 87 NUMBER 1 (1997) of the rarest of Iowa ferns, as it is restricted to two or three small colonies along a one km section of a single stream valley. Gymnocarpium Xintermedium Sarvela is the sterile hybrid between G. dryopteris and G. jessoense (Koidz.) Koidz. ssp. parvulum Sarvela (Pryer, 1993; Pryer and Haufler, 1993). Whereas G. Xintermedium has been reported from Alaska to Northern Quebec, it is most abundant along the northern and western shores of Lake Superior. Although this taxon has been reported from Fillmore County, in southeastern Minnesota (K. Pryer, personal communication), no previously published reports of this taxon existed from Iowa. Two unusual Gymnocarpium populations with aborted spores were collected in the summer of 1990 from algific talus slope habitats in Clayton County (Sec. 26, Boardman Township, Nekola & Thomas s.n. [COE 9051]) and Dubuque County (Secs. 4 & 5, Taylor Township, Nekola s.n. [COE 8385]). These were identified by K. Pryer in the spring of 1991 as G. Xintermedium. Of these, the Dubuque County population was by far the largest, with this taxon being dominant on an open, mossy, cold northwest-facing, algific talus slope. Extensive searches in the summer of 1991 on other algific slope sites uncovered no additional populations. Subsequent examination of Gymnocarpium specimens from other major Iowa herbaria in 1995 by K. Pryer (pers. comm.) uncovered an additional historical (1896) collection of this taxon from Winneshiek County (Goddard s.n. [IA, ISC]). Although this taxon typically occurs with both parent species in its western Great Lakes populations, neither G. dryopteris nor G. jessoense ssp. parvulum was located at either of the extant G. xintermedium sites. Discovery of G. jessoense var. parvulum would be important, as it currently is not known as an extant member of the Iowa flora. Kathleen Pryer (pers. comm.) noted the existence of two herbarium specimens of G. jessoense var. parvulum collected in Iowa, portions of a July 1882 collection from Winneshiek County (Holway s.n. [GH]) and a September 1958 collection from Allamakee County (Hartley 6254 [IA]). Unfortunately, the Allamake County specimen could not be located during this study and recent searches for this taxon at the site have been unsuccessful.