The Genus Caloplaca on Seashore Rocks in Eastern North America

Abstract

The species ofthe genus Caloplaca occurring on seashore rocks in eastern North America have been studied with regard to taxonomy, geographical distribution, and ecology. Five species were found to inhabit the coastal rocks. The species also occur in Europe, and three of them in Asia. Three of the species, C. microthallina (Wedd.) Zahlbr., C. scopularis (Nyl.) Lettau, and C. verru- culifera (Vainio) Zahlbr. occur exclusively on seashore rocks, while C. lithophila H. Magn. and C. fraudans (Th. Fr.) H. Olivier occur also in inland localities. One-way analysis of variance of both morphological and anatomical characters was carried out on the American and the European populations of the species, except C. fraudans. No significant differences were found in C. lithophila, but in the other three species significant differences were recorded in two or three characters. However, the differences were mostly very small, the overlaps large, and no discontinuities could be detected. Therefore no infraspecific taxa were recognized. The lichen flora occurring on seashore rocks in eastern North America has previously been studied on several occasions. In the late 19th and the early 20th century contributions to the knowledge of lit- toral lichens were made mainly with scattered col- lections by botanists such as E. Tuckerman, H. Wil- ley, W. G. Farlow, and G. K. Merrill. Degelius (1940) was one of the first lichenologists to investigate the lichens on seashore rocks in North America more thoroughly. He studied the flora of Maine and com- pared it with the European flora, and found great similarities. The work of Degelius inspired I. M. Lamb (1954) to carry out similar studies in Nova Scotia, Canada. The most extensive collections of littoral lichens in eastern North America were made by R. M. Tay- lor. His work mainly concerned the vertical distri- bution patterns, interspecific associations, and the general geographical distribution of the species col- lected, but also comprised taxonomical studies of the genus Verrucaria and a key to the 21 species included in the study (Taylor 1974). One of the latest studies in eastern North America, including littoral lichens, is that of the flora of Fundy National Park, New Brunswick, Canada, by Gowan and Bro- do (1988). They pointed out that the maritime prov- inces are still not very well known and that the need for further studies is high. This study was carried out to investigate the spe- cies of Caloplaca occurring on seashore rocks in eastern North America, and to compare the Euro- pean and the American populations of the species. No extensive studies have previously been done on this group in this region. Three of the species, oc- curring also in northern Europe, have been treated by Nordin (1972), but only for the European range of the species.