The Distribution of Woodwardia areolata

Abstract

Phytogeographical studies in North America, as compared with those in Europe, are still in their infancy. Lack of detailed atlases and the relative paucity of extensive paleoand neoecological studies in North America hamper the botanist who wishes to investigate the factors affecting the distribution of a particular species. A few botanical studies of this sort are available (Hocker, 1956; Koevenig, 1976; Salisbury, 1926), although most are limited to local areas or to single factors. The distribution of a particular plant is determined by several interrelated factors, including: (1) climate and soils, both present and past, (2) interactions with other organisms, (3) production and dissemination of propagules, and (4) evolutionary history, including time and place of origin (Billings, 1952; Cox et al., 1976; Krebs, 1972; Pielou, 1979). In general, physical parameters of the environment, such as moisture availability or extremes of temperature, place absolute limits on the distribution of an organism. Interactions with other species (including man!), soils, dispersability, and other historical factors (e.g., hurricanes, stream piracy, and glaciation) constrain the organism within these bounds (Billings, 1952; Gorham, 1954). As many have pointed out (Cox et al., 1976; Koevenig, 1976), the study of the interaction of limiting factors is problematic because of our inability to deal quantitatively with several seemingly inextricably linked variables at once. Analysis of widespread or narrowly restricted species is often easiest because in these situations one or a small number of variables contributes differentially to the distribution. Even so, the implications of such correlations are not always as clear as they may seem. In the absence of corroborative experimental evidence, caution should always be exercised in the interpretation of distributional correlations. Woodwardia areolata (L.) Moore is ideal for this type of study because it is widespread and common throughout the southeastern and Atlantic United States and is well collected. One of the three species in subgenus Lorinseria, it is characteristic of acidic mucky, sandy, and peaty bogs throughout the southeastern United States (Wherry, 1921, 1964). The aim of this paper is to make some ecological inferences from the distribution of W. areolata and to discuss some of the problems inherent in this sort of induction.