THE COMPARATIVE AUTECOLOGY OF ENDEMIC, GLOBALLY-RARE, AND GEOGRAPHICALLY-WIDESPREAD, COMMON-PLANT SPECIES - 3 CASE-STUDIES

The autecology (species biology) of each of three federal-endangered, narrowly-endemic plant species (Echinacea tanesseensis, Ilamna corei, Solidago shortii) was compared with that of a geographically-widesprea d congener (E. angustifolia, I. rivularis, S. altissima) via research and/or literature reviews. The Echinacea and Ilamna species are very c lose relatives, and the Solidago species are in the same subsection of the genus. Particular attention was given to the Echinacea species. N o differences were found in ecological, morphological, physiological, cytological, genetic or life history characteristics per se of E. tenn esseensis and E. angustifolia that reasonably could account for differ ences in their geographical distribution. Thus, a scenario based on hi storical factors was used in conjunction with the autecology of E. ten nesseensis to explain development and maintenance of endemism in this species. Likewise, no difference in species biology was identified in the two fire-dependent, fire-adapted Iliamna species, and thus endemis m in I. corei also probably is related to both autecological and histo rical factors. In contrast to the species pairs in Echinacea and Iliam na, the widespread Solidago altissima has, a greater potential to form a persistent seed bank and is a better competitor than the narrow end emic S. shortii. However, these autecological differences per se shoul d be used with caution in any attempt to explain maintenance of narrow endemism in S. shortii. We conclude that both autecological and histo rical factors are needed to explain endemism in many plant species.