Ecology of closely related plant species: An introduction

Abstract

The papers in this volume resulted from a special symposium on the ecology of closely related species held at the 40th Congress of the International Association for Vegetation Science (IAVS) in 1997 at Ceske Budejovice (Budweis, Czech Republic). The aim of this symposium was to integrate studies in taxonomy and phytosociology, both with a strong tradition in continental Europe, into the evolutionary ecology of plants. It was expected that this could lead to new insights into the selective forces exerted by the environment, especially the plant community, on target species and into their repertoires of evolutionary/ecological responses as influenced by phylogenetic constraints. The different contributions demonstrate the large interest of ecologists in this integration of taxonomic and phytosociological approaches. The papers can be grouped into two sets: in the first, the authors put the taxonomic units at the start of their considerations and in the second, the authors put the vegetation units at the centre of their investigations. Comparative ecology is one of the successful approaches explaining differences among individual species and trying to find general patterns in the world of organism diversity. There are several approaches, represented by treatments of large data sets (e.g. GRIME et al. 1988) or small sets of similar or related species (e.g. HARPER & CHANCELLOR 1959, HARPER & CLATWORTHY 1963). The results of the latter approach were supported in recent years by considering phylogenetic constraints, trying to solve the problems caused by phylogenetic relationships, at least partly known by former authors as a problem of homology and analogy. The necessity to consider phylogenetic relationships are complicated by the fact that only a limited number of plant groups had known phylogenetic relationships based on other than morphological criteria. However, such data are necessary as independent information to avoid circular arguments. In practice, only a few phylogenetic trees exist at higher (on the family) level of relationships (e.g. CHASE et al. 1993, SOLTIs et al. 1997, KALLERSJO et al. 1998). Some of these trees have been used in different ecological/ecological-evolutionary papers (e.g. SILVERTOWN et al. 1996). A careful use is necessary because phylogenetic trees are based on a small proportion of total genetic information and because even similarities at the DNA level may be due to convergent evolution (LEE 1999).