Biogeographical Differences in a Common Soil Ciliate, Gonostomum affine (Stein), as Revealed by Morphological and RAPD-Fingerprint Analysis
Wilhelm FOISSNER (1), Thorsten STOECK (2), Helmut SCHMIDT (2) and Helmut BERGER (3)
(1) Universität Salzburg, Institut für Zoologie, Salzburg, Austria; (2) Universität Kaiserslautern, Abteilung Ökologie, Kaiserslautern, Germany; (3) Technisches Büro für Ökologie, Salzburg, Austria
Summary. Gonostomum affine is a common, hypotrichous soil ciliate showing a wide variety of more or less distinct morphologies which, depending on the view, can be considered as taxonomic entities or variations of a single morphotype. Thus, we chose it as a model to investigate some main questions in ciliate alpha-taxonomy and biodiversity, viz., (i) the power of morphological methods and RAPD-fingerprints to separate two distinct morphospecies of Gonostomum; (ii) whether morphology and RAPD agree in separating the most dissimilar morphotypes; and (iii) whether G. affine has a biogeographical population structure. Accordingly, we investigated one G. strenuum population from Australia and compared it with six G. affine populations from Europe, Africa, and South America. Data were analysed with classical similarity trees and two new methods combining morphological features and RAPD-fingerprints in single similarity trees. The main results of this study were: (i) Morphology could separate the two morphospecies very clearly, while RAPD could not, irrespective of the indices and clustering algorithms used; (ii) Morphotrees did not agree with RAPD-trees and not show a distinct biogeographical pattern. However, a rather distinct biogeographical population structure became recognisable when morphological features and RAPD-fingerprints were combined in a single similarity tree, indicating (iii) a certain degree of geographical uniqueness of various genotypes. Generally, however, separation was rather weak and highly dependent on the indices and clustering algorithms used, indicating that, at the present state of knowledge, most Gonostomum affine-like morphotypes fall into the range of natural variability of a single species.
Keywords: biodiversity, biogeography, Ciliophora, Protozoa, similarity trees, soil ciliates.