" - • " ' " -' - - ••" ISRAEL JOURNAL OF PLANT SCIENCES, Vol. 43, 1995, pp. 347-358 THE BREEDING SYSTEMS OF THREE ANNUAL CLOVERS NATIVE TO NORTH SYRIA M.A. PAGNOTTA,3-* P.S. COCKS," AND R.W. SNAYDONC aDipartimento di Agrobiologia e Agrochimica, Universita degli Studi della Tuscia, Via S. Camilla de Lellis, Oil00 Viterbo, Italy ^Faculty of Agriculture, The University of Western Australia, Nedlands, WA 6009, Australia 'Agricultural Botany Department, University of Reading, Whiteknights, Reading RG6 2AS, UK ABSTRACT The breeding systems of three clovers (Trifolium stellatum, T. tomentosum, and T. campestre) were studied by measuring (a) seed production under forced selfing and crossing, and (b) morphological variation between and within families derived from seeds collected in the field. The results indicate that all three species are both self- and cross-compatible. However, since morphological variation within families was small compared with variation between families, the three species seem to be predominantly inbreeding in the field. This is confirmed by the fact that field populations are genetically heterogeneous and composed of mainly homozygous individuals. INTRODUCTION The breeding systems of a species are an important determinant both of its potential for evolutionary change and its colonizing ability. For example, outbreeding increases the incidence of both genetic recombination and gene flow, leading to the maintenance of genetic variability, and giving a greater potential for evolutionary change (Rollins, 1967). However, there are disadvantages in outbreeding; for example, dependence on the presence of pollination vectors and of adjacent compatible genotypes may limit seed output, and may also limit colonizing ability of the species (Cruden, 1977; Lloyd, 1984; Levin, 1986). By contrast, inbreeding restricts genetic recombination and gene flow, thereby maintaining adapted combinations of genes, but this can lead to homozygosity and homogeneity within populations, and so can restrict the opportunity for rapid evolutionary change. Inbreeding would seem to offer advantages for colonizing species (Price and Jain, 1981; Jain, 1983), since a single individual can provide the basis for a new population (Baker, 1955, 1967; Stebbins, 1957, 1958; Antonovics, 1968). It is *Author to whom correspondence should be addressed. Received 19 June 1995.