Ecogeography of annual legumes in Syria: distribution patterns.
Climate and soil factors influencing the distribution of annual legume species collected at 207 sites throughout Syria were investigated by cluster analysis. Different genera showed distinct geographic preferences in relation to rainfall and alt. soil pH lime content. Species fell into 6 categories in relation to soil type. The largest category was restricted to alkaline soils with a smaller proportion exhibiting calcicole or calcifuge behaviour. Strict neutrophiles and widely tolerant species were less common. Species diversity and the size of the legume seed populations were identically related to annual rainfall patterns, with wetter areas having high diversity and seed densities. The av. seed density/species was 3.5 g/m2. Annual legumes appeared to be relatively resilient to overgrazing and were an important component of non-arable land in all but the driest areas. It is suggested that collection of plants for genetic conservation should be directed to species of dry areas where pressures on populations are most severe, and to those species of wet areas which are not widely distributed. Techniques for defining and bulking duplicate samples held in ex situ collections are suggested. The value of ecogeographic data for identifying rare or isolated populations of potential genetic interest and for selecting suitable species for diverse environments is demonstrated.