Differentiation in populations of Hordeum spontaneum Koch along a gradient of environmental productivity and predictability: Intra- and interspecific competitive responses

We compared intra- and interspecific competitive responses of wild barley, Hordeum spontaneum, from four populations originating in distinct environments in Israel. The environments ranged along two parallel gradients of rainfall amount and predictability, from low (desert) to moderate (semi-steppe batha) to high (Mediterranean grassland and mountain, the latter also experiencing frost stress). The target barley plants grew under one of five densities (0, 4, 8, 16, and 32 surrounding plants per bucket) of either barley from the same population or oats (Avena sterilis) from a neutral population. The traits examined included estimates of fitness, reproductive traits, and resource allocation. The effect of intraspecific competition was stronger than interspecific competition at a high increment of neighbor density (from 4 to 32 neighbors). There was no difference in interspecific competitive responses of plants originating in the four environments at any neighbor density increments, but intraspecific competi...