Diaspore heteromorphism and germination in populations of the ephemeral Hedypnois rhagadioloides (L.) F.W. Schmidt (Asteraceae) inhabiting a geographic range of increasing aridity

Hedypnois rhagadioloides a heterocarpic ephemeral winter composite that inhabits Mediterranean and desert regions of Israel, produces three diaspore morphs which differ in their dispersal ability: 1) small, central pappose achenes with aristate pappi; 2) larger epappose achenes, and 3) compound diaspores consisting of marginal epappose achenes enclosed by a persistent and lignified inner involucral bract. The proportion of widely dispersed pappose achenes decreases in populations in areas of greater aridity, although the dormancy of different diaspore morphs is unaffected by population source. Germination of all diaspore morphs is light dependent, and increases at lower temperatures (15 vs 25°C). Widely dispersed pappose diaspores were less dormant than epappose diaspores. -Author