Diaspore dispersal ability and degree of dormancy in heteromorphic species of cold deserts of northwest China: A review

The cold deserts of northern Xinjiang Province in northwest China are rich in diaspore-heteromorphic species, and diaspore biology has been compared in more heteromorphic species native to this biogeoclimatic region than for any other region worldwide. Our primary purpose was to compare the dispersal ability and degree of dormancy in heteromorphic diaspores in Xinjiang desert plants via a review of the Chinese and English literature. We located literature on 20 heteromorphic species native to these deserts. Fourteen of the species are chenopods (Amaranthaceae). All 20 species are heterodiasporous (dimorphic, 14; trimorphic, 4; polymorphic, 2) annuals, and none is amphicarphic sensu stricto. Thirteen of the species are heterocarpic, six heterospermic, one amphi-basicarpic and none heteroarthrocarpic. Diaspores of 19 of the species differ in seed dormancy/germination. Thirteen of the 14 species to which both diaspore dispersal ability and degree of dormancy could be assigned had at least one morph with high (or relatively high) dispersal ability and low degree of dormancy and at least one with low dispersal ability and high (or relatively high) degree of dormancy. Conceptual models of the dynamics of seed dormancy of the two morphs for each of three dimorphic species suggest the ecological significance of heterodiaspory in the cold desert annuals. However, the ecological significance of seed/fruit heteromorphism needs to be more thoroughly demonstrated via long-term field studies that compare the life history/demography of plants derived from different morphs.