Study on coevolution between pollinators and caragana ssp. in the inner mongolia plateau of China

摘要

The flowering phenology, quantitative characters of flowers, breeding system and flower visitors of Caragana microphylla, C. intermedia and C. korshinskii were studied in the Inner Mongolia Plateau of China. The outcrossing indices (OCI) of the three species were 3, indicating the breeding systems of them were self-compatible, demanding for pollinators. Their pollen/ovule (P/O) ratios were 5400 ± 377, 7950 ± 1908, 4700 ± 911 respectively, indicating their breeding systems were obligate xenogamy. Meanwhile, the outcrossing level of C.intermedia was the highest among these three species. Moreover, only with the help of pollinators, the three species could accomplish their outcrossing. The flower visitors recorded on the three species were similar to each other, including at least 20 species of insects, such as Coleoptera, Hymenoptera, Lapidoptera, Diptera, Hemiptera and Thysanopters. Beetles were the most common flower visitors, followed by bees and ants, moths, flies and stinkbugs etc. The forage behaviour of flower visitors displayed that the beetles were not typical effective pollinators, but bees especially bumblebees (Bombus spp.) might be effective pollinators. These results have important implications in plant breeding, for the Caragana species' breeding system affects both the method of seed collection that should be used to conserve its genetic variation most effectively, and how its genetic resources should be used most efficiently in a breeding program.