Differential importance of consecutive dispersal phases in two ant-dispersed Corydalis species
22 September 2017
Zhu, Yan; Wang, Dong; Zhang, Lingyu; Liu, MuxingSeed dispersal of myrmecochorous plants, in which a sequence of two or more steps involved, has profound effects on plant benefits. In general, when seeds mature or fall onto to the ground (primary dispersal), ants then transport them into nests (ant dispersal), and sometimes ants discarded seeds out of nests (re-dispersal). By neglecting attributable phases, we might misjudge the possible benefits of plants conferred by myrmecochory. Here, we investigated the variation in the potential importance of each dispersal step between two myrmecochorous plants, Corydalia incisa and C. wilfordii which are common to China, by examining (1) primary dispersal distance, (2) seed removal rates and dispersal distance by ants, and (3) frequency of seeds discarded out of nests and the re-dispersal distance. The mean primary dispersal distance of C. incisa was about eightfold further than C. wilfordii. Two ant species, Pheidole noda and Pristomyrmex pungens are major dispersers. The presence of elaiosome increase the attractiveness of seeds to ants, while both the removal rate and dispersal distance were greater for C. wilfordii than for C. incisa. P. noda, the larger-bodied species, discarded most seeds of both species out of nests, whereas P. pungens, the smaller one, discarded only C. wilfordii seeds. The mean re-dispersal distances of the two species were similar, while that of C. incisa and C. wilfordii were about threefold and fivefold shorter than the distances in the step of ant dispersal, respectively. In field, no predators were found to interact with the discarded seeds in 72 h. The results indicated that the importance of each dispersal phase were variable between the two Corydalis species, which was primarily attributed to differential role of ant identity and seed characteristics. As an additional phase of ant dispersal, re-dispersal should be also taken into consideration in understanding the plant benefits of myrmecochory.