4.1 | Dispersal of elaiosome-less seeds by ants
In this study, we first verified that M. humile seeds without
elaiosomes surely attracted ants. We have confirmed that 9 out of 80
untreated seeds were carried to the ant nest, whereas no treated seeds
were carried (Table S1). We also found that by using dummy seeds coated
with the odor components of M. humile seeds, those dummy seeds
treated with a mixture of 6 major components were carried to the nest by
the ants, although the dummy seeds treated with the solvent were not
carried away (Table S3). Among the 6 main odor components, linalool and
α-terpineol were also identified as floral scents of M. humile ,
but the other 4 components were not identified (Kubo & Ono, 2014).
These results indicate that M. humile seeds attracted ants by
their seed or fruit specific odor mixture. In the pepper family plant,Peperomia macrostachya , the mixture of seed odors efficiently
attracts the ant, Camponotus femoratus (Youngstead et al., 2007).
Since the volatile seed odors would have disappeared in 72 h, the dummy
seeds were abandoned outside the nest. Similarly, the seeds are likely
to be abandoned after the outer fruity coating components are consumed.
Therefore, even in the absence of elaiosomes, some plants, includingM. humile , could disperse their seeds through the ants using a
specific blend of odor components.
Hence, ants are thought to participate in the seed dispersal of M.
humile, in addition to herbivorous insects, such as cockroaches and
camel crickets (Suetsugu 2017; Uehara & Sugiura 2017), and the seed
dispersal by ants could be beneficial for the achlorophyllous species.
With regards to the seed dispersal by ant, the seed-discards or
left-inside-the-nest indicated that dispersal by ants should be
important for plant seeds of such achlorophyllous plants as M.
humile . The plant does not depend solely on the myrmecochory, as
Suetsugu 2017 reported many of seeds have been detected from the
herbivorous insects’ excretion. Because the number of seeds carried in
our assay is relatively small, myrmecochory of the species could be one
aspect of their zoochory.