Opening myrmecochory's black box: what happens inside the ant nest?

Abstract

In the process of seed dispersal by ants (myrmecochory), foragers bring diaspores back to their nest, then eat the elaiosome and usually reject viable seeds outside the nest. Here, we investigate what happens inside the nest, a barely known stage of the myrmecochory process, for two seed species (Viola odorata, Chelidonium majus) dispersed either by the insectivorous ant Myrmica rubra or by the aphid-tending ant Lasius niger. Globally, elaiosome detachment decreased ants' interest towards seeds and increased their probability of rejecting them. However, we found marked differences in seed management by ants inside the nest. The dynamics of elaiosome detachment were ant-and plant-specific whereas the dynamic of seed rejection were mainly antspecific. Seeds remained for a shorter period of time inside the nest of the carnivorous ant Myrmica rubra than in Lasius niger nest. Thus, elaiosome detachment and seed rejection were two competing dynamics whose relative efficiency leads to variable outcomes in terms of types of dispersed items and of nutrient benefit to the ants. This is why some seeds remained inside the nest even without an elaiosome, and conversely, some seeds were rejected with an elaiosome still attached. Fresh seeds may be deposited directly in contact with the larvae. However, the dynamics of larvae-seeds contacts were also highly variable among species. This study illustrates the complexity and variability of the ecological network of ant-seed interactions.

Impact of seed abundance on seed processing and dispersal by the red ant Myrmica rubra

“…As found in previous studies (Servigne & Detrain, 2010;Prior et al, 2014), M. rubra workers handle and keep seeds inside their nest, albeit for a shorter time than other ant dispersers, such as the black garden ant, Lasius niger. As found in previous studies (Servigne & Detrain, 2010;Prior et al, 2014), M. rubra workers handle and keep seeds inside their nest, albeit for a shorter time than other ant dispersers, such as the black garden ant, Lasius niger.…”

“…As found in previous studies (Servigne & Detrain, 2010;Prior et al, 2014), M. rubra workers handle and keep seeds inside their nest, albeit for a shorter time than other ant dispersers, such as the black garden ant, Lasius niger. This also confirms that the detachment of the elaiosome from the C. majus diaspore is a prerequisite to its subsequent discarding by M. rubra ants (Hughes & Westoby, 1992;Gorb & Gorb, 2003;Servigne & Detrain, 2010;Canner et al, 2012). The elaiosome detachment and the subsequent discarding of seeds occurred for the majority of diaspores after 24 and 36 h for the small and large seed sources, respectively.…”

Seed manipulation by ants: disentangling the effects of ant behaviours on seed germination

“…However, seed manipulation by ants can also play a key role in seed germination through mechanical and chemical behaviours (Leal & Oliveira, 1998;Pizo & Oliveira, 1998;Ohkawara & Akino, 2005;Leal et al, 2007;Prior et al, 2014). When ants manipulate myrmecochorous seeds, two non-mutually exclusive physical behaviours may occur: (i) ants detach the elaiosome for feeding (Servigne & Detrain, 2010;Caut et al, 2013;Prior et al, 2014); and (ii) ants scarify the seeds, damaging the seed coat (Horvitz, 1981;Zettler et al, 2001). Other non-physical manipulation effects may also take place; for instance, ants can release anti-fungal substances that reduce chances of microbial infection of non-myrmecochorous seeds (Ohkawara & Akino, 2005).…”

Seed re‐dispersal of four myrmecochorous plants by a keystone ant in central China

“…While seeds re-dispersed from nests may further increase dispersal distances away from the parent plant and reduce sib competition (Canner et al 2012), it may also re-expose seeds to predators like rodents and insects (Hughes and Westoby 1992;Lô bo et al 2011;Tanaka et al 2015). Furthermore, discarded seeds often have the elaiosome only partially removed (Servigne and Detrain 2010;Beaumont et al 2013), as there is much interspecific variation in elaiosome location and tissue origin (Sernander 1906;Gorb and Gorb 2003). Thus, the likelihood of elaiosome removal by ants may be variable and may affect subsequent attraction to rodents.…”