Dispersal of non-myrmecochorous plants by a “keystone disperser” ant in a Mediterranean habitat reveals asymmetric interdependence

Abstract

In contrast to other plant-animal mutualisms, seed dispersal interactions, and particularly seed dispersal by ants, are generally considered asymmetric, non-specialized relationships in which dispersers depend less on plants than vice versa. Although myrmecochory is well understood in many terrestrial ecosystems, dispersal of non-elaiosomebearing seeds by ants has barely been studied outside the Neotropics. Aphaenogaster senilis, a common ant in Southern Spain, collects a great variety of non-myrmecochorous diaspores along with insect prey. At our study site, fleshy fruits of Arum italicum, Phillyrea angustifolia and Pistacia lentiscus represent up to one-fourth of the items collected by A. senilis from June to November. However, they are mostly ignored by other ants. In the laboratory, the addition of A. italicum fruits to A. senilis insect-based diet increased male production and both worker and queen pupae size. Seeds were transported up to 8 m away from the mother plant and deposited in a favorable habitat allowing a relatively high proportion of germination. Given important differences in seed production between species, our data suggest that A. senilis removes virtually all seeds of A. italicum, but a negligible fraction of P. lentiscus seeds. We conclude that in contrast to the common view, dispersal of non-myrmecochorous Mediterranean plants by ants might be an important phenomenon. Keystone disperser ants like A. senilis probably obtain an important fitness advantage from non-myrmecochorous diaspore collection. However, plant benefit may vary greatly according to the amount of seeds per individual plant and the existence of alternative dispersal agents.

Investment in reward by ant-dispersed plants consistently selects for better partners along a geographic gradient

“…Those keystone dispersers do not consume seeds (only the elaiosome), keep small colony size, frequently relocate their nest, forage solitarily, have excellent food detection capabilities and redisperse seeds beyond the nest limit (see Warren and Giladi (2014) for a detailed list). The large Cataglyphis species in our system (mainly C. savignyi and C. israelensis ) share many of the traits characterizing well-known keystone dispersers (Gorb and Gorb 1995; Boulay et al 2007 b ; Gove et al 2007; Barroso et al 2013; Leal et al 2014). Furthermore, the results from this study and our additional observations indicate that large Cataglyphis in our system disperse myrmecochorous seeds at high rates, to long distances (up to 40 m) and redisperse the seeds to favourite sites for plants establishment.…”

Diversity of the Formicidae (Hymenoptera) carrion communities in Lisbon (Portugal): preliminary approach as seasonal and geographic indicators

“…Like the previous species, A. senilis also appeared in very small numbers, in winter, spring and summer and in several stages of decomposition. The individual way the workers of this species carry their forage activity [ 50 ] may explain this reduced number of collected specimens.…”

“…Colonies often move their nests to open areas in the spring and autumn and to shady areas in the summer. Workers are individual foragers moving quickly [ 50 ]. They are omnivores feeding on both seeds and animal remains.…”

The use of branch piles to assist in the restoration of degraded semiarid steppes

“…Ants were never observed carrying seeds out of the trays nor we detected any sign of rodent presence. Previous studies have found a negligible effect of ants on the removal of P. lentiscus seeds (Aronne & Wilcock 1994;Barroso et al 2013). The effect of seed predators may be expected to be larger under shrub patches where more seeds and noningested fruits accumulate, which should attract more seed predators (Alcántara et al 2000).…”