Asynchrony between ant seed dispersal activity and fruit dehiscence of myrmecochorous plants

Abstract

Premise of the Study Phenological mismatch has received attention in plant–pollinator interactions, but less so in seed dispersal mutualisms. We investigated whether the seasonal availability of myrmecochorous seeds is well matched to the seasonal activity patterns of seed‐dispersing ants. Methods We compared seasonal timing of seed removal by a keystone seed‐dispersing ant, Aphaenogaster rudis, and fruit dehiscence of several species of plants whose seeds it disperses in a deciduous forest in southern Ontario, Canada. We examined the timing of elaiosome “robbing” by the nonnative slug Arion subfuscus and tested whether seed removal by ants declines in response to supplementation with additional elaiosome‐bearing seeds (ant “satiation”). Key Results Seed removal from experimental depots peaked early in the season for all plant species and correlated with temperature. In contrast, elaiosome robbing by slugs increased late in the season and thus may disproportionately affect plants with late‐dehiscing fruits. Ant colonies removed seeds at similar rates regardless of seed supplementation, indicating that satiation likely does not impact seasonal patterns of seed dispersal in this system. Fruits of the five myrmecochorous plant species in our study dehisced at discrete intervals throughout the season, with minimal overlap among species. Peak dehiscence did not overlap with peak seed removal for any plant species. Conclusions Fruit dehiscence of myrmecochorous plants and peak ant seed dispersal activity occur asynchronously. Whether future climate warming will shift ant and plant phenologies in ways that have consequences for seed dispersal remains an open question.

Effects of seed morphology and elaiosome chemical composition on attractiveness of five Trillium species to seed‐dispersing ants

“…In the southern Appalachian region, many species of Trillium are sympatric. Although co-occurring myrmecochore species often temporally stagger fruiting (Gordon, Meadley-Dunphy, Prior, & Frederickson, 2019;Warren, Giladi, & Bradford, 2014), the sympatric species studied here have overlapping flowering and fruiting phenology (Miller & Kwit, 2018).…”

“…In the southern Appalachian region, many species of Trillium are sympatric. Although co‐occurring myrmecochore species often temporally stagger fruiting (Gordon, Meadley‐Dunphy, Prior, & Frederickson, ; Warren, Giladi, & Bradford, ), the sympatric species studied here have overlapping flowering and fruiting phenology (Miller & Kwit, ). Due to the spatial proximity of plants at our study sites, foraging ants occasionally come across mature diaspores of co‐occurring congeners at the same time (C. N. M., personal observation), resulting in potential interspecific competition for dispersal services.…”

Interactions between seed‐dispersing ant species affect plant community composition in field mesocosms

“…While this could affect colony foraging and aggressive behaviour (Grangier & Lester, 2014), it ensured all colonies started the experiment in a similar nutritional state. Seeds of four myrmecochore species (see above) were collected when fruits were naturally dehiscing in the field at KSR (mid‐June 2013; Gordon, Meadley‐Dunphy, Prior, & Frederickson, 2019), and stored at –20°C until use (for approx. 2 months).…”

“…Seeds of four myrmecochore species (see above) were collected when fruits were naturally dehiscing in the field at KSR (mid-June 2013; Gordon, Meadley-Dunphy, Prior, & Frederickson, 2019), and stored at -20°C until use (for approx. 2 months).…”

Antagonistic and mutualistic interactions alter seed dispersal of understory plants at forest edges

“…In each depot, we placed 8 seeds of either two myrmecochorous plant species commonly found in the area, A. canadense and S. canadensis (alternating between plots). Both species release seeds around the same time (late June; Gordon et al 2019) and have similar traits related to dispersal (e.g., seed size, ratio of elaiosome to diaspore, and oleic acid concentrations), with Aphaenogaster sp. showing little difference in preference for seeds of these species (Prior et al 2015).…”