Ants as diaspore removers of non‐myrmecochorous plants: a meta‐analysis

Abstract

Diaspore (e.g. seeds, fruits) dispersal is pivotal for plant communities and often involves several steps and different dispersing agents. Most studies focusing on diaspore dispersal by animals have highlighted the role of vertebrates, neglecting the role of ants in the diaspore dispersal of non‐myrmecochorous plants. Diaspore dispersal by ants is especially relevant in the current scenario of declining of vertebrate populations and, consequently, collapse of the dispersal system of large‐seeded plants. Although ants can never compensate for the dispersal service provided by vertebrates, they can mitigate the impact of vertebrate decline via removal of diaspores deposited on the ground. We have used a meta‐analytical approach to investigate the contribution of ants in the removal of non‐myrmecochorous diaspores (through vertebrate exclusion experiments). We considered the number of diaspore removal as effect size and factors such as plant growth forms, diaspore and ant size, habitat type as moderators. In addition, we investigated the role of such factors on the diaspore removal distance by ants. Ants played complementary role to non‐myrmecochorous diaspore removal services provided by vertebrates (mean Hedges’ g of −0.30). The ant diaspore removal was 69% higher for diaspores from shrubs than that of tree diaspores and removal of small‐sized diaspores were 69% and 70% higher in comparison to medium‐ and large‐sized diaspores, respectively. Regarding the diaspore removal distance by ants, those of tree species were removed 32% farther than those of shrub species, and diaspores were removed three‐ times farther in the savanna than in rainforest ecosystems. Our results highlight the shrubs and small‐sized diaspores. Regarding the diaspore removal distance, the ants can be crucial for the dispersal of tree diaspores and in the savanna ecosystems. Finally, considering the biodiversity crisis, the ants may play an even more important role than appreciated in diaspores dispersal.

Role of ants as dispersers of native and exotic seeds in an understudied dryland

“…In this sense, dispersal distance could help to reduce parent or sibling competition, which is especially critical when resources are limited, allowing plants to colonise new sites and favouring their establishment (Higashi et al, 1989;Boyd, 1996). Even when some benefits, such as longer life expectancy and higher fecundity, are evident with short dispersal distances (at least 51 cm; Kjellsson, 1991), the longer the distance, the greater the advantage for plants (Kjellsson, 1991;Schupp et al, 2010;Anjos et al, 2020). In addition, dispersal of seeds to nutrient-enriched and eventually wetter ant nests represent greater germination, growth, and survival of the seedlings and higher reproduction suitability for the plants compared to random locations (Hanzawa et al, 1988;Passos & Oliveira, 2002;Frouz & Jilková, 2008;Farji-Brener & Werenkraut, 2017).…”

“…Despite the relevance of myrmecochory in drylands, especially in America (e.g. Leal et al, 2007Leal et al, , 2014Aranda-Rickert & Fracchia, 2011;Luna et al, 2018;Anjos et al, 2020), there are no detailed studies of ant-seed interactions in Patagonia. However, a recent work suggests that several ant species can interact with seeds and potentially disperse them in the semi-arid Patagonian steppe (Pirk & Lopez de Casenave, 2017), but the details of these interactions and the dispersal effectiveness of the ant species involved remains to be determined.…”

Can variation in seed removal patterns of Neotropical pioneer tree species be explained by local ant community composition?

“…Ants play a role in both short‐distance dispersal and long‐distance dispersal (Gómez & Espadaler, 2013), removing seeds from the soil surface where they are more likely to be eaten by granivores (Bond & Slingsby, 1984; Christian & Stanton, 2004; O’Dowd & Hay, 1980), and providing suitable microsites for germination and growth (Culver & Beattie, 1980; Davidson & Morton, 1981; Hanzawa et al., 1988). Some plants encourage seed dispersal by providing an elaiosome attached to their seeds, while others participate in ant‐mediated dispersal without providing a food reward (e.g., Anjos et al., 2020; Barroso et al., 2013; Christianini & Oliveira, 2010; Passos & Oliveira, 2002; Pizo & Oliveira, 1998; Magalhães et al, 2018). Even among ants that use seeds as resources, not all ants are attracted equally to seeds of different plant species.…”

Structure of ant-diaspore networks and their functional outcomes in a Brazilian Atlantic Forest

“…Ants and plants interact in a variety of ways, from parasitism to mutualism (Beattie, 1985), including interactions with diaspores (i.e. : dispersal unit) that can result in seed dispersal (Anjos et al, 2020;Luna et al, 2021). Seed dispersal is a fundamental process for plant fitness because it determines the location in which seeds arrive and whether they will be able to develop and reach future stages in that location (Wenny, 2001).…”

“…These conditions favour germination in ants' nesting soils for some plant species (Passos & Oliveira et al, 2002;Leal et al, 2007). Diaspore removal generally occurs at short distances, with a global mean dispersal distance of 2.39 m for nonmyrmecochorous diaspores (Anjos et al, 2020). Removal distance depends on ants' nest density and on diaspore disposition in relation to the nests.…”