Mutualism fails when climate response differs between interacting species

Abstract

Successful species interactions require that both partners share a similar cue. For many species, spring warming acts as a shared signal to synchronize mutualist behaviors. Spring flowering plants and the ants that disperse their seeds respond to warming temperatures so that ants forage when plants drop seeds. However, where warm-adapted ants replace cold-adapted ants, changes in this timing might leave early seeds stranded without a disperser. We investigate plant seed dispersal south and north of a distinct boundary between warm- and cold-adapted ants to determine if changes in the ant species influence local plant dispersal. The warm-adapted ants forage much later than the cold-adapted ants, and so we first assess natural populations of early and late blooming plants. We then transplant these plants south and north of the ant boundary to test whether distinct ant climate requirements disrupt the ant-plant mutualism. Whereas the early blooming plant's inability to synchronize with the warm-adapted ant leaves its populations clumped and patchy and its seedlings clustered around the parents in natural populations, when transplanted into the range of the cold-adapted ant, effective seed dispersal recovers. In contrast, the mutualism persists for the later blooming plant regardless of location because it sets seed later in spring when both warm- and cold-adapted ant species forage, resulting in effective seed dispersal. These results indicate that the climate response of species interactions, not just the species themselves, is integral in understanding ecological responses to a changing climate. Data linking phenological synchrony and dispersal are rare, and these results suggest a viable mechanism by which a species' range is limited more by biotic than abiotic interactions - despite the general assumption that biotic influences are buried within larger climate drivers. These results show that biotic partner can be as fundamental a niche requirement as abiotic resources.

Forest invader replaces predation but not dispersal services by a keystone species

“…We focused on plant aggregation because the end result of failed seed dispersal by ants is increased seedling clumping around parents. Results from previous studies have linked failed dispersal with unsuitable abiotic habitat for A. rudis (Giladi 2004;Warren II and Bradford 2013;Warren II et al 2010;Zelikova et al 2011). We did not find microclimate associated with plant aggregation, suggesting that ''unsuitable habitat'' in this instance was a biotic consequence of B. chinensis presence.…”

Ant-mediated seed dispersal in a warmed world

“…Such specialization in interactions can make interaction networks more vulnerable to disruption as a result of low levels of functional redundancy within a system (Aizen, Sabatino & Tylianakis, 2012). Myrmecochorous plant species that rely on a single ant species (or species complex) for seed dispersal may be at increased risk for disruption by ongoing climatic change (Pelini et al, 2011a; Warren, Bahn & Bradford, 2011; Warren & Bradford, 2013) if that ant species is negatively affected by warming. Inversely, systems in which multiple species are responsible for removing seeds may prove to be more resistant to disruptions because of functional redundancy in the system (Peterson, Allen & Holling, 1998).…”

“…Inversely, systems in which multiple species are responsible for removing seeds may prove to be more resistant to disruptions because of functional redundancy in the system (Peterson, Allen & Holling, 1998). However, despite the importance and ubiquity of myrmecochory in ecosystems around the world and the importance of temperature in regulating ant foraging, experiments examining the consequences of climatic change on this mutualism are rare (but see Pelini et al, 2011a; Warren & Bradford, 2013). …”

Adding Biotic Interactions into Paleodistribution Models: A Host-Cleptoparasite Complex of Neotropical Orchid Bees

“…mutualism, parasitism) to survive and reproduce. Nonetheless, during historical and current scenarios of climate change, such interactions may uncouple or fail given spatial or phenological mismatches between the interacting species [75–79]. Therefore, further investigation on how interacting species will behave upon future climate changes are needed especially given concerning scenarios of biodiversity loss [80–82] for a better assessment on how will species interactions maintain themselves in the future.…”