Linking phenological shifts to species interactions through size‐mediated priority effects

Abstract

Summary1. Interannual variation in seasonal weather patterns causes shifts in the relative timing of phenological events of species within communities, but we currently lack a mechanistic understanding of how these phenological shifts affect species interactions. Identifying these mechanisms is critical to predicting how interannual variation affects populations and communities. 2. Species' phenologies, particularly the timing of offspring arrival, play an important role in the annual cycles of community assembly. We hypothesize that shifts in relative arrival of offspring can alter interspecific interactions through a mechanism called size-mediated priority effects (SMPE), in which individuals that arrive earlier can grow to achieve a body size advantage over those that arrive later. 3. In this study, we used an experimental approach to isolate and quantify the importance of SMPE for species interactions. Specifically, we simulated shifts in relative arrival of the nymphs of two dragonfly species to determine the consequences for their interactions as intraguild predators. 4. We found that shifts in relative arrival altered not only predation strength but also the nature of predator-prey interactions. When arrival differences were great, SMPE allowed the early arriver to prey intensely upon the late arriver, causing exclusion of the late arriver from nearly all habitats. As arrival differences decreased, the early arriver's size advantage also decreased. When arrival differences were smallest, there was mutual predation, and the two species coexisted in similar abundances across habitats. Importantly, we also found a nonlinear scaling relationship between shifts in relative arrival and predation strength. Specifically, small shifts in relative arrival caused large changes in predation strength while subsequent changes had relatively minor effects.5. These results demonstrate that SMPE can alter not only the outcome of interactions but also the demographic rates of species and the structure of communities. Elucidating the mechanisms that link phenological shifts to species interactions is crucial for understanding the dynamics of seasonal communities as well as for predicting the effects of climate change on these communities.

Approximation of a physiologically structured population model with seasonal reproduction by a stage-structured biomass model

“…Interactions between different species may change due to climatic changes. More specifically, the synchronicity between species over different ontogenetic life stages can make up species interactions and potentially determine a species success (Yang and Rudolf 2010;Rasmussen et al 2014). For example, hatching phenology of predatory salamanders has been shown to determine their size-specific interaction with frog tadpoles (Nosaka et al 2015).…”

“…It has been shown that the time of hatching of a predator relative to the time of hatching of its prey determines the performance of predators (Rasmussen et al 2014;Nosaka et al 2015). Moreover, it is thought that seasonal reproduction may structure the extent of trophic control and trophic cascades in food chains (van Leeuwen et al 2007;Nakazawa and Doi 2012).…”

Commentary: Novel competitors shape species' responses to climate change

“…For example, in alpine communities, cushion plants can ameliorate environmental conditions and thereby increase the survival of other species leading to higher species richness (Cavieres et al, 2014). On the other hand, inhibitory priority effects can occur through legacies in the plant-soil feedbacks (Grman and Suding, 2010) or size-mediated priority effects and asymmetric competition (Weiner, 1990;Rasmussen et al, 2014). Size-mediated or size-asymmetric priority effects is the unequal competitive ability between different stages of the established and the novel species, such that incumbent species with adult individuals have an inherent competitive advantage over seeds or seedlings from the incoming species which must germinate and establish.…”

Effects of environmental warming during early life history on libellulid odonates

“…The timing of egg laying and hatching determines the abiotic conditions (Visser and Holleman 2001) and the biotic interactions of juveniles (Rudolf and Singh 2013). Larval odonates are voracious predators and the order and relative timing in which species hatch can determine body-size advantages (Rasmussen et al 2014), a crucial force structuring species interactions in aquatic systems (Werner and Gilliam 1984). Unequal responses to warming could affect the rank order of hatching within groups of co-occurring species, thereby contributing to these body-size advantages or disadvantages (Guo et al 2009).…”