Strategies of offspring investment and dispersal in a spatially structured environment: a theoretical study using ants

Abstract

BackgroundOffspring investment strategies vary markedly between and within taxa, and much of this variation is thought to stem from the trade-off between offspring size and number. While producing larger offspring can increase their competitive ability, this often comes at a cost to their colonization ability. This competition–colonization trade-off (CCTO) is thought to be an important mechanism supporting coexistence of alternative strategies in a wide range of taxa. However, the relative importance of an alternative and possibly synergistic mechanism—spatial structuring of the environment—remains the topic of some debate. In this study, we explore the influence of these mechanisms on metacommunity structure using an agent-based model built around variable life-history traits. Our model combines explicit resource competition and spatial dynamics, allowing us to tease-apart the influence of, and explore the interaction between, the CCTO and the spatial structure of the environment. We test our model using two reproductive strategies which represent extremes of the CCTO and are common in ants.ResultsOur simulations show that colonisers outperform competitors in environments subject to higher temporal and spatial heterogeneity and are favoured when agents mature late and invest heavily in reproduction, whereas competitors dominate in low-disturbance, high resource environments and when maintenance costs are low. Varying life-history parameters has a marked influence on coexistence conditions and yields evolutionary stable strategies for both modes of reproduction. Nonetheless, we show that these strategies can coexist over a wide range of life-history and environmental parameter values, and that coexistence can in most cases be explained by a CCTO. By explicitly considering space, we are also able to demonstrate the importance of the interaction between dispersal and landscape structure.ConclusionsThe CCTO permits species employing different reproductive strategies to coexist over a wide range of life-history and environmental parameters, and is likely to be an important factor in structuring ant communities. Our consideration of space highlights the importance of dispersal, which can limit the success of low-dispersers through kin competition, and enhance coexistence conditions for different strategies in spatially structured environments.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-016-0058-z) contains supplementary material, which is available to authorized users.

Evolution of dispersal and the maintenance of fragmented metapopulations

“…In contrast, large seeds have restricted dispersal due to their weight but contain more resources (Cheptou et al, 2008). In social insects, dispersal and reproduction could follow from the production of many isolated queens that fly large distances and have high mortality or through the split of the colony in a few propagules that usually disperse on short distances but may be more efficient at gathering resources when founding the new colonies (Cronin et al, 2013(Cronin et al, , 2016. Fragmentation affects strategies along the competition-colonization trade-off in different ways.…”

Fine-scale habitat heterogeneity favours the coexistence of supergene-controlled social forms in Formica selysi

“…Colonization-competition trade-offs are often discussed in the framework of species coexistence, where a species occupies the “colonizer niche” by efficiently colonizing empty habitats, and the other the “competitive niche” by outcompeting the first species locally [ 36 – 39 ]. Two studies, one experimental and the other theoretical, suggest that such trade-offs play a role in the coexistence of ant species with alternative modes of dispersal and colony founding strategies [ 40 , 41 ]. Here, we investigate if competition and colonization in heterogeneous habitats plays a role in the coexistence of social forms within one ant species.…”

Geographic patterns in colonial reproductive strategy inMyrmecina nipponica: Links between biogeography and a key polymorphism in ants

“…Another important reproductive trait is the mode through which new colonies are founded. Social insects employ two principal modes of colony reproduction with markedly contrasting cost/benefit characteristics and major implications for dispersal and population genetics (Cronin, Loeuille, & Monnin, 2016; Cronin, Molet, Doums, Monnin, & Peeters, 2013; Peeters & Molet, 2010). Under independent colony foundation (ICF), individual queens disperse on the wing and found new colonies alone.…”

“…In army ants ( Eciton burchelli ), for example, the parent colony divides the worker force more or less evenly among two new colonies (Gotwald, 1995). This strategy can markedly improve the survival of new colonies but, because ant workers are wingless, comes at a cost of severely curtailed dispersal (Cronin et al., 2013, 2016; Peeters & Molet, 2010). In ants, these modes of reproduction are typically associated with differences in queen morphology: ICF queens are winged, with enlarged thoraces housing fat reserves and flight muscles, whereas DCF queens are more worker‐like in morphology (‘ergatoid’) and cannot fly (Peeters, 2012).…”

“…Although ICF provides a clear advantage in terms of dispersal, other aspects of life history such as competitive ability and generation time are enhanced under DCF. Different strategies are thus favoured by different environments, with DCF favoured by competitive ability in homogeneous environments and ICF benefiting from factors increasing colonization opportunities (Cronin et al., 2016; Peeters & Molet, 2010; Tilman, 1994). The limited available evidence from field studies of species which can employ both strategies supports this: Heinze (1993) found that in Leptothorax sp.…”