Comparative life‐history traits in a fig wasp community: implications for community structure

Abstract

1. Whether life‐history traits can determine community composition and structure is an important question that has been well explored theoretically, but has received scant empirical attention. Life‐history traits of a seven‐member community of galler and parasitoid fig wasp species (Chalcidoidea), developing within the inflorescences (syconia) of Ficus racemosa (Moraceae) in India, were determined and used to examine community structure and ecology. 2. Gallers were pro‐ovigenic (all eggs are mature upon adult emergence) whereas parasitoids were synovigenic (eggs mature progressively during adult lifespan). Initial egg load was correlated with body size for some species, and there was a trade‐off between egg number and egg size across all species. Although all species completed their development and left the syconium concurrently, they differed in their adult and pre‐adult lifespans. Providing sucrose solutions increased parasitoid lifespan but had no effect on the longevity of some galler species. While feeding regimes and body size affected longevity in most species, an interaction effect between these variables was detected for only one species. 3. Life‐history traits of wasp species exhibited a continuum in relation to their arrival sequence at syconia for oviposition during syconium development, and therefore reflected their ecology. The largest number of eggs, smallest egg sizes, and shortest longevities were characteristic of the earliest‐arriving galling wasps at the smallest, immature syconia; the converse characterised the later‐arriving parasitoids at the larger, already parasitised syconia. Thus life history is an important correlate of community resource partitioning and can be used to understand community structure. 4. This is the first comprehensive study of life‐history traits in a fig wasp community. The comparative approach revealed constraints and flexibility in trait evolution.

Trade-Offs and Coexistence in Fluctuating Environments: Evidence for a Key Dispersal-Fecundity Trade-Off in Five Nonpollinating Fig Wasps

“…While the strength of competition among nonpollinating fig wasps has not been estimated, interspecific competition among nonpollinators should be comparable to that of pollinators where ovule resources are limiting and overlapping (e.g., Ghara et al 2014). Observations from wild populations find that nonpollinators regularly compete with pollinators for access to overlapping ovule resources (e.g., West and Herre 1994;Kerdelhué and Rasplus 1996;West et al 1996;Kerdelhué et al 2000;Ghara and Borges 2010), and experimental manipulations suggest that observational studies likely underestimate competition (Raja et al 2014).…”

Life history trade-offs, the intensity of competition, and coexistence in novel and evolving communities under climate change

“…First, an oft-reported trade-off between competitive ability and longevity will favour the coexistence of species able to achieve quick numerical abundance, and species with slower growth but better persistence through time [15,39]. This mechanism is particularly salient when the environment fluctuates over time [19], but intransitive dynamics mediated by interspecific differences in density-dependent regulation can also maintain the coexistence of competitors with divergent life history strategies along the slow-fast continuum within communities, even in the absence of environmental fluctuations [40]. Note that this coexistence mechanism does not depend on competitors diverging in their resource requirements or resource acquisition abilities.…”

“…Empirical evidence from damselflies, plants, parasitoids, fig wasps, fish and Drosophila all indicate that life history divergence is often a critical coexistence mechanism within guilds, where species overlap very closely in specific resource requirement and acquisition traits [14,15,18,19,39,40,43]. Life history traits are also well-characterized mediators of competition and coexistence even among more diffuse competitors [37,44].…”

Trade-Offs and Coexistence: A Lottery Model Applied to Fig Wasp Communities

“…They found variation in fecundity and longevity between these species, and while they did not measure the dispersal ability of species in the community, they noted that the abundances of species varied both locally and seasonally. Ghara and Borges (2010) suggest that the life-history traits of community members will be affected by spatiotemporal variation in figs. Egg load and wing loading estimates from the nonpollinator community associated with Ficus petiolaris strongly support the hypothesis of a dispersal ability and fecundity trade-off (Duthie 2013).…”

“…Several hypotheses have been proposed to explain nonpollinator coexistence, including differences in the timing of oviposition (Kerdelhué et al 2000;Ghara and Borges 2010) and whether it occurs from the exterior or interior of the syconium (Kerdelhué et al 2000;Ghara et al 2011). While these differences likely promote niche partitioning to some degree, it is difficult to explain the observed diversity based only on these modest differences.…”