The fig–fig wasp interaction is a classic example of obligate mutualism and coevolution. It is also a nursery pollination mutualism and supports a diversity of exploiter/parasite/non-pollinating fig wasp species. Mutualists and exploiters comprise the fig wasp community. All the wasp community members are obligately dependent on the fig syconium (a globular closed structure comprising of hundreds to thousands of uniovulate florets) for completing their life cycle. The fig florets can be sessile (without a stalk) or pedicellate (stalked) and can support a community comprising 3–30 wasp species. Fig wasps can access the floral resources for oviposition directly by entering into the syconium (internal oviposition) or by penetration of the syconium surface (external oviposition). Most studies on the fig–fig wasp interaction have investigated the stability of the interaction, pollination biology, pollen dispersal, co-evolution or the effect of exploiters on this mutualism. However, studies dealing with community ecology and species coexistence mechanisms in these communities are rare. Factors contributing to coexistence of mutualists and exploiters in a fig wasp community were studied using a reasonably speciose fig wasp community associated with Ficus racemosa in south India. The wasp community of Ficus racemosa comprises a single species of pollinator and six species of exploiters; together they represent three genera of fig wasp species. The community members show differences in their feeding habit; they could be 1) gallers (feed on floral tissue after pollination and/or after inducing abnormal tissue development of the floret that is also called the gall), 2) inquilines (feed on gall tissue but cannot induce galling; survive by feeding on gall tissue and starving the host larva to death), or 3) parasitoids (lay eggs in or on developing offspring of a galler or inquiline species; develop by feeding on host tissue). Resource partitioning across temporal and spatial axes on this fig wasp community have been quantified. Ovipositor traits of each community member were also investigated since variation in ovipositor traits might facilitate resource partitioning. Finally, the role of life-history traits in species coexistence in this community was also explored. Temporal resource partitioning among members of the fig wasp community was studied (1) across the resource phenology, i.e. over the development phases of the fig syconium, and (2) on a diel scale. The seven members of the wasp community were found to partition their oviposition periods across fig syconium development phenology; some species used very young syconia (soft and smaller in size) for oviposition whereas others used mature (hard and bigger in size) syconia for oviposition. The first species to colonise the syconia were gallers and these were followed by parasitoids in a definite oviposition sequence. Pollinators arrived concurrently with an exploiter galler species and had the shortest oviposition window in terms of days. Although fig wasps are known to be largely diurnal, night oviposition in several fig wasp species was documented for the first time. Wasp species showed a peak in their activity period across the diel cycle and phenology. This is probably the first study to simultaneously investigate temporal partitioning across the syconium phenology as well as the diel scale in a fig wasp community. Partitioning of syconium space was investigated by quantifying the quality (type of floret—sessile or pedicellate) of floral resources. The number of individuals of each species developing in a syconium was quantified along with host accessibility during oviposition by each wasp species. The association between community members developing within a syconium was also tested. The differential occupancy of florets by each species based on their distance from the base of the syconium was evaluated. For the first time the relative distribution of males and females of the entire fig wasp community was quantified. The wasp community members used similar types of florets for oviposition. Seeds were found mostly in sessile florets and wasps were present in large numbers in pedicellate florets. Except for one wasp species, all others occurred uniformly within the syconium with respect to the distance from the base of the syconium. Species distribution models revealed higher prediction ability for the location of mutualists (seed and pollinator) within the syconium compared to exploiters. Within a syconium, all species pairs exhibited positive associations indicating either an absence of or low competitive exclusion. Some florets were modified by their gall occupants such that they were longer in length indicating the possibility of creation of an enemy-free zone by the gall occupant. Yet, most florets were accessible to ovipositing wasps based on ovipositor lengths and flexibility. The probability of finding a male decreased with increase in floret length when all wasp species were grouped together; however, this trend did not hold true when males and females of species were tested individually. Based on these results, the fig wasps of F. racemosa could be grouped into—(1) Early-arriving galler species which used immature florets, inducing large galls that protruded into the cavity, and with fewer individuals per syconium, (2) Galler species arriving concurrently with the pollinator, inducing galls that were morphologically indistinguishable from those of the pollinator, and with many individuals developing per fig syconium, and (3) Parasitoids and/or inquilines of the galler species, with variable abundance per syconium. Thus, these results show that the wasp species do not clearly partition floral resources between syconia and within syconium but they can modify their oviposition sites and also differ in the proportion of florets within a syconium used for oviposition. Oviposition sites of the fig wasps can be reached only by using their ovipositor. The resources for oviposition are hidden and hence might require tools for resource location and utilisation. The frequency and diversity of sensilla on the ovipositor, as well as ovipositor structure (morphology and sclerotisation of the tip) was documented for the entire wasp community. The internally-ovipositing pollinator had the simplest ovipositor, negligible sclerotisation and only one type of sensillum on its ovipositor; the externally ovipositing exploiter species had teeth on their ovipositors, sclerotisation and various types of ovipositor sensilla. Ovipositor sclerotisation and lateness of arrival for oviposition in syconium development were positively correlated. Ovipositor teeth height increased from gallers to parasitoids. Presence of different types of sensilla was noted which included mechano- and chemosensilla, as well as combined mechano-chemosensilla. Chemosensilla were most concentrated at ovipositor tips while mechanoreceptors were more widely distributed. Ovipositor traits of one putative parasitoid/inquiline species differed from those of its syntopic galler congeners and clustered with those of parasitoids within a different wasp subfamily. Thus ovipositor tools show lability based on adaptive necessity, and are not constrained by phylogeny. Life-history traits such as fecundity, pre-adult and adult lifespan were studied for each wasp member of the community. Trade-offs in life-history traits were also investigated. Interspecific variation in life-history traits was observed. Gallers were pro-ovigenic (all eggs were mature upon adult emergence) whereas parasitoids were synovigenic (eggs matured 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 preadult 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. 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 exploited syconia. Thus life-history is an important correlate of community resource partitioning and can be used to understand community structure. The comparative approach revealed constraints and flexibility in trait evolution. This is probably the first comprehensive study of life-history traits in a fig wasp community.

Plant–animal interaction systems are complex food webs where the members—plants, pollinators, herbivores, parasites and predators of the pollinators/herbivores—interact with each other in ways which maximize their own fitness. Based on the net outcome, such interactions could be mutually beneficial to the interacting members (mutualism) or beneficial to only one of the interacting members at the cost of the other interacting members (herbivory, predation, parasitism). It is possible that such outcomes are actually a continuum and could swing in either direction from beneficial to detrimental and vice versa. Such transitions happen not only over long time scales, but could also happen within shorter time scales based on conditionalities. Conditional outcomes are those in which the outcome of an interaction between two partners is conditional on the involvement of a third partner. Thus, studying such outcomes necessitates taking into account systems beyond the classical two-partner interactions. In such complex multitrophic plant–animal interaction systems in which there are direct and indirect interactions between species, comprehending the dynamics of these multiple partners is very important for an understanding of how the system is structured. In Chapter 2 we investigate Ficus racemosa and its community of obligatory mutualistic and parasitic fig wasps that develop within the fig inflorescence or syconium, as well as their interaction with opportunistic ants. We focus on temporal resource partitioning among members of the fig wasp community over the development cycle of the fig syconia during which wasp oviposition and development occur and we study the activity rhythm of the ants associated with this community. We found that the members of the wasp community partitioned their oviposition across fig syconium development phenology and showed interspecific variation in activity across the diel cycle. The wasps presented a distinct sequence in their arrival at fig syconia for oviposition. We documented night oviposition in several fig wasp species for the first time. Ant activity on the fig syconia was correlated with wasp activity and was dependent on whether the ants were predatory or trophobiont-tending species; only numbers of predatory ants increased during peak arrivals of the wasps. In Chapter 3, we found that predatory ants (Oecophylla smaragdina) patrolling F. racemosa trees were attracted to the odour from fig syconia at different developmental phases, as well as to the odours of fig wasps, whereas other predatory ants (Technomyrmex albipes) responded only to odours of syconia from which fig wasps were dispersing and to fig wasp odour. However, trophobiont-tending ants (Myrmicaria brunnea) patrolling the same trees and exposed to the same volatiles were unresponsive to fig or fig wasp odours. The predatory ants demonstrated a concentration-dependent response towards volatiles from figs receptive to pollinators and those from which wasps were dispersing while the trophobiont-tending ants were unresponsive to such odours at all concentrations. Naıve predatory ants failed to respond to the volatiles to which the experienced predatory ants responded, indicating that the response to fig-related odours is learned. In Chapter 4 we characterise the dynamics of the volatile bouquet of the fig syconium from the initiation through pre-receptive, receptive, and late inter-floral stages which act as signals/ cues for different fig wasp species. We were also interested in diel patterns of volatile emission as some fig wasp species were strictly diurnal (the pollinator, Ceratosolen fusciceps) whereas other fig wasps such as Apocryptophagus fusca were observed ovipositing even during the nocturnal hours. We identified volatiles that were specific to syconium development phase as well as to the time of day in this bouquet. α-muurolene was identified as the sesquiterpene specific to receptive-phase as well as being present only during the day thus coinciding with the diurnal pollinator arrival pattern. Volatiles such as (E)-β-ocimene were present in increasing levels across the developmental stages of the fig and thus could act as background volatiles providing suitable information to fig wasps about host plants and their phases. Chapter 5 examines the responses of predatory and trophobiont-tending ant species to the cuticular hydrocarbon (CHC) extracts of four galler and two parasitoid fig wasp species associated with F. racemosa. Interestingly, the antennation response of both experienced and na¨ıve ants to these wasp extracts was identical indicating that prior exposure to such compounds is not necessary for eliciting such response. We also characterised these cuticular hydrocarbon extracts to find potential compounds which could as short-range cues for predatory ants. Ants were more responsive to the cuticular extracts of parasitoids rather than to those of galler wasps, implying that the CHC profile of carnivorous prey may contain more elicitors of aggressive behaviour in ants compared to herbivorous prey whose profiles may be more similar to those of their plant resources. We also find congruency between the cuticular profiles of parasitoids and their hosts suggesting that parasitoids could sequester compounds from their diet. Important findings and conclusions of the thesis are presented in Chapter 6. The first two parts of the appendices section discuss work carried out on alternative ways of analysing multivariate data sets such as plant volatiles and insect cuticular hydrocarbons. Appendix A details the use of Random Forests, an algorithm-based method of analysing complex data sets where there are more variables than samples, a situation akin to microarray data sets. This work illustrates the use of such techniques in chemical ecology, highlighting the potential pitfalls of classical multivariate tests and the advantages of newer more robust methods. Appendix B, an invited article following the publication of the earlier work, compares different data transformation procedures currently employed in such multivariate analysis. Appendix C details sex-specific differences in cuticular hydrocarbons of fig wasps, using the pollinator C. fusciceps as a case study.

Obligate nursery pollination mutualisms such as the fig–fig wasp system, with their central plant–pollinator mutualism associated with non-pollinating satellite wasp species, can function as closed system microcosms representative of tritrophic communities. In this system, enclosed inflorescences (syconia) function as sites of seed production, as well as brood-sites for the progeny of herbivorous mutualistic pollinators, non-pollinating gallers and parasitoids of the two. Plant reproductive traits such as inflorescence size (syconium volume) and within-plant phenology (within-tree asynchrony) as can affect inter-species relationships among the three trophic levels in such plant–herbivore–parasitoid systems. Induced or natural variations in such plant traits could influence various direct and indirect effects among the organisms in the community and could even lead to the formation of feedback cycles. Furthermore, changes in the abiotic environment could have major impacts on the biotic associations in the system either by affecting the community members directly, or through their effects on plant reproductive traits. Ficus racemosa with its fig wasp community comprised of a single herbivorous pollinator mutualist, three non-pollinating parasitic gallers and three non-pollinating parasitoids was used as a model to investigate: (1) the role of mutualistic and parasitic fig wasps in affecting within-tree phenology; (2) direct and indirect biotic associations between various groups of fig wasps (pollinators, gallers and parasitoids) and the influence of inflorescence size and within-tree phenology on them; and (3) variations in the reproduction of and the biotic associations between the organisms of the community under variable abiotic climatic conditions. Patterns of plant reproductive phenology are usually considered evolved responses directed at optimizing resource use, pollen receipt/donation schedules and seed dispersal for plant individuals. Within-plant reproductive synchrony or asynchrony can arise due to variation in floral initiation patterns, as well as from localised proximate mechanistic responses to interactants such as pollinators, parasites and herbivores which could affect floral longevity or fruit development time. The investigation was begun by exploring the role of a mutualistic pollinator, and for the first time in a brood-site mutualism, that of parasitic herbivores (gallers) and parasitoids in influencing within-plant reproductive phenology. Since a syconium functions as an inflorescence which develops into a fruit after pollination, investigations were carried out on the impact on syconium synchrony of fig wasps that began their development within the brood site syconium at pre-pollination, pollination, and post-pollination stages via their effects on the development time of individual syconia in Ficus racemosa. We found that syconium initiation patterns were not the only proximate mechanism for within-tree reproductive asynchrony, and that individual syconia (even within a tree) had highly plastic development times dependent on their sizes, pollination time and the species of wasp progeny developing within them. Syconium volume, pollination early in the pollen-receptive phase and presence of early-ovipositing galler progeny reduced syconium development time, whereas the presence of late-ovipositing parasitoid progeny or pollination late in the pollen-receptive phase increased syconium development time. These results suggest an ongoing tug-of-war between syconium inhabitants to modify syconium development times. Parasitic fig wasps pull in different directions to suit their own needs, such that final syconium development times are likely to be a compromise between conflicting demands from developing seeds and from different wasp species. Inter-species relationships among the three trophic levels in plant–herbivore–parasitoid systems can potentially include various direct and indirect effects possibly mediated by induced or natural variations in plant traits. Analysing the seed and fig wasp compositions of microcosm replicates, i.e. individual syconia, shows that besides direct competition for resources and predator–prey interactions, the F. racemosa community also displays exploitative or apparent competition and trait-mediated indirect interactions. Syconium volume and within-tree asynchrony were reproductive plant traits that not only affected plant–herbivore and plant–parasitoid associations, but also possibly modified herbivore–herbivore and herbivore–parasitoid interactions. Our results also indicated that the reciprocal effects of higher trophic level fauna on plant traits (and vice versa) within this system drive a positive feedback cycle between syconium inhabitants and within-tree reproductive asynchrony. In the F. racemosa system, abiotic environmental factors could affect the reproduction of mutualistic pollinators, non-mutualistic parasites and seed production via seasonal changes in plant reproductive traits such as syconium volume within-tree asynchrony. Temperature, relative humidity and rainfall defined four seasons: winter; hot days, cold nights; summer and wet seasons. Syconium volumes were highest in winter and lowest in summer, and affected syconium contents positively across all seasons. Greater transpiration from the nurseries was possibly responsible for smaller syconia in summer. The 3–5°C increase in mean temperatures between the cooler seasons and summer reduced fig wasp reproduction and increased seed production nearly two-fold. Yet, seed and pollinator progeny production were never negatively related in any season confirming the mutualistic fig–pollinator association across seasons. Parasites affected seed production negatively in some seasons, but had a surprisingly positive relationship with pollinators in most seasons. While within-tree reproductive phenology did not vary across seasons, its effect on syconium inhabitants varied with season. In all seasons, within-tree reproductive asynchrony affected parasite reproduction negatively, whereas it had a positive effect on pollinator reproduction in winter and a negative effect in summer. Seasonally variable syconium volumes probably caused the differential effect of within-tree reproductive phenology on pollinator reproduction. Within-tree reproductive asynchrony itself was positively affected by intra-tree variation in syconium contents and volume, creating a unique feedback loop which varied across seasons. Therefore, nursery size affected fig wasp reproduction, seed production and within-tree reproductive phenology via the feedback cycle in this system. Climatic factors affecting plant reproductive traits can cause biotic relationships between plants, mutualists and parasites to vary seasonally and must be accorded greater attention, especially in the context of climate change.