A new brood-pollination mutualism between Stellera chamaejasme and flower thrips Frankliniella intonsa

Background Brood pollination mutualism is a special type of plant-pollinator interaction in which adult insects pollinate plants, and the plants provide breeding sites for the insects as a reward. To manifest such a mutualism between Stellera chamaejasme and flower thrips of Frankliniella intonsa, the study tested the mutualistic association of the thrips life cycle with the plant flowering phenology and determined the pollination effectiveness of adult thrips and their relative contribution to the host’s fitness by experimental pollinator manipulation. Results The adult thrips of F. intonsa, along with some long-tongue Lepidoptera, could serve as efficient pollinators of the host S. chamaejasme. The thrips preferentially foraged half-flowering inflorescences of the plants and oviposited in floral tubes. The floral longevity was 11.8 ± 0.55 (mean ± se) days, which might precisely accommodate the thrips life cycle from spawning to prepupation. The exclusion of adult thrips from foraging flowers led to a significant decrease in the fitness (i.e., seed set) of host plants, with a corresponding reduction in thrips fecundity (i.e., larva no.) in the flowers. Conclusions The thrips of F. intonsa and the host S. chamaejasme mutualistically interact to contribute to each other’s fitness such that the thrips pollinate host plants and, as a reward, the plants provide the insects with brooding sites and food, indicating the coevolution of the thrips life cycle and the reproductive traits (e.g., floral longevity and morphology) of S. chamaejasme.

Testing for apomixis in an obligate pollination mutualism

Plants with a small number of specific pollinators may be vulnerable to fluctuations in the availability of those pollinators, which could limit plant reproductive success and even result in extinction. Plants can develop mechanisms to mitigate this risk, such as apomixis. Reproductive assurance mechanisms have been largely ignored in obligate pollination mutualisms (OPMs), that are some of the most specialised of plant-pollinator interactions. Furthermore, although OPMs are often referred to as obligate, this is rarely tested. We performed a flower-bagging experiment to test if the unisexual flowers of Breynia oblongifolia could set fruit in the absence of its highly specialised seed-eating moth pollinators. Surprisingly, many bagged female flowers developed fruits, suggesting apomixis. We therefore conducted a second series of experiments in which we 1) added or excluded pollinators from caged plants; and 2) surveyed a wild population for apomictic reproduction using mother-offspring genotyping. In the absence of pollinators, no fruits developed. In addition, we detected no genetic evidence for apomixis when comparing between mothers and their offspring or between adults in a wild population. We explain the production of fruits in bagged branches by our discovery that B. oblongifolia can retain pollinated female flowers over the winter period. These flowers develop to fruits in the spring in the absence of male flowers or pollinators. Our study thus shows that B. oblongifolia is unable to produce fruit in the absence of its specialist moth pollinators. Thus, the highly specific interaction between plant and pollinators appears to be truly obligate.

Plants Are the Drivers of Geographic Variation of Floral Scents in a Highly Specialized Pollination Mutualism: a Study of Ficus Hirta in China

BackgroundFloral volatiles play an important role in pollinator attraction. This is particularly true in obligate brood site pollination mutualisms. The plants generally produce inconspicuous flowers and depend on odours to attract to their inflorescences specialised pollinators that breed in their floral structures. Little is known about the processes shaping the micro-evolution of these floral odours. Here, we investigate geographic variation of floral odour in an obligate host-specific brood site pollination mutualism where plant and pollinator genetic structures are different, Ficus hirta and its specialised pollinators.ResultsWe evidence progressive geographic divergence of floral odours. The pattern of variation fits plant genetic structure but differs from pollinating insect structuring into species and populations. In our study system, the evolution of receptive floral odour presents a pattern that is not distinguishable from neutral drift that is not canalised by the insects.ConclusionWe propose that this pattern characterises obligate brood site pollination mutualisms in which pollinators are host specific and dispersal is limited. Insects with their short generation times and large population sizes track variation in host receptive inflorescence odours. Plants are the drivers and insects the followers. Strict sense plant-insect co-evolution is not involved. In contrast, stabilizing selection may be at work in more dispersive brood site pollination mutualisms, while pollinators may mediate local interspecific plant floral odour convergence when plant species share local pollinators.

Genomic evidence of prevalent hybridization throughout the evolutionary history of the fig-wasp pollination mutualism

Ficus (figs) and their agaonid wasp pollinators present an ecologically important mutualism that also provides a rich comparative system for studying functional co-diversification throughout its coevolutionary history (~75 million years). We obtained entire nuclear, mitochondrial, and chloroplast genomes for 15 species representing all major clades of Ficus. Multiple analyses of these genomic data suggest that hybridization events have occurred throughout Ficus evolutionary history. Furthermore, cophylogenetic reconciliation analyses detect significant incongruence among all nuclear, chloroplast, and mitochondrial-based phylogenies, none of which correspond with any published phylogenies of the associated pollinator wasps. These findings are most consistent with frequent host-switching by the pollinators, leading to fig hybridization, even between distantly related clades. Here, we suggest that these pollinator host-switches and fig hybridization events are a dominant feature of fig/wasp coevolutionary history, and by generating novel genomic combinations in the figs have likely contributed to the remarkable diversity exhibited by this mutualism.

Behaviors and Interactions of Insects in Mid-Mesozoic Ecosystems of Northeastern China

During the past 20 years, more than 1,600 species of well-preserved fossil insects, including members of over 270 families within 24 orders, have been described from the Middle Jurassic Yanliao Entomofauna and Early Cretaceous Jehol Entomofauna in Northeastern China. Diversified fossil insects not only document the origin, systematics, and early evolution of many lineages, but also reveal these lineages’ behaviors and interactions with coexisting plants, vertebrates, and other insects in their ecosystems. Fossil evidence has been documented, for example, regarding insects’ feeding and pollination mutualism with gymnosperms; ectoparasitic feeding on blood of vertebrates; camouflage, mimicry of gymnosperm plants, and eyespot warning; sound stridulation for attracting potential mates; and sexual display, mating, egg-laying, and parental care. In this article, we review the diverse taxonomy of mid-Mesozoic insects of Northeastern China and elucidate their behaviors and interactions within their ecosystems, which have impacted their early evolution and development into extant insects.

Reduced Water Negatively Impacts Social Bee Survival and Productivity Via Shifts in Floral Nutrition

Pollinators provide a key ecosystem service vital for the survival and stability of the biosphere. Identifying factors influencing the plant–pollinator mutualism and pollinator management is necessary for maintaining a healthy ecosystem. Since healthy beehives require substantial amounts of carbohydrates (nectar) and protein (pollen) from forage plants such as clover, we must assess how resources offered by plants change under limited water conditions in order to fully understand how drought modifies the pollination mutualism. Here we document how reduced water availability leads to decreased nectar quality and quantity and decreased protein quality of pollen. Furthermore, we provide conclusive evidence that these lower quality resources lead to decreased survival and productivity in both developing honey bees (Hymenoptera: Apidae) and bumble bees (Hymenoptera: Apidae). The results emphasize the importance of the nutritional effects of reduced water on bees when predicting shifts of pollination mutualisms under climate change.