This interaction confers benefits on both the interacting species. Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising algae or cyanobacteria. Similarly, the mycorrhizae are associations between fungi and the roots of higher plants. The fungi help the plant in the absorption of essential nutrients from the soil while the plant in turn provides the fungi with energy-yielding carbohydrates. The most spectacular and evolutionarily fascinating examples of mutualism are found in plant-animal relationships. Plants need the help of animals for pollinating their flowers and dispersing their seeds. Animals obviously have to be paid ‘fees’ for the services that plants expect from them. Plants offer rewards or fees in the form of pollen and nectar for pollinators and juicy and nutritious fruits for seed dispersers. But the mutually beneficial system should also be safeguarded against ‘cheaters’, for example, animals that try to steal nectar without aiding in pollination. Now you can see why plant-animal interactions often involve co-evolution of the mutualists, that is, the evolutions of the flower and its pollinator species are tightly linked with one another. In many species of fig trees, there is a tight one-to-one relationship with the pollinator species of wasp . It means that a given fig species can be pollinated only by its ‘partner’ wasp species and no other species. The female wasp uses the fruit not only as an oviposition (egg-laying) site but uses the developing seeds within the fruit for nourishing its larvae. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites. In return for the favour ofpollination the fig offers the wasp some of its developingseeds, as food for the developing wasp larvae.Orchids show a bewildering diversity of floralpatterns many of which have evolved to attract the rightpollinator insect (bees and bumblebees) and ensureguaranteed pollination by it. Not allorchids offer rewards. The Mediterranean orchid Ophrysemploys ‘sexual deceit’ to get pollination done by aspecies of bee. One petal of its flower bears an uncannyresemblance to the female of the bee in size, colour andmarkings. The male bee is attracted to what it perceivesas a female, ‘pseudocopulates’ with the flower, andduring that process is dusted with pollen from theflower. When this same bee ‘pseudocopulates’ withanother flower, it transfers pollen to it and thus,pollinates the flower. Here you can see how co-evolutionoperates. If the female bee’s colour patterns change evenslightly for any reason during evolution, pollination success will be reducedunless the orchid flower co-evolves to maintain the resemblance of itspetal to the female bee.
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