Plant coevolution with insects

Coevolution is defined as reciprocal stepwise adaptations between at least two species (Ehrlich and Raven, 1964). Coevolution without the criterion of reciprocity is indistinguishable from evolution and hence a useless concept (Lindroth, 1988). Consider the following scenario. A plant develops effective antiherbivore defenses. In response, a herbivore counteradapts to circumvent these defenses and is at a competitive advantage over other herbivores. The plant, in turn, responds to this breach of its defenses. In insects, such pairwise reciprocal evolution can take the form of a chemical arms race (Dawkins and Krebs, 1979). Coevolution differs from evolution by being narrower, with fewer participants, perhaps even only two species or two populations. In reality, in most ecosystems, many species prey on many other species. Therefore, we can at best speak of diffuse coevolution, with a number of participants that exert diluted selection pressures. 

Life in the oceans differs in most respects from life on land. The most remarkable observation is that the oceans are poorer in species but richer in phyla with respect to land (Chapter 1.2). This finds no easy answer, however. Perhaps the reason for the larger number of species on land lies in a wider diversification of habitat and climate than in the sea, which required a great deal of adaptation, accompanied by speciation. In these affairs, coevolution of plants with insects was a major trigger of biodiversity. 

Rothschild, M., Carotenoids in the evolution of signals. Experiments with insects (1974-1976), in Biochemical Aspects of Plant and Animal Coevolution (J. B. Harborne, ed.), 259-276, Academic Press, New York, 1978. 

I will extend this argument to encompass the diversification of such systems in lineages of plants in an effort to correlate enzyme-mediated glycoside toxicity with the evolution of host plant specificity and the coevolution of plants and insects. 

The coevolution of plants with the bacteria, fungi, insects, nematodes, viruses, and others that attack them has led to... 

Evans HC. Co-evolution of entomogenous fungi and their insect hosts. In Pirozynski KA, Hawksworth DL, eds. Coevolution of Fungi with Plants and Animals. London, New York Academic Press, 1988, pp 149-171. 

The coevolution of plants and insects, birds and bats with respect to the pollination of flowers gave rise to the formation of special morphological features and chemical characteristics. The main reason why pollinators visit flowers is to gather nectar and pollen as nutrients which contain carbohydrates, fats, and proteins. With respect to secondary products... 

The other aspects of resistance, the unpalatability of the plant for the vector, will be dealt with in the next section of this chapter, together with further evidence for plant-insect coevolution. 

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