Adaptive radiation and insects

Abstract

The fundamental aspect of principle of divergence has emerged in different spheres of evolutionary biology as propounded by Charles Darwin. Adaptive radiation is an aspect of evolutionary biology encompassing microevolution and macroevolution, explaining the principles of divergence, taking into account the theories of natural selection and struggle for life. In addition to the classical example of Darwin's finches in the Galapagos Islands, there are many others, of which the phytophagous insects are a prominent one that could be examined in detail to explain the different paradigms of adaptive radiation. With this example the evolutionary process of natural selection can be explained in its totality when one ancestral species gives rise to two or more species with different kinds of feeding characteristics and other core biological phenomena. There are many criteria that can be adopted to establish that adaptive radiation has taken place and all these focus toward aspects of microevolution and macroevolution. Many times the ecological, reproductive, stratigraphic, barriers due to abiotic factors are the ones that are focused toward establishing the facts on adaptive radiation. There are evidences that pluralistic diversity in insects and their species, genetic and ecological diversity is mainly due to successful adaptive radiation. The macroevolutionary patterns on insect host plant evolution are enormously varied due to the special features of wings and metamorphosis in addition to characteristics of migration and dispersal. The inordinate fondness for beetles and other phytophagous insects exhibited by nature and discussed in detail is mainly due to adaptive radiation as explicit through sister group analysis done in the large insect groups. It is also established that the evolutionary rates in these insect groups are much enormous as exhibited by the Chrysomeloidea and Curculionoidea. There are examples like the cotton stem weevil, other gall-inducing Coleopterans and other insects wherein the coevolution on the insect plant surface had been brought out and integrated with molecular phylogenetic studies to establish the bridge between microevolution and macroevolution as envisioned by Charles Darwin. These are shedding light on the underlying causes of the patterns of diversification in phytophagous insects. It is very clear that such efforts are providing the ultimate appraisal of Darwin's bridge between microevolution and macroevolution as components of adequate radiation. All these finally testify that the treatise 'On the Origin of Species' by Darwin is a living document that contains wealth of ideas, which if subjected to modern synthesis and innovative appraisal can provide multiple answers to many intriguing questions in evolutionary biology, especially those relating to 'inordinate fondness for beetles' and the adaptive radiation in the phytophagous insects.