Integrating ancient patterns and current dynamics of insect–plant interactions: Taxonomic and geographic variation in herbivore specialization

Abstract

The search for pattern in the ecology and evolutionary biology of insect–plant associations has fascinated biologists for centuries. High levels of tropical (low‐latitude) plant and insect diversity relative to poleward latitudes and the disproportionate abundance of host‐specialized insect herbivores have been noted. This review addresses several aspects of local insect specialization, host use abilities (and loss of these abilities with specialization), host‐associated evolutionary divergence, and ecological (including “hybrid”) speciation, with special reference to the generation of biodiversity and the geographic and taxonomic identification of “species borders” for swallowtail butterflies (Papilionidae). From ancient phytochemically defined angiosperm affiliations that trace back millions of years to recent and very local specialized populations, the Papilionidae (swallowtail butterflies) have provided a model for enhanced understanding of localized ecological patterns and genetically based evolutionary processes. They have served as a useful group for evaluating the feeding specialization/physiological efficiency hypothesis. They have shown how the abiotic (thermal) environment interacts with host nutrirional suitability to generate “voltinism/suitability” gradients in specialization or preference latitudinally, and geographical mosaics locally. Several studies reviewed here suggest strongly that the oscillation hypothesis for speciation does have considerable merit, but at the same time, some species‐level host specializations may lead to evolutionary dead‐ends, especially with rapid environmental/habitat changes involving their host plants. Latitudinal gradients in species richness and degree of herbivore feeding specialization have been impacted by recent developments in ecological genetics and evolutionary ecology. Localized insect–plant associations that span the biospectrum from polyphenisms, polymorphisms, biotypes, demes, host races, to cryptic species, remain academically contentious, with simple definitions still debated. However, molecular analyses combined with ecological, ethological and physiological studies, have already begun to unveil some answers for many important ecological/evolutionary questions.

Butterfly proboscis: combining a drinking straw with a nanosponge facilitated diversification of feeding habits

“…Most explanatory models of lepidopteran biodiversification focus on the larva-foodplant interface [21]. The possible role of the proboscis in facilitating the adaptive radiation of butterflies and moths, such as the exclusively fruit-feeding butterflies [12], has received scant attention.…”

Revisiting the evolution of ecological specialization, with emphasis on insect–plant interactions

“…In the intervening two decades, empirical and theoretical work on specialization has flourished (Schluter 2000, Ravigne´et al 2009, Scriber 2010. Developments have been sufficient in volume and importance that we find it opportune to review and synthesize the field.…”

Oviposition strategy as a means of local adaptation to plant defence in native and invasive populations of the viburnum leaf beetle

“…Because plants vary tremendously in their defensive arsenal among species [1] and populations [2], herbivores may encounter geographically heterogeneous mosaics of plant defences and their offence traits are predicted to exhibit local adaptation [3][4][5][6]. Despite this widespread notion, relatively little data exist on local adaptation of insects to specific defence traits [7,8].…”