The evolvability of arthropods

Abstract

By many metrics, arthropods constitute one of the most successful animal phyla on our planet, manifest in extreme species richness, enormous diversity in morphologies and developmental modes, and successful radiation into nearly every inhabitable ecological niche available to multicellular organisms (Storch and Welch 1991; Brusca and Brusca 2000; Odegaard 2000; Valentine 2004; Gullan and Cranston 2004; Grimaldi and Engel 2005). In this chapter, we will explore some of the causes and mechanisms that have enabled arthropod diversification. We define evolvability broadly as a lineage's capacity to generate phenotypic diversity over evolutionary time. We begin by exploring two prominent axes of diversification in the arthropods: evolvability in (1) developmental space and in (2) developmental time, and their respective contributions to facilitating innovation, diversification, and radiation within the Arthropoda. We end our chapter by examining the role of (3) developmental plasticity in arthropod evolution. In each context, we explore the genetic, developmental, and ecological mechanisms that may have allowed arthropods to diversify more than any other group of animals, the interactions among these mechanisms, and the emergent properties of these interactions. Throughout, we highlight key questions for future research, in particular as created by the increased integration of evolution and ecology with developmental biology and genomics.