Recent experiments and simulations are starting to answer some fundamental questions about how life came to be.
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Edited by Rodolfo Dirzo, Stanford University, Stanford, CA, and approved July 7, 2017 (received for review April 17, 2017)
Significance
Understanding what morphological and behavioral traits promote the success of diverse groups of organisms is a major goal of evolutionary biology. The ability to consume novel food sources has been linked to the spectacular radiation of herbivorous insects that eat terrestrial plants on Earth. Among the crustaceans, the arthropod group that dominates aquatic environments, relatively few major taxa have overcome the challenges of consuming primary producers (plants and macroalgae). However, lineages that include plant material in their diets support more species than their most closely related lineages. The results of our analyses support the hypothesis that a shift in diet promotes speciation in this diverse and ecologically important animal group.
Abstract
About half of the world’s animal species are arthropods associated with plants, and the ability to consume plant material has been proposed to be an important trait associated with the spectacular diversification of terrestrial insects. We review the phylogenetic distribution of plant feeding in the Crustacea, the other major group of arthropods that commonly consume plants, to estimate how often plant feeding has arisen and to test whether this dietary transition is associated with higher species numbers in extant clades. We present evidence that at least 31 lineages of marine, freshwater, and terrestrial crustaceans (including 64 families and 185 genera) have independently overcome the challenges of consuming plant material. These plant-feeding clades are, on average, 21-fold more speciose than their sister taxa, indicating that a shift in diet is associated with increased net rates of diversification. In contrast to herbivorous insects, most crustaceans have very broad diets, and the increased richness of taxa that include plants in their diet likely results from access to a novel resource base rather than host-associated divergence.
Footnotes
- ↵1To whom correspondence should be addressed. Email: a.poore{at}unsw.edu.au.
Author contributions: A.G.B.P., S.T.A., J.K.L., and E.E.S. designed research; A.G.B.P., S.T.A., J.K.L., and E.E.S. performed research; A.G.B.P. and E.E.S. analyzed data; and A.G.B.P., S.T.A., and E.E.S. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1706399114/-/DCSupplemental.
Herbivory promotes crustacean diversification
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