title: Revisiting the particular role of host shifts in initiating insect speciation.
abstract: The notion that shifts to new hosts can initiate insect speciation is more than 150 years old, yet widespread conflation with paradigms of sympatric speciation has led to confusion about how much support exists for this hypothesis. Here, we review 85 insect systems and evaluate the relationship between host shifting, reproductive isolation, and speciation. We sort insects into five categories: (1) systems in which a host shift has initiated speciation; (2) systems in which a host shift has made a contribution to speciation; (3) systems in which a host shift has caused the evolution of new reproductive isolating barriers; (4) systems with host-associated genetic differences; and (5) systems with no evidence of host-associated genetic differences. We find host-associated genetic structure in 65 systems, 43 of which show that host shifts have resulted in the evolution of new reproductive barriers. Twenty-six of the latter also support a role for host shifts in speciation, including eight studies that definitively support the hypothesis that a host shift has initiated speciation. While this review is agnostic as to the fraction of all insect speciation events to which host shifts have contributed, it clarifies that host shifts absolutely can and do initiate speciation.
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Forbes
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Sara N
authors.initials: SN
authors.lastname: Devine
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Alaine C
authors.initials: AC
authors.lastname: Hippee
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Tvedte
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Anna K G
authors.initials: AKG
authors.lastname: Ward
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Widmayer
authors.affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, 52242.
authors.forename: Caleb J
authors.initials: CJ
authors.lastname: Wilson
mesh_terms: D000818:Animals; D049810:Genetic Speciation; D007313:Insecta; D012098:Reproduction; D060047:Reproductive Isolation; D013045:Species Specificity; D061350:Sympatry
keywords: Ecological speciation; habitat isolation; immigrant inviability; plant-insect interactions; reproductive isolation; sympatric speciation