Abstract
Determinants of the host ranges of insect herbivores are important from an evolutionary perspective and also have implications for applications such as biological control. Although insect herbivore host ranges typically are phylogenetically constrained, herbivore preference and performance ultimately are determined by plant traits, including plant secondary metabolites. Where such traits are phylogenetically labile, insect hervivore host ranges are expected to be phylogenetically disjunct, reflecting phenotypic similarities rather than genetic relatedness among potential hosts. We tested this hypothesis in the laboratory with a Brassicaceae-specialized weevil, Ceutorhynchus cardariae Korotyaev (Coleoptera: Curculionidae), on 13 test plant species differing in their suitability as hosts for the weevil. We compared the associations between feeding by C. cardariae and either phenotypic similarity (secondary chemistry—glucosinolate profile) or genetic similarity (sequence of the chloroplast gene ndhF) using two methods—simple correlations or strengths of association between feeding by each species, and dendrograms based on either glucosinolates or ndhF sequence (i.e., a phylogram). For comparison, we performed a similar test with the oligophagous Plutella xylostella (L.) (Lepidoptera: Plutellidae) using the same plant species. We found using either method that phenotypic similarity was more strongly associated with feeding intensity by C. cardariae than genetic similarity. In contrast, neither genetic nor phenotypic similarity was significantly associated with feeding intensity on the test species by P. xylostella. The result indicates that phenotypic traits can be more reliable indicators of the feeding preference of a specialist than phylogenetic relatedness of its potential hosts. This has implications for the evolution and maintenance of host ranges and host specialization in phytophagous insects. It also has implications for identifying plant species at risk of nontarget attack by potential weed biological control agents and hence the approach to prerelease testing.
Highlights
Phylogenetic constraints are evident in the host range of many specialized organisms, including plant pathogens (Gilbert & Webb, 2007), parasitic Hymenoptera (Desneux et al, 2012), and insect herbivores (Bernays & Chapman, 1994)
Feeding punctures by C. cardariae differed among the 13 species tested in bioassays (χ2 = 45.7; P < 0.0001) with greatest feeding occurring on L. draba followed by feeding on the closely related European L. campestre and the North American D. nemorosa (Table 3)
The host ranges of insect herbivores generally are phylogenetically constrained (Bernays & Chapman, 1994; Rasmann & Agrawal, 2011), some species have phylogenetically disjunct host ranges that include plant species more distantly related to a primary host but exclude some that are more closely related (Hinz & Diaconu, 2015; Weiblen et al, 2006)
Summary
Phylogenetic constraints are evident in the host range of many specialized organisms, including plant pathogens (Gilbert & Webb, 2007), parasitic Hymenoptera (Desneux et al, 2012), and insect herbivores (Bernays & Chapman, 1994) These patterns likely reflect the morphological and biochemical similarities among closely related potential host species (Krasnov et al, 2004; Poulin, 2005), accounting for phylogenetic associations between lineages of insect herbivores and plant families with distinct chemical defenses (Ehrlich & Raven, 1964), and host ranges of individual insect species among their potential hosts. Individual compounds within a class can have divergent effects on herbivores (Agrawal et al, 2011; Hopkins, Van Dam & Van Loon, 2009; Liu, Klinkhamer & Vrieling, 2017), potentially accounting for disjunct host ranges of individual herbivore species
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.