Divergence in selection of host species and plant

Authors: Magne Friberg Christopher Schwind John N Thompson

Publish Date: 2016/05/05

Volume: 30, Issue: 4, Pages: 723-737

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Abstract

The diversification of phytophagous insects is often attributed to diverging processes of host plant specialization onto different often closely related host plants Some insect clades have diversified by specializing not only on different plant species but also on different plant parts of the same hosts This is the case in Greya moths Prodoxidae where both Greya obscura and G politella are tightly linked to host plants of the genus Lithophragma Saxifragaceae We assess how these species differ in their choice of plants and use of plant parts Previous work showed that strong local host specialization in G politella is mediated by floral scent variation among Lithophragma species Here we identify geographic variation in host plant use in the close relative G obscura relate the emerging patterns to previous studies of geographic variation in host use in G politella and evaluate potential processes underlying the variation among and within species First we show that G obscura also uses floral chemistry to locate hosts but that additional plant cues must be involved in deciding whether to oviposit on a plant because females did not discriminate against chemically different host species in nochoice trials We also found that although all known populations of G politella oviposit only in flowers all G obscura populations examined here distributed their eggs among both floral and scape tissues both in the field and in laboratory experiments The distribution of eggs among plant parts however varied among moth populations and also depended on the Lithophragma species they attacked Together these results show the potential for phytophagous insect species and populations to diverge in use of plant parts as part of the process of speciation and adaptation These two layers of specialization enhance the potential for subsequent diversification in phytophagous insect lineagesWe thank Kate McCurdy Sedgwick UC Reserve for hospitality and assistance Jim Velzy and the UCSC Greenhouse staff Katherine Rich Galen Pelzmann Lindsey Roark Aliya Ingersoll and Jill Piorkowski for greenhouse and field work assistance and Glenn Svensson for the olfactometer design We thank two anonymous reviewers for valuable comments on this manuscript This work was supported by the Swedish Research Council the Fulbright Commission the Royal Swedish Academy of Sciences the Crafoord Foundation and the STINT Foundation to MF and by the National Science Foundation to JNT DEB0839853

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