Evol Ecol Res 19: 195-208 (2018) Full PDF if your library subscribes.
Changes in host discrimination behaviour of Callosobruchus maculatus: shifting from habitual to ancestral hosts
Soumaya Haouel-Hamdi1, Olfa Bachrouch2, Mariam Hedjal Chebheb3, Meriem Labidi1, Ali Ouji4, Emna Boushih1 and Jouda Mediouni-Ben Jemâa1
1Laboratory of Biotechnology Applied to Agriculture, National Agricultural Research Institute of Tunisia (INRAT), University of Carthage, Tunis, Tunisia, 2Laboratory of Plant Protection, National Agricultural Research Institute of Tunisia (INRAT), University of Carthage, Tunis, Tunisia, 3Faculty of Biological and Agricultural Sciences, University Mouloud Mammeri, Tizi Ouzou, Algeria and 4Regional Centre for Research and Agricultural Development of the Semi-arid North West in El Kef, Tunisia
Correspondence: S. Haouel-Hamdi, Laboratory of Biotechnology Applied to Agriculture, National Agricultural Research Institute of Tunisia (INRAT), University of Carthage, Rue Hedi Karray, 2080 Ariana, Tunis, Tunisia. email: firstname.lastname@example.org
Background: Callosobruchus maculatus (the cowpea weevil) can cause considerable damage to important leguminous food crops. Its ancestral host is cowpea (Vigna unguiculata), but it can feed on other leguminous seeds as well. We reared a laboratory colony of C. maculatus on chickpea (Cicer arietinum) for 45 generations. The chickpea is termed the ‘habitual’ host of these weevils.
Questions: When given a choice, do C. maculatus from our laboratory colony prefer their ancestral host (cowpea), their habitual host (chickpea), or a third leguminous host (lentil, Lens culinaris) with which they are unfamiliar? If we observe a shift from chickpea back to cowpea, does it happen as soon as chickpea becomes available to the population, or does it occur gradually, generation after generation? Does it depend on the number of host choice tests weevils are confronted with? Is there a relationship between the adaptive evolution of female oviposition behaviour and larval feeding biology under free- and no-host-choice tests.
Methods: Experiment I: Allow weevils to choose freely between chickpea, cowpea, and lentils. Experiment II: Force females to use one and only one of the three weevil resources. Measure their reproductive success on each. Carry out each experiment for six generations.
Results: In the first generation, in both free- and no-host-choice tests, C. maculatus favoured the habitual host, chickpea. But, beginning with the third generation, weevils expanded what they used to include the ancestral host as well. Thus, C. maculatus can swiftly recognize and adapt to host opportunities, rapidly diversifying its host range and thereby increasing the damage it can inflict. Furthermore, results revealed that C. maculatus behaviours were greatly affected by the host-choice tests, by hosts and by generation number. Demographic traits adapted to the novel host evolved in concert with the elevation of population fitness on cowpea and lentil over the course of only three to four generations in both free- and no-host-choice tests.
Keywords: behaviour, Callosobruchus maculatus, host discrimination, host shift.
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