Sources of variation in herbivore preference: among-individual and past diet effects on amphipod host choice
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Understanding which factors affect the feeding preferences of herbivores is essential for predicting the effects of herbivores on plant assemblages and the evolution of plant–herbivore interactions. Most studies of marine herbivory have focussed on the plant traits that determine preferences (especially secondary metabolites), while few studies have considered how preferences may vary among individual herbivores due to genetic or environmental sources of variation. Such intraspecific variation is essential for evolutionary change in preference behaviour and may alter the outcome of plant–herbivore interactions. In an abundant marine herbivore, we determined the relative importance of among-individual and environmental effects on preferences for three host algae of varying quality. Repeated preference assays were conducted with the amphipod Peramphithoe parmerong and three of its brown algal hosts: Sargassum linearifolium, S. vestitum and Padina crassa. We found no evidence that preference varied among individuals, thus constraining the ability of natural selection to promote increased specialisation on high-quality S. linearifolium. Most of the variation in preference occurred within individuals, with amphipod preferences strongly influenced by past diet. The increased tendency for amphipods to select alternate hosts to that on which they had been recently feeding indicates that amphipods are actively seeking mixed diets. Such a feeding strategy provides an explanation for the persistence of this herbivore on hosts in the field that support poor growth and survival if consumed alone. The effects of past diet indicate that herbivore preferences are a function of herbivore history in addition to plant traits and are likely to vary with the availability of algae in space and time.
KeywordsMixed Diet Heritable Variation Diet Breadth Brooding Female Host Choice
We thank three anonymous reviewers for advice on analyses and highly constructive comments that have improved this manuscript. This research was supported by the Australian Research Council Discovery Project DP0208481. All collections were made with the permission of New South Wales Fisheries (Scientific Research Permit # P01/0047) and comply with the current laws in Australia.
- Agresti A (1996) An introduction to categorical data analysis. Wiley, New YorkGoogle Scholar
- Behmer ST, Simpson SJ, Raubenheimer D (2002) Herbivore foraging in chemically heterogeneous environments: nutrients and secondary metabolites. Ecology 83:2489–2501Google Scholar
- Bernays EA, Chapman RF (1994) Host-plant selection by phytophagous insects. Chapman & Hall, New YorkGoogle Scholar
- Bolnik DI, Yang LH, Fordyce JA, Davis JM, Svanbäck R (2002) Measuring individual-level resource specialization. Ecology 83:2936–2941Google Scholar
- Falconer DS, Mackay TFC (1996) Introduction to quantitative genetics. Longman Group Ltd, HarlowGoogle Scholar
- Hay ME, Steinberg PD (1992) The chemical ecology of plant–herbivore interactions in marine versus terrestrial communities. In: Rosenthal GA, Berenbaum M (eds) Herbivores: their interaction with secondary plant metabolites. Ecological and evolutionary processes, vol 2. Academic, San Diego, pp 371–413Google Scholar
- Paul VJ, Cruz-Rivera E, Thacker RW (2001) Chemical mediation of macroalgal-herbivore interactions: ecological and evolutionary perspectives. In: McClintock JB, Baker BJ (eds) Marine chemical ecology. CRC Press, Boca Raton, pp 227–265Google Scholar
- Poore AGB, Steinberg PD (1999) Preference–performance relationships and effects of host plant choice in an herbivorous marine amphipod. Ecol Monogr 69:443–464Google Scholar
- Roughgarden J (1979) Theory of population genetics and evolutionary ecology: an introduction. Macmillan, New YorkGoogle Scholar
- Sotka EE, Hay ME (2002) Geographic variation among herbivore populations in tolerance for a chemically rich seaweed. Ecology 83:2721–2735Google Scholar
- Szentesi A, Jermy T (1990) The role of experience in host plant choice by phytophagous insects. In: Bernays EA (ed) Insect–plant interactions, vol II. CRC Press, Boca Raton, pp 39–75Google Scholar