Abstract
In natural systems plant-insect interactions are influenced by several factors. For instance plants could be characterised by the presence of defensive chemicals and herbivores are forced to evolve resistance against them. There are several studies on induced plant defence, which indicate it can mediate competition between herbivorous insects, shaping host plant choice and community structure. Therefore, realized host plant use can be much narrower than the potential one. A laboratory experiment was done to clear up the possible difference in host plant utilization ability of Melitaea phoebe and Melitaea ornata, especially their utilization of Cirsium pannonicum. The caterpillars were reared individually on three different species of host plant (Ci. pannonicum, Ci. arvense and Centaurea scabiosa). The weights of the larvae were measured every second day and the data analysed using ANOVA. M. phoebe caterpillars developed well and all pupated when fed on Cirsium arvense and Centaurea scabiosa, whereas those fed on Cirsium pannonicum developed poorly and 10% died. In contrast, M. ornata developed well on Ci. pannonicum and the other two host plants. Despite this M. ornata was only found on Ci. pannonicum in Hungary.
Highlights
In natural systems plant-insect interactions are influenced by several factors
The results show that M. ornata occurs in higher numbers only in those habitats where its only known food plant (Cirsium pannonicum) is abundant, despite the fact that there are several Asteraceae (Carduus sp., Centaurea sp.) there that are used as food plants in the Mediterranean area
The aim of the study was to clear up the possible difference in host plant utilization ability of Melitaea phoebe and Melitaea ornata, especially that of Cirsium pannonicum
Summary
Many plants are characterised by the presence of defensive chemicals (Ehrlich & Raven, 1964; Häggström & Larsson, 1995; Dobler et al, 1996; Monique, 2001; Wahlberg, 2001) These substances form part of the plant’s defence system and affect herbivores in different ways, e.g. they can attract predators or parasitoids of herbivores (Vet & Dicke, 1992), as well as having direct effects, which may be toxic, anti-digestive, anti-nutritive and deterrent (Bernays & Graham, 1988; Jaenike, 1990; Wittstock & Gershenzon, 2002; Kessler & Halitschke, 2007). When a novel detoxifying mechanism arises, it will open up a new array of potential host plants, consisting of all those that produce the less harmful chemical These food plants constitute a biochemical group, but need not be related phylogenetically as unrelated plants can have the same defensive chemicals. It follows that herbivores are often not adapted to a single plant species but to a particular type of secondary metabolite, as is the case in Blepharida beetles (Becerra, 1997) and pierid butterflies (Wheat et al, 2007)
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