Abstract
Quantitative behavioural traits associated with egg-laying, such as the level of selectivity for host-supports and the size of egg clutches, are generally thought to be of great importance for the subsequent survival and development of offspring. These quantitative traits, however, are often difficult to assess reliably by direct observation in the field. This is particularly the case when the insects are very tiny, which is the case for most galling and leaf mining insects. However, a new approach, the Melba procedure, allows the indirect inference of these quantitative traits, using easily recorded field-data only. Application of this diagnostic procedure to a large series of samples of beech leaves (Fagus silvatica), harbouring either a leaf miner, Phyllonorycter maestingella (Lepidoptera: Gracillariidae) or one or the other of two galling insects, Mikiola fagi or Hartigiola annulipes (Diptera: Cecidomyiidae) indicates that the leaf miner differs significantly from the two species of galling insect in term of combined values of host-acceptance ratio and average clutch-size, while the two gall-inducing species remain substantially undistinguishable from each other according to these traits. Thus, the galling insects (i) show stronger selectivity for a host than does the miner at any given average clutch-size and (ii) show larger average clutch-size at any given level of selectivity. That is, for at least these three species, the galling insects show a greater level of selectivity when choosing leaves to oviposit on but, then, tend to lay larger egg-clutches. These differences may be due (i) to the gall-inducing process requiring far more of leaf tissues than being simply palatable, which makes it likely that galling species will be more selective in their choice of leaves than leaf miners and (ii) to the capacity of galls to become nutrient sinks, which may help explain why the galling insects laid larger egg clutches. However, whether these trends can be regarded as general rather specific to this particular case, depends on the outcome of future studies on other groups of insects with similar life histories.
Highlights
Optimising the survival and future success of offspring in insects arguably implies that mothers lay eggs where there are the appropriate resources for the development of their larvae (Vuorisalo et al, 1989; Thompson & Pellmyr, 1991; Réale & Roff, 1992; Awmack & Leather, 2002; Fox & Czesak, 2002; Obermaier et al, 2008; Fry et al, 2009; Morrison & Quiring, 2009; Trager et al, 2009; sometimes it is difficult to determine a clear relationship: Gripenberg et al, 2007b)
Sixty-six samples were successively analyzed using the Melba procedure in order to quantitatively evaluate the following behavioural traits: the leaf-acceptance ratio D and the average clutch size nc in term of the mines/galls that resulted from the eggs that successfully hatched
Combined distributions of the behavioural traits D and nc Considering the results for the three species taken altogether, the leaf-acceptance ratio D extends homogeneously across almost its entire possible range, from 0.05 to 1.00 and the average clutch size, nc, ranges from 1.00 to 1.38
Summary
Optimising the survival and future success of offspring in insects arguably implies that mothers lay eggs where there are the appropriate resources for the development of their larvae (Vuorisalo et al, 1989; Thompson & Pellmyr, 1991; Réale & Roff, 1992; Awmack & Leather, 2002; Fox & Czesak, 2002; Obermaier et al, 2008; Fry et al, 2009; Morrison & Quiring, 2009; Trager et al, 2009; sometimes it is difficult to determine a clear relationship: Gripenberg et al, 2007b). The likely reason for this is that, usually, the larval stage is both the least mobile and the one mainly devoted to feeding in insects. This, is especially the case when the larval stage must remain within a host or part of a host, such as (endo-) parasitoids and galling or mining insects. In galling and mining insects the larvae complete their development often within one discrete, clearly-bounded host-part, hereafter designated a “host-unit”. This may be a leaf, bud, flower, fruit or particular section of shoot of a given host-species (equivalent to individual host of similar age, belonging to the same species, in parasitoid insects)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: 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.
