Decoupling of female host plant preference and offspring performance in relative specialist and generalist butterflies

Abstract

The preference-performance hypothesis posits that the host plant range of plant-feeding insects is ultimately limited by larval costs associated with feeding on multiple resources, and that female egg-laying preferences evolve in response to these costs. The trade-off of either using few host plant species and being a strong competitor on them due to effective utilization or using a wide host plant range but being a poor competitor is further predicted to result in host plant specialization. This follows under the hypothesis that both females and offspring are ultimately favoured by utilizing only the most suitable host(s). We develop an experimental approach to identify such trade-offs, i.e. larval costs associated with being a host generalist, and apply a suite of experiments to two sympatric and syntopic populations of the closely related butterflies Pieris napi and Pieris rapae. These butterflies show variation in their level of host specialization, which allowed comparisons between more and less specialized species and between families within species. Our results show that, first, the link between female host preference and offspring performance was not significantly stronger in the specialist compared to the generalist species. Second, the offspring of the host plant specialist did not outperform the offspring of the generalist on the former's most preferred host plant species. Finally, the more generalized species, or families within species, did not show higher survival or consistently higher growth rates than the specialists on the less preferred plants. Thus, the preference and performance traits appear to evolve as largely separated units.

Female fecundity variation affects reproducibility of experiments on host plant preference and acceptance in a phytophagous insect

“…We compared female host use of the three host plants B. vulgaris (winter cress), B. napus (rapeseed) and A. rusticana (horseradish). All these plants are highly suitable for larval growth [38]. Across experiments, we tried to minimize effects of phenological state or genetic variation in the host plants, by continuously growing new plants of the same seed/ root stock, and picking leaves of the same physiological stature, size and freshness.…”

“…Pieris butterflies (Pieridae) are suitable targets for these kinds of experiment, because a previous study on P. napi found variation in host plant acceptance among females of the same Swedish population of P. napi [38]. Whereas all females readily laid eggs on Barbarea vulgaris, about half of the females tested refused certain hosts in long-term nochoice trials (e.g.…”

“…Whereas all females readily laid eggs on Barbarea vulgaris, about half of the females tested refused certain hosts in long-term nochoice trials (e.g. Armoracia rusticana or Brassica napus) [38]. Investigating the basis of this variation is of interest as a route to uncovering the genetic basis of host plant choice.…”

Host associations of Coenonympha hero (Lepidoptera: Nymphalidae) in northern Europe: microhabitat rather than plant species

“…In particular, in enclosures with multiple plant species, eggs may be laid on non-host plants due to the confounding effect of the proximity of higher ranked hosts while one substrate designs are free of this problem. In such experiments, the number of eggs laid during a certain (short) period of time is a measure of host acceptability Tammaru 2004, 2006;Gamberale-Stille et al 2014;Friberg et al 2015).…”

Divergent host plant utilization by adults and offspring is related to intra‐plant variation in chemical defences

“…Maternal choice can vary between herbivore species and populations, where some may select either optimal or suboptimal diet choices for their offspring (Clark, Hartley, & Johnson, ; Friberg, Posledovich, & Wiklund, ; Garcia‐Robledo & Horvitz, ; Gripenberg, Mayhew, Parnell, & Roslin, ; Handley, Ekbom, & Ågren, ; Hufnagel, Schilmiller, Ali, & Szendrei, ). Alternatively, the inverse has been observed, where host plant dietary constraints on adults impacted reproduction and fitness, yet did not completely extend to negative impacts on brood performance (Lee et al, ; Scheirs, Bruyn, & Verhagen, ; Scheirs et al, ; Smith, Johnson, Davidowitz, & Bronstein, ).…”