Geographical variation in host plant utilization in the comma butterfly: the roles of time constraints and plant phenology (original) (raw)
Related papers
Host plant utilization in the comma butterfly: sources of variation and evolutionary implications
Oecologia, 1994
A major challenge in the study of insect-host plant interactions is to understand how the different aspects of offspring performance interact to produce a preference hierarchy in the ovipositing females. In this paper we investigate host plant preference of the polyphagous butterfly Polygonia c-album (Lepidoptera: Nymphalidae) and compare it with several aspects of the life history of its offspring (growth rate, development time, adult size, survival and female fecundity). Females and offspring were tested on four naturally used host plants (Urtica dioica, Ulmus glabra, Salix caprea, and Betula pubescens). There was substantial individual variation in host plant preference, including reversals in rank order, but the differences were largely confined to differences in the ranking of Urtica dioica and S. caprea. Different aspects of performance on these two plants gave conflicting and complementary results, implying a trade-off between short development time on U dioica, and larger size and higher fecundity on S. caprea. As all performance components showed low individual variation the large variation in host plant preference was interpreted as due to alternative oviposition strategies on the basis of similar 'performance hierarchies'. This indicates that the larval performance component of host-plant utilization may be more conservative to evolutionary change than the preference of ovipositing females. Possible macro-evolutionary implications of this are discussed.
Biological Journal of The Linnean Society, 2016
An insect species that shows variation in host species association across its geographical range may do so either because of local adaptation in host plant preference of the insect or through environmentally or genetically induced differences in the plants, causing variation in host plant suitability between regions. In the present study, we experimentally investigate the host plant preference of Anthocharis cardamines (orange tip butterfly) in two populations from the UK and two from Sweden. Previous reports indicate that A. cardamines larvae are found on different host plant species in different regions of the UK, and some variation has been reported in Sweden. Host plant choice trials showed that females prefer to oviposit on plants in an earlier phenological stage, as well as on larger plants. When controlling for plant phenological stage and size, the host species had no statistically significant effect on the choice of the females. Moreover, there were no differences in host plant species preference among the four butterfly populations. Based on our experiment, the oviposition choice by A. cardamines mainly depends on the phenological stage and the size of the host plant. This finding supports the idea that the geographical patterns of host-plant association of A. cardamines in the UK and Sweden are consequences of the phenology and availability of the local hosts, rather than regional genetic differences in the host species preference of the butterfly.
Biological Journal of the Linnean Society, 2005
In the Lepidoptera, sex-linked genes have been found to be of importance for species differences in, for example, hostplant preference, and have been implicated in ecological speciation. Variation within species is typically not sexlinked. However, in the comma butterfly Polygonia c-album (Nymphalidae) an X-linked gene has been found to play a major role in determining differences in host-plant use between two well separated populations. For this reason, we studied the role of sex-linked genes for host-plant preference within a single Swedish population of this species. Three generations of females with known pedigrees were studied in the laboratory, and they were given a choice between Urtica dioica and Salix caprea in flight cages. We found strong variation among females and significant genetic variance for host-plant preference, but no evidence for major importance of sex linkage of host-plant preference on this local scale. To what extent the observed genetic variation was due to additive genes and/or effects of major genes was not clear from the maximum likelihood analysis. In a follow-up study we sampled females over a larger area. We found strong variation among females, but not among localities, suggesting an open population structure with strong gene flow. From the combined stock, a selection experiment was performed over 2 years and six generations. The selection lines diverged after the first generation of selection and remained separate, but did not diverge further, suggesting a low degree of narrow-sense heritability and that the genetic differences may be effects of major genes. We discuss these results in relation to the possible role of genetics in the radiation of the Lepidoptera and other phytophagous insects.
Butterfly host plant choice in the face of possible confusion
Journal of Insect Behavior, 2000
We tested predictions from the theory that ovipositing females of phytophagous insects are limited by their neural capacity for information processing. Previous studies have found that relatively specialized insects make faster and/or more accurate identifications of host plants compared to generalists. The study species was the polyphagous comma butterfly, Polygonia c-album (Nymphalidae). We compared females originating from two populations (Sweden and England) which differ in degree of specialization on the preferred host Urtica dioica (Urticaceae). Females were given a choice between this plant and a very similar nonhost, white dead nettle, Laminum album (Lamiacease), or a choice between a relatively poor host, Betuala pubescens, and the nonhost Betula pendula (Betulaceae). Oviposition rate was lower in cages with Betula compared to cages with Urtica, demonstrating that P. c-album females will withhold eggs when preferred hosts are not available. As predicted, females originating from the Swedish generalist population oviposited more often on the nonhost Lamium. However, females of both populations discriminated very strongly against oviposition on B. pendula. We found that newly hatched larvae have some ability to move from herbaceous nonhost to hosts. Although alternative interpretations are possible, the results give further support to the hypothesis that there are trade-offs between diet breadth and the ability to discriminate among plants.
Insect Science, 2013
In most phytophagous insects, the larval diet strongly affects future fitness and in species that do not feed on plant parts as adults, larval diet is the main source of nitrogen. In many of these insect-host plant systems, the immature larvae are considered to be fully dependent on the choice of the mothers, who, in turn, possess a highly developed host recognition system. This circumstance allows for a potential mother-offspring conflict, resulting in the female maximizing her fecundity at the expense of larval performance on suboptimal hosts. In two experiments, we aimed to investigate this relationship in the polyphagous comma butterfly, Polygonia c-album, by comparing the relative acceptance of low-and medium-ranked hosts between females and neonate larvae both within individuals between life stages, and between mothers and their offspring. The study shows a variation between females in oviposition acceptance of low-ranked hosts, and that the degree of acceptance in the mothers correlates with the probability of acceptance of the same host in the larvae. We also found a negative relationship between stages within individuals as there was a higher acceptance of lower ranked hosts in females who had abandoned said host as a larva. Notably, however, neonate larvae of the comma butterfly did not unconditionally accept to feed from the least favorable host species even when it was the only food source. Our results suggest the possibility that the disadvantages associated with a generalist oviposition strategy can be decreased by larval participation in host plant choice.
Oecologia, 2009
A large proportion of phytophagous insect species are specialised on one or a few host plants, and female host plant preference is predicted to be tightly linked to high larval survival and performance on the preferred plant(s). Specialisation is likely favoured by selection under stable circumstances, since different host plant species are likely to differ in suitability-a pattern usually explained by the ''trade-off hypothesis'', which posits that increased performance on a given plant comes at a cost of decreased performance on other plants. Host plant specialisation is also ascribed an important role in host shift speciation, where different incipient species specialise on different host plants. Hence, it is important to determine the role of host plants when studying species divergence and niche partitioning between closely related species, such as the butterfly species pair Leptidea sinapis and Leptidea reali. In Sweden, Leptidea sinapis is a habitat generalist, appearing in both forests and meadows, whereas Leptidea reali is specialised on meadows. Here, we study the female preference and larval survival and performance in terms of growth rate, pupal weight and development time on the seven mostutilised host plants. Both species showed similar host plant rank orders, and larvae survived and performed equally well on most plants with the exceptions of two rarely utilised forest plants. We therefore conclude that differences in preference or performance on plants from the two habitats do not drive, or maintain, niche separation, and we argue that the results of this study do not support the trade-off hypothesis for host plant specialisation, since the host plant generalist Leptidea sinapis survived and performed as well on the most preferred meadow host plant Lathyrus pratensis as did Leptidea reali although the generalist species also includes other plants in its host range.
Ecology, 2009
The majority of phytophagous insects are relatively specialized in their food habits, and specialization in resource use is expected to be favored by selection in most scenarios. Ecological generalization is less common and less well understood, but it should be selected for by (1) rarity of resources, (2) resource inconstancy, or (3) unreliability of resource quality. Here, we test these predictions by studying egg distribution and offspring survival in the orange tip butterfly, Anthocharis cardamines, on different host plants in Sweden over a fiveyear period. A total of 3800 eggs were laid on 16 of the 18 crucifers available at the field site during the five years. Three main factors explained host plant generalization: (1) a rarity of food resources in which the female encounter rate of individual crucifer plants was low and within-year phenological succession of flowering periods of the different crucifers meant that individual species were suitable for oviposition only within a short time window, which translates to a low effective abundance of individual crucifer species as experienced by females searching for host plants, making specialization on a single crucifer species unprofitable; (2) variation in food resources in which among-year variation in availability of any one host plant species was high; and (3) larval survivorship varied unpredictably among years on all host plants, thereby necessitating a bet-hedging strategy and use of several different host plants. Unpredictable larval survival was caused by variation in plant stand habitat characteristics, which meant that drowning and death from starvation affected different crucifers differently, and by parasitism, which varied by host plant and year. Hence, our findings are in agreement with the theoretical explanation of ecological generalization above, helping to explain why A. cardamines is a generalist throughout its range with respect to genera within the Cruciferae.