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- Pettersson, Viktoria, 1976-, et al.
(författare)
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Male and female resposes to florivory in the perennial herb Silene dioica
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In dioecious species the two sexes differ in amount and timing of allocation to reproduction and as a consequence we would expect different sex specific responses to equal losses to herbivory. We studied the response of Silene dioica male and female plants to herbivory of two specialist insect herbivores Caryocolum viscariella and Delia criniventris that share the same food resource, the floral stems. We tracked the fates of marked individuals located in nine populations over eight consecutive years in a Bothnian archipelago. We found no differences in survival probabilities between attacked and non-attacked plants or between the sexes. We found that attacked plants of both sexes re-flowered to a higher extent compared to non-attacked plants. However, there was an inter-sexual difference in response to attack. Attacked females tended to re-flower more often than males and therefore showed a stronger compensatory response to this type of herbivore attack. The likely mechanism for this difference is that females in response to attack of floral stems early in season will save more resources than males and that these resources will be retained in the basal rosette to be used for future reproductive events. This suggests a positive effect on plant life time fecundity in females. However, there is also a negative effect of florivory on number of capsules produced as capsule production was halved in attacked compared to non-attacked females. The demographic implications of these direct and indirect effects of florivory remain to be understood.
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- Pettersson, Viktoria, 1976-, et al.
(författare)
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Rates of insect herbivory on Silene dioica change across primary successional zones.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The strengths and directions of herbivore-host plant interactions are strongly shaped by environmental conditions that also affect a number of plant traits (density, size, nutritional quality). We studied spatio-temporal patterns in attack rates of two specialist herbivores Delia criniventris and Caryocolum viscariella that utilize the same food resource, the floral stems, of their shared host plant Silene dioica across young, intermediate and old successional zones in the primary succession in a Bothinan archipelago. Our data from nine islands collected during seven consecutive years showed that attack rates were consistently higher in the youngest zone and decreased in parallel to progressing succession. This zonal pattern of decreasing attack rates correlated with several plant attributes, a decrease in plant size and nitrogen content, and an increased content of secondary compounds, but not to host plant density. We failed to come up with a simple explanation for the spatial structure with chronic high attack rates in the younger zones. However, the consistent patterns in attack rate suggest that a suite of abiotic and biotic factors interact and reinforce the strength and direction of selection.
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- Pettersson, Viktoria, 1976-, et al.
(författare)
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Sex-biased herbivory in Silene dioica. : Which sex is the better resource?
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In cases when sexual dimorphic traits form the target resource of a particular herbivore we would expect the herbivore to select the best resource. We studied the interaction between to specialist insect herbivores Delia criniventris and Caryocolum viscariella that share the same food resource, the floral stems, of their host plant the perennial and dioecious herb, Silene dioica. We studied the interaction on nine islands in a Bothinan archipelago over seven consecutive years. Both herbivores attacked female plants more than male plants (D. criniventris, 32.8% females, 30.7% males; C. viscariella, 4% females, 2% males). The pattern was consistent over years and islands. We also found a number of sexually dimorphic traits suggesting females to be the better resource. We have presented evidence that female-biased herbivory does occur in dioecious plants and, as with male-biased herbivory, it may occur because herbivores utilise the better resource which will vary depending upon feeding strategy. We conclude that in dioecious species we need identify the dimorphism responsible for the sex sustaining the greatest attack rates and avoid being blinded by the expectation of male herbivory.
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