Can optimal defence theory be used to predict the distribution of plant chemical defences?
نویسندگان
چکیده
1. The optimal defence theory (ODT) of chemical defence provides a predictive framework for the distribution of anti-herbivore defences in plants. One of its predictions is that chemical defences will be allocated within a plant as a function of tissue value, where value is correlated with the cost of having that tissue removed. While many studies have examined intra-plant variation in defence chemistry, these results have rarely been compiled quantitatively to assess whether defence allocation is consistent with the prediction of ODT that more valuable tissues should be more defended than less valuable tissues. 2. We performed a formal meta-analysis of published and unpublished studies to examine the predictive utility of ODT. Specifically, we examined whether defence chemicals occur at higher concentrations in flowers versus leaves and in younger leaves compared to older leaves, under the assumption that younger leaves are more valuable than older leaves. We also examined whether the expansion status of younger leaves, nodal position of the leaves, growing conditions and chemical class of defence compounds affected the mean effect sizes. 3. We found that tissues with higher assumed value had significantly higher concentrations of defence chemicals than tissues with lower value. In particular, we found that younger leaves had higher concentrations of defence chemicals than older leaves, consistent with the predictions of ODT. The magnitude of this difference was higher in the younger leaf ⁄older leaf comparison than in the flower ⁄ leaf comparison, with no evidence that flowers were more defended than leaves. The overall results were not affected by chemical class, young leaf expansion status, growing conditions or leaf position on the plant. 4. Synthesis. We found general agreement between the predictions of ODT and the intraplant distribution of chemical defence and conclude it is a useful model. The effect size varied depending on the tissue compared. Explicit measures of tissue value, in particular as it relates to relative fitness, are required to further validate the predictive utility and general applicability of ODT.
منابع مشابه
Targeted predation of extrafloral nectaries by insects despite localized chemical defences.
Extrafloral (EF) nectaries recruit carnivorous arthropods that protect plants from herbivory, but they can also be exploited by nectar thieves. We studied the opportunistic, targeted predation (and destruction) of EF nectaries by insects, and the localized chemical defences that plants presumably use to minimize this effect. In field and laboratory experiments, we identified insects that were p...
متن کاملTrade-offs between constitutive and induced defences drive geographical and climatic clines in pine chemical defences.
There is increasing evidence that geographic and climatic clines drive the patterns of plant defence allocation and defensive strategies. We quantified early growth rate and both constitutive and inducible chemical defences of 18 Pinaceae species in a common greenhouse environment and assessed their defensive allocation with respect to each species' range across climatic gradients spanning 31° ...
متن کاملInduced plant defences in biological control of arthropod pests: a double‐edged sword
Biological control is an important ecosystem service delivered by natural enemies. Together with breeding for plant defence, it constitutes one of the most promising alternatives to pesticides for controlling herbivores in sustainable crop production. Especially induced plant defences may be promising targets in plant breeding for resistance against arthropod pests. Because they are activated u...
متن کاملSPECIAL FEATURE PLANT-MEDIATED INTERACTIONS BETWEEN ABOVE- AND BELOW-GROUND COMMUNITIES Plant defence theory re-examined: nonlinear expectations based on the costs and benefits of resource mutualisms
1. General theories of plant defence often fail to account for complex interactions between the resources required for defence expression. For example, the carbon that is used for carbon-based defence is acquired using nutrient-rich photosynthetic pigments, while nutrient gain itself requires substantial carbon allocation belowground. We should therefore expect the expression of plant defence t...
متن کاملInvestment in Seed Physical Defence Is Associated with Species' Light Requirement for Regeneration and Seed Persistence: Evidence from Macaranga Species in Borneo
The seed stage is often critical in determining the regeneration success of plants. Seeds must survive an array of seed predators and pathogens and germinate under conditions favourable for seedling establishment. To maximise recruitment success plants protect seeds using a diverse set of chemical and physical defences. However, the relationship between these defence classes, and their associat...
متن کامل