Trade‐offs between constitutive and induced defences drive geographical and climatic clines in pine chemical defences

Abstract

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° latitude and 2300 m elevation. Constitutive defences traded-off with induced defences, and these defensive strategies were associated with growth rate such that slow-growing species invested more in constitutive defence, whereas fast-growing species invested more in inducible defence. The position of each pine species along this trade-off axis was in turn associated with geography; moving poleward and to higher elevations, growth rate and inducible defences decreased, while constitutive defence increased. These geographic patterns in plant defence were most strongly associated with variation in temperature. Climatic and geographical clines thus act as drivers of defence profiles by mediating the constraints imposed by trade-offs, and this dynamic underlays global patterns of defence allocation.

Elevational gradients in plant defences and insect herbivory: recent advances in the field and prospects for future research

“…1B). In support of this hypothesis, Moreira et al (2014) found that constitutive and induced levels of defensive resins traded off among pine species, and an elevational gradient among species was observed for constitutive (but not induced) resins, with these defences increasing with elevation. Similarly, tradeoffs between tolerance and resistance have also been reported in other temperate plantinsect herbivore interactions (Fineblum andRausher 1995, Agrawal et al 1999) and are thus expected to tradeoff along elevational gradients.…”

“…Consequently, plant species adapted to environments with limiting abiotic conditions are predicted to increase allocation to expensive constitutive defences (relative to induced defences), as the energy demand of replacing tissues consumed by insect herbivores is higher under such stressful conditions (Moreira et al 2014, Pellissier et al 2016 (Fig. 1B).…”

“…Unconstrained ordination techniques (e.g. principal component analysis) have been widely used in ecology -including for the analysis of plant defences (Moreira et al 2014) -to reduce the dimensionality of datasets for analysis with common univariate statistical tests. Many types of plant defence and herbivore community data are also well suited for constrained ordination techniques (e.g.…”

Insect outbreak shifts the direction of selection from fast to slow growth rates in the long-lived conifer Pinus ponderosa

“…We suggest it may relate to delayed induced defense responses (47). Induced defenses are critical during bark beetle outbreaks (35), are under genetic control (48) and, importantly, often show a trade-off with constitutive defenses (49). Therefore, higher constitutive defenses in faster growing trees and families at our site (45, 50) may be associated with lower induced defenses.…”

Frankincense yield is related to tree size and resin-canal characteristics

“…Some tree species have resin canals filled with (constitutive) resin, which is transported to and released at wounded spots upon wounding, other species start producing (induced) resin after wounding and may require more time for defence against invaders (Lewinsohn et al, 1991;Trapp and Croteau, 2001) and some species can produce both constitutive and induced resin (Raffa and Berryman, 1982;Lombardero et al, 2000;Franceschi et al, 2005). Overall, the resin secretory structures and the type of resin (constitutive or induced) used for defence is largely species specific (Moreira et al, 2014). Recent evidence show that Boswellia trees have constitutive resin, but probably also produce induced resin upon wounding trees for frankincense harvest (Tolera et al, 2013a;Eshete et al, 2012a).…”