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Abstract Detail


Lindberg, Erik [1], Ferrenberg, Scott [2], Schwilk, Dylan W [1].

Resin duct investment across space and time in west Texas pines.

Oleoresin is the predominant defense used by pines (Pinus) against herbivory, especially herbivory by bark beetles (Coleoptera: Curculionidae: Scolytinae). At the whole plant level, plant defense theory predicts a positive correlation between growth and defense investment under resource limitation that shifts to a negative correlation with increasing water or nutrient availability. Investment patterns may result from natural selection and life history variation across populations or from phenotypic plasticity. Resin production, however, is difficult to measure. Recent work demonstrates that resin duct density (number of resin ducts per unit cross sectional area of secondary xylem), predicts both bark beetle attack probabilities and subsequent tree survival. Assuming that resin production is proportional to supply capability, then we can use resin duct density as a proxy for defense investment. With tree xylem cores providing annual resolution of resin duct density in growth rings, we can estimate investment across individuals and within individuals over time. We conducted an exploratory analysis of how resin duct investment varied across life history, space, and time in three subsections of Pinus in west Texas.
We investigated the relative influence of environmental variables, age, and annual climate on growth and resin duct density across five species (Pinus arizonica var. stormiae, P. cembroides, P. edulis, P. ponderosa var. scopulorum, and P. strobiformis) representing three subsections (Cembroides, Ponderosae and Strobus) within Pinus. We collected cores from 159 trees and used mixed effects models to test the relative influence of subsection, environmental variables, and annual climate on resin duct density and ring width. Our main findings were (1) annual resin duct density decreases with tree age, and the relative rate by which it decreased was strongest in subsection Strobus. (2) young trees tend to invest less in resin ducts in high growth years and therefore resin duct density is negatively associated with ring width in younger trees. As trees age, this relationship changes and, in older trees, resin duct investment is either proportional to ring width or older trees invest disproportionately less in resin ducts in low growth years. (3) After accounting for environmental and age effects, the pinyon pines (Cembroides) had greater annual resin duct density than did Ponderosae or Strobus. The effect of age on resin duct density has often been overlooked, but could confound investigations of resin duct density across environmental gradients when tree age structure varies across space as a result of demographic variables or past disturbance.

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1 - Texas Tech University, Biological Sciences, Lubbock, TX, 79409-3131, USA
2 - University of Colorado, Biology, Boulder, CO, 80309, USA

bark beetles
sky islands

Presentation Type: Oral Paper
Session: 15, Ecology Section - Functional Traits and Responses
Location: Sundance 5/Omni Hotel
Date: Monday, June 26th, 2017
Time: 4:30 PM
Number: 15004
Abstract ID:125
Candidate for Awards:None

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