Interactions between Abert's Squirrel and Ponderosa Pine: The Relationship between Selective Herbivory and Host Plant Fitness

Snyder, Marc A.

doi:10.1086/285513

Cited by 44 publications

(37 citation statements)

References 18 publications

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“…Mammalian herbivore damage can have adverse effects on overall plant fitness (e.g. Bergström and Danell 1987;Snyder 1993), and vertebrate herbivores can remove plant species from communities by selective predation of seedlings (Crawley 1989). While we have not directly measured effects of herbivores on plant fitness in E. globulus, other evidence suggests that herbivory by marsupials, including Trichosurus vulpecula and Thylogale billardierii, greatly reduces plant fitness in eucalypts.…”

Section: Discussionmentioning

confidence: 99%

“…Snyder 1993;Lawler et al 1998) but only a few studies have implicated the influence of plant genetics in resistance to mammalian herbivores (Dimock Genetic variation in resistance of Eucalyptus globulus to marsupial browsers et al 1976;Snyder 1993;Mutikainen et al 2000). In this study, we investigate both the intraspecific variation in plant resistance to mammalian herbivores and the genetic basis of this resistance.…”

Section: Introductionmentioning

confidence: 95%

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Genetic variation in resistance of Eucalyptus globulus to marsupial browsers

2002

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The evolution of plant defensive traits in response to selection pressures imposed by herbivores is central to co-evolutionary theory. To demonstrate the role of herbivores as selective agents on plant resistance there must be variability in plant resistance to herbivores within a plant population. This variability must be under genetic control, and the variability in plant resistant traits and consequently herbivore damage to plants must reflect variability in plant fitness. We used a common eucalypt species, Eucalyptus globulus, and two major mammalian herbivores, the common brushtail possum (Trichosurus vulpecula) and the red-bellied pademelon (Thylogale billardierii), as a system to investigate intraspecific variation in plant resistance to mammalian herbivores and to investigate if this variation has a genetic basis. We measured mammalian browsing damage on 2,302 individual trees of E. globulus, from 563 families derived from range-wide native stand seed collections of known pedigree and grown in a common environment field trial. Using a selection of trees from the field trial we then conducted a feeding trial with captive herbivores to assess if the genetic variation in plant resistance in the field was reflected in feeding preferences of captive animals, as measured by relative intake. Results from the field trial showed significant genetic variation in plant resistance amongst races, localities and amongst different families. These results were consolidated in the captive trial with similar trends in genetic variation among E. globulus localities. Dry matter intake of foliage by Trichosurus vulpecula was consistently greater than that by Thylogale billardierii; however, the intraspecific preferences of the two herbivores were significantly correlated.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Genetic variation in resistance of Eucalyptus globulus to marsupial browsers

2002

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“…Oleoresin composition does have demonstrable effects on herbivore choices in other populations under attack by different species of herbivore. Several herbivores, such as mountain pine beetle and Abert's squirrel are known to have strong negative effects on the growth and fitness of ponderosa pine, as well as documented feeding preferences associated with specific monoterpenes Sturgeon 1979;Mitton and Sturgeon 1982;Snyder 1992Snyder , 1993. However, this population has not been exposed to either of these species in the past decades.…”

Section: Discussionmentioning

confidence: 99%

“…For example, individuals of ponderosa pine (Pinus ponderosa Laws) with rare monoterpene compositions appear better able to survive outbreaks of bark beetles (Dendroctonus brevicomis) than those with common resin profiles (Sturgeon 1979). Snyder (1992Snyder ( , 1993 experimentally manipulated the monoterpene concentration in artificial food sources, and demonstrated that monoterpenes also serve to deter herbivory by Abert's squirrel Sciurus aberti), and that squirrel herbivory has a negative effect on the fitness of the tree.…”

Section: Introductionmentioning

confidence: 99%

Path analysis of natural selection on plant chemistry: the xylem resin of ponderosa pine

Latta¹,

Linhart²

1997

Oecologia

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We analyzed the pattern of correlations among fitness components, herbivory, and resin characteristics in a natural all-aged stand of ponderosa pine, to infer the strength and mechanism of natural selection on plant chemistry. Male and female cone production were monitored yearly for 15 years, and levels of herbivory for 9 years in 165 trees. Resin flow rate and monoterpene composition were determined for these same trees. Multiple regression of fitness components on resin characteristics showed significant associations consistent with directional selection for increased resin flow rates and increased proportions of α- and β-pinene, myrcene and terpinolene. However, negative correlations among monoterpene fractions of the resin constrained the overall selection. Selective herbivory by aphids approached statistical significance and monoterpenes showed some (non-significant) effect as deterrents against deer browse. Resin characteristics were not correlated with attack by cone insects or porcupines. However, the association between resin characteristics and fitness is significantly different from that predicted by the path coefficients involving herbivores. Therefore the hypothesis that these herbivores mediate selection on the resin is not supported by the observed pattern of correlations among resin characteristics, herbivory, growth and fecundity. In this population, most of the association between resin characteristics and fitness appears to be mediated by some other factor independent of attack by herbivore species present.

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“…The different chemotypes are impacted by herbivory in different ways. For the highly specialised bark-feeding Albert's squirrel (Sciuridae alberti) on ponderosa pine, the percentage composition of the major monoterpene β-pinene differed significantly between target and non-target trees (Snyder 1993). Sitka spruce trees that showed resistance to the white pine weevil had highly significant differences in the resin composition of the major monoterpenes β-pinene and β-phellandrene when compared with susceptible trees (Harris et al 1983).…”

Section: Introductionmentioning

confidence: 99%

Monoterpene chemodiversity of ponderosa pine in relation to herbivory and bark beetle colonization

Thoss

Byers

2006

Chemoecology

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Ponderosa pine, Pinus ponderosa Laws. (Pinaceae), forests in Arizona have suffered from a nine-year period of drought and bark beetle, Ips lecontei Swaine (Coleoptera: Scolytidae), outbreaks. Abiotic and biotic stress in ponderosa pine results in the induced synthesis of certain monoterpenes that may in turn affect bark beetle behavior and survival. In this study, we investigate whether induced monoterpene production could result in a different monoterpene composition that remains stored in the needles or the trunk resin of the tree. Needle and resin samples in addition to trunk cores were collected from ponderosa pines at three locations in Arizona. Ungulate browsing induced a significant increase in limonene (P=0.010) and in chemodiversity (P=0.009), a measure of the evenness of distribution among the monoterpenes present in needles. We compared the level of 'stress' of the trees by measuring the thickness of annual rings in living trees and those that were killed by bark beetles. Where drought occurred, the spacing of annual rings from the last 10 years of trees killed by bark beetles was significantly smaller (P=0.020) compared to living trees. There was no difference in the monoterpene composition between the core sections of closest spacing of annual rings (stressed years) compared to the sections of widest spacing, which indicates that monoterpenes are distributed evenly throughout the extended resin system. In the area where the degree of drought was less overall, none of the individual monoterpenes present in the resin was related to bark beetle killed trees. However, about half the living pines had resin in which one of the major monoterpenes (α-pinene, ∆ 3 -carene, and limonene) was absent, and these trees had a lower monoterpene chemodiversity compared to trees killed by bark beetles. Trees with these three major monoterpenes, corresponding to the average relative proportion in living pines at that location, may sustain higher selection and colonization by bark beetles.

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Interactions between Abert's Squirrel and Ponderosa Pine: The Relationship between Selective Herbivory and Host Plant Fitness

Cited by 44 publications

References 18 publications

Genetic variation in resistance of Eucalyptus globulus to marsupial browsers

Genetic variation in resistance of Eucalyptus globulus to marsupial browsers

Path analysis of natural selection on plant chemistry: the xylem resin of ponderosa pine

Monoterpene chemodiversity of ponderosa pine in relation to herbivory and bark beetle colonization

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