The South-western USA and Northern Mexico one-seeded Junipers: their volatile oils and evolution

Adams, Robert P.; Zanoni, Thomas A.; Rudgloff, Ernst Von; Hogge, Lawrence

doi:10.1016/0305-1978(81)90025-9

Cited by 42 publications

(33 citation statements)

References 10 publications

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“…It is low in nitrogen (1.00% by dry weight ;Dial 1988) and high in fiber (24% cellulose and lignin, this study). Juniper produces considerable quantities of secondary compounds, particularly monoterpenes and phenolics (Adams et al 1981;Holchek et al 1990). The predominant monoterpene, α-pinene, has numerous deleterious effects on mammals including neurotoxicity, irritation of mucous membranes, and nephritis (Hedenstierna et al 1983;Koppel et al 1981;Levin et al 1992).…”

Section: Introductionmentioning

confidence: 99%

Diet breadth of mammalian herbivores: nutrient versus detoxification constraints

2000

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Two hypotheses, nutrient constraints and detoxification limitation, have been proposed to explain the lack of specialists among mammalian herbivores. The nutrient constraint hypothesis proposes that dietary specialization in mammalian herbivores is rare because no one plant can provide all requisite nutrients. The detoxification limitation hypothesis suggests that the mammalian detoxification system is incapable of detoxifying high doses of similar secondary compounds present in a diet of a single plant species. We experimentally tested these hypotheses by comparing the performance of specialist and generalist woodrats (Neotoma) on a variety of dietary challenges. Neotoma stephensi is a narrow dietary specialist with a single species, one-seeded juniper, Juniperus monosperma, comprising 85-95% of its diet. Compared with other plants available in the habitat, juniper is low in nitrogen and high in fiber, phenolics, and monoterpenes. The generalist woodrat, N. albigula, also consumes one-seeded juniper, but to a lesser degree. The nutrient constraint hypothesis was examined by feeding both species of woodrats a low-nitrogen, high-fiber diet similar to that found in juniper. We found no differences in body mass change, or apparent digestibility of dry matter or nitrogen between the two species of woodrats after 35 days on this diet. Moreover, both species were in positive nitrogen balance. We tested the detoxification limitation hypothesis by comparing the performance of the generalist and specialist on diets with and without juniper leaves, the preferred foliage of the specialist, as well as on diets with and without α-pinene, the predominant monoterpene in juniper. We found that on the juniper diet, compared with the specialist, the generalist consumed less juniper and lost more mass. Urine pH, a general indicator of overall detoxification processes, declined in both groups on the juniper diet. The generalist consumed half the toxin load of the specialist yet its urine pH was slightly lower. Moreover, the generalist consumed significantly less of the treatment with high concentrations of α-pinene compared to the control treatment, while the specialist consumed the same amount of food regardless of α-pinene concentration. For both groups, urine pH declined as levels of α-pinene in the diet increased. The generalist produced a significantly more acidic urine than the specialist on the treatment with the highest α-pinene concentration. Our results suggest that in this system, specialists detoxify plant secondary compounds differently than generalists and plant secondary compounds may be more important than low nutrient levels in maintaining dietary diversity in generalist herbivores.

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Section: Introductionmentioning

confidence: 99%

Diet breadth of mammalian herbivores: nutrient versus detoxification constraints

2000

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“…Although thermogenesis has not yet been demonstrated for any known PSCs in juniper, other PSCs, such as capsaicin and caffeine, are noted for their thermogenic activity in humans (Westerterp-Plantenga et al 2006). Turpentine contains PSCs similar to those in juniper (Mirov et al 1962;Adams et al 1981) and is routinely used to experimentally induce hyperthermia in laboratory animals (Xie et al 2006;Hernán-dez-Espinosa et al 2007). Subcutaneous administration of turpentine elevated T b of mice (Hernández-Espinosa et al 2007) and rabbits (Xie et al 2006) more than 1ЊC for 6-24 h after administration.…”

Section: Pscs and Thermoregulationmentioning

confidence: 99%

“…D. Dearing, personal observations). Juniper has notable levels of PSCs, particularly terpenes and, to a lesser extent, phenolics (Adams et al 1981;Nú ñez-Hernández et al 1989). The limited amount of juniper that N. albigula can consume is largely dictated by PSCs and not nutrient content (Dearing et al 2000;Sorensen et al 2005b).…”

Section: Introductionmentioning

confidence: 99%

Ambient Temperature Influences Diet Selection and Physiology of an Herbivorous Mammal, Neotoma albigula

Dearing¹,

Forbey²,

McLister³

et al. 2008

Physiological and Biochemical Zoology

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The whitethroat woodrat (Neotoma albigula) eats juniper (Juniperus monosperma), but the amount of juniper in its diet varies seasonally. We tested whether changes in juniper consumption are due to changes in ambient temperature and what the physiological consequences of consuming plant secondary compounds (PSCs) at different ambient temperatures might be. Woodrats were acclimated to either 20ЊC or 28ЊC. Later, they were given two diets to choose from (50% juniper and a nontoxic control) for 7 d. Food intake, resting metabolic rate (RMR), and body temperature (T b ) were measured over the last 2 d. Woodrats at 28ЊC ate significantly less juniper, both proportionally and absolutely, than woodrats at 20ЊC. RMRs were higher for woodrats consuming juniper regardless of ambient temperature, and T b was higher for woodrats consuming juniper at 28ЊC than for woodrats eating control diet at 28ЊC. Thus, juniper consumption by N. albigula is influenced by ambient temperature. We conclude that juniper may influence thermoregulation in N. albigula in ways that are helpful at low temperatures but harmful at warmer temperatures in that juniper PSCs may be more toxic at warmer temperatures. The results suggest that increases in ambient temperature associated with climate change could significantly influence foraging behavior of mammalian herbivores.

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“…stephensi and N. albigula represent a model study system to initially test detoxification limitations in specialist and generalist mammalian herbivores. These species occur sympatrically, are similar in body size, and have equal access to juniper (Juniperus monosperma), which is high in plant secondary compounds (Adams 1994;Adams et al 1981). Despite these similarities, the two species have disparate foraging strategies in both the field and the laboratory (Dearing et al 2000;Dial 1988).…”

Section: Introductionmentioning

confidence: 97%

Elimination of plant toxins by herbivorous woodrats: revisiting an explanation for dietary specialization in mammalian herbivores

Sorensen

Dearing

2003

Oecologia

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Constraints on rates of detoxification and elimination of plant toxins are thought to be responsible for limiting dietary specialization in mammalian herbivores. This hypothesis, known as the detoxification limitations hypothesis, suggests that most mammalian herbivores are generalists to avoid overdosing on toxins from a single plant species. The hypothesis also predicts that the few mammalian specialists that exist should have adaptations for rapid detoxification and elimination of plant secondary compounds. We took a pharmacological approach to test whether specialists eliminate toxins from the bloodstream faster than generalists. We compared elimination rate and total exposure of alpha-pinene in closely related dietary specialist and generalist woodrats, Neotoma stephensi and N. albigula, respectively. Animals were orally gavaged with alpha-pinene, a plant secondary compound present in the natural diets of both woodrat species. We collected venous blood at 3, 6, 10, 15, and 20 min post-ingestion of alpha-pinene. Blood was analyzed for alpha-pinene concentration using gas chromatography. We found that specialist and generalist woodrats did not differ in elimination rates of alpha-pinene. However, specialists had lower exposure levels of alpha-pinene than generalists due to lower initial delivery of alpha-pinene to the general circulation. The levels of alpha-pinene detected in the bloodstream of specialists were 4.7-5.3x lower over all time intervals than generalists. Thus, specialists encounter a functionally lower dose of toxin than generalists. We suggest that the lower exposure level of specialist woodrats may be due to mechanisms in the gut that decrease toxin absorption. Regardless of mechanism, lower exposure to plant toxins may allow specialists to forage on diets with high toxin concentrations thereby facilitating dietary specialization.

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The South-western USA and Northern Mexico one-seeded Junipers: their volatile oils and evolution

Cited by 42 publications

References 10 publications

Diet breadth of mammalian herbivores: nutrient versus detoxification constraints

Diet breadth of mammalian herbivores: nutrient versus detoxification constraints

Ambient Temperature Influences Diet Selection and Physiology of an Herbivorous Mammal, Neotoma albigula

Elimination of plant toxins by herbivorous woodrats: revisiting an explanation for dietary specialization in mammalian herbivores

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