Differential resistance to freezing and spatial distribution in a chemically polymorphic plant Thymus vulgaris

Abstract

Secondary compounds play multiple ecological roles. In this study, we present novel experimental evidence of differential tolerance to freezing temperatures among chemotypes of a chemically polymorphic plant, Thymus vulgaris. Non-phenolic chemotypes showed a significantly better survival and re-growth after early-winter freezing ()10°in early December) than phenolic chemotypes. Comparison of temperature data at a phenolic and non-phenolic site showed that whereas early-winter freezing occurred in 6 years in the non-phenolic site they never occurred at the phenolic site. Observations of trichome morphology (where the essential oil is stocked) with and without intense freezing indicate that non-phenolic chemotypes may escape any negative effects of freezing by releasing their essential oil into the atmosphere during severe freezing. The correlation between tolerance of freezing and local temperature regimes strongly suggests that differential freezing resistance is a key ingredient of the distribution of thyme chemotypes in space.

Evolution of a genetic polymorphism with climate change in a Mediterranean landscape

“…In addition to the fact that phenolic chemotypes have been repeatedly shown to grow faster than nonphenolic chemotypes in the absence of early-winter freezing (28,39), trichomes (glands where the oil is stocked on the outer surface of leaves) on nonphenolic adult plants are more fragile with respect to freezing temperatures than those on phenolic plants (29). The latter result indicates that nonphenolic plants may be able to liberate monoterpenes outside of the plant rather than into the leaf upon freezing.…”

“…Such changes have occurred in 17 of the 24 populations where they could potentially occur. For more than 20 y, the freezing temperatures that have been shown to cause mortality of the phenolic chemotypes in early winter (28,29) have not occurred in the study area (Fig. 1).…”

“…2). In short, nonphenolic chemotypes show marked adaptation to habitats, which in the past have frequently experienced extreme freezing temperatures in early winter, whereas phenolic chemotypes are sensitive to intense early-winter freezing and occur in habitats where extreme summer drought can exclude nonphenolic chemotypes (28,29).…”

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

“…By monitoring how insect herbivory and plant defence along elevational gradients change over time, the list of candidate abiotic drivers can be narrowed substantially as novel climates decouple these factors. For example, Thompson and colleagues used multi-decadal elevational surveys of chemical defences (terpenes) in wild-growing thyme Thymus vulgaris to show that less palatable, freeze-intolerant chemical types have colonized higher elevations as climate change has changed the elevations where freezing occurs (Amiot et al 2005, Thompson et al 2013). However, researchers should be aware that climate change may affect other abiotic drivers of plant-insect herbivore interactions that may not vary over elevational gradients.…”

Компонентный Состав Эфирного Масла Thymus Baicalensis Serg. (Семейство Lamiaceae), Произрастающего На Территории Восточной Сибири И Монголии

“…-, , , [11]. , , [12], [13], , [14]. Plants of genus Thymus (Lamiaceae) are very popular in traditional and officinal medicine of many countries.…”