Flowers that cool themselves: Thermal ecology of summer-blooming thistles in hot Mediterranean environments

IF 7.1 1区 环境科学与生态学 Q1 ECOLOGY Ecological Monographs Pub Date : 2025-03-10 DOI:10.1002/ecm.70007
Carlos M. Herrera
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引用次数: 0

Abstract

Flower exposure to high temperature reduces the production, viability, and performance of pollen, ovules, and seeds, which in turn impairs individual fecundity and risks the survival of populations. Autonomous floral cooling could alleviate the effects of flower exposure to harmful temperatures, yet investigations on thermal ecology of flowers in hot environments are needed to evaluate the reality, magnitude, and ecological significance of thermoregulatory cooling. This paper reports a study on the thermal ecology of the flower heads (=capitula) of 15 species of summer-blooming Asteraceae, tribe Cardueae, from hot-dry habitats in the southern Iberian Peninsula. Temperature inside (Tin) and outside (Tout) capitula were assessed under natural field conditions using two complementary sampling and measurement procedures, which provided information on the relationships between the two temperatures at the levels of individual capitula (“continuous recording”) and local plant populations (“instantaneous measurements”). Baselines for the TinTout relationship in the absence of physiological activity were obtained by exposing dehydrated capitula to variable ambient temperatures in the field. To assess whether the co-flowering capitula of summer-blooming Asteraceae defined collectively a distinct thermal layer, the vertical distribution of capitula relative to the ground was quantified. Bees visiting capitula were watched and temperature of the air beside the visited capitulum was measured. Results were remarkably similar for all plant species. The capitula experienced high ambient temperatures during long periods, yet their interior was cooler than the air most of the time, with temperature differentials (ΔT = Tin − Tout) often approaching, and sometimes exceeding −10°C. The relationship between Tin and Tout was best described by a composite of one steep and one shallow linear relationship separated by a breakpoint (Ψ, interspecific range = 25–35°C). Capitula were only weakly thermoregulated when Tout < Ψ, but switched to closely thermoregulated cooling when Tout > Ψ. Narrow vertical distributions of capitula above the ground and similar cooling responses by all species resulted in a “refrigerated floral layer” where most bees foraged at Tout > Ψ and presumably visited cooled capitula. Thermoregulatory refrigeration of capitula (“thermal engineering”) can benefit not only plant reproduction by reducing pollen and ovule exposure to high temperatures during the summer but also the populations of bee pollinators and other floricolous insects.

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来源期刊
Ecological Monographs
Ecological Monographs 环境科学-生态学
CiteScore
12.20
自引率
0.00%
发文量
61
审稿时长
3 months
期刊介绍: The vision for Ecological Monographs is that it should be the place for publishing integrative, synthetic papers that elaborate new directions for the field of ecology. Original Research Papers published in Ecological Monographs will continue to document complex observational, experimental, or theoretical studies that by their very integrated nature defy dissolution into shorter publications focused on a single topic or message. Reviews will be comprehensive and synthetic papers that establish new benchmarks in the field, define directions for future research, contribute to fundamental understanding of ecological principles, and derive principles for ecological management in its broadest sense (including, but not limited to: conservation, mitigation, restoration, and pro-active protection of the environment). Reviews should reflect the full development of a topic and encompass relevant natural history, observational and experimental data, analyses, models, and theory. Reviews published in Ecological Monographs should further blur the boundaries between “basic” and “applied” ecology. Concepts and Synthesis papers will conceptually advance the field of ecology. These papers are expected to go well beyond works being reviewed and include discussion of new directions, new syntheses, and resolutions of old questions. In this world of rapid scientific advancement and never-ending environmental change, there needs to be room for the thoughtful integration of scientific ideas, data, and concepts that feeds the mind and guides the development of the maturing science of ecology. Ecological Monographs provides that room, with an expansive view to a sustainable future.
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