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Latitudinal patterns of phenology and age-specific thermal performance across six Coenagrion damselfly species (Odonata)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
University of Leuven.
University of Leuven.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Using a combination of computer simulations and laboratory experiments we test if the thermal sensitivity of growth rates change during ontogeny and if variation in age-specific growth rates can be predicted based on the natural progression of average temperature or thermal variability in the field. Although annual fluctuations in temperature represent a key characteristic of temperate environments, very few studies of thermal performance have considered the ecological importance of the studied traits within a seasonal context. Instead, thermal performance is assumed to remain constant throughout ontogeny and reflect selection acting over the whole life cycle. Our laboratory experiment revealed that the slope of reaction norms of growth rates changed during ontogeny in five out of six species. In four species from Southern and Central Europe, reaction norms were steepest during early ontogeny, becoming less steep later in life (low-temperature acclimation). In one species from Northern Europe, no change in the slope of reaction norms occurred. In the other North European species, reaction norms became steeper during ontogeny (high-temperature acclimation). Because high-latitude species have a short flight season and inhabit a strongly seasonal environment, we had expected high-latitude species to show strong low-temperature acclimation responses. Instead, we found the reversed pattern: low-latitude species displayed strong low-temperature acclimation responses and high-latitude species displayed weak, or even reversed, acclimation responses to low temperatures. Therefore, we suggest that acclimation to low temperatures may be less beneficial and possibly more costly in habitats with rapid seasonal transitions in average temperature. We conclude that thermal performance traits are more dynamic than typically assumed and caution against using results from single ontogenetic stages to predict species’ responses to changing environmental conditions.

National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-62272OAI: oai:DiVA.org:umu-62272DiVA: diva2:576934
Funder
Swedish Research Council Formas
Available from: 2012-12-14 Created: 2012-12-14 Last updated: 2017-02-01Bibliographically approved
In thesis
1. Thermal adaptation along a latitudinal gradient in damselflies
Open this publication in new window or tab >>Thermal adaptation along a latitudinal gradient in damselflies
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Understanding how temperature affects biological systems is a central question in ecology and evolutionary biology. Anthropogenic climate change adds urgency to this topic, as the demise or success of species under climate change is expected to depend on how temperature affects important aspects of organismal performance, such as growth, development, survival and reproduction. Rates of biological processes generally increase with increasing temperature up to some maximal temperature. Variation in the slope of the initial, rising phase has attracted considerable interest and forms the focus of this thesis. I explore variation in growth rate-temperature relationships over several levels of biological organization, both between and within species, over individuals’ lifetime, depending on the ecological context and in relation to important life history characteristics such as generation length and winter dormancy.

      Specifically, I examine how a clade of temperate damselflies have adapted to their thermal environment along a 3,600 km long latitudinal transect spanning from Southern Spain to Northern Sweden. For each of six species, I sampled populations from close to the northern and southern range margin, as well from the center of the latitudinal range. I reared larvae in the laboratory at several temperatures in order to measure indiviudal growth rates. Very few studies of thermal adaptation have employed such an extensive sampling approach, and my finding reveal variation in temperature responses at several levels of organization.

      My main finding was that temperature responses became steeper with increasing latitude, both between species but also between latitudinal populations of the same species. Additional genetic studies revealed that this trend was maintained despite strong gene flow. I highlight the need to use more refined characterizations of latitudinal temperature clines in order to explain these findings. I also show that species differ in their ability to acclimate to novel conditions during ontogeny, and propose that this may reflect a cost-benefit trade-off driven by whether seasonal transitions occur rapidly or gradually during ontogeny.

      I also carried out a microcosm experiment, where two of the six species were reared either separately or together, to determine the interacting effects of temperature and competition on larval growth rates and population size structure. The results revealed that the effects of competition can be strong enough to completely overcome the rate-depressing effects of low temperatures. I also found that competition had stronger effects on the amount of variation in growth rates than on the average value.

      In summary, my thesis offers several novel insights into how temperature affects biological systems, from individuals to populations and across species’ ranges. I also show how it is possible to refine our hypotheses about thermal adaptation by considering the interacting effects of ecology, life history and environmental variation.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2012. 35 p.
Keyword
Growth rate, metabolic theory of ecology, universal temperature dependence, environmental gradients, thermal performance, thermal sensitivity, environmental variability, optimality theory, life history, acclimation, size structure, competition, cannibalism, intraguild predation
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-62276 (URN)978-91-7459-529-1 (ISBN)
Public defence
2013-01-18, N450, Umeå Universitet, Johan Bures väg 14, Umeå, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas
Available from: 2012-12-21 Created: 2012-12-14 Last updated: 2017-02-01Bibliographically approved

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