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Escape speed of Rana temporaria tadpoles along a latitudinal gradient: inducible defences interact with food availability
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Ecology and Evolution.
Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-96447OAI: oai:DiVA.org:uu-96447DiVA: diva2:171022
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Adaptation Along Environmental Gradients: an Evaluation of Physiological Mechanisms and Ecological Constraints
Open this publication in new window or tab >>Adaptation Along Environmental Gradients: an Evaluation of Physiological Mechanisms and Ecological Constraints
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For ectotherms living in seasonal environments, time available for development and growth is often constrained by the length of the growth season. Declining season length towards higher latitudes often select for latitudinal clines in development and growth rates, exhibiting increasing growth and developmental rates towards the north. However, the physiological and ecological factors enabling these clines are poorly understood.

Our study system included eight populations of Rana temporaria along a 1500 km latitudinal gradient. We found increased growth rates in populations at higher latitudes to be the result of higher growth efficiency, partly due to increased relative gut length. Populations with higher growth rates also exhibited lower standard metabolic rates, implying that fast-growing individuals are able to achieve high growth rates by spending less energy on maintenance metabolism under low activity conditions.

Predator densities, and antipredatory defenses in prey, are assumed to decrease towards higher latitudes. While all study populations responded to predator presence by decreasing activity and foraging, high latitude populations maintained higher activity levels in the presence of the predator. In trials with a free-ranging predator, high latitude tadpoles experienced higher mortality than those from the low latitudes. The higher activity level in the northern populations increases mortality under predation risk, but is probably needed to maintain high growth and development rates.

When competing over resources, tadpoles from the low latitude population were inferior competitors, as indicated by their longer development time when raised together with high latitude tadpoles. We found no effect of latitude on size-corrected burst speed. The general effect of predator presence on burst speed depended on food availability, with well fed tadpoles being faster in the absence, and food restricted being faster in the presence of a predator.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 48 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 366
Biology, Rana temporaria, latitudinal clines, growth rate, growth efficiency, SMR, predation, competition, trade-off, Biologi
urn:nbn:se:uu:diva-8310 (URN)978-91-554-7023-4 (ISBN)
Public defence
2007-11-30, Zootissalen, Evolutionary Biology Centre, Villavägen 9, Uppsala, 10:00
Available from: 2007-11-09 Created: 2007-11-09Bibliographically approved

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