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Antipredator defenses along a latitudinal gradient in Rana temporaria
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution.
2008 (English)In: Ecology, ISSN 0012-9658, Vol. 89, no 5, 1399-1413 p.Article in journal (Refereed) Published
Abstract [en]

Antipredator defenses are expected to decrease toward higher latitudes because predation rates are predicted to decrease with latitude. However, latitudinal variation in predator avoidance and defense mechanisms has seldom been studied. We studied tadpole antipredator defenses in seven Rana temporaria populations collected along a 1500-km latitudinal gradient across Sweden, along which previous studies have found increasing tadpole growth and development rates. In a laboratory common garden experiment, we measured behavioral and morphological defenses by raising tadpoles in the presence and absence of a predator (Aeshna dragonfly larva) in two temperature treatments. We also estimated tadpole survival in the presence of free-ranging predators and compared predator densities between R. temporaria breeding ponds situated at low and high latitudes. Activity and foraging were generally positively correlated with latitude in the common garden experiment. While all populations responded to predator presence by decreasing activity and foraging, high-latitude populations maintained higher activity levels in the presence of the predator. All populations exhibited defensive morphology in body and tail shape. However, whereas tail depth tended to increase with latitude in the presence of predator, it did not change with latitude in the absence of the predator. Predator presence generally increased larval period and decreased growth rate. In the southern populations, predator presence tended to have a negative effect on metamorphic size, whereas in the northern populations predators had little or a positive effect on size. Latitude of origin had a strong effect on survival in the presence of a free-ranging predator, with high-latitude tadpoles experiencing higher mortality than those from the low latitudes. In the wild, predator densities were significantly lower in high-latitude than in mid-latitude breeding ponds. Although the higher activity level in the northern populations seems to confer a significant survival disadvantage under predation risk, it is probably needed to maintain the high growth and development rates. However, the occurrence of R. temporaria at high latitudes may be facilitated by the lower predator densities in the north.

Place, publisher, year, edition, pages
2008. Vol. 89, no 5, 1399-1413 p.
Keyword [en]
activity, amphibians, growth, inducible defenses, latitudinal gradient, life history, morphology, population differentiation, predation, Rana temporaria
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96445ISI: 000256101200022OAI: oai:DiVA.org:uu-96445DiVA: diva2:171020
Available from: 2007-11-09 Created: 2007-11-09 Last updated: 2009-11-04Bibliographically 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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 366
Keyword
Biology, Rana temporaria, latitudinal clines, growth rate, growth efficiency, SMR, predation, competition, trade-off, Biologi
Identifiers
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
Opponent
Supervisors
Available from: 2007-11-09 Created: 2007-11-09Bibliographically approved

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