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  • 1.
    Hettyey, Attila
    et al.
    Ungern.
    Laurila, Anssi
    Uppsala University.
    Herczeg, Gábor
    Ungern.
    Jönsson, K. Ingemar
    Lund University.
    Kovács, Tibor
    Ungern.
    Merilä, Juha
    Finland.
    Does testis weight decline towards the Subarctic?: a case study on the common frog, Rana temporaria2005Inngår i: Die Naturwissenschaften, ISSN 0028-1042, E-ISSN 1432-1904, Vol. 92, nr 4, 188-192 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Interpopulation comparisons of variation in resource availability and in allocation patterns along altitudinal and latitudinal gradients allow insights into the mechanisms shaping the life history of animals. Patterns of between-population differences in female life history traits have been studied intensively across a wide range of taxa, but similar investigations in males have remained scarce. To study if testis weight-a measure of reproductive investment-varies on a geographical scale in anurans, we focussed on the variation in relative testis weight (RelTW) and asymmetry in 22 populations of the common frog Rana temporaria along a 1,600-km latitudinal transect across the Scandinavian peninsula. We found that RelTW decreased towards the north. Body mass and body length both had independent positive effects on testes mass. We found evidence for directional asymmetry (DA) in testis weight with the right testis being larger than the left. The level of DA in testis weight was not related to latitude, but both body mass and testes mass had independent positive effects on asymmetry. We discuss the northwards decrease in RelTW in terms of a decreased reproductive investment as a possible consequence of harsher environmental conditions, and perhaps also, weaker sexual selection in the north than in the south.

  • 2.
    Jönsson, K. Ingemar
    Lund University.
    The evolution of life histories in holo-anhydrobiotic animals: a first approach2005Inngår i: Integrative and Comparative Biology, ISSN 1540-7063, E-ISSN 1557-7023, Vol. 45, nr 5, 764-770 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The life histories of holo-anhydrobiotic animals differ from those of all other organisms by a regular or irregular entrance into an ametabolic state induced by desiccation. Such ametabolic periods will arrest growth and reproduction completely and thus affect primary life history parameters dramatically. The selective forces and the genetic and physiological trade-offs acting on anhydrobiotic animals are to a large extent unknown. Assuming low growth rates and low juvenile to adult survival, general theoretical models on life history responses to stress predict that anhydrobiotic animals will be selected for a high degree of iteroparity, with low fecundity, large egg size, and low total reproductive investment. A high degree of variability in growth and reproduction should create a selective force in the same direction. Although basic empirical data on life history parameters are very scarce, available observations seem to be consistent with this prediction.

  • 3.
    Jönsson, K. Ingemar
    et al.
    Lund University.
    Järemo, Johannes
    Lund University.
    A model on the evolution of cryptobiosis2003Inngår i: Annales Zoologici Fennici, ISSN 0003-455X, E-ISSN 1797-2450, Vol. 40, nr 4, 331-340 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cryptobiosis is an ametabolic state of life entered by some lower organisms (among metazoans mainly rotifers, tardigrades and nematodes) in response to adverse environmental conditions. Despite a long recognition of cryptobiotic organisms, the evolutionary origin and life history consequences of this biological phenomenon have remained unexplored. We present one of the first theoretical models on the evolution of cryptobiosis, using a hypothetical population of marine tardigrades that migrates between open sea and the tidal zone as the model framework. Our model analyses the conditions under which investments into anhydrobiotic (cryptobiosis induced by desiccation) functions will evolve, and which factors affect the optimal level Of Such investments. In particular, we evaluate how the probability of being exposed to adverse conditions (getting stranded) and the consequences for survival Of Such exposure (getting desiccated) affects the option for cryptobiosis to evolve. The optimal level of investment into anhydrobiotic traits increases with increasing probability of being stranded as well as with increasing negative survival effects of being stranded. However, our analysis shows that the effect on survival of being stranded is a more important parameter than the probability of stranding for the evolution of anhydrobiosis. The existing, although limited, evidence from empirical studies seems to support some of these predictions.

  • 4.
    Laugen, A T
    et al.
    Uppsala University.
    Laurila, A
    Uppsala University.
    Jönsson, K. Ingemar
    Lund University.
    Söderman, F
    Uppsala University.
    Merila, Juha
    Finland.
    Do common frogs (Rana temporaria) follow Bergmann's rule?2005Inngår i: Evolutionary Ecology Research, ISSN 1522-0613, E-ISSN 1937-3791, Vol. 7, nr 5, 717-731 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Questions: Does intraspecific extension of Bergmann's rule - larger size within a species in cooler areas - hold true for ectotherms in general, and for the common frog (Rana temporaria) in particular? What is the relative importance of genetic and environmental factors (i.e. direct environmental induction) in determining latitudinal patterns of body size variation in common frogs?

    Methods: We tested for a positive association between mean body size and latitude in common frogs (Rana temporaria) across a 1600 km long latitudinal gradient in Scandinavia both for wild-collected adults and laboratory-reared metamorphs.

    Results: In adults, the mean body size increased from south to mid-latitudes, and declined thereafter. This occurred despite the fact that the mean age of adult frogs increased with increasing latitude, and age and body size were positively correlated. The latitudinal pattern of body size variation in metamorphs reared in a common garden experiment was similar to that observed among wild-caught adults.

    Conclusions: The results suggest that the concave pattern of body size variation across the latitudinal cline may be at least partly genetically determined, and that although there is considerable geographic variation in mean body size of R. temporaria, this variation does not conform with Bergmann's rule.

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