| 1. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient
- 2009
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Ingår i: Ecography. - : Wiley-Blackwell. - 0906-7590 .- 1600-0587. ; 32:5, s. 831-839
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Tidskriftsartikel (refereegranskat)abstract
- The ability to store energy is an important life history trait for organisms facing long periods without energy income, and in particular for capital breeders such as temperate zone amphibians, which rely on stored energy during reproduction. However, large scale comparative studies of energy stores in populations with different environmental constraints on energy allocation are scarce. We investigated energy storage patterns in spring (after hibernation and before reproduction) in eight common frog (Rana temporaria) populations exposed to different environmental conditions along a 1600 km latitudinal gradient across Scandinavia (range of annual activity period 3-7 months). Analyses of lean body weight (eviscerated body mass), weight of fat bodies, liver weight, and liver fat content, showed that (i) post-hibernation/pre-breeding energy stores increased with increasing latitude in both sexes, (ii) males generally had larger energy reserves than females and (iii) the difference in energy stores between sexes decreased towards the north. Larger energy reserves towards the north can serve as a buffer against less predictable and/or less benign weather conditions during the short activity period, and may also represent a risk-averse tactic connected with a more pronounced iteroparous life history. In females, the continuous and overlapping vitellogenic activity in the north may also demand more reserves in early spring. The general sexual difference could be a consequence of the fact that, at the time of our sampling, females had already invested their energy into reproduction in the given year (i.e. their eggs were already ovulated), while the males' main reproductive activities (e.g. calling, mate searching, sexual competition) occurred later in the season.
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| 2. |
- Hettyey, Attila, et al.
(författare)
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Body temperature, size, nuptial colouration and mating success in male Moor Frogs (Rana arvalis)
- 2009
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Ingår i: Amphibia-Reptilia. - 0173-5373 .- 1568-5381. ; 30:1, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- Variation in colouration has rarely been related to sexual Selection ill anuran amphibians, even though such a relationship has been proven for many other vertebrate taxa. Male and female Moor Frogs (Rana arvalis) have a cryptic brown colour pattern, but males develop a conspicuous blue nuptial colouration during the reproductive season. To investigate: the possibility that colouration plays a role in sexual selection in this species, we Studied the temporal variation in blue colouration. determined if body size or body temperature affected blueness and investigated if blueness of males could be related to their mating, success. Results confirmed previous observation,,, that males develop and maintain blue colouration for only a very few nights during peak reproductive activity. Colouration of males was unrelated to body size, but males exhibiting higher body temperatures were somewhat bluer (hall males with lower body temperatures. Further, males in amplexus had higher body temperatures than non-mated males. Finally, Mating Success Was positively related to blueness in small males, whereas in large males no such relationship was detected. While our results align with the hypothesis that the bright blue colouration of males may be a target of sexual selection. alternative explanations are also discussed.
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| 3. |
- Hettyey, A, et al.
(författare)
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Does testis weight decline towards the Subarctic? A case study on the common frog, Rana temporaria
- 2005
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Ingår i: Naturwissenschaften. - : Springer Science and Business Media LLC. - 1432-1904 .- 0028-1042. ; 92:4, s. 188-192
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Tidskriftsartikel (refereegranskat)abstract
- 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 - ameasure 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.
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| 4. |
- Jones, Owen R., et al.
(författare)
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Senescence rates are determined by ranking on the fast-slow life-history continuum
- 2008
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 11:7, s. 664-673
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Tidskriftsartikel (refereegranskat)abstract
- Comparative analyses of survival senescence by using life tables have identified generalizations including the observation that mammals senesce faster than similar-sized birds. These generalizations have been challenged because of limitations of life-table approaches and the growing appreciation that senescence is more than an increasing probability of death. Without using life tables, we examine senescence rates in annual individual fitness using 20 individual-based data sets of terrestrial vertebrates with contrasting life histories and body size. We find that senescence is widespread in the wild and equally likely to occur in survival and reproduction. Additionally, mammals senesce faster than birds because they have a faster life history for a given body size. By allowing us to disentangle the effects of two major fitness components our methods allow an assessment of the robustness of the prevalent life-table approach. Focusing on one aspect of life history - survival or recruitment - can provide reliable information on overall senescence.
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| 5. |
- Jönsson, K. Ingemar, et al.
(författare)
-
Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient
- 2009
-
Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 32:5, s. 831-839
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to store energy is an important life history trait for organisms facing long periods without energy income, and in particular for capital breeders such as temperate zone amphibians, which rely on stored energy during reproduction. However, large scale comparative studies of energy stores in populations with different environmental constraints on energy allocation are scarce. We investigated energy storage patterns in spring (after hibernation and before reproduction) in eight common frog Rana temporaria populations exposed to different environmental conditions along a 1600 km latitudinal gradient across Scandinavia (range of annual activity period is 3-7 months). Analyses of lean body weight (eviscerated body mass), weight of fat bodies, liver weight, and liver fat content, showed that 1) post-hibernation/pre-breeding energy stores increased with increasing latitude in both sexes, 2) males generally had larger energy reserves than females and 3) the difference in energy stores between sexes decreased towards the north. Larger energy reserves towards the north can serve as a buffer against less predictable and/or less benign weather conditions during the short activity period, and may also represent a risk-averse tactic connected with a more pronounced iteroparous life history. In females, the continuous and overlapping vitellogenic activity in the north may also demand more reserves in early spring. The general sexual difference could be a consequence of the fact that, at the time of our sampling, females had already invested their energy into reproduction in the given year (i.e. their eggs were already ovulated), while the males' main reproductive activities (e.g. calling, mate searching, sexual competition) occurred later in the season.
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| 6. |
- Laugen, A T, et al.
(författare)
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Do common frogs (Rana temporaria) follow Bergmann's rule?
- 2005
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Ingår i: Evolutionary Ecology Research. - 1522-0613 .- 1937-3791. ; 7:5, s. 717-731
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 7. |
- Räsänen, Katja, et al.
(författare)
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Geographic variation in maternal investment : Acidity affects egg size and fecundity in Rana arvalis
- 2008
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 89:9, s. 2553-2562
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Tidskriftsartikel (refereegranskat)abstract
- Environmental-stress-mediated geographic variation in reproductive parameters has been little studied in natural vertebrate populations outside the context of climatic variation. Based on life-history theory, an increase in the degree of environmental stress experienced by a population should lead to (1) a shift in reproductive allocation from fecundity to offspring quality, (2) stronger trade-offs between reproductive parameters, and (3) changes in the relationship between female phenotype and maternal investment. To test these predictions, we investigated geographic variation in maternal investment of moor frogs (Rana arvalis) in relation to breeding site acidity (pH 4-8). We found that mean egg size increased and clutch size and total reproductive output (TRO) decreased with increasing acidity among 19 Swedish moor frog populations. Tests for variation and co-variation in maternal investment and female size and age in 233 females from a subset of four acid origin (AO) and four neutral origin (NO) populations revealed that clutch size and TRO increased with female size in both acid and neutral environments. However, in AO populations, egg size also increased with female size, and clutch size and TRO with female age, whereas in NO populations, egg size increased with female age. The strength of the egg-size-clutch-size trade-off tended to be stronger in AO than in NO females as expected if the former experience stronger environmental constraints. All in all, these results suggest that environmental acidfication selects for investment in larger eggs at a cost to fecundity, imposes negative effects on reproductive output, and alters the relationship between female phenotype and maternal investment.
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| 8. |
- Sorensen, Jesper Givskov, et al.
(författare)
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Complex patterns of geographic variation in heat tolerance and Hsp70 expression levels in the common frog Rana temporaria
- 2009
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Ingår i: Journal of Thermal Biology. - : Elsevier BV. - 0306-4565 .- 1879-0992. ; 34:1, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- 1. We tested for geographical variation in heat tolerance and Hsp70 expression levels of Rana temporaria tadpoles along a 1500 km long latitudinal gradient in Sweden. 2. Temperature tolerance of the hatchling tadpoles did not differ among populations, but they tolerated stressful hot temperatures better than 2 weeks older tadpoles. 3. Among 2-week old tadpoles, the southern population tolerated 32 C better than tadpoles from other populations. A parallel difference was found in Hsp70 expression, with the southern population showing the highest expression level. Nevertheless, at a highly stressful temperature (36 C) the northern population showed highest tolerance. 4. The heat shock pre-treatment increased heat tolerance of the tadpoles. The possible adaptive role of Hsp70 for thermal tolerance and climatic adaptation in R. temporaria tadpoles is discussed.
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