| 1. |
- Alho, Jussi S., et al.
(author)
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Increasing melanism along a latitudinal gradient in a widespread amphibian : local adaptation, ontogenic or environmental plasticity?
- 2010
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In: BMC Evolutionary Biology. - 1471-2148 .- 1471-2148. ; 10, s. 317-
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Journal article (peer-reviewed)abstract
- BackgroundThe thermal benefits of melanism in ectothermic animals are widely recognized, but relatively little is known about population differentiation in the degree of melanism along thermal gradients, and the relative contributions of genetic vs. environmental components into the level of melanism expressed. We investigated variation in the degree of melanism in the common frog (Rana temporaria; an active heliotherm thermoregulator) by comparing the degree of melanism (i) among twelve populations spanning over 1500 km long latitudinal gradient across the Scandinavian Peninsula and (ii) between two populations from latitudinal extremes subjected to larval temperature treatments in a common garden experiment.ResultsWe found that the degree of melanism increased steeply in the wild as a function of latitude. Comparison of the degree of population differentiation in melanism (PST) and neutral marker loci (FST) revealed that the PST > FST, indicating that the differences cannot be explained by random genetic drift alone. However, the latitudinal trend observed in the wild was not present in the common garden data, suggesting that the cline in nature is not attributable to direct genetic differences.ConclusionsAs straightforward local adaptation can be ruled out, the observed trend is likely to result from environment-driven phenotypic plasticity or ontogenetic plasticity coupled with population differences in age structure. In general, our results provide an example how phenotypic plasticity or even plain ontogeny can drive latitudinal clines and result in patterns perfectly matching the genetic differences expected under adaptive hypotheses.
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| 2. |
- Hettyey, Attila, et al.
(author)
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Body temperature, size, nuptial colouration and mating success in male Moor Frogs (Rana arvalis)
- 2009
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In: Amphibia-Reptilia. - 0173-5373 .- 1568-5381. ; 30:1, s. 37-43
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Journal article (peer-reviewed)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. |
- Hjernquist, Mårten B., et al.
(author)
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Seasonality determines patterns of growth and age structure over a geographic gradient in an ectothermic vertebrate
- 2012
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In: Oecologia. - 0029-8549 .- 1432-1939. ; 170:3, s. 641-649
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Journal article (peer-reviewed)abstract
- Environmental variation connected with seasonality is likely to affect the evolution of life-history strategies in ectotherms, but there is no consensus as to how important life-history traits like body size are influenced by environmental variation along seasonal gradients. We compared adult body size, skeletal growth, mean age, age at first reproduction and longevity among 11 common frog ( Rana temporaria ) populations sampled along a 1,600-km-long latitudinal gradient across Scandinavia. Mean age, age at first reproduction and longevity increased linearly with decreasing growth season length. Lifetime activity (i.e. the estimated number of active days during life-time) was highest at mid-latitudes and females had on average more active days throughout their lives than males. Variation in body size was due to differences in lifetime activity among populations—individuals (especially females) were largest where they had the longest cumulative activity period—as well as to differences between populations in skeletal growth rate as determined by skeletochronological analyses. Especially, males grew faster at intermediate latitudes. While life-history trait variation was strongly associated with latitude, the direction and shape of these relationships were sex- and trait-specific. These context-dependent relationships may be the result of life-history trade-offs enforced by differences in future reproductive opportunities and time constraints among the populations. Thus, seasonality appears to be an important environmental factor shaping life-history trait variation in common frogs.
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| 4. |
- Hjernquist, Mårten B., et al.
(author)
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Seasonality determines patterns of growth and age structure over a geographic gradient in an ectothermic vertebrate
- 2012
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In: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 170:3, s. 641-649
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Journal article (peer-reviewed)abstract
- Environmental variation connected with seasonality is likely to affect the evolution of life-history strategies in ectotherms, but there is no consensus as to how important life-history traits like body size are influenced by environmental variation along seasonal gradients. We compared adult body size, skeletal growth, mean age, age at first reproduction and longevity among 11 common frog (Rana temporaria) populations sampled along a 1,600-km-long latitudinal gradient across Scandinavia. Mean age, age at first reproduction and longevity increased linearly with decreasing growth season length. Lifetime activity (i.e. the estimated number of active days during life-time) was highest at mid-latitudes and females had on average more active days throughout their lives than males. Variation in body size was due to differences in lifetime activity among populations-individuals (especially females) were largest where they had the longest cumulative activity period-as well as to differences between populations in skeletal growth rate as determined by skeletochronological analyses. Especially, males grew faster at intermediate latitudes. While life-history trait variation was strongly associated with latitude, the direction and shape of these relationships were sex- and trait-specific. These context-dependent relationships may be the result of life-history trade-offs enforced by differences in future reproductive opportunities and time constraints among the populations. Thus, seasonality appears to be an important environmental factor shaping life-history trait variation in common frogs.
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| 5. |
- Patrelle, Cecile, et al.
(author)
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Sex differences in age structure, growth rate and body size of common frogs Rana temporaria in the subarctic
- 2012
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In: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 35:10, s. 1505-1513
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Journal article (peer-reviewed)abstract
- The thermal environment and length of the activity season are important factors in shaping life-history trait variation in ectotherms. Many ectothermic vertebrates living at high latitudes or altitudes tend to be larger and older than their conspecifics living at lower latitudes or altitudes. However, detailed data on age, body size and growth variation-and how they may differ between males and females-are still scarce, especially from extreme high-latitude environments. We studied growth (body length increment), age and size structure of common frogs (Rana temporaria) in subarctic Finland (69A degrees 04'N) by applying skeletochronological methods to individually marked adults (n = 169) captured and recaptured between 1999 and 2003. We found that breeding males were on average younger (mean = 8.5 years) than females (11.9 years) and that males started reproducing earlier (a parts per thousand yen3-4 years of age) than females (> 4-5 years). The oldest encountered individual was an 18-year-old female, which to our knowledge is the oldest wild common frog ever reported. Females were on average larger (mean body length = 76.6 mm) than males (70.7 mm), and this appeared to be mainly due to their older age as compared to males. While body length increased and growth rate decreased with age in both sexes, growth rate declined significantly faster with age in males than in females. The latter finding provides a proximate explanation for the observation that even after accounting for age differences among sexes (females > males), females were longer than males.
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| 6. |
- Räsänen, Katja, et al.
(author)
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Geographic variation in maternal investment : Acidity affects egg size and fecundity in Rana arvalis
- 2008
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In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 89:9, s. 2553-2562
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Journal article (peer-reviewed)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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| 7. |
- Sorensen, Jesper Givskov, et al.
(author)
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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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In: Journal of Thermal Biology. - : Elsevier BV. - 0306-4565 .- 1879-0992. ; 34:1, s. 49-54
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Journal article (peer-reviewed)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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