| 41. |
- 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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| 42. |
- Hettyey, Attila, et al.
(författare)
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Interactions between the information content of different chemical cues affect induced defences in tadpoles
- 2010
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 119:11, s. 1814-1822
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Tidskriftsartikel (refereegranskat)abstract
- Animals often alter their behaviour, morphology and physiology in the presence of predators. These induced defences can be fine-tuned by a variety of environmental factors such as predator species, acute predation risk or food availability. It has, however, remained unclear what cues influence the extent and quality of induced defences and how the information content of these cues interact to determine the development of antipredator defences. We performed an experiment to study the significance of direct chemical cues, originating from the predators themselves, and indirect cues, released by attacked or consumed prey, for phenotypic responses in Rana dalmatina tadpoles. We reared tadpoles in the presence of caged predators (Triturus vulgaris, Aeshna cyanea) fed either one or three tadpoles every other day outside the tadpole-rearing tanks. Fifteen hours after food provisioning, predators were put back into the tanks containing focal tadpoles either after washing (direct + digestion-released cues) or with the water containing remnants of the prey (direct + all types of indirect cues). Our results suggest that direct cues together with digestion-released cues can be sufficient to induce strong antipredator responses. Induced defences depended on both direct cues, affecting predator-specific responses, and the quantity of indirect cues, resulting in graded responses to differences in predation threat. Moreover, direct and indirect cues interacted in behaviour, resulting in predator-specific graded responses. We also observed a decrease in the extent of predator-induced responses in large tadpoles as compared to small ones. Our results, thus, suggest that prey integrate multiple cues about predators to optimize induced defences and that this process changes during ontogeny.
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| 43. |
- Hjernquist, Mårten B., et al.
(författare)
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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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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 170:3, s. 641-649
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Tidskriftsartikel (refereegranskat)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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| 44. |
- Höglund, Jacob, et al.
(författare)
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Low neutral and immunogenetic diversity in northern fringe populations of the green toad Bufotes viridis : implications for conservation
- 2022
-
Ingår i: Conservation Genetics. - : Springer Nature. - 1566-0621 .- 1572-9737. ; 23, s. 139-149
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Tidskriftsartikel (refereegranskat)abstract
- Genetic variation is often lower at high latitudes, which may compromise the adaptability and hence survival of organisms. Here we show that genetic variability is negatively correlated with northern latitude in European green toads (Bufotes viridis). The result holds true for both putatively neutral microsatellite variation and supposedly adaptive MHC Class IIB variation. In particular, our findings have bearing on the conservation status of this species in Sweden, on the northern limit of its distribution where local populations are small and fragmented. These genetically impoverished populations are closely related to other populations found around the Baltic Sea basin. The low neutral and adaptive variation in these fringe populations compared to population at central ranges confirms a pattern shared across all other amphibians so far studied. In Sweden, the situation of green toads is of concern as the remaining populations may not have the evolutionary potential to cope with present and future environmental challenges.
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| 45. |
- Jelena, Mausbach, et al.
(författare)
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Context dependent variation in corticosterone and phenotypic divergence of Rana arvalis populations along an acidification gradient
- 2022
-
Ingår i: BMC Ecology and Evolution. - : Springer Nature. - 2730-7182. ; 22:1
-
Tidskriftsartikel (refereegranskat)abstract
- Physiological processes, as immediate responses to the environment, are important mechanisms of phenotypic plasticity and can influence evolution at ecological time scales. In stressful environments, physiological stress responses of individuals are initiated and integrated via the release of hormones, such as corticosterone (CORT). In vertebrates, CORT influences energy metabolism and resource allocation to multiple fitness traits (e.g. growth and morphology) and can be an important mediator of rapid adaptation to environmental stress, such as acidification. The moor frog, Rana arvalis, shows adaptive divergence in larval life-histories and predator defense traits along an acidification gradient in Sweden. Here we take a first step to understanding the role of CORT in this adaptive divergence. We conducted a fully factorial laboratory experiment and reared tadpoles from three populations (one acidic, one neutral and one intermediate pH origin) in two pH treatments (Acid versus Neutral pH) from hatching to metamorphosis. We tested how the populations differ in tadpole CORT profiles and how CORT is associated with tadpole life-history and morphological traits.
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| 46. |
- Johansson, Magnus
(författare)
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Adjusting to the extreme : Thermal adaptation in a freshwater gastropod
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Temperature is a ubiquitous force influencing biological processes ranging from cellular responses to life span. The thermal environment for many organisms is predicted to change with globally increasing temperatures and studies conducted in natural systems incorporating various evolutionary forces, such as gene flow, is needed. In my thesis, I investigate how snails (Radix balthica) originating from distinct geothermal environments within Lake Mývatn in northern Iceland have adapted, both genetically and phenotypically, to the respective thermal regime. Locations were classified as either cold, warm or seasonal depending on the average and variance in temperature. A high resolution spatial distribution of genetic variation within Mývatn was obtained using both neutral and outlier AFLPs. In addition, the genetic profile enabled me identify warm origin snails irrespective of geographic location in Iceland. Warm environments were often more stressful than cold or seasonal environments but snails originating from a high temperature location benefited from increased performance elsewhere. Patterns of growth were identical in both common garden and reciprocal transplant experiment; warm origin snails grew faster than both cold and seasonal origin snails. This result is in concordance with quantitative genetics models of thermal adaptation but suggesting cogradient rather than countergradient variation. Although warm origin snails generally had superior performance, survival at cold temperatures (< 12 °C) was reduced. All snails matured at similar size in the common garden experiment but cold origin snails were observed to mature later and lay fewer eggs. Also, snails had a common optimum for growth rate at 20 °C irrespective of thermal origin. This is arguably the reason why snails were observed to have a common thermal preference. Interestingly, warm origin snails had a reduced tolerance to high temperatures compared to cold and seasonal origin snails which did not differ in tolerance. Putatively, natural selection has reduced a putatively unnecessary trait (high temperature tolerance in a stable thermal environment) in favour of higher growth rate and performance in warm habitats. In conclusion, the price of high performance in a warm environment was paid in terms of reduced survival at low temperatures and a potential disadvantage of reduced genetic variability.
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| 47. |
- Johansson, Markus, 1974-
(författare)
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Effects of Agriculture on Abundance, Genetic Diversity and Fitness in the Common Frog, Rana temporaria
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aims of this thesis were to evaluate the effects of agriculture on amphibians in terms of (i) population genetic consequences of agriculture-induced spatial changes of the landscape and (ii) local adaptation and tolerance to frequently used agrochemicals. The study was performed using the common frog Rana temporaria as a model. Abundance, occurrence, genetic diversity and gene flow were negatively affected by agriculture in southern Sweden, but unaffected or even positively affected by agriculture in the central and northern regions, respectively. These test parameters correlated positively with landscape diversity both in the south and in the north. Moreover, the size and occurrence of R. temporaria populations decreased towards the north i.e. the margin of the species’ distribution range. In accordance with theoretical expectations, genetic variability decreased and population substructuring increased as a negative function of (effective) population size. Southern Swedish common frogs are naturally exposed to higher levels of nitrates, and thus have a higher tolerance to high nitrate levels than their northern conspecifics. This suggests local adaptation to naturally varying nitrate levels. Consequently, increased anthropogenic supplementation of nitrate could impact more the northern than the southern Swedish common frog populations. Exposure to the pesticides azoxystrobin, cyanazine and permethrin at ecologically relevant concentrations had small or no effects on R. temporaria tadpoles. The populations with lowest microsatellite variation (fragmented populations) in southern Sweden had considerably lower fitness in terms of survival and growth as compared to those with the highest genetic variability (non-fragmented populations). The results indicate that populations with low levels of neutral genetic variability were phenotypically less differentiated than populations with higher levels of variability. One possible explanation for this is that the degree of population differentiation in low variability populations has been constrained due to lack of suitable genetic variation or inefficiency of selection relative to genetic drift.
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| 48. |
- Johansson, Magnus P., et al.
(författare)
-
Divergence of gastropod life history in contrasting thermal environments in a geothermal lake
- 2016
-
Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 29:10, s. 2043-2053
-
Tidskriftsartikel (refereegranskat)abstract
- Experiments using natural populations have provided mixed support for thermal adaptation models, probably because the conditions are often confounded with additional environmental factors like seasonality. The contrasting geothermal environments within Lake Myvatn, northern Iceland, provide a unique opportunity to evaluate thermal adaptation models using closely located natural populations. We conducted laboratory common garden and field reciprocal transplant experiments to investigate how thermal origin influences the life history of Radix balthica snails originating from stable cold (6 degrees C), stable warm (23 degrees C) thermal environments or from areas with seasonal temperature variation. Supporting thermal optimality models, warm-origin snails survived poorly at 6 degrees C in the common garden experiment and better than cold-origin and seasonal-origin snails in the warm habitat in the reciprocal transplant experiment. Contrary to thermal adaptation models, growth rate in both experiments was highest in the warm populations irrespective of temperature, indicating cogradient variation. The optimal temperatures for growth and reproduction were similar irrespective of origin, but cold-origin snails always had the lowest performance, and seasonal- origin snails often performed at an intermediate level compared to snails originating in either stable environment. Our results indicate that central life-history traits can differ in their mode of evolution, with survival following the predictions of thermal optimality models, whereas ecological constraints have shaped the evolution of growth rates in local populations.
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| 49. |
- Johansson, Magnus P., et al.
(författare)
-
Genetic divergence and isolation by thermal environment in geothermal populations of an aquatic invertebrate
- 2016
-
Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 29:9, s. 1701-1712
-
Tidskriftsartikel (refereegranskat)abstract
- Temperature is one of the most influential forces of natural selection impacting all biological levels. In the face of increasing global temperatures, studies over small geographic scales allowing investigations on the effects of gene flow are of great value for understanding thermal adaptation. Here, we investigated genetic population structure in the freshwater gastropod Radix balthica originating from contrasting thermal habitats in three areas of geothermal activity in Iceland. Snails from 32 sites were genotyped at 208 AFLP loci. Five AFLPs were identified as putatively under divergent selection in Lake Myvatn, a geothermal lake with an almost 20 degrees C difference in mean temperature across a distance of a few kilometres. In four of these loci, variation across all study populations was correlated with temperature. We found significant population structure in neutral markers both within and between the areas. Cluster analysis using neutral markers classified the sites mainly by geography, whereas analyses using markers under selection differentiated the sites based on temperature. Isolation by distance was stronger in the neutral than in the outlier loci. Pairwise differences based on outlier F-ST were significantly correlated with temperature at different spatial scales, even after correcting for geographic distance or neutral pairwise F-ST differences. In general, genetic variation decreased with increasing environmental temperature, possibly suggesting that natural selection had reduced the genetic diversity in the warm origin sites. Our results emphasize the influence of environmental temperature on the genetic structure of populations and suggest local thermal adaptation in these geothermal habitats.
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| 50. |
- Johansson, Magnus P., et al.
(författare)
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Maximum thermal tolerance trades off with chronic tolerance of high temperature in contrasting thermal populations of Radix balthica
- 2017
-
Ingår i: Ecology and Evolution. - : WILEY. - 2045-7758. ; 7:9, s. 3149-3156
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal adaptation theory predicts that thermal specialists evolve in environments with low temporal and high spatial thermal variation, whereas thermal generalists are favored in environments with high temporal and low spatial variation. The thermal environment of many organisms is predicted to change with globally increasing temperatures and thermal specialists are presumably at higher risk than thermal generalists. Here we investigated critical thermal maximum (CTmax) and preferred temperature (T-p) in populations of the common pond snail (Radix balthica) originating from a small-scale system of geothermal springs in northern Iceland, where stable cold (ca. 7 degrees C) and warm (ca. 23 degrees C) habitats are connected with habitats following the seasonal thermal variation. Irrespective of thermal origin, we found a common T-p for all populations, corresponding to the common temperature optimum (T-opt) for fitness-related traits in these populations. Warm-origin snails had lowest CTmax. As our previous studies have found higher chronic temperature tolerance in the warm populations, we suggest that there is a trade-off between high temperature tolerance and performance in other fitness components, including tolerance to chronic thermal stress. T-p and CTmax were positively correlated in warm-origin snails, suggesting a need to maintain a minimum "warming tolerance" (difference in CTmax and habitat temperature) in warm environments. Our results highlight the importance of high mean temperature in shaping thermal performance curves.
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