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- Bauerfeind, Stephanie S., et al.
(author)
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Geographic variation in responses of European yellow dung flies to thermal stress
- 2018
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In: Journal of Thermal Biology. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0306-4565 .- 1879-0992. ; 73, s. 41-49
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Journal article (peer-reviewed)abstract
- Climatic conditions can be very heterogeneous even over small geographic scales, and are believed to be major determinants of the abundance and distribution of species and populations. Organisms are expected to evolve in response to the frequency and magnitude of local thermal extremes, resulting in local adaptation. Using replicate yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae) populations from cold (northern Europe) and warm climates (southern Europe), we compared 1) responses to short-term heat and cold shocks in both sexes, 2) heat shock protein (Hsp70) expression in adults and eggs, and 3) female reproductive traits when facing short-term heat stress during egg maturation. Contrary to expectations, thermal traits showed minor geographic differentiation, with weak evidence for greater heat resistance of southern flies but no differentiation in cold resistance. Hsp70 protein expression was little affected by heat stress, indicating systemic rather than induced regulation of the heat stress response, possibly related to this fly group's preference for cold climes. In contrast, sex differences were pronounced: males (which are larger) endured hot temperatures longer, while females featured higher Hsp70 expression. Heat stress negatively affected various female reproductive traits, reducing first clutch size, overall reproductive investment, egg lipid content, and subsequent larval hatching. These responses varied little across latitude but somewhat among populations in terms of egg size, protein content, and larval hatching success. Several reproductive parameters, but not Hsp70 expression, exhibited heritable variation among full-sib families. Rather than large-scale clinal geographic variation, our study suggests some local geographic population differentiation in the ability of yellow dung flies to buffer the impact of heat stress on reproductive performance.
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- Bauerfeind, Stephanie S., et al.
(author)
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Replicated latitudinal clines in reproductive traits of European and North American yellow dung flies
- 2018
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 127:11, s. 1619-1632
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Journal article (peer-reviewed)abstract
- Geographic variation in phenotypic traits is commonly correlated with spatial variation in the environment, e.g. seasonality and mean temperature, providing evidence that natural selection generates such patterns. In particular, both body size and egg size of ectothermic animals are commonly larger in northern climates, and temperature induces plastic responses in both traits. Size-independent egg quality can also vary with latitude, though this is rarely investigated. For the widespread yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) we investigated whether there are latitudinal clines in reproductive traits (clutch size, egg size and egg composition), whether these clines are due to variation in body and/or egg size, and whether such clines replicate across independent experiments performed on different continents (North America and Europe). Egg size generally increased with latitude (especially in Europe), an effect largely explained by body size of the mother, while clutch size did not; overall reproductive effort thus increased with latitude. Both the absolute and relative (correcting for egg size) amount of egg protein increased with latitude, egg glycogen decreased with latitude, while latitudinal trends for egg lipids and total egg energy content were complex and non-linear. Altitude sometimes showed relationships analogous to those of latitude (egg proteins and glycogen) but occasionally opposite (egg size), possibly because latitude and altitude are negatively related among populations of this cold-adapted species. There was no evidence of a tradeoff between egg size and number across latitudinal populations; if anything, the relationship was positive. All traits, including body and egg size, varied with rearing temperature (12 degrees C, 18 degrees C, 24 degrees C), generally following the temperature-size rule. Clines based on common garden rearing, thus reflecting genetic differentiation, were qualitatively but not always quantitatively consistent between continents, and were similar across rearing temperatures, suggesting they evolved due to natural selection, although the concrete selective mechanisms involved require further study.
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- Blanckenhorn, Wolf U., et al.
(author)
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Life history traits, but not body size, vary systematically along latitudinal gradients on three continents in the widespread yellow dung fly
- 2018
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In: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 41:12, s. 2080-2091
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Journal article (peer-reviewed)abstract
- Large-scale clinal variation in body size and other life-history traits is common enough to have stimulated the postulation of several eco-geographical rules. Whereas some clinal patterns are clearly adaptive, the causes of others remain unclear. We present a comprehensive intraspecific population comparison for the cosmopolitan yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) to check for consistent world-wide patterns. Common garden assessment of various life history traits permitted continental comparison of (clinal) quantitative genetic differentiation (Qst) with putatively neutral genetic differentiation (Fst) derived from field-caught flies. Latitudinal clines in fly development time, growth rate, and overwintering propensity were consistent among North American, European and Japanese populations. Increased winter dormancy incidence and duration at higher latitude, combined with a faster growth rate and shorter development time, suggest that flies are adaptated to season length more than to temperature. The resulting body size clines, in contrast, were not very consistent; importantly, they were not negative, as expected under seasonal constraints, but flat or even positive clines. Quantitative genetic differentiation Q(ST) exceeded neutral molecular variation F-ST for most traits, suggesting that natural selection plays a consistent role in mediating global dung fly life histories. We conclude that faster growth and development in response to shorter growing seasons at higher latitudes may indirectly counteract expected direct effects of temperature on body-size, potentially resulting in flat or inconsistent body size clines in nature.
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- González-Tokman, Daniel, et al.
(author)
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Heritable responses to combined effects of heat stress and ivermectin in the yellow dung fly
- 2022
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 286
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Journal article (peer-reviewed)abstract
- In current times of global change, several sources of stress such as contaminants and high temperatures may act synergistically. The extent to which organisms persist in stressful conditions will depend on the fitness consequences of multiple simultaneously acting stressors and the genetic basis of compensatory genetic responses. Ivermectin is an antiparasitic drug used in livestock that is excreted in dung of treated cattle, causing severe negative consequences on non-target fauna. We evaluated the effect of a combination of heat stress and exposure to ivermectin in the yellow dung fly, Scathophaga stercoraria (Diptera: Scathophagidae). In a first experiment we investigated the effects of high rearing temperature on susceptibility to ivermectin, and in a second experiment we assayed flies from a latitudinal gradient to assess potential effects of local thermal adaptation on ivermectin sensitivity. The combination of heat and ivermectin synergistically reduced offspring survival, revealing severe effects of the two stressors when combined. However, latitudinal populations did not systematically vary in how ivermectin affected offspring survival, body size, development time, cold and heat tolerance. We also found very low narrow-sense heritability of ivermectin sensitivity, suggesting evolutionary constraints for responses to the combination of these stressors beyond immediate maternal or plastic effects. If the revealed patterns hold also for other invertebrates, the combination of increasing climate warming and ivermectin stress may thus have severe consequences for biodiversity. More generally, our study underlines the need for quantitative genetic analyses in understanding wildlife responses to interacting stressors that act synergistically and threat biodiversity.
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- Schäfer, Martin A., et al.
(author)
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Geographic clines in wing morphology relate to colonization history in New World but not Old World populations of yellow dung flies
- 2018
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In: Evolution. - : WILEY. - 0014-3820 .- 1558-5646. ; 72:8, s. 1629-1644
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Journal article (peer-reviewed)abstract
- Geographic dines offer insights about putative targets and agents of natural selection as well as tempo and mode of adaptation. However, demographic processes can lead to dines that are indistinguishable from adaptive divergence. Using the widespread yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae), we examine quantitative genetic differentiation (Q(ST)) of wing shape across North America, Europe, and Japan, and compare this differentiation with that of ten microsatellites (F-ST). Morphometric analyses of 28 populations reared at three temperatures revealed significant thermal plasticity, sexual dimorphism, and geographic differentiation in wing shape. In North America morphological differentiation followed the decline in microsatellite variability along the presumed route of recent colonization from the southeast to the northwest. Across Europe, where S. stercoraria presumably existed for much longer time and where no molecular pattern of isolation by distance was evident, clinal variation was less pronounced despite significant morphological differentiation (Q(ST) >F-ST). Shape vector comparisons further indicate that thermal plasticity (hot-to-cold) does not mirror patterns of latitudinal divergence (south-to-north), as might have been expected under a scenario with temperature as the major agent of selection. Our findings illustrate the importance of detailed phylogeographic information when interpreting geographic dines of dispersal traits in an adaptive evolutionary framework.
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