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Thomas A White - One of the best experts on this subject based on the ideXlab platform.
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genomic and morphological analysis of a semipermeable avian hybrid zone suggests asymmetrical introgression of a sexual signal
Evolution, 2014Co-Authors: Daniel T Baldassarre, Thomas A White, Jordan Karubian, Michael S WebsterAbstract:Hybrid zones are geographic regions where differentiated taxa meet and potentially exchange genes. Increasingly, genomic analyses have demonstrated that many hybrid zones are semipermeable boundaries across which introgression is highly variable. In some cases, certain alleles penetrate across the hybrid zone in only one direction, recombining into the alternate genome. We investigated this phenomenon using genomic (genotyping-by-sequencing) and morphological (plumage reflectance spectrophotometry) analyses of the hybrid zone between two subspecies of the red-backed fairy-wren (Malurus melanocephalus) that differ conspicuously in a sexual signal, male back plumage color. Geographic Cline analyses revealed a highly variable pattern of differential introgression, with many narrow coincident Clines combined with several significantly wider Clines, suggesting that the hybrid zone is a semipermeable tension zone. The plumage Cline was shifted significantly into the genomic background of the orange subspecies, consistent with sexual selection driving asymmetrical introgression of red plumage alleles across the hybrid zone. This interpretation is supported by previous experimental work demonstrating an extra-pair mating advantage for red males, but the role of genetic dominance in driving this pattern remains unclear. This study highlights the potential for sexual selection to erode taxonomic boundaries and promote gene flow, particularly at an intermediate stage of divergence.
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phenotypic variation across chromosomal hybrid zones of the common shrew sorex araneus indicates reduced gene flow
PLOS ONE, 2013Co-Authors: David P Polly, Thomas A White, Nina Bulatova, N A Shchipanov, Svetlana Pavlova, Andrei V Polyakov, Vadim B Ilyashenko, Sergei S Onischenko, P M BorodinAbstract:Sorex araneus, the Common shrew, is a species with more than 70 karyotypic races, many of which form parapatric hybrid zones, making it a model for studying chromosomal speciation. Hybrids between races have reduced fitness, but microsatellite markers have demonstrated considerable gene flow between them, calling into question whether the chromosomal barriers actually do contribute to genetic divergence. We studied phenotypic Clines across two hybrid zones with especially complex heterozygotes. Hybrids between the Novosibirsk and Tomsk races produce chains of nine and three chromosomes at meiosis, and hybrids between the Moscow and Seliger races produce chains of eleven. Our goal was to determine whether phenotypes show evidence of reduced gene flow at hybrid zones. We used maximum likelihood to fit tanh Cline models to geometric shape data and found that phenotypic Clines in skulls and mandibles across these zones had similar centers and widths as chromosomal Clines. The amount of phenotypic differentiation across the zones is greater than expected if it were dissipating due to unrestricted gene flow given the amount of time since contact, but it is less than expected to have accumulated from drift during allopatric separation in glacial refugia. Only if heritability is very low, Ne very high, and the time spent in allopatry very short, will the differences we observe be large enough to match the expectation of drift. Our results therefore suggest that phenotypic differentiation has been lost through gene flow since post-glacial secondary contact, but not as quickly as would be expected if there was free gene flow across the hybrid zones. The chromosomal tension zones are confirmed to be partial barriers that prevent differentiated races from becoming phenotypically homogenous.
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Properties of a hybrid zone between highly distinct chromosomal races of the house mouse (Mus musculus domesticus) in Northern Italy, and comparisons with other hybrid zones.
Cytogenetic and genome research, 2011Co-Authors: Heidi C. Hauffe, Thomas A White, Mabel D. Giménez, Rodrigo Vega, Jeremy B SearleAbstract:Here we provide the first detailed description of the hybrid zone between the Cremona chromosomal race of house mouse (ICRE; 2n = 22) and the standard all-telocentric race (40ST; 2n = 40), with full karyotypes of 106 individuals from 17 localities along a transect between the 2 races to the west of Lake Garda in Northern Italy. The ICRE race is characterised by 9 pairs of metacentric chromosomes in a homozygous state and we use the metacentric frequency data along the transect to fit tanh metacentric Clines. The Clines are narrow (5-8 km, standardised width) suggesting low hybrid fitness. However, the lack of occurrence of ICRE × 40ST F(1) hybrids and presence of other hybrid types suggests that the F(1) hybrids initially produced in this hybrid zone were at least partially fertile, despite having 9 meiotic trivalent configurations. We apply the same Cline-fitting methodology to 3 previously studied hybrid zones between metacentric races and the 40ST race. Taken together with published clinal data on 4 further metacentric-40ST hybrid zones, we are able to make objective generalisations on the characteristics of such zones in the house mouse. Zones involving 22-chromosome races are narrower, on average, than other metacentric-40ST hybrid zones and do not show a tendency towards the generation of new races as found with zones where the metacentric race has a higher 2n. It appears that metacentric-40ST zones are unlikely to be sites of speciation (even when a 22-chromosome race is involved), although a mosaic structure to the hybrid zone may enhance this possibility. We make a comparison between metacentric-40ST zones and contacts between 2 metacentric races, for a comprehensive perspective of chromosomal hybrid zones in the house mouse.
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natural hybridization between extremely divergent chromosomal races of the common shrew sorex araneus soricidae soricomorpha hybrid zone in siberia
Journal of Evolutionary Biology, 2011Co-Authors: Nina Bulatova, Thomas A White, R M Jones, N A Shchipanov, Svetlana Pavlova, Jeremy B SearleAbstract:Chromosomal races of the common shrew differ in sets of metacentric chromosomes and on contact may produce hybrids with extraordinarily complex configurations at meiosis I that are associated with reduced fertility. There is an expectation that these may be some of the most extreme tension zones available for study and therefore are of interest as potential sites for reproductive isolation. Here, we analyse one of these zones, between the Novosibirsk race (characterized by metacentrics go, hn, ik, jl, mp and qr) and the Tomsk race (metacentrics gk, hi, jl and mn and acrocentrics o, p, q and r), which form hybrids with a chain-of-nine (CIX) and a chain-of-three (CIII) configuration at meiosis I. At the Novosibirsk-Tomsk hybrid zone, the CIX chromosomes form Clines of 8.53 km standardized width on average, whereas the Cline for the CIII chromosomes was 52.83 km wide. The difference in these Cline widths fits with the difference in meiotic errors expected with the CIX and CIII configuration, and we produce estimates of selection against hybrids with these types of configurations, which we relate to dispersal and age of the hybrid zone. The hybrid zone is located at the isoCline at 200 m altitude above sea level; this relationship between the races and altitude is suggested at both coarse and fine scales. This indicates adaptive differences between the races that may in turn have been promoted by the chromosome differences. Thus, the extreme chromosomal divergence between the Novosibirsk and Tomsk may be associated with genic differentiation, but it is still striking that, despite the large chromosomal differences, reproductive isolation between the Novosibirsk and Tomsk races has not occurred.
Patricia M Schulte - One of the best experts on this subject based on the ideXlab platform.
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steep coincident and concordant Clines in mitochondrial and nuclear encoded genes in a hybrid zone between subspecies of atlantic killifish fundulus heteroclitus
Ecology and Evolution, 2016Co-Authors: Jessica L Mckenzie, Rashpal S Dhillon, Patricia M SchulteAbstract:Steep genetic Clines resulting from recent secondary contact between previously isolated taxa can either gradually erode over time or be stabilized by factors such as ecological selection or selection against hybrids. We used patterns of variation in 30 nuclear and two mitochondrial SNPs to examine the factors that could be involved in stabilizing Clines across a hybrid zone between two subspecies of the Atlantic killifish, Fundulus heteroclitus. Increased heterozygote deficit and cytonuclear disequilibrium in populations near the center of the mtDNA Cline suggest that some form of reproductive isolation such as assortative mating or selection against hybrids may be acting in this hybrid zone. However, only a small number of loci exhibited these signatures, suggesting locus-specific, rather than genomewide, factors. Fourteen of the 32 loci surveyed had Cline widths inconsistent with neutral expectations, with two SNPs in the mitochondrial genome exhibiting the steepest Clines. Seven of the 12 putatively non-neutral nuclear Clines were for SNPs in genes related to oxidative metabolism. Among these putatively non-neutral nuclear Clines, SNPs in two nuclear-encoded mitochondrial genes (SLC25A3 and HDDC2), as well as SNPs in the myoglobin, 40S ribosomal protein S17, and actin-binding LIM protein genes, had Clines that were coincident and concordant with the mitochondrial Clines. When hybrid index was calculated using this subset of loci, the frequency distribution of hybrid indices for a population located at the mtDNA Cline center was non-unimodal, suggesting selection against advanced-generation hybrids, possibly due to effects on processes involved in oxidative metabolism.
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Cline coupling and uncoupling in a stickleback hybrid zone
Evolution, 2016Co-Authors: Timothy H Vines, Patricia M Schulte, Anne C Dalziel, Arianne Albert, Thor Veen, Dolph SchluterAbstract:Strong ecological selection on a genetic locus can maintain allele frequency differences between populations in different environments, even in the face of hybridization. When alleles at divergent loci come into tight linkage disequilibrium, selection acts on them as a unit and can significantly reduce gene flow. For populations interbreeding across a hybrid zone, linkage disequilibria between loci can force Clines to share the same slopes and centers. However, strong ecological selection on a locus can also pull its Cline away from the others, reducing linkage disequilibrium and weakening the barrier to gene flow. We looked for this "Cline uncoupling" effect in a hybrid zone between stream resident and anadromous sticklebacks at two genes known to be under divergent natural selection (Eda and ATP1a1) and five morphological traits that repeatedly evolve in freshwater stickleback. These Clines were all steep and located together at the top of the estuary, such that we found no evidence for Cline uncoupling. However, we did not observe the stepped shape normally associated with steep concordant Clines. It thus remains possible that these Clines cluster together because their individual selection regimes are identical, but this would be very surprising given their diverse roles in osmoregulation, body armor, and swimming performance.
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evidence for a bimodal distribution of hybrid indices in a hybrid zone with high admixture
Royal Society Open Science, 2015Co-Authors: Jessica L Mckenzie, Rashpal S Dhillon, Patricia M SchulteAbstract:The genetic structure of a hybrid zone can provide insights into the relative roles of the various factors that maintain the zone. Here, we use a multilocus approach to characterize a hybrid zone between two subspecies of killifish (Fundulus heteroclitus, Walbaum 1792) found along the Atlantic coast of North America. We first analysed clinal variation along the Atlantic coast using a single-nucleotide polymorphism in the mitochondrial DNA (mtDNA) displacement loop (D-loop) and a panel of nine nuclear microsatellite markers. A model constraining all Clines to the same width and centre was not significantly different from a model in which the Clines were allowed to vary independently. Locus-by-locus analysis indicated that the majority of nuclear Clines shared the same centre as the mtDNA Cline, and the widths of these Clines were also narrower than that predicted by a neutral model, suggesting that selection is operating to maintain the hybrid zone. However, two of the nuclear Clines had widths greater than the neutral prediction and had centres that were displaced relative to the mtDNA Cline centre. We also found that a marsh located near the centre of the mtDNA Cline demonstrated a bimodal distribution of nuclear hybrid index values, suggesting a deficit of first-generation hybrids and backcrossed genotypes. Thus, selection against hybrid genotypes may be playing a role in maintaining this hybrid zone and the associated steep nuclear and mtDNA Clines.
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Cline coupling and uncoupling in a stickleback hybrid zone
bioRxiv, 2015Co-Authors: Timothy H Vines, Patricia M Schulte, Anne C Dalziel, Arianne Albert, Thor Veen, Dolph SchluterAbstract:Strong ecological selection on a genetic locus can maintain allele frequency differences between populations in different environments, even in the face of hybridization. When alleles at divergent loci come into tight linkage disequilibria, selection acts on them as a unit and can significantly reduce gene flow. For populations interbreeding across a hybrid zone, linkage disequilibria between loci can force Clines to share the same slopes and centers. However, strong ecological selection can push Clines away from the others, reducing linkage disequilibria and weakening the barrier to gene flow. We looked for this ‘Cline uncoupling’ effect in a hybrid zone between stream resident and anadromous sticklebacks at two genes known to be under divergent natural selection (Eda and ATP1a1) and five morphological traits that repeatedly evolve in freshwater stickleback. We used 10 anonymous SNPs to characterize the shape of the zone. We found that the Clines at Eda, ATP1a1, and four morphological traits were concordant and coincident, suggesting that direct selection on each is outweighed by the indirect selection generated by linkage disequilibria. Interestingly, the Cline for pectoral fin length was much steeper and displaced 200m downstream, and two anonymous SNPs also had steep Clines.
Roger K. Butlin - One of the best experts on this subject based on the ideXlab platform.
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testing an hypothesis of hybrid zone movement for toads in france
Molecular Ecology, 2019Co-Authors: Ben Wielstra, Roger K. Butlin, Isolde Van Riemsdijk, Jan W. ArntzenAbstract:Hybrid zone movement may result in substantial unidirectional introgression of selectively neutral material from the local to the advancing species, leaving a genetic footprint. This genetic footprint is represented by a trail of asymmetric tails and displaced Cline centres in the wake of the moving hybrid zone. A peak of admixture linkage disequilibrium is predicted to exist ahead of the centre of the moving hybrid zone. We test these predictions of the movement hypothesis in a hybrid zone between common (Bufo bufo) and spined toads (B. spinosus), using 31 nuclear and one mtDNA SNPs along a transect in the northwest of France. Average effective selection in Bufo hybrids is low and Clines vary in shape and centre. A weak pattern of asymmetric introgression is inferred from Cline discordance of seven nuclear markers. The dominant direction of gene flow is from B. spinosus to B. bufo and is in support of southward movement of the hybrid zone. Conversely, a peak of admixture linkage disequilibrium north of the hybrid zone suggests northward movement. These contrasting results can be explained by reproductive isolation of the B. spinosus and B. bufo gene pools at the southern (B. spinosus) side of the hybrid zone. The joint occurrence of asymmetric introgression and admixture linkage disequilibrium can also be explained by the combination of low dispersal and random genetic drift due to low effective population sizes.
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habitat association and seasonality in a mosaic and bimodal hybrid zone between chorthippus brunneus and c jacobsi orthoptera acrididae
PLOS ONE, 2012Co-Authors: Richard I Bailey, C I Saldamandobenjumea, Haruki Tatsuta, Roger K. ButlinAbstract:Understanding why some hybrid zones are bimodal and others unimodal can aid in identifying barriers to gene exchange following secondary contact. The hybrid zone between the grasshoppers Chorthippus brunneus and C. jacobsi contains a mix of allopatric parental populations and inter-mingled bimodal and unimodal sympatric populations, and provides an ideal system to examine the roles of local selection and gene flow between populations in maintaining bimodality. However, it is first necessary to confirm, over a larger spatial scale, previously identified associations between population composition and season and habitat. Here we use Cline-fitting of one morphological and one song trait along two valley transects, and intervening mountains, to confirm previously identified habitat associations (mountain versus valley) and seasonal changes in population composition. As expected from previous findings of studies on a smaller spatial scale, C. jacobsi dominated mountain habitats and mixed populations dominated valleys, and C. brunneus became more prevalent in August. Controlling for habitat and incorporating into the analysis seasonal changes in Cline parameters and the standard errors of parental trait values revealed wider Clines than previous studies (best estimates of 6.4 to 24.5 km in our study versus 2.8 to 4.7 km in previous studies) and increased percentage of trait variance explained (52.7% and 61.5% for transects 1 and 2 respectively, versus 17.6%). Revealing such strong and consistent patterns within a complex hybrid zone will allow more focused examination of the causes of variation in bimodality in mixed populations, in particular the roles of local selection versus habitat heterogeneity and gene flow between differentiated populations.
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genetic analysis of a chromosomal hybrid zone in the australian morabine grasshoppers vandiemenella viatica species group
Evolution, 2009Co-Authors: Roger K. Butlin, Takeshi Kawakami, Mark Adams, David Paull, Steven J B CooperAbstract:Whether chromosomal rearrangements promote speciation by providing barriers to gene exchange between populations is one of the long-standing debates in evolutionary biology. This question can be addressed by studying patterns of gene flow and selection in hybrid zones between chromosomally diverse taxa. Here we present results of the first study of the genetic structure of a hybrid zone between chromosomal races of morabine grasshoppers Vandiemenella viatica, P24(XY) and viatica17, on Kangaroo Island, Australia. Chromosomal and 11 nuclear markers revealed a narrow hybrid zone with strong linkage disequilibrium and heterozygote deficits, most likely maintained by a balance between dispersal and selection. Widths and positions of Clines for these markers are concordant and coincident, suggesting that selection is unlikely to be concentrated on a few chromosomes. In contrast, a mitochondrial marker showed a significantly wider Cline with centre offset toward the P24(XY) side. We argue that the discordance between the mitochondrial and nuclear/chromosomal Clines and overall asymmetry of the Clines suggest a secondary origin of the contact zone and potential movement of the zone after contact. Genome-wide scans using many genetic markers and chromosomal mapping of these markers are needed to investigate whether chromosomal differences directly reduce gene flow after secondary contact.
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adaptation to a steep environmental gradient and an associated barrier to gene exchange in littorina saxatilis
Evolution, 2006Co-Authors: J Grahame, Craig S Wilding, Roger K. ButlinAbstract:Steep environmental gradients offer important opportunities to study the interaction between natural se- lection and gene flow. Allele frequency Clines are expected to form at loci under selection, but unlinked neutral alleles may pass easily across these Clines unless a generalized barrier evolves. Here we consider the distribution of forms of the intertidal gastropod Littorina saxatilis, analyzing shell shape and amplified fragment length polymorphism (AFLP) loci on two rocky shores in Britain. On the basis of previous work, the AFLP loci were divided into differentiated and undifferentiated groups. On both shores, we have shown a sharp Cline in allele frequencies between the two morphs for differentiated AFLP loci. This is coincident with a habitat transition on the shore where the two habitats (cliff and boulder field) are immediately contiguous. The allele frequency Clines coincide with a Cline in shell mor- phology. In the middle of the Cline, linkage disequilibrium for the differentiated loci rises in accordance with expec- tation. The Clines are extremely narrow relative to dispersal, probably as a result of both strong selection and habitat choice. An increase in FST for undifferentiated AFLPs between morphs, relative to within-morph comparisons, is consistent with there being a general barrier to gene flow across the contact zone. These features are consistent either with an episode of allopatric divergence followed by secondary contact or with primary, nonallopatric divergence. Further data will be needed to distinguish between these alternatives.
Jessica L Mckenzie - One of the best experts on this subject based on the ideXlab platform.
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steep coincident and concordant Clines in mitochondrial and nuclear encoded genes in a hybrid zone between subspecies of atlantic killifish fundulus heteroclitus
Ecology and Evolution, 2016Co-Authors: Jessica L Mckenzie, Rashpal S Dhillon, Patricia M SchulteAbstract:Steep genetic Clines resulting from recent secondary contact between previously isolated taxa can either gradually erode over time or be stabilized by factors such as ecological selection or selection against hybrids. We used patterns of variation in 30 nuclear and two mitochondrial SNPs to examine the factors that could be involved in stabilizing Clines across a hybrid zone between two subspecies of the Atlantic killifish, Fundulus heteroclitus. Increased heterozygote deficit and cytonuclear disequilibrium in populations near the center of the mtDNA Cline suggest that some form of reproductive isolation such as assortative mating or selection against hybrids may be acting in this hybrid zone. However, only a small number of loci exhibited these signatures, suggesting locus-specific, rather than genomewide, factors. Fourteen of the 32 loci surveyed had Cline widths inconsistent with neutral expectations, with two SNPs in the mitochondrial genome exhibiting the steepest Clines. Seven of the 12 putatively non-neutral nuclear Clines were for SNPs in genes related to oxidative metabolism. Among these putatively non-neutral nuclear Clines, SNPs in two nuclear-encoded mitochondrial genes (SLC25A3 and HDDC2), as well as SNPs in the myoglobin, 40S ribosomal protein S17, and actin-binding LIM protein genes, had Clines that were coincident and concordant with the mitochondrial Clines. When hybrid index was calculated using this subset of loci, the frequency distribution of hybrid indices for a population located at the mtDNA Cline center was non-unimodal, suggesting selection against advanced-generation hybrids, possibly due to effects on processes involved in oxidative metabolism.
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evidence for a bimodal distribution of hybrid indices in a hybrid zone with high admixture
Royal Society Open Science, 2015Co-Authors: Jessica L Mckenzie, Rashpal S Dhillon, Patricia M SchulteAbstract:The genetic structure of a hybrid zone can provide insights into the relative roles of the various factors that maintain the zone. Here, we use a multilocus approach to characterize a hybrid zone between two subspecies of killifish (Fundulus heteroclitus, Walbaum 1792) found along the Atlantic coast of North America. We first analysed clinal variation along the Atlantic coast using a single-nucleotide polymorphism in the mitochondrial DNA (mtDNA) displacement loop (D-loop) and a panel of nine nuclear microsatellite markers. A model constraining all Clines to the same width and centre was not significantly different from a model in which the Clines were allowed to vary independently. Locus-by-locus analysis indicated that the majority of nuclear Clines shared the same centre as the mtDNA Cline, and the widths of these Clines were also narrower than that predicted by a neutral model, suggesting that selection is operating to maintain the hybrid zone. However, two of the nuclear Clines had widths greater than the neutral prediction and had centres that were displaced relative to the mtDNA Cline centre. We also found that a marsh located near the centre of the mtDNA Cline demonstrated a bimodal distribution of nuclear hybrid index values, suggesting a deficit of first-generation hybrids and backcrossed genotypes. Thus, selection against hybrid genotypes may be playing a role in maintaining this hybrid zone and the associated steep nuclear and mtDNA Clines.
Carla M Sgro - One of the best experts on this subject based on the ideXlab platform.
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the effect of developmental temperature on the genetic architecture underlying size and thermal Clines in drosophila melanogaster and d simulans from the east coast of australia
Evolution, 2011Co-Authors: Belinda Van Heerwaarden, Carla M SgroAbstract:Body size and thermal tolerance Clines in Drosophila melanogaster occur along the east coast of Australia. However the extent to which temperature affects the genetic architecture underlying the observed clinal divergence remains unknown. Clinal variation in these traits is associated with cosmopolitan chromosome inversions that Cline in D. melanogaster. Whether this association influences the genetic architecture for these traits in D. melanogaster is unclear. Drosophila simulans shows linear Clines in body size, but nonlinear Clines in cold resistance. Clinally varying inversions are absent in D. simulans. Line-cross and clinal analyses were performed between tropical and temperate populations of D. melanogaster and D. simulans from the east coast of Australia to investigate whether clinal patterns and genetic effects contributing to clinal divergence in wing centroid size, thorax length, wing-to-thorax ratio, cold and heat resistance differed under different developmental temperatures (18 °C, 25 °C, and 29 °C). Developmental temperature influenced the genetic architecture in both species. Similarities between D. melanogaster and D. simulans suggest clinally varying inversion polymorphisms have little influence on the genetic architecture underlying clinal divergence in size in D. melanogaster. Differing genetic architectures across different temperatures highlight the need to consider different environments in future evolutionary and molecular studies of phenotypic divergence.
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a comprehensive assessment of geographic variation in heat tolerance and hardening capacity in populations of drosophila melanogaster from eastern australia
Journal of Evolutionary Biology, 2010Co-Authors: Carla M Sgro, Johannes Overgaard, Torsten Nygard Kristensen, Kathrine A Mitchell, Fiona Elizabeth Cockerell, Ary A HoffmannAbstract:We examined latitudinal variation in adult and larval heat tolerance in Drosophila melanogaster from eastern Australia. Adults were assessed using static and ramping assays. Basal and hardened static heat knockdown time showed significant linear Clines; heat tolerance increased towards the tropics, particularly for hardened flies, suggesting that tropical populations have a greater hardening response. A similar pattern was evident for ramping heat knockdown time at 0.06 °C min−1 increase. There was no Cline for ramping heat knockdown temperature (CTmax) at 0.1 °C min−1 increase. Acute (static) heat knockdown temperature increased towards temperate latitudes, probably reflecting a greater capacity of temperate flies to withstand sudden temperature increases during summer in temperate Australia. Larval viability showed a quadratic association with latitude under heat stress. Thus, patterns of heat resistance depend on assay methods. Genetic correlations in thermotolerance across life stages and evolutionary potential for critical thermal limits should be the focus of future studies.
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investigating latitudinal Clines for life history and stress resistance traits in drosophila simulans from eastern australia
Journal of Evolutionary Biology, 2008Co-Authors: Aston L Arthur, Anton Weeks, Carla M SgroAbstract:Latitudinal Clines have been demonstrated for many quantitative traits in Drosophila and are assumed to be due to climatic selection. However, clinal studies are often performed in species of Drosophila that contain common cosmopolitan inversion polymorphisms that also show clinal patterns. These inversion polymorphisms may be responsible for much of the observed clinal variation. Here, we consider latitudinal Clines for quantitative traits in Drosophila simulans from eastern Australia. Drosophila simulans does not contain cosmopolitan inversion polymorphisms, so allows the study of clinal selection on quantitative traits that are not confounded by associations with inversions. Body size showed a strong linear Cline for both females and males. Starvation resistance exhibited a weak linear Cline in females, whereas chill-coma recovery exhibited a significant nonlinear Cline in females only. No clinal pattern was evident for development time, male chill-coma recovery, desiccation or heat resistance. We discuss these results with reference to the role inversion polymorphisms play in generating Clines in quantitative traits of Drosophila.