Browsing by Subject "3-SPINED STICKLEBACK"

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  • Shikano, Takahito; Laine, Veronika N.; Herczeg, Gabor; Vilkki, Johanna; Merilä, Juha (2013)
  • Johnson, Sini; Candolin, Ulrika (2017)
    Much evidence exists for sexually selected traits reflecting various components of mate quality, but the factors that limit signal expression and ensure honest signaling are less well known. Predation risk has been proposed to be one factor that could constrain the elaboration of visually conspicuous signals and ensure honesty, but little evidence exists because of limitations of earlier used methods. We investigated using a combination of field observations and experimental work if a conspicuous sexual signal of the threespine stickleback Gasterosteus aculeatus, the red nuptial coloration of the male, increases predation risk. We compared the proportion of colorful males in the gut of a predator in the wild, the perch Perca fluviatilis, to that in the population, and found proportionally more red-colored stickleback in the gut. This indicates that the predator selectively preys on colorful males under natural conditions. To differentiate between the effects of color and behavior on susceptibility to predation, we experimentally investigated the attack behavior of the predator towards breeding stickleback males differing in coloration. We found the predator to preferentially attack more colorful males, independent of their behavior. These results indicate that predation risk is a cost of the sexual signal that could limit expression and influence the honesty of the signal as an indicator of mate quality
  • Yang, Jing; Guo, Baocheng; Shikano, Takahito; Liu, Xiaolin; Merilä, Juha (2016)
    Heritable phenotypic differences between populations, caused by the selective effects of distinct environmental conditions, are of commonplace occurrence in nature. However, the actual genomic targets of this kind of selection are still poorly understood. We conducted a quantitative trait locus (QTL) mapping study to identify genomic regions responsible for morphometric differentiation between genetically and phenotypically divergent marine and freshwater nine-spined stickleback (Pungitius pungitius) populations. Using a dense panel of SNP-markers obtained by restriction site associated DNA sequencing of an F-2 recombinant cross, we found 22 QTL that explained 3.5-12.9% of phenotypic variance in the traits under investigation. We detected one fairly large-effect (PVE = 9.6%) QTL for caudal peduncle length-a trait with a well-established adaptive function showing clear differentiation among marine and freshwater populations. We also identified two large-effect QTL for lateral plate numbers, which are different from the lateral plate QTL reported in earlier studies of this and related species. Hence, apart from identifying several large-effect QTL in shape traits showing adaptive differentiation in response to different environmental conditions, the results suggest intra-and interspecific heterogeneity in the genomic basis of lateral plate number variation.
  • Pritchard, Victoria L.; Viitaniemi, Heidi M.; McCairns, R. J. Scott; Merila, Juha; Nikinmaa, Mikko; Primmer, Craig R.; Leder, Erica H. (2017)
    Much adaptive evolutionary change is underlain by mutational variation in regions of the genome that regulate gene expression rather than in the coding regions of the genes themselves. An understanding of the role of gene expression variation in facilitating local adaptation will be aided by an understanding of underlying regulatory networks. Here, we characterize the genetic architecture of gene expression variation in the threespine stickleback (Gasterosteus aculeatus), an important model in the study of adaptive evolution. We collected transcriptomic and genomic data from 60 half-sib families using an expression microarray and genotyping-by-sequencing, and located expression quantitative trait loci (eQTL) underlying the variation in gene expression in liver tissue using an interval mapping approach. We identified eQTL for several thousand expression traits. Expression was influenced by polymorphism in both cis- and trans-regulatory regions. Transe-QTL clustered into hotspots. We did not identify master transcriptional regulators in hotspot locations: rather, the presence of hotspots may be driven by complex interactions between multiple transcription factors. One observed hotspot colocated with a QTL recently found to underlie salinity tolerance in the threespine stickleback. However, most other observed hotspots did not colocate with regions of the genome known to be involved in adaptive divergence between marine and freshwater habitats.
  • Morozov, Sergey; Leinonen, Tuomas; Merilä, Juha; McCairns, R. J. Scott (2018)
    Conspecifics inhabiting divergent environments frequently differ in morphology, physiology, and performance, but the interrelationships amongst traits and with Darwinian fitness remains poorly understood. We investigated population differentiation in morphology, metabolic rate, and swimming performance in three-spined sticklebacks (Gasterosteus aculeatus L.), contrasting a marine/ancestral population with two distinct freshwater morphotypes derived from it: the typical low-plated morph, and a unique small-plated morph. We test the hypothesis that similar to plate loss in other freshwater populations, reduction in lateral plate size also evolved in response to selection. Additionally, we test how morphology, physiology, and performance have evolved in concert as a response to differences in selection between marine and freshwater environments. We raised pure-bred second-generation fish originating from three populations and quantified their lateral plate coverage, burst- and critical swimming speeds, as well as standard and active metabolic rates. Using a multivariate Q(ST)-F-ST framework, we detected signals of directional selection on metabolic physiology and lateral plate coverage, notably demonstrating that selection is responsible for the reduction in lateral plate coverage in a small-plated stickleback population. We also uncovered signals of multivariate selection amongst all bivariate trait combinations except the two metrics of swimming performance. Divergence between the freshwater and marine populations exceeded neutral expectation in morphology and in most physiological and performance traits, indicating that adaptation to freshwater habitats has occurred, but through different combinations of traits in different populations. These results highlight both the complex interplay between morphology, physiology and performance in local adaptation, and a framework for their investigation.
  • Hasan, M. Mehedi; De Faveri, Jacquelin; Kuure, Satu; Dash, Surjya N.; Lehtonen, Sanna; Merila, Juha; McCairns, R. J. Scott (2017)
    Novel physiological challenges in different environments can promote the evolution of divergent phenotypes, either through plastic or genetic changes. Environmental salinity serves as a key barrier to the distribution of nearly all aquatic organisms, and species diversification is likely to be enabled by adaptation to alternative osmotic environments. The threespine stickleback (Gasterosteus aculeatus) is a euryhaline species with populations found both in marine and freshwater environments. It has evolved both highly plastic and locally adapted phenotypes due to salinity-derived selection, but the physiological and genetic basis of adaptation to salinity is not fully understood. We integrated comparative cellular morphology of the kidney, a key organ for osmoregulation, and candidate gene expression to explore the underpinnings of evolved variation in osmotic plasticity within two populations of sticklebacks from distinct salinity zones in the Baltic Sea: the high salinity Kattegat, representative of the ancestral marine habitat; and the low salinity Bay of Bothnia. A common-garden experiment revealed that kidney morphology in the ancestral high-salinity population had a highly plastic response to salinity conditions whereas this plastic response was reduced in the low-salinity population. Candidate gene expression in kidney tissue revealed a similar pattern of population specific differences, with a higher degree of plasticity in the native high-salinity population. Together these results suggest that renal cellular morphology has become canalized to low salinity, and that these structural differences may have functional implications for osmoregulation.