A Darwinian Laboratory of Multiple Contact Zones

Johannesson, Kerstin; Moan, Alan Le; Perini, Samuel; André, Carl

doi:10.1016/j.tree.2020.07.015

Cited by 81 publications

(94 citation statements)

References 108 publications

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“…It is interesting that this selection has had a strong and detectable effect on the genomic structure of these populations in a relatively short time. This has been described in a few other studies [50][51][52] . However, to our knowledge, this is the first case where predator and human pressures have been functionally linked with possible selection on loci involved in physiological functions that are directly involved with locomotor and escape behaviors.…”

Section: Discussionsupporting

confidence: 71%

Genomic signatures of drift and selection driven by predation and human pressure in an insular lizard

Bassitta

Brown

Pérez‐Cembranos

et al. 2021

Sci Rep

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Genomic divergence was studied in 10 small insular populations of the endangered Balearic Islands lizard (Podarcis lilfordi) using double digest restriction-site associated DNA sequencing. The objectives were to establish levels of divergence among populations, investigate the impact of population size on genetic variability and to evaluate the role of different environmental factors on local adaptation. Analyses of 72,846 SNPs supported a highly differentiated genetic structure, being the populations with the lowest population size (Porros, Foradada and Esclatasang islets) the most divergent, indicative of greater genetic drift. Outlier tests identified ~ 2% of loci as candidates for selection. Genomic divergence-Enviroment Association analyses were performed using redundancy analyses based on SNPs putatively under selection, detecting predation and human pressure as the environmental variables with the greatest explanatory power. Geographical distributions of populations and environmental factors appear to be fundamental drivers of divergence. These results support the combined role of genetic drift and divergent selection in shaping the genetic structure of these endemic island lizard populations.

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Section: Discussionsupporting

confidence: 71%

Genomic signatures of drift and selection driven by predation and human pressure in an insular lizard

Bassitta

Brown

Pérez‐Cembranos

et al. 2021

Sci Rep

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“…The Baltic Sea is a large body of brackish water which became connected to the North Sea about 8 kya. Its marine fauna has probably more than one origin, with evidence of populations and species in the Baltic Sea being the result of both primary and secondary divergence (reviewed in Johannesson et al ., 2020). The evolutionary origin of some specific taxa, such as the Baltic Sea populations of Pleuronectiformes, remains controversial (Jokinen et al ., 2019; Le Moan et al ., 2019; Momigliano et al ., 2017, 2018).…”

Section: Discussionmentioning

confidence: 99%

Biases in demographic modelling affect our understanding of recent divergence

Momigliano

Florin

Merilä

2020

Preprint

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Estimating patterns of gene flow during the early stages of speciation is central to understanding whether reproductive isolation arises via the gradual erosion of gene flow or through successive stages of strict isolation and secondary contact. Such scenarios can be explicitly tested by comparing the joint allele frequency spectrum (jAFS) of a set of populations to jAFS simulated under scenarios of isolation with migration (IM) and secondary contact (SC). However, the potential effect of unaccounted demographic events (such as population expansions and bottlenecks) on model choice and parameter estimation remains largely unexplored. Using simulations, we demonstrate that under realistic scenarios of population divergence with constant gene flow, failure to account for population size changes in either a daughter population or the ancestral population leads to overestimated divergence time and to a bias towards the choice of SC models. On the other hand, when the simulations included long periods of strict isolation the correct gene flow scenario was usually retrieved. We illustrate these issues reconstructing the demographic history of North Sea and Baltic Sea turbots (Schopthalmus maximus) by testing 16 IM and 16 SC scenarios, modelling changes in effective population sizes as well as the effects of linked selection and heterogeneous migration rates across the genome. As in the simulated data, failure to account for changes in effective population sizes resulted in selecting SC models with a long period of strict isolation and divergence times preceding the formation of the Baltic Sea. In contrast, models accounting for population size changes suggest that the Baltic Sea turbot population originated from a very recent (<6 kya) invasion and has diverged with constant gene flow from the North Sea. The results have broad implications for the study of speciation by high-lighting the potential effects of ancestral size changes and bottlenecks followed by growth on choices between competing scenarios of speciation. In general, extreme caution should be exercised when interpreting results of demographic model comparisons.

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“…S. typhle is a marine teleost, which originally invaded from the North Sea into the Baltic Sea after its formation about 8000 years ago (Wilson and Veraguth, 2010). The brackish salinity environment in the Baltic Sea imposes osmoregulatory stress on marine animals and is thus assumed to be an important driver for genetic divergence and adaptation to local condition (Berg et al, 2015;Guo et al, 2015;Johannesson et al, 2020). Strong genetic clines over the Baltic Sea salinity gradient were shown for a diversity of species (Johannesson et al, 2020) with strong patterns of local salinity adaptation (Leder et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…The brackish salinity environment in the Baltic Sea imposes osmoregulatory stress on marine animals and is thus assumed to be an important driver for genetic divergence and adaptation to local condition (Berg et al, 2015;Guo et al, 2015;Johannesson et al, 2020). Strong genetic clines over the Baltic Sea salinity gradient were shown for a diversity of species (Johannesson et al, 2020) with strong patterns of local salinity adaptation (Leder et al, 2021). Here, we focused on six pipefish populations from the German coastline A PERMANOVA was applied to gene expression (− Ct values) of all 558 samples for all genes (47), including immune genes comprised of the innate, adaptive and complement genes, as well as genes involved in metabolism, osmoregulation and epigenetics, e.g., methylation or histone modification.…”

Section: Discussionmentioning

confidence: 99%

Pipefish Locally Adapted to Low Salinity in the Baltic Sea Retain Phenotypic Plasticity to Cope With Ancestral Salinity Levels

et al. 2021

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Genetic adaptation and phenotypic plasticity facilitate the migration into new habitats and enable organisms to cope with a rapidly changing environment. In contrast to genetic adaptation that spans multiple generations as an evolutionary process, phenotypic plasticity allows acclimation within the life-time of an organism. Genetic adaptation and phenotypic plasticity are usually studied in isolation, however, only by including their interactive impact, we can understand acclimation and adaptation in nature. We aimed to explore the contribution of adaptation and plasticity in coping with an abiotic (salinity) and a biotic (Vibrio bacteria) stressor using six different populations of the broad-nosed pipefish Syngnathus typhle that originated from either high [14–17 Practical Salinity Unit (PSU)] or low (7–11 PSU) saline environments along the German coastline of the Baltic Sea. We exposed wild caught animals, to either high (15 PSU) or low (7 PSU) salinity, representing native and novel salinity conditions and allowed animals to mate. After male pregnancy, offspring was split and each half was exposed to one of the two salinities and infected with Vibrio alginolyticus bacteria that were evolved at either of the two salinities in a fully reciprocal design. We investigated life-history traits of fathers and expression of 47 target genes in mothers and offspring. Pregnant males originating from high salinity exposed to low salinity were highly susceptible to opportunistic fungi infections resulting in decreased offspring size and number. In contrast, no signs of fungal infection were identified in fathers originating from low saline conditions suggesting that genetic adaptation has the potential to overcome the challenges encountered at low salinity. Offspring from parents with low saline origin survived better at low salinity suggesting genetic adaptation to low salinity. In addition, gene expression analyses of juveniles indicated patterns of local adaptation, trans-generational plasticity and developmental plasticity. In conclusion, our study suggests that pipefish are locally adapted to the low salinity in their environment, however, they are retaining phenotypic plasticity, which allows them to also cope with ancestral salinity levels and prevailing pathogens.

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A Darwinian Laboratory of Multiple Contact Zones

Cited by 81 publications

References 108 publications

Genomic signatures of drift and selection driven by predation and human pressure in an insular lizard

Genomic signatures of drift and selection driven by predation and human pressure in an insular lizard

Biases in demographic modelling affect our understanding of recent divergence

Pipefish Locally Adapted to Low Salinity in the Baltic Sea Retain Phenotypic Plasticity to Cope With Ancestral Salinity Levels

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