scholarly journals Digest: How the snowshoe hare got its brown coat: Convergent evolution or gene flow?*

Evolution ◽  
2020 ◽  
Vol 74 (9) ◽  
pp. 2174-2175
Author(s):  
Jente Ottenburghs
Keyword(s):  
Gene Flow ◽  
Convergent Evolution ◽  
Snowshoe Hare ◽  
Or Gene

scholarly journals Emergent speciation by multiple Dobzhansky-Muller incompatibilities

2014 ◽  
Author(s):  
Tiago Paixão ◽  
Kevin E. Bassler ◽  
Ricardo B. R. Azevedo
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Network Model ◽  
Neutral Network ◽  
Collective Effects ◽  
Neutral Networks ◽  
Adaptive Landscapes ◽  
Complex Interactions ◽  
Or Gene

The Dobzhansky-Muller model posits that incompatibilities between alleles at different loci cause speciation. However, it is known that if the alleles involved in a Dobzhansky-Muller incompatibility (DMI) between two loci are neutral, the resulting reproductive isolation cannot be maintained in the presence of either mutation or gene flow. Here we show that speciation can emerge through the collective effects of multiple neutral DMIs that cannot, individually, cause speciation-a mechanism we call emergent speciation. We investigate emergent speciation using models of haploid holey adaptive landscapes-neutral networks-with recombination. We find that certain combinations of multiple neutral DMIs can lead to speciation. Furthermore, emergent speciation is a robust mechanism that can occur in the presence of migration, and of deviations from the assumptions of the neutral network model. Strong recombination and complex interactions between the DMI loci facilitate emergent speciation. These conditions are likely to occur in nature. We conclude that the interaction between DMIs may cause speciation.

scholarly journals Population Genomic Evidence Reveals Subtle Patterns of Differentiation in the Trophically Polymorphic Cuatro Ciénegas Cichlid, Herichthys minckleyi

2019 ◽  
Vol 110 (3) ◽  
pp. 361-369 ◽  
Author(s):  
Katherine L Bell ◽  
Chris C Nice ◽  
Darrin Hulsey
Keyword(s):  
Gene Flow ◽  
Biological Diversity ◽  
Molecular Genetic ◽  
Molecular Ecology ◽  
Cichlid Fish ◽  
Genome Wide ◽  
A Genome ◽  
The Face ◽  
Or Gene ◽  
Herichthys Minckleyi

Abstract In recent decades, an increased understanding of molecular ecology has led to a reinterpretation of the role of gene flow during the evolution of reproductive isolation and biological novelty. For example, even in the face of ongoing gene flow strong selection may maintain divergent polymorphisms, or gene flow may introduce novel biological diversity via hybridization and introgression from a divergent species. Herein, we elucidate the evolutionary history and genomic basis of a trophically polymorphic trait in a species of cichlid fish, Herichthys minckleyi. We explored genetic variation at 3 hierarchical levels; between H. minckleyi (n = 69) and a closely related species Herichthys cyanoguttatus (n = 10), between H. minckleyi individuals from 2 geographic locations, and finally between individuals with alternate morphotypes at both a genome-wide and locus-specific scale. We found limited support for the hypothesis that the H. minckleyi polymorphism is the result of ongoing hybridization between the 2 species. Within H. minckleyi we found evidence of geographic genetic structure, and using traditional population genetic analyses found that individuals of alternate morphotypes within a pool appear to be panmictic. However, when we used a locus-specific approach to examine the relationship between multi-locus genotype, tooth size, and geographic sampling, we found the first evidence for molecular genetic differences between the H. minckleyi morphotypes.

scholarly journals Convergent evolution of seasonal camouflage in response to reduced snow cover across the snowshoe hare range

2019 ◽  
Author(s):  
Matthew R. Jones ◽  
L. Scott Mills ◽  
Jeffrey D. Jensen ◽  
Jeffrey M. Good
Keyword(s):  
Gene Flow ◽  
Snow Cover ◽  
Pacific Northwest ◽  
Deep Structure ◽  
Low Frequency ◽  
Masking Effect ◽  
Snowshoe Hare ◽  
Changing Environments ◽  
Range Edge ◽  
History Of

AbstractDetermining how different populations adapt to similar environments is fundamental to understanding the limits of adaptation under changing environments. Snowshoe hares (Lepus americanus) typically molt into white winter coats to remain camouflaged against snow. In some warmer climates, hares have evolved brown winter camouflage – an adaptation that may spread under climate change. We used extensive range-wide genomic data to 1) resolve broad-scale patterns of population structure and gene flow and 2) investigate the factors shaping the origins and distribution of winter-brown camouflage variation. In coastal Pacific Northwest (PNW) populations, winter-brown camouflage is known to be determined by a recessive haplotype at the Agouti pigmentation gene. Our phylogeographic analyses revealed deep structure and limited gene flow between PNW and more northern Boreal populations, where winter-brown camouflage is rare along the range edge. Genome sequencing of a winter-brown snowshoe hare from Alaska shows that it lacks the winter-brown PNW haplotype, reflecting a history of convergent phenotypic evolution. However, the PNW haplotype does occur at low frequency in a winter-white population from Montana, consistent with the spread of a locally deleterious recessive variant that is masked from selection when rare. Simulations show that if annual snow cover dramatically declined in the same population, then the predicted selective increase in frequency of the now beneficial winter-brown Agouti allele is likely to be extremely slow due to the same masking effect. Our findings underscore how allelic dominance can shape the geographic extent and rate of convergent adaptation in response to rapidly changing environments.

scholarly journals Introgression makes waves in inferred histories of effective population size

2017 ◽  
Author(s):  
John Hawks
Keyword(s):  
Gene Flow ◽  
Population Size ◽  
Effective Population Size ◽  
Population History ◽  
Human Populations ◽  
Effective Population ◽  
History Of ◽  
Or Gene ◽  
Time Of Origin ◽  
Past Population

AbstractHuman populations have a complex history of introgression and of changing population size. Human genetic variation has been affected by both these processes, so that inference of past population size depends upon the pattern of gene flow and introgression among past populations. One remarkable aspect of human population history as inferred from genetics is a consistent “wave” of larger effective population size, prior to the bottlenecks and expansions of the last 100,000 years. Here I carry out a series of simulations to investigate how introgression and gene flow from genetically divergent ancestral populations affect the inference of ancestral effective population size. Both introgression and gene flow from an extinct, genetically divergent population consistently produce a wave in the history of inferred effective population size. The time and amplitude of the wave reflect the time of origin of the genetically divergent ancestral populations and the strength of introgression or gene flow. These results demonstrate that even small fractions of introgression or gene flow from ancient populations may have large effects on the inference of effective population size.

scholarly journals LOSS OF EVOLUTIONARY RESISTANCE BY THE OLIGOCHAETELIMNODRILUS HOFFMEISTERITO A TOXIC SUBSTANCE-COST OR GENE FLOW?

Evolution ◽  
2010 ◽  
Vol 64 (1) ◽  
pp. 152-165 ◽  
Author(s):  
Joshua A. Mackie ◽  
Jeffrey S. Levinton ◽  
Rachel Przeslawski ◽  
Dominique DeLambert ◽  
William Wallace
Keyword(s):  
Gene Flow ◽  
Toxic Substance ◽  
Or Gene

scholarly journals GENETIC VARIATION AND GEOGRAPHIC DIFFERENTIATION IN MITOCHONDRIAL DNA OF THE HORSESHOE CRAB, LIMULUS POLYPHEMUS

Genetics ◽  
1986 ◽  
Vol 112 (3) ◽  
pp. 613-627
Author(s):  
Nancy C Saunders ◽  
Louis G Kessler ◽  
John C Avise
Keyword(s):  
Mitochondrial Dna ◽  
Gene Flow ◽  
Horseshoe Crab ◽  
Gulf Coast ◽  
Sequence Divergence ◽  
Clonal Diversity ◽  
Limulus Polyphemus ◽  
Site Variation ◽  
Horseshoe Crabs ◽  
Or Gene

ABSTRACT Restriction site variation in mitochondrial DNA (mtDNA) of the horseshoe crab (Limulus polyphemus) was surveyed in populations ranging from New Hampshire to the Gulf Coast of Florida. MtDNA clonal diversity was moderately high, particularly in southern samples, and a major genetic "break" (nucleotide sequence divergence approximately 2%) distinguished all sampled individuals which were north vs. south of a region in northeastern Florida. The area of genotypic divergence in Limulus corresponds to a long-recognized zoogeographic boundary between warm-temperate and tropical marine faunas, and it suggests that selection pressures and/or gene flow barriers associated with water mass differences may also influence the evolution of species widely distributed across such transition zones. On the other hand, a comparison of the mtDNA divergence patterns in Limulus with computer models involving stochastic lineage extinction in species with limited gene flow demonstrates that deterministic explanations need not necessarily be invoked to account for the observations. Experiments to distinguish stochastic from deterministic possibilities are suggested. Overall, the pattern and magnitude of mtDNA differentiation in horseshoe crabs is very similar to that typically reported for freshwater and terrestrial species assayed over a comparable geographic range. Results demonstrate for the first time that, geographically, at least some continuously distributed marine organisms can show considerable mtDNA genetic differentiation.

scholarly journals Variation in sexual dimorphism and assortative mating do not predict genetic divergence in the sexually dimorphic Goodeid fish Girardinichthys multiradiatus

2012 ◽  
Vol 58 (3) ◽  
pp. 440-452 ◽  
Author(s):  
C. Macías Garcia ◽  
G. Smith ◽  
C. González Zuarth ◽  
J. A. Graves ◽  
M. G. Ritchie
Keyword(s):  
Sexual Selection ◽  
Gene Flow ◽  
Sexual Dimorphism ◽  
Assortative Mating ◽  
Genetic Divergence ◽  
Isolation By Distance ◽  
Morphological Differentiation ◽  
Morphological Differences ◽  
Or Gene ◽  
Male Morphology

Abstract Sexual dimorphism is often used as a proxy for the intensity of sexual selection in comparative studies of sexual selection and diversification. The Mexican Goodeinae are a group of livebearing freshwater fishes with large variation between species in sexual dimorphism in body shape. Previously we found an association between variation in morphological sexual dimorphism between species and the amount of gene flow within populations in the Goodeinae. Here we have examined if morphological differentiation within a single dimorphic species is related to assortative mating or gene flow between populations. In the Amarillo fish Girardinichthys multiradiatus studies have shown that exaggerated male fins are targets of female preferences. We find that populations of the species differ in the level of sexual dimorphism displayed due to faster evolution of differences in male than female morphology. However, this does not predict variation in assortative mating tests in the laboratory; in fact differences in male morphology are negatively correlated with assortative mating. Microsatellite markers reveal significant genetic differences between populations. However, gene flow is not predicted by either morphological differences or assortative mating. Rather, it demonstrates a pattern of isolation by distance with greater differentiation between watersheds. We discuss the caveats of predicting behavioural and genetic divergence from so-called proxies of sexual selection.

scholarly journals Convergent evolution of seasonal camouflage in response to reduced snow cover across the snowshoe hare range*

Evolution ◽  
2020 ◽  
Vol 74 (9) ◽  
pp. 2033-2045 ◽  
Author(s):  
Matthew R. Jones ◽  
L. Scott Mills ◽  
Jeffrey D. Jensen ◽  
Jeffrey M. Good
Keyword(s):  
Snow Cover ◽  
Convergent Evolution ◽  
Snowshoe Hare

scholarly journals Population genomics perspectives on convergent adaptation

2019 ◽  
Vol 374 (1777) ◽  
pp. 20180236 ◽  
Author(s):  
Kristin M. Lee ◽  
Graham Coop
Keyword(s):  
Gene Flow ◽  
Molecular Basis ◽  
Convergent Evolution ◽  
Population Genomics ◽  
Evolutionary Change ◽  
Theme Issue ◽  
Fitness Advantage ◽  
Standing Variation ◽  
Independent Replication ◽  
Genetics And Genomics

Convergent adaptation is the independent evolution of similar traits conferring a fitness advantage in two or more lineages. Cases of convergent adaptation inform our ideas about the ecological and molecular basis of adaptation. In judging the degree to which putative cases of convergent adaptation provide an independent replication of the process of adaptation, it is necessary to establish the degree to which the evolutionary change is unexpected under null models and to show that selection has repeatedly, independently driven these changes. Here, we discuss the issues that arise from these questions particularly for closely related populations, where gene flow and standing variation add additional layers of complexity. We outline a conceptual framework to guide intuition as to the extent to which evolutionary change represents the independent gain of information owing to selection and show that this is a measure of how surprised we should be by convergence. Additionally, we summarize the ways population and quantitative genetics and genomics may help us address questions related to convergent adaptation, as well as open new questions and avenues of research. This article is part of the theme issue ‘Convergent evolution in the genomics era: new insights and directions’.

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