scholarly journals A lizard with two tales: what diversification within Sceloporus occidentalis teaches us about species formation

2021 ◽  
Author(s):  
Ricardo Pereira ◽  
Sonal Singhal
Keyword(s):  
Gene Flow ◽  
Genetic Drift ◽  
Charles Darwin ◽  
Molecular Ecology ◽  
Genetic Interactions ◽  
Sceloporus Occidentalis ◽  
Genome Data ◽  
Species Formation ◽  
Ring Species ◽  
Natural Laboratory

In 1859, Charles Darwin proposed that species are not fundamentally different from subspecies or the varieties from which they evolve. A century later, Dobzhansky (1958) suggested that many such lineages are ephemeral and are likely to revert differentiation through introgression (Fig. 1A); only a few evolve complete reproductive isolation and persist in sympatry. In this issue of Molecular Ecology, Bouzid et al. (2021) show how new analytical methods, when applied to genome data, allow us to more precisely determine whether or not species formation follows the paths outlined by Darwin and Dobzhansky (Fig. 1B). The authors study the diversification of the lizard Sceloporus occidentalis, finding a continuum of genetic interactions between the preservation of genetic identity to genetic merger, analogous to what is exemplified by ring species. In doing so, they teach us two tales on species formation: that lineages are fractal byproducts of evolutionary processes such as genetic drift and selection, and that lineages are often ephemeral and do not always progress into species. Studying ephemeral lineages like those in S. occidentalis allows us to capture divergence at its earliest stages, and potentially to determine the factors that allow lineages to remain distinct despite pervasive gene flow. These lineages thus serve as a natural laboratory to address long standing hypotheses on species formation.

Barriers to gene flow and ring species formation

Evolution ◽  
2016 ◽  
Vol 71 (2) ◽  
pp. 442-448 ◽  
Author(s):  
Ayana de Brito Martins ◽  
Marcus Aloizio Martinez de Aguiar
Keyword(s):  
Gene Flow ◽  
Species Formation ◽  
Ring Species

scholarly journals Evidence for ephemeral ring species formation during the diversification history of western fence lizards ( Sceloporus occidentalis )

2021 ◽  
Author(s):  
Nassima M. Bouzid ◽  
James W. Archie ◽  
Roger A. Anderson ◽  
Jared A. Grummer ◽  
Adam D. Leaché
Keyword(s):  
Sceloporus Occidentalis ◽  
Species Formation ◽  
History Of ◽  
Ring Species

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 Molecular Ecology and Systematics of Blue  Mussels (Genus Mytilus) (Mytilidae; Bivalvia;  Mollusca) in the Southern Hemisphere

2021 ◽  
Author(s):  
◽  
Kristen Marie Westfall
Keyword(s):  
Gene Flow ◽  
New Zealand ◽  
South America ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Molecular Ecology ◽  
Population Subdivision ◽  
Kerguelen Islands ◽  
Blue Mussels ◽  
The World

<p>The Mytilus edulis species complex, comprised of M. edulis, M. galloprovincialis and M. trossulus, is antitropically distributed in temperate coastal regions of all oceans and main seas of the world. This genus has been heavily studied in the Northern hemisphere but Southern hemisphere populations have received much less attention. This thesis aims to place Southern hemisphere blue mussels into global evolutionary relationships among Mytilus species and investigate aspects of their molecular ecology, including, effects of non-native Northern hemisphere species introductions, biogeography across the Southern hemisphere, regional phylogeographic patterns and population genetics within New Zealand. Southern hemisphere blue mussel phylogenetic reconstruction resulted in the detection of a monophyletic M. galloprovincialis lineage. Two new molecular markers developed with specificity for this lineage and congruence among phylogenetic investigations indicates a panhemispheric distribution of this M. galloprovincialis lineage with implications for naming a new sibling species of the M. edulis complex. This proposed new species, M. meridianus, is distributed in South America, the Kerguelen Islands, New Zealand and Australia at latitudes between ~ 30°S and ~ 55°S. Non-native M. galloprovincialis introduced from the Northern hemisphere have been present in NZ, Australia and Chile for at least ten years and hybridise with native blue mussels. Introgression is observed in New Zealand and Australian but not Chilean hybrid regions. The limited number of introduced mussels in Australia induces hybrid swamping of non-native alleles but an interlineage gender bias towards non-native maternal parents may result in eventual loss of the unique genomic content of native blue mussels in NZ. Southern hemisphere blue mussels form a monophyletic sister clade to a haplogroup shared by Northern hemisphere M. edulis and M. galloprovincialis. Although single gene histories are not congruent with respect to evolutionary relationships within the Northern hemisphere due to introgressive hybridisation after speciation, it is clear that Southern hemisphere blue mussels arose from a species native to the northeast Atlantic Ocean after speciation of the three ‘M. edulis complex’ members. Within the Southern hemisphere monophyletic clade lies three reciprocally monophyletic clades restricted to the geographic regions South America/Kerguelen Islands, New Zealand and Australia. Phylogeographic analysis indicates past gene flow between South American/Kerguelen Islands and New Zealand populations that has ceased at present day and ongoing gene flow between South America and the Kerguelen Islands likely via the West Wind Drift. Within NZ, population subdivision inferred from mtDNA indicates genetic variation is distributed within an east-west phylogeographic split on the North Island. These populations experienced gene flow in the past that has ceased at present day. Microsatellite allele frequencies indicate a different population subdivision within the northwest North Island that has been narrowed down to a 15 km stretch of coastline in a sheltered bay. The abrupt discontinuity within a small geographic area does not conform to classic population subdivision in this broad-cast spawning species, therefore, further investigation into the genomic content of northwest North Island mussels with respect to introgressed non-native genes is warranted. Resolving complex phylogenetic patterns from interspecific introgression is key to understanding the evolutionary history of Southern hemisphere M. galloprovincialis. Further characterisation of hybrid introgression would increase accuracy of (1) inferences of processes contributing to hybridisation dynamics and (2) population subdivision in NZ. Probing the basis for variation of hybridisation dynamics would help to predict the outcomes of Northern hemisphere M. galloprovincialis introductions in other areas of the world.</p>

scholarly journals Adaptive divergence in resistance to herbivores inDatura stramonium

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1411 ◽  
Author(s):  
Guillermo Castillo ◽  
Pedro L. Valverde ◽  
Laura L. Cruz ◽  
Johnattan Hernández-Cumplido ◽  
Guadalupe Andraca-Gómez ◽  
...  
Keyword(s):  
Gene Flow ◽  
Genetic Differentiation ◽  
Genetic Drift ◽  
Datura Stramonium ◽  
Adaptive Divergence ◽  
Restricted Gene Flow ◽  
Trichome Density ◽  
Phenotypic Differentiation ◽  
Phenotypic Resistance ◽  
Resistance Traits

Defensive traits exhibited by plants vary widely across populations. Heritable phenotypic differentiation is likely to be produced by genetic drift and spatially restricted gene flow between populations. However, spatially variable selection exerted by herbivores may also give rise to differences among populations. To explore to what extent these factors promote the among-population differentiation of plant resistance of 13 populations ofDatura stramonium, we compared the degree of phenotypic differentiation (PST) of leaf resistance traits (trichome density, atropine and scopolamine concentration) against neutral genetic differentiation (FST) at microsatellite loci. Results showed that phenotypic differentiation in defensive traits among-population is not consistent with divergence promoted by genetic drift and restricted gene flow alone. Phenotypic differentiation in scopolamine concentration was significantly higher thanFSTacross the range of trait heritability values. In contrast, genetic differentiation in trichome density was different fromFSTonly when heritability was very low. On the other hand, differentiation in atropine concentration differed from the neutral expectation when heritability was less than or equal to 0.3. In addition, we did not find a significant correlation between pair-wise neutral genetic distances and distances of phenotypic resistance traits. Our findings reinforce previous evidence that divergent natural selection exerted by herbivores has promoted the among-population phenotypic differentiation of defensive traits inD. stramonium.

scholarly journals Extensive introgression despite Haldane’s rule: insights from grasshopper hybrid zones

2021 ◽  
Author(s):  
Linda Hagberg ◽  
Enrique Celemin ◽  
Iker Irisarri ◽  
Oliver Hawlitschek ◽  
J L Bella ◽  
...  
Keyword(s):  
Gene Flow ◽  
Reproductive Isolation ◽  
Male Sterility ◽  
Secondary Contact ◽  
Hybrid Zones ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Haldane’S Rule ◽  
Haldane's Rule ◽  
Species Formation

Although the process of species formation is notoriously idiosyncratic, the observation of pervasive patterns of reproductive isolation across species pairs suggests that generalities, or “rules”, underlie species formation in all animals. Haldane’s rule states that whenever a sex is absent, rare or sterile in a cross between two taxa, that sex is usually the heterogametic sex. Yet, understanding how Haldane’s rule first evolves and whether it is associated to genome wide barriers to gene flow remains a challenging task because this rule is usually studied in highly divergent taxa that no longer hybridize in nature. Here, we address these questions using the meadow grasshopper Pseudochorthippus parallelus where populations that readily hybridize in two natural hybrid zones show hybrid male sterility in laboratorial crosses. Using mitochondrial data, we infer that such populations have diverged some 100,000 years ago, surviving multiple glacial periods in isolated Pleistocenic refugia. Nuclear data shows that secondary contact has led to extensive introgression throughout the species range, including between populations showing hybrid male sterility. We find repeatable patterns of genomic differentiation across the two hybrid zones, yet such patterns are consistent with shared genomic constraints across taxa rather than their role in reproductive isolation. Together, our results suggest that Haldane’s rule can evolve relatively quickly within species, particularly when associated to strong demographic changes. At such early stages of species formation, hybrid male sterility still permits extensive gene flow, allowing future studies to identify genomic regions associated with reproductive barriers.

scholarly journals The Sensitiveness of Expected Heterozygosity and Allelic Richness Estimates for Analyzing Population Genetic Diversity

2021 ◽  
Author(s):  
María Eugenia Barrandeguy ◽  
María Victoria García
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Genetic Variability ◽  
Population Size ◽  
Genetic Drift ◽  
Population Genetic ◽  
Allelic Richness ◽  
Theoretical Background ◽  
Computational Simulations ◽  
Expected Heterozygosity

Genetic diversity comprises the total of genetic variability contained in a population and it represents the fundamental component of changes since it determines the microevolutionary potential of populations. There are several measures for quantifying the genetic diversity, most notably measures based on heterozygosity and measures based on allelic richness, i.e. the expected number of alleles in populations of same size. These measures differ in their theoretical background and, in consequence, they differ in their ecological and evolutionary interpretations. Therefore, in the present chapter these measures of genetic diversity were jointly analyzed, highlighting the changes expected as consequence of gene flow and genetic drift. To develop this analysis, computational simulations of extreme scenarios combining changes in the levels of gene flow and population size were performed.

scholarly journals Limits to adaptation along environmental gradients

2014 ◽  
Author(s):  
Jitka Polechová ◽  
Nick Barton
Keyword(s):  
Gene Flow ◽  
Genetic Drift ◽  
Environmental Gradients ◽  
Single Species ◽  
Local Conditions ◽  
Deterministic Theory ◽  
Range Margin ◽  
Abrupt Changes ◽  
Analytical Tools ◽  
Range Fragmentation

Why do species not adapt to ever-wider ranges of conditions, gradually expanding their ecological niche and geographic range? Gene flow across environments has two conflicting effects: while it increases genetic variation, which is a prerequisite for adaptation, gene flow may swamp adaptation to local conditions. In 1956, Haldane proposed that when the environment varies across space, ?swamping? by gene flow creates a positive feedback between low population size and maladaptation, leading to a sharp range margin. Yet, current deterministic theory shows that when variance can evolve, there is no such limit. Using simple analytical tools and simulations, we show that genetic drift can generate a sharp margin to a species' range, by reducing genetic variance below the level needed for adaptation to spatially variable conditions. Aided by separation of ecological and evolutionary time scales, the identified effective dimensionless parameters reveal a simple threshold that predicts when adaptation at the range margin fails. Two observable parameters determine the threshold: i) the effective environmental gradient, which can be measured by the loss of fitness due to dispersal to a different environment, and ii) the efficacy of selection relative to genetic drift. The theory predicts sharp range margins even in the absence of abrupt changes in the environment. Furthermore, it implies that gradual worsening of conditions across a species' habitat may lead to a sudden range fragmentation, when adaptation to a wide span of conditions within a single species becomes impossible.

scholarly journals Yangtze River, an insignificant genetic boundary in tufted deer (Elaphodus cephalophus): the evidence from a first population genetics study

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2654 ◽  
Author(s):  
Zhonglou Sun ◽  
Tao Pan ◽  
Hui Wang ◽  
Mujia Pang ◽  
Baowei Zhang
Keyword(s):  
Gene Flow ◽  
Yangtze River ◽  
Population Decline ◽  
Molecular Ecology ◽  
Population Increase ◽  
The Yangtze River ◽  
Population Demography ◽  
Vector Autoregressions ◽  
High Genetic Diversity ◽  
Geographical Barrier

Great rivers were generally looked at as the geographical barrier to gene flow for many taxonomic groups. The Yangtze River is the third largest river in the world, and flows across South China and into the East China Sea. Up until now, few studies have been carried out to evaluate its effect as a geographical barrier. In this study, we attempted to determine the barrier effect of the Yangtze River on the tufted deer (Elaphodus cephalophus) using the molecular ecology approach. Using mitochondrial DNA control region (CR) sequences and 13 nuclear microsatellite loci, we explored the genetic structure and gene flow in two adjacent tufted deer populations (Dabashan and Wulingshan populations), which are separated by the Yangtze River. Results indicated that there are high genetic diversity levels in the two populations, but no distinguishable haplotype group or potential genetic cluster was detected which corresponded to specific geographical population. At the same time, high gene flow was observed between Wulingshan and Dabashan populations. The tufted deer populations experienced population decrease from 0.3 to 0.09 Ma BP, then followed by a distinct population increase. A strong signal of recent population decline (T= 4,396 years) was detected in the Wulingshan population by a Markov-Switching Vector Autoregressions(MSVAR) process population demography analysis. The results indicated that the Yangtze River may not act as an effective barrier to gene flow in the tufted deer. Finally, we surmised that the population demography of the tufted deer was likely affected by Pleistocene climate fluctuations and ancient human activities.

Sign in / Sign up

Export Citation Format

Share Document