Lack of genetic differentiation between two sympatric species of Astyanax (Characidae:Teleostei) in Lake Catemaco, Mexico

2020 ◽  
Author(s):  
Ignacio Doadrio ◽  
Patricia Ornelas ◽  
Elena G. Gonzalez ◽  
Diethard Tautz
Keyword(s):  
Genetic Differentiation ◽  
Genetic Basis ◽  
Single Gene ◽  
Ecological Speciation ◽  
Sympatric Species ◽  
Morphological Divergence ◽  
Wide Range ◽  
Species Pairs ◽  
Morphological Differences ◽  
Trophic Niches

Abstract Background Fish of the genus Astyanax are known to be able to adapt to a wide range of ecological conditions and are especially known for repeated colorizations of cave systems. In lakes they often occur in species pairs. In the case we study here, they show major morphological differences, such that they were originally classified in different genera. Previous studies have shown that these morphological differences correlate with occupation of different trophic niches. Hence, this could be an example of ecological speciation under sympatric conditions, which predicts that differential ecological adaptation becomes coupled to assortative mating and to the formation of genetically distinct groups that may be called species. We have tested this prediction by typing a set of microsatellites for the two morphs in the lake in comparison to an allopatric population.Results While we find the expected differentiation with respect to the allopatric population, there is a complete lack of genetic differentiation between the two morphs within the lake. Hence, the two morphs in the lake are either in an extremely early phase of speciation or represent two extreme morphotypes derived from a single gene pool.Conclusions Even when we failed to recover the two morphs as reproductively isolated, this model provides a unique opportunity to characterize those factors that would promote the ecological divergence, thus, our lacustrine morphs system gives a unique opportunity to understand the genetic basis of how morphological divergence in the presence of gene flow.

The role of competition in determining morphological differences between Victorian and Tasmanian passerine birds

1977 ◽  
Vol 25 (3) ◽  
pp. 429 ◽  
Author(s):  
I Abbott
Keyword(s):  
Wing Length ◽  
Sympatric Species ◽  
Congeneric Species ◽  
Tarsus Length ◽  
Frequency Distributions ◽  
Clear Cut ◽  
Significant Difference ◽  
Species Pairs ◽  
Morphological Differences ◽  
Bill Length

Bill length, tarsus length and wing length were measured in 107 passerine species in southern Victoria and 46 in Tasmania, and the possibility that the impoverishment of the Tasmanian avifauna elicits morphological shifts was evaluated. An hypothesis of competitor release failed to account for the main morphological features of the Tasmanian avifauna. There was no significant difference between the frequency distributions of the three variables in mainland and island species, which suggests that no character size on the mainland is over- or under-represented in Tasmania; in spite of this, in nearly all the species common to both areas all three variables are significantly larger in Tasmania. No significant difference was found between the frequency distributions of character-ratios for mainland and island congeneric species-pairs, though theory predicts the island distribution would be the more skew. In 17 pairs of congeners occurring in both areas, the bill length and tarsus length ratios are not significantly different, and though wing length ratios do differ significantly, it is the mainland pairs that have the larger ratio. The variability of the three characters in 25 species did not differ significantly between mainland and island. Many genera which are represented by several sympatric species in Victoria have only one representative (usually the larger) in Tasmania. Although the theory of competitor release predicts that the species in Tasmania should show decreased character sizes, a clear-cut trend to increased size was found. Congeneric species-pairs in Tasmania do not show large morphological differences, which cannot be necessary for successful coexistence there. The above results are discussed briefly, and an hypothesis based on the larger size of food items in Tasmania is proposed to explain them.

scholarly journals Polygenic selection drives the evolution of convergent transcriptomic landscapes across continents within a Nearctic sister-species complex

2018 ◽  
Author(s):  
Clément Rougeux ◽  
Pierre-Alexandre Gagnaire ◽  
Kim Praebel ◽  
Ole Seehausen ◽  
Louis Bernatchez
Keyword(s):  
Gene Expression ◽  
Natural Selection ◽  
Differential Gene Expression ◽  
Ecological Speciation ◽  
Sympatric Species ◽  
Benthic Species ◽  
Species Pairs ◽  
Differential Gene ◽  
Polygenic Selection

ABSTRACTIn contrast to the plethora of studies focusing on the genomic basis of adaptive phenotypic divergence, the role of gene expression during speciation has been much less investigated and consequently, less understood. Yet, the convergence of differential gene expression patterns between closely related species-pairs might reflect the role of natural selection during the process of ecological speciation. Here, we test for intercontinental convergence in differential transcriptional signatures between limnetic and benthic sympatric species-pairs of Lake Whitefish (Coregonus clupeaformis) and its sister-lineage, the European Whitefish (C. lavaretus), using six replicated sympatric species-pairs (two in North America, two in Norway and two in Switzerland). We characterized both sequence variation in transcribed regions and differential gene expression between sympatric limnetic and benthic species across regions and continents. Our first finding was that differentially expressed genes (DEG) between limnetic and benthic whitefish tend to be enriched in shared polymorphism among sister-lineages. We then used both genotypes and co-variation in expression in order to infer polygenic selection at the gene level. We identified parallel outliers and DEG involving genes primarily over-expressed in limnetic species relative to the benthic species. Our analysis finally revealed the existence of shared genomic bases underlying parallel differential expression across replicated species pairs from both continents, such as a cis-eQTL affecting the pyruvate kinase expression level involved in glycolysis. Our results are consistent with a longstanding role of natural selection in maintaining transcontinental diversity at phenotypic traits involved in ecological speciation between limnetic and benthic whitefishes.

Quantitative Trait Loci Affecting Differences in Floral Morphology Between Two Species of Monkeyflower (Mimulus)

Genetics ◽  
1998 ◽  
Vol 149 (1) ◽  
pp. 367-382 ◽  
Author(s):  
H D Bradshaw ◽  
Kevin G Otto ◽  
Barbara E Frewen ◽  
John K McKay ◽  
Douglas W Schemske
Keyword(s):  
Quantitative Trait Loci ◽  
Reproductive Isolation ◽  
Quantitative Trait ◽  
Floral Morphology ◽  
Cumulative Effect ◽  
Sympatric Species ◽  
Accurate Estimate ◽  
Phenotypic Variance ◽  
Trait Loci ◽  
Morphological Differences

Abstract Conspicuous differences in floral morphology are partly responsible for reproductive isolation between two sympatric species of monkeyflower because of their effect on visitation of the flowers by different pollinators. Mimulus lewisii flowers are visited primarily by bumblebees, whereas M. cardinalis flowers are visited mostly by hummingbirds. The genetic control of 12 morphological differences between the flowers of M. lewisii and M. cardinalis was explored in a large linkage mapping population of F2 plants (n = 465) to provide an accurate estimate of the number and magnitude of effect of quantitative trait loci (QTLs) governing each character. Between one and six QTLs were identified for each trait. Most (9/12) traits appear to be controlled in part by at least one major QTL explaining ≥25% of the total phenotypic variance. This implies that either single genes of individually large effect or linked clusters of genes with a large cumulative effect can play a role in the evolution of reproductive isolation and speciation.

scholarly journals A New Statistic for Detecting Genetic Differentiation

Genetics ◽  
2000 ◽  
Vol 155 (4) ◽  
pp. 2011-2014 ◽  
Author(s):  
Richard R Hudson
Keyword(s):  
Genetic Differentiation ◽  
Dna Sequences ◽  
Genetic Data ◽  
Island Model ◽  
Wide Range ◽  
Infinite Sites Model ◽  
Parameter Values

Abstract A new statistic for detecting genetic differentiation of subpopulations is described. The statistic can be calculated when genetic data are collected on individuals sampled from two or more localities. It is assumed that haplotypic data are obtained, either in the form of DNA sequences or data on many tightly linked markers. Using a symmetric island model, and assuming an infinite-sites model of mutation, it is found that the new statistic is as powerful or more powerful than previously proposed statistics for a wide range of parameter values.

Comparative morphology of two sympatric Pareledone species from South Georgia

1994 ◽  
Vol 6 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Heather I. Daly ◽  
Paul G. Rodhouse
Keyword(s):  
Reproductive Isolation ◽  
Body Mass ◽  
Comparative Morphology ◽  
Sympatric Species ◽  
Morphometric Data ◽  
South Georgia ◽  
Buccal Mass ◽  
Significant Difference ◽  
Sharp Point ◽  
Trophic Niches

Morphometric data were collected for 410 specimens of Pareledone turqueti and P. polymorpha caught around South Georgia. The two species differ in beak morphology and in the male hectocotylus. The species have similar appearances although there is a small but significant difference in the mantle length/body mass relationship for females, with P. polymorpha having a relatively longer mantle. There is no significant difference in the arm length/body mass relationship between species or sexes (p>0.05), except in the case of arm IV of females. There is an interspecific significant difference between sucker number on arms I and II of males, arms I–IV of females, and between hood length and mass of the buccal mass (p<0.05), with P. turqueti having relatively lower sucker numbers, a longer hood length and greater buccal mass mass. The beak of P. turqueti is similar to that of Eledone spp. but P. polymorpha has a small, fine beak with the rostral tip ending in an elongated, sharp point. Differences in beak and buccal mass suggest that these sympatric species occupy distinct trophic niches and that the differing morphology of the male hectocotylus is a factor in reproductive isolation.

Epigenetics and Applied Anthropology

2021 ◽  
Author(s):  
Charles H. Klein
Keyword(s):  
Social Inequalities ◽  
Homo Sapiens ◽  
Single Gene ◽  
Molecular Genetic ◽  
Healthcare Providers ◽  
Basic Research ◽  
Sufficient Information ◽  
Theoretical Frameworks ◽  
Noncoding Dna ◽  
Wide Range

Since Francis Crick and James D. Watson’s discovery of DNA in 1953, researchers, policymakers, and the general public have sought to understand the ways in which genetics shapes human lives. A milestone in these efforts was the completion of the Human Genome Project’s (HGP) sequencing of Homo sapiens’ nearly three million base pairs in 2003. Yet, despite the excitement surrounding the HGP and the discovery of the structural genetic underpinnings of several debilitating diseases, the vast majority of human health outcomes have not been linked to a single gene. Moreover, even when genes have been associated with particular diseases (e.g., breast and colon cancer), it is not well understood why certain genetically predisposed individuals become ill and others do not. Nor has the HGP’s map provided sufficient information to understand the actual functioning of the human genetic code, including the role of noncoding DNA (“junk DNA”) in regulating molecular genetic processes. In response, a growing number of scientists have shifted their attention from structural genetics to epigenetics, the study of how genes express themselves in particular situations and environments. Anthropologists play roles in these applications of epigenetics to real-world settings. Their new theoretical frameworks unsettle the nature-versus-nurture binary and support biocultural anthropological research demonstrating how race becomes biology and embodies social inequalities and health disparities across generations. Ethnographically grounded case studies further highlight the diverse epigenetic logics held by healthcare providers, researchers, and patient communities and how these translations of scientific knowledge shape medical practice and basic research. The growing field of environmental epigenetics also offers a wide range of options for students and practitioners interested in applying the anthropological toolkit in epigenetics-related work.

Reaching Future Scientists, Consumers, & Citizens

2014 ◽  
Vol 76 (6) ◽  
pp. 379-383 ◽  
Author(s):  
Melissa A. Hicks ◽  
Rebecca J. Cline ◽  
Angela M. Trepanier
Keyword(s):  
Personalized Medicine ◽  
Genetic Basis ◽  
Genetic Disorders ◽  
Single Gene ◽  
Personal Health ◽  
Adult Onset ◽  
Biology Textbooks ◽  
Multifactorial Diseases ◽  
Single Gene Disorders

An understanding of how genomics information, including information about risk for common, multifactorial disease, can be used to promote personal health (personalized medicine) is becoming increasingly important for the American public. We undertook a quantitative content analysis of commonly used high school textbooks to assess how frequently the genetic basis of common multifactorial diseases was discussed compared with the “classic” chromosomal–single gene disorders historically used to teach the concepts of genetics and heredity. We also analyzed the types of conditions or traits that were discussed. We identified 3957 sentences across 11 textbooks that addressed multifactorial and “classic” genetic disorders. “Classic” gene disorders were discussed relatively more frequently than multifactorial diseases, as was their genetic basis, even after we enriched the sample to include five adult-onset conditions common in the general population. Discussions of the genetic or hereditary components of multifactorial diseases were limited, as were discussions of the environmental components of these conditions. Adult-onset multifactorial diseases are far more common in the population than chromosomal or single-gene disorders; many are potentially preventable or modifiable. As such, they are targets for personalized medical approaches. The limited discussion in biology textbooks of the genetic basis of multifactorial conditions and the role of environment in modifying genetic risk may limit the public’s understanding and use of personalized medicine.

scholarly journals Geography is more important than life history in the recent diversification of the tiger salamander complex

2021 ◽  
Vol 118 (17) ◽  
pp. e2014719118
Author(s):  
Kathryn M. Everson ◽  
Levi N. Gray ◽  
Angela G. Jones ◽  
Nicolette M. Lawrence ◽  
Mary E. Foley ◽  
...  
Keyword(s):  
Life History ◽  
Gene Flow ◽  
Genetic Differentiation ◽  
Population Genetic ◽  
Tiger Salamander ◽  
Life History Variation ◽  
Mexican Axolotl ◽  
Population Genetic Differentiation ◽  
Wide Range ◽  
Lineage Divergence

The North American tiger salamander species complex, including its best-known species, the Mexican axolotl, has long been a source of biological fascination. The complex exhibits a wide range of variation in developmental life history strategies, including populations and individuals that undergo metamorphosis; those able to forego metamorphosis and retain a larval, aquatic lifestyle (i.e., paedomorphosis); and those that do both. The evolution of a paedomorphic life history state is thought to lead to increased population genetic differentiation and ultimately reproductive isolation and speciation, but the degree to which it has shaped population- and species-level divergence is poorly understood. Using a large multilocus dataset from hundreds of samples across North America, we identified genetic clusters across the geographic range of the tiger salamander complex. These clusters often contain a mixture of paedomorphic and metamorphic taxa, indicating that geographic isolation has played a larger role in lineage divergence than paedomorphosis in this system. This conclusion is bolstered by geography-informed analyses indicating no effect of life history strategy on population genetic differentiation and by model-based population genetic analyses demonstrating gene flow between adjacent metamorphic and paedomorphic populations. This fine-scale genetic perspective on life history variation establishes a framework for understanding how plasticity, local adaptation, and gene flow contribute to lineage divergence. Many members of the tiger salamander complex are endangered, and the Mexican axolotl is an important model system in regenerative and biomedical research. Our results chart a course for more informed use of these taxa in experimental, ecological, and conservation research.

scholarly journals Population Genetics of the Red Rock Lobster,  Jasus edwardsii

2021 ◽  
Author(s):  
◽  
Luke Thomas
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
New Zealand ◽  
Genetic Differentiation ◽  
Microsatellite Markers ◽  
Rocky Reef ◽  
Rock Lobster ◽  
Wide Range ◽  
Jasus Edwardsii ◽  
Polymorphic Microsatellite

<p>Understanding patterns of gene flow across a species range is a vital component of an effective fisheries management strategy. The advent of highly polymorphic microsatellite markers has facilitated the detection of fine-scale patterns of genetic differentiation at levels below the resolving power of earlier techniques. This has triggered the wide-spread re-examination of population structure for a number of commercially targeted species. The aims of thesis were to re-investigate patterns of gene flow of the red rock lobster Jasus edwardsii throughout New Zealand and across the Tasman Sea using novel microsatellite markers. Jasus edwardsii is a keystone species of subtidal rocky reef system and supports lucrative export markets in both Australia and New Zealand. Eight highly polymorphic microsatellite markers were developed from 454 sequence data and screened across a Wellington south coast population to obtain basic diversity indices. All loci were polymorphic with the number of alleles per locus ranging from 6-39. Observed and expected heterozygosity ranged from 0.563-0.937 and 0.583-0.961, respectively. There were no significant deviations from Hardy-Weinberg equilibrium following standard Bonferroni corrections. The loci were used in a population analysis of J. edwardsii that spanned 10 degrees of latitude and stretched 3,500 km across the South Pacific. The analysis rejected the null-hypothesis of panmixia based on earlier mDNA analysis and revealed significant population structure (FST=0.011, RST=0.028) at a wide range of scales. Stewart Island was determined to have the highest levels of genetic differentiation of all populations sampled suggesting a high degree of reproductive isolation and self-recruitment. This study also identified high levels of asymmetric gene flow from Australia to New Zealand indicating a historical source-sink relationship between the two countries. Results from the genetic analysis were consistent with results from oceanographic dispersal models and it is likely that the genetic results reflect historical and contemporary patterns of Jasus edwardsii dispersal and recruitment throughout its range.</p>

scholarly journals Sympatry drives colour and song evolution in wood-warblers (Parulidae)

2021 ◽  
Vol 288 (1942) ◽  
pp. 20202804
Author(s):  
Richard K. Simpson ◽  
David R. Wilson ◽  
Allison F. Mistakidis ◽  
Daniel J. Mennill ◽  
Stéphanie M. Doucet
Keyword(s):  
Related Species ◽  
Species Recognition ◽  
Sympatric Species ◽  
Signal Evolution ◽  
Wood Warblers ◽  
Mixed Support ◽  
Species Pairs ◽  
Song Divergence ◽  
Signal Diversity ◽  
Signal Divergence

Closely related species often exhibit similarities in appearance and behaviour, yet when related species exist in sympatry, signals may diverge to enhance species recognition. Prior comparative studies provided mixed support for this hypothesis, but the relationship between sympatry and signal divergence is likely nonlinear. Constraints on signal diversity may limit signal divergence, especially when large numbers of species are sympatric. We tested the effect of sympatric overlap on plumage colour and song divergence in wood-warblers (Parulidae), a speciose group with diverse visual and vocal signals. We also tested how number of sympatric species influences signal divergence. Allopatric species pairs had overall greater plumage and song divergence compared to sympatric species pairs. However, among sympatric species pairs, plumage divergence positively related to the degree of sympatric overlap in males and females, while male song bandwidth and syllable rate divergence negatively related to sympatric overlap. In addition, as the number of species in sympatry increased, average signal divergence among sympatric species decreased, which is likely due to constraints on warbler perceptual space and signal diversity. Our findings reveal that sympatry influences signal evolution in warblers, though not always as predicted, and that number of sympatric species can limit sympatry's influence on signal evolution.

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