Reproductive isolation with little genetic divergence between Urticina (=Tealia) felina and U. eques (Anthozoa: Actiniaria)

1985 ◽  
Vol 85 (3) ◽  
pp. 279-284 ◽  
Author(s):  
A. M. Sol�-Cava ◽  
J. P. Thorpe ◽  
J. G. Kaye
Keyword(s):  
Reproductive Isolation ◽  
Genetic Divergence

scholarly journals Genetic divergence predicts reproductive isolation in damselflies

2013 ◽  
Vol 27 (1) ◽  
pp. 76-87 ◽  
Author(s):  
R. A. Sánchez-Guillén ◽  
A. Córdoba-Aguilar ◽  
A. Cordero-Rivera ◽  
M. Wellenreuther
Keyword(s):  
Reproductive Isolation ◽  
Genetic Divergence

scholarly journals Spiraling Complexity: A Test of the Snowball Effect in a Computational Model of RNA Folding

2016 ◽  
Author(s):  
Ata Kalirad ◽  
Ricardo B. R. Azevedo
Keyword(s):  
Reproductive Isolation ◽  
Computational Model ◽  
Genetic Divergence ◽  
Rna Folding ◽  
Fitness Landscape ◽  
Natural Populations ◽  
Using Data ◽  
Two Populations ◽  
Snowball Effect

ABSTRACTGenetic incompatibilities can emerge as a by-product of genetic divergence. According to Dobzhansky and Muller, an allele that fixes in one population may be incompatible with an allele at a different locus in another population when the two alleles are brought together in hybrids. Orr showed that the number of Dobzhansky–Muller incompatibilities (DMIs) should accumulate faster than linearly—i.e., snowball—as two lineages diverge. Several studies have attempted to test the snowball effect using data from natural populations. One limitation of these studies is that they have focused on predictions of the Orr model but not on its underlying assumptions. Here we use a computational model of RNA folding to test both predictions and assumptions of the Orr model. Two populations are allowed to evolve in allopatry on a holey fitness landscape. We find that the number of inviable introgressions (an indicator for the number of DMIs) snowballs, but does so more slowly than expected. We show that this pattern is explained, in part, by the fact that DMIs can disappear after they have arisen, contrary to the assumptions of the Orr model. This occurs because DMIs become progressively more complex (i.e., involve alleles at more loci) as a result of later substitutions. We also find that most DMIs involve more than two loci—i.e., they are complex. Reproductive isolation does not snowball because DMIs do not act independently of each other. We conclude that the RNA model supports the central prediction of the Orr model that the number of DMIs snowballs, but challenges other predictions, as well as some of its underlying assumptions.

scholarly journals Whole-genome resequencing confirms reproductive isolation between sympatric demes of brown trout (Salmo trutta) detected with allozymes

2021 ◽  
Author(s):  
Atal Saha ◽  
Anastasia Andersson ◽  
Sara Kurland ◽  
Naomi Keehnen ◽  
Verena Esther Kutschera ◽  
...  
Keyword(s):  
Reproductive Isolation ◽  
Brown Trout ◽  
Genetic Divergence ◽  
Salmo Trutta ◽  
Sequence Data ◽  
Whole Genome ◽  
Similar Data ◽  
Genome Resequencing ◽  
Genome Wide ◽  
Whole Genome Resequencing

The sympatric existence of genetically distinct populations of the same species remains a puzzle in ecology. Coexisting salmonid fish populations are known from over 100 freshwater lakes. Most studies of sympatric populations have used limited numbers of genetic markers making it unclear if genetic divergence involves only certain parts of the genome. We return to the first reported case of salmonid sympatry, initially detected through contrasting homozygosity at a single allozyme locus (lactate dehydrogenase, LDH-A1) in brown trout in the small Lakes Bunnersjöarna, central Sweden. We use DNA from samples collected in the 1970s and a 96 SNP fluidigm array to verify the existence of the coexisting demes. We then apply whole-genome resequencing of pooled DNA to explore genome-wide diversity within and between these demes; strong genetic divergence is observed with genome-wide FST=0.13. Nucleotide diversity is estimated to 0.0013 in Deme I but only 0.0005 in Deme II. Individual whole-genome resequencing of two individuals per deme suggests considerably higher inbreeding in Deme II vs. Deme I. Comparing with similar data from other lakes we find that the genome-wide divergence between the demes is similar to that between reproductively isolated populations. We located two genes for LDH-A and found divergence between the demes in a regulatory section of one of the genes, but we could not find a perfect fit between allozyme and sequence data. Our data demonstrate genome-wide divergence governed by genetic drift and diversifying selection, confirming reproductive isolation between the sympatric demes.

scholarly journals Genetic divergence and the number of hybridizing species affect the path to homoploid hybrid speciation

2018 ◽  
Vol 115 (39) ◽  
pp. 9761-9766 ◽  
Author(s):  
Aaron A. Comeault ◽  
Daniel R. Matute
Keyword(s):  
Genetic Diversity ◽  
Reproductive Isolation ◽  
Genetic Divergence ◽  
Adaptive Systems ◽  
Parental Species ◽  
Hybrid Speciation ◽  
Hybrid Species ◽  
Empirical Question ◽  
Homoploid Hybrid

Hybridization is often maladaptive and in some instances has led to the loss of biodiversity. However, hybridization can also promote speciation, such as during homoploid hybrid speciation, thereby generating biodiversity. Despite examples of homoploid hybrid species, the importance of hybridization as a speciation mechanism is still widely debated, and we lack a general understanding of the conditions most likely to generate homoploid hybrid species. Here we show that the level of genetic divergence between hybridizing species has a large effect on the probability that their hybrids evolve reproductive isolation. We find that populations of hybrids formed by parental species with intermediate levels of divergence were more likely to mate assortatively, and discriminate against their parental species, than those generated from weakly or strongly diverged parental species. Reproductive isolation was also found between hybrid populations, suggesting differential sorting of parental traits across populations. Finally, hybrid populations derived from three species were more likely to evolve reproductive isolation than those derived from two species, supporting arguments that hybridization-supplied genetic diversity can lead to the evolution of novel “adaptive systems” and promote speciation. Our results illustrate when we expect hybridization and admixture to promote hybrid speciation. Whether homoploid hybrid speciation is a common speciation mechanism in general remains an outstanding empirical question.

Isolating Mechanisms in Threespine Sticklebacks (Gasterosteus)

1967 ◽  
Vol 24 (8) ◽  
pp. 1637-1692 ◽  
Author(s):  
D. W. Hagen
Keyword(s):  
Reproductive Isolation ◽  
Hybrid Zone ◽  
Genetic Divergence ◽  
Progressive Increase ◽  
Hybrid Zones ◽  
Genetic Incompatibility ◽  
Species Definition ◽  
Isolating Mechanisms ◽  
Ecological Isolation ◽  
Threespine Sticklebacks

A systematic examination was made of isolating mechanisms, as set out by Mayr, that might serve to maintain reproductive isolation between the marine (trachurus) and the freshwater (leiurus) threespine sticklebacks. Field work was conducted in a small British Columbia coastal stream, the Little Campbell River, for[Formula: see text] years and complemented with laboratory experiments. Other streams were included late in the investigation. Leiurus permanently occupies the upper reaches of the stream; trachurus is anadromous and enters the lower reaches to breed in freshwater. Between the breeding grounds of the two, where numbers of both are greatly reduced, hybridization occurs. But it is restricted to a narrow zone.The two species are easily distinguished. Thus, morphological analysis provided firm circumstantial evidence that hybrids are plentiful and that backcrossing occurs, predominately to leiurus. Hybridization was confirmed by rearing offspring under uniform conditions in the laboratory with crosses in all combinations. Such offspring were also used to demonstrate considerable genetic divergence (much of it polygenetic) between leiurus and trachurus.Behavioural experiments demonstrated the absence of ethological isolation and hybrids performed courtship and parental care normally.Nor was genetic incompatibility found in the reared hybrids (F1's or backcrosses); all were vigourous. Seasonal isolation is only partially developed with early spawning migrants of trachurus making a major contribution to hybridization (in the Little Campbell River).Since behavioural and genetic blocks to hybridization are not present, there is no means to prevent hybridization where leiurus and trachurus come together. However, coexistence between the two species is very low. Evidence from observation and experiment in the field and from preference tests showed that ecological isolation is a very powerful barrier to hybridization. The two species show numerous adaptations to the distinctly different habitats they frequent, and each shows a strong affinity for its own habitat. In localities with intermediate or contiguous habitats, coexistence and interbreeding occur. Hybridization is a function of the environment.No selection against hybrids could be detected within the hybrid zone (or with laboratory reared hybrids); yet, one is forced to assume that it is present outside the zone. The very narrow zones as well as the reversed cline that were found indicate there is intense selection against hybrids. What these selective forces are remains to be found. Hybrid zones will probably continue to be poorly understood until a critical analysis of hybrid inferiority is made.Genotypes of either species that remain in the hybrid zone are at a strong selective disadvantage. Hence, reinforcement of ecological isolation probably occurs, and Moore's criticism concerning the spread of such reinforced genotypes would not apply to such cases. Mayr distinguishes between pre- and postmating mechanisms stating that the mode of operation of natural selection will be different for the two. But in threespine sticklebacks one premating mechanism (ecological isolation) and one postmating mechanism (hybrid inferiority) cannot be distinguished. This is so because ecological isolation is the cause of hybrid inferiority.Leiurus and trachurus are reproductively isolated, have well developed isolating mechanisms, and exhibit considerable genetic divergence. The two, then, fulfill the species definition of Mayr. There is no evidence that introgression occurs. Indeed a reversed cline showing a progressive increase in morphological divergence between the two species as the hybrid zone is approached together with the narrow hybrid zone demonstrates that selection severely restricts gene flow. Collections and observations from other streams corroborate those from the study area. Reproductive isolation between leiurus and trachurus seems to be widespread, throughout their range.

scholarly journals Are genetically distinct lizard species able to hybridize? A review

2015 ◽  
Vol 61 (1) ◽  
pp. 155-180 ◽  
Author(s):  
Jitka Jančúchová-Lásková ◽  
Eva Landová ◽  
Daniel Frynta
Keyword(s):  
Reproductive Isolation ◽  
Genetic Divergence ◽  
Divergence Time ◽  
Distinct Species ◽  
F1 Hybrids ◽  
Lizard Species ◽  
And Bisexual ◽  
Reproductive Isolation Mechanisms ◽  
Cyt B Gene ◽  
The Relationship

Abstract Animal species are delimited by reproductive isolation mechanisms (RIMs). Postzygotic RIMs are mainly products of genetic differences and thus their strength increases with elapsed divergence time. The relationship between postzygotic reproductive isolation and genetic divergence, however, differs considerably among major clades of vertebrates. We reviewed the available literature providing empirical evidence of natural and/or experimental hybridization between distinct species of lizards (squamates except snakes). We found that hybridization events are widely distributed among nearly all major lizard clades. The majority of research focuses on parthenogenetic species and/or polyploid hybrids in families Lacertidae, Teiidae and Gekkonidae. Homoploid bisexual hybrids are mainly reported within Lacertidae and Iguania groups. As a proxy of genetic divergence of the hybridizing taxa we adopted nucleotide sequence distance (HKY85) of mitochondrial cyt b gene. The upper limit of genetic divergence was similar with regard to both parthenogenetic and bisexual hybrids. Maximum values of these distances between hybridizing species of lizards approached 18%?21%, which is comparable to or even exceeds the corresponding values reported for other principal clades of vertebrates. In spite of this, F1 hybrids are typically at least partially fertile in lizards and thus genetic in-trogression between highly divergent species is possible. The relationship between the genetic distance and hybrid fertility was not found.

Genetic Divergence and Reproductive Isolation in the Genus Fejervarya (Amphibia: Anura) from Bangladesh Inferred from Morphological Observations, Crossing Experiments, and Molecular Analyses

2008 ◽  
Vol 25 (11) ◽  
pp. 1084-1105 ◽  
Author(s):  
Mohammed Mafizul Islam ◽  
Naoko Kurose ◽  
MdMukhlesur Rahman Khan ◽  
Toshitaka Nishizawa ◽  
Mitsuru Kuramoto ◽  
...  
Keyword(s):  
Reproductive Isolation ◽  
Genetic Divergence ◽  
Crossing Experiments ◽  
Molecular Analyses
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