scholarly journals Intrinsic reproductive isolating mechanisms in the maintenance of a hybrid zone between ecologically divergent subspecies

2017 ◽  
Vol 30 (4) ◽  
pp. 848-864 ◽  
Author(s):  
J. L. McKenzie ◽  
C. Bucking ◽  
A. Moreira ◽  
P. M. Schulte
Keyword(s):  
Hybrid Zone ◽  
Isolating Mechanisms

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.

RELATIVE ABUNDANCE AND THE SPECIES-SPECIFIC REINFORCEMENT OF MALE MATING PREFERENCE IN THE CHRYSOCHUS (COLEOPTERA: CHRYSOMELIDAE) HYBRID ZONE

Evolution ◽  
2005 ◽  
Vol 59 (12) ◽  
pp. 2639 ◽  
Author(s):  
Merrill A. Peterson ◽  
Barbara M. Honchak ◽  
Stefanie E. Locke ◽  
Timothy E. Beeman ◽  
Jessica Mendoza ◽  
...  
Keyword(s):  
Relative Abundance ◽  
Hybrid Zone ◽  
Mating Preference ◽  
Male Mating ◽  
Species Specific

Behavioral Stabilization of a Baboon Hybrid Zone

1975 ◽  
Vol 109 (970) ◽  
pp. 701-712 ◽  
Author(s):  
Stephen A. Gabow
Keyword(s):  
Hybrid Zone

scholarly journals Differences in dietary composition and preference maintained despite gene flow across a woodrat hybrid zone

2021 ◽  
Author(s):  
Danny P. Nielsen ◽  
Marjorie D. Matocq
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Dietary Composition

scholarly journals Sixty Years After “Isolating Mechanisms, Evolution and Temperature”: Muller's Legacy

Genetics ◽  
2002 ◽  
Vol 161 (3) ◽  
pp. 939-944
Author(s):  
Norman A Johnson
Keyword(s):  
Isolating Mechanisms

Evolution of Some Arctic Gulls (Larus): An Experimental Study of Isolating Mechanisms

1966 ◽  
pp. 1-99 ◽  
Author(s):  
Neal Griffith Smith
Keyword(s):  
Experimental Study ◽  
Isolating Mechanisms

scholarly journals X-Linked Signature of Reproductive Isolation in Humans is Mirrored in a Howler Monkey Hybrid Zone

2020 ◽  
Vol 111 (5) ◽  
pp. 419-428 ◽  
Author(s):  
Marcella D Baiz ◽  
Priscilla K Tucker ◽  
Jacob L Mueller ◽  
Liliana Cortés-Ortiz
Keyword(s):  
Reproductive Isolation ◽  
X Chromosome ◽  
Hybrid Zone ◽  
Sex Chromosome ◽  
Genomic Sequence ◽  
Alouatta Palliata ◽  
Model Systems ◽  
Howler Monkey ◽  
Autosomal Snps ◽  
Outlier Region

Abstract Reproductive isolation is a fundamental step in speciation. While sex chromosomes have been linked to reproductive isolation in many model systems, including hominids, genetic studies of the contribution of sex chromosome loci to speciation for natural populations are relatively sparse. Natural hybrid zones can help identify genomic regions contributing to reproductive isolation, like hybrid incompatibility loci, since these regions exhibit reduced introgression between parental species. Here, we use a primate hybrid zone (Alouatta palliata × Alouatta pigra) to test for reduced introgression of X-linked SNPs compared to autosomal SNPs. To identify X-linked sequence in A. palliata, we used a sex-biased mapping approach with whole-genome re-sequencing data. We then used genomic cline analysis with reduced-representation sequence data for parental A. palliata and A. pigra individuals and hybrids (n = 88) to identify regions with non-neutral introgression. We identified ~26 Mb of non-repetitive, putatively X-linked genomic sequence in A. palliata, most of which mapped collinearly to the marmoset and human X chromosomes. We found that X-linked SNPs had reduced introgression and an excess of ancestry from A. palliata as compared to autosomal SNPs. One outlier region with reduced introgression overlaps a previously described “desert” of archaic hominin ancestry on the human X chromosome. These results are consistent with a large role for the X chromosome in speciation across animal taxa and further, suggest shared features in the genomic basis of the evolution of reproductive isolation in primates.

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