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Evolutionary experimentation through hybridization under laboratory condition in Drosophila: evidence for recombinational speciation.

Harini BP, Ramachandra NB - BMC Evol. Biol. (2003)

Bottom Line: Each of these Cytoraces is composed of recombined genomes of the parental races.The results reveal that in most cases, the newly evolved Cytoraces, with different chromosome constitutions, exhibit decreased body size, better fitness and live longer than their parents.Particularly, Cytorace 5, 6 and 8 have evolved with very much higher range values of quantitative traits than the parents and other Cytoraces, which suggests the role of transgressive segregation in the evolution of these Cytoraces.

View Article: PubMed Central - HTML - PubMed

Affiliation: Drosophila stock centre, Department of Studies in Zoology University of Mysore Manasagangotri Mysore-570 006, India. bpharini@hotmail.com

ABSTRACT

Background: Drosophila nasuta nasuta (2n = 8) and Drosophila nasuta albomicans (2n = 6) are a pair of sibling allopatric chromosomal cross-fertile races of the nasuta subgroup of immigrans species group of Drosophila. Interracial hybridization between these two races has given rise to new karyotypic strains called Cytorace 1 and Cytorace 2 (first phase). Further hybridization between Thailand strain of D. n. albomicans and D. n. nasuta of Coorg strain has resulted in the evolution of two more Cytoraces, namely Cytorace 3 and Cytorace 4 (second phase). The third phase Cytoraces (Cytorace 5 to Cytorace 16) have evolved through interracial hybridization among first, second phase Cytoraces along with parental races. Each of these Cytoraces is composed of recombined genomes of the parental races. Here, we have made an attempt to systematically assess the impact of hybridization on karyotypes, morphometric and life history traits in all 16 Cytoraces.

Results: The results reveal that in most cases, the newly evolved Cytoraces, with different chromosome constitutions, exhibit decreased body size, better fitness and live longer than their parents. Particularly, Cytorace 5, 6 and 8 have evolved with very much higher range values of quantitative traits than the parents and other Cytoraces, which suggests the role of transgressive segregation in the evolution of these Cytoraces.

Conclusion: Thus, the rapid divergence recorded in the chromosomes, karyotypes, body size and fitness traits of Cytoraces exhibit the early event of recombinational raciation / speciation in the evolution of the Cytoraces under laboratory conditions.

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Evidence for recombination and transgressive segregation of quantitative traits analysed in 18 members of the nasuta-albomicans complex of Drosophila. Correlation of Euclidean distance dissimilarity (Table 8) is computed to the traits assessed separately in males (7 traits), females (8 traits) and both males and females together (5 traits). Based on these values, the members are classified into three ranges, namely parental range, higher range and lower range. Many of these newly evolved Cytoraces are more fit in the laboratory than their parental species and exhibit phenotypes that are extreme relative to either parent. The generation of extreme phenotypes through recombination in segregating hybrids is referred to as transgressive segregation.
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Figure 7: Evidence for recombination and transgressive segregation of quantitative traits analysed in 18 members of the nasuta-albomicans complex of Drosophila. Correlation of Euclidean distance dissimilarity (Table 8) is computed to the traits assessed separately in males (7 traits), females (8 traits) and both males and females together (5 traits). Based on these values, the members are classified into three ranges, namely parental range, higher range and lower range. Many of these newly evolved Cytoraces are more fit in the laboratory than their parental species and exhibit phenotypes that are extreme relative to either parent. The generation of extreme phenotypes through recombination in segregating hybrids is referred to as transgressive segregation.

Mentions: Correlation analysis based on the Euclidean distance dissimilarity in 18 members of the NAC complex of Drosophila is compiled in Table 8 - Additional file: 1. The traits used for male, female and both male and female together analysis were 7 (wing length and width, genitalia length and width, body weight, longevity in unmated and mated males), 8 (wing length and width, body weight, lifetime fecundity, ovariole numbers, lifetime fertility, longevity in virgin and mated females) and 5 (wing length and width, body weight, longevity in virgin and mated flies) respectively. The Euclidean distance between two values is the arithmetic difference. The minimum value is 0, and it has no upper limit. Based on this, Cytorace 8 had the maximum distance from D. n. nasuta and D. n. albomicans than other Cytoraces. Figure 7 illustrates the Cytoraces, which deviate with higher and lower range of Euclidean distance from the parental range. Interestingly, some of the 3rd phase Cytoraces have higher range of Euclidean distance with D. n. nasuta, D. n. albomicans, Cytorace 2 and Cytoraces 1. In particular, Cytorace 5, Cytorace 6 and Cytorace 8 had maximum divergence with D. n. nasuta and D. n. albomicans. While some of the 3rd phase and 2nd phase Cytoraces had minimum divergence among themselves indicating the role of hybrid recombination followed by segregation of parental genes during the evolution of these Cytoraces (Fig. 7).


Evolutionary experimentation through hybridization under laboratory condition in Drosophila: evidence for recombinational speciation.

Harini BP, Ramachandra NB - BMC Evol. Biol. (2003)

Evidence for recombination and transgressive segregation of quantitative traits analysed in 18 members of the nasuta-albomicans complex of Drosophila. Correlation of Euclidean distance dissimilarity (Table 8) is computed to the traits assessed separately in males (7 traits), females (8 traits) and both males and females together (5 traits). Based on these values, the members are classified into three ranges, namely parental range, higher range and lower range. Many of these newly evolved Cytoraces are more fit in the laboratory than their parental species and exhibit phenotypes that are extreme relative to either parent. The generation of extreme phenotypes through recombination in segregating hybrids is referred to as transgressive segregation.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC240057&req=5

Figure 7: Evidence for recombination and transgressive segregation of quantitative traits analysed in 18 members of the nasuta-albomicans complex of Drosophila. Correlation of Euclidean distance dissimilarity (Table 8) is computed to the traits assessed separately in males (7 traits), females (8 traits) and both males and females together (5 traits). Based on these values, the members are classified into three ranges, namely parental range, higher range and lower range. Many of these newly evolved Cytoraces are more fit in the laboratory than their parental species and exhibit phenotypes that are extreme relative to either parent. The generation of extreme phenotypes through recombination in segregating hybrids is referred to as transgressive segregation.
Mentions: Correlation analysis based on the Euclidean distance dissimilarity in 18 members of the NAC complex of Drosophila is compiled in Table 8 - Additional file: 1. The traits used for male, female and both male and female together analysis were 7 (wing length and width, genitalia length and width, body weight, longevity in unmated and mated males), 8 (wing length and width, body weight, lifetime fecundity, ovariole numbers, lifetime fertility, longevity in virgin and mated females) and 5 (wing length and width, body weight, longevity in virgin and mated flies) respectively. The Euclidean distance between two values is the arithmetic difference. The minimum value is 0, and it has no upper limit. Based on this, Cytorace 8 had the maximum distance from D. n. nasuta and D. n. albomicans than other Cytoraces. Figure 7 illustrates the Cytoraces, which deviate with higher and lower range of Euclidean distance from the parental range. Interestingly, some of the 3rd phase Cytoraces have higher range of Euclidean distance with D. n. nasuta, D. n. albomicans, Cytorace 2 and Cytoraces 1. In particular, Cytorace 5, Cytorace 6 and Cytorace 8 had maximum divergence with D. n. nasuta and D. n. albomicans. While some of the 3rd phase and 2nd phase Cytoraces had minimum divergence among themselves indicating the role of hybrid recombination followed by segregation of parental genes during the evolution of these Cytoraces (Fig. 7).

Bottom Line: Each of these Cytoraces is composed of recombined genomes of the parental races.The results reveal that in most cases, the newly evolved Cytoraces, with different chromosome constitutions, exhibit decreased body size, better fitness and live longer than their parents.Particularly, Cytorace 5, 6 and 8 have evolved with very much higher range values of quantitative traits than the parents and other Cytoraces, which suggests the role of transgressive segregation in the evolution of these Cytoraces.

View Article: PubMed Central - HTML - PubMed

Affiliation: Drosophila stock centre, Department of Studies in Zoology University of Mysore Manasagangotri Mysore-570 006, India. bpharini@hotmail.com

ABSTRACT

Background: Drosophila nasuta nasuta (2n = 8) and Drosophila nasuta albomicans (2n = 6) are a pair of sibling allopatric chromosomal cross-fertile races of the nasuta subgroup of immigrans species group of Drosophila. Interracial hybridization between these two races has given rise to new karyotypic strains called Cytorace 1 and Cytorace 2 (first phase). Further hybridization between Thailand strain of D. n. albomicans and D. n. nasuta of Coorg strain has resulted in the evolution of two more Cytoraces, namely Cytorace 3 and Cytorace 4 (second phase). The third phase Cytoraces (Cytorace 5 to Cytorace 16) have evolved through interracial hybridization among first, second phase Cytoraces along with parental races. Each of these Cytoraces is composed of recombined genomes of the parental races. Here, we have made an attempt to systematically assess the impact of hybridization on karyotypes, morphometric and life history traits in all 16 Cytoraces.

Results: The results reveal that in most cases, the newly evolved Cytoraces, with different chromosome constitutions, exhibit decreased body size, better fitness and live longer than their parents. Particularly, Cytorace 5, 6 and 8 have evolved with very much higher range values of quantitative traits than the parents and other Cytoraces, which suggests the role of transgressive segregation in the evolution of these Cytoraces.

Conclusion: Thus, the rapid divergence recorded in the chromosomes, karyotypes, body size and fitness traits of Cytoraces exhibit the early event of recombinational raciation / speciation in the evolution of the Cytoraces under laboratory conditions.

Show MeSH
Related in: MedlinePlus