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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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Related in: MedlinePlus

Based on the DMR test, 18 members of the nasuta-albomicans complex of Drosophila are constructed into clusters and named in the hierarchical form from the lowest to the highest mean body weight in 2 days old flies. The members belonging to each clusters have insignificant differences. In males, Cytorace 8 formed an independent cluster, while all others with 7 overlapping clusters (Fig. 4a). In females, six clusters are recognised, of which, cluster 1 to 3 are clustered together while cluster 4 (C11 & C9) has formed an independent cluster. In addition to this, cluster 5 and 6 are also overlapped each other and independent from the other clusters (Fig. 4b). In both males and females, 5 clusters are recognised, of which, cluster 1 and 2 are overlapped with each other, while cluster 3 (C2, C11, and C4), cluster 4 (C13, C14, C7, C6 and C9) and cluster 5 (C8) are formed as independent clusters.
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Figure 4: Based on the DMR test, 18 members of the nasuta-albomicans complex of Drosophila are constructed into clusters and named in the hierarchical form from the lowest to the highest mean body weight in 2 days old flies. The members belonging to each clusters have insignificant differences. In males, Cytorace 8 formed an independent cluster, while all others with 7 overlapping clusters (Fig. 4a). In females, six clusters are recognised, of which, cluster 1 to 3 are clustered together while cluster 4 (C11 & C9) has formed an independent cluster. In addition to this, cluster 5 and 6 are also overlapped each other and independent from the other clusters (Fig. 4b). In both males and females, 5 clusters are recognised, of which, cluster 1 and 2 are overlapped with each other, while cluster 3 (C2, C11, and C4), cluster 4 (C13, C14, C7, C6 and C9) and cluster 5 (C8) are formed as independent clusters.

Mentions: The mean body weight of 2 days old flies (Table 5) in 18 members of the NAC of Drosophila revealed that females show increased body weight than males. The males of Cytorace 10 and Cytorace 8 had lesser and greater body weight respectively, while in females and both males and females together, D. n. nasuta and Cytorace 8 has decreased and increased body weight respectively, however, the difference between the values of D. n. nasuta and Cytorace 10 is insignificant (Fig. 4). Most of the Cytoraces have increased body weight than parental races. These results are contrasting with the other body size traits indicating that body weight trait is independent of body size traits.


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

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

Based on the DMR test, 18 members of the nasuta-albomicans complex of Drosophila are constructed into clusters and named in the hierarchical form from the lowest to the highest mean body weight in 2 days old flies. The members belonging to each clusters have insignificant differences. In males, Cytorace 8 formed an independent cluster, while all others with 7 overlapping clusters (Fig. 4a). In females, six clusters are recognised, of which, cluster 1 to 3 are clustered together while cluster 4 (C11 & C9) has formed an independent cluster. In addition to this, cluster 5 and 6 are also overlapped each other and independent from the other clusters (Fig. 4b). In both males and females, 5 clusters are recognised, of which, cluster 1 and 2 are overlapped with each other, while cluster 3 (C2, C11, and C4), cluster 4 (C13, C14, C7, C6 and C9) and cluster 5 (C8) are formed as independent clusters.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC240057&req=5

Figure 4: Based on the DMR test, 18 members of the nasuta-albomicans complex of Drosophila are constructed into clusters and named in the hierarchical form from the lowest to the highest mean body weight in 2 days old flies. The members belonging to each clusters have insignificant differences. In males, Cytorace 8 formed an independent cluster, while all others with 7 overlapping clusters (Fig. 4a). In females, six clusters are recognised, of which, cluster 1 to 3 are clustered together while cluster 4 (C11 & C9) has formed an independent cluster. In addition to this, cluster 5 and 6 are also overlapped each other and independent from the other clusters (Fig. 4b). In both males and females, 5 clusters are recognised, of which, cluster 1 and 2 are overlapped with each other, while cluster 3 (C2, C11, and C4), cluster 4 (C13, C14, C7, C6 and C9) and cluster 5 (C8) are formed as independent clusters.
Mentions: The mean body weight of 2 days old flies (Table 5) in 18 members of the NAC of Drosophila revealed that females show increased body weight than males. The males of Cytorace 10 and Cytorace 8 had lesser and greater body weight respectively, while in females and both males and females together, D. n. nasuta and Cytorace 8 has decreased and increased body weight respectively, however, the difference between the values of D. n. nasuta and Cytorace 10 is insignificant (Fig. 4). Most of the Cytoraces have increased body weight than parental races. These results are contrasting with the other body size traits indicating that body weight trait is independent of body size traits.

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