Limits...
Travelling in time with networks: Revealing present day hybridization versus ancestral polymorphism between two species of brown algae, Fucus vesiculosus and F. spiralis.

Moalic Y, Arnaud-Haond S, Perrin C, Pearson GA, Serrao EA - BMC Evol. Biol. (2011)

Bottom Line: Individual-centered networks were analyzed on the basis of microsatellite genotypes from North Africa to the Pacific American coast, through the North Atlantic.Two genetic distances integrating different time steps were used, the Rozenfeld (RD; based on alleles divergence) and the Shared Allele (SAD; based on alleles identity) distances.Intermediate individuals linking both clusters on the RD network were those sampled at the limits of the sympatric zone in Northwest Iberia.

View Article: PubMed Central - HTML - PubMed

Affiliation: IFREMER, Institut Français de Recherche pour l'Exploitation de la Mer, centre de Brest, BP70, 29280 Plouzané, France.

ABSTRACT

Background: Hybridization or divergence between sympatric sister species provides a natural laboratory to study speciation processes. The shared polymorphism in sister species may either be ancestral or derive from hybridization, and the accuracy of analytic methods used thus far to derive convincing evidence for the occurrence of present day hybridization is largely debated.

Results: Here we propose the application of network analysis to test for the occurrence of present day hybridization between the two species of brown algae Fucus spiralis and F. vesiculosus. Individual-centered networks were analyzed on the basis of microsatellite genotypes from North Africa to the Pacific American coast, through the North Atlantic. Two genetic distances integrating different time steps were used, the Rozenfeld (RD; based on alleles divergence) and the Shared Allele (SAD; based on alleles identity) distances. A diagnostic level of genotype divergence and clustering of individuals from each species was obtained through RD while screening for exchanges through putative hybridization was facilitated using SAD. Intermediate individuals linking both clusters on the RD network were those sampled at the limits of the sympatric zone in Northwest Iberia.

Conclusion: These results suggesting rare hybridization were confirmed by simulation of hybrids and F2 with directed backcrosses. Comparison with the Bayesian method STRUCTURE confirmed the usefulness of both approaches and emphasized the reliability of network analysis to unravel and study hybridization.

Show MeSH
Network topology of F. spiralis and F. vesiculosus individuals + simulated hybrids with the SAD. Only links with value smaller than or equal to the threshold values are present. Nodes representing individuals are circles for F. spiralis and squares for F. vesiculosus. Nodes representing hybrids are triangles. Colors correspond to geographical regions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3040711&req=5

Figure 3: Network topology of F. spiralis and F. vesiculosus individuals + simulated hybrids with the SAD. Only links with value smaller than or equal to the threshold values are present. Nodes representing individuals are circles for F. spiralis and squares for F. vesiculosus. Nodes representing hybrids are triangles. Colors correspond to geographical regions.

Mentions: The topologies of derived networks were compared across the 4 hybrids datasets at decreasing thresholds, 0.39, 0.33 and 0.28 (Figure 3) allowing networks to pass from a connected state to a disconnected one preventing gene flow between the two species. At the threshold of 0.39, F_spi are connected to F_ves through synthetic hybrids for all datasets. Nevertheless, differences appear during the decrease of the threshold highlighting the closer behavior of BC_F_ves and BC_F_spi_F_ves hybrids datasets to the initial natural dataset than hybrids F1 and BC_F_spi.


Travelling in time with networks: Revealing present day hybridization versus ancestral polymorphism between two species of brown algae, Fucus vesiculosus and F. spiralis.

Moalic Y, Arnaud-Haond S, Perrin C, Pearson GA, Serrao EA - BMC Evol. Biol. (2011)

Network topology of F. spiralis and F. vesiculosus individuals + simulated hybrids with the SAD. Only links with value smaller than or equal to the threshold values are present. Nodes representing individuals are circles for F. spiralis and squares for F. vesiculosus. Nodes representing hybrids are triangles. Colors correspond to geographical regions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3040711&req=5

Figure 3: Network topology of F. spiralis and F. vesiculosus individuals + simulated hybrids with the SAD. Only links with value smaller than or equal to the threshold values are present. Nodes representing individuals are circles for F. spiralis and squares for F. vesiculosus. Nodes representing hybrids are triangles. Colors correspond to geographical regions.
Mentions: The topologies of derived networks were compared across the 4 hybrids datasets at decreasing thresholds, 0.39, 0.33 and 0.28 (Figure 3) allowing networks to pass from a connected state to a disconnected one preventing gene flow between the two species. At the threshold of 0.39, F_spi are connected to F_ves through synthetic hybrids for all datasets. Nevertheless, differences appear during the decrease of the threshold highlighting the closer behavior of BC_F_ves and BC_F_spi_F_ves hybrids datasets to the initial natural dataset than hybrids F1 and BC_F_spi.

Bottom Line: Individual-centered networks were analyzed on the basis of microsatellite genotypes from North Africa to the Pacific American coast, through the North Atlantic.Two genetic distances integrating different time steps were used, the Rozenfeld (RD; based on alleles divergence) and the Shared Allele (SAD; based on alleles identity) distances.Intermediate individuals linking both clusters on the RD network were those sampled at the limits of the sympatric zone in Northwest Iberia.

View Article: PubMed Central - HTML - PubMed

Affiliation: IFREMER, Institut Français de Recherche pour l'Exploitation de la Mer, centre de Brest, BP70, 29280 Plouzané, France.

ABSTRACT

Background: Hybridization or divergence between sympatric sister species provides a natural laboratory to study speciation processes. The shared polymorphism in sister species may either be ancestral or derive from hybridization, and the accuracy of analytic methods used thus far to derive convincing evidence for the occurrence of present day hybridization is largely debated.

Results: Here we propose the application of network analysis to test for the occurrence of present day hybridization between the two species of brown algae Fucus spiralis and F. vesiculosus. Individual-centered networks were analyzed on the basis of microsatellite genotypes from North Africa to the Pacific American coast, through the North Atlantic. Two genetic distances integrating different time steps were used, the Rozenfeld (RD; based on alleles divergence) and the Shared Allele (SAD; based on alleles identity) distances. A diagnostic level of genotype divergence and clustering of individuals from each species was obtained through RD while screening for exchanges through putative hybridization was facilitated using SAD. Intermediate individuals linking both clusters on the RD network were those sampled at the limits of the sympatric zone in Northwest Iberia.

Conclusion: These results suggesting rare hybridization were confirmed by simulation of hybrids and F2 with directed backcrosses. Comparison with the Bayesian method STRUCTURE confirmed the usefulness of both approaches and emphasized the reliability of network analysis to unravel and study hybridization.

Show MeSH