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Re-visiting phylogenetic and taxonomic relationships in the genus Saga (Insecta: Orthoptera).

Kolics B, Ács Z, Chobanov DP, Orci KM, Qiang LS, Kovács B, Kondorosy E, Decsi K, Taller J, Specziár A, Orbán L, Müller T - PLoS ONE (2012)

Bottom Line: The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only.After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies.The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences and Biotechnology, Georgikon Faculty, University of Pannonia, Keszthely, Hungary.

ABSTRACT
Twelve of the 13 bushcricket species of the Saga genus are bisexuals and diploids, except the parthenogenetic and tetraploid bush cricket, Saga pedo. Despite a continuous research effort stretching through the 1900s, the taxonomic relationships of the Saga species are still disputed. In this study, our primary aim was to reveal natural relationships of the European Saga species and three of their Asian relatives, with special attention to the problematic taxonomy of two subspecies: S. campbelli campbelli and S. c. gracilis. Following a phylogenetic analysis of eight species, a comprehensive study was carried out on the above three taxa by using acoustic and morphometric approaches in parallel. Our phylogenetic data showed that European Saga species evolved from a monophyletic lineage. The geographical transitional species S. cappadocica was positioned between European and Asian lineages supporting the idea that the European Saga lineage originated phylogeographically from the Asian clade. The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only. After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies. S. c. gracilis shares the same ITS2 haplotype with S. pedo, indicating that the latter could have evolved from populations of the former, probably through whole genome duplication. Based on acoustic and morphometric differences, we propose to elevate the two subspecies, S. campbelli campbelli and S. c. gracilis, to species level status, as Saga gracilis Kis 1962, and Saga campbelli Uvarov 1921. The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.

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Evolutionary relationship of Saga species estimated from the nuclear DNA sequences.Panel A: Maximum Parsimony phylogenetic tree of Saginae based on ITS2 sequences. The consistency index was 0.91, whereas the retention index was 0.966 for MP tree. The composite index was 0.888 for all sites and 0.879 for the parsimony-informative sites. There were a total of 829 positions in the final dataset, out of which 95 were parsimony-informative. Vertical bars at right indicate the species. Bootstrap values are presented at each node. The unrooted tree showed the S. ephippigera-ornata clade as most basal group. The transient S. cappadocica is positioned between the Asian S. ephippigera-ornata and the European Saga linegae (S. hellenica, S. rammei, S. pedo, S. c. gracilis, S. c. campbelli, S. natoliae). Panel B:Asian Saga species have a long insertion in their ITS2 sequence, compared to that of European species. Evolutionary relationship of the ITS2 insertions is presented in a Neighbor-Joining tree. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site.
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pone-0042229-g004: Evolutionary relationship of Saga species estimated from the nuclear DNA sequences.Panel A: Maximum Parsimony phylogenetic tree of Saginae based on ITS2 sequences. The consistency index was 0.91, whereas the retention index was 0.966 for MP tree. The composite index was 0.888 for all sites and 0.879 for the parsimony-informative sites. There were a total of 829 positions in the final dataset, out of which 95 were parsimony-informative. Vertical bars at right indicate the species. Bootstrap values are presented at each node. The unrooted tree showed the S. ephippigera-ornata clade as most basal group. The transient S. cappadocica is positioned between the Asian S. ephippigera-ornata and the European Saga linegae (S. hellenica, S. rammei, S. pedo, S. c. gracilis, S. c. campbelli, S. natoliae). Panel B:Asian Saga species have a long insertion in their ITS2 sequence, compared to that of European species. Evolutionary relationship of the ITS2 insertions is presented in a Neighbor-Joining tree. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site.

Mentions: The MP and Bayesian analyses based on ITS2 sequences showed a somewhat different tree topology (Fig. 4A). At the species level, the ITS2 locus of Saga species appeared to be more conserved than the mitochondrial loci. Both the MP and Bayesian trees shared the same clades, but showed a slightly different tree topology. Both analyses positioned the Asian clades ‘ephippigera-ornata’ and ‘cappadocica’ at the basis of the tree, and confirmed the monophyly of European Saga lineage (natoliae, hellenica, rammei, and pedo-campbelli). The three Asian Saga species, S. cappadocica, S.ephippigera and S. ornata samples had a long (155 bp) insertion in their ITS2 sequence, compared to that of European species. Although this insert was removed before the above two trees were built, we have looked at their evolutionary relationship by generating a Neighbour-Joining tree (Fig. S2B). In agreement with the two above trees, the NJ tree has shown that S. ephippigera and S. ornata were more closely related to each other than to S. cappadocica.


Re-visiting phylogenetic and taxonomic relationships in the genus Saga (Insecta: Orthoptera).

Kolics B, Ács Z, Chobanov DP, Orci KM, Qiang LS, Kovács B, Kondorosy E, Decsi K, Taller J, Specziár A, Orbán L, Müller T - PLoS ONE (2012)

Evolutionary relationship of Saga species estimated from the nuclear DNA sequences.Panel A: Maximum Parsimony phylogenetic tree of Saginae based on ITS2 sequences. The consistency index was 0.91, whereas the retention index was 0.966 for MP tree. The composite index was 0.888 for all sites and 0.879 for the parsimony-informative sites. There were a total of 829 positions in the final dataset, out of which 95 were parsimony-informative. Vertical bars at right indicate the species. Bootstrap values are presented at each node. The unrooted tree showed the S. ephippigera-ornata clade as most basal group. The transient S. cappadocica is positioned between the Asian S. ephippigera-ornata and the European Saga linegae (S. hellenica, S. rammei, S. pedo, S. c. gracilis, S. c. campbelli, S. natoliae). Panel B:Asian Saga species have a long insertion in their ITS2 sequence, compared to that of European species. Evolutionary relationship of the ITS2 insertions is presented in a Neighbor-Joining tree. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3420257&req=5

pone-0042229-g004: Evolutionary relationship of Saga species estimated from the nuclear DNA sequences.Panel A: Maximum Parsimony phylogenetic tree of Saginae based on ITS2 sequences. The consistency index was 0.91, whereas the retention index was 0.966 for MP tree. The composite index was 0.888 for all sites and 0.879 for the parsimony-informative sites. There were a total of 829 positions in the final dataset, out of which 95 were parsimony-informative. Vertical bars at right indicate the species. Bootstrap values are presented at each node. The unrooted tree showed the S. ephippigera-ornata clade as most basal group. The transient S. cappadocica is positioned between the Asian S. ephippigera-ornata and the European Saga linegae (S. hellenica, S. rammei, S. pedo, S. c. gracilis, S. c. campbelli, S. natoliae). Panel B:Asian Saga species have a long insertion in their ITS2 sequence, compared to that of European species. Evolutionary relationship of the ITS2 insertions is presented in a Neighbor-Joining tree. The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site.
Mentions: The MP and Bayesian analyses based on ITS2 sequences showed a somewhat different tree topology (Fig. 4A). At the species level, the ITS2 locus of Saga species appeared to be more conserved than the mitochondrial loci. Both the MP and Bayesian trees shared the same clades, but showed a slightly different tree topology. Both analyses positioned the Asian clades ‘ephippigera-ornata’ and ‘cappadocica’ at the basis of the tree, and confirmed the monophyly of European Saga lineage (natoliae, hellenica, rammei, and pedo-campbelli). The three Asian Saga species, S. cappadocica, S.ephippigera and S. ornata samples had a long (155 bp) insertion in their ITS2 sequence, compared to that of European species. Although this insert was removed before the above two trees were built, we have looked at their evolutionary relationship by generating a Neighbour-Joining tree (Fig. S2B). In agreement with the two above trees, the NJ tree has shown that S. ephippigera and S. ornata were more closely related to each other than to S. cappadocica.

Bottom Line: The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only.After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies.The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences and Biotechnology, Georgikon Faculty, University of Pannonia, Keszthely, Hungary.

ABSTRACT
Twelve of the 13 bushcricket species of the Saga genus are bisexuals and diploids, except the parthenogenetic and tetraploid bush cricket, Saga pedo. Despite a continuous research effort stretching through the 1900s, the taxonomic relationships of the Saga species are still disputed. In this study, our primary aim was to reveal natural relationships of the European Saga species and three of their Asian relatives, with special attention to the problematic taxonomy of two subspecies: S. campbelli campbelli and S. c. gracilis. Following a phylogenetic analysis of eight species, a comprehensive study was carried out on the above three taxa by using acoustic and morphometric approaches in parallel. Our phylogenetic data showed that European Saga species evolved from a monophyletic lineage. The geographical transitional species S. cappadocica was positioned between European and Asian lineages supporting the idea that the European Saga lineage originated phylogeographically from the Asian clade. The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only. After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies. S. c. gracilis shares the same ITS2 haplotype with S. pedo, indicating that the latter could have evolved from populations of the former, probably through whole genome duplication. Based on acoustic and morphometric differences, we propose to elevate the two subspecies, S. campbelli campbelli and S. c. gracilis, to species level status, as Saga gracilis Kis 1962, and Saga campbelli Uvarov 1921. The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.

Show MeSH