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Changing Names with Changed Address: Integrated Taxonomy and Species Delimitation in the Holarctic Colymbetes paykulli Group (Coleoptera: Dytiscidae).

Drotz MK, Brodin T, Nilsson AN - PLoS ONE (2015)

Bottom Line: Only a few sampled specimens occur from this particular area and they are mostly found in museum and private collections.However, significant difference in size and reticulation patterns from the two regions is shown.The combined conclusion is that the C. dahuricus complex needs a more thorough investigation to fully disentangle its taxonomic status.

View Article: PubMed Central - PubMed

Affiliation: Lake Vänern Museum of Natural and Cultural History, Lidköping, Västra Götaland, Sweden.

ABSTRACT
Species delimitation of geographically isolated forms is a long-standing problem in less studied insect groups. Often taxonomic decisions are based directly on morphologic variation, and lack a discussion regarding sample size and the efficiency of migration barriers or dispersal/migration capacity of the studied species. These problems are here exemplified in a water beetle complex from the Bering Sea region that separates North America from Eurasia. Only a few sampled specimens occur from this particular area and they are mostly found in museum and private collections. Here we utilize the theory of integrated taxonomy to discuss the speciation of the Holarctic Colymbetes paykulli water beetle complex, which historically has included up to five species of which today only two are recognized. Three delimitation methods are used; landmark based morphometry of body shape, variation in reticulation patterns of the pronotum exo-skeleton and sequence variation of the partial mitochondrial gene Cyt b. Our conclusion is that the Palearctic and Nearctic populations of C. paykulli are given the status of separate species, based on the fact that all methods showed significant separation between populations. As a consequence the name of the Palearctic species is C. paykulli Erichson and the Nearctic species should be known as C. longulus LeConte. There is no clear support for delineation between Palearctic and Nearctic populations of C. dahuricus based on mtDNA. However, significant difference in size and reticulation patterns from the two regions is shown. The combined conclusion is that the C. dahuricus complex needs a more thorough investigation to fully disentangle its taxonomic status. Therefore it is here still regarded as a Holarctic species. This study highlights the importance to study several diagnosable characters that has the potential to discriminate evolutionary lineage during speciation.

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The evolutionary history of the Colymbetes paykulli complex was inferred by using the Maximum Likelihood method based on the Hasegawa-Kishino-Yano model with a discrete Gamma distribution (5 categories (+G, parameter = 0.3301)) and a invariable rate variation model ([+I], 58.5832% sites).The tree with the highest log likelihood (-1493.9031) is shown. Bootstrap values above 60% are reported below branches. Above branches are the Maximum likelihood partition support values from the Poisson tree processes (PTP) model given for each species identified by the model. Sequence reference to individual sample from population follow table 2. The Nearctic C. paykulli is within this study accepted as a valid species and should be known as C. longulus LeConte.
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pone.0143577.g003: The evolutionary history of the Colymbetes paykulli complex was inferred by using the Maximum Likelihood method based on the Hasegawa-Kishino-Yano model with a discrete Gamma distribution (5 categories (+G, parameter = 0.3301)) and a invariable rate variation model ([+I], 58.5832% sites).The tree with the highest log likelihood (-1493.9031) is shown. Bootstrap values above 60% are reported below branches. Above branches are the Maximum likelihood partition support values from the Poisson tree processes (PTP) model given for each species identified by the model. Sequence reference to individual sample from population follow table 2. The Nearctic C. paykulli is within this study accepted as a valid species and should be known as C. longulus LeConte.

Mentions: The Maximum Likelihood method based on the HKY+G+I model resulted in a tree with the highest log likelihood -1493.9031. Bootstrap values above 60% are reported below braches (Fig 3). Gamma distribution (+G) was estimated to 0.3301. The invariable rate value (+I) was estimated to be 58.5832% per site. Parsimony analysis did not support that the data was subjected to ‘long branch attraction’. The analysis resulted in four most parsimonious (MP) trees with a length of 204 steps (uninformative characters excluded), and CI and RI of 0.54 and 0.79, respectively (tree not shown). The subsequent phylogenetic analysis without the out-group species Rhantus grapii resulted in two MP un-rooted trees with a tree length of 181 steps, CI and RI of 0.59 and 0.81, respectively (tree not shown). The main differences between these six fundamental trees from the two analyses were the position of the clade including Colymbetes fuscus and C. schildknechti and the clade including the C. exaratus haplotype and the Swedish C. striatus. The topology of the clade including all the paykulli-group specimens was identical in the two analyses. When the outgroup species was excluded, the resulting topologies were identical to two of the four most parsimonious trees in the complete analysis.


Changing Names with Changed Address: Integrated Taxonomy and Species Delimitation in the Holarctic Colymbetes paykulli Group (Coleoptera: Dytiscidae).

Drotz MK, Brodin T, Nilsson AN - PLoS ONE (2015)

The evolutionary history of the Colymbetes paykulli complex was inferred by using the Maximum Likelihood method based on the Hasegawa-Kishino-Yano model with a discrete Gamma distribution (5 categories (+G, parameter = 0.3301)) and a invariable rate variation model ([+I], 58.5832% sites).The tree with the highest log likelihood (-1493.9031) is shown. Bootstrap values above 60% are reported below branches. Above branches are the Maximum likelihood partition support values from the Poisson tree processes (PTP) model given for each species identified by the model. Sequence reference to individual sample from population follow table 2. The Nearctic C. paykulli is within this study accepted as a valid species and should be known as C. longulus LeConte.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664258&req=5

pone.0143577.g003: The evolutionary history of the Colymbetes paykulli complex was inferred by using the Maximum Likelihood method based on the Hasegawa-Kishino-Yano model with a discrete Gamma distribution (5 categories (+G, parameter = 0.3301)) and a invariable rate variation model ([+I], 58.5832% sites).The tree with the highest log likelihood (-1493.9031) is shown. Bootstrap values above 60% are reported below branches. Above branches are the Maximum likelihood partition support values from the Poisson tree processes (PTP) model given for each species identified by the model. Sequence reference to individual sample from population follow table 2. The Nearctic C. paykulli is within this study accepted as a valid species and should be known as C. longulus LeConte.
Mentions: The Maximum Likelihood method based on the HKY+G+I model resulted in a tree with the highest log likelihood -1493.9031. Bootstrap values above 60% are reported below braches (Fig 3). Gamma distribution (+G) was estimated to 0.3301. The invariable rate value (+I) was estimated to be 58.5832% per site. Parsimony analysis did not support that the data was subjected to ‘long branch attraction’. The analysis resulted in four most parsimonious (MP) trees with a length of 204 steps (uninformative characters excluded), and CI and RI of 0.54 and 0.79, respectively (tree not shown). The subsequent phylogenetic analysis without the out-group species Rhantus grapii resulted in two MP un-rooted trees with a tree length of 181 steps, CI and RI of 0.59 and 0.81, respectively (tree not shown). The main differences between these six fundamental trees from the two analyses were the position of the clade including Colymbetes fuscus and C. schildknechti and the clade including the C. exaratus haplotype and the Swedish C. striatus. The topology of the clade including all the paykulli-group specimens was identical in the two analyses. When the outgroup species was excluded, the resulting topologies were identical to two of the four most parsimonious trees in the complete analysis.

Bottom Line: Only a few sampled specimens occur from this particular area and they are mostly found in museum and private collections.However, significant difference in size and reticulation patterns from the two regions is shown.The combined conclusion is that the C. dahuricus complex needs a more thorough investigation to fully disentangle its taxonomic status.

View Article: PubMed Central - PubMed

Affiliation: Lake Vänern Museum of Natural and Cultural History, Lidköping, Västra Götaland, Sweden.

ABSTRACT
Species delimitation of geographically isolated forms is a long-standing problem in less studied insect groups. Often taxonomic decisions are based directly on morphologic variation, and lack a discussion regarding sample size and the efficiency of migration barriers or dispersal/migration capacity of the studied species. These problems are here exemplified in a water beetle complex from the Bering Sea region that separates North America from Eurasia. Only a few sampled specimens occur from this particular area and they are mostly found in museum and private collections. Here we utilize the theory of integrated taxonomy to discuss the speciation of the Holarctic Colymbetes paykulli water beetle complex, which historically has included up to five species of which today only two are recognized. Three delimitation methods are used; landmark based morphometry of body shape, variation in reticulation patterns of the pronotum exo-skeleton and sequence variation of the partial mitochondrial gene Cyt b. Our conclusion is that the Palearctic and Nearctic populations of C. paykulli are given the status of separate species, based on the fact that all methods showed significant separation between populations. As a consequence the name of the Palearctic species is C. paykulli Erichson and the Nearctic species should be known as C. longulus LeConte. There is no clear support for delineation between Palearctic and Nearctic populations of C. dahuricus based on mtDNA. However, significant difference in size and reticulation patterns from the two regions is shown. The combined conclusion is that the C. dahuricus complex needs a more thorough investigation to fully disentangle its taxonomic status. Therefore it is here still regarded as a Holarctic species. This study highlights the importance to study several diagnosable characters that has the potential to discriminate evolutionary lineage during speciation.

Show MeSH
Related in: MedlinePlus