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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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Morphological shape variation between and within Colymbetes paykulli males from the Palearctic (○) and Nearctic (■) regions.Shape variation was analysed with a Principle Component Analysis (PCA) of the partial warps, the uniform components and centroid size of the body in the Relative warps program v 1.20 (Rohlf 1998). The shape difference between the regions is significant (first component d.f. = 86, t-value = 13.30 p<0.001). 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.g002: Morphological shape variation between and within Colymbetes paykulli males from the Palearctic (○) and Nearctic (■) regions.Shape variation was analysed with a Principle Component Analysis (PCA) of the partial warps, the uniform components and centroid size of the body in the Relative warps program v 1.20 (Rohlf 1998). The shape difference between the regions is significant (first component d.f. = 86, t-value = 13.30 p<0.001). The Nearctic C. paykulli is within this study accepted as a valid species and should be known as C. longulus LeConte.

Mentions: The repeatability of the first five relative warps and centroid size ranges from 85.0 to 99.7% in the C. paykulli males and from 80.0 to 98.4% in females. This clearly indicates that the variation in form found here is due to true form variation and not measurement errors. The Nearctic C. paykulli males were more compact and had a wider abdominal apex than the Palearctic males, whereas the form variation was opposite in the females. We found a small morphological overlap in both sexes of this species-complex (Fig 2), but the difference in morph space was significant in both sexes (t-test of the first component: males (d.f. = 86, t-value = 13.30) P-value<0.001, and females (d.f. = 74, t-value = -5.67) P-value< 0.001). A larger morphological overlap between populations was seen in C. dahuricus males than in males of C. paykulli (T-test of first component (d.f. = 18, t-value = -5.01) p<0.001). As a result of too few C. dahuricus females to generate representative data they were subsequently excluded from the 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)

Morphological shape variation between and within Colymbetes paykulli males from the Palearctic (○) and Nearctic (■) regions.Shape variation was analysed with a Principle Component Analysis (PCA) of the partial warps, the uniform components and centroid size of the body in the Relative warps program v 1.20 (Rohlf 1998). The shape difference between the regions is significant (first component d.f. = 86, t-value = 13.30 p<0.001). 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.g002: Morphological shape variation between and within Colymbetes paykulli males from the Palearctic (○) and Nearctic (■) regions.Shape variation was analysed with a Principle Component Analysis (PCA) of the partial warps, the uniform components and centroid size of the body in the Relative warps program v 1.20 (Rohlf 1998). The shape difference between the regions is significant (first component d.f. = 86, t-value = 13.30 p<0.001). The Nearctic C. paykulli is within this study accepted as a valid species and should be known as C. longulus LeConte.
Mentions: The repeatability of the first five relative warps and centroid size ranges from 85.0 to 99.7% in the C. paykulli males and from 80.0 to 98.4% in females. This clearly indicates that the variation in form found here is due to true form variation and not measurement errors. The Nearctic C. paykulli males were more compact and had a wider abdominal apex than the Palearctic males, whereas the form variation was opposite in the females. We found a small morphological overlap in both sexes of this species-complex (Fig 2), but the difference in morph space was significant in both sexes (t-test of the first component: males (d.f. = 86, t-value = 13.30) P-value<0.001, and females (d.f. = 74, t-value = -5.67) P-value< 0.001). A larger morphological overlap between populations was seen in C. dahuricus males than in males of C. paykulli (T-test of first component (d.f. = 18, t-value = -5.01) p<0.001). As a result of too few C. dahuricus females to generate representative data they were subsequently excluded from the 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