Morphological shape variation between and within <i>Colymbetes paykulli</i> males from the Palearctic (○) and Nearctic (■) regions.

<p>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 <i>C</i>. <i>paykulli</i> is within this study accepted as a valid species and should be known as <i>C</i>. <i>longulus</i> LeConte.</p

<i>Agabus bipustulatus</i> classification of secondary elytral reticulation after the total sample was screened for common patterns.

<p>Seven categories (A-G) ranging from tightly packed longitudinally elongated meshes to more or less isomorphic meshes were recognised in <i>Agabus bipustulatus</i>. Type A is found in the <i>bipustulatus</i> and <i>solieri</i> forms, type B in <i>kiesenwetterii</i>, <i>falcozi</i> and <i>dolomitanus</i>, and type C, F and G in <i>pyrenaeus</i>. The categories D, E and F describe intermixed patterns.</p

Distribution map of reported observations of the Holarctic (Δ) <i>Colymbetes dahuricus</i>, the Palearctic (●) <i>C</i>. <i>paykulli</i> and the Nearctic (■) <i>C</i>. <i>paykulli</i>.

<p>The latter is within this study accepted as a valid species. This means that the name of the Palearctic species is <i>C</i>. <i>paykulli</i> Erichson and the Nearctic species should be known as <i>C</i>. <i>longulus</i> LeConte.</p

Taxonomy of the <i>Colymbetes paykulli</i> -complex published after all five species names became available.

<p>Taxonomy of the <i>Colymbetes paykulli</i> -complex published after all five species names became available.</p

Maximum likelihood representation of sequence data from <i>Agabus bipustulatus</i> complex.

<p>Likelihood representation including all three genes (cytochrome b, cytochrome c oxidase subunit I and cytochrome oxidase II). The translational model (TIM) was used along with a proportion of invariable sites equal to 0.8199 and a gamma distribution shape parameter of 0.7877. The tree is rooted with the <i>Agabus bipustulatus</i> specimen from BipRus1 in order to visualise the deep split within the complex (group I and II). Jackknife values above 50% are reported above branches.</p

The evolutionary history of the <i>Colymbetes paykulli</i> complex was inferred by using the Maximum Likelihood method based on the Hasegawa-Kishino-Yano model with a discrete Gamma distribution (5 categories (+<i>G</i>, parameter = 0.3301)) and a invariable rate variation model ([+<i>I</i>], 58.5832% sites).

<p>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 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143577#pone.0143577.t002" target="_blank">table 2</a>. The Nearctic <i>C</i>. <i>paykulli</i> is within this study accepted as a valid species and should be known as <i>C</i>. <i>longulus</i> LeConte.</p

Species, country, sampling area, number of males and females, sampling code of specimen and collectors are listed.

<p>Collectors abbreviations as follows; N. Minakawa (NM), P. Oberg (PO), D.J. Larson (DL), J. Elmberg (JE), A. Töyrä (AT), K.B. Miller (KM), W. Hilsenhoff (WH), M.K. Drotz (MD), E. Goth-Birkigt (EGB), J. Bergsten (JB) and A.N. Nilsson (AN). Samples represent either a geographical area where specimens from several local sampling sites were pooled or a single sample locality. The Nearctic <i>C</i>. <i>paykulli</i> is within this study accepted as a valid species and should be known as <i>C</i>. <i>longulus</i> LeConte. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0143577#sec016" target="_blank">discussion</a> for more information.</p

tree from parsimony analysis of <i>Agabus bipustulatus</i> complex.

<p>The “best” fundamental tree, according to Kishino and Hasegawa test, from combined unweighted parsimony analysis of all three genes (cytochrome b, cytochrome c oxidase subunit I and cytochrome oxidase II), rooted with <i>Agabus bipustulatus</i> specimen from BipRus1 in order to visualise the deep split within the complex (group I and II), and to display unambiguous unique character state transformations, marked with (•), and homoplasious character state transformations with (○). Bootstrap values above 50% are reported above branches.</p