Sampling localities of <i>Culex pipiens</i> across Germany with significant different population pairwise F_ST values.

<p>Significant different pairwise F_ST values between populations are indicated using different line colors. Significant F_ST values were grouped into the four following categories: very great population differentiation (red lines), great population differentiation (yellow lines), moderate population differentiation (green lines) and low population differentiation (purple lines) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone.0102158-Balloux1" target="_blank">[67]</a>. Pictured are all sampling points listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone-0102158-t004" target="_blank">Table 4</a> with a summary of their haplotypes. Map was created with ArcMap 10.1.</p

Sampling localities in Germany with abbreviations and number of sequences and detected haplotypes at each locality.

<p>Sampling localities in Germany with abbreviations and number of sequences and detected haplotypes at each locality.</p

Population Structure and Distribution Patterns of the Sibling Mosquito Species <i>Culex pipiens</i> and <i>Culex torrentium</i> (Diptera: Culicidae) Reveal Different Evolutionary Paths

<div><p>Nowadays a number of endemic mosquito species are known to possess vector abilities for various diseases, as e.g. the sibling species <i>Culex pipiens</i> and <i>Culex torrentium</i>. Due to their morphological similarity, ecology, distribution and vector abilities, knowledge about these species' population structure is essential. Culicidae from 25 different sampling sites were collected from March till October 2012. All analyses were performed with aligned cox1 sequences with a total length of 658 bp. Population structure as well as distribution patterns of both species were analysed using molecular methods and different statistical tests like distance based redundancy analysis (dbDRA), analysis of molecular variances (AMOVA) or McDonald & Kreitman test and Tajima's D. Within both species, we could show a genetic variability among the cox1 fragment. The construction of haplotype networks revealed one dominating haplotype for <i>Cx. pipiens</i>, widely distributed within Germany and a more homogeneous pattern for <i>Cx. torrentium</i>. The low genetic differences within <i>Cx. pipiens</i> could be a result of an infection with <i>Wolbachia</i> which can induce a sweep through populations by passively taking the also maternally inherited mtDNA through the population, thereby reducing the mitochondrial diversity as an outcome of reproductive incompatibility. Pairwise population genetic differentiation (F_ST) ranged significantly from moderate to very great between populations of <i>Cx. pipiens</i> and <i>Cx. torrentium</i>. Analyses of molecular variances revealed for both species that the main genetic variability exists within the populations (<i>Cx. pipiens</i> [88.38%]; <i>Cx. torrentium</i> [66.54%]). Based on a distance based redundancy analysis geographical origin explained a small but significant part of the species' genetic variation. Overall, the results confirm that <i>Cx. pipiens</i> and <i>Cx. torrentium</i> underlie different factors regarding their mitochondrial differentiation, which could be a result of endosymbiosis, dispersal between nearly located populations or human introduction.</p></div

Sampling localities of <i>Culex torrentium</i> across Germany with significant different population pairwise F_ST values.

<p>Significant F_ST values were grouped into the four following categories: very great population differentiation (red lines), great population differentiation (yellow lines), moderate population differentiation (green lines) and low population differentiation (purple lines) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone.0102158-Balloux1" target="_blank">[67]</a>. Pictured are all sampling points listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone-0102158-t005" target="_blank">Table 5</a> with a summary of their haplotypes. There were no significant moderate or low F_ST values. Map was created with ArcMap 10.1.</p

AMOVA group structure of <i>Culex pipiens</i> and <i>Culex torrentium</i>.

<p>Group structures are based on pairwise F_ST's of <i>Culex pipiens</i> and <i>Culex torrentium</i>.</p

Haplotype networks of <i>Culex pipiens</i> and <i>Culex torrentium</i> for the cox1 gene segment calculated using statistical parsimony as implemented in TCS 1.21.

<p>The squares stand for the most probable ancestral haplotypes, the circle for all other haplotypes. The Numbers are equal to the haplotypes of each species. Each line represents a single mutation while small white dots symbolize hypothetical missing haplotypes. The size of the circles and the square is proportional to the number of the occurring haplotypes. The number of individuals can be derived from the scale which is given in the figure. Different colors represent the different geographical sampling localities. The colored area is proportional to the occurrence at the respective site.</p

Distribution of <i>Culex torrentium</i> (white) and <i>Culex pipiens</i> (grey) in Germany (A) and the Hessian Rhine-Main area (B).

<p>Small circles in Figure 1A (excluding the circles for FFM, BV, AS and GR) indicate that only one of the two species was detected at this specific locality. Pie charts indicate the ratio of the two detected species at this locality. The sizes of the pie chart and the circles do not relate to the number of investigated individuals (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone-0102158-t001" target="_blank">Table 1</a>). A: Overview of the sampling localities across Germany. Abbreviations: AS = Altenstadt, BV = Bad Vilbel, MF = Berlin-Marienfelde, BI = Bielefeld, BL = Bad Lippspringe, DB = Duisburg, DK = Dresden-Klotzsche, EW = Eberswalde, FFM = Frankfurt/Main (four different localities: Bornheim (FB), Bockenheim (KS), Sachsenhausen (FS) and Ostend (FZ)), FT = Fuldatal, GR = Gründau-Rothenbergen, HU = Husum, KL = Klein Linden, LE = Lebus, LL = Langenlehsten, MG = Mönchengladbach, MÜ = Müncheberg, RI = Rietschen, ST = Stralsund and WI = Wismar. B: Detailed view of the Rhine-Main area with Höchst a.d.N. (A1), Eichen (AS2), Heldenbergen (AS3), Klein Linden. Map was created with ArcMap 10.1.</p

Population pairwise F_ST from <i>Culex torrentium</i> calculated with Arlequin 3.5.1.2.

<p>Data based on the analyses of 193 sequences of the cox1 gene segment from 10 different sampling localities in Germany (FFM = Frankfurt/Main with KS, FB and FZ). Sample size are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone-0102158-t001" target="_blank">Table 1</a>, abbreviations of each locality are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone-0102158-t001" target="_blank">Table 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone-0102158-t003" target="_blank">3</a>. Significant different F_ST values are shown in bold. For calculation only populations with 5 or more individuals were used.</p

Results of the Analysis of molecular variance (AMOVA) and level of genetic differentiation of <i>Culex pipiens</i> and <i>Culex torrentium</i> measured by F_CT, F_SC, and F_ST.

<p>All Data were calculated in Arlequin 3.5.1.2 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone.0102158-Excoffier2" target="_blank">[59]</a> based on the distance method of Tamura and Nei <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102158#pone.0102158-Tamura3" target="_blank">[60]</a>.</p