Lestes virens, (Charpentier, 1825) (Charpentier, 1825)

Simonsen, Thomas J., Djernaes, Marie, Nielsen, Ole Fogh & Olsen, Kent, 2023, COI diversity supports subspecific division in Western European Lestes virens (Charpentier, 1825) (Zygoptera: Lestidae), but hints at further Mediterranean complexity, International Journal of Odonatology 26, pp. 18-26 : 22-24

L. virens

specimens. There were 16 sequences available on BOLD and Genbank with at least 550 overlapping base pairs in the barcode region and a further five sequences with 318 overlapping base pairs. One sequence (Genbank accession number KF369424 ) did not have locality information and was therefore omitted. We constructed two different datasets: one dataset comprising the 43 sequences that were at least 550 base pairs long, and one that comprised all 48 sequences. The 43-sequence dataset was thus 550 base pairs long afer trimming, and the 48-sequence dataset was 318 base pairs long afer trimming. The 43-sequence dataset was used for haplotype network and phylogenetic analyses and assessment of genetic variation, while the 48-sequence dataset was only used for a haplotype network analysis. The sequence alignments used for the PopArt and MrBayes analyses are available as Supplementary Material in the Nexus format (Supplementary Material S1–S3).

The haplotype network analysis of the 43-sequence dataset ( Fig. 2 ) shows that L. virens can be divided into three well-defined haplotype groups in Western Europe that correspond well to the current geographic distribution and taxonomy. The specimens from southwestern Europe , all belonging to the current subspecies L. virens virens , form a well-delimited group (n = 10), defined by three unique nucleotide changes, with little internal variation. The specimens from northern and central Europe including mainland Italy, all belonging to the subspecies L. virens vestalis , form another well-delimited group (n = 30), defined by three unique nucleotide changes, albeit with greater internal variation. Interestingly, the single specimen from the Italian Mediterranean island of Sardinia is placed in this group. Finally , the three specimens from the Italian Mediterranean island of Sicily form a distinct and isolated group (n = 3), defined by five unique nucleotide changes, with no internal variation. The 48-sequence dataset with much shorter sequences confirms the division into three well-defined groups (Supplementary Figure S 4)—the five additional specimens, all from Bavaria in southern Germany, only add to the internal variation of L. virens vestalis .

The Bayesian analysis in MrBayes ( Fig. 3 ) confirms the results from the haplotype network analyses. Lestes virens virens , L. virens vestalis , and the specimens from Sicily all form distinct clades. But while the two latter clades are well supported with pp values of 99 and 96, respectively, L. virens virens only receives moderate support with a pp value of 84 despite appearing as a highly distinct group in the haplotype network—possibly because it shares homoplasious or plesiomorphic nucleotide changes with both the other groups. Interestingly, the specimens from Sicily form the sister group to a clade comprising L. virens virens and L. virens vestalis , although the latter is only poorly supported with a pp value of 63.

Genetic diversity

The K2P distance values ( Table 2 ) confirm the results from the haplotype network analyses. The average K2P distance between the groups varies from 0.0120 between L. virens virens and L. virens vestalis to 0.0173 between L. virens vestalis and the specimens from Sicily. The difference between L. virens virens and Sicily is 0.0163. The average K2P distance within groups varies between 0 in Sicilian specimens, 0.0004 in L. virens virens , and 0.0015 in L. virens vestalis . The average between groups K2P distance is thus approximately an order of magnitude higher than the highest within group K2P distance. The AMOVA-test ( Table 3 ) shows that more than 97% of the genetic variance is explained by variation among the three major groups. The overall nucleotide diversity (π) is 0.0072.

Figures

Figure 2. Minimum-spanning haplotype network based on the 550 bp COI dataset. The number of mutations between groups are indicated by bars. Groups are indicated as described in the text.

Figure 3. Tree from the 10 million generation analysis in MrBayes. Numbers indicate relevant posterior probability values. Groups are indicates as discussed in the text and colors correspond to Figure 1. For specimen details see Table 1.