Chalcolestes

Simonsen, Thomas J., Glahder, Marcus, Pape, Thomas, Olsen, Kent & Djernaes, Marie, 2022, Rhapsody in emerald: phylogenetic framework for Lestidae with reference to the systematic position of Chalcolestes Kennedy, International Journal of Odonatology 25, pp. 16-21 : 20

Position of Chalcolestes

Our results support recent conclusions by Dumont et al. (2010), Gyulavári et al. (2011), Dijkstra and Kalkman (2012), and Vajda et al. (2018) that Chalcolestes is a valid genus and should not be considered a synonym of Lestes . Gyulavári et al. (2011) analysed COI and ITS sequences from several specimens of C. viridis and C. parvidens , as well as Sympecma fusca and six taxa of European Lestes spp. in two separate analyses. In both analyses they found that Chalcolestes and Lestes are separated by Sympecma . However, as they did not analyse a combined dataset and only included European species, their results provide little information on the phylogenetic position of Chalcolestes . More importantly, their datasets did not include any non-Lestidae outgroup taxa and if the trees they presented ( Gyulavári et al., 2011, fig. 3) are rooted on Sympecma fusca (Vander Linden, 1820) , Chalcolestes and the included representatives of Lestes would appear to be sister groups. Even though Vajda et al. (2018) could not conclusively separate Chalcolestes , Lestes , and Sympecma in their statistical morphometric analyses of male morphology, they concluded that differences in the male secondary genitalia structures support full genus status for Chalcolestes . Furthermore, they mentioned that female genitalia morphology also supports this, as Chalcolestes viridis has two spermathecae, Sympecma fusca one spermatheca, and at least Lestes barberus (Fabricius, 1798) and Lestes virens have no spermatheca ( Vajda et al., 2018, p. 254). As mentioned above, Dumont et al. (2010) is the only higher-level phylogenetic study that includes Chalcolestes . Their results are similar to ours as Chalcolestes is the well-supported sister group to Indolestes . Our taxon sampling within Lestidae is broader than that of Dumont et al. (2010) as we include the genera Orolestes and Austrolestes . We find that Indolestes is placed in a strongly supported monophyletic group with Austrolestes , and that Chalcolestes is placed in a strongly supported monophyletic group with Orolestes . As these two groups together form a strongly supported monophyletic group (Group 1), our results are compatible with Dumont et al. (2010), and strongly support full genus status for Chalcolestes . Interestingly, Chalcolestes is entirely restricted to the Western and Central Palaearctic (Boudot & Duatlova, 2015; Boudot & Willigalla, 2015), while the other three genera are found in Southeast Asia ( Orolestes ), Australia ( Austrolestes ), or from India to Japan and Australia ( Indolestes ) (GBIF.org, 24 September 2021). As our dataset does not include the genera Platylestes ( India, Southeast Asia) and Sinhalestes ( Sri Lanka) (GBIF.org, 24 September 2021), we refrain from making any biogeographical conclusions but note that Chalcolestes may represent a dispersal into Central and Western Palaearctic by an otherwise Oriental-Australian group.

Conclusions and further directions

Three main conclusions can be drawn from our results despite the somewhat limited taxon sampling. First, there is no phylogenetic support for dividing Lestidae into the subfamilies Lestinae and Sympecmatinae. Second, Lestes as currently defined is almost certainly not a monophyletic group, and we agree with Dijkstra and Kalkman (2012) that a phylogenetic revision of the genus is much needed. Third, Chalcolestes is a valid genus that is not closely related to other European genera of Lestidae —neither Lestes nor Sympecma . Instead, the genus is most likely the sister group to Orolestes and placed in a clade with otherwise Oriental-Australian genera.

Other than the much-needed revision of Lestes sensu lato, several high profile aspects of Lestidae phylogeny and systematics remain to be solved. The relationship and delimitation of Austrolestes and Indolestes remain unclear, and the two genera in combination should be the subject of a phylogenetic taxonomic revision. The higher-level phylogeny of Lestidae should be the subject of phylogenomic analyses in the mould of Bybee et al. (2021) and include also Platylestes and Sinhalestes . Such a study should address the phylogenetic position of Sympecma , identify natural divisions that can be used for a subfamily and tribal classification, and resolve the biogeography of the family including the geographical origin of Chalcolestes .