Merodon natans (Fabricius, 1794)

Ačanski, Jelena, Tot, Tamara, Grković, Ana, Miličić, Marija, Radenković, Snežana & Vujić, Ante, 2023, An assessment of new character in hoverfly species delimitation using linear and geometric morphometrics - genus Merodon Meigen, 1803 (Diptera: Syrphidae) as a case study, European Journal of Taxonomy 910, pp. 98-114 : 105-107

Merodon natans group

Linear morphometrics

ANOVA did not find significant differences between the sexes (ANOVA: F 2,108 = 1.2; P> 0.05). However, highly significant differences between species were found (ANOVA: F 2,111 = 72.1; P <0.01). Merodon calcaratus (Fabricius, 1794) had a larger angle at the intersection of the R4+5 vein and the middle line, indicating that this species has a less sinuate R4+5 vein than other species of the natans group ( Fig. 3 ).

Geometric morphometrics analysis of R4+5 vein shape

Due to sexual dimorphism, analyses were performed separately on males and females (ANOVA: F 37, 234 = 5.348; P <0.01).

Regarding male specimens, DA clearly separated all species pairs based on R4+5 vein sinuation (P <0.01). 94.41% of all specimens were correctly classified into a priori defined groups. CVA produced two highly significant axes (CV1: Wilks’ Lambda = 0.0625; χ 2 = 338.211; P <0.01; CV2: Wilks’ Lambda = 0.282; χ 2 = 154.55; P <0.01). CV1, with 58% of the total shape variation, separated M. calcaratus from M. natans (Fabricius, 1794) and M. pulveris Vujić & Radenković, 2011 , whereas CV2, with 42%, separated M. natans from M. pulveris ( Fig 5A ). Superimposed outline drawings indicated that M. calcaratus has the least sinuate R4+5 vein ( Fig. 5D ).

Females of all species pairs differed highly significantly by R4+5 vein shape (DA: P <0.01). Overall, classification success was high, 98.50% of all female specimens were correctly classified based on vein sinuation. All females of M. calcaratus were correctly classified. CVA produced two highly significant axes (CV1: Wilks’ Lambda = 0.34; χ 2 = 378.52; P <0.01; CV2: Wilks’ Lambda = 0.208; χ 2 = 175.89; P <0.01). As in males, the first axis clearly separated M. calcaratus from M. natans and M. pulveris , whereas CV2, with 42% of the total shape variation, separated M. natans from M. pulveris ( Fig. 6A ). As in males, females of M. calcaratus had the least sinuate R4+5 vein ( Fig. 6 D ).

Combined geometric morphometrics analysis of R4+5 vein shape and wing shape

Due to sexual dimorphism, analyses were performed separately on males and females (ANOVA: F 60,211 = 7.93; P <0.01).

Males of all species pairs differed highly significantly using both semilandmarks and landmarks (DA: P <0.01). Classification success was excellent, only one specimen out of 143 was misclassified (one M. pulveris as M. natans ). CVA produced two highly significant axes (CV1: Wilks’ Lambda = 0.019; χ 2 = 505.313; P <0.01; CV2: Wilks’ Lambda = 0.199; χ 2 = 208.199; P <0.01). The first CV axis, with 69% of the total shape variation clearly separated M. natans from M. pulveris , whereas CV2, with the rest of the variability, clearly separated M. calcaratus from the other two species ( Fig. 5C ).

Females of all three species were correctly classified into a priori defined groups. All species pairs differed highly significantly (DA: P <0.01). CVA produced two highly significant axes (CV1: Wilks’ Lambda = 0.0046; χ 2 = 611.459; P <0.01; CV2: Wilks’ Lambda = 0.113; χ 2 = 247.88; P <0.01). Both CV axes clearly separated all species, the first CV1, with 75% of the total variation, separated M. natans from M. calcaratus , whereas CV2 separated M. pulveris from the other two species ( Fig. 6C ).

Figures

Fig. 3. Box plot showing a comparison of the angle at the intersection of the R4+5 vein and the middle line for all species used in the analysis.

Fig. 5. Results of the geometric morphometric wing shape analysis of males of the Merodon natans group. A. Scatter plot of individual scores showing the R4+5 vein shape variability. B. Scatter plot of individual scores showing the wing shape variability from Vujić et al. (2021c). C. Scatter plot of individual scores showing the semilandmark R4+5 vein shape and landmark wing shape variability D. Superimposed outline drawings showing R4+5 vein shape differences among males of the investigated species.

Fig. 6. Results of the geometric morphometric wing shape analysis of females of the Merodon natans group. A. Scatter plot of individual scores showing the R4+5 vein shape variability. B. Scatter plot of individual scores showing wing the shape variability from Vujić et al. (2021c). C. Scatter plot of individual scores showing the semilandmark R4+5 vein shape and landmark wing shape variability D. Superimposed outline drawings showing the R4+5 vein shape differences among females of the investigated species.