Are Appearances Deceiving? Morpho-Genetic Complexity of the Eumerus tricolor Group (Diptera: Syrphidae) in Europe, with a Focus on the Iberian Peninsula

Abstract

Eumerus Meigen, 1822 is one of the largest Syrphidae genera in the Palaearctic Region, with the highest levels of taxonomic diversity found in the Eumerus tricolor species group. Despite its high diversity, the interspecific levels of morphological variability can be low. Additionally, some species may show certain levels of intraspecific variability. Hence, species delimitation may become challenging. In this work, we assessed the diversity of the E. tricolor group in the Iberian Peninsula through an integrative analysis of nomenclature, morphology and the 5' (COI-5') and 3' (COI-3') end regions of the Cytochrome c oxidase subunit I gene. Two new species, Eumerus ancylostylus Aguado-Aranda & Ricarte sp. n. and Eumerus petrarum Aguado-Aranda, Nedeljković & Ricarte sp. n., were described, and their intra- and interspecific variations discussed. In addition, the first barcodes of Iberian members of the E. tricolor group were obtained, and the distribution ranges of all species were mapped within the study area. The systematic position of the new species is discussed based on the resulting COI-based trees. The male genitalia of Eumerus hispanicus van der Goot, 1966 and Eumerus bayardi Séguy, 1961 were studied and illustrated. A lectotype was designated for Eumerus lateralis (Zetterstedt, 1819). An updated dichotomous key for all known European species of the E. tricolor group is provided. The egg of E. petrarum sp. n. is also described.

Keywords: COI; Merodontini; hoverfly; male genitalia; phenotypic diversity; systematics.

Figure 1

Maximum Likelihood tree based on COI-5′. DNA vouchers of specimens analyzed for this work are highlighted in bold. Bootstrap values > 50 are shown near nodes. Branch lengths are measured in the number of substitutions per site.

Figure 2

Neighbor-Joining tree based on COI (COI-5′+COI-3′). DNA vouchers of specimens analyzed for this work are highlighted in bold. Bootstrap values > 50 are shown near nodes. Branch lengths are measured in the number of substitutions per site.

Figure 3

Eumerus ancylostylus sp. n., male (holotype): (A) Habitus, lateral view. (B) Habitus, dorsal view. (C) Head, lateral view. (D) Eye contiguity (indicated by an arrow). Scale bars = (A) 1 mm; (B) 2 mm; (C,D) 500 µm.

Figure 4

Male, vertical triangle: (A) E. ancylostylus sp. n. (holotype). (B) E. grandis (specimen from Montenegro). (C) E. lateralis (lectotype). Vertical triangle width (mm): a = 0.58, b = 0.43, c = 0.5. Scale bar = 500 µm.

Figure 5

Eumerus ancylostylus sp. n. (holotype), male genitalia: (A) Hypandrium, ventral view. (B) Hypandrium, lateral view (right side). (C) Epandrium, lateral view (right side). Legend: de, dentate expansion; psl, posterior surstylar lobe; rb, rounded bulges. Scale bar = 250 µm.

Figure 6

Surstylus, lateral view (right side): (A) E. ancylostylus sp. n. (holotype). (B) E. grandis (specimen from Montenegro). (C) E. lateralis (lectotype). Male genitalia, lateral view (right side): (D) E. ancylostylus sp. n. (E) E. grandis. (F) E. lateralis. An arrow indicates the posterior surstylar lobe, which is enlarged in the images above. Scale bar (D–F) = 250 µm.

Figure 9

Eumerus petrarum sp. n., male (holotype), habitus: (A) Lateral view. (B) Dorsal view. Female (paratype), habitus: (C) Lateral view. (D) Dorsal view. Scale bars = (A–C) 1 mm; (D) 2 mm.

Figure 10

Eumerus petrarum sp. n., head: (A) Male (holotype). (B) Female (paratype). Head, lateral view: (C) Male. (D) Female. Head, dorsal view: (E) Male. (F) Female. Scale bar = 500 µm.

Figure 11

Eumerus petrarum sp. n., male genitalia (holotype): (A) Hypandrium, lateral view (right side). (B) Epandrium, lateral view (right side). (C) Surstylus, intraspecific variation. (D) Epandrium, ventral view. Legend: ial, interior accessory lobe. Scale bars = (A,D) 250 µm; (B,C) 100 µm.

Figure 12

Eumerus petrarum sp. n., egg: (A) Detail of the chorionic sculpture. (B) Units conforming to the chorionic sculpture. Units may touch each other in some parts because the egg was not uniformly turgid. Legend: col, columns.

Figure 7

Distribution ranges of the Iberian members of the E. tricolor species group. Confirmed records are indicated with a square. Unconfirmed published records are indicated with a triangle.

Figure 8

Eumerus lateralis, male (lectotype): (A) Habitus, lateral view. (B) Head, lateral view. (C) Original labels. Female (paralectotype): (D) Habitus, lateral view. (E) Head, lateral view. (F) Original labels. Scale bars = (A,D) 1 mm; (B,E) 500 µm.

Figure 13

Eumerus sabulonum, male genitalia: (A) Hypandrium, lateral view (right side). (B) Epandrium, lateral view (right side). (C) Surstylus, intraspecific variation. (D) Epandrium, ventral view. Legend: ial, interior accessory lobe. Scale bars = (A,B,D) 250 µm; (C) 100 µm.

Figure 14

Eumerus litoralis, male (syntype), habitus: (A) Lateral view. (B) Dorsal view. Photos by Simon Hinkley (MMV).

Figure 15

Mesonotum, pilosity (male): (A) E. azabense. (B) E. tricolor. Scale bars = (A) 750 µm; (B) 500 µm.

Figure 16

Basoflagellomere, female: (A) E. ovatus. (B) E. azabense. Scale bars = 500 µm.

Figure 17

Eumerus bayardi, male: (A) Habitus, lateral view. (B) Habitus, dorsal view. (C) Head. (D) Metafemur. Scale bars = (A) 1 mm; (B) 2 mm; (C,D) 500 µm.

Figure 18

Eumerus bayardi, male, genitalia: (A) Hypandrium, lateral view (right side). (B) Epandrium, lateral view (right side). (C) Epandrium, ventral view. Legend: se, serrated expansion; vb, ventral bulge. Scale bars = (A,B) 250 µm; (C) 100 µm.

Figure 19

Eumerus hispanicus, male (paratype): (A) Habitus, lateral view. (B) Habitus, dorsal view. (C) Head. (D) Original labels. Scale bars = (A,B) 1 mm; (C) 500 µm.

Figure 20

Eumerus hispanicus, male genitalia (mainly based on the paratype), hypandrium: (A) Ventral view. (B) Lateral view (right side). Epandrium: (C) Lateral view (right side). (D) Ventral view. Legend: dte, dorsal triangular expansion; vb, ventral bulge; vhe, ventral hyaline expansions. Scale bars = 250 µm.

Figure 21

Eumerus sabulonum, head, lateral view: (A) Male. (B) Female. An arrow indicates the orange macula. Scale bars = (A) 250 µm; (B) 500 µm.