Unveiling the Mainland vs. Insular Variability of the Eumerus barbarus Species Group (Diptera: Syrphidae) in the Western Mediterranean Basin

Abstract

Comprising nearly 300 described species, Eumerus Meigen, 1822, is one of the most speciose syrphid genera worldwide, and its taxonomic diversity is remarkable in the Mediterranean basin. The Eumerus barbarus (Coquebert, 1804) group consists of four species in the western Mediterranean. Although the phenotypic variability of this species group has been commented on in previous studies, it has never been contrasted with molecular data. In the present work, the morphological variation found in 300+ specimens of this species group from the western Mediterranean is explored and tested against the COI mitochondrial DNA (mtDNA). The highest phenotypic disparity was found in E. barbarus and Eumerus sulcitibius Rondani 1868. The integrative approach has not revealed cryptic diversity within the species E. barbarus but in E. sulcitibius. As a result, a new species close to E. sulcitibius was discovered, Eumerus sardus Aguado-Aranda, Ricarte & Hauser sp. n., from Sardinia, Italy. The new insular species is here described, illustrated, and discussed. A total of twenty-three haplotypes of COI mtDNA were identified amongst the analyzed Mediterranean specimens of E. barbarus, whereas two and five haplotypes were distinguished in the Iberian specimens of E. sulcitibius and Eumerus gibbosus van Steenis, Hauser & van Zuijen, 2017, respectively. Moreover, the first known barcodes of E. gibbosus and Eumerus schmideggeri van Steenis, Hauser & van Zuijen, 2017 were obtained, and the distribution ranges of all species are mapped. An updated dichotomous key to the males of the E. barbarus group from the western Mediterranean is provided.

Keywords: Merodontini; barcode; genetic diversity; hoverflies; new species; phenotypic variation.

Figure 1

Eumerus barbarus, vertical triangle and scutum, pilosity (male): (a) mainly golden-yellow (but black on the ocellar triangle); (b) black on the vertical triangle anteriorly and intermixed on the scutum; (c) black on vertical triangle and intermixed on the scutum. Scale bar = 750 μm.

Figure 2

Eumerus barbarus, variation in the shape of the cercus of genitalia (male). An arrow indicates the triangular expansion. Scale bar = 250 μm.

Figure 3

Eumerus barbarus, scutum, pilosity (female): (a) short yellow hairs; (b) long yellow hairs; (c) black and yellow hairs intermixed. An arrow indicates the black hairs. Scale bar = 1 mm.

Figure 4

Eumerus barbarus, variation in the basoflagellomere coloration, male: (a) reddish orange, (b) blackish brown; female: (c) reddish orange, (d) blackish brown. Scale bar = 750 μm.

Figure 5

Maximum Likelihood tree based on COI-5′. We included only one sequence of each haplotype of E. sulcitibius from the eastern Mediterranean. DNA vouchers of specimens analyzed for this work are highlighted in bold. Bootstrap values >70 are shown near nodes. Branch lengths are measured in the number of substitutions per site.

Figure 6

Maximum Likelihood tree based on COI (COI-5′+COI-3′). DNA vouchers of specimens analyzed for this work are highlighted in bold. Bootstrap values > 70 are shown near nodes. Branch lengths are measured in the number of substitutions per site.

Figure 7

Haplotype network of E. barbarus from the western Mediterranean based on COI-5′ sequence data (see Supplementary Material S3). Size of circles is proportional to the number of individuals. Black dots depict the number of mutational steps. Three loops were removed in the network. Numbers of the haplotypes are indicated close to the circles.

Figure 8

Haplotype network of E. sulcitibius from the Mediterranean area based on COI-5′ sequence data (see Supplementary Material S3). Size of circles is proportional to the number of individuals. Black dots depict the number of mutational steps. Numbers of the haplotypes are indicated close to the circles.

Figure 9

Eumerus sardus sp. n., holotype (male), habitus: (a) dorsal view, (b) lateral view; head: (c) dorsal view, (d) lateral view. Scale bars = (a,b) 1 mm; (c,d) 750 μm.

Figure 10

Eumerus sardus sp. n., holotype (male), genitalia: (a) hypandrium, lateral view; (b) epandrium, lateral view. Eumerus sulcitibius, male, genitalia: (c) surstylus, lateral view. Legend: asl, anterior surstylar lobe; n, notch; pe, pointed expansion; psl, posterior surstylar lobe; te, triangular expansion. Scale bar = 250 μm.

Figure 11

Distribution range of E. sardus sp. n.

Figure 12

Distribution range of E. barbarus in the western Mediterranean basin. Magnifications: (a) Province of Alicante, (b) Mallorca, (c) Menorca. Red dots indicate new records, green dots indicate confirmed literature records, and blue dots indicate unconfirmed literature records.

Figure 13

Distribution range of E. sulcitibius in the Ibero-Balearic area. Red dots indicate new records, green dots indicate confirmed literature records, and blue dots indicate unconfirmed literature records.

Figure 14

Distribution range of E. gibbosus. Red dots indicate new records and yellow dots indicate literature records.

Figure 15

Distribution range of E. schmideggeri. Red dots indicate new records and yellow dots indicate literature records.