Hetaerina calverti Vega-Sánchez & Mendoza-Cuenca & Rodríguez 2020, sp. nov.

Hetaerina calverti sp. nov.

(Figs. 1–3)

Type specimens

Holotype. ♂ (CNIN), tributary stream of Los Pescados River in Apazapan, Veracruz, Mexico (19.3250389, -96.7248972, 305 m asl), 3 July 2019. L.F. Mendoza-Cuenca leg. The male was collected in tandem position with the female allotype (Fig. 1).

Allotype. ♀ (CNIN). A mature female that was collected in the same locality, date and collector as the holotype (Fig. 1).

Paratypes. 4 ♂♂ (CNIN and GCEUMSNH). A mature male, same locality and date as the holotype. Y.M. Vega-Sánchez leg. (Fig. 2), and three mature males from El Platanal, Xichú, Guanajuato, Mexico (21.465478, - 99.832283, 700 m asl), 5 April 2019. Y.M. Vega-Sánchez leg.

Etymology. This species was named in honor to Dr. Philip P. Carlvert because he was the first scientist to analyze and illustrate the shape of the cerci of the new species and for his prominent contribution to the odonatology of the Neotropics.

Description of holotype

Head. Metallic red.

Thorax. Prothorax mostly metallic red. Pterothorax mainly red, with metallic brown flashes; the sutures—hu-meral, interpleural and metapleural—are whitish. Mesepisternum completely metallic red except for white anterior humeral margin; mesepimeron mainly red-brown with metallic green flashes; metepisternum with an elongated metallic brown hook-shaped spot that invades the metepimeron at its superior margin and is surrounded by pale whitish coloration (Fig. 1). Metepimeron surrounded by pale whitish color and with an elongate reddish spot in the center. Legs dark brown.

Wings. All wings with a red spot at the base, extending up to four crossveins beyond the quadrangle. All veins on HW spot white below. All wings lacking apical spots. Pterostigma present in all wings, dark brown.

Abdomen. Metallic green on dorsum becoming metallic brown from S7–10. S1 with pale spots on sides.

Caudal appendages. Cerci yellowish with the median lobe widened and flattened at the beginning and with a prominent tooth at the end. The transverse ridge connects at 45° with the superior ridge, which is beyond three fourths of the length of the cercus. Paraprocts cylindrical and one third the length of the cerci, with a pair of spines at the tip; yellowish at the base, the distal part dark brown (Fig. 3).

Measurements. Total length 47; abdomen 37.5; HW 25.7; FW 27.1.

Variation in male paratypes

The male paratype deposited at CNIN has pale brown humeral, interpleural and metapleural sutures (Fig. 3). In the paratypes deposited at GCEUMSNH, the red spot at the base extends up to two crossveins beyond the quadrangle.

Measurements. Total length 39.65–45.9 (41.69); abdomen 31.76–36.7 (33.56); HW 23.79–25.1 (24.18); FW 26–27 (26.3).

Description of allotype

Head. Frons mainly metallic reddish with green flashes. Postclypeus metallic red in the center, margins white. Labrum mainly whitish. First segment of antennas white, remainder black (Fig. 1).

Thorax. Prothorax metallic brown-green; intersternites linear, without anterior shoulder. Pterothorax mainly metallic brown-green with whitish humeral, interpleural and metapleural sutures. Mesepisternum completely metallic brown-green except for white humeral margin; mesepimeron mainly metallic brown-green, metepisternum surrounded by whitish color, with an elongated metallic brown hook-shaped spot that invades the metepimeron at its superior margin (Fig. 1). Metepimeron with an elongated brown spot in the center, surrounded by whitish coloration. Coaxes pale yellowish, rest of legs dark brown.

Wings. All wings with an amber spot that lightens towards the apex. Veins on HW spot white. All wings lacking apical spots. Pterostigma present in all wings, white.

Abdomen. Each segment metallic green above, except the last three segments metallic brown, in addition, all segments with a thin pale medio-dorsal line. Ventral part of the abdomen pale. Medio-dorsal carina of S10 ends in a prominent spine that extends beyond the rest of the segment (Fig. 1 and 3).

Measurements. Total length 36.3; abdomen 28.1; HW 24.5; FW 26.1.

Diagnosis

The male of H. calverti is distinguished from other species of the genus by the shape of the cerci. The median lobe extends from one third to beyond two thirds of the appendage and is widened and flattened in the middle part and ends in an acute projection. In contrast, the median lobe in H. americana is more bilobed (Fig. 3).

Additionally, in the distal part of the cerci, after the transverse ridge the distal fossa is short and represents a quarter or less of the total length of the appendage. This is the principal difference with H. americana, in which the distal fossa is larger and represents more than a quarter of the cercus (Fig. 3).

The female of H. calverti is characterized by having a linear intersternite. The medio-dorsal carina of S10 forms a prominent spine that extends beyond the margin of the segment. In H. americana, the intersternite presents an anterior shoulder and the medio-dorsal carina of S10 forms a spine but no as prominent as in H. calverti (Fig. 4).

3.3. Distribution, ecology and variation in size

Based on 1071 specimens reviewed in both collections (CNIN and GCEUMSNH), we found 621 individuals with georeferenced information (principally males), of which 457 belong to H. americana and 164 to H. calverti (Supplementary table 1).

Hetaerina calverti is found from Guatemala to northern Mexico (Fig. 5). It is distributed in shallow streams and small rivers in tropical dry forests principally, but in the northern part of its distribution it can be found in desert shrub and grass vegetation types. It is usually in sympatry with H. americana (Fig. 4). Like other species of Hetaerina, the males are territorial and perform synchronized flights. The females are usually far from the territories of the males and only approach these in order to copulate. After copulation, the tandem pair leaves the territory of the male to look for oviposition sites.

On the other hand, we found differences in the total length between species when they are in sympatry (Species: F= 54.8; p-value<0.0001; Locality type: F= 1.15; p-value= 0.28; Interaction: F= 8.76; p-value= 0.003), being H. calverti larger. Differentiation in HW was somewhat less pronounced (Species: F= 12.95; p-value = 0.0003; Locality type: F= 0.15; Interaction: F= 3.29; p-value = 0.07).

3.4. Genetic distances

Nuclear DNA (ITS region) data show a 5% divergence between H. calverti and H. americana. Therefore, H. calverti can be distinguished without hesitation by using this region of the nuclear genome. The distances between other species of the genus range from 2% to 12% (Table 2).