Heteragrion denisye

Vilela, Diogo Silva, Koroiva, Ricardo & Guillermo-Ferreira, Rhainer, 2019, Heteragrion denisye sp. nov. (Odonata: Zygoptera: Heteragrionidae), a notable species from Serra da Canastra, Minas Gerais, Brazil, Zootaxa 4671 (4), pp. 589-594: 590-592

publication ID

https://doi.org/10.11646/zootaxa.4671.4.10

publication LSID

lsid:zoobank.org:pub:CC043DC1-AD6B-4AA7-8888-5BE1E66D4D28

persistent identifier

http://treatment.plazi.org/id/03B5716E-7801-FF84-FF77-38E856B1FE27

treatment provided by

Plazi

scientific name

Heteragrion denisye
status

sp. nov.

Heteragrion denisye  sp. nov.

( Figs. 2a, c, dView FIGURE 2; 3View FIGURE 3 and 4 aView FIGURE 4 ̅e)

Holotype. ³( LESTES, RK054), BRAZIL, Minas Gerais, São Roque de Minas, Serra da Canastra National Park (-20.2323, -46.6085, 1305 m asl), 25 x 2018, Diogo S. Vilela, Ricardo Koroiva, Vanessa Nobrega & Marcellus Lera leg.GoogleMaps 

Etymology. Named denisye  (noun in genitive case) after Denisy Aparecida Silva, teacher, educator and beloved mother of the first author.

Description of holotype / Head. Labium light grey; labrum black; base of mandibles and genae black; remain- der of the head black, except for lighter spots lateral to each lateral ocellus and pale postocular lobes ( Fig. 2cView FIGURE 2). Posterior head pale, with dark markings laterally.

Thorax. Prothorax black dorsally; anterior lobe blue/grey laterally; middle lobe mostly blue laterally except for a small pale spot posteriorly; posterior lobe entirely black, bent caudad. Pterothorax black, with thin blue/pale stripes along the main thoracic sutures (mesopleural, metapleural and interpleural); remainder of thorax blue/grey. Legs; coxae pale grey, black medially; all femora and pro-, meso tibiae black externally, brown internally, metatibiae brown; spines longer than the space between them, becoming longer towards the apex on femora, and shorter towards the apex on tibiae; metatarsi missing ( Fig. 2a, dView FIGURE 2).

Wings. Hyaline, almost reaching S8; venation brown; pterostigma dark brown overlying 2 FW to 2 1/2 HW cells, oblique proximally; two postquadragular cells in FW and HW, 18 Px in FW, 16 HW ( Fig. 3View FIGURE 3).

Abdomen. Black, with pale basal rings from S3 to S7; S1 black dorsally, pale blue laterally; S2 with a pale area on its lower portion; ventroposterior portion of S8 and entire ventral portion of S9–S10 pale yellow.

Anal appendages. Black with dark brown coloration medially; ventrobasal expansion present, occupying at least 1/3 of the appendage; basal (BP) and medial portion (MP) subequal; medial portion dilated, almost rectangular, ventral branch of medial process plate-like with a bilobate apex and a distinct (almost straight) ridge; apical portion (AP) the shortest, ending with a beak-like blunt tip curved inwards ( Fig. 4View FIGURE 4 a–e). Paraprocts greatly reduced.

Measurements (in mm). FW: 24.5; HW: 23.4; Abdomen: 28.8; Total: 36.5.

Differential diagnosis. Heteragrion denisye  belongs to Lencioni’s Group A, consisting of males lacking an elongated paraproct. It is a remarkable new species mainly due to its blue coloration pattern and cerci morphology. The cerci of H. denisye  are easily distinguished from other congeners by the reduced apical portion, the latter elongated in most of Brazilian Heteragrion  species, including those of Group A (see Lencioni 2013 for a review of Heteragrion  Group A). In Heteragrion  , the apical portion of cerci is rarely shorter than the basal and medial portions. In Group A, H. denisye  shares the short apical portion with H. johndeaconi  and H. gracile  . Heteragrion denisye  can be easily distinguished from H. johndeaconi  and H. gracile  by exhibiting a blunt bilobated MP tip. The MP tip is rectangular shaped in H. johndeaconi  and “W” shaped in H. gracile  .

Two species that can be found in Minas Gerais state may resemble H. denisye  : H. cyane  and H. obsoletum Selys, 1886  . Heteragrion denisye  occurs in a locality 400 km away from the type locality of H. cyane  ( Fig. 1View FIGURE 1). Both species are only known from their type localities. In comparison with H. cyane  ( Fig. 4View FIGURE 4), H. denisye  exhibits the three portions of the cerci with some differences. In H. denisye  , BP and MP are subequal in size and AP is visibly the shortest portion. In H. cyane  , BP is the shortest whereas MP and AP are subequal. Both H. denisye  and H. cyane  have a ventrobasal expansion on the basal portion of cerci, less concave in H. cyane  ( Fig. 3aView FIGURE 3) in comparison to H. denisye  ( Fig. 4cView FIGURE 4). Heteragrion denisye  has a ventral branch on MP, with a rectangular plate-like conformity (MP in Fig. 3aView FIGURE 3), similar to H. cyane  (MP in Fig. 4cView FIGURE 4). However, in the latter, the apex of MP is rounded, while H. denisye  has MP with bilobated apex.

As for H. obsoletum  , the only comparable trait Selys (1886) mentions for H. obsoletum  is that “un renflement ou dent interne arrondie après leur milieu”, suggesting that male cerci have rounded MP. Therefore, here we consider that H. denisye  may be distinguished from H. obsoletum  by the presence of a bilobed MP, rounded in H. cyane  . We cannot make further accurate comparisons or associate H. obosoletum  with any known Heteragrion  species because of the problematics involved. First, the validity of H. obsoletum  is yet to be addressed until the holotype is found or a neotype designated. The only known specimen had its cerci lost before Selys finished its description (Selys 1886, p. 58) and nothing is known of the whereabouts of the holotype, except for its original label in the RBINS collection (Jérôme Constant pers. comm.; Fig. 5View FIGURE 5). Machado & Souza (2014) mentioned that the description of H. obsoletum  made by Selys (1886) is very poor in terms of structural characters, what hampers comparisons. Moreover, in a personal communication, Marcel Wasscher mentioned that “Unfortunately, Selys had made no drawing or notes on that species”. Second, the type locality of H. obsoletum, Caxambu  , has been visited by Ângelo Machado in several expeditions, nevertheless, specimens of H. obsoletum  could never be found (Ângelo Machado pers. comm.). Moreover, Caxambu is distant from the type localities of H. cyane  and H. denisye  ( Fig. 1View FIGURE 1).

Habitat and Ecology. This species was collected in a first order stream near to a Vereda (i.e., palm swamp) within the altitude fields (which differs from the surrounding phytophysiognomies mainly by its sparse vegetation, lacking woods and often occurring> 1.300 m asl) of the park (27 km from São Roque de Minas, entrance to the Serra da Canastra National Park, Fig. 6View FIGURE 6). The species was found perching on a shaded area of the stream ( Fig. 6aView FIGURE 6), which was quite difficult to access due to the tall grass and muddy soil. We collected several Peristicta  spp., a couple Argia  sp. and one female Franciscagrion franciscoi Machado & Bedê, 2016 in the same area.

Final remarks. Most Heteragrion  species are often characterized by their yellow/orange body coloration contrasting with dark pterothoracic stripes, mainly on the middorsal carina and mesepimeron. However, coloration seems to be a plastic trait even among conspecifics, therefore, should not be considered a reliable character for taxonomic use ( Lencioni 2013). Nevertheless, some species are known to exhibit colors that diverge from the common yellow/orange/black pattern, which are easily recognizable both in the field and in collections. For example, Machado & de Souza (2014) described H. cyane  from Minas Gerais state, a remarkable species with a blue/black body pattern. Dunkle (1989) described H. azulum  from a single male collected in Mexico, with blue-gray bands on the pterothorax and orange coloration from segments eight to ten. Heteragrion inca Calvert, 1909  also seems to present some blue thoracical colors (Rosser Garrison pers. comm). Heteragrion denisye  is certainly a remarkable species in terms of coloration, being easily distinguished from other Heteragrion  .

Finally, H. denisye  was found within a National Park that harbors many endemic and poorly known species ( Machado & Bedê 2015; Novaes et al. 2018; Cezário et al. 2018, in press). Furthermore, the habitat in which H. denisye  was collected differs from the areas where it is common to find other Heteragrion  species ( Fig. 6View FIGURE 6). Instead of inhabiting shaded areas in dense forests, H. denisye  was found in a small patch of vegetation in an open field ( Fig. 6aView FIGURE 6 ̅b). The discovery of this new species justifies the actions for species conservation in the National Park, such as the expeditions that resulted in this study, which are essential for monitoring populations of these rare and already endangered species. Furthermore, the altitude fields are known for their high degree of fauna endemism, yet are one of the most susceptible to anthropic pressures ( Vasconcelos 2014). Therefore, more collections are needed in the immediate surroundings and other areas of the park to find additional populations of these species.