Dyscolus denigratus ( Bates, 1891 )

Moret, Pierre & Murienne, Jérôme, 2020, Integrative taxonomy of the genus Dyscolus (Coleoptera, Carabidae, Platynini) in Ecuadorian Andes, European Journal of Taxonomy 646, pp. 1-55 : 43

Dyscolus denigratus ( Bates, 1891)

Figs 45–50

Colpodes denigratus Bates, 1891: 17 .

Dyscolus palatus Moret, 1998: 18 . syn. nov.

Dyscolus (Dyscolus) denigratus – Moret 2005: 128.

Dyscolus (Dyscolus) palatus – Moret 2005: 130.

Dyscolus denigratus is a highly variable species, with a broad range of variation within each population regarding body size, form of the pronotum, length of the legs, and form of the apex of the male aedeagus ( Figs 45–46, 48–50 ). The tree based on the COI sequences separates two clades (Fig. 2): one in the south-west part of the area of D. denigratus , represented in our dataset by the Cotopaxi and Pichincha populations, vs a north and north-east zone represented by the Cotacachi, Cayambe and Guamaní populations. Additionally, three species-level units are recognized through BIN analysis: the first one embraces the populations of the south-western clade, including specimens identified as D. palatus . The northern clade is split into two BIN units: one for the Guamaní population, and another for the Cotacachi and Cayambe populations. However, we were unable to find any morphological character that reliably reflects these divisions. According to the form of the apex of the median lobe, the Cotacachi population ( Fig. 49 ) seems to be closer to the Pichincha population ( Fig. 50 ) than to the Guamaní one ( Fig. 48 ), in contradiction with the molecular results. Obviously, the phylogeny of the denigratus complex cannot be resolved from the COI sequences alone.

We thus take a conservative approach, with no taxonomic decision regarding the specific or subspecific status of the components of the denigratus complex, except for the synonymy of Dyscolus palatus with Dyscolus denigratus . Dyscolus palatus was described from specimens from the Pichincha, Atacazo and Corazón volcanoes in the Western Cordillera ( Fig. 47 ). This taxon was then thought to be more closely related to D. altarensis ( Bates, 1891) than to D. denigratus , due to its relatively broader and shorter body. The specimen of D. palatus included in our analysis (COI voucher PM359-01, BOLD sequence SUM168- 18) instead suggests that D. palatus and D. denigratus are conspecific. A re-examination of the type series of D. palatus and of large series of specimens recently collected on the Pichincha shows that the body dimensions of the two taxa partly overlap ( Fig. 51 ). Owing to the existence of these transition forms, D. palatus cannot be maintained as a good species and we therefore treat it as a synonym of D. denigratus .

Figures

Figs 45–50. Dyscolus spp., habitus (45–47) and aedeagus, median lobe in lateral view (48–50). 45. D. denigratus (Bates, 1891), male specimen from Guamaní. 46. D. denigratus, male specimen from Guagua Pichincha (type locality). 47. D. palatus Moret, 1998, male paratype from Atacazo. 48– 50. D. denigratus. 48. From Guamaní. 49. From Cotacachi. 50. From Guagua Pichincha.

Fig. 51. Compared dimensions of the elytra of Dyscolus denigratus (Bates, 1891) and D. palatus Moret, 1998.