Cybister Curtis, 1827

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson, 2024, Reclassification of Cybistrinae Sharp, 1880 in the Neotropical Region (Coleoptera, Adephaga, Dytiscidae), with description of new taxa, ZooKeys 1188, pp. 125-168 : 125

Cybister Curtis, 1827

Figs 5 , 7 , 9 , 10 , 15-18 , 30-35 , 51 , 52 , 58 , 59 , 66 , 72

Type species.

Dytiscus lateralis Fabricius, 1798.

Diagnosis.

Within Cybistrinae Cybister is characterized by the following: (1) a series of setae present along the posteroventral apical margin of the mesotarsomeres of males and pro- and mesotarsomeres of females (Fig. 5 ); (2) males with a single metatarsal claw, females with one or two, and if two, then the posterior claw small (some species with females dimorphic, some with a small posterior claw, others with only a single claw) (Figs 15-18 ); and (3) the medial margin of the lobes of the male abdominal sternite IX emarginate (Figs 51 , 52 ). Larvae of Cybister (Neocybister) are unknown.

Distribution.

Cybister are found in all major biogeographic regions but are most diverse in the Afrotropical and Oriental regions, mainly in low latitudes. The group is not diverse in the Neotropical region where it is largely replaced in numbers of species and individuals by species previously in Megadytes (Megadytes) (most of these in a newly described genus, see below).

Phylogenetic relationships of Neotropical Cybister .

Cybister is the sister group to Megadytes as newly constituted (Figs 54 , 76 , see below). The Neotropical species of Cybister are in the subgenus Cybister (Neocybister) Miller, Bergsten & Whiting, 2007, which is restricted to the New World ( Miller et al. 2007). This subgenus was resolved as sister group to all other Cybister in the analysis by Miller et al. (2007). It is resolved nested within Cybister here based on morphological data (Figs 75 , 76 ), although previously examined molecular data ( Miller et al. 2007) are not analyzed here. More investigation is needed. The two South American species are different from other Cybister in having (1) females always with a second, rudimentary posterior claw (Figs 15-18 ), (2) the medial margin of the gonocoxa distinctly emarginate (Figs 58 , 59 ), and (3) the apex of the ventral sclerite of the male median lobe distinctly bifid (Figs 31 , 34 ).

Figures

Figure 72. Cybister (Neocybister) festae, lectotype male (left) and paralectotype female (right). Photograph courtesy of F. Giachino, MRSN.

Figure 75. One of seven cladograms derived from parsimony analysis of 57 morphological characters from Cybistrinae and other Dytiscidae (len = 105, CI = 68, RI = 92) with characters mapped using ' fast' optimization in WinClada. Black hash marks indicate unambiguous changes, white hash marks indicate homoplasious changes or reversals. Numbers above hash marks are character numbers, those below hash marks are derived state numbers.

Figure 76. Consensus cladogram of seven equally parsimonious cladograms from parsimony analysis of 57 morphological characters from Cybistrinae and other Dytiscidae morphology.

Figures 1 - 8. Cybistrinae morphological features 1 Bifurcitus lherminieri, right metatibia, posterior surface 2 Bifurcitus lherminieri, left metaleg, anterior surface 3 Trifurcitus robustus, left metaleg, anterior surface 4 Metaxydytes fraternus, left mesotarsomeres III-V, posterior surfaces 5 Cybister tripunctatus, left mesotarsomeres III-V, posterior surfaces 6 Megadytes latus, left half of metaventrite and left metacoxa (WV = metaventrite wing width, WC = metacoxal width) 7 Cybister tripunctatus, right metathoracic wing 8 Trifurcitus robustus, right metatrochanter, ventral surface. Scale bars: 1.0 mm.

Figures 9 - 14. Neotropical Cybistrinae species, habitus 9 Cybister festae 10 Cybister puncticollis 11 Nilssondytes diversus 12 Megadytes parvus 13 Megadytes latus 14 species " IR 57 " (Ribera et al. 2008). Scale bar: 10.0 mm.

Figures 15 - 29. Neotropical Cybistrinae species, metatarsal claws and tarsomere VI of males and females 15, 16 Cybister festae 17, 18 Cybister puncticollis 19, 20 Nilssondytes diversus 21, 22 Megadytes latus 23, 24 Megadytes parvus 25 species " IR 57 " (Ribera et al. 2008) 26, 27 Paramegadytes glaucus 28, 29 Metaxydytes fraternus. Scale bars: 1.0 mm.

Figures 30 - 50. Neotropical Cybistrinae species, male genitalia 30 - 32 Cybister festae: 30 median lobe, right lateral aspect 31 median lobe, ventral aspect 32 right lateral lobe, right lateral aspect 33 - 35 Cybister puncticollis: 33 median lobe, right lateral aspect 34 median lobe, ventral aspect 35 right lateral lobe, right lateral aspect 36 - 38 Nilssondytes diversus: 36 median lobe, right lateral aspect 37 median lobe, ventral aspect 38 right lateral lobe, right lateral aspect 39 - 43 Megadytes parvus: 39 median lobe, right lateral aspect 40 median lobe, ventral aspect 41 right lateral lobe, right lateral aspect 42 apex of median lobe, right lateral aspect 43 apex of median lobe, ventral aspect 44 - 47 Megadytes latus: 44 median lobe, right lateral aspect 45 median lobe, ventral aspect 46 right lateral lobe, right lateral aspect 47 apex of median lobe, ventral aspect 48 - 50 species " IR 57 " (Ribera et al. 2008): 48 median lobe, right lateral aspect 49 median lobe, ventral aspect 50 right lateral lobe, right lateral aspect.

Figures 51 - 57. Neotropical Cybistrinae species, male sternite IX, ventral aspect 51 Cybister festae 52 Cybister puncticollis 53 Nilssondytes diversus 54 Megadytes latus 55 Megadytes parvus 56 Paramegadytes glaucus 57 Metaxydytes fraternus. Scale bars: 1.0 mm.

Figures 58 - 61. Neotropical Cybistrinae species, female genitalia including left gonocoxosternite, ventral aspect, except Fig. 60 without internal genitalia 58 Cybister festae 59 Cybister puncticollis 60 Megadytes latus 61 Nilssondytes diversus. Scale bars: 1.0 mm.

Figures 62 - 66. Neotropical Cybistrinae species, female genitalia including left gonocoxosternite, ventral aspect 62 Metaxydytes fraternus 63 Paramegadytes glaucus 64 Bifurcitus lherminieri 65 Trifurcitus robustus 66 Cybister fimbriolatus. Scale bars: 1.0 mm.