Convexocoleus decemmaculatus Sekerka 2016
Creators: name: Sekerka, Lukáš
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Convexocoleus
Convexocoleus decemmaculatus

description: Convexocoleus decemmaculatus (Blake, 1930) stat. restit. & comb. nov.
Stoiba decemmaculata Blake, 1930: 221 (original description).
Type locality. Cuba, Oriente Province, Sierra Maestra, 1070–1350 m a.s.l.
Type material examined. HOLOTYPE: pinned, ‘ Sierra Maestra, Cuba. | Julio 10-20 de 1922. | Col.C.H.Ballou y | S.C.Brunner | 1070-1350 M. [w, p, cb, last row hw] || E.E.A. de | Cuba, No. 92.98 [w, p, cb, last row hw] || Type No. | 43118 [hw] | U.S.N.M. [r, p, cb] || Stoiba | decemmaculata | Blake [w, p, cb]’ (USNM).
Remarks. BLAKE (1930) mentioned that this species does not fit well into the key in which SPAETH (1909a) described the genus Stoiba Spaeth, 1909 because its antennomere V is intermediate in character between basal and apical antennomeres. She added that on the other hand S. decemmaculata is similar in punctation and also general shape to S. angusticollis (Suffrian, 1868).
CHABOO (2000) transferred S. decemmaculata to Elytrogona Chevrolat, 1836 and synonymized it with E. bulla Boheman, 1862 based on (1) the fact that BLAKE (1930) compared her species to E. bulla and (2) a label by Pallister pinned under one of the additional specimens of S. decemmaculata she examined with note that the two taxa differ only in colour. However, even from the original description of E. bulla it is clear that these two taxa cannot be conspeficic because BOHEMAN (1862) mentioned most coarsely punctate elytra as was also pointed by BLAKE (1930) because the type series of S. decemmaculata was previously identified as E. bulla. However, the latter species is completely different and is in fact the same as E. gemmata Blake, 1930. For additional information see remarks under E. bulla.
CHABOO (2000) supported her placement of S. decemmaculata in Elytrogona by a cladistic analysis of 12 morphological characters and S. decemmaculata + other species of Elytrogona were supported by three apomorphies: dorsally convex body, elytra with maculation, and pointed tarsal claw. However, four characters separated S. decemmaculata from other species of Elytrogona: slightly inflated prosternal process, elytra finely punctate, brachypterous hind wings, and receptacle of spermatheca not inflated. These four characters actually unite S. decemmaculata with other species of Stoiba included in the analysis. Chaboo did not further discuss the curious placement of S. decemmaculata in Elytrogona nor did she comment on individual characters, but only redefined the genus Elytrogona based on the new transfer.
The three apomorphies uniting S. decemmaculata with Elytrogona were incorrectly sampled. It is true that S. decemmaculata and all species of Elytrogona have strongly convex elytra but the latter have elytra much more gibbous than in S. decemmaculata which has elytra similarly convex to some other species of Stoiba (e.g. S. angusticollis or S. brunneri Blake, 1930). Also all species of Stoiba including S. decemmaculata have apex of elytra rounded with very narrowly explanate margin and continuously sloping while Elytrogona has apex of elytra acuminate with horizontally projecting explanate margin thus discontinuously sloping. All species of Elytrogona have the basal tooth of claws clearly sharply pointed and projecting, providing the claw with a bifid appearance. In contrast, S. decemmaculata and all other species of Stoiba have it subquadrangular with the lower margin more or less curved. It is important to note that in both Stoiba and Elytrogona, the shape of the basal tooth is somewhat variable within each genus and species as it also depends on the size of an actual specimen. However, its general shape is constant and no species of Stoiba has apparently bifid claws like Elytrogona. Use of elytral maculation in this case is disputable as it probably has no phylogenetic signal because size of the spots on elytra in Elytrogona is depending on altitude. Lowland populations have small spots while montane have them greatly enlarged and respective colour forms were described as distinct taxa. On the other hand other important characters (shape of pronotum and antennae) clearly separating S. decemmaculata from other species of the genus and also from Elytrogona were not discussed.
SHIN & CHABOO (2012) included S. decemmaculata (as E. bulla) in the cladisctic analysis of the genus Stoiba. They noticed the difference in the shape of pronotum and included it as character 12 (the shape of basal line of pronotum) in the phylogenetic analysis. They recognized three states of this character: linear, sinuate and rounded. However, based on the character matrix and consensus tree this character was wrongly scored in all species of Stoiba. Their basal margin of pronotum was considered as rounded while in fact it is sinuate and of the same shape as in Chelymorpha and Phytodectoidea Spaeth, 1909 included in the analysis and correctly scored as taxa with sinuate basal margin of pronotum. Stoiba was resolved as a separate clade sister to Chelymorpha + Phytodectoidea + Stolas + Elytrogona, for which the sinuate base of pronotum was resolved as an apomorphy. It should therefore also include Stoiba the consensus tree and is thus erroneous. Stoiba decemmaculata was resolved as sister to remaining species of Elytrogona and the whole group was supported by six apomorphies and three homoplasies, however, the topology of the tree would have been probably quite different if the characters were scored correctly.
Most recently, SHIN (2013) described Convexocoleus Shin, 2013, a new genus of Mesomphaliini from Haiti (superficially similar to Elytrogona and Stoiba) and performed cladistic analysis based on morphological characters to resolve its position and answer some phylogenetic implications. The character matrix was modified from the previous analysis (SHIN & CHABOO 2012) with inclusion of new taxa and additional characters. The shape of the base of pronotum was corrected in Stoiba, however, the original character was split in two and scoring of its states across sampled taxa is dubious as the interpretation is subjective due to minor differences among individual states. The same is true for some other characters including the shape of tarsal claws. SHIN (2013) stated that the shape of basal tooth of claws in Convexocoleus is similar to that of Botanochara and completely ignored their similarity to Stoiba, in which the shape was scored as different state than in Convexocoleus. In the analysis Stoiba decemmaculata (as E. bulla) was again resolved as sister to remaining species of Elytrogona. Convexocoleus, Elytrogona and Stoiba were resolved as not closely related and SHIN (2013) suggested three independent origins of flightlessness.
Phylogenetic analyses of Cassidinae based only on morphological characters of adult specimens are dubious, particularly among true cassidines, which are characterized by reductions rather than evolving new structures. As a result most taxa are based on combinations of several dozens of characters, which mostly represent homoplasies. It is evident even in the higher classification of Cassidinae s. str., in which entire tribes lack unique characters. Therefore analyses purely based on morphological characters of adult specimens are speculative and it is necessary to combine them with characters of immature stages and molecular data to obtain reasonable results.
As I mentioned above S. decemmaculata is in my opinion not congeneric with Elytrogona nor with Stoiba. Generally it is more similar to Stoiba as it has the same morphology of spermatheca, shape of elytra and basal tooth on claws and also the punctation of elytra is alike while the shape of pronotum is similar to Elytrogona, particularly E. bulla (= E. gemmata), but is separated from both by formation of antennae. Stoiba and Elytrogona have shorter and more robust antennae with tightly arranged antennomeres, which are gradually thickening from antennomere III to apex and only four basal antennomeres are sparsely pubescent and shiny. Stoiba decemmaculata has longer and slimmer antennae with loosely arranged antennomeres, which are thickening from antennomere VI, antennomeres I–V are slim, filiform, sparsely pubescent and shiny.
I did not examine any specimen of the recently described Convexocoleus rileyi Shin, 2013 but according to the figures in original description it has very similar formation of antennae, basal tooth on claws and elytra including punctation as S. decemmaculata. It clearly differs in the shape of pronotum, which is basally constricted, laterobasally with small angulation and the explanate margin is bent upwards while C. rileyi has broadly rounded basal corners of pronotum and explanate margin nearly horizontal. Despite the shape of pronotum I hereby transfer S. decemmaculata to Convexocoleus as other important morphological features are quite similar rather than proposing a new genus for it. However, concerning the circumstances this transfer must be understood as tentative. Further study including comparison of genitalia of Convexocoleus is desirable to verify the placement.
Distribution. Cuba (BLAKE 1930, CHABOO 2000).
description: Published as part of Sekerka, Lukáš, 2016, Taxonomic and nomenclatural changes in Cassidinae (Coleoptera: Chrysomelidae), pp. 275-344 in Acta Entomologica Musei Nationalis Pragae 56 (1) on pages 322-325, DOI: 10.5281/zenodo.5305725