Inaequalium, Coscaron & Wygodzinsky, 1984

HERNANDEZ, LUIS MIGUEL, SHELLEY, ANTHONY JOHN, DE LUNA DIAS, ANTONIO PAULINO ANDRADE & MAIA-HERZOG, MARILZA, 2007, Review of the Neotropical blackfly subgenus Chirostilbia Enderlein (Diptera: Simuliidae) based on adults and pupal morphology, Zootaxa 1649 (1), pp. 1-96 : 6-12

publication ID	https://doi.org/ 10.11646/zootaxa.1834.1.1
persistent identifier	https://treatment.plazi.org/id/039987D4-FFDE-FF8B-9580-FCFFFD0DFAF3
treatment provided by	Felipe
scientific name	Inaequalium
status

Treatment

The subgenus Inaequalium

Literature review

In this section we summarize the previous work on the subgenus Inaequalium followed by our own conclusions and our proposed grouping of species within this subgenus. We have largely drawn upon Coscarón’s treatment of the Neotropical fauna (1987) and based our arrangement on Crosskey’s classification in his annotated world list ( Crosskey & Howard, 2004).

Previous work

Coscarón (1980) during a revision of some Simuliidae species inhabiting the coastal region of Brazil redescribed S. botulibranchium Lutz and described two new species, S. souzalopesi and S. petropoliense . In this paper, he mentioned that these species “constituted a small group with an affinity to the subgenus Inaequalium ”. The three species described in the paper were similar to species of Inaequalium in adult coloration, setation of the thorax and abdominal chaetotaxy of the pupa as well as the relative proportions of the antennal segments, and the form of the hypostomium in the larva. Differences in the form of the female paraproct, gonocoxite (as basímero), gonostyle (as distímero) and ventral plate of the male and also the pupal gill form precluded their formal inclusion in this subgenus. However, it was suggested that these species might possibly be included as a separate group within Inaequalium . Unfortunately, he failed to record the species present in the subgenus Inaequalium or give a diagnosis for this subgenus. As the name Inaequalium was published with no named species, designation of type species or subgeneric diagnosis Crosskey (1988) considered Inaequalium as an unavailable name [see also International Code of Zoological nomenclature (1999), articles 11 and 13].

The subgenus Inaequalium was formally described by Coscarón & Wygodzinsky in 1984 in their revision of the species of the subgenera Psaroniocompsa and Inaequalium . In this paper, the authors described all morphological characters necessary to recognize the species in this subgenus, selected Eusimulium inaequale (described by Paterson & Shannon in 1927) as the type species of Inaequalium , and presented a cladrogram outlining the phylogenetic relationships between the species that they assigned to Inaequalium . Other taxonomic features in this paper are as follows: S. mariavulcanoae was described as a new species; two species, S. baiense Pinto and S. pseudoexiguum Nunes de Mello & Barbosa de Almeida (see also Table 1) were included as species inquirendae; and five new synonyms were proposed for S. inaequale (= Trichodagmia manicata Enderlein , S. jundiaiensis D’Andretta & González B ), S. subnigrum Lutz (= S. diversifurcatum Lutz , S. mbarigui Coscarón ) and S. diversibranchium Lutz (= S. missionum Coscarón ).

Coscarón & Wygodzinsky (1984) recognized the difficulty in identifying the adults of Inaequalium and Psaroniocompsa species and stated that “…both subgenera are composed of morphologically similar sympatric species…” (see also Appendix 1 for more details). They had reviewed both subgenera together because of the similarity in coloration of the thorax (black laterally and grey posteriorly) and abdomen of adults, female paraprocts short and wider than long, pupal gill with six long, fine filaments (exceptionally four or 2–3 thick filaments), and similar coloration and morphology of the hypostomium, mandibular teeth, and anal gills in the larva. They concluded that both subgenera must have shared a common lineage, but still regarded Psaroniocompsa and Inaequalium as separate taxa. The authors also provided a table to distinguish Inaequalium from Psaroniocompsa . Their main characters to distinguish Inaequalium were as follows: adults with hairs on basal section of R; female with gonapophyses distally narrow and with or without scattered microtrichiae and internal margins divergent and weakly sclerotized; male with subtriangular to subtrapezoidal gonostyle with terminal spine; pupa with trifid to quadrifid trichomes; larva with cephalic apotome “not always positive”, “not very distinct”, sometimes delimiting a subbasal, median clearer window; larval third antennal segment much longer than first and second segments. In the same paper the authors ( Coscarón & Wygodzinsky, 1984) also emphasized the variation in size, adult thoracic pubescence and the pupal gill configuration in these two subgenera. Their species group analysis of Inaequalium separated “…with certain effort…” S. travassosi from the other species because of its pupa with three filaments and different proportions of the genital fork.

Several species now considered to belong to Inaequalium had been previously placed in different subgenera within Simulium . The major changes are listed in Table 1, with a detailed diagnosis for the subgenus by different authors given in Appendix 1. The first comprehensive paper on Inaequalium specie s is that of Coscarón & Wygodzinsky (1984) who provided species descriptions, but did not allocate them to species groups. Simulium nahimi , described by Py-Daniel (1984) from Mato Grosso State in Brazil, was assigned by the author to Inaequalium . Coscarón in 1987 produced the most comprehensive treatment of the subgenera and species of Simuliidae in the Neotropical Region. He divided species of the subgenus Inaequalium into two species groups, the inaequale group (11 species) and botulibranchium group (three species) based on adult genitalia, pupal gill configuration and girth, and morphology of the larval hypostomium. He also placed S. baiense , S. lurybayae and S. pseudoexiguum as species inquirendae. However, Crosskey (1988) in his world list of Simulium species apparently followed Coscarón & Wygodzinsky (1984) in their concept of Inaequalium , but considered S. nahimi as a member of the subgenus Cerqueirellum Py-Daniel [now a synonym of Psaroniocompsa ], and left the following species “unassigned to subgenus”: S. botulibranchium , S. clarki , S. lurybayae , S. nogueirai D’Andretta & González , S. petropoliense , S. rappae Py-Daniel & Coscarón , and S. souzalopesi . In both publications, the name of S. parimaense [described by Ramírez-Pérez et al. (1986) from Venezuela as S. parimaensis ] is missing from the species list in Simulium . A further species, S. nogueirai , described by D’Andretta & González B. (1964), was presumed misplaced by Py-Daniel & Moreira (1989), who redescribed it and assigned it to the subgenus Inaequalium . These authors also added some morphological characters to recognize the members of this subgenus (see Appendix 1).

Coscarón (1991) reviewed all subgenera and species occurring in the “Cono Sur” region of South America [ Argentina, Chile, southern Bolivia, Paraguay, Uruguay and S.E. Brazil] and provided a diagnosis of Inaequalium (see Table 1, Appendix 1). He presented a key to separate the adults and pupal stages for 15 species of Inaequalium [not 14 as cited in the paper] in the Neotropical Region, but only fully treated those species (11 in total) that occur in the Cono Sur. However, he did not include in the key S. pseudoexiguum and S. nogueirai , despite stating that it included all species for the Neotropical region. The major changes in this paper are as follows: he only recorded Inaequalium extending from Venezuela to Argentina [ S. clarki synonymized with S. inaequale by Hernández et al. (2007) occurs in Panama]; S. petropoliense and S. parimaense were not included in the key to females; he assigned S. lurybayae to the botulibranchium species group; and regarded S. baiense as a junior synonym of S. inaequale .

Py-Daniel & Moreira Sampaio (1994a) proposed recognition of only two higher categories in Simuliidae , and they elevated all subgenera to genera. This action was then applied by Py-Daniel & Moreira Sampaio (1995) to the Brazilian fauna [see also Py-Daniel & Moreira Sampaio (1994b) for new specific name changes in Simuliidae ] and included only 14 species for this country. However, this system has not been followed by Crosskey & Howard (1997) in their “World Inventory of Simuliidae ” and three subsequent updates that followed ( Crosskey, 1999, 2002; Crosskey & Howard, 2004). It is evident that the latter authors followed the previous papers of Coscarón (1987, 1991) for the classification of Inaequalium and treated S. pseudoexiguum as “species unplaced to group”. However, they regarded S. parimaense as a “species unplaced to group” in the subgenus Psaroniocompsa . In a subsequent paper Coscarón & Miranda-Esquivel (1998) published a scientific note dealing with synonyms of S. inaequale . They maintained those proposed in Coscarón & Wygodzinsky (1984) and Coscarón (1991) for S. inaequale , and also synonymized Thyrsopelma argentata Enderlein with this species.

Since then species in Inaequalium have received a lot of attention and several authors have published reviews and phylogenetic analyses independently. Coscarón & Coscarón-Arias (1997) produced a phylogenetic analysis of 13 species of the subgenus Inaequalium together with the subgenera Chirostilbia and Psaroniocompsa . For Inaequalium they used the subgenus Notolepria as the outgroup. They did not include in their analysis S. beaupertuyi Ramírez-Pérez, Rassi & Ramírez , S. nogueirai [related to S. subnigrum ], and S. clarki , S. lurybayae [related to S. inaequale ] because of lack of material. However, in a distribution map for all species in Inaequalium they figured the distribution of S. clarki and S. beaupertuyi . They recognized two species groups: the botulibranchium and inaequale species groups. Within the inaequale group, S. parimaense formed an independent clade, and they concluded that S. travassosi and S. rappae formed a subgroup within the inaequale group. Strieder et al. (1992) provided a key to identify those species found in the state of Rio Grande Sul and treated Inaequalium as a genus. Strieder and Py-Daniel (1999, 2000) also regarded Inaequalium as a genus and studied those characters that define this taxon based on immature stages. In their latest paper Strieder & Py-Daniel (2000) described S. leopoldense [as I. leopoldense ] based only on larvae and pupae from São Leopoldo, Rio Grande do Sul. Another phylogenetic tree was constructed by the same authors, Strieder & Py-Daniel (2002), in which they only recognized two species groups as before, and two subgroups within the inaequale group. In this paper S. travassosi was transferred from the inaequale to the botulibranchium species group. More recently, in a paper on the Simuliidae of Belize Shelley et al. (2002) discussed the taxonomic position of S. quadrivittatum Loew , and mistakenly attributed its placement in the subgenus Inaequalium to Coscarón (1987). In the latter paper the quadrivittatum group followed on from the subgenus Inaequalium , but was considered by the author to have subgeneric rank and the term species subgroup was used in place of species group. In subsequent publications the author used the universally accepted definition for species group.

Two new species have been recently described that pertain to Inaequalium : S. maranguapense and S. margaritatum by Pessoa et al. (2005) and Pepinelli et al. (2006), respectively. Neither species was allotted to a species group. More recently, Hernández et al. (2006) reviewed the taxonomy of S. petropoliense in which the larva and the male were described for the first time, the female and pupa were redescribed, and illustrations of the pupal gill variation and comparisons with other species in the botulibranchium were provided.

The most recent classification of Inaequalium was provided in the overview of the Neotropical Simuliidae by Coscarón & Coscarón-Arias (2007). These authors included 14 species in the subgenus [actually 17 and three as species inquirendae not here included in the total] of which 14 were allocated to the inaequale and three to the botulibranchium species group (Table 1). In the same publication the authors added the name, S. hauseri [as I. hauseri ] described by Strieder (1998) from Brazil. Their new diagnosis for this subgenus is essentially the same as those provided previously (e.g., Coscarón, 1987, 1991; Table 1) with the omission of information on coloration of antennae, pleura, legs, description of Lutz’s organ, and additional information on the adult genitalia, pupal cocoon and larva. They separated the two species groups as in previous publications with additional information on features of the cibarium and gill (see Table 1).

More recently, Hernández et al. (2007) dealt with new synonymies of Simuliidae in the Neotropical region and proposed the following synonyms in the subgenus Inaequalium : for S. inaequale ( T. manicata , S. clarki , S. pseudoexiguum ) and for S. subnigrum ( S. subclavibranchium Lutz , S. nahimi , S. nogueirai , S. beaupertuyi , and I. leopoldense ). In the same paper, these authors designated a neotype for S. inaequale , a lectotype for S. subclavibranchium , clarified which life stage was designated as the holotype of S. [as Inaequalium ] leopoldense , and provided additional information on the preservation and condition of all type species that they had examined.

Our conclusions

We prefer the broader approach of Coscarón (1987), Coscarón & Coscarón-Arias (2007) and Crosskey & Howard (1997, 2004) in the treatment of Inaequalium as a subgenus, instead of that of Py-Daniel & Moreira Sampaio (1994a, b), Py-Daniel (1995), and Strieder & Py-Daniel (2000, 2002) who consider Inaequalium as a genus. We have maintained species group names of Coscarón ( Coscarón, 1987, 1991; Coscarón & Coscarón- Arias, 2007). In our classification of the subgenus Inaequalium not all species clearly fit into groups because of the overlap in characters.

We have based our species groups only on characters that we consider to generally show relatively minimal intraspecific variation in the Neotropical fauna. These are: scutal pattern, cibarium, adult genitalia, and cocoon and gill morphology of pupae. We have used a suite of these characters and species have been placed in a species group when most of the characters in that species coincide with those of the species group. We maintain the division of the subgenus Inaequalium into the botulibranchium and inaequale species groups. The most obvious characters separating the two groups are the form of the female cercus and paraproct, the male gonostyle and ventral plate and the pupal gill. The use of these characters in determining phylogenetic relationships may only be adequately resolved when considered in combination with cytological and molecular characters. It has been suggested by several authorities, e.g. Crosskey (1988), Shelley (1988), Crosskey & Howard (1997), that Inaequalium might be better subsumed within Psaroniocompsa due to the their morphological similarity. We support this suggestion here. However, this still needs further investigation in relation to species of other subgenera in the Neotropical Region and a final decision will be made following this analysis in the forthcoming revision of “ The Simuliidae of Brazil by A.J. Shelley, L.M. Hernández, M. Maia-Herzog, A.P.A. Luna Dias & P.R. Garitano’.

Classification

Our classification of Inaequalium has been derived from that proposed by Crosskey & Howard (2004) with two subsequent species descriptions by Pessoa et al. (2005) and Pepinelli et al. (2006). The 20 species under Inaequalium have now been reduced to 14 valid species (including two species inquirendae) through the recent synonyms proposed by Hernández et al. (2007) and in this paper. All species are listed in alphabetical order within each species group. Valid species are given in bold and italics, with synonyms in italics.

BOTULIBRANCHIUM species group

botulibranchium Lutz, 1910 View in CoL

petropoliense Coscarón, 1980 View in CoL

souzalopesi Coscarón, 1980 View in CoL

INAEQUALE species group

clavibranchium Lutz, 1910 View in CoL

diversibranchium Lutz, 1910 View in CoL

missionum Coscarón, 1976 View in CoL

inaequale Paterson & Shannon, 1927

baiense Pinto, 1932 View in CoL

manicatum ( Enderlein, 1934)

clarki Fairchild, 1940 View in CoL