INFOWEB 12 :
Within a biogeographical review of Cynolebias et al.,
Simpsonichthys is revised and split by Costa

From Jean H. Huber
Private address: 7 Bd Flandrin, 75116 Paris, France
M.N.H.N., Ichthyology, 43 rue Cuvier, 75231 PARIS Cedex 05.
e-mail : huber@mnhn.fr, author@killi-data.org [today both inactive]
S.F.I. : Société Francaise d'Ichtyologie (same address).

Paris, November 30. 2010 [updated on July 1. 2015… Simpsonichthys, Nematolebias, Xenurolebias, on March 31. 2016, new molecular publication contradicts many of Costa's morphological and distributional analyses, see addendum].

Dear Colleague, dear Aquarist!

Wilson Costa has published an important paper on biogeography of South America. This is a major work which attempts to link morphological groups with currently known ancestral biogeography (mainly movements of rivers) ; it covers the analysis of the biogeographical events responsible for the present distribution of cynolebiasine (= Cynolebiinae) killifishes (i.e. all species belonging to the genera Cynolebias and its allied, notably Simpsonichthys), a diversified and widespread Neotropical group of annual fishes threatened with extinction, from South America, focusing on the main river basins draining the Brazilian Shield and adjacent zones ; the analysis is based on 214 morphological characters of 102 species, in conjunction with a dispersal-vicariance analysis based on the distribution of all species among 16 areas of endemism (using 2 computer programmes, TNT for the morphological characters and DIVA for the biogeographical events). The 16 described areas of endemism are : (A) Eastern Brasil: numerous small river basins of the eastern coastal plains of Brazil, as well as the lower courses of 3 larger rivers (Jequitinhonha, Pardo and Doce); (B) Central Brasilian Plateau: the plateau comprising the upper section of streams running to the Parana, Sao Francisco, Tocantins and Araguaia rivers; (C) Paraguay: the western part of the Paraguay river basin; (D) Guaporé : Guaporé river drainage of the Madeira river basin; (E) Xingu: the middle–lower section of the Xingu river basin; (F) Araguaia: the middle section of the Araguaia river basin; (G) Tocantins: the middle section of the Tocantins river basin; (H) Jequitinhonha: the middle section of the Jequitinhonha river basin above Salto da Divisa falls; (I) Sao Francisco: the middle section of the Sao Francisco basin north of the city of Sao Francisco, as well as the middle section of the Paraguaçu, Vaza-Barris and Itapicuru river basins; (J) Urucuia: Urucuia and Paracatu river drainages of the Sao Francisco river basin and adjacent areas; (K) Parana: Parana river drainage of the Tocantins river basin; (L) Northeastern Brazil: Jaguaribe river and smaller adjacent coastal basins; (M) La Plata: the lower La Plata river basin and middle–lower Uruguay river basin; (N) Negro: Negro river drainage of the Uruguay river basin, and upper and middle sections of the Jacui, Santa Maria, Jaguarao and Quarai river drainages; (O) Patos: Patos lagoon system andadjacent coastal plains to the south; and (P) Iguaçu: the middle section of the Iguaçu river basin.

Summerized results : the basal group lineage is hypothesized to be derived from an old vicariance event occurring just after the separation of South America from Africa, when the terrains at the passive margin of the South American plate were isolated from the remaining interior areas ; this would have been followed by geodispersal events caused by river-capturing episodes from the adjacent upland river basins to the coastal region ; optimal ancestral reconstructions suggest that the diversification of the group in north-eastern South America was first caused by vicariance events in the Parana-Urucuia-Sao Francisco area, followed by dispersal from the Sao Francisco to the Northeastern Brazil area; the latter dispersal event occurred simultaneously in two different subgroups, possibly as a result of a temporary connection of the Sao Francisco area before the uplift of the Borborema Plateau during the Miocene ; the diversity of the species inhabiting the Paraguay area is hypothesized to be derived from 2 processes: an older vicariance event (about 30 Million years ago) separating Paraguay from southern Amazonian areas (Guapore-Xingu-Araguaia-Tocantins), and a series of more recent dispersal and vicariance events (about 15-11 Million years ago) caused by successive marine transgressions, which permitted alternating biotic exchange and isolation in the Paraguay, La Plata, Negro and Patos areas ; as a consequence, each morphospecies appears to be (more or less… with unresolved major mysteries) to a biogeographical unit and that is milestone in our understanding of that group of Killifish.

The next issue is however distinct from the main theme of the paper : the author derives from that analysis a major shift in systematics by proposing (without new data) a split of the genus Simpsonichthys into 5 distinct genera Simpsonichthys, Hypsolebias, Spectrolebias, Xenurolebias, Ophthalmolebias (Spectrolebias is then revalidated) ; in total, according to him, the phylogeny of Cynolebiinae supports 8 lineages corresponding to formally recognized genera, first the 3 three basal lineages (Nematolebias, Xenurolebias, Ophthalmolebias) are endemic to the eastern Brazilian coastal plains, whereas the other 5 lineages (Simpsonichthys, Hypsolebias, Spectrolebias, Cynolebias, Austrolebias) occur in the remaining South American areas analysed.

What are the impacts of Costa's reshuffling of the genus Simpsonichthys? 

Here is a table that summerizes the changes (they are not followed in Killi-Data presently, see conclusion).

Will Killi-Data online follow the impacts of Costa's reshuffling of the genus Simpsonichthys ?

As discussed in details in the preceding newsletter INFOWEB 11, Killi-Data will not automatically align to generic moves derived from research, notably when diagnoses remain weak.
In the present case the matrix is impressive, but the author himself states that no new criteria have been added to previous studies (by Costa, too), just taxa described in the mean time. While it is important for biogeographical analysis, the work does not transform the situation at the systematic level. Basically in the present paper, Costa splits the genus Simpsonichthys by upgrading its already described subgenera to the genus rank (and consequently revalidating his own genus Spectrolebias previously moved as a synonym or a subgenus), likewise a few years ago, he already split the then lumped genus Cynolebias and upgraded Simpsonichthys as a distinct large genus. As a consequence, his various new genera tend to represent each a morphospecies (or superspecies, to use a "very old" concept, fashionable in the nineteen sixties and enhanced by J.J. Scheel).
This moves with numerous names changes appears then more philosophical (and splitting-driven) with little added value to the nomenclature which promotes stability and reason.
This move will then not be followed by Killi-Data, until strong and solid diagnoses are proposed which show that the split situation reflects better the phylogeny than previously.
In practical terms, the names prevailing in Killi-Data until further evidence are the previous ones, with only 2 genera Simpsonichthys and Nematolebias.

[addendum (July 1. 2015), : a new work with molecular data processed through the maximum likelihood method by Andrew Furness {ref. Furness, A.I. 2015. The Evolution of an annual Life Cycle in killifish: Adaptation to ephemeral aquatic environments through embryonic Diapause. Biological Reviews of the Cambridge Philosophical Society (Biol. Rev.)} with taxonomic notes on Rivulidae quotes: «Simpsonichthys myersi and Nematolebias whitei came out as well-supported sister taxa distinct from the otherwise monophyletic genus Simpsonichthys» which is not in line with Costa's original tree, because Simpsonichthys myersi has been erected in a separate genus Xenurolebias, along with Ophthalmolebias ; hence it would be more parsimonious not to consider Xenurolebias as a valid genus (in Killi-Data, it is conservatively kept as a valid subgenus of Simpsonichthys, only, pending further studies on Ophthalmolebias ; alternatively all species of Xenurolebias could be moved to Nematolebias, but then Ophthalmolebias is un-placed satisfactorily)]. 

[addendum (March 31. 2016), : a new publication with the first molecular global survey of the genus Simpsonichthys contradicts many of Costa's morphological and distributional analyses with splitting of the genus in several genera [ref.: Ponzetto, J.M., R. Britzke, D.T.B. Nielsen, P.P. Parise-Maltempi & A.L. Alves. 2016. Phylogenetic Relationships of Simpsonichthys subgenera (Cyprinodontiformes, Rivulidae), including a Proposal for a new genus. Zoologica Scripta, DOI: 10.1111/zsc.12159]… This new molecular study involving 29 named or un-named species is a major breakthrough in the systematics of Simpsonichthys, Xenurolebias, Ophthalmolebias, Spectrolebias and Hypsolebias, since the proposed splitting by Costa in 2010 of Simpsonichthys and levelling of Xenurolebias, Ophthalmolebias, Spectrolebias and Hypsolebias as full genera ; the present findings based on ATPase 8 and 6 gene sequences of 53 specimens, according to their authors, (quote) <the monophyletism of the genera Simpsonichthys, Spectrolebias, Hypsolebias and also of the flammeus group, as proposed by Costa could not be recovered and the relationship observed by morphological data within the Hypsolebias genus also could not be recovered in the present analysis< (end quote) ; the authors consider rather 2 clades ; my analysis of the work done by the present alternative Brasilian team (with Britsky, Nielsen, and Alves, i.e., independant from the other team with Costa and Amorim) and notably their molecular tree shows that components of Simpsonichthys and Spectrolebias are mixed and little can be derived, apart from synonymizing Spectrolebias into Simpsonichthys s.s., that Ophthalmolebias and the heloplites-group (which they name antenori-group) are related (within the antenori-heloplites group the species are extremely similar -also by male color pattern- and might not deserve a separate species rank for igneus, coamazonicus), that the remain bulk of previous Hypsolebias is related (flammeus-group, notatus-group, magnificus-group) and often very related, that several "species" which have been described in a given species group among those last 3 groups were wrongly allocated (e.g., ocellatus), that virgulatus and auratus are very related, with a population of virgulatus as paraphyletic, that the diagnoses of most names at the (sub)generic level in those lineages have to be written again since they are not valid anymore, and finally that Xenurolebias is confirmed as the basal group (however the authors do not include any component of Nematolebias in their analysis) ; besides the alternative Brasilian team does not formally propose changes in the nomenclature of Simpsonichthys and do not formally name as a new generic taxon (as a subgenus of Simpsonichthys) the un-named branch (Hypsolebias being paraphyletic and split into 2 lineages, the supergroup with flammeus-group, notatus-group, magnificus-group is left un-named), pending further studies (with more species… the total number of named species in the genus is 74, vs. 27 herein studied as named), and probably pending a new molecular study by Costa and Amorim (who up to now only studied a few species of the genus but are rumored to aiming the full genus).

In total a very important and sensitive newsletter !
Hopefully a boost to our community and a spur to speed up knowledge progress on our (beloved) fishes !

Take care and enjoy the scientific or aquaristic complexity of killifish !

Do not hesitate to ask questions for future Newsletters.

Visit frequently the website www.killi-data.org!

Thank you for your support over the years.

With my kindest regards.

Jean

Literature cited:
Costa, W.J.E.M. 2010. Historical Biogeography of cynolebiasine annual Killifishes inferred from Dispersal-Vicariance Analysis. Journ. Biogeography, 37: 1995-2004.

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