64 (1): 23 – 33 © Senckenberg Gesellschaft für Naturforschung, 2014. 16.5.2014 A new genus of miniature cynolebiasine from the Atlantic Forest and alternative biogeographical explanations for seasonal killifish distribution patterns in South America (Cyprinodontiformes: Rivulidae) Wilson J. E. M. Costa Laboratório de Sistemática e Evolução de Peixes Teleósteos, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Caixa Postal 68049, CEP 21944 – 970, Rio de Janeiro, Brasil; wcosta(at)acd.ufrj.br Accepted 21.ii.2014. Published online at www.senckenberg.de/vertebrate-zoology on 30.iv.2014. Abstract The analysis of 78 morphological characters for 16 species representing all the lineages of the tribe Cynopoecilini and three out-groups, indicates that the incertae sedis miniature species ‘Leptolebias’ leitaoi Cruz & Peixoto is the sister group of a clade comprising the genera Leptolebias, Campellolebias, and Cynopoecilus, consequently recognised as the only member of a new genus. Mucurilebias gen. nov. is diagnosed by seven autapomorphies: eye occupying great part of head side, low number of caudal-fin rays (21), distal portion of epural much broader than distal portion of parhypural, an oblique red bar through opercle in both sexes, isthmus bright red in males, a white stripe on the distal margin of the dorsal fin in males, and a red stripe on the distal margin of the anal fin in males.Mucurilebias leitaoi is an endangered seasonal species endemic to the Mucuri river basin. The biogeographical analysis of genera of the subfamily Cynolebiasinae using a dispersal-vicariance, event-based parsimony approach indicates that distribution of South American killifishes may be broadly shaped by dispersal events. The analysis supports south-eastern Brazilian coastal plains as the centre of dispersal for cynolebiasine killifishes. Alternative biogeographical explanations are compared and possible dispersal routes and means of dispersal are discussed. Key words Atlantic Forest, Centre of origin, Dispersal, Mucuri river, Vicariance. Introduction The tribes Cynolebiasini and Cynopoecilini are well- 1952, and Notholebias COSTA, 2008, 2010). In addition, corroborated clades of killifishes, belonging to the sea- COSTA (2008) recognised an incertae sedis cynopo- sonal killifish subfamily Cynolebiasinae, with the Cy no- eciline species, ‘Leptolebias’ leitaoi (CRUZ & PEIXOTO, lebiasini comprising seven genera (Austrolebias COSTA, 1991) that could not be properly placed in any genera. 1998, Cynolebias STEINDACHNER, 1877, Hypsolebias ‘Leptolebias’ leitaoi is known only from the floodplains COSTA, 2006, Nematolebias COSTA, 1998, Simpsonichthys of the Mucuri river, an area about 500 km north from CARVALHO, 1959, Spectrolebias COSTA & NIELSEN, 1997, the geographically nearest cynopoecilines (COSTA, 2008). Xenurolebias COSTA, 2006) and the Cynopoecilini com- All the known specimens of ‘L’. leitaoi were collected prising four genera (Campellolebias VAZ-FERREIRA & in 1988, within a cacao farm close to the Mucuri river SIERRA, Cynopoecilus REGAN, 1912, Leptolebias MYERS, bank (CRUZ & PEIXOTO, 1991). The whole region was ISSN 1864-5755 23 W.J.E.M. Costa: A new genus of miniature cynolebiasine from the Atlantic Forest subsequently highly modified by a cellulose industry and stained for bone and cartilage according to TAYLOR & great part of the original forest was substituted by cattle VAN DYKE (1985), deposited in the Instituto de Biologia, pastures few years after the discovery of ‘L’. leitaoi. As a Universidade Federal do Rio de Janeiro, Rio de Janeiro; consequence, the species was never found again (COSTA, characters examined included data on squamation and 1995, 2009). Since the type series was lost, determination contact organs taken just after fixation in formalin, and of the phylogenetic position of ‘L’. leitaoi depends on the data on osteological characters taken after clearing and single specimen of the species presently known to be pre- staining procedures. Data on colour patterns were taken served in a fish collection (COSTA, 2008). This specimen from colour photos of live topotypes, and on reproduc- was collected with the type series, kept in aquaria and tive behaviour characters from direct observation of one fixed, cleared and stained just after dying. Consequently, male and one female kept in aquarium, not preserved. some diagnostic characters could not be examined and The phylogenetic analysis was conducted using the same the phylogenetic position of the species was not evalu- data matrix provided in COSTA (2008), just inserting ‘L’. ated, preventing a tentative generic placement (COSTA, leitaoi as a terminal taxon (Appendix 1); characters were 2008). However, after six years, ‘L’. leitaoi is still an modified to follow SERENO’s (2007) proposal for for- incertae sedis taxon, which is a undesirable situation mulating character statements (Appendix 2); characters since ‘L’. leitaoi is a focal species within an important of anal-fin musculature and neuromast patterns, not re- Brazilian governmental program to conserve killifishes corded for ‘L’. leitaoi, were coded as a question mark for threatened with extinction (ICMBIO, 2013). To solve this this species in the data matrix. A Maximum Parsimony problem, characters of that specimen are re-analysed in analysis was performed with TNT 1.1 (GOLOBOFF et al., order to find the best phylogenetic hypothesis for the po- 2008), using the ‘traditional’ search and setting random sition of ‘L’. leitaoi among cynopoecilines, which then is taxon-addition replicates to 10, tree bisection-reconnec- used to provide a conventional generic placement. tion branch swapping, multitrees in effect, collapsing The great distance between the only record of ‘L’. branches of zero-length, characters equally weighted, leitaoi and other members of the tribe Cynopoecilini, and a maximum of 100,000 trees saved in each replicate. about 500 km, is not an uncommon pattern in the Atlantic Branch support was assessed by bootstrap analysis, us- Forest, similar to distributional gaps recorded for other ing a heuristic search with 1,000 replicates and the same cynolebiasine killifishes of the Atlantic Forest: 1) all spe- settings used in the MP search, but saving a maximum of cies of the genus Ophthalmolebias, except O. constan- 1,000 trees in each random taxon-addition replicate. ciae (MYERS, 1942), occurs in an area of north-eastern Brazil between the Almada and Jequitinhonha river ba- Biogeography. Biogeographical distribution patterns sins, whereas O. constanciae is endemic to an area 800 of the subfamily Cynolebiasinae is analysed under a km distant, in south-eastern Brazil (COSTA, 2007); 2) the dispersal-vicariance, event-based parsimony approach sister species L. aureoguttatus (CRUZ, 1974) and L. itan- (DIVA) (RONQUIST, 1996, 1997). The search for the op- haensis COSTA, 2008 from southern Brazil are separated timal historical reconstruction was performed using the from other congeners in south-eastern Brazil by a 400 computer program DIVA 1.2 (RONQUIST, 1996). The phy- km gap (COSTA, 2008); 3) the genus Xenurolebias from lo genetic tree used in the analysis was a summary of our eastern Brazil is separated from its sister group genus present knowledge on cynolebiasine relationships, using Nematolebias from south-eastern Brazil by a 400 km gap. genera as terminal taxa. This tree follows the phylogeny These broad gaps may be explained both by large-scale of the Cynopoecilini as herein proposed (Fig. 1) and the extinction or long-distance dispersal, since incomplete phylogeny of the Cynolebiasini as proposed by COSTA sampling becomes improbable after over 200 collect- (2010), except for the sister group relationship between ing trips in about 30 years (June 1993 – February 2014), Nematolebias and Xenurolebias, as strongly supported directed to killifish habitats of all parts of the Atlantic in an unpublished phylogenetic study using nuclear and Forest. COSTA (2010) analysed the biogeographical pat- mitochondrial genes by AMORIM and COSTA. The analysis terns of the Cynolebiasini, concluding that they are pre- also included the ancestral distribution of the most basal dominantly derived from old vicariance events. On the rivulid genus Kryptolebias COSTA to follow RONQUIST’s basis of a more inclusive analysis to comprise all genera (1996) recommendation to include distribution data for of the Cynolebiasinae, alternative biogeographical his- sister groups to reduce the tendency of the root node torical explanations are here compared. distribution to include most of the areas occupied by the terminals. The analysis included 14 terminal taxa (Fig. 2), representing all the genera of the subfamily Cynolebiasinae and Kryptolebias. The exact search of Material and methods DIVA was used both without reducing the number of an- cestral areas and restricting them to two areas through the maxareas option of the optimize command in DIVA. Areas of endemism were delimited according to the dis- Phylogeny. The phylogenetic position of ‘L’. leitaoi tribution of monophyletic groups of the Cynolebiasinae was inferred through examination of a single topotype and other killifishes. In order to detect potential disper- specimen, UFRJ 171, male, 22 mm SL, cleared and sal routes, areas of endemism (Fig. 3) were represented 24 VERTEBRATE ZOOLOGY — 64 (1) 2014 Fig. 1. Most parsimonious phylogeny among 13 species of the Cy- no poecilini. Out-groups not depicted. Numbers above branches are bootstrap values. Fig. 2. Phylogenetic relationships among genera