Monophyly and Phylogenetic Relationships of the Neotropical Annual Fish Genera Austrolebias and Megalebias (Cyprinodontiformes: Rivulidae)
Phylogenetic relationships among taxa of the annual fish subtribe Cynolebiatina are examined, based on 57 morphological characters in 29 terminal taxa, including two basal species of the well-supported monophyletic genus Cynolebias Steindachner, 19 valid species of Austrolebias Costa, and all five valid species of Megalebias Costa. A clade comprising Austrolebias and Megalebias is strongly supported (bootstrap value 96%) and defined by five nonhomoplastic synapomorphies: deep urohyal, long cleithrum, dorsal and anal fins of male short and rounded, frontal squamation F-patterned, and a transverse supraorbital bar. Monophyly of Megalebias is supported (bootstrap value 98%) by 12 synapomorphies, four unambiguous: reduced basihyal, anteriorly expanded anterolateral tip of lateral process of sphenotic, curved lacrimal, and posteroventrally directed suborbital stripe. Monophyly of Austrolebias (bootstrap value 96%) is corroborated by a reduced basihyal ossification, a laterally expanded basihyal cartilage, an anteriorly positioned dorsal fin of male, and a spotted color pattern in female. Evidence supporting intergeneric and intrageneric relationships is discussed. Relações filogenéticas entre taxa da subtribo de peixes anuais Cynolebiatina são examinadas, com base em 57 caracteres morfológicos em 29 taxa terminais, incluindo duas espécies basais do bem corroborado gênero monofilético Cynolebias, 19 espécies válidas de Austrolebias Costa, e todas as cinco espécies válidas de Megalebias Costa. Um clado compreendendo Austrolebias e Megalebias é fortemente sustentado (valor de bootstrap 96%), e definido por cinco sinapomorfias não homoplásticas: uro-hial alto, cleitro longo, nadadeiras dorsal e anal de macho curtas e arredondadas, escamação frontal em padrão F, e uma barra supraorbital transversal. Monofiletismo de Megalebias é sustentado (valor de bootstrap 98%) por 12 sinapomorfias, quatro não ambíguas: basi-hial reduzido, ponta antero-lateral de esfenótico expandida anteriormente, lacrimal encurvado, e faixa suborbital direcionada postero-ventralmente. Monofiletismo de Austrolebias (valor de bootstrap 96%) é corroborado pela reduzida ossificação do basi-hial, expansão lateral de cartilagem basi-hial, nadadeira dorsal de macho posicionada anteriormente, e padrão de colorido maculado em fêmea. Evidências sustentando relações inter e intra-genéricas são discutidas.Abstract
Strict consensus of two equally parsimonious shortest trees (L = 124; CI = 0.65; RI = 0.84) inferred from 57 characters for 29 species. Letters left of branches represent clades of the strict consensus tree. The set of numbers left are unambiguously placed synapomorphies, followed by the number of characters supporting the node; numbers right of branches are decay indices above, and bootstrap values below. List of apomorphies by node as in Appendix 2
Left jaws, suspensorium and opercular series, lateral view. (A) Austrolebias carvalhoi, (B) Megalebias elongatus. Stipple indicate bone, small circles cartilage
Basihyal, ventral view, and right hyoid bar, medial view, of (A) Austrolebias vandenbergi, (B) Austrolebias alexandri, (C) Megalebias elongatus. Dots indicate bone, small circles cartilage
Neurocranium, ventral view, of (A) Austrolebias alexandri, (B) Megalebias monstrosus. Stipple indicate bone, small circles cartilage
Shoulder girdle, left side, lateral view, of Austrolebias alexandri. Postcleithrum 3 not represented. Stipple indicate bone, small circles cartilage
Phylogenies for 13 species of Austrolebias and Megalebias based on mitochondrial cytochrome b data according to García et al. (2000). (A) Neighbor-joining analysis, (B) unweighted maximum parsimony analysis, (C) weighted maximum parsimony analysis
Urohyal, left lateral view of (A) Cynolebias griseus, (B) Austrolebias viarius, (C) Megalebias cheradophilus, (D) Megalebias wolterstorffi, (E) Megalebias monstrosus