Tuesday, April 5, 2016

[Ichthyology • 2016] Diversity and Evolution of the Middle American Cichlid Fishes (Teleostei: Cichlidae) with Revised Classification

Fig. 3. Phylogenetic relationships of Middle American heroine cichlids using the 903 terminal taxon population-level sampling analysis based on mitochondrial DNA (mtDNA: cyt b, ND4, COI, 16S) and nuclear DNA (nDNA: S7i1, RAG1, RAG2). The population-level information is based on the cytb marker only, while the skeleton of the tree is based on the multilocus species-level sampling dataset (fig. 2). The first part of the figure shows relationships within herichthyines, the second part within the amphilophines and astatheroines (both highlighted in the inset tree). Other parts of the tree are omitted (see Supplementary material 2). The tree shown is a 50% majority-rule consensus tree obtained with Bayesian inference analysed as five data partitions (see figs. 1‒2 and Methods). Support values (PP) are shown to the right of the nodes. Putative new species are shown in green. Conflicts with existing classification and conflicts between nDNA and mtDNA are shown in red (cf. figs. 1 & 4). Weakly supported nodes are in grey colour. The scale bar represents the average number of substitutions per site. Each species is also shown by a photograph of a specimen in breeding coloration accompanied by a two-letter species-name acronym. See Supplementary material 1 for the specimen sampling of the Middle American species.

We present a taxonomically complete and topologically robust molecular phylogeny of the Middle American heroine cichlids based on which we review their diversity and genus-level systematics. In order to ascertain the diversity of the group and its phylogeny we have used three nested taxon sampling analyses of the concatenated nDNA/mtDNA datasets and additionally to these analyses we present a summary of the results of a new Next Generation Sequencing-generated nuclear phylogeny based on a data set of ~ 140,000 informative characters. The NGS ddRAD phylogeny has a species-level sampling covering virtually all species (including the enigmatic Cichlasoma microlepis Dahl, 1960) with multiple sequenced specimens per species. Based on our results the Middle American heroine cichlids are made up of three main clades. The three clades (the herichthyines, the amphilophines, and the astatheroines) are however not each other sister groups since they are interspersed with South American (Australoheros, Caquetaia, Chocoheros, Heroina, Mesoheros) and Antillean (Nandopsis) genera and they represent probably two separate colonization events of Middle America from South America, probably via the Antilles. Our study reveals many cases of cytonuclear discordance and/or introgressive hybridization both at the genus and deeper levels stressing the importance to study the nuclear and mitochondrial phylogenetic signals independently and not solely in concatenated analyses.

We have found that a great majority of morphological characters are ecologically correlated and that they form only a limited number of functionally-determined combinations – i.e. ecomorphs. We have found five main cranial ecomorphs but only two postcranial ecomorphs (the lotic and lentic ecomorphs, plus the undifferentiated ancestral character combination). The cranial and postcranial ecomorphs are not combined completely randomly having produced thirteen modular whole-body ecomorphs. Both the cranial and postcranial ecomorphs, and even their combinations, have evolved repeatedly in the Middle American cichlids in the same habitats both in sympatry as well as in allopatry. Our analyses of the diversity of Middle American cichlid clade support the existence of 31 genera in Middle America (plus six in South America and one in the Greater Antilles) as separate evolutionary lineages occupying separate adaptive zones. Nine new genera are described here for species and species groups that have lacked a genus level name to this day or were associated with other unrelated genera. We also review the species level diversity based on the mtDNA cytb gene population-level analysis. Furthermore, we provide a new biogeographical analysis of the group which explains their evolutionary history and demonstrates that biogeography is a much better indicator of evolutionary relationships in this fish group than are most morphological characters due to their ecological correlation.

Key words: Adaptive radiation, Central America, cytonuclear discordance, introgressive hybridization, freshwater fishes, new genera, putative new species.

New genus and new species:

Chocoheros gen. nov. Říčan & Piálek, 2016
Type species: Cichlasoma microlepis Dahl, 1960

Chortiheros gen. nov. Říčan & Dragová, 2016
Type species: Theraps wesseli Miller, 1996

Cribroheros gen. nov. Říčan & Piálek, 2016
Type species: Heros rostratus Gill in Gill & Bransford, 1877

Darienheros gen. nov. Říčan & Novák, 2016
Type species: Cichlasoma calobrense Meek & Hildebrand, 1913

Isthmoheros gen. nov. Říčan & Novák, 2016
Type species: Cichlasoma tuyrense Meek & Hildebrand, 1913

Kronoheros gen. nov. Říčan & Piálek, 2016
Type species: Cichlasoma umbriferum Meek & Hildebrand, 1913

Mayaheros gen. nov. Říčan & Piálek, 2016
Type species: Heros urophthalmus Günther, 1862

Talamancaheros gen. nov. Říčan & Novák, 2016
Type species: Heros sieboldii Kner, 1863

Wajpamheros gen. nov. Říčan & Piálek, 2016
Type species: Theraps nourissati Allgayer, 1989

Oldřich Říčan, Lubomír Piálek, Klára Dragová and Jindřich Novák. 2016. Diversity and Evolution of the Middle American Cichlid Fishes (Teleostei: Cichlidae) with Revised Classification. Vertebrate Zoology. 66(1): 1-102.