Tempo and rates of diversification in the South American cichlid genus Apistogramma (Teleostei: Perciformes: Cichlidae)

Abstract

Evaluating biodiversity and understanding the processes involved in diversification are noticeable conservation issues in fishes subject to large, sometimes illegal, ornamental trade purposes. Here, the diversity and evolutionary history of the Neotropical dwarf cichlid genus Apistogramma from several South American countries are investigated. Mitochondrial and nuclear markers are used to infer phylogenetic relationships between 31 genetically identified species. The monophyly of Apistogramma is suggested, and Apistogramma species are distributed into four clades, corresponding to three morphological lineages. Divergence times estimated with the Yule process and an uncorrelated lognormal clock dated the Apistogramma origin to the beginning of the Eocene (≈ 50 Myr) suggesting that diversification might be related to marine incursions. Our molecular dating also suggests that the Quaternary glacial cycles coincide with the phases leading to Apistogramma speciation. These past events did not influence diversification rates in the speciose genus Apistogramma, since diversification appeared low and constant through time. Further characterization of processes involved in recent Apistogramma diversity will be necessary.

Extensive Chromosomal Reorganization in Apistogramma Fishes (Cichlidae, Cichlinae) Fits the Complex Evolutionary Diversification of the Genus

“…The set of particular karyotype traits in Apistogramma provides a conspicuous phylogenetic signature, which supports the monophyly of the genus (Figure 6), as also supported by morphological and molecular data [4,23]. In addition to this basal fusion event, characteristic of the Apistogramma genus, a multitude of secondary and stochastic chromosomal changes, caused by pericentric inversions (or non-reciprocal translocations) and Robertsonian translocations, promoted additional numerical and structural karyotype changes.…”

“…In this group, the reduced karyotypes (2n ≤ 46) with a high number of bi-armed chromosomes (Figure 5) largely contrast with those found in the other Apistogrammines (2n = 48). Such a low 2n value originated from one ancestral fusion event, at the onset of the diversification of the genus by around 55 Mya [23].…”

“…Multiple lines of evidence indicate that several Apistogramma complexes underwent rapid speciation processes or are undergoing a dynamic process of diversification [23]. In the incipient speciation context, the genetic cohesion of groups is insured by prezygotic reproductive barriers [63].…”

“…Due to its high endemism, sympatry levels, and species diversity, Apistogramma has several provisional taxonomic groups, whose phylogenetic relationships are largely uncertain [4,23]. Its morphological taxonomy is particularly difficult, based on many cases in cryptic differences and body color patterns [4,17].…”

“…Its morphological taxonomy is particularly difficult, based on many cases in cryptic differences and body color patterns [4,17]. Up to now, phylogenetic inferences based on nuclear and mitochondrial markers have identified four Apistogramma clades in three main morphological groups, namely the steindachneri , agassizii , and regani lineages [23], reinforcing the difficulties in using the morphospecies concept to establish evolutionary relationships.…”