ABSTRACT
Two hybrids between the monkey goby Neogobius fluviatilis and the round goby Neogobius melanostomus from the Rhine River were identified by genotyping and morphological comparison. These are the first records of goby-hybrids outside the parent species' native ranges worldwide.
Subject(s)
Hybridization, Genetic , Introduced Species , Perciformes/physiology , Amplified Fragment Length Polymorphism Analysis , Animals , Genotype , Perciformes/genetics , Phylogeny , Population Dynamics , Sequence Analysis, DNAABSTRACT
Hybridization in animals is a much more common phenomenon as previously thought and may have profound implications for speciation research. The cichlid genus Steatocranus (Teleostei: Cichlidae), a close relative to members of the East African cichlid radiations, radiated under riverine conditions in the lower Congo rapids and produced a small species flock. Previous phylogenetic analyses suggested that hybridization occurred and contributed to speciation in this genus. A re-analysis of an already published 2000 loci-AFLP data set explicitly testing for patterns of ancient gene flow provided strong evidence for a highly reticulate phylogenetic history of the genus. We provide, to our knowledge, the first example of a complex reticulate network in vertebrates, including multiple closely related species connected through ancient as well as recent gene flow. In this context, the limited validity of strictly bifurcating tree hypotheses as a phylogenetic basis for hypothesis testing in evolutionary biology is discussed.
Subject(s)
Cichlids/genetics , Genetic Speciation , Hybridization, Genetic , Phylogeny , Amplified Fragment Length Polymorphism Analysis , Animals , Cichlids/classification , Congo , Gene Flow , Genomics , Polymorphism, Restriction Fragment Length , Principal Component Analysis , RiversABSTRACT
Sympatric speciation is difficult to demonstrate in nature and remains a hotly debated issue. Barluenga et al. present a case of putative sympatric speciation for two cichlid species in the Nicaraguan crater lake Apoyo, but they overlook or reinterpret some key published information on the system. Although sympatric speciation is possible in theory, we show here that, when this information is taken into account, the results of Barluenga et al. do not provide conclusive evidence for sympatric speciation: this is because the null hypothesis of multiple invasion with introgression cannot be rejected.
Subject(s)
Biological Evolution , Cichlids/genetics , Cichlids/physiology , Genetic Speciation , Models, Biological , Animals , Cichlids/classification , DNA, Mitochondrial/genetics , Fresh Water , Haplotypes/genetics , Nicaragua , Phylogeny , Reproducibility of Results , Species SpecificityABSTRACT
The existence of sympatric speciation--that populations diverge into species in the absence of physical or ecological barriers--is controversial. The East African Great Lakes harbour hundreds of cichlid species representing only a few monophyletic lineages, although palaeolimnological evidence and local restrictions on species distribution suggest that speciation in these lakes could have been allopatric. The case for sympatry in restricted areas of Lakes Malawi and Tanganyika is stronger but not unassailable. A better case might be made for cichlid species flocks in small, ecologically monotonous crater lakes. Here we present a mitochondrial DNA analysis of cichlid species flocks endemic to two such lakes in Cameroon. The results suggest that the flocks in each lake are monophyletic: the implication being that each lake was colonized once only, the size and shape of each lake being such that subsequent diversification would have been sympatric.
