Abstract
BackgroundCichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments. To examine whether ecological opportunity increased diversification (speciation minus extinction) early in a species-rich cichlid radiation, we determined if Heroine cichlids experienced a burst of diversification following their invasion of Central America.ResultsWe first reconstructed the Heroine phylogeny and determined the basal node to use as the root of Central American Heroine diversification. We then examined the influence of incomplete taxon sampling on this group's diversification patterns. First, we added missing species randomly to the phylogeny and assessed deviations from a constant rate of lineage accumulation. Using a range of species numbers, we failed to recover significant deviations from a pure-birth process and found little support for an early burst of diversification. Then, we examined patterns of lineage accumulation as nodes were increasingly truncated. We assumed that as we removed more recently diverged lineages that sampling would become more complete thereby increasing the power to detect deviations from a pure-birth model. However, truncation of nodes provided even less support for an early burst of diversification.ConclusionsContrary to expectations, our analyses suggest Heroine cichlids did not undergo a burst of diversification when they invaded from South America. Throughout their history in Central America, Heroine cichlids appear to have diversified at a constant rate.
Highlights
Cichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments
To examine the hypothesis that novel ecological opportunity facilitates an increase in cichlid diversification rate, we determined whether Heroine cichlids underwent a burst of diversification following their invasion of Central America
Phylogeny Reconstruction The phylogenetic relationships recovered with the 17 new cytochrome b sequences (Table 1) analyzed in a Archocentrus spinosissimus Cichlasoma beani Cryptoheros chetumalensis Cryptoheros cutteri Cryptoheros spilurus Paraneetroplus gibbiceps Parachromis friedrichsthalii Parachromis managuensis Parachromis motaguensis Thorichthys affinis Thorichthys aureus Thorichthys meeki Thorichthys pasionis Thorichthys socolofi Vieja bifasciata Vieja hartwegi Vieja maculicauda
Summary
Cichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments. To examine whether ecological opportunity increased diversification (speciation minus extinction) early in a species-rich cichlid radiation, we determined if Heroine cichlids experienced a burst of diversification following their invasion of Central America. The absence of predators or competitors in these three massive, relatively old lakes could have been the key to the rapid filling of niches with the hundreds of endemic cichlid species that occur sympatrically in each lake It is generally unclear how important the invasion of novel habitats is to cichlid diversification [9] and if cichlids presented with novel ecological circumstances frequently experience a burst and subsequent slowdown in cladogenesis. To examine the hypothesis that novel ecological opportunity facilitates an increase in cichlid diversification rate, we determined whether Heroine cichlids underwent a burst of diversification following their invasion of Central America
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