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Time and origin of cichlid colonization of the lower Congo rapids.

Schwarzer J, Misof B, Ifuta SN, Schliewen UK - PLoS ONE (2011)

Bottom Line: Based on a representative taxon sampling and well resolved phylogenetic hypotheses we demonstrate that a high level of riverine diversity originated in the lower Congo within about 5 mya, which is concordant with age estimates for the hydrological origin of the modern lower Congo River.A spatial genetic structure is present in all widely distributed lineages corresponding to a trisection of the lower Congo River into major biogeographic areas, each with locally endemic species assemblages.Beyond this we give for the first time a biologically estimated age for the origin of the lower Congo River rapids, one of the most extreme freshwater habitats on earth.

View Article: PubMed Central - PubMed

Affiliation: Bavarian State Collection of Zoology, München, Germany. j.schwarzer.zfmk@uni-bonn.de

ABSTRACT
Most freshwater diversity is arguably located in networks of rivers and streams, but, in contrast to lacustrine systems riverine radiations, are largely understudied. The extensive rapids of the lower Congo River is one of the few river stretches inhabited by a locally endemic cichlid species flock as well as several species pairs, for which we provide evidence that they have radiated in situ. We use more that 2,000 AFLP markers as well as multilocus sequence datasets to reconstruct their origin, phylogenetic history, as well as the timing of colonization and speciation of two Lower Congo cichlid genera, Steatocranus and Nanochromis. Based on a representative taxon sampling and well resolved phylogenetic hypotheses we demonstrate that a high level of riverine diversity originated in the lower Congo within about 5 mya, which is concordant with age estimates for the hydrological origin of the modern lower Congo River. A spatial genetic structure is present in all widely distributed lineages corresponding to a trisection of the lower Congo River into major biogeographic areas, each with locally endemic species assemblages. With the present study, we provide a phylogenetic framework for a complex system that may serve as a link between African riverine cichlid diversity and the megadiverse cichlid radiations of the East African lakes. Beyond this we give for the first time a biologically estimated age for the origin of the lower Congo River rapids, one of the most extreme freshwater habitats on earth.

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Chronogram showing divergence time estimates for Steatocranus and Nanochromis.The chronogram was calculated based on the ML tree. A partitioned Bayesian analysis implemented in BEAST was used to estimate divergence times. Time constraints were used following Schwarzer et al. [18]: A1 53–84 mya (uniform prior), published age estimate based on non-cichlid fossils [35] and O1 5.98 mya (lower bound), the age estimate for Oreochromis lorenzoi† [34]. The chronogram shows 95% credibility intervals (HPC, green bars). For nodes marked with letters, age estimates (95% HPC and mean heights) are given in Table 1. The asterisk marks the non-endemic lower Congo clade including N. parilus and N. teugelsi. Nanochromis parilus is distributed in the lower Congo but can also be found at Maluku upstream of Malebo pool. For simplification clear monophyletic groups were combined and shown as triangles.
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pone-0022380-g003: Chronogram showing divergence time estimates for Steatocranus and Nanochromis.The chronogram was calculated based on the ML tree. A partitioned Bayesian analysis implemented in BEAST was used to estimate divergence times. Time constraints were used following Schwarzer et al. [18]: A1 53–84 mya (uniform prior), published age estimate based on non-cichlid fossils [35] and O1 5.98 mya (lower bound), the age estimate for Oreochromis lorenzoi† [34]. The chronogram shows 95% credibility intervals (HPC, green bars). For nodes marked with letters, age estimates (95% HPC and mean heights) are given in Table 1. The asterisk marks the non-endemic lower Congo clade including N. parilus and N. teugelsi. Nanochromis parilus is distributed in the lower Congo but can also be found at Maluku upstream of Malebo pool. For simplification clear monophyletic groups were combined and shown as triangles.

Mentions: The age of the most recent common ancestor (MRCA) of Nanochromis is estimated at 8.36 (6.5 - 10.4) mya (Fig. 3, Node N). Median ages for clades containing lower Congo taxa (Node LC 1: N. splendens and N. consortus, Node LC 2*: N. parilus, N. teugelsi and N. nudiceps) are estimated at 2.67 (1.5–3.9) mya and 1.6 (0.7–2.5) mya. The two lacustrine species from the central Congo, Nanochromis wickleri and N. transvestitus (Node C1), diverged 4.4 (3–6.2) mya based on our data (Fig. 3, Table 1).


Time and origin of cichlid colonization of the lower Congo rapids.

Schwarzer J, Misof B, Ifuta SN, Schliewen UK - PLoS ONE (2011)

Chronogram showing divergence time estimates for Steatocranus and Nanochromis.The chronogram was calculated based on the ML tree. A partitioned Bayesian analysis implemented in BEAST was used to estimate divergence times. Time constraints were used following Schwarzer et al. [18]: A1 53–84 mya (uniform prior), published age estimate based on non-cichlid fossils [35] and O1 5.98 mya (lower bound), the age estimate for Oreochromis lorenzoi† [34]. The chronogram shows 95% credibility intervals (HPC, green bars). For nodes marked with letters, age estimates (95% HPC and mean heights) are given in Table 1. The asterisk marks the non-endemic lower Congo clade including N. parilus and N. teugelsi. Nanochromis parilus is distributed in the lower Congo but can also be found at Maluku upstream of Malebo pool. For simplification clear monophyletic groups were combined and shown as triangles.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3140524&req=5

pone-0022380-g003: Chronogram showing divergence time estimates for Steatocranus and Nanochromis.The chronogram was calculated based on the ML tree. A partitioned Bayesian analysis implemented in BEAST was used to estimate divergence times. Time constraints were used following Schwarzer et al. [18]: A1 53–84 mya (uniform prior), published age estimate based on non-cichlid fossils [35] and O1 5.98 mya (lower bound), the age estimate for Oreochromis lorenzoi† [34]. The chronogram shows 95% credibility intervals (HPC, green bars). For nodes marked with letters, age estimates (95% HPC and mean heights) are given in Table 1. The asterisk marks the non-endemic lower Congo clade including N. parilus and N. teugelsi. Nanochromis parilus is distributed in the lower Congo but can also be found at Maluku upstream of Malebo pool. For simplification clear monophyletic groups were combined and shown as triangles.
Mentions: The age of the most recent common ancestor (MRCA) of Nanochromis is estimated at 8.36 (6.5 - 10.4) mya (Fig. 3, Node N). Median ages for clades containing lower Congo taxa (Node LC 1: N. splendens and N. consortus, Node LC 2*: N. parilus, N. teugelsi and N. nudiceps) are estimated at 2.67 (1.5–3.9) mya and 1.6 (0.7–2.5) mya. The two lacustrine species from the central Congo, Nanochromis wickleri and N. transvestitus (Node C1), diverged 4.4 (3–6.2) mya based on our data (Fig. 3, Table 1).

Bottom Line: Based on a representative taxon sampling and well resolved phylogenetic hypotheses we demonstrate that a high level of riverine diversity originated in the lower Congo within about 5 mya, which is concordant with age estimates for the hydrological origin of the modern lower Congo River.A spatial genetic structure is present in all widely distributed lineages corresponding to a trisection of the lower Congo River into major biogeographic areas, each with locally endemic species assemblages.Beyond this we give for the first time a biologically estimated age for the origin of the lower Congo River rapids, one of the most extreme freshwater habitats on earth.

View Article: PubMed Central - PubMed

Affiliation: Bavarian State Collection of Zoology, München, Germany. j.schwarzer.zfmk@uni-bonn.de

ABSTRACT
Most freshwater diversity is arguably located in networks of rivers and streams, but, in contrast to lacustrine systems riverine radiations, are largely understudied. The extensive rapids of the lower Congo River is one of the few river stretches inhabited by a locally endemic cichlid species flock as well as several species pairs, for which we provide evidence that they have radiated in situ. We use more that 2,000 AFLP markers as well as multilocus sequence datasets to reconstruct their origin, phylogenetic history, as well as the timing of colonization and speciation of two Lower Congo cichlid genera, Steatocranus and Nanochromis. Based on a representative taxon sampling and well resolved phylogenetic hypotheses we demonstrate that a high level of riverine diversity originated in the lower Congo within about 5 mya, which is concordant with age estimates for the hydrological origin of the modern lower Congo River. A spatial genetic structure is present in all widely distributed lineages corresponding to a trisection of the lower Congo River into major biogeographic areas, each with locally endemic species assemblages. With the present study, we provide a phylogenetic framework for a complex system that may serve as a link between African riverine cichlid diversity and the megadiverse cichlid radiations of the East African lakes. Beyond this we give for the first time a biologically estimated age for the origin of the lower Congo River rapids, one of the most extreme freshwater habitats on earth.

Show MeSH
Related in: MedlinePlus