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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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Potential colonization scenarios for Steatocranus and Nanochromis.Potential colonization scenarios are shown separately for both genera. The red arrows indicate potential dispersal routes of Steatocranus and Nanochromis precursors. Non-lower Congo taxa are written in black. Current distribution ranges of the major lower Congo phylogenetic clades (see Fig. 2) are represented by different kinds of dotted lines (see figure legend). Clade 1 (Steatocranus): S. cf. casuarius species pair, clade 2 (Steatocranus): S. cf. tinanti/ S. cf. gibbiceps/ S. glaber and S. mpozoensis, clade1 (Nanochromis): N. splendens and N. consortus, and clade 2 (Nanochromis): N. parilus. The trisection of the lower Congo is shown in combination with sampling sites (indicated by red dots) along the lower Congo. The upper part of the Congo River is presented highly simplified for a better understanding.
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pone-0022380-g004: Potential colonization scenarios for Steatocranus and Nanochromis.Potential colonization scenarios are shown separately for both genera. The red arrows indicate potential dispersal routes of Steatocranus and Nanochromis precursors. Non-lower Congo taxa are written in black. Current distribution ranges of the major lower Congo phylogenetic clades (see Fig. 2) are represented by different kinds of dotted lines (see figure legend). Clade 1 (Steatocranus): S. cf. casuarius species pair, clade 2 (Steatocranus): S. cf. tinanti/ S. cf. gibbiceps/ S. glaber and S. mpozoensis, clade1 (Nanochromis): N. splendens and N. consortus, and clade 2 (Nanochromis): N. parilus. The trisection of the lower Congo is shown in combination with sampling sites (indicated by red dots) along the lower Congo. The upper part of the Congo River is presented highly simplified for a better understanding.

Mentions: Apparent cyto-nuclear tree incongruence hampers the reconstruction of some colonization patterns in both genera (Fig. 2). In Steatocranus a well supported relationship is identified between the “North” clade species and the lower Congo S. cf. casuarius clade (including S. sp. “Maluku” and S. sp. “dwarf”), indicating that the ancestors of present day S. cf. casuarius colonized the lower Congo (at about 3.23 mya) from Northern populations distributed presently in the upper Congo near Kisangani, downstream of Mbandaka and in northern Congo tributaries (Ubangi and Sangha Rivers). The phylogenetic signal concerning the position of the Southern populations is ambiguous. Two alternative topologies are most frequently found among the bootstrap replicates (Fig. S1), supporting two slightly different colonization scenarios with regard to the lower Congo: In the first scenario, a simultaneous dispersal of southern precursors into the lower Congo as well as into the northern tributaries took place, i.e. seeding both the present day S. cf. tinanti/S. mpozoensis/S. glaber/S. cf. gibbiceps clade (ca.4.48 mya, Fig. 3) and the northern clade (BS = 47, Fig. S1). Subsequently a secondary colonization wave from northern tributary species and from the Congo mainstream then founded the younger lower Congo Steatocranus cf. casuarius clade (ca. 3.23 mya, Fig. 3). In the second scenario, an early vicariance event separated already existing southern and northern tributary populations which then founded the S. cf. tinanti/S. mpozoensis/S. glaber/S. cf. gibbiceps clade (BS = 44, Fig. S1) from the South and later the Steatocranus cf. casuarius clade from the North (Fig. 4).


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

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

Potential colonization scenarios for Steatocranus and Nanochromis.Potential colonization scenarios are shown separately for both genera. The red arrows indicate potential dispersal routes of Steatocranus and Nanochromis precursors. Non-lower Congo taxa are written in black. Current distribution ranges of the major lower Congo phylogenetic clades (see Fig. 2) are represented by different kinds of dotted lines (see figure legend). Clade 1 (Steatocranus): S. cf. casuarius species pair, clade 2 (Steatocranus): S. cf. tinanti/ S. cf. gibbiceps/ S. glaber and S. mpozoensis, clade1 (Nanochromis): N. splendens and N. consortus, and clade 2 (Nanochromis): N. parilus. The trisection of the lower Congo is shown in combination with sampling sites (indicated by red dots) along the lower Congo. The upper part of the Congo River is presented highly simplified for a better understanding.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0022380-g004: Potential colonization scenarios for Steatocranus and Nanochromis.Potential colonization scenarios are shown separately for both genera. The red arrows indicate potential dispersal routes of Steatocranus and Nanochromis precursors. Non-lower Congo taxa are written in black. Current distribution ranges of the major lower Congo phylogenetic clades (see Fig. 2) are represented by different kinds of dotted lines (see figure legend). Clade 1 (Steatocranus): S. cf. casuarius species pair, clade 2 (Steatocranus): S. cf. tinanti/ S. cf. gibbiceps/ S. glaber and S. mpozoensis, clade1 (Nanochromis): N. splendens and N. consortus, and clade 2 (Nanochromis): N. parilus. The trisection of the lower Congo is shown in combination with sampling sites (indicated by red dots) along the lower Congo. The upper part of the Congo River is presented highly simplified for a better understanding.
Mentions: Apparent cyto-nuclear tree incongruence hampers the reconstruction of some colonization patterns in both genera (Fig. 2). In Steatocranus a well supported relationship is identified between the “North” clade species and the lower Congo S. cf. casuarius clade (including S. sp. “Maluku” and S. sp. “dwarf”), indicating that the ancestors of present day S. cf. casuarius colonized the lower Congo (at about 3.23 mya) from Northern populations distributed presently in the upper Congo near Kisangani, downstream of Mbandaka and in northern Congo tributaries (Ubangi and Sangha Rivers). The phylogenetic signal concerning the position of the Southern populations is ambiguous. Two alternative topologies are most frequently found among the bootstrap replicates (Fig. S1), supporting two slightly different colonization scenarios with regard to the lower Congo: In the first scenario, a simultaneous dispersal of southern precursors into the lower Congo as well as into the northern tributaries took place, i.e. seeding both the present day S. cf. tinanti/S. mpozoensis/S. glaber/S. cf. gibbiceps clade (ca.4.48 mya, Fig. 3) and the northern clade (BS = 47, Fig. S1). Subsequently a secondary colonization wave from northern tributary species and from the Congo mainstream then founded the younger lower Congo Steatocranus cf. casuarius clade (ca. 3.23 mya, Fig. 3). In the second scenario, an early vicariance event separated already existing southern and northern tributary populations which then founded the S. cf. tinanti/S. mpozoensis/S. glaber/S. cf. gibbiceps clade (BS = 44, Fig. S1) from the South and later the Steatocranus cf. casuarius clade from the North (Fig. 4).

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