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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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Location map of sampling sites.Circles correspond to Steatocranus and squares to Nanochromis sampling sites. The filled circle and square mark the location of unsamples species. The half filled circle indicate that the species was included in the sequence but not in the AFLP analysis. Letters correspond to non-lower-Congo species distributions: (a) Nanochromis parilus, (b) N. teugelsi, (c) N. nudiceps, (d) N. transvestitus, N. wickleri, (e) N. sp. “Mbandaka”, (f) N. sp. “Ndongo”, (A) S. sp. “dwarf”, S. sp. “bulky head”, S. bleheri, S. sp. “Maluku” (B) S. sp. “red eye”, (C) S. sp. “Kwilu” (D) S. rouxi, (E) S. sp. “Mbandaka”, S. sp “Maluku” (F) S. ubanguiensis, (G) S. sp. “Kisangani” and (H) S. sp. “Nki. Sampling locations along the lower Congo are presented in larger scale and marked by red circles. Numbers along the lower Congo correspond to the sample site legend in the lower right side. White background highlights the territory of the Democratic Republic of Congo.
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pone-0022380-g001: Location map of sampling sites.Circles correspond to Steatocranus and squares to Nanochromis sampling sites. The filled circle and square mark the location of unsamples species. The half filled circle indicate that the species was included in the sequence but not in the AFLP analysis. Letters correspond to non-lower-Congo species distributions: (a) Nanochromis parilus, (b) N. teugelsi, (c) N. nudiceps, (d) N. transvestitus, N. wickleri, (e) N. sp. “Mbandaka”, (f) N. sp. “Ndongo”, (A) S. sp. “dwarf”, S. sp. “bulky head”, S. bleheri, S. sp. “Maluku” (B) S. sp. “red eye”, (C) S. sp. “Kwilu” (D) S. rouxi, (E) S. sp. “Mbandaka”, S. sp “Maluku” (F) S. ubanguiensis, (G) S. sp. “Kisangani” and (H) S. sp. “Nki. Sampling locations along the lower Congo are presented in larger scale and marked by red circles. Numbers along the lower Congo correspond to the sample site legend in the lower right side. White background highlights the territory of the Democratic Republic of Congo.

Mentions: Species of the two lower Congo cichlid genera Steatocranus and Nanochromis show a scattered distribution of few predominantly allopatric species within the Congo basin (Fig. 1) with a remarkable peak of recently discovered species richness (described and undescribed) endemic to the lower Congo (N (Steatocranus)  = 10, N (Nanochromis)  = 3). Apart from the lower Congo, Nanochromis species are distributed mainly south to the central Congo basin in Lakes Tumba and Mai Ndombe and adjacent rivers (N. wickleri and N. transvestitus, N. nudiceps) or in the Kasai River drainage (N. teugelsi). One undescribed species (N. sp. “Ndongo”) has recently been discovered in rivers Ngoko and Sangha (pers. obs.), both forming a northwestern Congo tributary, and another yet undescribed species (N. sp. “Mbandaka”) is known from the Congo mainstream around Mbandaka [16]. Nanochromis parilus is distributed in the lower Congo but also above Malebo Pool e.g. at Maluku. Steatocranus species occurring outside the lower Congo are distributed either in northern tributaries (S. sp. “Nki”, S. ubanguiensis and S. sp. “Lefini” from Ngoko, Ubangi and Lefini rivers) or south to the Congo mainstream (S. rouxi, S. sp. “red eye”, S. sp. “Kwilu” from Kasai, Kwango and Kwilu rivers), or in the Congo proper (S. sp. “dwarf”, S. sp. “bulky head”, S. bleheri, S. sp. “Maluku”, S. sp. “Mbandaka” and S. sp. “Kisangani” from around Malebo Pool, Maluku, Mbandaka and Kisangani). The haplotilapiine genus Steatocranus consists of rheophilic species whereas within the chromidotilapiine genus Nanochromis adaptations to high current are less obvious [4], [17], [18]. Habitat preferences differ between the mainly rock-dwelling Steatocranus and the more sand-dwelling Nanochromis (pers. obs.). Lower Congo Steatocranus are characterized by divergence in trophic traits indicating ecologically differentiated trait utility, i.e. dentition used for algae scraping (“aufwuchs feeding”), molluscivory and drift feeders ([4], pers. obs.). Recent surveys by different teams along multiple locations along the Lower Congo discovered that the species distribution of cichlids along the Lower Congo is not homogeneous. Both Nanochromis and Steatocranus species can be confined to short rapids stretches, and partially occur syntopically with close congenerics, whereas other species are less restricted in their distribution and/or represent the single genus representative in a selected rapids stretch.


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

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

Location map of sampling sites.Circles correspond to Steatocranus and squares to Nanochromis sampling sites. The filled circle and square mark the location of unsamples species. The half filled circle indicate that the species was included in the sequence but not in the AFLP analysis. Letters correspond to non-lower-Congo species distributions: (a) Nanochromis parilus, (b) N. teugelsi, (c) N. nudiceps, (d) N. transvestitus, N. wickleri, (e) N. sp. “Mbandaka”, (f) N. sp. “Ndongo”, (A) S. sp. “dwarf”, S. sp. “bulky head”, S. bleheri, S. sp. “Maluku” (B) S. sp. “red eye”, (C) S. sp. “Kwilu” (D) S. rouxi, (E) S. sp. “Mbandaka”, S. sp “Maluku” (F) S. ubanguiensis, (G) S. sp. “Kisangani” and (H) S. sp. “Nki. Sampling locations along the lower Congo are presented in larger scale and marked by red circles. Numbers along the lower Congo correspond to the sample site legend in the lower right side. White background highlights the territory of the Democratic Republic of Congo.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0022380-g001: Location map of sampling sites.Circles correspond to Steatocranus and squares to Nanochromis sampling sites. The filled circle and square mark the location of unsamples species. The half filled circle indicate that the species was included in the sequence but not in the AFLP analysis. Letters correspond to non-lower-Congo species distributions: (a) Nanochromis parilus, (b) N. teugelsi, (c) N. nudiceps, (d) N. transvestitus, N. wickleri, (e) N. sp. “Mbandaka”, (f) N. sp. “Ndongo”, (A) S. sp. “dwarf”, S. sp. “bulky head”, S. bleheri, S. sp. “Maluku” (B) S. sp. “red eye”, (C) S. sp. “Kwilu” (D) S. rouxi, (E) S. sp. “Mbandaka”, S. sp “Maluku” (F) S. ubanguiensis, (G) S. sp. “Kisangani” and (H) S. sp. “Nki. Sampling locations along the lower Congo are presented in larger scale and marked by red circles. Numbers along the lower Congo correspond to the sample site legend in the lower right side. White background highlights the territory of the Democratic Republic of Congo.
Mentions: Species of the two lower Congo cichlid genera Steatocranus and Nanochromis show a scattered distribution of few predominantly allopatric species within the Congo basin (Fig. 1) with a remarkable peak of recently discovered species richness (described and undescribed) endemic to the lower Congo (N (Steatocranus)  = 10, N (Nanochromis)  = 3). Apart from the lower Congo, Nanochromis species are distributed mainly south to the central Congo basin in Lakes Tumba and Mai Ndombe and adjacent rivers (N. wickleri and N. transvestitus, N. nudiceps) or in the Kasai River drainage (N. teugelsi). One undescribed species (N. sp. “Ndongo”) has recently been discovered in rivers Ngoko and Sangha (pers. obs.), both forming a northwestern Congo tributary, and another yet undescribed species (N. sp. “Mbandaka”) is known from the Congo mainstream around Mbandaka [16]. Nanochromis parilus is distributed in the lower Congo but also above Malebo Pool e.g. at Maluku. Steatocranus species occurring outside the lower Congo are distributed either in northern tributaries (S. sp. “Nki”, S. ubanguiensis and S. sp. “Lefini” from Ngoko, Ubangi and Lefini rivers) or south to the Congo mainstream (S. rouxi, S. sp. “red eye”, S. sp. “Kwilu” from Kasai, Kwango and Kwilu rivers), or in the Congo proper (S. sp. “dwarf”, S. sp. “bulky head”, S. bleheri, S. sp. “Maluku”, S. sp. “Mbandaka” and S. sp. “Kisangani” from around Malebo Pool, Maluku, Mbandaka and Kisangani). The haplotilapiine genus Steatocranus consists of rheophilic species whereas within the chromidotilapiine genus Nanochromis adaptations to high current are less obvious [4], [17], [18]. Habitat preferences differ between the mainly rock-dwelling Steatocranus and the more sand-dwelling Nanochromis (pers. obs.). Lower Congo Steatocranus are characterized by divergence in trophic traits indicating ecologically differentiated trait utility, i.e. dentition used for algae scraping (“aufwuchs feeding”), molluscivory and drift feeders ([4], pers. obs.). Recent surveys by different teams along multiple locations along the Lower Congo discovered that the species distribution of cichlids along the Lower Congo is not homogeneous. Both Nanochromis and Steatocranus species can be confined to short rapids stretches, and partially occur syntopically with close congenerics, whereas other species are less restricted in their distribution and/or represent the single genus representative in a selected rapids stretch.

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