Comment on "Origin of the Superflock of Cichlid Fishes from Lake Victoria, East Africa"

Stager, J. Curtis; Day, Julia J.; Santini, Simona

doi:10.1126/science.1091978

Cited by 7 publications

(7 citation statements)

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“…Despite strong evidence for late Pleistocene desiccation, and the universal acceptance of it within the geological and paleoclimate communities, debate over the reality of that event still persists among some evolutionary biologists (Fryer, 1997(Fryer, , 2001(Fryer, , 2004Nagl et al, 2000;Seehausen, 2002;Seehausen et al, 2003;Verheyen et al, 2003;Stager et al, 2004). For example, Fryer (2001) claims that the drying out of the lake ''... cannot be treated seriously,' ' Joyce et al (2005) say that the endemic fishes evolved over ''15,000-250,000 years,'' and Abila et al (2004) suggest that Victoria's hundreds of species of endemic cichlids ''...evolved in a recordsetting 100,000 years...'' rather than over the much shorter time period that is clearly indicated by geological evidence.…”

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confidence: 99%

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

2007

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Lingering debate among evolutionary biologists over whether or not Lake Victoria dried out during the late Pleistocene focuses on perceived conflicts between biological and geological evidence for the age of its endemic species. This article reviews and updates the geophysical and paleoecological evidence for lake-wide desiccation and describes the environmental conditions that aquatic species likely experienced during the low stand. Lake Victoria was at its lowest between 18,000 and 14,000 calendar years ago, and it dried out at least once during that time. There is no evidence of remnant ponds or marshes persisting within the desiccated basin. If such features existed, then they would have been small, shallow, turbid, and/or saline, and therefore markedly different from the lake to which today's species are adapted. The existence of Lake Victoria's diverse endemic biota must be reconciled with the incontrovertible geophysical and paleoecological evidence of a ca. 15,000 year age for the lake, and not vice versa.

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Section: Introductionmentioning

confidence: 99%

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

2007

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“…First, we point out that the geological evidence for a complete drying-out of the LV basin ϳ15,000 years ago may not be as unambiguous as suggested by Stager et al (5). An earlier study (7) coauthored by one of the authors of the current comment concluded that "there is no evidence that the lake level fell low enough to confine fishes to refugia in small isolated ponds or around river mouths," and also suggested that the paleolimnological data were not sufficient to suppose that LV "dried up completely or even became highly concentrated."…”

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“…Stager et al (5) further contend that the calibration of the molecular clock we used (12) is inaccurate, citing other molecular phylogenetic work (13) in support of their claim that the LV cichlid species flock is only ϳ14,000 to 16,000 years old. However, all molecular phylogenetic studies-those that were published before (14) the paper by Johnson et al (6) and, more important, those that have been published since (1,13,15,16), including the reference (13) that Stager et al (5) cite to the contrary-agree that the "genetic diversity [of the LV superflock] is considerably older than the 15,000 years that have passed since the lake began to refill" (13). All molecular studies suggest an age of at least 100,000 years for these genetic lineages and, probably, species, in contrast to the claim by Stager et al (5).…”

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“…Stager et al (5) question some of the interpretations of our genetic results, based on what they perceive to be the welldocumented geological history of East Africa and, in particular, of LV, which might have dried out completely ϳ15,000 years ago (6). They argue that no refuges at all could have existed within the LV basin, and that even if refuges had existed in LV they would have been too small, too shallow, too turbid, or chemically too concentrated to maintain a diverse set of lake-adapted haplochromine lineages.…”

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“…They argue that no refuges at all could have existed within the LV basin, and that even if refuges had existed in LV they would have been too small, too shallow, too turbid, or chemically too concentrated to maintain a diverse set of lake-adapted haplochromine lineages. Stager et al (5) further suggest that the LV cichlids evolved in parallel with the species flock of LK only during the last ϳ15,000 years after LV refilled, with lineages of cichlids that were seeded from potential Rwandan highland river refugial populations.…”

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Response to Comment on "Origin of the Superflock of Cichlid Fishes from Lake Victoria, East Africa"

Verheyen

Salzburger

Snoeks

et al. 2004

Science

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Freshwater Molluscs of the Nile Basin, Past and Present

Damme

Bocxlaer

2009

The Nile

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The malacofauna of the Nile is poor compared to that of the Congo and its degree of endemicity is lower. While the highest species richness of the Congo Basin is in stenotopic taxa that live in the rivers and lakes, the highest diversity in the Nile Basin occurs in eurytopic taxa living in fringe habitats such as temporary pools. The paucity of endemics that need perennial waters as well in the Lower Nile as in the White Nile confirms the geological evidence indicating instability and discontinuity in water supply during Plio-Pleistocene times. The fauna of the Nile is predominantly Afrotropical in the Lower Nile and exclusively Afrotropical south of the junction of the White Nile and Blue Nile. Of all sub-basins, the degree of endemicity (either zero or two species) is lowest in the Equatorial Nile, indicating that the perennial aquatic environment in this sub-basin is young (probably Holocene) and lending support to the idea that the Bahr el Arab and White Nile Transcontinental Rift System were hydrologically unstable, with endorheic, alkaline lakes during most of the Plio-Pleistocene (Salama, 1997). In the Lower (Egyptian) Nile and in the Ethiopian Highlands palaearctic faunal components occur, consisting of widespread species and of a limited number of endemics of palaearctic origin, related to Levantine species. Most of these taxa first appear in the fossil record around 2.5 Ma. There is no evidence that the Nile functioned as an invasion route for Eurasiatic species prior to that time. Only Theodoxus niloticus is possibly of Paratethyan origin and may have invaded in the Late Miocene. The main invasion of freshwater molluscs into Africa appears to have occurred via the Horn of Africa in Middle and Late Miocene times. In the East African Rift, a diversified fauna occurs that only shares a fraction of species with the Nile Basin north of the Albert Nile (> ~5° N). In the equatorial headwaters, some species from southern Africa reach their northern limit, but the main community consists of species that are either endemic to one of the rift lakes or endemic to the region stretching from Turkana to the Kivu Basins. There hence exists a distinct East African bio-province, that was already recognisable in Pliocene assemblages and that had developed before the present lakes formed in the Late Pleistocene. Concerning the young age of Lake Victoria and the occurrence of an endemic cichlid superflock in the lake, the fossil molluscan record points to a persistence in the East African Rift of freshwater bodies sufficiently extensive to harbour a molluscan community — and ipso facto also fish — during periods of aridity/hyperaridity. The hypothesis of Verheyen et al. (2003, 2004), that the stem lineages of the East African haplochromines, presently inhabiting Lakes Victoria, Kyoga, Rukwa, Albert, George, Edward and surrounding waters, already existed during the Late Pliocene is consistent with the fossil evidence. The location of the area(s) of refuge (around Mount Elgon?) remains hypothetic, however. The fossil records...

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Comment on "Origin of the Superflock of Cichlid Fishes from Lake Victoria, East Africa"

Cited by 7 publications

References 11 publications

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

Response to Comment on "Origin of the Superflock of Cichlid Fishes from Lake Victoria, East Africa"

Freshwater Molluscs of the Nile Basin, Past and Present

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