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The effect of ancient population bottlenecks on human phenotypic variation.

ABSTRACT: The origin and patterns of dispersal of anatomically modern humans are the focus of considerable debate. Global genetic analyses have argued for one single origin, placed somewhere in Africa. This scenario implies a rapid expansion, with a series of bottlenecks of small amplitude, which would have led to the observed smooth loss of genetic diversity with increasing distance from Africa. Analyses of cranial data, on the other hand, have given mixed results, and have been argued to support multiple origins of modern humans. Using a large data set of skull measurements and an analytical framework equivalent to that used for genetic data, we show that the loss in genetic diversity has been mirrored by a loss in phenotypic variability. We find evidence for an African origin, placed somewhere in the central/southern part of the continent, which harbours the highest intra-population diversity in phenotypic measurements. We failed to find evidence for a second origin, and we confirm these results on a large genetic data set. Distance from Africa accounts for an average 19-25% of heritable variation in craniometric measurements-a remarkably strong effect for phenotypic measurements known to be under selection.

SUBMITTER: Manica A

PROVIDER: S-EPMC1978547 | biostudies-literature | 2007 Jul

REPOSITORIES: biostudies-literature

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The effect of ancient population bottlenecks on human phenotypic variation.

Manica Andrea A Amos William W Balloux François F Hanihara Tsunehiko T

Nature 20070701 7151

The origin and patterns of dispersal of anatomically modern humans are the focus of considerable debate. Global genetic analyses have argued for one single origin, placed somewhere in Africa. This scenario implies a rapid expansion, with a series of bottlenecks of small amplitude, which would have led to the observed smooth loss of genetic diversity with increasing distance from Africa. Analyses of cranial data, on the other hand, have given mixed results, and have been argued to support multipl ...[more]

PMID: 17637668

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Project description:It is becoming increasingly clear that microbial symbionts influence key aspects of their host's fitness, and vice versa. This may fundamentally change our thinking about how microbes and hosts interact in influencing fitness and adaptation to changing environments. Here we explore how reductions in population size commonly experienced by threatened species influence microbiome diversity. Consequences of such reductions are normally interpreted in terms of a loss of genetic variation, increased inbreeding and associated inbreeding depression. However, fitness effects of population bottlenecks might also be mediated through microbiome diversity, such as through loss of functionally important microbes. Here we utilise 50 Drosophila melanogaster lines with different histories of population bottlenecks to explore these questions. The lines were phenotyped for egg-to-adult viability and their genomes sequenced to estimate genetic variation. The bacterial 16S rRNA gene was amplified in these lines to investigate microbial diversity. We found that 1) host population bottlenecks constrained microbiome richness and diversity, 2) core microbiomes of hosts with low genetic variation were constituted from subsets of microbiomes found in flies with higher genetic variation, 3) both microbiome diversity and host genetic variation contributed to host population fitness, 4) connectivity and robustness of bacterial networks was low in the inbred lines regardless of host genetic variation, 5) reduced microbial diversity was associated with weaker evolutionary responses of hosts in stressful environments, and 6) these effects were unrelated to Wolbachia density. These findings suggest that population bottlenecks reduce hologenomic variation (combined host and microbial genetic variation). Thus, while the current biodiversity crisis focuses on population sizes and genetic variation of eukaryotes, an additional focal point should be the microbial diversity carried by the eukaryotes, which in turn may influence host fitness and adaptability with consequences for the persistence of populations.

Dataset Information

The effect of ancient population bottlenecks on human phenotypic variation.

Publications

The effect of ancient population bottlenecks on human phenotypic variation.

Similar Datasets

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