Dataset Information

The influence of body size and net diversification rate on molecular evolution during the radiation of animal phyla.

ABSTRACT:

Background

Molecular clock dates, which place the origin of animal phyla deep in the Precambrian, have been used to reject the hypothesis of a rapid evolutionary radiation of animal phyla supported by the fossil record. One possible explanation of the discrepancy is the potential for fast substitution rates early in the metazoan radiation. However, concerted rate variation, occurring simultaneously in multiple lineages, cannot be detected by "clock tests", and so another way to explore such variation is to look for correlated changes between rates and other biological factors. Here we investigate two possible causes of fast early rates: change in average body size or diversification rate of deep metazoan lineages.

Results

For nine genes for phylogenetically independent comparisons between 50 metazoan phyla, orders, and classes, we find a significant correlation between average body size and rate of molecular evolution of mitochondrial genes. The data also indicate that diversification rate may have a positive effect on rates of mitochondrial molecular evolution.

Conclusion

If average body sizes were significantly smaller in the early history of the Metazoa, and if rates of diversification were much higher, then it is possible that mitochondrial genes have undergone a slow-down in evolutionary rate, which could affect date estimates made from these genes.

SUBMITTER: Fontanillas E

PROVIDER: S-EPMC1929056 | biostudies-literature | 2007 Jun

REPOSITORIES: biostudies-literature

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Publications

The influence of body size and net diversification rate on molecular evolution during the radiation of animal phyla.

Fontanillas Eric E Welch John J JJ Thomas Jessica A JA Bromham Lindell L

BMC evolutionary biology 20070626

<h4>Background</h4>Molecular clock dates, which place the origin of animal phyla deep in the Precambrian, have been used to reject the hypothesis of a rapid evolutionary radiation of animal phyla supported by the fossil record. One possible explanation of the discrepancy is the potential for fast substitution rates early in the metazoan radiation. However, concerted rate variation, occurring simultaneously in multiple lineages, cannot be detected by "clock tests", and so another way to explore s ...[more]

PMID: 17592650

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Project description:Parasite lineages commonly diverge when host lineages diverge. However, when large clades of hosts and parasites are analyzed, some cases suggest host switching as another major diversification mechanism. The first step in host switching is the appearance of a parasite on an atypical host, or "straggling." We analyze the conditions associated with straggling events. We use five species of colonially nesting seabirds from the Galapagos Archipelago and two genera of highly specific ectoparasitic lice to examine host switching. We use both genetic and morphological identification of lice, together with measurements of spatial distribution of hosts in mixed breeding colonies, to test: (1) effects of local host community composition on straggling parasite identity; (2) effects of relative host density within a mixed colony on straggling frequency and parasite species identity; and (3) how straggling rates are influenced by the specifics of louse attachment. Finally, we determine whether there is evidence of breeding in cases where straggling adult lice were found, which may indicate a shift from straggling to the initial stages of host switching. We analyzed more than 5,000 parasite individuals and found that only ~1% of lice could be considered stragglers, with ~5% of 436 host individuals having straggling parasites. We found that the presence of the typical host and recipient host in the same locality influenced straggling. Additionally, parasites most likely to be found on alternate hosts are those that are smaller than the typical parasite of that host, implying that the ability of lice to attach to the host might limit host switching. Given that lice generally follow Harrison's rule, with larger parasites on larger hosts, parasites infecting the larger host species are less likely to successfully colonize smaller host species. Moreover, our study supports the general perception that successful colonization of a novel host is extremely rare, as we found only one nymph of a straggling species, which may indicate successful reproduction.

Dataset Information

The influence of body size and net diversification rate on molecular evolution during the radiation of animal phyla.

Background

Results

Conclusion

Publications

The influence of body size and net diversification rate on molecular evolution during the radiation of animal phyla.

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