The age of lice (Phthiraptera): Assessing the utility of molecular data for dating ancient louse radiations
Başlık:
The age of lice (Phthiraptera): Assessing the utility of molecular data for dating ancient louse radiations
Yazar:
Ford, Tom, author.
ISBN:
9780438059801
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (184 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: Rod Page.
Özet:
The age of parasitic lice (Insecta: Phthiraptera) is investigated with respect to coevolutionary patterns with avian and mammalian hosts. Qualitative tests of phylogenetic utility are employed to assess the suitability of various molecular data sources for estimating basal louse phylogeny. Wingless, a novel genetic marker for lice, is found to be a positive addition to the Phthirapteran molecular 'tool kit'. The role that these qualitative techniques can have in optimal data selection is discussed, with particular reference to combined datasets and codon positions in the mitochondrial gene COI. Molecular data techniques are used to approximate the origin of lice in two quite different ways. Firstly, using a penalised likelihood approach, the rate of louse evolution from four independent molecular markers is calibrated with respect to the rest of insects using external fossil data. Although results from the wingless marker are promising, age estimates from the different markers vary greatly, the potential reasons for this are discussed. Secondly the rate of louse evolution, for a combined molecular data set, is calibrated internally using host fossils at postulated cospeciation points, and a Bayesian 'relaxed clock' approach. This method yields an early Cretaceous age for lice, which both independently corroborates a Cretaceous radiation for modem birds, and suggests a generalised history of cospeciation between the parasites and avian hosts. The accuracy of the results is discussed in the light of recent palaeontological findings. An additional qualitative study uses experimental design methods to predict markers that could make a valuable contribution to molecular dating studies of lice. Using a method based on the Fisher's information index, the expected information per site with respect to branch lengths is calculated for an EFl? basal louse phylogeny. Scaling this tree by different substitution rates indicates an optimum tempo, to which relative rates from 36 genes, based on other insect sequences, are compared. This process enables the cautious identification of several candidate genes for further investigation of basal louse phylogeny. Future prospects for investigating louse evolution and ancient host associations are considered in light of the findings presented here.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684757.1) | 684757-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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