Journalartikel

Jahr der Veröffentlichung: 2006

Seiten: 143-157

Zeitschrift: Malacologia

Bandnummer: 48

Heftnummer: 1/2

ISSN: 0076-2997

URL: https://www.biodiversitylibrary.org/item/47264#page/147/mode/1up

Verlag: Institute of Malacology

Abstract: 
Today, the human blood fluke, Schistosoma japonicum, is transmitted in China by two subspecies of the rissooidean snail taxon Oncomelania hupensis: O. h. hupensis and O. h. robertsoni. Whereas the eastern Chinese subspecies O. h. hupensis has been studied extensively using mitochondrial DNA sequences, very little data exists for the western subspecies O. h. robertsoni. Preliminary phylogeographic studies indicate that the latter shows a very high degree of genetic diversity with Kimura 2 parameter distances in the cytochrome oxidase I (COI) gene of up to 0.0932 (= 9.32%) among four sequences previously deposited in GenBank. Extreme degrees of intraspecific heterogeneity in gastropods have been reported before, and possible explanations include the presence of cryptic species complexes, isolation followed by secondary contact, heteroplasmy and duplications within the mitochondrial genome, the presence of "pseudogenes", and the retention of ancestral mitochondrial polymorphism.Given the great significance of understanding phylogeographic patterns in the intermediate schistosomiasis host Oncomelania h. robertsoni for comprehending host/parasite relationships, DNA sequences of two mitochondrial genes (COI and LSU rRNA) from 66 O. hupensis robertsoni specimens are used to (1) assess the phylogenetic position, (2) study the degree of heterogeneity within and between "populations", (3) provide a preliminary overview of the geographic distribution of major genetic groups and (4) study the phylogenetic concordance of the two gene fragments.Phylogenetic analyses, parametric bootstrapping and studies of sequence polymorphism show that: (1) all COI sequences are fully protein-coding with no insertions or deletions, (2) both individual and combined analyses of the COI and LSU rRNA genes show at least four distinct haplotype groups within O. h. robertsoni, (3) monophyly of the four clades cannot be confirmed, (4) there is high concordance in cluster patterns and arrangement of individual haplotypes of both gene fragments, (5) two of the genetic clades recovered appear to be localized, whereas the other two are widely distributed, and (6) sympatry of individuals belonging to different clades occurs. Moreover, based on preliminary AFLP analyses it could be shown that (7) there is no phylogenetic concordance between the mitochondrial and nuclear data presented here, and (8) the nuclear data from AFLP genotyping indicate a lack of clear population structure.Given the results of the present study, it is cautiously suggested that retention of ancestral mitochondrial DNA polymorphism possibly in combination with some effects of secondary contact (introgression) is the most probable explanation for the occurrence of deviant lineages in O. h. robertsoni. On the basis of nuclear, morphological, and ecological data, it is also suggested that there is no evidence of organismal subdivision in O. h. robertsoni. It is strongly recommended that future studies incorporate more data from nuclear loci in order to better understand phylogeography, population genetics, and host-parasite co-evolution in O. h. robertsoni.

Harvard-Zitierstil: Wilke, T., Davis, G., Qiu, D. and Spear, R. (2006) Extreme mitochondrial sequence diversity in the intermediate schistosomiasis host Oncomelania hupensis robertsoni: Another case of ancestral polymorphism?, Malacologia, 48(1/2), pp. 143-157. https://www.biodiversitylibrary.org/item/47264#page/147/mode/1up

APA-Zitierstil: Wilke, T., Davis, G., Qiu, D., & Spear, R. (2006). Extreme mitochondrial sequence diversity in the intermediate schistosomiasis host Oncomelania hupensis robertsoni: Another case of ancestral polymorphism?. Malacologia. 48(1/2), 143-157. https://www.biodiversitylibrary.org/item/47264#page/147/mode/1up