Home About us Contact
|
Home About us Contact | ||
|
|
||
Uninfected Populations (uninfected + population)
Selected AbstractsWolbachia -induced unidirectional cytoplasmic incompatibility and the stability of infection polymorphism in parapatric host populationsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007M. FLOR Abstract Wolbachia are intracellular, maternally inherited bacteria that are widespread among arthropods and commonly induce a reproductive incompatibility between infected male and uninfected female hosts known as unidirectional cytoplasmic incompatibility (CI). If infected and uninfected populations occur parapatrically, CI acts as a post-zygotic isolation barrier. We investigate the stability of such infection polymorphisms in a mathematical model with two populations linked by migration. We determine critical migration rates below which infected and uninfected populations can coexist. Analytical solutions of the critical migration rate are presented for mainland-island models. These serve as lower estimations for a more general model with two-way migration. The critical migration rate is positive if either Wolbachia causes a fecundity reduction in infected female hosts or its transmission is incomplete, and is highest for intermediate levels of CI. We discuss our results with respect to local adaptations of the Wolbachia host, speciation, and pest control. [source] Genetic diversity and Wolbachia infection of the Drosophila parasitoid Leptopilina clavipes in western EuropeMOLECULAR ECOLOGY, Issue 5 2004Bart A. Pannebakker Abstract Wolbachia are maternally transmitted bacteria that alter their arthropod hosts' reproduction in various ways, including parthenogenesis induction (PI). Wolbachia -induced parthenogenesis can have drastic effects on the genetic structure of its host because it potentially reduces populations to clones without genetic exchange. However, Wolbachia -induced parthenogenesis does not inevitably result in a reduction of genetic variation of infected populations vs. uninfected populations, because the parthenogenetic populations are initially derived from uninfected populations and can thus show similar genetic variation. Here we investigate these issues in infected and uninfected populations of the Drosophila parasitoid Leptopilina clavipes in western Europe. Wasps from 19 sites in the Netherlands, France and northern Spain were screened for Wolbachia and analysed using amplified fragment length polymorphism (AFLP) markers. All the populations from the Netherlands and mid-France were infected with the same two strains of Wolbachia, whereas populations from the Pyrenees were not infected. The infected and uninfected populations show identical levels of genetic variation, but have clearly diverged genetically, indicating the presence of a barrier that prevents gene flow. Within the infected wasps two distinct genotypes were found at multiple localities, indicating the coexistence of multiple clones. The conditions promoting clonal coexistence in L. clavipes are discussed. [source] Assessing the long-term impact of Ranavirus infection in wild common frog populationsANIMAL CONSERVATION, Issue 5 2010A. G. F. Teacher Abstract Amphibians are declining worldwide, and one cause of this is infectious disease emergence. Mass mortalities caused by a virus or a group of viruses belonging to the genus Ranavirus have occurred in wild common frogs Rana temporaria in England since the 1980s, and ranaviral disease is widespread in amphibians in North America and Canada, where it can also cause mass die-offs. Although there have been numerous reports of Ranavirus -associated mass mortality events, no study has yet evaluated the long-term impacts of this disease. This study follows up archived records of English common frog mortalities likely caused by Ranavirus. There is a preliminary indication that common frog populations can respond differently to the emergence of disease: emergence may be transient, catastrophic, or persistent with recurrent mortality events. We subsequently focused on populations that had recurring mortality events (n=18), and we report median declines of 81% in the number of adult frogs in these populations from 1996 to 2008. Comparable uninfected populations (n=16) showed no change in population size over the same time period. Regressions show that larger frog populations may be more likely to experience larger declines than smaller populations, and linear models show that percentage population size change is significantly correlated with disease status, but that habitat age (a possible proxy for environmental quality) has no significant effect on population size change. Our results provide the first evidence of long-term localized population declines of an amphibian species which appear to be best explained by the presence of Ranavirus infection. [source] | ||||||||||