Biochemical Strain Variation in Parasitic Helminths

Host Availability and the Evolution of Parasite Life-History Strategies

“…In particular, our models show that the greater the degree of this environmental stochasticity, the greater the phenotypic variation in the parasite population. Substantial degrees of intraspecific genetic and phenotypic variation have been observed in the field for a variety of parasitic helminth species (Blouin et al 1995; Anderson et al 1998; Maizels and Kurniawan‐Atmadja 2002; Paterson and Viney 2003; Braisher et al 2004), with potentially important implications for the impact of disease on the host population (Bryant and Flockhart 1986; Rollinson et al 1986; Wakelin and Goyal 1996; Viney et al 2002), vaccine development (McManus and Hope 1993; Maizels and Kurniawan‐Atmadja 2002), the evolution of drug resistance (McManus and Hope 1993; Anderson et al 1998; Maizels and Kurniawan‐Atmadja 2002), and the success of disease management programs (Fenton et al 2006). Furthermore, in terms of entomopathogenic nematodes, previous workers have observed that only a small proportion of iJs infect at any one time, even under optimal conditions (Fan and Hominick 1991; Bohan and Hominick 1996; Griffin 1996; Campbell et al 1999).…”

On the biological and biochemical nature of cloned populations of Strongyloides ratti

“…In a review of biochemical strain variation in parasitic helminths, BRYANT & FLOCKHART (1986) amply demonstrated that variation within a helminth species is the usual condition; a condition which the authors considered a biological truism. Although it remains to be seen what variation can be detected in S. ratti using other methods, such as DNA restriction fragment length polymorphisms, our results show that levels of variation found within one species will not necessarily be found in all species of that genus.…”

Phylogenetic Pattern, Evolutionary Processes and Species Delimitation in the Genus Echinococcus

“…It has often been suggested that the reproductive biology of species of Echinococcus, with a combination of self-fertilisation and extensive asexual reproduction, has a profound effect on evolutionary processes, leading to the genetic uniformity of local populations and rapid genetic differentiation among populations subject to different selection pressures (Smyth and Smyth, 1964;McManus and Smyth, 1986;Bryant and Flockhart, 1986;Haag et al, 2008;Nakao et al, 2009Nakao et al, , 2010aNakao et al, , 2013b. This is thought to occur because the population genetic consequences of obligate self-fertilisation and asexual reproduction are almost complete homozygosity, extensive linkage disequilibrium (non-random association of alleles at different loci) and a distribution of genetic diversity between, rather than within family groups, which will lead to spatial structuring 11 of genetic variation if dispersal is limited.…”