Effective size of the hierarchically structured populations of the agent of malaria: a coalescent-based model.

Using the coalescence theory, we derived a simple expression for the asymptotic inbreeding effective population size of Plasmodium falciparum, the most malignant agent of malaria, in relationship to F-statistics at different hierarchical levels. We consider the effective size of malaria parasites, both for the intrinsic interest of the result for the study of this medically important organism and as an example illustrating general arguments that should clarify effective size calculations in a wide range of organisms with complex life cycles and a hierarchical population structure. We consider in this study a model with four hierarchical levels (villages, oocyst infrapopulations, oocysts within infrapopulations and the oocyst). The derived expression is applicable to both island and isolation by distance models and is a function of three F-statistics: the genetic differentiation among villages (F(VT)), the genetic differentiation among oocyst infrapopulations (F(MV)) and, finally, the departure from panmixia (F(IM)) within oocyst infrapopulations. The logic of the derivation of effective size presented in this study is applicable to any organism showing the same levels of subdivision.