title: Variation in repeat length and heteroplasmy of the mitochondrial DNA control region along a core-edge gradient in the eastern spadefoot toad (Pelobates syriacus).
abstract: Peripheral populations are those situated at the distribution margins of a species and are often subjected to more extreme abiotic and biotic conditions than those at the core. Here, we hypothesized that shorter repeat length and fewer heteroplasmic mitochondrial DNA (mtDNA) copies, which are associated with more efficient mitochondrial function, may be related to improved survival under extreme environmental conditions. We sampled eastern spadefoot toads (mostly as tadpoles) from 43 rain pools distributed along a 300-km gradient from core to edge of the species' distribution. We show that mean pool tandem repeat length and heteroplasmy increase from edge to core, even after controlling for body size. We evaluate several alternative hypotheses and propose the Fisher hypothesis as the most likely explanation. However, additional sequential sampling and experimental studies are required to determine whether selection under extreme conditions, or alternative mechanisms, could account for the gradient in heteroplasmy and repeat length in the mtDNA control region.
authors.affiliation: School of Marine Sciences, Ruppin Academic Center, Michmoret 40297, Israel.
authors.forename: Inbar
authors.initials: I
authors.lastname: Munwes
authors.forename: Eli
authors.initials: E
authors.lastname: Geffen
authors.forename: Adam
authors.initials: A
authors.lastname: Friedmann
authors.forename: Yaron
authors.initials: Y
authors.lastname: Tikochinski
authors.forename: Sarig
authors.initials: S
authors.lastname: Gafny
mesh_terms: D000818:Animals; D001001:Anura / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D007557:Israel; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D004272:DNA, Mitochondrial