title: Contact zone dynamics during early stages of speciation in a chorus frog (Pseudacris crucifer).
abstract: Characterizing the genetic and behavioural consequences of contact between previously geographically isolated lineages provides insights into the mechanisms underlying diversification and ultimately speciation. The spring peeper (Pseudacris crucifer) is a widespread Nearctic chorus frog with six divergent mitochondrial DNA (mtDNA) lineages, many of which came into secondary contact during the Holocene. We examined genetics, morphology, advertisement calls and female preference for two lineages that began diverging in allopatry in the Pliocene and now overlap in southwestern Ontario, Canada. We found non-coincident clines in mtDNA and nuclear DNA, mirroring directionality of premating isolation barriers. We also found divergence in a range of traits between these two lineages, displacement in male call attributes and female preference for calls of their natal lineage in sympatry. Hybrids were morphologically distinct from both parental lineages, but hybrid male calls were acoustically intermediate. Female hybrids showed asymmetrical preference for Eastern male calls. These results considered together provide evidence of either unidirectional hybridization or selection against hybrids, potentially implying reproductive character displacement. Our work demonstrates the utility of integrated, multi-character approaches to understanding the processes of divergence and the nature of speciation.
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada.|College of Environmental Science and Engineering, Sino-Canada Centre for Environmental and Sustainable Development, Tongji University, Shanghai, People's Republic of China.
authors.forename: K A
authors.initials: KA
authors.lastname: Stewart
authors.affiliation: Department of Wildlife Ecology and Conservation, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Austin
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Zamudio
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada.
authors.forename: S C
authors.initials: SC
authors.lastname: Lougheed
mesh_terms: D000818:Animals; D001001:Anura / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics; D005260:Female; D005819:Genetic Markers; D049810:Genetic Speciation; D005828:Genetics, Population; D005838:Genotype; D008297:Male; D052586:Mating Preference, Animal; D018895:Microsatellite Repeats; D009864:Ontario; D017422:Sequence Analysis, DNA; D014828:Vocalization, Animal
chemical_list: D004272:DNA, Mitochondrial; D005819:Genetic Markers