Characterization of a hybrid zone between two annual killifish genus Austrolebias from the Biosphere Reserve and Ramsar
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PRIMARY RESEARCH PAPER
Characterization of a hybrid zone between two annual killifish genus Austrolebias from the Biosphere Reserve and Ramsar Sites in South America Graciela Garcı´a . Vero´nica Gutie´rrez . Ne´stor Rı´os . Nicola´s Papa . Sebastia´n Serra . Marcelo Loureiro
Received: 25 April 2019 / Revised: 16 September 2019 / Accepted: 12 October 2019 Ó Springer Nature Switzerland AG 2019
Abstract This study attempts to characterize species boundaries in the hybrid zone between two taxa of the South American killifish genus Austrolebias (Cyprinodontiformes: Rivulidae), A. charrua and A. reicherti, to test mechanisms underlying secondary contact and introgression. The hybrid zone spans in a narrow area of approximately 106 km2 in the Patos-Merin System. Present analyses were based on seven microsatellite loci, and one mitochondrial marker and morphology. Discriminant analysis of principal components
Handling editor: Christian Sturmbauer
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10750-019-04104-0) contains supplementary material, which is available to authorized users. G. Garcı´a (&) V. Gutie´rrez N. Rı´os S. Serra Seccio´n Gene´tica Evolutiva, Facultad de Ciencias, UdelaR, Igua´ 4225, CP. 11400 Montevideo, Uruguay e-mail: [email protected] S. Serra M. Loureiro Departamento de Ecologı´a y Evolucio´n, Facultad de Ciencias, UdelaR, Igua´ 4225 11400 Montevideo, Uruguay
(DAPC) and morphology detected five hybrid populations. Structure and Newhybrids analyses suggested the existence of a bimodal hybrid zone, in which hybrids predominantly consist of individuals genetically similar to one or other parental genotype, with few intermediates. The existence of bidirectional backcrossing was evident through AMOVA analyses using both nuclear and mitochondrial markers, haplotype network, and long-term asymmetric gene flow estimates. Several mechanisms may underlie the patterns of mitochondrial and nuclear gene flow such as differential fitness of intraspecific and interspecific cyto-nuclear combinations and selection against female function in interspecific backcrosses. Finally, present results highlight the role of natural hybridization and introgression to increase morphological and genetic variability contrasting with inbreeding and genetic drift which occur in each temporal pond where these endangered killifish species live. Keywords Annual killifish Hybrid zone Austrolebias Rivulidae Genetics Morphology Conservation
N. Papa Seccio´n Biologı´a Celular, Facultad de Ciencias, UdelaR, Igua´, 4225, 11400 Montevideo, Uruguay
Introduction
S. Serra M. Loureiro Seccio´n Ictiologı´a, Museo Nacional de Historia Natural, Montevideo, Uruguay
Hybrid zones have been long times ago recognized as ‘‘windows’’ on the evolutionary process or laboratories for studying divergence and speciation (Hewitt,
123
Hydrobiologia
1988; Harrison 1990). In fact, hybridization and introgression are hierarchized for the
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