Different mating systems are expected to affect the extent and direction of hybridization. Due to the different levels of sexual conflict, the weak inbreeder/strong outbreeder (WISO) hypothesis predicts that gametes from self-incompatible (SI) species should outcompete gametes from self-compatible (SC) ones. However, other factors such as timing of selfing and unilateral incompatibilities may also play a role on the direction of hybridization. In addition, differential mating opportunities provided by different mating systems are also expected to affect the direction of introgression in hybrid zones involving outcrossers and selfers. Here, we explored these hypotheses with a unique case of recent hybridization between two mangrove killifish species with different mating systems, Kryptolebias ocellatus (obligately outcrossing) and K. hermaphroditus (predominantly self-fertilizing) in two hybrid zones in southeast Brazil. Hybridization rates were relatively high (~20%), representing the first example of natural hybridization between species with different mating systems in vertebrates. All F1 individuals were sired by the selfing species. Backcrossing was small, but mostly asymmetrical with the SI parental species, suggesting pattern commonly observed in plant hybrid zones with different mating systems. Our findings shed light on how contrasting mating systems may affect the direction and extent of gene flow between sympatric species, ultimately affecting the evolution and maintenance of hybrid zones.

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Published in Genes, v. 12, issue 10, 1486.

© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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This work was supported by National Geographic/Waitt program [W461-16], the Fisheries Society of the British Isles (FSBI) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) [233161/2014-7].

Related Content

FastaQC files for GBS library can be accessed at NCBI (accession PRJNA563625).

Sequence and microsatellite data are available in Supplementary Material, which is also available for download as the additional file listed at the end of this record.

All scripts used in the project are available at: https://github.com/waldirmbf/BerbelFilho_etal_KryptolebiasHybridisation.

genes-12-01486-s001.zip (678 kB)
Supplementary file