Differential sperm-egg interactions in experimental pairings between two subspecies and their hybrids in a passerine bird

Laura L. Hurley*, Melissah Rowe, Simon C. Griffith

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
4 Downloads (Pure)

Abstract

Speciation research has largely overlooked reproductive barriers acting between copulation and the formation of the zygote (i.e., postmating, prezygotic [PMPZ] barriers), especially in internally fertilizing vertebrates. Nonetheless, it is becoming clear that PMPZ reproductive barriers can play a role in the formation and maintenance of species boundaries. We investigated sperm-egg interactions in the recently diverged subspecies pairs of the long-tailed finch, Poephila acuticauda acuticauda and P. a. hecki, to explore potential PMPZ barriers. Specifically, we compared the number of sperm reaching the perivitelline layer (PVL) of the ova, and hence the site of fertilization, in both intra- and inter-subspecies pairings and pairings of F1 hybrid adults with one parental subspecies. Although we found no difference in PVL sperm number among intra- and inter-subspecific pairs, a significantly lower number of sperm reached the site of fertilization in a backcross pairing. As low numbers of PVL sperm appear to be associated with low fertilization success in birds, our findings offer insight into the potential role of postcopulatory processes in limiting gene flow between the subspecies and may help explain the relatively narrow hybrid zone that exists in the wild in this species. Though further work is needed to gain a comprehensive understanding of the morphological, physiological, and molecular mechanisms underlying our results, our study supports the role of PMPZ reproductive barriers in avian speciation, even in recently diverged taxa, that may not yet be fully genetically incompatible.

Original languageEnglish
Pages (from-to)11725-11732
Number of pages8
JournalEcology and Evolution
Volume8
Issue number23
Early online date31 Oct 2018
DOIs
Publication statusPublished - Dec 2018

Bibliographical note

Copyright the Author(s) 2018. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • finch
  • hybridization
  • perivitelline layer
  • postmating prezygotic reproductive barriers
  • speciation

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