The genetics of maintenance of an all‐male lineage in the Squalius albuvnoides complex

Squalius alburnoides is a complex of minnows common to the Iberian Peninsula, consisting of two distinct forms. The most common form is comprised of diploid and polyploid asexual hybrids heterozygous for several diagnostic allozyme loci contributed by Squalius pyrenaicus or Squalius carolitertii and a missing ancestor. The other form is diploid and homozygous for the allele contributed by the missing ancestor at these same loci. Present results from analyses of sex ratio and cytochrome b sequences are not consistent with the evolutionary distinctiveness of this non‐hybrid form and suggest that it represents an all‐male lineage imbedded within an almost all‐female complex. This all‐male lineage allowed preservation of the ancestral paternal nuclear genome after the paternal ancestor became extinct in all or most drainages, withimportant evolutionary implications.