Figure 1.

(a) Simplified reproductive framework of the S. alburnoides allopolyploid complex in the Ocreza River (Tagus drainage, Central Portugal), showing the core of its reproductive dynamics and its relationship with the sympatric bisexual S. pyrenaicus. Males and females are represented in blue and pink, respectively. (b) Table of all crosses that could theoretically occur in the referred population. Reproductive modes include meiotic hybridogenesis in PAA females, clonal spermatogenesis in PA, PAA, and PPA males, and regular meiosis in PPAA and PP individuals; 5n offspring is unviable. Dark grey circles represent eggs. Capital letters refer to fish genomes, and small letters to gamete genomes: A, a from the Anaecypris-like paternal ancestor of the complex; P, p from the S. pyrenaicus maternal ancestor of the complex. (Online version in colour.)