HYBRIDOGENETIC REPRODUCTION AND MATERNAL ANCESTRY OF POLYPLOID IBERIAN FISH - THE TROPIDOPHOXINELLUS-ALBURNOIDES COMPLEX

Iberian minnows collectively known as the Tropidophoxinellus alburnoid es STEINDACHNER complex comprise diploid and polyploid forms with high ly female biased sex ratios. Previous investigators suggested that all -female clonal reproduction and interspecific hybridization may occur in this complex. We examined nuclear (allozymes) and cytoplasmic genes (mtDNA) to assess the evolutionary origins, relationships, and reprod uctive modes of T. alburnoides from western Spain. The multi-locus all ozyme data dearly revealed the hybrid nature of all polyploid forms of this fish and some diploid forms as well. Diagnostic markers identifi ed fish from the genus Leuciscus as the paternal ancestor of hybrids i n the Duero and Guadiana River Basins. Additionally, analysis of nucle ar markers revealed that hybridogenetic reproduction occurs in the dip loid and triploid hybrids. The hybrids fully express the paternal Leuc iscus genome and then discard it during oogenesis. Hybridogenetic ova contain only maternal nuclear genes and mtDNA from a non-hybrid T. alb urnoides ancestor. Apparently diploid and triploid hybrids of T. albur noides persist as sperm parasites on males of a sexually reproducing L euciscus host species.