Molecular evidence for naturally occurring intra- and inter-generic hybridization in the genus Ecklonia (Laminariales, Phaeophyceae)

Abstract

ABSTRACT Reports of naturally occurring hybridization between species and genera in Laminariales are limited. Hybrids are mostly identified based on morphological evidence, which is often inadequate to distinguish hybrids from other unusual kelp morphological variants. In the present study, we found morphologically atypical Ecklonia (Ec.), which were suspected of being hybrids between Ec. radicosa (Ecr) and Ec. cava subsp. stolonifera (Eccs) (IKI 09–23) or between Ecr and Eisenia (Ei.) nipponica (Ein) (OWS 07–13), in two localities in Japan. To verify the existence of naturally occurring hybrids in Ec., we determined their maternal ancestry by mtDNA genotyping and assigned the putative hybrids to four categories (F1, F2 and backcross to parental species) based on microsatellite markers. The morphologically atypical specimens were defined as: F1 generation of Ecr ♂ × Eccs ♀ (IKI 12, IKI 15–17 and IKI 19–22), Ecr ♀ × Eccs ♂ (IKI 11), or Ecr ♂ × Ein ♀ (OWS 07 and OWS 10–13), with relatively high posterior probabilities (>0.700). The remaining specimens were non-hybrids (Eccs: IKI 09, IKI 10 and IKI 13; Ecr: IKI 18), F1 or backcrosses to Ecr (IKI 14, IKI 23 and OWS 08) and F1, F2 or backcrosses to Ecr (OWS 09). Our results provide strong genetic evidence for the existence of intra- and inter-generic hybrids of Ecklonia in the field.