Outbreeding lethality between toxic Group I and nontoxic Group III Alexandrium tamarense spp. isolates: Predominance of heterotypic encystment and implications for mating interactions and biogeography

摘要: We report the zygotic encystment of geographically dispersed isolates in dinoflagellate species complex Alexandrium tamarense, particular, successful mating toxic Group I and nontoxic III isolates. However, hypnozygotes produced I/III co-cultures complete no more than three divisions after germinating. Previous reports have suggested a mate recognition mechanism whereby could arise from either homotypic (inbred) or heterotypic (outbred) gamete pairs. To determine extent to which each occurs, nested PCR assay was developed parentage individual hypnozygotes. The vast majority pairwise were outbred, so that inviability result hybridization, not inbreeding. These findings support assertion speciation underlies phylogenetic structure tamarense complex. Additionally, ribosomal DNA (rDNA) copy numbers both hybrid single ribotype reduced substantially those haploid motile cells. destruction rDNA loci may be crucial for genetically distant conjugants appears integral process encystment. The hybrids is important public health because presence cysts indicate ongoing displacement population by one (or vice versa). Hybrid also suggests bloom control strategy persistent, blooms mitigated introduction potential hybridization nature investigated applying Belfast Lough, Northern Ireland, region where populations co-occur. Two identified 14 assays, demonstrating do interbreed region. an analysis data collected over 18-year period indicated leaky pre-mating barrier between (including Groups III). Whether observed selectivity inhibits dependent on its mechanism. If point induction gametogenesis, dissimilar ribotypes freely, promoting cases lethal. instead, occurs during adhesion pairs, it enable stable co-existence A. species. In case, impose significant obstacle range expansion. here valuable tool investigation interspecies consequences global biogeography these organisms.