Oh, Sang-Hun .
Homoploid hybridization in Neillia (Rosaceae): genetic evidence for recombinational speciation.
While evolution via allopolyploidization has been well documented in a wide range of taxa, cases of speciation through diploid hybridization have been rarely reported. The genus Neillia with 12 species of deciduous shrubs in eastern Asia provides a novel system for understanding of the genetic basis of homoploid hybridization in woody angiosperms. All species that have been examined in Neillia are diploid, and three species formerly classified in Stephanandra, N. incisa, N. hanceana, and N. tanakae, have been postulated to have originated via hybridization between N. uekii and the stem lineage of the N. thyrsiflora/N. gracilis clade. In order to further test the hypothesis and to gain insight on genome evolution in the hybrid species, nucleotide sequences of PISTILLATA (PI), CRABS CLAW (CRC), and granule-bound starch synthase (GBSSI-1), all low-copy nuclear protein-coding genes, were determined from 17 plants of ten species of Neillia. Separate phylogenetic analyses of PI, CRC, and GBSSI-1 along with previous data (cpDNA, ITS, ETS, and LEAFY) not only supported a hybrid origin of N. incisa, N. hanceana, and N. tanakae but revealed that N. affinis may also be independently derived via homoploid hybridization. No evidence of additivity of parental markers was found in the nuclear genes of the four hybrid species. Phylogenetic placement of the hybrids was strongly incongruent between a set of genes, but was consistent across genes in each set of genes. GBSSI-1 sequences of the hybrid species showed a strong signature of recombination of parental sequences. Recombination patterns in N. incisa, N. hanceana, and N. tanakae are similar to one another, but differ from those in N. affinis. Results of this study suggest that the diploid hybrids of Neillia have evolved multiple times, supporting the genetic model of recombinational speciation.
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1 - Cornell University, L. H. Bailey Hortorium, Department of Plant Biology, 412 Mann Library, Ithaca, New York, 14853, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 182/I K Barber
Date: Monday, July 28th, 2008
Time: 10:45 AM