title: Coping with potential bi-parental inbreeding: limited pollen and seed dispersal and large genets in the dioecious marine angiospermThalassia testudinum.
abstract: The high prevalence of dioecy in marine angiosperms or seagrasses (>50% of all species) is thought to enforce cross-fertilization. However, seagrasses are clonal plants, and they may still be subject to sibling-mating or bi-parental inbreeding if the genetic neighborhood is smaller than the size of the genets. We tested this by determining the genetic neighborhoods of the dioecious seagrassThalassia testudinumat two sites (Back-Reef and Mid-Lagoon) in Puerto Morelos Reef Lagoon, Mexico, by measuring dispersal of pollen and seeds in situ, and by fine-scale spatial autocorrelation analysis with eight polymorphic microsatellite DNA markers. Prevalence of inbreeding was verified by estimating pairwise kinship coefficients; and by analysing the genotypes of seedlings grown from seeds in mesocosms. Average dispersal of pollen was 0.3-1.6 m (max. 4.8 m) and of seeds was 0.3-0.4 m (max. 1.8 m), resulting in a neighborhood area of 7.4 m2(range 3.4-11.4 m2) at Back-Reef and 1.9 (range 1.87-1.92 m2) at Mid-Lagoon. Neighborhood area (Na) derived from spatial autocorrelation was 0.1-20.5 m2at Back-Reef and 0.1-16.9 m2at Mid-Lagoon. Maximal extensions of the genets, in 19 × 30 m plots, were 19.2 m (median 7.5 m) and 10.8 m (median 4.8 m) at Back-Reef and Mid-Lagoon. There was no indication of deficit or excess of heterozygotes nor were coefficients of inbreeding (FIS) significant. The seedlings did not show statistically significant deficit of heterozygotes (except for 1 locus at Back-Reef). Contrary to our expectations, we did not find evidence of bi-parental inbreeding in this dioecious seagrass with large genets but small genetic neighborhoods. Proposed mechanisms to avoid bi-parental inbreeding are possible selection against homozygotes during fecundation or ovule development. Additionally, the genets grew highly dispersed (aggregation index Ac was 0.09 and 0.10 for Back-Reef and Mid-Lagoon, respectively); such highly dispersed guerrilla-like clonal growth form likely increases the probability of crossing between different potentially unrelated genets.
authors.affiliation: Instituto de Ciencias del Mar y Limnología Unidad Académica Sistemas Arrecifales-Puerto Morelos Universidad Nacional Autónoma de México Prolongación Niños Héroes S/N Puerto Morelos Quintana Roo México.
authors.forename: Brigitta Ine
authors.identifier: 0000-0002-6447-7479
authors.initials: BI
authors.lastname: Van Tussenbroek
authors.affiliation: Instituto de Ciencias del Mar y Limnología Unidad Académica Sistemas Arrecifales-Puerto Morelos Universidad Nacional Autónoma de México Prolongación Niños Héroes S/N Puerto Morelos Quintana Roo México.
authors.forename: Tania
authors.initials: T
authors.lastname: Valdivia-Carrillo
authors.affiliation: Instituto de Ciencias del Mar y Limnología Unidad Académica Sistemas Arrecifales-Puerto Morelos Universidad Nacional Autónoma de México Prolongación Niños Héroes S/N Puerto Morelos Quintana Roo México; Present address: Department of Life and Health Sciences University of North Texas at Dallas Dallas Texas.
authors.forename: Irene Teresa
authors.initials: IT
authors.lastname: Rodríguez-Virgen
authors.affiliation: Instituto de Ciencias del Mar y Limnología Unidad Académica Sistemas Arrecifales-Puerto Morelos Universidad Nacional Autónoma de México Prolongación Niños Héroes S/N Puerto Morelos Quintana Roo México.
authors.forename: Sylvia Nashieli Marisela
authors.initials: SN
authors.lastname: Sanabria-Alcaraz
authors.affiliation: Instituto de Ciencias del Mar y Limnología Unidad Académica Sistemas Arrecifales-Puerto Morelos Universidad Nacional Autónoma de México Prolongación Niños Héroes S/N Puerto Morelos Quintana Roo México; Facultad de Ciencias Laboratorio de Desarrollo de Plantas Ciudad Universitaria Universidad Nacional Autónoma de México Coyoacan Distrito Federal México.
authors.forename: Karina
authors.initials: K
authors.lastname: Jiménez-Durán
authors.affiliation: Instituto de Ciencias del Mar y Limnología Unidad Académica Sistemas Arrecifales-Puerto Morelos Universidad Nacional Autónoma de México Prolongación Niños Héroes S/N Puerto Morelos Quintana Roo México; Present address: School of Biological Science University of Adelaide Adelaide South Australia 5005 Australia.
authors.forename: Kor Jent
authors.initials: KJ
authors.lastname: Van Dijk
authors.affiliation: Facultad de Ciencias Laboratorio de Desarrollo de Plantas Ciudad Universitaria Universidad Nacional Autónoma de México Coyoacan Distrito Federal México.
authors.forename: Guadalupe Judith
authors.initials: GJ
authors.lastname: Marquez-Guzmán
keywords: Clonal growth; genetic neighborhood; genetic structure; hydrodynamics; hydrophily; mating system; microsatellite markers; seagrass