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Hybrids and Hybridization

Villa Machío, Irene [1], Heuertz, Myriam [2], Álvarez, Inés [3], Nieto Feliner, Gonzalo [4].

Examining the evolutionary fate of specific introgression events within syngameons: Armeria pungens (Plumbaginaceae).

Natural hybridization does not occur randomly across the living world, even within plants, but instead concentrates on certain lineages. Some of these lineages might thus fit the old syngameon concept -a group of otherwise distinct species interconnected by limited gene exchange-, which has been rescued in the last years following considerable molecular and genomic evidence. Hybridization propensity within a syngameon, however, is not uniform across species and, in addition to hybrid populations with no evolutionary trajectory, syngameons may contain introgressed successful populations or even hybrid species. This poses the question of which genetic, ecological, demographic, reproductive and biogeographic factors determine the viability and evolutionary fate of hybridization events. Fitness of introgressed individuals, adaptive value of introgressed loci, genetic divergence and incompatibilities between hybridizing populations, as well as demographic and spatial characteristics of the hybridizing site no doubt play a role. Focusing on a natural site where ongoing introgression occurs -thus early-generation hybrid products- is a suitable frame for examining this problem, especially when hybrid species or persisting products of old hybridization events exist in the syngameon in question. Armeria (Plumbaginaceae), a primarily Mediterranean genus, is one of such syngameons where hybridization and introgression have been documented at micro and macroevolutionary levels and weakness of reproductive barriers tested with artificial crosses. This study focuses on the southernmost population of a coastal sand-dune Iberian-Corsica-Sardinian species (Armeria pungens), which is introgressed by a sympatric congener (A. macrophylla). Introgression has been analyzed in 155 samples of both species distributed along 35 km in a southern Iberian site using SNP data from a Genotyping-by-Sequencing approach. NeighborNet and PCA analyses showed introgression between these species. Evidence from other analyses, including genetic clustering (Structure and NewHybrids), nucleotide diversity, heterozygosity and fixation indices as well as Bayesian genomic cline analyses, in addition to morphometric analyses, are consistent with asymmetric introgression, occurring mostly from A. macrophylla to A. pungens. The origin of the introgressed population and its determinant factors are explored by reconstructing its demographic history, together with that of the two parentals, with coalescent simulations, as well as exploring genotype-environment associations and selection gradients, with latent factor mixed models and redundancy analysis, as well as spatial PCA.

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1 - Real Jardin Botanico de Madrid-CSIC, Biodiversity and Conservation, Plaza de Murillo, 2, Madrid, Madrid, 28014, Spain
2 - INRAE, Univ. Bordeaux, Biogeco, 69 route d'Arcachon, Cestas, 33610, France
3 - Real Jardin Botanico de Madrid-CSIC, Biodiversity and Conservation, Plaza de Murillo, 2, Madrid, Madrid, 28014, España
4 - Real Jadrín Botánico de Madrid-CSIC, Biodiversity and conservation, Plaza de Murillo, 2, Madrid, Madrid, 28014, España

Introgressive hybridization
Population genomics
Armeria (Plumbaginaceae).

Presentation Type: Oral Paper
Session: HH1, Hybrids and Hybridization I
Location: /
Date: Wednesday, July 21st, 2021
Time: 10:00 AM(EDT)
Number: HH1001
Abstract ID:546
Candidate for Awards:None

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