1153 TAXON 67 (6) • December 2018: 1153–1162 Conceição & al. • Limonium intra- and interspecific hybridization Version of Record Article history: Received: 26 Jan 2018 | returned for (first) revision: 13 Aug 2018 | (last) revision received: 6 Nov 2018 | accepted: 12 Nov 2018 | published: online fast track, 27 Nov 2018; in print and online issues, 13 Dec 2018 || Associate Editor: Elvira Hörandl || © International Association for Plant Taxonomy (IAPT) 2018, all rights reserved INTRODUCTION The sea lavenders genus Limonium Mill. is represented by taxonomically complex groups generally characterized by sexual (selfing, outcrossing) and asexual reproduction (apo- mixis, agamospermy), hybridization among its members, and polyploidy (Erben, 1978). This genus is roughly characterized by perennial and annual herbs or dwarf shrubs, disposed in basal rosettes and usually with terminal panicles or corymbs as inflorescences (Erben, 1993; Kubitzki, 1993). Diverse ploidy, like diploid (e.g., L. ovalifolium (Poir.) Kuntze, 2n = 2x = 16), tetraploid (e.g., L. vulgare Mill., 2n = 4x = 36) or hexaploid (e.g., L. humile Mill., 2n = 6x = 54) levels occur in this genus (Ingrouille & Stace, 1986; Dawson & Ingrouille, 1995; Cowan & al., 1998; Cortinhas & al., 2015; Caperta & al., Limonium homoploid and heteroploid intra- and interspecific crosses unveil seed anomalies and neopolyploidy related to sexual and/or apomictic reproduction Sofia I.R. Conceição,1 Ana Sofia Róis1 , 2 & Ana D. Caperta1 1 Linking Landscape, Environment, Agriculture and Food (LEAF), Instituto Superior de Agronomia (ISA), Universidade de Lisboa, Tapada da Ajuda, 1349-017 Lisboa, Portugal 2 School of Psychology and Life Sciences, Universidade Lusófona de Humanidades e Tecnologias (ULHT), Campo Grande, 376, 1749-024 Lisboa, Portugal Author for correspondence: Ana D. Caperta, anadelaunay@isa.ulisboa.pt DOI https://doi.org/10.12705/676.11 Abstract Apomixis is a form of asexual reproduction that consists in cloning through seeds. In Limonium (Plumbaginaceae) species present a pollen–stigma dimorphism linked to a sporophytic self-incompatibility system associated with sexual and/ or apomictic reproductive modes. Previous work in other genera suggests that the emergence of apomixis is associated with hybridization and/or polyploidy. In this study, our goal was to test the ability of diploid and tetraploid species to hybridize and to evaluate the variate outcomes from these crosses. To achieve this, sexual diploid (L. nydeggeri, L. ovalifolium) and facultative apomict tetraploid (L. binervosum, L. dodartii) plants from cultivated material, previously cytogenetically and reproductively characterized, were used for experimental intra- and interspecific crosses. Genome sizes, ploidy levels and morphology were examined in the resulting progenies. Results showed a high production of viable seeds in particular in plants from tetraploid × diploid (heteroploid) crosses. In these crosses, some seedlings exhibited pleiocotyly (tricotyl, tetracotyl), while others showed polyembryony. In both homoploid (diploid × diploid) and heteroploid (tetraploid × diploid) crosses, most of the offspring plants were morphologically and in their ploidy similar to the female receiver, although some morphological abnormalities were found. Molecular progeny tests using the nrDNA ITS1-ITS2 sequence demonstrated an astounding range of diploid offspring plants originated from diploid × diploid crosses that were either genetically similar or distinct from parental plants. Although in intraspecific crosses most of the resulting progeny was diploid, one triploid plant was formed. Moreover, in homoploid interspecific crosses, neopolyploids (two tetraploid plants) were produced. Progeny plants from heteroploid crosses always showed nrDNA ITS1-ITS2 sequences identical to the parental plant used as female receiver. In conclusion, diploid homoploid crosses presented genetically diverse offspring arising from sexual reproduction. By contrast, heteroploid crosses generated clonal, maternal (apomictic) offspring. Keywords apomixis; genetic crossing; hybridization; neopolyploid; Plumbaginaceae; pleiocotyly; polyembryony Supplementary Material The Electronic Supplement (Tables S1–S3, Fig. S1) and DNA sequence alignments (used to compare parental and progeny plants of nine homoploid and/or interploid crosses) are available from https://doi.org/10.12705/676.11.S1 and https://doi.org/10.12705/676.11.S2, respectively. 2017). Triploid taxa are common in the Western Mediterranean (e.g., L. virgatum, 2n = 3x = 27) (Erben, 1993). A conspicuous feature of Limonium species is a pollen– stigma dimorphism linked to a sporophytic self-incompat- ibility system (Electr. Suppl.: Fig. S1) (Baker, 1966). Four possible combinations have been determined: (A) coarsely reticulate exine and cob-like stigmas; (B) finely reticulate exine and papillose stigmas; (C) finely reticulate exine and cob-like stigmas; and (D) coarsely reticulate exine and pap- illose stigmas. A and B represent self-incompatible combi- nations whereas C and D are self-compatible combinations (Baker, 1966). Although these latter two combinations are self-fertile, it was hypothesized that some polyploid species surpass this self-incompatibility system reproducing mainly by apomixis (Baker, 1966).