The role of seed traits as segregation factors of hybrids in wild populations ofCistus(Cistaceae)

Abstract

Hybridization has been postulated as a main speciation mechanism in Cistus, a hard-seeded group of plants widely distributed in fire-prone Mediterranean shrublands. However, ecological evidence about how the segregation of hybrids from parents might occur is nonexistent. The presence of two hybrid populations in Morocco and Spain from Cistus albidus and Cistus heterophyllus led us to investigate their seed trait differences (seed size, mass and coat thickness) with the parentals and their seed germinability. A sowing experiment to compare the seedling emergence ability and seedling fitness of hybrids and their parentals was also carried out. Hybrid seeds germinated in a similar proportion to those of the parents. The hybrid seeds were significantly lighter, smaller and had thinner seed coats in both populations. However, these seed trait differences did not affect the seedling fitness of hybrids. These results were interpreted as a successful shift in the regeneration niche of the hybrids due to a greater proportion of soft-coated seeds, able to emerge from the soil seed bank in absence of fire. Smaller seeds also would favour further and deeper seed dispersal to escape from a fire. Monitoring of the seed yield of the Spanish population showed a competitive ability of hybrids.

An efficient protocol for Cistus crispus L. (Cistaceae) micropropagation

“…This could also reduce the genetic introgression from other similar species that can hybridise with C. crispus. This is particularly important when considering that diversification in Cistus depends on the geographical isolation between the species (Fernández-Mazuecos and Vargas, 2011;Navarro-Cano et al, 2017).…”

“…Such a condition does not allow C. crispus to easily renew and can have drawback for repopulating the plant community, especially if considering that such a species is also collected for ornamental purposes. This calls for a genetic and environmental protection of this species through adoption of ad hoc conservation practices, especially if considering its rarity and that Cistus species can undergo hybridisation with non-native species from the same genus (Navarro-Cano et al, 2017). Such measures of propagation should rely on both sexuate and asexuate reproduction methods to conserve the intraspecific variability and increase the number of individuals available for ornamental purposes and to recolonise the native areas.…”

Obtención de material vegetal de reproducción de Cistus heterophyllus carthaginensis (Cistaceae), especie catalogada En Peligro de Extinción en la Comunidad Valenciana (España)

“…Respecto a la caracterización de las dimensiones y pesos de las semillas obtenidas mediante los cruzamientos se ha seguido la metodología expuesta por Navarro-Cano et al (2017).…”