Morphometric and molecular variation in concert: taxonomy and genetics of the reticulate Pyrenean and Iberian alpine spiny fescues (Festuca eskiacomplex, Poaceae)

Abstract

The Iberian mountain spiny fescues are a reticulate group of five diploid grass taxa consisting of three parental species and two putative hybrids: F. × souliei (F. eskia × F. quadriflora) and F. × picoeuropeana (F. eskia × F. gautieri). Phenotypic and molecular studies were conducted with the aim of determining the taxonomic boundaries and genetic relationships of the five taxa and disentangling the origins of the two hybrids. Statistical analyses of 31 selected phenotypic traits were conducted on individuals from 159 populations and on nine type specimens. Molecular analyses of random amplified polymorphic DNA (RAPD) markers were performed on 29 populations. The phenotypic analyses detected significant differences between the five taxa and demonstrated the overall intermediacy of the F. × picoeuropeana and F. × souliei between their respective parents. The RAPD analysis corroborated the genetic differentiation of F. eskia, F. gautieri and F. quadriflora and the intermediate nature of the two hybrids; however, they also detected genetic variation within F. × picoeuropeana. These results suggest distinct origins for F. × picoeuropeana in the Cantabrian and Pyrenean mountains, with the sporadic Pyrenean populations having potentially resulted from recent hybridizations and the stabilized Cantabrian ones from older events followed by potential displacements of the parents.

Past climate changes facilitated homoploid speciation in three mountain spiny fescues (Festuca, Poaceae)

“…Despite we have no data concerning the compatibility system of these fescues, they show grass features compatible with allogamy20 like those reported in many other fescues14. But the three species studied here are also pseudorrhizomatous plants, spreading primarily by asexual reproduction15, which can contribute to the persistence of their populations19. It implies that any hybrid generation could last over many years in the same area without any crossing, favoring its geographical isolation.…”

“…This pattern has been reported in other fescues23 and might also act as a barrier to hybridization in the fescues studied here. Asexual reproduction through pseudorrhizomes should also be considered a major isolation barrier between these fescues since seedlings are infrequent15.…”

“…Species are perennial rhizomatose grasses with a generation time of two or more years, reproducing very frequently by asexual reproduction (pseudorrhizomes). Species identity was determined following the criteria of15. Individuals were collected randomly with a minimum sampling distance of 10 m to avoid the sampling of relatives or ramets.…”

“…In this study, we assessed how climate has shaped the outcomes of hybridization in two species of spiny fescues ( Festuca L., Poaceae) where homoploid speciation was proposed to occur1415. The spiny fescue F. picoeuropeana Nava (2 n  = 2 x  = 14) was suggested to be of hybrid origin because of its intermediate morphology between its putative parents, F. eskia Ramond ex DC.…”

“…(2 n  = 2 x  = 14). The latter two species co-occur in several localities in the NE of Spain (Pyrenees) where they have presumably given rise to this hybrid1416 although they also spread in allopatry in other regions of the Iberian Peninsula (NW Cantabrian Mountains, F. eskia ; E Iberian Mountains, F. gautieri 15). However, there are several allopatric hybrid populations in NW of Spain (Cantabrian Mountains; Fig.…”