Genetic diversity,genetic structure and phylogeography of the Iberian endemic Gypsophila struthium (Caryophyllaceae) as revealed by AFLP and plastid DNA sequences: connecting habitat fragmentation and diversification

Iberian gypsum outcrops are highly fragmented and ecologically challenging environments for plant colonization. As gypsophytes occur exclusively in such habitats, they are ideal models for the study of both the effects of habitat fragmentation and selection on population genetic diversity and structure. In this study, we used amplified fragment length polymorphism (AFLP) and plastid DNA sequences to investigate the phylogeographical history of the Iberian plant Gypsophila struthium (Caryophyllaceae), a widespread endemic restricted to Iberian gypsum outcrops. Gypsophila struthium consists of two subspecies that differ in the architecture of their inflorescence and have mostly allopatric ranges. Gypsophila struthium subsp. struthium occurs in central, eastern and south‐eastern Iberia, whereas G. struthium subsp. hispanica occurs in northern and eastern areas. AFLPs revealed low but significant genetic differentiation between the subspecies, probably as a result of a recent diversification during the Pliocene–Pleistocene. In the geographical contact zone between the taxa, the Bayesian analyses revealed populations with mixed ancestries and genetic clusters predominantly of one or the other subspecies, indicating incomplete reproductive barriers between them. Plastid DNA haplotypes revealed strong geographical structure and testified to processes of isolation by distance and continuous range expansion for some haplotype clades. The Bayesian analyses of the population structure of AFLP data and nested clade phylogeographical analysis (NCPA) of plastid haplotypes revealed that the putative ancestral range corresponded to central and eastern populations of G. struthium subsp. struthium, with those lineages contributing through more recent expansion to increased genetic diversity and structure of the south‐eastern and eastern ranges of this subspecies and to the diversification of G. struthium subsp. hispanica in northern and eastern gypsum outcrops. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 654–675.     

Among-population variation and plasticity to drought of Atlantic,Mediterranean, and interprovenance hybrid populations of maritime pine

Maritime pine grows naturally under a wide range of climatic conditions, from strongly Atlantic to strongly Mediterranean. Aiming to improve our understanding of the genetic structure and inheritance of drought resistance strategies in the species, we conducted an environmentally controlled experiment to assess the genetic variation and plasticity to drought of Atlantic and Mediterranean populations, and the interprovenance hybrids between them. Hybridization could also help to provide new genetic material for use in transitional areas between the two regions, for which reproductive materials of good quality are generally lacking. Plastic responses to water stress appeared to be highly conserved among populations, with a common conservative isohydric strategy based on promoting growth when water was abundant, and stopping it when water became limiting. We found, however, a strong intraspecific variation in biomass allocation patterns. The Atlantic populations showed a risky growth-based strategy with a larger amount of juvenile needles, whereas Mediterranean populations showed a more conservative strategy, minimizing aerial growth and increasing the proportion of adult needles that is more resistant to water loss. Hybrid populations performed more similarly to the Mediterranean parent, suggesting a dominance of the Mediterranean-like characteristics. Some of the tested hybrid populations, however, combined high growth with traits of drought adaptation, and thus represent potentially interesting materials for use in transitional regions between the two climate zones.