Disentangling plasticity of serotiny, a key adaptive trait in a Mediterranean conifer.
Serotiny, the maintenance of ripe seeds in closed fruits or cones until fire causes dehiscence, is a key adaptive trait of plants in fire-prone ecosystems, but knowledge of phenotypic plasticity for cone retention in woody plants is extremely scarce. On the basis of published literature and our field observations, we hypothesized that increased aridity might decrease the aerial seed bank as a plastic response, not necessarily adaptive.



We used a Pinus halepensis common garden replicated in three contrasted sites (mild, cold, and dry) to separate population differentiation from phenotypic plasticity of cone serotiny and canopy cone bank (CCB). Differences in growth among trees of the same provenance allowed us to include size effect as a proxy of ontogenetic age for the same chronological age of the trees.



Tree size had a strong negative effect on serotiny, but serotiny degree differed among trial sites even after accounting for size effects. As hypothesized, serotiny was lower at the harsh (dry and cold) sites compared with the mild site. Genetic variation for size-dependent cone serotiny and significant population × site interaction were confirmed, the latter implying different plasticity of serotiny among populations. Population differentiation for CCB showed an ecotypic trend, with positive correlation with temperature oscillation (continentality) and negative correlation with summer rainfall.



Growth-limiting environments exacerbated the precocious release of seeds, contrary to the ecotypic trend found for the aerial cone bank, suggesting a counter-gradient plasticity. This plastic response is potentially maladaptive under a scenario of frequent wildfires.
Department of Forest Ecology and Genetics. Forest Research Centre (INIA-CIFOR), Crta. A Coruña km 7.5, 28040 Madrid, Spain Sustainable Forest Management Research Institute (UVa-INIA).
Ruth C
RC
Martín-Sanz
Sustainable Forest Management Research Institute (UVa-INIA) IDForest-Biotecnología Forestal Aplicada, Calle Curtidores, 17 34004 Palencia, Spain.
Luis
L
Santos-Del-Blanco
Forest Resources Unit, Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Crta. de Montañana, 179 50080, Zaragoza, Spain.
Eduardo
E
Notivol
Department of Forest Ecology and Genetics. Forest Research Centre (INIA-CIFOR), Crta. A Coruña km 7.5, 28040 Madrid, Spain.
M Regina
MR
Chambel
Sustainable Forest Management Research Institute (UVa-INIA) Escuela Técnica Superior de Ingenierías Agrarias, Universidad de Valladolid. Avd. de Madrid 57 34004, Palencia, Spain.
Roberto
R
San-Martín
Department of Forest Ecology and Genetics. Forest Research Centre (INIA-CIFOR), Crta. A Coruña km 7.5, 28040 Madrid, Spain Sustainable Forest Management Research Institute (UVa-INIA) climent@inia.es.
José
J
Climent
D004777:Environment; D005390:Fires; D059647:Gene-Environment Interaction; D010641:Phenotype; D028223:Pinus / Q000235:genetics / Q000502:physiology*; D012098:Reproduction; D058614:Seed Dispersal
Pinaceae; Pinus halepensis; adaptation; canopy cone bank; counter-gradient plasticity; genotype–environment interaction; phenotypic plasticity; serotiny