Plasticity, instability and canalization: is the phenotypic variation in seedlings of sclerophyll oaks consistent with the environmental unpredictability of Mediterranean ecosystems?

Abstract

Summary• Evergreen oaks from the Mediterranean basin exhibit a conservative resource-use strategy based on a reduced expression of phenotypic variation (i.e. canalization). We hypothesized that genetic variation across closely related species is more canalized than the response to environmental variation.• Seedlings of Quercus ilex and Q. coccifera , two important oak species from the Mediterranean basin that belong to the same subgenus and section, were grown in contrasted light and nutrient environments following a factorial design. Phenotypic variation was explored in a total of 75 variables including photosynthetic capacity, nutrient allocation, allometric relationships and crown architecture.• Path analysis showed that phenotypic variation was not significantly affected by differences between species but by those between and within environments, which are argued to be primarily linked to phenotypic plasticity and developmental instability, respectively. This finding is interpreted as evidence of genetic canalization across species.• The similar importance of plasticity and instability as sources of phenotypic variation and the high degree of genetic canalization are consistent with the expected role of the environmental unpredictability of Mediterranean ecosystems in shaping the developmental patterns of these two species.

Fine-scale spatial patterns of the Tertiary relict Zelkova abelicea (Ulmaceae) indicate possible processes contributing to its persistence to climate changes

“…Although the relationship between Z. abelicea and Q. coccifera is unknown at the moment, it may possibly be linked to the lower tolerance of Z. abelicea to dryness and disturbance, as compared to Q. coccifera. The latter is generally well known for its high degree of physiological and morphological plasticity (Valladares et al 2002). This hypothesis is also in support of the assumption of the supposed dependence of Z. abelicea on the ''hydraulic lift.''…”

Relationships between soil water repellency and microbial community composition under different plant species in a Mediterranean semiarid forest

“…1). This is not unusual in the Mediterranean region, where vegetation patterns exhibit a high spatial heterogeneity (Valladares et al, 2002) comprising a mixture of trees and shrubs that may interact. However, the patchy distribution of soil WR seems to influence the microbial community structure, including the prevalence of specific groups of microorganisms like actinobacteria, more than vegetation in our study.…”

Phenotypic plasticity is stronger than adaptative differentiation among Mediterranean stone pine provenances

“…On the contrary, other species of the subgenus Pinus have the vegetative phase change fixed at the end of the first or second growth season and would perish if the adult plant's resources demand exceeds environmental limitations (Klaus, 1989). The capacity of the stone pine to postpone the phase change in order to survive in limiting environments can thus be seen as an adaptative trait within a conservative resource use strategy, similar to delayed stem-growth patterns in the Canaries pine, pine species with grass stage or other lignotuberous plants, shaped by the environmental unpredictability of Mediterranean ecosystems (Valladares et al, 2002). Furthermore, after the phase change, the stone pine gradually loses also other juvenile traits, like the capacity to sprout adventitious juvenile shoots from needle axils, e.g.…”