Phenotypic plasticity blurs ecotypic divergence in the response of Quercus coccifera and Pinus halepensis to water stress

Abstract

The Mediterranean evergreen woody plants Quercus coccifera and Pinus halepensis grow in a range of environments where selection by drought, heat and high irradiance can drive genetic and phenotypic diVerentiation of populations. However, the role of these stresses in Wltering out maladaptive genotypes remains unknown. We hypothesize that this Wltering is an important process for woody Mediterranean species due to their low phenotypic plasticity reported in previous studies. We have studied the response of saplings of Q. coccifera and P. halepensis, originating from two contrasting populations (a rock outcrop and a garrigue formation), to water stress. Isozyme characterization of genetic diversity was done to determine whether populations were genetically distinct. Water response analysis was based on water relations, gas exchange, chlorophyll a Xuorescence, pigment content, antioxidant status and morphological and structural parameters. Ecotypic diVerentiation was found for both Q. coccifera and P. halepensis populations, with a higher population isozyme similarity and a higher frequency of dominance of a few genotypes at the rock outcrop in both the species. P. halepensis exhibited small but signiWcant diVerences between populations for plastic responses to water, with lower phenotypic plasticity in saplings from the rock outcrop. Although it was not found in Q. coccifera, this pattern suggests that ecotypic diVerentiation rendering stress-tolerant ecotypes involves a decreased plasticity. Phenotypic plasticity was not high but it explained over 75% of the total variability among individual plants. Thus, and although evidence for ecotypic divergence was found in both the species, saplings were plastic enough to blur ecotypic diVerentiation.

The effect of genotype by environment interaction, phenotypic plasticity and adaptation on Pinus halepensis reforestation establishment under expected climate drifts

“…Regarding phenotypic plasticity, and according to RDPI range established by Valladares et al (2006), the tested Salzmann pine seed sources showed low phenotypic plasticity for both growth traits and survival, which concords with previous results of pine species such as Pinus halepensis (Baquedano et al, 2008) or on other Mediterranean species such as Quercus coccifera (Balaguer et al, 2001), Quercus robur and Fagus sylvatica (Valladares et al, 2000(Valladares et al, , 2002. Some traits might vary in their sensitivity to the environment being more plastic than others (Aitken et al, 2008;Benito-Garzón et al, 2011) as was the case in our experiment where height growth plasticity was higher than of that diameter among sites.…”

“…Height differed more among seed sources than diameter growth within each site. This can be explained by the fact that seedlings diameter, being frequently more sensitive to change in environmental conditions, is further fixed than height in establishing seedlings (Baquedano et al, 2008). However, there were specific differences among sites, with height growth being higher in Berga while in Xert diameter growth was the highest and height growth rates were the lowest.…”

Pine mortality in southeast Spain after an extreme dry and warm year: interactions among drought stress, carbohydrates and bark beetle attack

“…Similar observations have been made in semiarid regions of Turkey, Algeria and Morocco (Barbéro et al 1998;Pausas et al 2004). From a functional point of view, Pinus halepensis is considered not only a droughtavoider isohydric species with efficient stomatal control over water use (Baquedano et al 2008), but also a species that displays moderate resistance to the xylem embolism compared to other Pinus sp (Choat et al 2012).…”

Genetic variability in different growth forms of Dendrocalamus strictus: Deogun revisited

“…Such ecotype differentiation may be due to the long-term selection pressure that caused these populations to adapt to local environmental and edaphic conditions (Kawecki & Ebert 2004;Savolainen et al 2007). Such development of ecotypes due to the adaptational pressures of local climate and soil is also reported in other species such as Pinus taeda L. (Bongarten & Teskey 1986), Picea abies L. (Oleksyn 1998), Pinus sylvestris L. (Palmroth 1999), Fagus sylvatica L. (Müller-Stark 1997;Peuke 2002) and Quercus coccifera L. (Baquedano 2008). Soolanayakanahally et al (2009) found that species growing in wide geographical ranges showed great potential to acquire larger intraspecific variation in physiology, phenology, morphology and growth rate, which are clearly visible in case of these growth forms of D. strictus growing in different geographical locations.…”