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Premise: Maternal effects have been demonstrated to affect offspring performance in many organisms, and in plants, seeds are important mediators of these effects. Some woody plant species maintain long‐lasting canopy seed banks as an adaptation to wildfires. Importantly, these seeds stored in serotinous cones are produced by the mother plant under varying ontogenetic and physiological conditions. Methods: We sampled the canopy seed bank of a highly serotinous population of Pinus pinaster to test whether maternal age and growth and the environmental conditions during each crop year affected seed mass and ultimately germination and early survival. After determining retrospectively the year of each seed cohort, we followed germination and early survival in a semi‐natural common garden. Results: Seed mass was related to maternal age and growth at the time of seed production; i.e., slow‐growing, older mothers had smaller seeds, and fast‐growing, young mothers had larger seeds, which could be interpreted either as a proxy of senescence or as a maternal strategy. Seed mass had a positive effect on germination success, but aside from differences in seed mass, maternal age had a negative effect and diameter had a positive effect on germination timing and subsequent survival. Conclusions: The results highlight the importance of maternal conditions combined with seed mass in shaping seedling establishment. Our findings open new insights in the offspring performance deriving from long‐term canopy seed banks, which may have high relevance for plant adaptation. [ABSTRACT FROM AUTHOR]

Serotiny is an important adaptation for plants in fire-prone environments. However, different mechanisms also induce the opening of serotinous cones in the absence of fire in variably serotinous species. Xeriscence -cone opening driven by dry and hot conditions- is considered to be mediated only by the external environment, but endogenous factors could also play a significant role. Using the variably serotinous Pinus halepensis as our model species, we determined the effects of cone age and scales density in cone opening, and using in-situ and ex-situ manipulative experiments we investigated the role of water availability in the opening of serotinous cones. We hypothesized that loss of connection between the cones and the branch through the peduncles or the absence of water supply could induce a faster cone opening. Results showed that older cones lost more water and opened at lower temperatures, with no influence of scales density. Both field and chamber manipulative experiments (using paired cones of the same whorl) confirmed that water intake through the peduncles affected significantly the pace of cone opening, such that lack of water supply speeded up cone dehiscence. However, this was true for weakly serotinous provenances—more common in this species—, while highly serotinous provenances were indifferent to this effect in the field test. All our results support that cone serotiny in P. halepensis involves the allocation of water to the cones, which is highly consistent with the previously observed environmental effects. Importantly, the existence of maintenance costs of serotinous cones has strong implications on the effects of climate change in the resilience of natural populations, via modifications of the canopy seed banks and recruitment after stand-replacing fires. Moreover, evolutionary models for serotiny in P. halepensis must take into account the significant contribution of maintenance costs to the complex interaction between genotype and the environment. [ABSTRACT FROM AUTHOR]

Background A central question for understanding the evolutionary responses of plant species to rapidly changing environments is the assessment of their potential for short-term (in one or a few generations) genetic change. In our study, we consider the case of Pinus pinaster Aiton (maritime pine), a widespread Mediterranean tree, and (i) test, under different experimental conditions (growth chamber and semi-natural), whether higher recruitment in the wild from the most successful mothers is due to better performance of their offspring; and (ii) evaluate genetic change in quantitative traits across generations at two different life stages (mature trees and seedlings) that are known to be under strong selection pressure in forest trees. Results Genetic control was high for most traits (h2 = 0.137-0.876) under the milder conditions of the growth chamber, but only for ontogenetic change (0.276), total height (0.415) and survival (0.719) under the more stressful semi-natural conditions. Significant phenotypic selection gradients were found in mature trees for traits related to seed quality (germination rate and number of empty seeds). Moreover, female relative reproductive success was significantly correlated with offspring performance for specific leaf area (SLA) in the growth chamber experiment, and stem mass fraction (SMF) in the experiment under semi-natural conditions, two adaptive traits related to abiotic stress-response in pines. Selection gradients based on genetic covariance of seedling traits and responses to selection at this stage involved traits related to biomass allocation (SMF) and growth (as decomposed by a Gompertz model) or delayed ontogenetic change, depending also on the testing environment. Conclusions Despite the evidence of microevolutionary change in adaptive traits in maritime pine, directional or disruptive changes are difficult to predict due to variable selection at different life stages and environments. At mature-tree stages, higher female effective reproductive success can be explained by differences in their production of offspring (due to seed quality) and, to a lesser extent, by seemingly better adapted seedlings. Selection gradients and responses to selection for seedlings also differed across experimental conditions. The distinct processes involved at the two life stages (mature trees or seedlings) together with environment-specific responses advice caution when predicting likely evolutionary responses to environmental change in Mediterranean forest trees. [ABSTRACT FROM AUTHOR]

Costs of reproduction lie at the core of basic ecological and evolutionary theories, and their existence is commonly invoked to explain adaptive processes. Despite their sheer importance, empirical evidence for the existence and quantification of costs of reproduction in tree species comes mostly from correlational studies, while more comprehensive approaches remain missing. Manipulative experiments are a preferred approach to study cost of reproduction, as they allow controlling for otherwise inherent confounding factors like size or genetic background., Here, we conducted a manipulative experiment in a Pinus halepensis common garden, removing developing cones from a group of trees and comparing growth and reproduction after treatment with a control group. We also estimated phenotypic and genetic correlations between reproductive and vegetative traits., Manipulated trees grew slightly more than control trees just after treatment, with just a transient, marginally non-significant difference. By contrast, larger differences were observed for the number of female cones initiated 1 year after treatment, with an increase of 70% more cones in the manipulated group. Phenotypic and genetic correlations showed that smaller trees invested a higher proportion of their resources in reproduction, compared with larger trees, which could be interpreted as an indirect evidence for costs of reproduction., Synthesis. This research showed a high impact of current reproduction on reproductive potential, even when not significant on vegetative growth. This has strong implications for how we understand adaptive strategies in forest trees and should encourage further interest on their still poorly known reproductive life-history traits. [ABSTRACT FROM AUTHOR]

Two strategies have evolved in understory trees in relation to light availability: maximization of light capture and shade tolerance. In the genus Acer, light capture is favored by a suite of traits maximizing twig thickness and leaf size and minimizing the density of branching in the crown. In contrast, shade tolerance is enhanced by minimizing crown area, crown volume, and total leaf area per unit height. Maples with polycyclic shoot growth (i.e., successive flushes of shoot growth separated by a resting phase within the same vegetative period) may benefit from the prolonged growth by growing more and increasing total leaf area; thus we hypothesize that polycyclism is evolutionarily correlated with the suite of traits related to light capture. We tested this hypothesis using different phylogenetic trees to explore correlations between polycyclism and both suites of traits. Polycyclism was correlated with the suite of traits maximizing light capture, suggesting that polycyclic maples are ‘optimists’ (i.e., they make vigorous vertical extensions in rich light) and monocyclic maples are ‘pessimists’ (i.e., they wait in the dark understory until a gap is opened). Both strategies have been described for different floras, and interestingly, polycyclic species recruit over a wider range of environments than the monocyclic species. [ABSTRACT FROM AUTHOR]