Unai López de Heredia

Vulnerability to cavitation, hydraulic efficiency, growth and survival in an insular pine (Pinus canariensis)

BACKGROUND AND AIMS It is widely accepted that hydraulic failure due to xylem embolism is a key factor contributing to drought-induced mortality in trees. In the present study, an attempt is made to disentangle phenotypic plasticity from genetic variation in hydraulic traits across the entire distribution area of a tree species to detect adaptation to local environments. METHODS A series of traits related to hydraulics (vulnerability to cavitation and hydraulic conductivity in branches), growth performance and leaf mass per area were assessed in eight Pinus canariensis populations growing in two common gardens under contrasting environments. In addition, the neutral genetic variability (FST) and the genetic differentiation of phenotypic variation (QST) were compared in order to identify the evolutionary forces acting on these traits. KEY RESULTS The variability for hydraulic traits was largely due to phenotypic plasticity. Nevertheless, the vulnerability to cavitation displayed a significant genetic variability (approx. 5 % of the explained variation), and a significant genetic × environment interaction (between 5 and 19 % of the explained variation). The strong correlation between vulnerability to cavitation and survival in the xeric common garden (r = -0·81; P < 0·05) suggests a role for the former in the adaptation to xeric environments. Populations from drier sites and higher temperature seasonality were less vulnerable to cavitation than those growing at mesic sites. No trade-off between xylem safety and efficiency was detected. QST of parameters of the vulnerability curve (0·365 for P50 and the slope of the vulnerability curve and 0·452 for P88) differed substantially from FST (0·091), indicating divergent selection. In contrast, genetic drift alone was found to be sufficient to explain patterns of differentiation for xylem efficiency and growth. CONCLUSIONS The ability of P. canariensis to inhabit a wide range of ecosystems seemed to be associated with high phenotypic plasticity and some degree of local adaptations of xylem and leaf traits. Resistance to cavitation conferred adaptive potential for this species to adapt successfully to xeric conditions.

Effect of canopy closure on pollen dispersal in a wind-pollinated species (Fagus sylvatica L.)

The effect of non-reproductive trees and saplings as a physical barrier to pollen dispersal in wind-pollinated species’ forests has not received enough attention in the literature so far. The neighborhood seedling model was used to fit pollen dispersal models for beech at different stages of gap recolonization and to elucidate the effect of saplings as a physical barrier on pollen dispersal at local scale. Phenological overlap of leaf emergence, and pollen release as well as wind directionality patterns were also examined. As a case study, we used a mixed beech-oak forest that was managed as open woodland until 1974. The ban on entry of cattle has led to the recolonization of empty spaces by seedlings and saplings of beech (Fagus sylvatica L.) and two oak species (Quercuspetraea (Matts.) Liebl. and Q. pyrenaica Willd.) and, at last, to canopy closure. The average pollen dispersal distance for the first plants that regenerated in the gaps was almost twice those found for recently installed seedlings and seeds collected in traps, supporting the hypothesis that the understory may act as a physical barrier to pollen dispersal. Although a substantial part of effective pollination directionality is at random, horizontal winds and vertical anabatic winds may explain some of this directionality. At the time of beech pollen release, leaves of beech and sessile oak are fully developed, enhancing pollen interception by the saplings. Explicit models of pollen dispersal for wind-pollinated trees should incorporate the effect of canopy closure caused by growth of saplings and account for leaf phenology of co-occurring species in the forest.

Variation components in leaf morphology of recruits of two hybridising oaks (Q. petraea (Matt.) Liebl. and Q. pyrenaica Willd.) at small spatial scale

Leaf morphological variation was examined in recruits of two hybridising oaks in a small sympatric area from Central Spain. Nuclear microsatellites were used to identify hybrids and assess the parental lineage. By Bayesian clustering analysis, 5% of hybrids were found. Principal component analysis was used to reduce 15 morphometric variables to four components associated with leaf size, lobation/pubescence and overall shape of the leaf. The percentage of variance due to genetic factors was evaluated through nested analysis of variance. As much as 70% of variance component was due to the factor “species” for lobation/pubescence, suggesting high adaptive value for these traits, possibly related to ecological constraints of the species. The genetic component of variance for leaf size and overall shape of the leaf was below 33%. Age and height of the recruits did not correlate with sun-leaf morphology. Competition indexes and diameter of the recruits showed slight, although significant, correlations with leaf size and lobation/pubescence components, pointing to some trade-offs between competition for light and leaf morphology of Q. petraea and Q. pyrenaica recruits.

Transcriptomic analysis of juvenile wood formation during the growing season in Pinus canariensis

Abstract A noticeable proportion of low transcribed genes involved in wood formation in conifers may have been missed in previous transcriptomic studies. This could be the case for genes related to less abundant cell types, such as axial parenchyma and resin ducts, and genes related to juvenile wood. In this study, two normalized libraries have been obtained from the cambial zone of young individuals of Pinus canariensis C. Sm. ex DC, a species in which such cells are comparatively abundant. These two libraries cover earlywood (EW) and latewood (LW) differentiation, and reads have been de novo meta-assembled into one transcriptome. A high number of previously undescribed genes have been found. The transcriptional profiles during the growing season have been analyzed and several noticeable differences with respect to previous studies have been found. This work contributes to a more complete picture of wood formation in conifers. The genes and their transcription profiles described here provide a useful molecular tool for further studies focused on relevant developmental issues, such as wound response and the formation of traumatic wood, re-sprouting, etc., presumably related to those cells.

NGScloud: RNA-seq analysis of non-model species using cloud computing

Summary RNA-seq analysis usually requires large computing infrastructures. NGScloud is a bioinformatic system developed to analyze RNA-seq data using the cloud computing services of Amazon that permit the access to ad hoc computing infrastructure scaled according to the complexity of the experiment, so its costs and times can be optimized. The application provides a user-friendly front-end to operate Amazons hardware resources, and to control a workflow of RNA-seq analysis oriented to non-model species, incorporating the cluster concept, which allows parallel runs of common RNA-seq analysis programs in several virtual machines for faster analysis. Availability and implementation NGScloud is freely available at https://github.com/GGFHF/NGScloud/. A manual detailing installation and how-to-use instructions is available with the distribution.

The Role of Hybridization on the Adaptive Potential of Mediterranean Sclerophyllous Oaks: The Case of the Quercus ilex x Q. suber Complex

Gene flow among closely related species is a not so unusual event, especially in plants. Hybridization and introgression have probably played a relevant role in the evolutionary history of the genus Quercus , for instance in the post-glacial northwards migration of European white oaks. In the same way, hybridization between the Mediterranean sclerophyllous oaks Q. ilex and Q. suber could have been determinant for the survival of the latter species during glaciations. In this chapter, evidences of the ancient introgression between these two species are revised, as well as estimations of current hybridization rates, which are very likely underrated. Pre-zygotic and post-zygotic limitations to introgression between Q. suber and Q. ilex are described. Finally, the effects of hybridization and introgression on cork quality, and the suitability of Q. ilex —Q. suber as a model system for the study of introgression and the maintenance/restoration of species boundaries within the genus are briefly discussed.