Relación entre variación fenotípica y éxito reproductor en "Olea europaea"

El objetivo general de la presente memoria doctoral es estudiar la relación entre la variación fenotípica en el acebuche (Olea europaea L.) y el éxito reproductor de sus individuos. Mediante una aproximación a tres escalas (intra-individual, inter-individual e interpoblacional) se busca valorar la importancia en la variación fenotípica de: a) la modularidad; b) la plasticidad fenotípica; c) la ontogenia; d) la diferenciación (genética) entre individuos y poblaciones; y e) el ambiente local y regional. A continuación, se pretende investigar cómo esa variación fenotípica se relaciona con la capacidad de captación de recursos y el funcionamiento reproductivo de los distintos individuos

Does the order of copulation matter? Experimental paternity analyses in the earthworm Hormogaster elisae (Annelida: Hormogastridae)

Multiple mating and sperm storage organs allow postcopulatory sexual selection to occur. This is the first time that a paternity test has been performed in an earthworm species. Microsatellite markers are used in Hormogaster elisae to trace paternity for multiple sires. Multiple paternity was detected in some cases, showing sperm mixture even within one cocoon, suggesting the eventual mixture of the allosperm within the spermathecae. Order of copulation influences paternity, the first (P1) and third partner (P3) being the most successful. Interestingly the second partner (P2) almost lacks paternity. The most plausible hypothesis suggests the existence of sperm displacement by flushing out older sperm once the spermathecae are full, which seems to occur when they contain sperm from two partners and P3 donates. At that moment sperm is still stratified thus removing sperm from P2. Afterwards sperm from P1 and P3 would be mixed provoking an equivalent paternity. Given the endogeic nature of the earthworm, copulation was not observed, making the lack of copulation with P2 (due to the need of a recovery time) or copulation without sperm transfer (due to low sperm production rate) possible alternative hypotheses. The weight of the earthworms is related to the number of cocoons they produce but not to their viability, which in all the cases was low, probably due to laboratory conditions. The sperm was kept viable inside the spermathecae for a maximum of two years and three months, suggesting a very effective nourishment system in the epithelium of the storage structures

Does the order of copulation matter? Experimental paternity analyses in the earthworm Hormogaster elisae (Annelida: Hormogastridae)

Multiple mating and sperm storage organs allow postcopulatory sexual selection to occur. This is the first time that a paternity test has been performed in an earthworm species. Microsatellite markers are used in Hormogaster elisae to trace paternity for multiple sires. Multiple paternity was detected in some cases, showing sperm mixture even within one cocoon, suggesting the eventual mixture of the allosperm within the spermathecae. Order of copulation influences paternity, the first (P1) and third partner (P3) being the most successful. Interestingly the second partner (P2) almost lacks paternity. The most plausible hypothesis suggests the existence of sperm displacement by flushing out older sperm once the spermathecae are full, which seems to occur when they contain sperm from two partners and P3 donates. At that moment sperm is still stratified thus removing sperm from P2. Afterwards sperm from P1 and P3 would be mixed provoking an equivalent paternity. Given the endogeic nature of the earthworm, copulation was not observed, making the lack of copulation with P2 (due to the need of a recovery time) or copulation without sperm transfer (due to low sperm production rate) possible alternative hypotheses. The weight of the earthworms is related to the number of cocoons they produce but not to their viability, which in all the cases was low, probably due to laboratory conditions. The sperm was kept viable inside the spermathecae for a maximum of two years and three months, suggesting a very effective nourishment system in the epithelium of the storage structures

The expression of light-related leaf functional traits depends on the location of individual leaves within the crown of isolated Olea europaea trees

Background: The spatial arrangement and expression of foliar syndromes within tree crowns can reflect the coupling between crown form and function in a given environment. Isolated trees subjected to high irradiance and concomitant stress may adjust leaf phenotypes to cope with environmental gradients that are heterogeneous in space and time within the tree crown. The distinct expression of leaf phenotypes among crown positions could lead to complementary patterns in light interception at the crown scale. Methods: We quantified eight light-related leaf traits across 12 crown positions of ten isolated Olea europaea trees in the field. Specifically, we investigated whether the phenotypic expression of foliar traits differed among crown sectors and layers and five periods of the day from sunrise to sunset. We investigated the consequences in terms of the exposed area of the leaves at the tree scale during a single day. Key Results: All traits differed among crown positions except the length-to-width ratio of the leaves. We found a strong complementarity in the patterns of the potential exposed area of the leaves among day periods as a result of a non-random distribution of leaf angles across the crown. Leaf exposure at the outer layer was below 60 % of the displayed surface, reaching maximum interception during morning periods. Daily interception increased towards the inner layer, achieving consecutive maximization from east to west positions within the crown, matching the sun’s trajectory. Conclusions: The expression of leaf traits within isolated trees of O. europaea varies continuously through the crown in a gradient of leaf morphotypes and leaf angles depending on the exposure and location of individual leaves. The distribution of light-related traits within the crown and the complementarity in the potential exposure patterns of the leaves during the day challenges the assumption of low trait variability within individuals

Intraindividual variation in light-related functional traits: magnitude and structure of leaf trait variability across global scales in Olea europaea trees

Intraspecific variation in leaf functional traits can play a crucial role at multiple ecological scales. However, our understanding of leaf functional trait variation (FV) across spatial scales is limited. Moreover, the influence of FV in specific responses to the environment remains poorly assessed. We investigated FV across multiple nested ecological scales in a set of leaf traits related to light interception and photosynthetic performance in eight populations of Olea europaea trees distributed over a wide latitudinal gradient (~60°). Specifically, we measured SLA, leaf shape, leaf’s spatial position (leaf angles) and leaf’s potential exposure to direct sunlight (silhouette area of the leaf blade and silhouette to area ratio of the leaf blade). The variability in leaf traits revealed two main patterns depending on the considered trait. Differences among sites absorbed >50% of the trait variation related to leaf shape and structure. Conversely, traits related to leaf position and exposure to direct light varied mostly within individuals among crown positions. The variation within trees for multiple traits ranged from 4 to 14%. Trees of equatorial populations had wider, thinner and more exposed leaves to direct light than trees of the remaining populations. The FV for multiple leaf traits at the tree scale was spatially structured within the tree crown and was higher for populations at the equator than for populations located in other latitudes. The differences among traits and scales in the magnitude of FV revealed a complex structure that could be linked to local adaptation

Field patterns of temporal variations in the light environment within the crowns of a Mediterranean evergreen tree (Olea europaea)

The light environment within a tree crown can be characterized by specific variation patterns arising from the structural features of the crown. Within-crown light variation patterns can be important for plant productivity, but this has yet to be assessed in natural settings. The spatio-temporal variations of direct and diffuse photosynthetic photon flux density (PPFD), their proportions and sunfleck frequency within the crowns of isolated adult wild olive trees (Olea europaea L.) were investigated. Trees growing in contrasting Mediterranean conditions (continental vs. coastal) at the same latitude were compared. Instantaneous diffuse and total PPFD were measured with sunshine sensors in three crown layers (outer-, middle- and inner-crown) in the south-facing part of the crown, at two points of the diurnal (mid-morning and midday) and seasonal (summer and winter) cycles. Direct PPFD and the proportion of direct to total PPFD vary diurnally within the crown as a result of an increase in sunfleck requency during midday and in self-shading during mid-morning, in both summer and winter conditions. Conversely, the lack of seasonal variation in the three light attributes is better explained by a greater average crown transmittance in winter conditions. The interplay between crown architecture heterogeneity and varying solar position renders identifiable patterns of temporal variations in the light environment within tree crowns. These patterns suggest that trees can benefit from the light heterogeneity typical of Mediterranean environments by developing conservative architectural layouts

Simplifying data acquisition in plant canopies- Measurements of leaf angles with a cell phone

1.Canopies are complex multilayered structures comprising individual plant crowns exposing a multifaceted surface area to sunlight. Foliage arrangement and properties are the main mediators of canopy functions. Theleaves act as light traps whose exposure to sunlight varies with time of the day, date and latitude in a trade-off between photosynthetic light harvesting and excessive or photoinhibitory light avoidance. To date, ecological research based upon leaf sampling has been limited by the available technology, with which data acquisition becomes labour intensive and time-consuming, given the overwhelming number of leaves involved. 2. In the present study, our goal involved developing a tool capable of measuring a sufficient number of leaves to enable analysis of leaf populations, tree crowns and canopies. We specifically tested whether a cell phone working as a 3D pointer could yield reliable, repeatable and valid leaf angle measurements with a simple gesture. We eval-uated the accuracy of this method under controlled conditions, using a 3D digitizer, and we compared perfor-mance in the field with the methods commonly used. We presented an equation to estimate the potential proportion of the leaf exposed to direct sunlight (SAL) at any given time and compared the results with those obtained by means of a graphical method. 3.We found a strong and highly significant correlation between the graphical methods and the equation presented. The calibration process showed a strong correlation between the results derived from the two methods with a mean relative difference below 10%. The mean relative difference in calculation of instantaneous exposure was below 5%. Our device performed equally well in diverse locations, in which we characterized over 700 leaves in a single day. 4.The new method, involving the use of a cell phone, is much more effective than the traditional methods or digitizers when the goal is to scale up from leaf position to performance of leaf populations, tree crowns or canopies. Our methodology constitutes an affordable and valuable tool within which to frame a wide range of ecological hypotheses and to support canopy modelling approaches