Biology subjects

Oliveras, I.

Publications and source records attributed to Oliveras, I..

4 recordsLinked to original sources

bioRxiv2023

Photosynthetic and water transport strategies of plants along a tropical forest aridity gradient: a test of optimality theory

(1) The research conducted, including the rationaleThe direct effect of aridity on photosynthetic and water-transport strategies is not easy to discern in global analyses because of large-scale correlations between precipitation and temperature. We analyze tree traits collected along an aridity gradient in Ghana, West Africa that shows little temperature variation, in an attempt to disentangle thermal and hydraulic influences on plant traits. (2) MethodsPredictions derived from optimality theory on the variation of key plant traits along the aridity gradient are tested with field measurements. (3) resultsMost photosynthetic traits show trends consistent with optimality-theory predictions, including higher photosynthetic capacity in the drier sites, and an association of higher photosynthetic capacity with greater respiration rates and greater water transport. Hydraulic traits show less consistency with theory or global-scale pattern, especially predictions based on xylem efficiency-safety tradeoff. Nonetheless, the link between photosynthesis and water transport still holds: species (predominantly deciduous species found in drier sites) with both higher sapwood-to-leaf area ratio (AS/AL) and potential hydraulic conductivity (Kp), implying higher transpiration, tend to have both higher photosynthetic capacity and lower leaf-internal CO2. (4) ConclusionsThese results indicate that aridity is an independent driver of spatial patterns of photosynthetic traits, while plants show a diversity of water-transport strategies along the aridity gradient. Plain language summaryAlong an aridity gradient in Ghana, West-Africa, we used optimality theory to explain that aridity is an important driver of photosynthetic traits, independent of temperature. Toward drier sites, plants have higher photosynthetic capacities per leaf area but have fewer leaves. We also explain how plants arrange water transportation to support quicker photosynthesis at drier sites. However, plants at the drier sites seem to have diverse combinations of hydraulic traits to satisfy the need for photosynthesis. We reported surprising data-theory inconsistency for some hydraulic traits along the aridity gradient where further research is needed.

ecology↗

bioRxiv2021

Tropical tree growth sensitivity to climate is driven by species intrinsic growth rate and leaf traits

A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long-term climate averages (mean climate) and short-term deviations from these averages (anomalies) both influence tree growth, but the rarity of long-term data integrating climatic gradients with tree censuses has so far limited our understanding of their respective role, especially in tropical systems. Here, we combined 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how tree growth responds to both climate means and anomalies, and how species functional traits mediate these tree growth responses to climate. We showed that short-term, anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast-growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both long-term and short-term climate variations. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests, and that species traits can be leveraged to understand these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.

ecology↗

bioRxiv2019

THE INFLUENCE OF ECOSYSTEM AND PHYLOGENY ON TROPICAL TREE CROWN SIZE AND SHAPE

1The sizes and shapes of tree crowns are of fundamental importance in ecology, yet understanding the forces that determine them remains elusive. A cardinal question facing ecologists is the degree to which general and non-specific versus ecological and context-dependent processes are responsible for shaping tree crowns. Here, we test this question for the first time across diverse tropical ecosystems. Using trees from 20 plots varying in elevation, precipitation, and ecosystem type (savanna-forest transitions) across the paleo- and neo-tropics, we test the relationship between crown dimensions and tree size. By analyzing these scaling relationships across environmental gradients, biogeographic regions, and phylogenetic distance, we extend Metabolic Scaling Theory (MST) predictions to include how local selective pressures shape variation in crown dimensions. Across all sites, we find strong agreement between mean trends and MST predictions for the scaling of crown size and shape, but large variation around the mean. While MST explained approximately half of the observed variation in tree crown dimensions, we find that local, ecosystem, and phylogenetic predictors account for the half of the residual variation. Crown scaling does not change significantly across regions, but does change across ecosystem types, where savanna tree crowns grow more quickly with tree size than forest tree crowns. Crowns of legumes were wider and larger than those of other taxa. Thus, while MST can accurately describe the central tendency of tree crown size, local ecological conditions and evolutionary history appear to modify the scaling of crown shape. Importantly, our extension of MST incorporating these differences accounts for the mechanisms driving variation in the scaling of crown dimensions across the tropics. These results are critical when scaling the function of individual trees to larger spatial scales or incorporating the size and shape of tree crowns in global biogeochemical models.

ecology↗

bioRxiv2018

Coping-Style Behaviour Identified by a Survey of Parent-of-Origin Effects in the Rat

We develop theory, based on earlier work, to partition heritability into a component due to a combination of parent of origin, maternal, paternal and shared environment, and another component that estimates classical additive genetic variance. We then investigate the effects on heritability of the parental origin of alleles in outbred heterogeneous stock rats across 199 complex traits. Parent-of-origin-like heritability was on average 2.7-fold larger than classical additive heritability. Among the phenotypes with the most enhanced parent-of-origin heritability were 10 coping style behaviors, with average 3.2-fold heritability enrichment. To confirm these findings on coping behaviour, and to eliminate the possibility that the parent of origin effects are due to confounding with shared environment, we performed a reciprocal F1 cross between the behaviourally divergent RHA and RLA rat strains. We observed parent-of-origin effects on F1 rat anxiety/coping-related behavior in the Elevated Zero Maze test. Our results are the first to assess genetic parent-of-origin effects in rats, and confirm earlier findings in mice that such effects influence mammalian coping and impulsive behavior.

genetics↗