A trait‒environment relationship approach in participatory plant breeding

Trait‒environment relationships are thought to be consistent or general across species and communities due to fundamental eco-physiological principles driving the interaction between individuals’ phenotypes and their environment. However, reported community-level trait‒environment relationships vary widely in strength and sign, and recent studies have shown that trait‒environment relationships can also vary across co-existing species. Here we refined the search for generality by evaluating whether trait‒environment relationships differ among genetically-homogeneous crop varieties, using carrot as a model species. This information will help guide selection methods and breeding programs to optimize crop attributes from an eco-evolutionary perspective. Work in progress.

Main collaborators: Marney E. Isaac

Complex trait‒environment relationships and the structure of Wisconsin forest plant communities

Adaptive relationships between traits and the environment are often inferred from observational data by regressing community-weighted mean (CWM) traits on environmental gradients. However, trait‒environment relationships are better understood as the outcome of trait‒abundance and environment‒abundance relationships, and the interaction between traits and the environment. Accounting for this functional structure and for interrelationships among traits should improve our ability to accurately describe general trait‒environment relationships. Using forest understory communities in Wisconsin, we applied a generalized mixed model (GLMM) incorporating this structure. We identified a simple hierarchy of trait‒environment relationships dominated by a strong positive effect of mean temperature on plant height. Compared to the traditional CWM approach, the GLMM was more conservative in identifying significant trait‒environment relationships, and also detected important relationships that CWM regressions overlooked. Results will be out soon.

Main collaborators: Caroline Tucker, Donald M. Waller

Beyond rectilinear functions linking traits with individual performance and species abundance

Functional traits have been largely regarded as “indicators” of plant function, i.e. whether they are positively or negatively correlated with individual performance. However, there are good ecological reasons to expect curved cross-species trait-performance and trait-abundance relationships. I tested this idea during my PhD working with annual desert annual plants. Results from two independent competition experiments showed (i) interactive effects of leaf size and specific leaf area (a curved response surface), (ii) optimum relationships for leaf size and leaf dry matter content (LDMC), and (iii) that LDMC can be as important as popular competitive traits. Field observations showed that trait selection was optimizing (stabilizing) and/or rectilinear (directional) when the environment was harshest (winter) while disruptive and/or directional when conditions were milder (summer). I believe that considering nonlinear relationships will help uncover hidden aspects of trait functionality that may in turn solve important current inconsistencies.

Main collaborators: Eduardo Pucheta

Ecology of desert annual plants

Much of what is known about desert annual plants comes from a few places in the world, primarily the Negev (Israel) and the deserts of North America (Mojave, Sonora, Chihuahua). Although the “Monte” is one of the largest deserts in the world, very little is known about its ecology in general and even less about its annual plants. I have conducted there my PhD. We have learned that water sheet flow is an important vector of seed dispersal into shrub understories (1). Shrubs tend to facilitate stress-intolerant species both in winter and in summer, whereas stress tolerant annuals dominate the open spaces between shrubs in summer (2). Trait selection is mostly stabilizing (convergent) in winter, when the environment is harshest, and it turns disruptive in summer, when conditions are milder (3).

Main collaborators: Eduardo Pucheta

Related publications:

(1) Rolhauser & Pucheta (2021) JVS

(2) Rolhauser & Pucheta (2017) JVS

(3) Rolhauser & Pucheta (2016) Ecology

Palm savanna vegetation ecology

Since 1965, El Palmar National Park (Argentina), protects the largest remnant of Butia yatay palm savanna, a species-rich ecosystem threatened by human activity. I have participated in several projects aimed at characterizing the heterogeneity of its vegetation and the distribution and dynamics of key plant species. We have learned that these endangered palm savannas undergo successional change due to woody encroachment triggered by cattle exclusion and maintained by scarcity of natural fires. Birds facilitate woody encroachment by dispersing seeds of gallery-forest trees.

Main collaborators: William B. Batista, Fernando Biganzoli