Biology subjects

Goetz, A. R. B.

Publications and source records attributed to Goetz, A. R. B..

5 recordsLinked to original sources

bioRxiv2026

Canopy traits reveal climate-associated genetic differentiation in a California oak common garden

Background and Aims. Phenotypic variation in plant populations reflecting historical climate adaptation may affect performance under future climates. In long-lived trees, height and stem diameter are commonly used to assess growth, but these measures may not fully capture complementary structural and functional dimensions of performance, such as canopy development and vigor. We investigated whether canopy traits reveal climate-associated genetic differentiation in Quercus lobata. Methods. Using drone-based remote sensing of 1,395 12-year-old Quercus lobata trees from 601 families in a common garden, we quantified canopy volume and greenness, using the Normalized Difference Vegetation Index (NDVI). Previous analyses indicated that trees originating from warmer climates grew more in common gardens than those from cooler climates. To assess whether canopy traits showed similar patterns, we tested for family-level variation in each trait and associations with climate of origin. Key Results. Canopy volume and greenness showed significant genetic variation among families and significant associations with climate of origin. Trees from hotter climates had greater canopy volume and greenness than trees from cooler climates. Conclusions. These covarying traits provide novel evidence of climate-associated genetic differentiation in tree performance, consistent with historical climate selection. Trees originating from climates with hot summers, moderate winters, and low precipitation performed best in the garden, suggesting that they will perform better than trees adapted to cool, wet conditions under future climate change.

evolutionary biology↗

bioRxiv2026

Climate of origin constrains phenological tracking of temperature in a California endemic oak (Quercus lobata)

Premise of the study. Phenotypic plasticity is advantageous for many plants that experience environmental fluctuations, but strong selection pressures can establish limits to plasticity. In deciduous trees, the ability to time leaf elongation in response to spring temperatures can extend the length of the growing season for a given year's climate. However, emergence timing may have undergone strong selection by factors like cold temperatures, limiting the capacity of locally adapted populations to adjust via plasticity to new conditions. Methods. Using a nine-year dataset of 659 families of Quercus lobata in two common gardens, we tested how climate of origin and annual temperatures at the gardens affected variation in phenology. We then examined whether leaf emergence timing was under selection in the gardens by testing its effects on growth. Finally, we tested whether among-year plasticity in leaf emergence timing conferred a growth benefit. Key results. Year-to-year environmental variation explained more phenological variation than genetic differences associated with climate of origin, yet trees from cooler climates were more constrained in their ability to track temperature than trees from warmer climates. We found evidence of weak stabilizing and directional selection on phenology, suggesting that strong selection in favor of earlier phenology is unlikely. Finally, we found no evidence that selection has favored increased plasticity in Q. lobata. Conclusions. Phenological plasticity remains a key driver of plants' response to changing temperatures, but it is constrained by natural selection. As temperatures rise, these processes may disproportionately limit the ability of trees adapted to cooler climates to shift their phenology to match spring temperatures.

plant biology↗

bioRxiv2026

Persistent adaptational lag to climate threatens future tree populations, but phenotype-informed assisted gene flow can mitigate its effects

Maladaptation in foundational tree species can undermine ecosystem stability, but few studies have quantified its current magnitude or its consequences under ongoing climate change. Using a range-wide provenance test of valley oak (Quercus lobata), we tested whether historical climate warming has already produced temperature-driven climate-fitness mismatches, whether climatic extremes intensify these mismatches, and whether understanding these patterns can inform management. Growth and survival models from a 12-year common garden study revealed that trees performed best under summer temperatures cooler than their home climates, demonstrating persistent maladaptation to contemporary temperature maxima. This mismatch intensified during hotter years, indicating that climate variability amplifies fitness costs and that stressful years impose lasting effects. However, simulations of assisted gene flow showed that sourcing seeds from high-performing maternal families yields greater projected future performance than climate-matched sourcing across the species range. Together, these findings provide rare phenotypic evidence that maladaptation is already constraining a keystone tree species and show that phenotype-informed management can outperform climate-matched seed sourcing under further temperature increases.

ecology↗

bioRxiv2025

Current maladaptation increases with age in valley oak (Quercus lobata): Implications for future populations

Adaptation and maladaptation are two fundamental evolutionary processes shaping the success of tree populations. Local adaptation has been studied extensively, but maladaptation, which not simply be the inverse, is particularly important for long-lived species since human impact is changing the environment on a very short time scale. Because maladaptation may be observed at different stages of an organisms life cycle, temporal variation may reduce or enhance the vulnerability of a species to a new climate environment. In this paper, we use findings from an ongoing range-wide provenance study comprising two common gardens of 3,674 half-sib juvenile valley oaks (Quercus lobata) from 658 maternal families to address two objectives. First, we test whether maladaptation (a) persists as trees age and/or (b) varies in magnitude over time. We model growth rates and performance measures (height * survival; "performance") across families sourced from sites with differing climates. Second, we assess the extent to which evidence-based seed transfer can mitigate the impact of maladaptation. We find that the twelve-year-old trees are currently adapted to temperatures not only cooler than their home site, but also beyond the coolest limit of the current species range. Moreover, this maladaptive pattern is exacerbated in hotter years of our study. Despite a general pattern of maladaptation, we demonstrate the feasibility of using phenotype-informed seed transfer guidelines for replanting trees in current populations by identified high-performing individuals from varied environmental origins. Overall, our results indicate that valley oak is imperiled by current and future climate conditions, but high-performing trees well suited to sites across the species range can be identified as seed donors. We conclude that current maladaptation in a long-lived tree species is a major threat that is first apparent within a few years and worsens as trees age, but careful management of vulnerable oak populations can improve their resiliency.

evolutionary biology↗

bioRxiv2024

Maladaptive response of an endemic California oak to climatic warming is previewed by interannual variation in growth and survival

Climate change poses a major threat to long-lived tree populations by shifting environmental conditions away from those to which species are adapted. One of the biggest concerns is that individuals that are adapted to current conditions will become maladapted to new conditions due to a reduction in fitness. If tree populations are already maladapted to their current environments, climate change may put them at even greater risk. Valley oak (Quercus lobata), a foundational California endemic tree species, has already lost much of its range to anthropogenic activities and has been shown to demonstrate patterns of climatic maladaptation. Given the rapid pace of climate change, predicting the future of a species requires quantifying the extent to which contemporary populations are adapted or maladapted to current climates. Here, we tested the extent and variability of maladaptation in valley oak using a ten-year, range-wide provenance study of 3,371 half-sib juvenile trees from 658 maternal lineages. We compared growth rates and multiplicative fitness functions (height * survival; MFF) across families sourced from sites with differing climates relative to the gardens, as well as against annual phenological records. We found evidence that valley oak trees are most adapted to temperatures beyond the coolest limit of the current species range. Within and across years, trees sourced from hotter localities had higher growth and fitness in the gardens, and the relationship was more pronounced in hotter years. Trees showed persistent maladaptation after ten years, suggesting that the role of phenotypic plasticity in immediate environmental response is superseded by underlying genotypes. Finally, trees with earlier leaf phenology (associated with warmer source climates) consistently showed higher growth rates, further demonstrating a maladaptive pattern. Our results suggest that short-term variation in fitness shows immediate short-term response to climate warming, "previewing" a concerning range of species-level responses to increasing temperature.

evolutionary biology↗