Spatial grain of adaptation is much finer than ecoregional‐scale common gardens reveal

Abstract

Adaptive variation among plant populations must be known for effective conservation and restoration of imperiled species and predicting their responses to a changing climate. Common‐garden experiments, in which plants sourced from geographically distant populations are grown together such that genetic differences may be expressed, have provided much insight on adaptive variation. Common‐garden experiments also form the foundation for climate‐based seed‐transfer guidelines. However, the spatial scale at which population differentiation occurs is rarely addressed, leaving a critical information gap for parameterizing seed‐transfer guidelines and assessing species’ climate vulnerability. We asked whether adaptation was evident among populations of a foundational perennial within a single “empirical” seed‐transfer zone (based on previous common‐garden findings evaluating very distant populations) but different “provisional” seed zones (groupings of areas of similar climate and are not parameterized from common‐garden data). Seedlings from three populations originating from similar conditions within an intermediate elevation were planted into gardens nearby at the same elevation, or 250–450 m higher or lower in elevation and 0.4–25 km away. Substantial variation was observed between gardens in survival (ranging 2%–99%), foliar crown volume (7.8–22.6 dm3), and reproductive effort (0%–65%), but not among the three transplanted populations. The between garden variation was inversely related to climatic differences between the gardens and seed‐source populations, specifically the site differences in maximum–minimum annual temperatures. Results suggest that substantial site‐specificity in adaptation can occur at finer scales than is accounted for in empirical seed‐transfer guidance when the guidance is derived from broadscale common‐garden studies. Being within the same empirical seed zone, geographic unit, and even within 10 km distance may not qualify as “local” in the context of seed transfer. Moving forward, designing common‐garden experiments so that they allow for testing the scale of adaptation will help in translating the resulting seed‐transfer guidance to restoration projects.

Weather and distance to fire refugia limit landscape‐level occurrence of fungal disease in an exotic annual grass

“…While stand‐level epidemics and subsequent cheatgrass stand failure have been documented in some infrequent previous instances (Meyer et al., 2010, 2016), we did not observe any such events during the first 4 years post‐fire in our study system in or around the plots reported here or elsewhere in the region (>2,500 plots sampled in Germino et al., 2018, 2019; Applestein et al., 2018, or Davidson & Germino, 2020). Fewer than half of all cheatgrass individuals were infected in the majority of plots and fewer than 17% plots contained the highest infection levels (>75% of plants), across all years (Table 2).…”

Demography with drones: detecting growth and survival of shrubs with unoccupied aerial systems

“…During the first field census in 2015, there were 313 plants, with a subsequent mortality decline to 219 plants by the time of the second field census in 2019. The Soda common garden (43.300° N, 116.991° W, 38 m × 42 m, hereafter Soda garden) was a larger experiment established in 2015 (Davidson & Germino 2020). The Soda garden included 1365 plants with minimal subsequent mortality during 2019 and 2021 field censuses, containing 1217 and 1209 live plants, respectively.…”

“…While mediumresolution satellite products are increasingly used to forecast trajectories of sagebrush cover after disturbance (Simler-Williamson & Germino 2022;Zaiats et al 2023), the $30-m resolution of these products cannot represent individual sagebrush plants. For sagebrush, individual-level measurements are key, given high levels of between-plant genetic variation with relevance for local adaptation (Richardson & Chaney 2018;Davidson & Germino 2020), differences in recovery trajectories depending on individual plant sizes (Shriver et al 2019), and reliance on individual species, patch, and plant traits by vertebrate herbivore species of conservation concern (Frye et al 2013;Ulappa et al 2014;Fremgen-Tarantino et al 2020).…”

Near‐infrared spectroscopy aids ecological restoration by classifying variation of taxonomy and phenology of a native shrub

“…heritable plasticity; Nicotra et al 2010; Karban et al 2014; Richardson et al 2017). Given the genetic basis of these morphological traits, it is possible that sagebrush is adapted to local conditions, which should influence where seeds are collected for restoration efforts (Davidson & Germino 2020). Alongside the natural complexities, sagebrush‐dominated ecosystems have a convoluted history of management.…”