How specialized is a soil specialist? Early life history responses of a rare Eriogonum to site‐level variation in volcanic soils

Abstract

PREMISE Understanding edaphic specialization is crucial for conserving rare plants that may need relocation due to habitat loss. Focusing on Eriogonum crosbyae, a rare soil specialist in the Great Basin of the United States, we asked how site‐level variation among volcanic soil outcrops affected plant growth and population distribution. METHODS We measured emergence, survival, size, and biomass allocation of E. crosbyae seedlings planted in soils collected from 42 outcrops of actual and potential habitat. We also measured phenotypic variation in the wild, documented abiotic and biotic components of E. crosbyae habitat, re‐surveyed Nevada populations, and evaluated occupancy changes over time. RESULTS Plants responded plastically to edaphic variation, growing larger and allocating relatively more to aboveground tissues in soils with greater nutrient availability and growing smaller in soils higher in copper in the field and the greenhouse. However, the chemical and physical soil properties we measured did not predict site occupancy, nor was plant phenotype in the greenhouse different when plants were grown in soils from sites with different occupation status. We observed occupation status reversals at five locations. CONCLUSIONS Eriogonum crosbyae performed well in soils formed on hydrothermally altered rocks that are inhospitable to many other plants. Extirpation/colonization events observed were consistent with metapopulation dynamics, which may partially explain the patchy distribution of E. crosbyae among outcrops of potential habitat. While soil properties did not predict site occupancy, early life stages showed sensitivity to soil variation, indicating that seedling dynamics may be important to consider for the conservation of this soil specialist.

Ecology of Eriogonum tiehmii, a rare soil specialist: Arthropod diversity, soil preferences, and demography

“…Further, within the relatively small area sampled at Rhyolite Ridge, we observed significant differences in a variety of soil characteristics between occupied and unoccupied sites; these differences, and the relative positions of sites in ordination space, were similar for both of the analytical methods we used. Lab-measured soil properties are not always useful for distinguishing site occupancy in rare species (McClinton et al, 2020;Wiser et al, 1998), and it is notable that we have done so here; this indicates that there is a unique envelope of soil conditions in which E. tiehmii can thrive.…”

“…Greenhouse soil preference experiment installation, monitoring, and harvesting Experimental methods broadly followed those of McClinton et al (2020). First, each field soil was sieved to 1.3 cm to remove large rocks, then combined in a 50/50 mixture with decomposed granite, using tarp rolling to ensure thorough soil mixing.…”

“…Such experiments can also help reveal the level of habitat specificity present in a species; for example, whether the species is specifically adapted, and therefore restricted, to its unique substrate, or whether it is merely stress‐tolerant, occupying harsh environments as, for example, a refuge from competition or climatic changes and might also do well in other, potentially more fertile sites (Madawala Weerasinghe et al, 2010). Taken together, this information can be useful for conservation planning, including understanding whether ex situ conservation methods might be possible or appropriate (Boisson et al, 2017; McClinton et al, 2020).…”

“…There may be few detectable chemical or physical distinctions between occupied habitat and unoccupied habitat, sample sizes for occupied locations can be very small, and metapopulation dynamics can pose challenges for identifying true “unoccupied” habitat (Delong & Gibson, 2012; Kleijn et al, 2008; Wiser et al, 1998). Thus, soil preference experiments, which use plant growth as an indicator of habitat suitability, can be useful for understanding the effects of soil variation on plant success at various life stages (Madawala Weerasinghe et al, 2010; McClinton et al, 2020; Palmiotto et al, 2004). Such experiments can also help reveal the level of habitat specificity present in a species; for example, whether the species is specifically adapted, and therefore restricted, to its unique substrate, or whether it is merely stress‐tolerant, occupying harsh environments as, for example, a refuge from competition or climatic changes and might also do well in other, potentially more fertile sites (Madawala Weerasinghe et al, 2010).…”

Genotyping‐by‐sequencing resolves relationships in Polygonaceae tribe Eriogoneae

“…obs.). Other edaphic specialist Eriogonum species can demonstrate substantial morphological variation across edaphic gradients (McClinton & al., 2020). Extensive hybridization and introgression can occur between congeners of other families on serpentine soils, and among their sympatric populations, and be detected in SNP datasets (Kay & al., 2018).…”