Provisional methods to guide species‐specific seed transfer in ecological restoration

Abstract

Transferring plant material during ecological restoration has inherent risk. The use of seed transfer guidelines minimizes the possibility of introducing maladapted genotypes. We delineated biogeographic regions relevant to the distribution of Cercocarpus montanus for the purpose of creating provisional seed transfer zones for ecological restoration. We also modeled seed transfer guidelines using quantitative estimates of environmental tolerance and thresholds. Analyses identified broadscale environmental patterns relevant for seed transfer success. First, a species distribution model was used to identify the distribution of C. montanus. Next, we used non‐metric multidimensional scaling to investigate the structure of environmental data, and hierarchical cluster analysis to delineate biogeographic regions (i.e., environmental discontinuities) using species distribution data. Finally, we calculated measures of environmental tolerance and thresholds for C. montanus to model the probability of seed transfer success with multiple logistic regression. Biogeographic regionalization of C. montanus resulted in four major clusters, which agreed with ordination methods. Logistic regression was implemented using estimates of environmental tolerance and threshold data to model seed transfer success. We compared our species‐specific seed transfer zones and guidelines with other provisional seed transfer zone methods and found that our species‐specific methods performed better at explaining phenotypic variation of C. montanus in four out of six cases. Seed transfer zones are useful for restoration planning; however, zonal models fail to reflect much of the environmental heterogeneity present across the range of C. montanus. Continuous models for seed transfer success using environmental tolerance and thresholds enhance the development and use of seed transfer guidelines because they reflect landscape heterogeneity at a fine scale, and the results are relative to restoration sites of interest. Herein, we describe a methodology to construct provisional seed transfer zones and continuous seed transfer guidelines using species‐specific distribution models and multivariate analyses.

Pervasive admixture between eucalypt species has consequences for conservation and assisted migration

“…By using only locally adapted genotypes, managers may be restricting the ability of populations to survive under changing conditions. To address this issue, the definition of what constitutes the most appropriate geographic spread for seed collection to encompass a beneficial amount of genetic variation needs to be considered (Breed, Stead, Ottewell, Gardner, & Lowe, 2013;Crow, Albeke, Buerkle, & Hufford, 2018;Prober et al, 2015).…”

Importance of considering soils in seed transfer zone development: evidence from a study of the nativeBromus marginatus

“…, Crow et al. ). Thus, choices about method of defining zone boundaries, as well as the traits and environmental factors to assess, likely play a large role in the resulting spatial patterns of ecotypic variation.…”

“…To date, there is limited empirical research on the support for transfer zone boundaries developed using climate, and none for the degree of fitness increase generated by including soils. There are also a variety of methods that are used to define transfer zone boundaries (besides the ones we employed; e.g., Hamann et al 2011, Doherty et al 2017, Crow et al 2018. Thus, choices about method of defining zone boundaries, as well as the traits and environmental factors to assess, likely play a large role in the resulting spatial patterns of ecotypic variation.…”

Spatial decision‐support tools to guide restoration and seed‐sourcing in the Desert Southwest

“…While species distribution models provide insight into factors constraining species at their margins (Butterfield 2015, Crow et al 2018, common garden trials (Johnson et al 2012, Bansal et al 2015 or landscape genetics (Shryock et al 2015(Shryock et al , 2017 still represent the primary sources of data for identifying climatic drivers of population fitness and adaptive divergence. First, climate distances might be weighted by results from field trials to capture trends important to different species, functional groups, or geographic regions.…”

“…First, climate distances might be weighted by results from field trials to capture trends important to different species, functional groups, or geographic regions. While species distribution models provide insight into factors constraining species at their margins (Butterfield 2015, Crow et al 2018, common garden trials (Johnson et al 2012, Bansal et al 2015 or landscape genetics (Shryock et al 2015(Shryock et al , 2017 still represent the primary sources of data for identifying climatic drivers of population fitness and adaptive divergence. Linking field performance data with climate distances could allow transformation of the distance measures into units of fitness, thereby enabling direct predictions of performance loss with increasing climate distance.…”