Sourcing native plants to support ecosystem function in different planting contexts

Abstract

Current guidance on sourcing native plants to support ecosystem function focuses on the high risk of failure when unsuitable material is used in ecological restoration. However, there is growing recognition that risks may be lower and rewards higher at highly disturbed sites isolated from remnant populations, especially when considering support for pollinators, wildlife, and other ecosystem functions. We developed the first decision support tool using expert opinion to assess suitability of different native plant sources, including horticultural cultivars, in two different planting contexts. We assessed the suitability of 761 sources for 72 commonly sold native species in two different planting contexts (small, isolated, highly disturbed sites vs. large, undisturbed sites near remnant populations). Information on genetic and adaptive backgrounds of sources was strikingly lacking, forcing us to exclude one-third of sources from our assessment. While only 3% of cultivars received high suitability scores for use in large, undisturbed sites near remnant populations, 52% received high suitability scores in small, isolated, highly disturbed sites. However, nearly 25% of cultivars had floral or leaf traits that differed from wild plants in ways that may compromise their ability to support pollinators and other wildlife. Forbs and cultivars lacking genetic diversity and source information were most likely to have altered traits. We recommend that native plant breeders and sellers work together to ensure ecosystem function, adaptation, and diversity information is available to consumers, that consumers request this information to drive demand, and that researchers further investigate how context influences risks and benefits of different sources. Implications for Practice• Most native plant sources available in the marketplace are cultivars that are typically unsuitable for ecological restoration efforts aimed at reestablishing diverse, self-sustaining populations. However, they may be appropriate in certain planting contexts, where the primary aim is to support pollinators, wildlife, and other ecosystem functions. Our structured decision-making tool is the first of its kind to allow users to assess benefits and risks of planting these sources in different contexts. • Information on adaptation, genetic diversity, and ecosystem function is lacking for a majority of native plant sources in the marketplace, particularly for cultivars. Native plant breeders and sellers should work together to ensure this information is available and consumers should ask for this information to help drive demand.Author contributions: EL, SJ completed the SDM tool and tested it with AK, KH, AN, TK; AW, AK created the dataset of source attributes; JZ analyzed and visualized the results; AK, AN, KH, DT, TK drafted and revised the manuscript; all coauthors edited the manuscript.

The Limits to Adaptation in Restored Ecosystems and How Management Can Help Overcome Them

“…In both cases, genetic diversity may be reduced compared to natural populations (e.g., Williams & Davis, 1996, but see Reynolds et al, 2012). In the case of commercial seed companies, little may be known about the origins or diversity of commercial populations (Kramer et al, 2019), but if the initial seed source was a small sampling of individuals (especially if from a small or inbred remnant population or other restored populations that may have experienced demographic bottlenecks during establishment), then genetic diversity may be substantially reduced compared to large natural populations. Many commercial seed sources are admixed populations resulting from initial collections from many natural populations within a region, which may help alleviate this potential Figure 1.…”

Eight generations of native seed cultivation reduces plant fitness relative to the wild progenitor population

“…However, it has been shown that cultivar plantings may fail to restore ecosystem function (reviewed in Kettenring et al, 2014 ; Lesica & Allendorf, 1999 ; White, 2016 ). For example, a recent meta‐analysis showed that almost 25% of studied non‐local cultivars differed for phenotypic traits, such as flower color, which may decrease their pollinator attraction or suitability (Kramer et al, 2019 ). Another study showed that native bees visited native plants more often than their “nativar” (native cultivar; White, 2016 ), which could undermine the long‐term stability of the restored population.…”

Seed Sourcing Strategies Considering Climate Change Forecasts: A Practical Test in Scots Pine

“…However, it is possible that some outbreeding depression might occur as a result of these new combinations [47,48]. Therefore we need to take these results with caution, as the context (early estimation under the climate change scenario, non-significant variation among provenances in survival) can hinder some of the advantages of these methods as proposed by different authors [7][8][9][10][11]. These methods can also have some risks in the conservation of the genetic resources of the species in the long term [49], and therefore we will need to show clear advantages over traditional methods to implement them at an operational scale in conditions like the ones tested in our study.…”

“…Selecting the most productive seed source for a given area has been a traditional approach by forest managers. At present, information on genetic variability and the predictions provided by climate change science enable different seed sourcing strategies to maximize the future adaptation and resilience of our forests [7][8][9][10][11]. Among the possible strategies, local, predicted, composite, admixture, and climate-adjusted seed sourcing have been widely promoted (see Materials and Methods for a detailed description).…”