Rapid evolution in native plants cultivated for ecological restoration: not a general pattern

Abstract

The growing number of restoration projects worldwide increases the demand for seed material of native species. To meet this demand, seeds are often produced through large-scale cultivation on specialized farms, using wild-collected seeds as the original sources. However, during cultivation plants experience novel environmental conditions compared to those in natural populations, and there is a danger that the plants in cultivation are subject to unintended selection and lose their adaptation to natural habitats. Although the propagation methods are usually designed to maintain as much natural genetic diversity as possible, the effectiveness of these measures have never been tested. We obtained seeds of five common grassland species from one of the largest native seed producers in Germany. For each species, the seeds were from multiple generations of seed production. We used AFLP markers and a common garden experiment to test for genetic and phenotypic changes during cultivation of these plants. The molecular markers detected significant evolutionary changes in three out of the five species, and we found significant phenotypic changes in two species. The only species that showed substantial genetic and phenotypic changes was the short-lived and predominantly selfing Medicago lupulina, where in the other, mostly perennial and outcrossing species, the observed changes were mostly minor. Agricultural propagation of native seed materials for restoration can cause evolutionary changes, at least in some species. We recommend caution particularly in selfing and short-lived species, where evolution may happen faster and effects may thus be more severe. This article is protected by copyright. All rights reserved.

Mixing source populations increases genetic diversity of restored rare plant populations

“…In fact, adaptive genetic variation may have been lost during the production process because selective pressures in a nursery setting are rarely similar to those in the wild (Espeland et al ), although previous studies have shown that even plants cultivated over multiple generations can show regional variation (Bucharova et al ). Yet, because only one generation passed from wild collection to our nursery production bed, the likelihood that adaptive diversity was lost in our study system is lower than for annual selfing species produced over multiple generations (Nagel et al ).…”

“…Multiple steps in the production process have been identified where unintentional changes in diversity may occur (Basey et al ; Espeland et al ), but few have been investigated in real‐world settings, making it challenging to understand the likelihood and relative strength of potential genetic bottlenecks in the production process. The few studies available illustrate the impacts of different methods of collecting and cleaning wild‐collected seeds on the genetic diversity of produced material (Silen & Osterhaus ; Konnert & Ruetz ; Kettle et al ), and highlight the high potential for evolution over multiple generations, particularly in short‐lived selfing species relative to outcrossing perennial species (Nagel et al ). None have followed genetic diversity from multiple wild populations through the production and use of mixed‐source plant materials for reintroduction.…”

Collection and production of native seeds for ecological restoration

“…2–5) before the seed production plot needs to be reseeded with newly collected wild seeds (Gibson‐Roy et al ; Association of German Wild Seed and Wild Plant Producers ). When tested on five grassland species, this approach proved effective for maintaining the genetic diversity of four species out of five, mostly long‐lived and out‐breeding perennials, while for Medicago lupulina , a short‐lived, selfing perennial species, genetic and phenotypic drift was detected after five generations (Nagel et al ). Such studies and results suggest that these approaches are usually effective, but over time and where research and testing capacity are available, the number of generations recommended for cultivated production crops for different taxa (according to life form and reproductive strategies) should ideally be determined on a species by species and region by region basis.…”

Maximising the use of native seeds in restoration projects

“…Using AFLP markers and phenotypic characterisation, Nagel et al . () found that large‐scale propagation can indeed, in some species, cause evolutionary changes.…”