Theory predicts, and recent empirical studies have shown, that the diversity of plant species determines the diversity of associated herbivores and mediates ecosystem processes, such as aboveground net primary productivity (ANPP). However, an often-overlooked component of plant diversity, namely population genotypic diversity, may also have wide-ranging effects on community structure and ecosystem processes. We showed experimentally that increasing population genotypic diversity in a dominant old-field plant species, Solidago altissima, determined arthropod diversity and community structure and increased ANPP. The effects of genotypic diversity on arthropod diversity and ANPP were comparable to the effects of plant species diversity measured in other studies.

Supporting Online Material for Plant Genotypic Diversity Predicts Community Structure and Governs an Ecosystem Process

It remains unclear whether biodiversity buffers ecosystems against climate extremes, which are becoming increasingly frequent worldwide. Early results suggested that the ecosystem productivity of diverse grassland plant communities was more resistant, changing less during drought, and more resilient, recovering more quickly after drought, than that of depauperate communities. However, subsequent experimental tests produced mixed results. Here we use data from 46 experiments that manipulated grassland plant diversity to test whether biodiversity provides resistance during and resilience after climate events. We show that biodiversity increased ecosystem resistance for a broad range of climate events, including wet or dry, moderate or extreme, and brief or prolonged events. Across all studies and climate events, the productivity of low-diversity communities with one or two species changed by approximately 50% during climate events, whereas that of high-diversity communities with 16–32 species was more resistant, changing by only approximately 25%. By a year after each climate event, ecosystem productivity had often fully recovered, or overshot, normal levels of productivity in both high- and low-diversity communities, leading to no detectable dependence of ecosystem resilience on biodiversity. Our results suggest that biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events. Anthropogenic environmental changes that drive biodiversity loss thus seem likely to decrease ecosystem stability, and restoration of biodiversity to increase it, mainly by changing the resistance of ecosystem productivity to climate events.

Biodiversity increases the resistance of ecosystem productivity to climate extremes

Introduction. Ecologically Meaningful Germination Studies. Types of Seed Dormancy. Germination Ecology of Seeds with Nondeep Physiological Dormancy. Germination Ecology of Seeds with Morphophysiological Dormancy. Germination Ecology of Seeds with Physical Dormancy. Germination Ecology of Seeds in the Persistent Seed Bank. Causes of Within-Species Variations in Seed Dormancy and Germination Characteristics. A Geographical Perspective on Germination Ecology: Tropical and Subtropical Zones. A Geographical Perspective on Germination Ecology: Temperate and Arctic Zones. Germination Ecology of Plants with Specialized Life Cycles and/or Habitats. Biogeographical and Evolutionary Aspects of Seed Dormancy. Subject Index.

A Definitive Book on Seed Ecology@@@Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination

Ex-situ conservation is widely used to protect wild plant species from extinction. However, it remains unclear how genetic variation of ex-situ plant collections reflects wild source population diversity. Here, we conduct a global meta-analysis of the genetic representativeness of ex-situ populations by comparing genetic diversity (i.e. AR, allelic richness; HE , expected heterozygosity; PPB, percentage polymorphic bands; and SWI, Shannon-Winner index), inbreeding coefficient (FIS ), and genetic differentiation between ex-situ plant collections and their wild source populations. Genetic diversity (i.e., HE , PPB, and SWI) was significantly lower in ex-situ populations than their wild source populations, while genetic differentiation between ex-situ and wild populations (ex-situ-wild FST ), but not that among ex-situ populations, was significantly higher than among wild populations. Outcrossing species, but not those with mixed mating system, had significantly lower genetic diversity in ex-situ populations, and significantly higher ex-situ-wild FST . When the collection size for ex-situ conservation was ≥30 or 50, PPB, HE , and ex-situ-wild FST were not significantly different between ex-situ and wild populations, indicating a relatively high genetic representativeness. Collecting from the entire natural distribution range and mixing collections from different sources could significantly increase the genetic representativeness of ex-situ populations. Type of ex-situ conservation (i.e., planting or seed bank) had no effect on genetic representativeness. The effect size of HE decreased and the effect size of ex-situ-wild FST increased with the duration of ex-situ conservation. Our results suggest that current ex-situ plant collections do not effectively capture the genetic variation of wild populations. Low genetic representativeness of ex-situ populations was caused by both initial incomplete sampling from wild populations and genetic erosion during ex-situ conservation. We emphasize that it is necessary to employ more thorough sampling strategies in future collecting efforts and to add new individuals where needed. Article impact statement: Low genetic representativeness of living plant collections is a worldwide problem in ex situ conservation. This article is protected by copyright. All rights reserved.

Meta-analysis of genetic representativeness of plant populations under ex situ conservation in contrast to wild source populations.

Achieving high intraspecific genetic diversity is a critical goal in ecological restoration as it increases the adaptive potential and long-term resilience of populations. Thus, we investigated genetic diversity within and between pristine sites in a fossil floodplain and compared it to sites restored by hay transfer between 1997 and 2014. RAD-seq genotyping revealed that the stenoecious floodplain species Arabis nemorensis is co-occurring with individuals that, based on ploidy, ITS-sequencing and morphology, probably belong to the close relative Arabis sagittata, which has a documented preference for dry calcareous grasslands but has not been reported in floodplain meadows. We show that hay transfer maintains genetic diversity for both species. Additionally, in A. sagittata, transfer from multiple genetically isolated pristine sites resulted in restored sites with increased diversity and admixed local genotypes. In A. nemorensis, transfer did not create novel admixture dynamics because genetic diversity between pristine sites was less differentiated. Thus, the effects of hay transfer on genetic diversity also depend on the genetic make-up of the donor communities of each species, especially when local material is mixed. Our results demonstrate the efficiency of hay transfer for habitat restoration and emphasize the importance of prerestoration characterization of microgeographic patterns of intraspecific diversity of the community to guarantee that restoration practices reach their goal, that is maximize the adaptive potential of the entire restored plant community. Overlooking these patterns may alter the balance between species in the community. Additionally, our comparison of summary statistics obtained from de novo- and reference-based RAD-seq pipelines shows that the genomic impact of restoration can be reliably monitored in species lacking prior genomic knowledge.

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Strengths and potential pitfalls of hay transfer for ecological restoration revealed by RAD-seq analysis in floodplain Arabis species

Many botanic gardens keep ex situ collections of rare species to prevent their extinction and to enable their reintroduction into the wild. A potential problem with ex situ collections is that relaxed selection, genetic drift, novel selection and inbreeding may cause rapid loss of adaptation to natural conditions and therefore may hamper success of reintroductions. Here, we investigated whether cultivation in ex situ collections of three threatened species—Trifolium spadiceum, Sisymbrium austriacum and Bromus grossus—influenced trait differentiation. Using plant material from the original source populations and from the ex situ collections, we compared germination characteristics, growth and phenology under different environmental treatments. Trifolium spadiceum showed reduced seed dormancy in the ex situ collection compared to the wild population, whereas germination temperature requirements changed for S. austriacum. Trifolium spadiceum also showed reduced seed viability in the ex situ collection compared to the wild population. All species showed differences in plant growth between the plants from nature and from the botanic garden. Additionally, B. grossus showed advanced flowering time in plants from the botanic garden. These differences may reflect reduced performance or changes in life-history strategies. We conclude that all three species have rapidly differentiated between wild and ex situ origins and that effects of relaxed selection, genetic drift, inbreeding depression and adaptation to cultivation conditions in the botanic garden may have played a role in population differentiation, which may be unfavourable for reintroduction into nature. To explore this further we suggest broader studies across more species, populations and gardens, involving common garden, reciprocal transplant and molecular studies.

Plant populations of three threatened species experience rapid evolution under ex situ cultivation

Genotypic diversity and environmental variability affect the invasibility of experimental plant populations

Ongoing global warming, coupled with increased drought frequencies, together with other biotic drivers may have resulted in complex evolutionary adaptation. The resurrection approach, comparing ancestors raised from stored seeds with their contemporary descendants under common conditions, is a powerful method to test for recent evolution in plant populations. We used 21-26-year-old seeds of four European plant species - Matthiola tricuspidata, Plantago crassifolia, Clinopodium vulgare and Leontodon hispidus - stored in seed banks together with re-collected seeds from their wild populations. To test for evolutionary changes, we conducted a greenhouse experiment that quantified heritable changes in plant responses to drought and simulated insect herbivory. In three out of the four studied species, we found evidence that descendants evolved shorter life cycles through faster growth and flowering. Shifts in the osmotic potential and leaf dry matter content indicated that descendants also evolved increased drought tolerance. A comparison of QST vs. FST values, using ddRAD genotyping data, suggested that directional selection, and therefore adaptive evolution, was underlying some of the observed phenotypic changes. In summary, our study reveals evolutionary changes in plant populations over the last decades that are consistent with adaptation of drought escape and tolerance as well as herbivory avoidance.

Robert Rauschkolb

Papers

Plant populations of three threatened species experience rapid evolution under ex situ cultivation

Genotypic diversity and environmental variability affect the invasibility of experimental plant populations

Evolution of plant drought strategies and herbivore tolerance after two decades of climate change.

Historical comparisons show evolutionary changes in drought responses in European plant species after two decades of climate change

Flowering and leaf phenology are more variable and stronger associated to functional traits in herbaceous compared to tree species