Wild-collected Seeds Research Articles

Micromorphology of wild-collected seeds from Paeonia L. in Serbia—Use of taxonomic markers in species determination

Seed traits have proven to be an effective taxonomic tool in a variety of plant groups and at different levels of classification. The main objective of this study was to describe and compare the characteristics of seeds from all wild-growing herbaceous peonies in Serbia and to evaluate and test their potential taxonomic significance. Seed samples of Paeonia officinalis subsp. banatica (Rochel) Soó, P. tenuifolia L., P. peregrina Miller, and P. daurica Andrews (15 populations) were collected across the Republic of Serbia and analyzed using light and scanning electron microscopy; 17 seed characters in total were identified, 14 of which were qualitative. The collected data was analyzed using both basic and multivariate statistical methods, focusing on both quantitative and qualitative traits. The outcomes revealed a distinct separation between the species based on both quantitative and qualitative parameters. The characters that contribute most to discrimination between species are seed length, color, and shape, sutura and hilum shape, and seed surface type. Based on these characters, a determination key was created, which enables easier identification of species. The results greatly contribute to the taxonomy of the genus Paeonia, and these characteristics enable a more accurate diagnosis of each of the examined species.

Plants cultivated for ecosystem restoration can evolve toward a domestication syndrome

The UN Decade on Ecosystem Restoration calls for upscaling restoration efforts, but many terrestrial restoration projects are constrained by seed availability. To overcome these constraints, wild plants are increasingly propagated on farms to produce seeds for restoration projects. During on-farm propagation, the plants face non-natural conditions with different selection pressures, and they might evolve adaptations to cultivation that parallel those of agricultural crops, which could be detrimental to restoration success. To test this, we compared traits of 19 species grown from wild-collected seeds to those from their farm-propagated offspring of up to four cultivation generations, produced by two European seed growers, in a common garden experiment. We found that some plants rapidly evolved across cultivated generations towards increased size and reproduction, lower within-species variability, and more synchronized flowering. In one species, we found evolution towards less seed shattering. These trait changes are typical signs of the crop domestication syndrome, and our study demonstrates that it can also occur during cultivation of wild plants, within only few cultivated generations. However, there was large variability between cultivation lineages, and the observed effect sizes were generally rather moderate, which suggests that the detected evolutionary changes are unlikely to compromise farm-propagated seeds for ecosystem restoration. To mitigate the potential negative effects of unintended selection, we recommend to limit the maximum number of generations the plants can be cultivated without replenishing the seed stock from new wild collections.

Factors Regulating Population Stand Structure in Blackbrush (Coleogyne ramosissima: Rosaceae), a Masting North American Desert Shrub

Blackbrush (Coleogyne ramosissima Torr.) is the dominant shrub on three million hectares across the transition zone between the western North American warm and cold deserts. This paper presents a study of blackbrush population structure at the stand level at sixteen sites across the species range. New stand-level information is then integrated with what is already known about blackbrush population ecology to explore the stand-level consequences of several unusual features of blackbrush life history, including its masting reproductive strategy, its interactions with heteromyid rodents that are both seed predators and dispersers, and its ability to form ‘seedling banks’ of growth-suppressed individuals, often within the crowns of adult conspecifics. It complements earlier work showing that blackbrush stands are organized at both the inter-clump and intra-clump levels. Each clump represents an establishment nexus where younger individual genets replace older genets over an extended time period. Inter-clump structure is thus determined by the rate of establishment of new clumps rather than new individuals. This has resulted in contrasting stand structures in response to rodent community composition, disturbance regimes, and climatic variability at the leading and trailing edges of current blackbrush distribution in the eastern Mojave Desert and Colorado Plateau regions. Because blackbrush likely disperses too slowly to track anthropogenic climate change, assisted migration with wild-collected seeds may be necessary to promote its continued survival and dominance.

Use of Flash-Flaming Technology to Improve Seed Handling and Delivery of Winterfat (Krascheninnikovia lanata)

Ecological restoration of rangelands using wild-collected seeds can be challenging due to low seed quality, inconvenient seed anatomy, and poor plant establishment. In North America, the half-shrub winterfat (Krascheninnikovia lanata) is a valuable protein-rich forage for wildlife and livestock. Seeds of this species are contained in one-seeded fruits enclosed in four fluffy, silky bracts. While the seeds can be removed from the bracts, it is not recommended as the bracts are thought to help protect the seed and aid in germination and seedling growth. However, bracts of winterfat make it difficult to incorporate this species within a seed mix because they prevent the seed from flowing through mechanized seeders. The anatomy of winterfat fruit also makes it difficult to treat this species with external seed-coating materials that may aid in direct seeding efforts. We tested the use of a recently developed flash-flaming technique in combination with seed coating to improve the flowability of winterfat fruits. Our results indicate that flash flaming can reduce the appendages on winterfat fruits, which decreased fruit volume by up to 46% without impacting seed germination. Flash flaming also makes it possible to incorporate a polymer seed coating to the exterior of winterfat fruits. We found that flash flaming combined with seed coating improved the flowability of winterfat fruits, as measured with standard laboratory tests and by delivering fruits through a broadcast seeder and a rangeland drill. These results indicate that flash flaming plus seed coating provides a new technology that will allow for the treating and planting of winterfat on degraded rangelands.

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

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 specialised 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 seed 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, while in the other, mostly perennial and outcrossing species, the observed changes were mostly minor. Agricultural propagation of native seed material for restoration can cause evolutionary changes, at least in some species. We recommend caution, particularly in selfing and short-lived species, where evolution may be more rapid and effects may thus be more severe.

Conservation Horticulture for Yarey Palm and Buccaneer Palm: Substrate and Sowing Depth Affect Germination and Early Seedling Growth

Palms (Arecaceae) are perhaps the most important tropical plant family for human use, both for utility and ornamental horticulture. The wide diversity of palm species with different seed germination characteristics necessitates tailoring horticultural practices to the needs of each. This is crucial for production and conservation horticulture. In this study, wild-collected seeds of yarey palm (Copernicia berteroana) and buccaneer palm (Pseudophoenix sargentii) were germinated in a variety of organic (standard nursery container mixes) and inorganic substrates. The yarey palm seeds were sown at two different depths, 0.5 inch and at the surface (seed half exposed). Mean maximum germination across all treatments for yarey palm was 79% and for buccaneer palm 60%. The standard nursery mixes generally fostered the best germination and long-term survival. This is likely due to a combination of the lower water availability at the surfaces of the more porous inorganic substrates (sand and perlite) and greater difficulty for coarse palm roots to penetrate the denser inorganic substrates, including fired ceramic, which otherwise had similar water-holding capacity (WHC) and even lower air space than the organic substrates. Difficulty of penetration caused roots of some seedlings to either dry up early in germination as in the surface sown yarey palm, or to “push up” the seed (buccaneer palm) rather than penetrating the substrate and this was often fatal. Thus, inorganic substrates are not recommended for germination and early seedling growth of these palm species and planting the seeds slightly below the surface may be preferable to surface sowing. For conservation horticulture of wild-collected palm seeds, this information can help prevent further genetic bottlenecks while under protective cultivation.

Flash flaming effectively removes appendages and improves the seed coating potential of grass florets

Ecological restoration of grasslands using wild‐collected seeds is a major undertaking in many parts of the world. Impediments to effective seed use such as low seed quality, difficult‐to‐handle and bulky collections of seeds, and seed dormancy and germination constraints contribute to restoration failure. Native grass florets are typically irregular in shape, with appendages that impede efficient mechanized sowing and render agricultural technologies, such as the application of polymer seed coatings, impractical. Our goal was to investigate the application of a novel flaming device to remove floret appendages and improve geometry using Triodia wiseana (C.A. Gardner [Poaceae]), a key framework grass of arid ecosystems in north‐western Australia, as a test species. Through the modification of a rotary seed coater with an engineered flaming apparatus, a flash flaming technique was developed. We demonstrate that flash flaming is a highly effective and efficient means of removing floret appendages and subsequently improving geometry. Once flamed, the bulk density of florets was significantly increased, the application of polymer coatings was more effective, and germination was enhanced. The improved floret geometry through flaming therefore shows promise for enhancing the mechanization of direct seeding of grasses.

Geographic variation in climate as a proxy for climate change: Forecasting evolutionary trajectories from species differentiation and genetic correlations.

Climate change models for California predict a warmer, drier future, potentially resulting in shorter growing seasons. If phenotypic differences between closely related species currently distributed across a moisture and temperature gradient represent adaptations to their abiotic environment, then as conditions become warmer and drier, populations presently adapted to cooler and wetter conditions may evolve to become more similar to those adapted to warmer and drier conditions. Two sister species, Clarkia unguiculata and C. exilis, are distributed across a moisture and temperature gradient in the southern Sierra Nevada, providing an opportunity to predict how this process may occur. In a greenhouse experiment using wild-collected seeds from 11 populations in the southern Sierra Nevada, we examined relationships among elevation, climatic conditions, and population means for each trait, then evaluated bivariate relationships among maternal family means, using raw values and controlling for population and seed mass effects on phenotype. Clarkia exilis occupied warmer, drier conditions, typically at lower elevations, than C. unguiculata did and flowered earlier and faster, producing smaller flowers with lower herkogamy. In C. unguiculata, petal area, herkogamy, and the rate of flower production were positively correlated with days to first flower. If selection favors earlier flowering, smaller petals, or faster flower production in C. unguiculata, then the genetic correlations among these traits should reinforce their joint evolution. Moreover, the correlations between these traits and herkogamy may promote the evolution of self-fertilization as an indirect response to selection, a previously unrecognized potential outcome of climate change.

Larval Host Choice of the Monarch Butterfly (Danaus plexippus L.) on Four Native California Desert Milkweed Species

The monarch butterfly, Danaus plexippus L. (Lepidoptera: Nymphalidae), is found across North America during the summer months. Adult populations from western North America migrate to roost along the central coast of California. Monarchs that disperse in the spring to the arid regions of southern California encounter widely dispersed individuals of desert milkweed species, including Asclepias fascicularis Decne. (Narrow-Leaf Milkweed), A. californica E. Greene (California Milkweed), A. eriocarpa Benth. (Indian Milkweed), and A. erosa Torrey (Desert Milkweed). The four species represent a range in suitability as hosts for monarch larvae. In laboratory assays of plants grown from wild-collected seeds, neonate larvae showed the least preference for A. fascicularis in host-selection assays and there were no differences in preference among the other three species. Previous research has shown that A. fascicularis has the lowest level of cardiac glycosides and the lowest latex flow of the four species examined. The leaf hairs of A. californica and A. eriocarpa provide a significant barrier to neonate larval success; larvae feeding on shaved leaves were significantly larger than larvae feeding on leaves with intact hairs. First instar larval behavior of cutting hairs before beginning to feed may improve their success by modifying plant quality and defenses.

Consequences of seed origin and biological invasion for early establishment in restoration of a North American grass species.

Local, wild-collected seeds of native plants are recommended for use in ecological restoration to maintain patterns of adaptive variation. However, some environments are so drastically altered by exotic, invasive weeds that original environmental conditions may no longer exist. Under these circumstances, cultivated varieties selected for improved germination and vigor may have a competitive advantage at highly disturbed sites. This study investigated differences in early establishment and seedling performance between wild and cultivated seed sources of the native grass, Poa secunda, both with and without competition from the invasive exotic grass, Bromus tectorum. We measured seedling survival and above-ground biomass at two experimental sites in western Montana, and found that the source of seeds selected for restoration can influence establishment at the restoration site. Cultivars had an overall advantage when compared with local genotypes, supporting evidence of greater vigor among cultivated varieties of native species. This advantage, however, declined rapidly in the presence of B. tectorum and most accessions were not significantly different for growth and survival in competition plots. Only one cultivar had a consistent advantage despite a strong decline in its performance when competing with invasive plants. As a result, cultivated varieties did not meet expectations for greater establishment and persistence relative to local genotypes in the presence of invasive, exotic species. We recommend the use of representative local or regional wild seed sources in restoration to minimize commercial selection, and a mix of individual accessions (wild, or cultivated when necessary) in highly invaded settings to capture vigorous genotypes and increase the odds native plants will establish at restoration sites.

The establishment of axenic seed and embryo cultures of endangered Hawaiian plant species: special review of disinfestation protocols

More than one third of the USA’s federally listed endangered and threatened plants are endemic to Hawaii. Because of the accelerating rate of environmental pressures resulting from habitat degradation to loss, the Hawaiian Rare Plant Program (HRPP, Lyon Arboretum, Honolulu, Hawaii) utilizes in vitro culture and seed storage to rescue, recover, and restore Hawaii’s most critically endangered native plant taxa. These in vitro methods complement existing ex situ and in situ efforts in the state. Wild-collected seeds tend to be hard to clean, and obtaining contamination-free seeds or embryos without damage or over sterilization is one of the most difficult obstacles in the successful establishment of in vitro cultures. Loss of rare and valuable propagation material occurs when seed samples succumb to contamination or mortality during the initial disinfestation stage. This study reviews pre-treatments and provides examples of three general disinfestation protocols successfully used in the HRPP to establish axenic ovule and embryo cultures of some endangered Hawaiian species. Three disinfestation protocols are described: bleach sterilization, gas sterilization, and ethanol dip and flame. Since 1998, the HRPP has been successful in establishing in vitro cultures of 135 endangered Hawaiian plant taxa representing 30 genera.

Restoration of Cymodocea nodosa seagrass meadows through seed propagation: germination in vitro, seedling culture and field transplants

Abstract Cymodocea nodosa, a marine angiosperm, an ecosystem engineer in the Mediterranean Sea and the Northwest Atlantic Ocean; however, as in other seagrasses meadows worldwide, the swards are actually declining due to increasing human pressures. Hence, we have developed an effective propagation methodology that provides C. nodosa seedlings for seagrass meadow restoration and conservation. This method consists of: i) germination of wild-collected seeds under hyposaline conditions, ii) acclimation of germinated seedling in tanks (1.6 m3) until there are two shoots per seedling (∼ 30 days), and iii) transplantation of acclimated seedlings to the field in dense groups. Our field outplants withstood herbivore activity and physical disturbance during the winter season, and propagated vegetatively, resulting in the spread and establishment of a new patch that has persisted for nine months.

Indices Seminum:

This manuscript investigates whether indices seminum are currently aiding conservation or whether they require modernisation. It is widely assumed that the proportion of wild-collected seeds has increased within botanical seed lists. Through a number of studies we found the reverse to be true. Our paper also found that very widespread taxa were needlessly offered from garden origin. More worrying is that taxa well known for their invasiveness were also freely available for distribution. Another concern was the failure to supply or request associated data for wild-collected seeds despite its availability, a neglect counter-intuitive to botanic gardens. We highlight that in their present form indices seminum are a waste of resources and offer little to legitimate conservation. A range of recommendations is provided for modernising this activity in order to prioritise conservation, one of our biggest challenges of the 21st century.

Ecological genetics of seed germination regulation in Bromus tectorum L. : I. Phenotypic variance among and within populations.

Regulation of seed germination phenology is an important aspect of the life history strategy of invading annual plant species. In the obligately selfing winter annual grass Bromus tectorum, seeds are at least conditionally dormant at dispersal in early summer and lose dormancy through dry-afterripening. Patterns of germination response at dispersal vary among populations and sometimes across years within populations. To assess the relative contribution of genotype and maturation environment to this variation, we grew progeny of ten parental lines from each of six contrasting populations in a common greenhouse environment. We then tested the germination responses of recently harvested seeds of the putative full-sib progeny at five incubation temperatures. Significant germination response differences among populations were observed in greenhouse cultivation, and major differences among full-sib families were evident for some populations and traits. Among-population variation accounted for over 90% of the variance in each trait, while within-family variance accounted for 1% or less. Germination responses of greenhouse-grown progeny were positively correlated with the responses of wild-collected seeds, but there was a tendency for lowered dormancy at higher incubation temperatures. This tendency was more marked in populations from cold desert, foothill, and plains habitats, suggesting a genotype-maturation environment interaction. Differences among populations in the amount of among-family variance were more evident at lower incubation temperatures, while among-family variance was more uniformly low at summer incubation temperatures. Populations from predictable extreme environments (subalpine meadow and warm desert margin) showed significantly less variation among families than populations from less predictable cold desert, foothill, and plains environments. Low among-family variance was not specifically associated with small population size or marginality of habitat, as small marginal populations from unpredictable environments showed variance as high as that of large populations. In populations with high among-family variance for germination traits, germination responses tended to be correlated across incubation temperatures, making it possible to characterize families in terms of their general dormancy status. The results indicate that seed germination regulation in this species is probably under strong genetic control, and that habitats with temporally varying selection are occupied by populations that tend to be more polymorphic in terms of their germination response patterns.

Life History Variation in Blue Flax (Linum perenne: Linaceae): Seed Germination Phenology

Linum perenne L. is a nonclonal perennial herb widely distributed across a range of habitats. Variation in seed germination patterns was examined for 21 Intermountain collections and for the commercial cultivar ‘Appar’. Collections from sites with long, snowy winters were largely dormant at harvest and responded positively to chilling. Collections from middle elevation sagebrush-grassland sites were generally nondormant and contained a fraction induced into secondary dormancy by chilling. Collections from palouse prairie and pinyon-juniper sites were generally nondormant and unaffected by chilling, as was ‘Appar’. When seeds of contrasting populations were planted in seed retrieval experiments at low, middle, and high elevation sites, their field germination phenology was predictable from laboratory experiments. In common garden experiments, there were significant among-sibship differences in germination for each garden-grown wild accession but not for ‘Appar’, suggesting that differences both among and within populations may be genetically based. Garden-grown seeds were generally less dormant than wild-collected seeds, possibly because of selection during propagation. Results demonstrated the existence of ecologically relevant among-population and within-population variation in germination phenology for blue flax. Seeds of high-montane populations are spring-emerging and have little provision for between-year carryover. Populations from lower elevation habitats with less predictable weather have seeds with contrasting germination patterns, allowing for emergence in both fall and spring as well as for seed bank carryover. ‘Appar’ seeds lack these predictive and carryover mechanisms.