Some Like It Hot: Maternal-Switching With Climate Change Modifies Formation of Invasive Spartina Hybrids

Limited life-history plasticity in marginal population of an invasive foundation species: Unraveling the genetic underpinnings and ecological implications

Plant's life history can evolve in response to variation in climate spatio-temporally, but numerous multiple-species studies overlook species-specific (especially a foundation species) ecological effects and genetic underpinnings. For a species to successfully invade a region, likely to become a foundation species, life-history variation of invasive plants exerts considerable ecological and evolutionary impacts on invaded ecosystems. We examined how an invasive foundation plant, Spartina alterniflora, varied in its life history along latitudinal gradient using a common gardens experiment. Two common gardens were located at range boundary in tropical zone and main distribution area of S. alterniflora in temperate zone in China. Within each population/garden, we measured the onset time of three successive phenological stages constituting the reproductive phase and a fitness trait. In the low-latitude garden with higher temperature, we found that reproductive phase was advanced and its length prolonged compared to the high-latitude garden. This could possibly due to lower plasticity of maturity time. Additionally, plasticity in the length of the reproductive phase positively related with fitness in the low-latitude garden. Marginal population from tropic had the lowest plasticity and fitness, and the poor capacity to cope with changing environment may result in reduction of this population. These results reflected genetic divergence in life history of S. alterniflora in China. Our study provided a novel view to test the center-periphery hypothesis by integration across a plant's life history and highlighted the significance in considering evolution. Such insights can help us to understand long-term ecological consequences of life-history variation, with implications for plant fitness, species interaction, and ecosystem functions under climate change.

×Sorbaronia mitschurinii: from an artificially created species to an invasion in Europe: repeating the fate of invasive Amelanchier ×spicata, a review

By intervening in natural events, relocating species to other areas, purposefully hybridizing them, as well as reducing the habitats required for them, humans have created conditions for new hybrid species to emerge. As long as hybrids exist in our gardens and fields, we have no reason to worry. However, problems arise with the expansion of these hybrid species into natural habitats, where such hybrid species cannot always be recognized and remain unnoticed, and in most cases they are often mistaken for natural parent species. Two hybrid species, Amelanchier ×spicata and ×Sorbaronia mitschurinii have historically developed in Europe with different scenarios of origin. It has been suggested in the past that both species are of hybrid origin, and recent molecular studies have confirmed the previous assumptions. There is no doubt that A. ×spicata originated in a natural way of hybridization, when the two parental species came into contact in Europe, but ×S. mitschurinii is a purposefully created species, crossing ×Sorbaronia fallax with Aronia melanocarpa. Produced as a result of different scenarios, these two hybrid species have become invasive in Europe, and ×S. mitschurinii has started to follow in the footsteps of the highly invasive A. ×spicata, spreading in the wild, where it predominantly expands in pine forests and in wetland forests along water bodies and bogs. Moreover, ×S. mitschurinii occupies the same habitats in Europe as one of its parent plants, A. melanocarpa in North America, and this species is a threat to wetland forest habitats. Given that ×S. mitschurinii has long been regarded as one of Aronia species, the exact distribution of the species in Europe is unknown, but the following countries are currently reporting the presence of the species in Europe: Belarus, Belgium, Czech Republic, Estonia, Finland, Latvia, Lithuania, Netherlands, Norway, Poland, Russian Federation, Sweden, Ukraine and United Kingdom. In the light of current knowledge, further studies on ×S. mitschurinii invasion in Europe are needed, as well as the need to correct the information in international databases, such as CABI, NOBANIS, to separate ×S. mitschurinii data from what applies to Aronia taxa.

Genetic Diversity of Invasive Spartina alterniflora Loisel. (Poaceae) Introduced Unintentionally Into Japan and Its Invasion Pathway

Among invasive species, aquatic plants pose serious threats to local biodiversity and ecosystem functions. Spartina alterniflora Loisel. (Poaceae), native to the eastern United States, was introduced unintentionally into Japan (Aichi and Kumamoto Prefectures) at around 2010. This invasive species could easily and rapidly spread to estuarine areas of Japan via vigorous trade and transport, making the prediction of its future invasion necessary. Here, the distribution and structure of the genetic variation of S. alterniflora in Japan were examined using chloroplast DNA (cpDNA) and microsatellite genotyping analyses for clarifying its invasion route and process. According to the cpDNA analysis, S. alterniflora populations in Japan had a single haplotype (haplotype C4) that is the most dominant genotype around the Florida Peninsula, the region of its origin, and is also widely found in the introduced populations in the East Asia. Microsatellite analysis also showed a loss of genetic diversity in Japanese S. alterniflora populations (allelic richness (A _R) = 1.20-1.39) compared with that in its native region (A _R = 4.58-4.59), suggesting a founder effect on S. alterniflora that might have occurred after invasion of the species into Japan. The principal coordinate analysis and The STRUCTURE analysis indicated that no gene mixing among Japanese local populations (Aichi, northern and southern Kumamoto) was observed, indicating that Spartina invasion occurred independently into these regions. Among the three regions, trading between the ports of northern Kumamoto and the U.S. was obviously lower than trading with China. We concluded that invasive S. alterniflora might have independently invaded Japan at different times through an East Asia route, particularly via China (i.e., secondary introduction). Therefore, it is important to strengthen the quarantine control on the importation of commodities, especially of transport vehicles at potential donor spots (i.e., border control/border biosecurity system), and to share information networks on invasive species between each region/port for minimizing further risks of biological species such as Spartina.

Effects of heavy metal pollution on germination and early seedling growth in native and invasive Spartina cordgrasses

Seed germination and seedling establishment are the stages most sensitive to abiotic stress in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either species were not affected by any metal at any tested concentration (up to 2000 μM). However, the increase in metal concentration had negative effects on S. densiflora seedlings. The primary effect was on radicle development, representing initial seedling emergence. Spartina densiflora seedlings emerging from seeds from Tinto Estuary, characterized by high bioavailable metal loads, showed higher tolerance to metals than those from less polluted Odiel and Piedras Estuaries. Comparing our results to metal concentrations in the field, we expect S. densiflora seedling development would be negatively impacted in the most metal-polluted areas in Odiel and Tinto Estuaries.