Invasive alien plants in China: diversity and ecological insights

China's current invasive alien plant species were analyzed with regard to their floristic status, biological attributes and invasion status elsewhere. Most of the 270 species identified were annuals, followed by perennial herbs. Woody perennials made only about 10% of the species. The invasives were comprised of 59 families, the largest being Asteraceae, Poaceae, and Brassicaceae. The genera with most invasive species were Amaranthus, Ipomoea, and Solanum. Most of the species originated from the New World, notably from South America. About one-third of the species were serious invaders of natural habitats in countries other than China. The proportion of invasive alien plants in province floras ranged from 0.5 to 3.8%, absolute numbers from nine to 117 species per province. Density of invasive species was correlated positively with native species density at provincial scale. The results demonstrate that in China invasive plants are present throughout the country, with a particularly high species richness in the Southeast. The ecological diversity of invasive plants suggests wide ranging impacts which need to be assesse

Do alien plants on Mediterranean islands tend to invade different niches from native species?

In order to understand invasions, it is important to know how alien species exploit opportunities in unfamiliar ecosystems. For example, are aliens concentrated in niches under-exploited by native communities, or widely distributed across the ecological spectrum? To explore this question, we compared the niches occupied by 394 naturalized alien plants with a representative sample from the native flora of Mediterranean islands. When niche structure was described by a functional group categorization, the distribution of native and alien species was remarkably similar, although “succulent shrubs” and “trees with specialized animal pollination mechanisms” were under-represented in the native species pool. When niche structure was described by Grime’s CSR strategy, the positioning of aliens and natives differed more strongly. Stress-tolerance was much rarer amongst the aliens, and a competitive strategy was more prevalent at the habitat level. This pattern is similar to previous findings in temperate Europe, although in those regions it closely reflects patterns of native diversity. Stressed environments are much more dominant in the Mediterranean. We discuss a number of factors which may contribute to this difference, e.g., competitive and ruderal niches are often associated with anthropogenic habitats, and their high invasibility may be due partly to introduction patterns rather than to a greater efficiency of aliens at exploiting them. Thus far, the reasons for invasion success amongst introduced species have proved difficult to unravel. Despite some differences, our evidence suggests that alien species naturalize across a wide range of niches. Given that their ecologies therefore vary greatly, one may ask why such species should be expected to share predictable traits at all