Are the distribution and expansion of exotic invasive Asteraceae plants in overseas Chinese town wetland related to their leaf construction cost?

Overseas Chinese town wetland (OCT wetland) located in Shenzhen Bay has been considered as part of the important coast wetlands of Guangdong-Hong Kong-Macau Greater Bay Area. Many exotic species especially Asteraceae plants were found in OCT wetland, became invasive species and caused serious ecological problems in last decades. However, the reasons causing such expansion are not clear but leaf construction cost (CC) was found to be related to the growth rates and expansion of an exotic species. The present study investigated the distribution and expansion of exotic invasive Asteraceae plants in OCT wetland, and the relationships between distribution and leaf construction cost (CC) of these plants, aiming to identify the reasons that causing the invasions. Results showed that there were nearly 40% of the total plant species (27 species) in OCT wetland were exotic invasive species and belonged to 13 families and 23 genera. Six of all invasive species were Asteraceae plants and their distribution area was larger than the other invasive plants. Among these six species, the CC of Wedelia trilobata was the lowest but its distribution and expansion index (coverage, frequency and importance value) were the largest, while the opposite was found in Ageratum conyzoides. The CC of all six invasive Asteraceae plants declined in the order of W. trilobata < Mikania micrantha < Aster subulatus < Bidens pilosa < Praxelis clematidea < A. conyzoides, but orders of coverage, frequency and importance value of these plants were just the opposite. The distribution and expansion index of all invasive Asteraceae plants were positively correlated with their CC. These findings indicated that lower CC might be one important reason causing the invasion of these exotic species in OCT wetland.