Comparative Studies On Ecophysiological Traits And Nuclear DNA C-values Among Invasive And Native Species

Few studies have been conducted to investigate the ecophysiological traits of invasive plants so far, and most of these studies compared phylogenetically unrelated invasive and native species. However, ecophysiologial comparisons among sympatric, closely related invasive and noninvasive alien species and native species are more meaningful for exploring the mechanisms underlying the invasiveness of alien plants. In this study, the ecophysiological traits and nuclear DNA C-values were measured in invasive and noninvasive alien species and native species within four genera in Xishuangbanna, Yunnan Province, southwest China. The invasiveness of the noxious invasive species was discussed.The main results were as follows:1. Invasive species in two of the four genera studied (Amaranthus and Peperomia) showed significantly higher light-saturated photosynthetic rate, apparent quantum yield and biochemical capacity for photosynthesis (maximum carboxylation rate and maximum electron transport rate) than their native congeners. Furthermore, invasive alien species were also significantly higher in these variables than their noninvasive alien congeners for all the two genera that included noninvasive alien species (Oxalis and Peperomia).2. Invasive species in two of the four genera studied (Peperomia and Piper) exhibited significantly higher leaf area ratio and specific leaf area (SLA). And SLA was significantly higher for the invasive alien species than for the noninvasive alien species in all the two genera including noninvasive alien species (Oxalis and Peperomia).3. Invasive species were significantly higher in photosynthetic nitrogen use efficiency (PNUE) than their native congeners in three of the four studied genera (Amaranthus, Peperomia and Piper). For Oxalis and Peperomia which included noninvasive alien species, invasive species were significantly higher in PNUE than their noninvasive alien congeners.4. Invasive species showed significantly lower leaf construction cost (CC) than their native congeners in two of the four genera studied (Peperomia and Piper). Only one invasive species in Oxalis showed significantly lower CC than its noninvasive alien congener.Through determining the nuclear DNA C-values of 20 species from 10 genera of eight families with flow cytometer, we found that the DNA C-value of the 13 invasive alien species as a group was significantly lower than that of the six native species and one noninvasive alien species. However, no consistent pattern was found when compared between different species within the same genus. All the invasive species showed consistently lower nuclear DNA C-values than their native congeners in only two of the four genera including both invasive and native species (Eupatorium and Bidens); only one of the two invasive species in Alternanthera showed significantly lower nuclear DNA C-values than its native congener. In contrast, invasive species in Peperomia showed significantly higher nuclear DNA C-value than native species. Not all the invasive alien species had lower nuclear DNA C-values than their native congeners. Therefore, the association between nuclear DNA C-value and plant invasiveness was not confirmed completely in our study.