The Evolution of Increased Competitive Ability (EICA) hypothesis predicts that exotic plants may escape from the control of natural enemies in introduced ranges and gradually evolve to lose costly defense traits, reallocating resources and energy from defense to growth. Therefore, the invasive plants are usually considered to be more competitive than native conspecifics. However, the inconsistent results were also found frequently in recent years. The different identity of competitors may lead to the mixed results in those studies.
To test the effects of competitor identity, Dr. ZHENG Yulong of Xishuangbanna Tropical Botanical Garden (XTBG) and his collaborators set a series of competitive conditions in one common garden in Mexico: Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively.
They studied performance differences between Ageratina adenophora plants from native and invasive ranges in the absence of competitors (monoculture experiment), in the presence of intraspecific competitors (intraspecific competition experiment) and interspecific competitors from both ranges of the invader (interspecific competition experiment), and in an artificial monoculture community with high density (high density experiment).
The results showed that invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China, but not when competing with natives from Mexico (interspecific competition). However, invasive A. adenophora plants showed lower competitive ability when competing with conspecifics from native populations (intraspecific competition). The evolution of natural selection might relate with the inconsistent pattern.
Depending on the competitors used in their common garden experiment, the results indicated that the differences in competitive ability between A. adenophora plants from native and invasive populations were inconsistent. The differences in competitive ability between plants from native and invasive populations were competitor-dependent. The researchers thus proposed that it is important to take into account the effects of competitors when testing the EICA hypothesis, choose suitable competitors according to the specific purpose, and explain experimental results carefully.
The study entitled “Are invasive plants more competitive than native conspecifics? Patterns vary with competitors” has been published in Scientific Reports. Key Words
Ageratina adenophora; invasion; compatibility; conspecifics Contact
ZHENG Yulong Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Tel: 86 691 8713195
E-mail: zhengyl@xtbg.org.cn |
