EXOTIC PALMS THREATENS NATIVE PALMS: A RISK TO PLANT BIODIVERSITY OF ATLANTIC FOREST

ABSTRACT Invasive plants can profoundly modify physical and biological characteristics of their new environments, especially when such habitats are already fragmented and reduced by anthropogenic pressure, such as the Atlantic Forest of Brazil. Here, we hypothesized that exotic palms successfully establish among the natural Euterpe edulis populations through a continuous propagule input by avifauna, high germination rates, and rapid growth. As a result, the native palm is experiencing decline and may be threatened with extinction. Beginning in 2007, we conducted a continuous forest inventory (FCI) every three years in the primary and secondary forest fragments of Viçosa, Minas Gerais. We use a Markov matrix to project future distributions of palm trees. The secondary forest contained three exotic palm species: Archontophoenix alexandrae, Livistona chinensis, and Arenga caudata. The first palm is a serious risk to natural E. edulis populations in the Atlantic because of frequent interactions with birds, rapid germination, and aggressive colonization in the lower to medium vertical forest strata. Currently, natural E. edulis populations are viable and sustainable, capable of regeneration, growth, and fruiting, their communities maintain continuous gene flow, dominating vertical forest strata compared with exotic palms. However, exotic palms should be monitored and control measures should be analyzed, especially in areas with A. alexandrae populations.

摘要 入侵植物可显著改变其新生境的物理与生物学特征，当这类生境已因人为压力出现片段化与退化时，这种改变尤为突出，巴西大西洋沿岸森林便是典型案例。本研究提出假说：外来棕榈可通过鸟类持续传播繁殖体、高萌发率以及快速生长这三个途径，成功在天然菜棕（Euterpe edulis）种群中定殖。受此影响，本地菜棕种群正经历衰退，甚至面临灭绝威胁。自2007年起，研究团队在米纳斯吉拉斯州维索萨地区的原生林与次生林片段中开展每三年一次的连续森林清查（Forest Inventory, FCI），并采用马尔可夫矩阵（Markov matrix）预测棕榈树的未来分布格局。次生林内共分布有3种外来棕榈：亚历山大椰子（Archontophoenix alexandrae）、蒲葵（Livistona chinensis）以及尾叶桄榔（Arenga caudata）。其中，亚历山大椰子因与鸟类存在频繁交互、萌发速度快且能在森林中下层垂直层位快速侵占生境，对大西洋沿岸森林内的天然菜棕种群构成严重威胁。目前，天然菜棕种群仍具生存活力与可持续性，能够完成更新、生长与结实，其群落维持着连续的基因交流，且相较于外来棕榈，在森林垂直层位中占据主导地位。但仍需对外来棕榈种群开展监测，并对防控措施进行论证分析，在亚历山大椰子分布的区域尤应加强关注。