Wilmshurst Janet M, McGlone Matt S, Turney Chris S M
Landcare Research, PO Box 69040, Lincoln 7640, New Zealand School of Environment, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
Landcare Research, PO Box 69040, Lincoln 7640, New Zealand.
AoB Plants. 2015 Aug 26;7:plv104. doi: 10.1093/aobpla/plv104.
Alien plants are a pervasive environmental problem, particularly on islands where they can rapidly transform unique indigenous ecosystems. However, often it is difficult to confidently determine whether a species is native or alien, especially if establishment occurred before historical records. This can present a management challenge: for example, should such taxa be eradicated or left alone until their region of origin and status are clarified? Here we show how combining palaeoecological and historical records can help resolve such dilemmas, using the tree daisy Olearia lyallii on the remote New Zealand subantarctic Auckland Islands as a case study. The status of this tree as native or introduced has remained uncertain for the 175 years since it was first discovered on the Auckland Islands, and its appropriate management is debated. Elsewhere, O. lyallii has a highly restricted distribution on small sea bird-rich islands within a 2° latitudinal band south of mainland New Zealand. Analysis of palaeoecological and historical records from the Auckland Islands suggest that O. lyallii established there c. 1807 when these islands were first exploited by European sealers. Establishment was facilitated by anthropogenic burning and clearing and its subsequent spread has been slow, limited in distribution and probably human-assisted. Olearia lyallii has succeeded mostly in highly disturbed sites which are also nutrient enriched from nesting sea birds, seals and sea spray. This marine subsidy has fuelled the rapid growth of O. lyallii and allowed this tree to be competitive against the maritime communities it has replaced. Although endemic to the New Zealand region, our evidence suggests that O. lyallii is alien to the Auckland Islands. Although such 'native' aliens can pose unique management challenges on islands, in this instance we suggest that ongoing monitoring with no control is an appropriate management action, as O. lyallii appears to pose minimal risk to ecological integrity.
外来植物是一个普遍存在的环境问题，尤其是在岛屿上，它们能够迅速改变独特的本土生态系统。然而，通常很难确切地确定一个物种是本土物种还是外来物种，特别是如果其定殖发生在历史记录之前。这可能带来管理上的挑战：例如，对于这类分类群，是应该根除还是任其自生自灭，直到其起源地和地位得到明确？在此，我们以偏远的新西兰亚南极奥克兰群岛上的树雏菊（Olearia lyallii）为例，展示了如何将古生态记录和历史记录相结合来帮助解决此类困境。自该树种在奥克兰群岛首次被发现的175年来，其作为本土物种还是引入物种的地位一直不确定，关于其适当管理的问题也存在争议。在其他地方，树雏菊在新西兰大陆以南2°纬度带内的小型海鸟丰富的岛屿上分布范围极为有限。对奥克兰群岛古生态和历史记录的分析表明，树雏菊大约在1807年这些岛屿首次被欧洲海豹捕猎者开发时就在那里定殖了。人为焚烧和开垦促进了其定殖，其随后的扩散一直很缓慢，分布范围有限，而且可能是人类协助的。树雏菊大多在受到严重干扰的地点成功生长，这些地点也因筑巢海鸟、海豹和海浪喷雾而养分丰富。这种海洋补贴促进了树雏菊的快速生长，并使其能够与它所取代的海洋群落竞争。尽管树雏菊是新西兰地区的特有物种，但我们的证据表明它对于奥克兰群岛来说是外来物种。尽管这类“本土”外来物种可能给岛屿带来独特的管理挑战，但在这种情况下，我们建议持续监测而不进行控制是一种适当的管理行动，因为树雏菊似乎对生态完整性构成的风险极小。
