Drouin Annick, McKindsey Christopher W, Johnson Ladd E
Demersal and Benthic Sciences Branch, Maurice-Lamontagne Institute, Fisheries and Oceans Canada, PO Box 1000, Mont Joli, QC G5H 3Z4 Canada ; Département de biologie et Québec-Océan, Université Laval, Quebec, QC G1V 0A6 Canada.
Demersal and Benthic Sciences Branch, Maurice-Lamontagne Institute, Fisheries and Oceans Canada, PO Box 1000, Mont Joli, QC G5H 3Z4 Canada.
Mar Biol. 2016;163:61. doi: 10.1007/s00227-016-2832-z. Epub 2016 Feb 24.
Knowledge of the potential distribution (i.e. abundance and spatial extent) of an invasive species is important to estimating its potential impacts on recipient communities. Most previous studies have focused on the potential spatial extent of invasive species populations at regional scales, but little is known on how species successfully recruit and establish at more local scales. In this study, we examined how recruitment of the green alga ssp. (hereafter ) can vary spatially and the environmental factors associated with establishment in eelgrass () beds. Standardized recruitment blocks (65 blocks in a 720 × 240 m grid) were used to monitor the number of recruits, juveniles and adults over 2 years. Environmental factors (depth, relative water flow, light and temperature) and attributes of the surrounding macrophyte assemblage (eelgrass density, eelgrass length, biomass) were also measured. Recruitment occurred on all blocks or nearby artificial structures (i.e. buoys) and mainly originated from button stages (i.e. female gametes or utricles). Contrary to other studies, the abundance of (recruits, juveniles and adults) was best predicted by the density of the native canopy-forming species, , which highlights a positive interaction between native and non-native canopy-forming species. Seasonal variation in recruitment was observed; it was lower during the summer. Recruitment did not show any distinct spatial pattern (e.g. gradient or patch), but the same spatial pattern of recruitment was observed every sampling date, suggesting that there are "hotspots" for recruitment. In general, the total number of fronds observed on a block at the end of the experiment was positively correlated with the cumulative number of recruits. However, recruitment occurred on some blocks but recruits never grew, suggesting that some environmental factors limit distribution and abundance in eelgrass beds. Overall, the assessment of recruitment over 2 years showed that the colonization of suitable locations by within seagrass beds may take several years and that some factors may not only limit, but also inhibit expansion within eelgrass beds.
了解入侵物种的潜在分布（即丰度和空间范围）对于评估其对受纳群落的潜在影响至关重要。此前的大多数研究都集中在区域尺度上入侵物种种群的潜在空间范围，但对于物种如何在更局部尺度上成功补充和定殖却知之甚少。在本研究中，我们研究了绿藻石莼属物种（以下简称石莼）的补充在空间上如何变化以及与鳗草床中石莼定殖相关的环境因素。使用标准化的补充样块（在一个720×240米的网格中有65个样块）来监测两年内石莼幼苗、幼体和成体的数量。还测量了环境因素（深度、相对水流、光照和温度）以及周围大型植物群落的属性（鳗草密度、鳗草长度、生物量）。补充发生在所有样块或附近的人工结构（即浮标）上，且主要源自孢芽阶段（即雌配子或囊果）。与其他研究相反，石莼（幼苗、幼体和成体）的丰度最好由本地形成冠层的物种——鳗草的密度来预测，这突出了本地和非本地形成冠层物种之间的正相互作用。观察到补充存在季节性变化；夏季补充率较低。补充没有呈现出任何明显的空间格局（例如梯度或斑块），但在每个采样日期都观察到相同的补充空间格局，这表明存在补充“热点”。总体而言，在实验结束时，一个样块上观察到的石莼叶片总数与幼苗的累积数量呈正相关。然而，在一些样块上发生了补充，但幼苗从未生长，这表明一些环境因素限制了石莼在鳗草床中的分布和丰度。总的来说，对两年内石莼补充的评估表明，石莼在海草床内适宜位置的定殖可能需要数年时间，并且一些因素可能不仅限制，还会抑制石莼在鳗草床内的扩张。
