Balestri Elena, Vallerini Flavia, Lardicci Claudio
Department of Biology, University of PisaPisa, Italy.
Front Plant Sci. 2017 Jun 16;8:1067. doi: 10.3389/fpls.2017.01067. eCollection 2017.
Seagrasses are declining globally, and deeper understanding is needed on the recruitment potential and distribution of new populations for many threatened species to support conservation planning in the face of climate change. Recruitment of , a threatened seagrass endemic to the Mediterranean, has long been considered rare due to infrequent flowering, but mounting evidence demonstrates that the species is responding to a changing climate through greater reproductive effort. Due to the fragmentary information on recruit occurrence and distribution, little is known about reproductive success in the species and its contribution to persistence. We assembled recruitment data from published and unpublished sources, including our own, to examine the frequency and extent of recruitment events (establishment of seedlings in a site), seedling growth potential and habitat characteristics at recruitment sites. Results show that at least one recruitment event has occurred about every 3 years, and 18 localities were colonized at least one time since the first seedling record in 1986. Notably, consistently high seedling inputs were observed in four localities of the Western Mediterranean. Seedlings established mainly on unoccupied substrate areas along the coasts of islands, in sheltered sites and at shallower depths (<3 m) than the upper limit of adjacent meadows. Seedling establishment occurred more frequently on rocky than on sandy substrate, and rarely on dead "matte" or meadows of the seagrass . The chance of colonization success on rock was two times higher than on sand. Our 11 years of observations have allowed for the first time the documentation of the formation and development of patches by seed. These findings contradict the historical assumption that sexual recruitment is rare and usually unsuccessful for , and highlight the potential importance of recruitment for the long-term persistence and adaptation of the species to sea level rise predicted in the next century in the Mediterranean. Unfortunately, management actions have mainly focused on established meadows, ignoring the presence of recruits in outside areas. Therefore, it will be useful to identify and consider regeneration sites in designing future management strategies to improve seagrass conservation effectiveness.
全球海草数量正在减少，面对气候变化，为支持保护规划，需要更深入了解许多濒危物种的新种群补充潜力和分布情况。地中海特有的濒危海草，长期以来因其开花不频繁，被认为补充率很低，但越来越多的证据表明，该物种正通过加大繁殖投入来应对气候变化。由于关于补充个体出现和分布的信息零散，人们对该物种的繁殖成功率及其对种群延续的贡献知之甚少。我们整合了已发表和未发表来源（包括我们自己的）的补充数据，以研究补充事件（在某一地点幼苗的建立）的频率和范围、幼苗生长潜力以及补充地点的栖息地特征。结果表明，自1986年首次记录到幼苗以来，大约每3年至少发生一次补充事件，有18个地点至少被殖民过一次。值得注意的是，在西地中海的四个地点观察到持续有大量的幼苗补充。幼苗主要在岛屿海岸未被占据的基质区域、隐蔽地点以及比相邻草甸上限更浅的深度（<3米）处建立。幼苗在岩石基质上比在沙质基质上更频繁地建立，很少在海草的死亡“垫层”或草甸上建立。在岩石上定殖成功的几率比在沙子上高两倍。我们11年的观察首次记录了种子形成斑块的过程和发育情况。这些发现与以往认为该物种有性补充很少且通常不成功的假设相矛盾，并凸显了补充对该物种在下个世纪地中海预计海平面上升情况下的长期延续和适应的潜在重要性。不幸的是，管理行动主要集中在已有的草甸上，而忽略了外部区域补充个体的存在。因此，在设计未来管理策略时识别并考虑再生地点，将有助于提高海草保护成效。
