Garthwin Ruby G, Poore Alistair G B, Ferretto Giulia, Wright Jeffrey T, Vergés Adriana
Centre for Marine Science and Innovation, School of Biological, Earth and Environmental Sciences University of New South Wales Sydney New South Wales Australia.
Sydney Institute of Marine Science Mosman New South Wales Australia.
Ecol Evol. 2024 Nov 17;14(11):e70561. doi: 10.1002/ece3.70561. eCollection 2024 Nov.
The polewards range expansion of tropical herbivorous fish into temperate latitudes is leading to overgrazing of marine habitats and community phase shifts in some regions. Here, we test the potential effects of increased herbivory on the temperate habitat-forming seagrass . We used a series of simulated herbivory experiments to predict the potential impacts of climate-mediated increases in seagrass consumption along entire latitudinal range (~9° latitude) in eastern Australia (1700 km of coastline). We subjected treatment plots to two levels of simulated herbivory (10% or 80% of leaves clipped) and compared them to unclipped controls. We measured seagrass leaf growth rates and tissue chemical traits: carbohydrates in rhizomes, leaf phenolics, and nutrients (carbon, nitrogen, and C:N ratio) in leaves and rhizomes. At the warmest range-edge population, we also tested how responses to increased herbivory may vary between summer and winter, or with repeated clipping events. Clipped shoots maintained growth rates similar to unclipped controls despite losing up to 80% of leaf biomass. This was consistent along the full latitudinal range and after repeated simulated herbivory at the northernmost location. One-off clipping events impacted plant architecture, increasing the number of subdividing shoots. At the species range edge, leaves grew more in winter than in summer, and clipping tended to lower seagrass growth only in winter; however, higher levels of shoot subdivision were produced over summer than in winter. Plant chemical traits could not explain consistently the growth patterns observed despite some traits varying with latitude (e.g., leaf nitrogen content decreased with latitude and C:N ratio increased) and/or simulated herbivory. : growth is not affected by increases in simulated herbivory and may be relatively resilient to future increases in seagrass consumption, suggesting that this species could be a relative 'winner' under future climate change conditions that lead to enhanced herbivory.
热带草食性鱼类向温带纬度的极向范围扩张正导致一些地区海洋栖息地的过度放牧和群落相位转移。在这里，我们测试了草食增加对温带栖息地形成海草的潜在影响。我们进行了一系列模拟草食实验，以预测气候介导的海草消费增加对澳大利亚东部整个纬度范围（约9°纬度）（1700公里海岸线）的潜在影响。我们对处理地块进行了两种水平的模拟草食（剪掉10%或80%的叶子），并将它们与未修剪的对照进行比较。我们测量了海草叶片的生长速率和组织化学特征：根茎中的碳水化合物、叶片酚类物质以及叶片和根茎中的营养物质（碳、氮和碳氮比）。在最温暖的范围边缘种群中，我们还测试了对草食增加的反应在夏季和冬季之间或随着重复修剪事件如何变化。尽管损失了高达80%的叶片生物量，但修剪后的枝条保持了与未修剪对照相似的生长速率。这在整个纬度范围内以及在最北端位置重复模拟草食后都是一致的。一次性修剪事件影响了植物结构，增加了细分枝条的数量。在物种范围边缘，叶片在冬季比夏季生长得更多，修剪往往仅在冬季降低海草生长；然而，夏季产生的枝条细分水平高于冬季。尽管一些特征随纬度（例如，叶片氮含量随纬度降低，碳氮比增加）和/或模拟草食而变化，但植物化学特征并不能始终如一地解释观察到的生长模式。：生长不受模拟草食增加的影响，并且可能对未来海草消费的增加具有相对的恢复力，这表明该物种在导致草食增加的未来气候变化条件下可能是一个相对的“赢家”。
