Kellogg Biological Station, Michigan State University, 3700 E Gull Lake Drive, Hickory Corners, Michigan, 49060, USA.
Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, 48109, USA.
Ecology. 2020 Oct;101(10):e03061. doi: 10.1002/ecy.3061. Epub 2020 Sep 8.
Seed dispersal and local filtering interactively govern community membership and scale up to shape regional vegetation patterns, but data revealing how and why particular species are excluded from specific communities in nature are scarce. This lack of data is a missing link between our theoretical understanding of how diversity patterns can form and how they actually form in nature, and it hampers our ability to predict community responses to climate change. Here, we compare seed, seedling, and adult plant communities at 12 grassland sites with different climates in southern Norway to examine how community membership is interactively shaped by seed dispersal and local filtering, and how this process varies with climate across sites. To do this, we divide species at each site into two groups: locally transient species, which occur as seeds but are rare or absent as adults (i.e., they arrive but are filtered out), and locally persistent species, which occur consistently as adults in annual vegetation surveys. We then ask how and why locally transient species are disfavored during community assembly. Our results led to four main conclusions: (1) the total numbers of seeds and species that arrived, but failed to establish locally persistent populations, rose with temperature, indicating an increase in the realized effects of local filtering on community assembly, as well as an increase in the number of species poised to rapidly colonize those warmer sites if local conditions change in their favor, (2) locally transient species were selectively filtered out during seedling emergence, but not during seedling establishment, (3) selective filtering was partly driven by species climate preferences, exemplified by the poor performance of seeds dispersing outside of their realized climate niches into colder and drier foreign climates, and (4) locally transient species had traits that likely made them better dispersers (i.e., smaller seeds) but poorer competitors for light (i.e., shorter statures and less persistent clonal connections) than locally persistent species, potentially explaining why these species arrived to new sites but did not establish locally persistent adult populations. Our study is the first to combine seed, seedling, and adult survey data across sites to rigorously characterize how seed dispersal and local filtering govern community membership and shape climate-associated vegetation patterns.
种子传播和局部过滤相互作用，共同决定群落组成，并扩展到塑造区域植被格局，但关于特定物种为何以及为何会被自然特定群落排斥的数据却很少。这种数据的缺乏是我们对多样性模式如何形成以及它们在自然界中实际如何形成的理论理解与实际之间缺失的一环，这也阻碍了我们预测群落对气候变化的反应的能力。在这里，我们比较了挪威南部 12 个具有不同气候的草原地点的种子、幼苗和成年植物群落，以研究群落组成如何通过种子传播和局部过滤相互作用形成，以及这一过程如何因地点而异。为此，我们将每个地点的物种分为两组：局地瞬态物种，它们以种子形式出现，但作为成体很少或不存在（即它们到达但被过滤掉），以及局地持久物种，它们在年度植被调查中始终作为成体存在。然后，我们询问局地瞬态物种在群落组装过程中为何以及为何处于不利地位。我们的研究结果得出了四个主要结论：（1）到达但未能建立局地持久种群的种子和物种总数随着温度的升高而增加，这表明局部过滤对群落组装的实际影响增加，以及如果当地条件有利于其变化，准备快速殖民这些温暖地区的物种数量增加；（2）局地瞬态物种在幼苗出现期间被选择性过滤掉，但在幼苗建立期间没有；（3）选择性过滤部分由物种的气候偏好驱动，例如，在更冷和更干燥的外来气候中，种子在其实际气候生态位之外传播的表现不佳；（4）局地瞬态物种具有使其成为更好的传播者的特征（即更小的种子），但在光竞争方面表现不佳（即更短的株高和较少的持久克隆连接），这可能解释了为什么这些物种到达新地点但未能建立局地持久的成年种群。我们的研究首次结合了种子、幼苗和成年调查数据，严格描述了种子传播和局部过滤如何控制群落组成并塑造与气候相关的植被格局。
