Zhu Jinlei, Lukić Nataša, Rajtschan Verena, Walter Julia, Schurr Frank M
Institute of Landscape and Plant Ecology University of Hohenheim Stuttgart Germany.
Institute of Soil Science and Land Evaluation University of Hohenheim Stuttgart Germany.
Ecol Evol. 2021 Nov 4;11(22):16239-16249. doi: 10.1002/ece3.8305. eCollection 2021 Nov.
Hydrology is a major environmental factor determining plant fitness, and hydrological niche segregation (HNS) has been widely used to explain species coexistence. Nevertheless, the distribution of plant species along hydrological gradients does not only depend on their hydrological niches but also depend on their seed dispersal, with dispersal either weakening or reinforcing the effects of HNS on coexistence. However, it is poorly understood how seed dispersal responds to hydrological conditions. To close this gap, we conducted a common-garden experiment exposing five wind-dispersed plant species (, , , , and ) to different hydrological conditions. We quantified the effects of hydrological conditions on seed production and dispersal traits, and simulated seed dispersal distances with a mechanistic dispersal model. We found species-specific responses of seed production, seed dispersal traits, and predicted dispersal distances to hydrological conditions. Despite these species-specific responses, there was a general positive relationship between seed production and dispersal distance: Plants growing in favorable hydrological conditions not only produce more seeds but also disperse them over longer distances. This arises mostly because plants growing in favorable environments grow taller and thus disperse their seeds over longer distances. We postulate that the positive relationship between seed production and dispersal may reduce the concentration of each species to the environments favorable for it, thus counteracting species coexistence. Moreover, the resulting asymmetrical gene flow from favorable to stressful habitats may slow down the microevolution of hydrological niches, causing evolutionary niche conservatism. Accounting for context-dependent seed dispersal should thus improve ecological and evolutionary models for the spatial dynamics of plant populations and communities.
水文是决定植物适应性的主要环境因素，水文生态位分离（HNS）已被广泛用于解释物种共存。然而，植物物种沿水文梯度的分布不仅取决于它们的水文生态位，还取决于它们的种子传播，传播可能会削弱或增强HNS对共存的影响。然而，人们对种子传播如何响应水文条件却知之甚少。为了填补这一空白，我们进行了一项共同花园实验，将五种风媒传播的植物物种（、、、和）置于不同的水文条件下。我们量化了水文条件对种子产量和传播特征的影响，并用一个机械传播模型模拟了种子传播距离。我们发现种子产量、种子传播特征以及预测传播距离对水文条件存在物种特异性响应。尽管存在这些物种特异性响应，但种子产量与传播距离之间存在普遍的正相关关系：生长在有利水文条件下的植物不仅产生更多种子，而且将它们传播到更远的距离。这主要是因为生长在有利环境中的植物长得更高，因此能将种子传播到更远的距离。我们推测，种子产量与传播之间的正相关关系可能会减少每个物种在对其有利的环境中的聚集，从而抵消物种共存。此外，如果出现从有利生境到压力生境的不对称基因流，可能会减缓水文生态位的微进化，导致进化生态位保守。因此，考虑到依赖环境的种子传播，应该可以改进植物种群和群落空间动态的生态和进化模型。
