Ferrenberg Scott, Martinez Alexander S, Faist Akasha M
Department of Ecology and Evolutionary Biology, University of Colorado at Boulder , Boulder , CO , United States.
Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO, United States; Department of Biological Sciences, Purdue University, West Lafayette, IN, United States.
PeerJ. 2016 Oct 13;4:e2545. doi: 10.7717/peerj.2545. eCollection 2016.
Understanding patterns of biodiversity is a longstanding challenge in ecology. Similar to other biotic groups, arthropod community structure can be shaped by deterministic and stochastic processes, with limited understanding of what moderates the relative influence of these processes. Disturbances have been noted to alter the relative influence of deterministic and stochastic processes on community assembly in various study systems, implicating ecological disturbances as a potential moderator of these forces.
Using a disturbance gradient along a 5-year chronosequence of insect-induced tree mortality in a subalpine forest of the southern Rocky Mountains, Colorado, USA, we examined changes in community structure and relative influences of deterministic and stochastic processes in the assembly of aboveground (surface and litter-active species) and belowground (species active in organic and mineral soil layers) arthropod communities. Arthropods were sampled for all years of the chronosequence via pitfall traps (aboveground community) and modified Winkler funnels (belowground community) and sorted to morphospecies. Community structure of both communities were assessed via comparisons of morphospecies abundance, diversity, and composition. Assembly processes were inferred from a mixture of linear models and matrix correlations testing for community associations with environmental properties, and from null-deviation models comparing observed vs. expected levels of species turnover (Beta diversity) among samples.
Tree mortality altered community structure in both aboveground and belowground arthropod communities, but null models suggested that aboveground communities experienced greater relative influences of deterministic processes, while the relative influence of stochastic processes increased for belowground communities. Additionally, Mantel tests and linear regression models revealed significant associations between the aboveground arthropod communities and vegetation and soil properties, but no significant association among belowground arthropod communities and environmental factors.
Our results suggest context-dependent influences of stochastic and deterministic community assembly processes across different fractions of a spatially co-occurring ground-dwelling arthropod community following disturbance. This variation in assembly may be linked to contrasting ecological strategies and dispersal rates within above- and below-ground communities. Our findings add to a growing body of evidence indicating concurrent influences of stochastic and deterministic processes in community assembly, and highlight the need to consider potential variation across different fractions of biotic communities when testing community ecology theory and considering conservation strategies.
了解生物多样性模式是生态学中一个长期存在的挑战。与其他生物类群类似，节肢动物群落结构可由确定性和随机性过程塑造，而对于调节这些过程相对影响的因素了解有限。在各种研究系统中，干扰已被指出会改变确定性和随机性过程对群落组装的相对影响，这表明生态干扰是这些作用力的一个潜在调节因素。
利用美国科罗拉多州落基山脉南部亚高山森林中由昆虫导致树木死亡的5年时间序列形成的干扰梯度，我们研究了地上（地表和凋落物活动物种）和地下（在有机和矿质土壤层活动的物种）节肢动物群落组装过程中群落结构的变化以及确定性和随机性过程的相对影响。通过陷阱诱捕器（地上群落）和改良的温克勒漏斗（地下群落）对时间序列中的所有年份进行节肢动物采样，并分类到形态物种。通过比较形态物种丰度、多样性和组成来评估两个群落的群落结构。从线性模型和测试群落与环境属性关联的矩阵相关性的混合分析中，以及从比较样本间观察到的与预期的物种周转水平（β多样性）的零偏差模型中推断组装过程。
树木死亡改变了地上和地下节肢动物群落的结构，但零模型表明地上群落经历了更大的确定性过程相对影响，而地下群落中随机性过程的相对影响增加。此外，曼特尔检验和线性回归模型揭示了地上节肢动物群落与植被和土壤属性之间存在显著关联，但地下节肢动物群落与环境因素之间无显著关联。
我们的结果表明，干扰后，在空间上同时存在的地面节肢动物群落的不同部分，随机和确定性群落组装过程的影响取决于具体环境。这种组装过程的变化可能与地上和地下群落中不同的生态策略和扩散速率有关。我们的发现进一步证明了随机和确定性过程在群落组装中同时发挥作用，并强调在检验群落生态学理论和考虑保护策略时，需要考虑生物群落不同部分的潜在差异。
