Rassati Davide, Faccoli Massimo, Haack Robert A, Rabaglia Robert J, Petrucco Toffolo Edoardo, Battisti Andrea, Marini Lorenzo
Department of Agronomy, Food, Natural Resources, Animals, & Environment (DAFNAE), University of Padua, Legnaro (PD), Italy.
USDA Forest Service, Northern Research Station, Lansing, Michigan, United States of America.
PLoS One. 2016 Jul 26;11(7):e0158519. doi: 10.1371/journal.pone.0158519. eCollection 2016.
Non-native bark and ambrosia beetles represent a threat to forests worldwide. Their invasion patterns are, however, still unclear. Here we investigated first, if the spread of non-native bark and ambrosia beetles is a gradual or a discontinuous process; second, which are the main correlates of their community structure; third, whether those correlates correspond to those of native species. We used data on species distribution of non-native and native scolytines in the continental 48 USA states. These data were analyzed through a beta-diversity index, partitioned into species richness differences and species replacement, using Mantel correlograms and non-metric multidimensional scaling (NMDS) ordination for identifying spatial patterns, and regression on distance matrices to test the association of climate (temperature, rainfall), forest (cover area, composition), geographical (distance), and human-related (import) variables with β-diversity components. For both non-native bark and ambrosia beetles, β-diversity was mainly composed of species richness difference than species replacement. For non-native bark beetles, a discontinuous invasion process composed of long distance jumps or multiple introduction events was apparent. Species richness differences were primarily correlated with differences in import values while temperature was the main correlate of species replacement. For non-native ambrosia beetles, a more continuous invasion process was apparent, with the pool of non-native species arriving in the coastal areas that tended to be filtered as they spread to interior portions of the continental USA. Species richness differences were mainly correlated with differences in rainfall among states, while rainfall and temperature were the main correlates of species replacement. Our study suggests that the different ecology of bark and ambrosia beetles influences their invasion process in new environments. The lower dependency that bark beetles have on climate allowed them to potentially colonize more areas within the USA, while non-native ambrosia beetles, being dependent on rainfall, are typically filtered by the environment.
外来树皮甲虫和食菌小蠹对全球森林构成威胁。然而，它们的入侵模式仍不明确。在此，我们首先调查外来树皮甲虫和食菌小蠹的扩散是一个渐进过程还是不连续过程；其次，它们群落结构的主要相关因素有哪些；第三，这些相关因素是否与本土物种的相关因素一致。我们使用了美国大陆48个州外来和本土小蠹科物种分布的数据。通过β多样性指数对这些数据进行分析，将其分为物种丰富度差异和物种更替，使用Mantel相关图和非度量多维尺度（NMDS）排序来识别空间模式，并对距离矩阵进行回归分析，以检验气候（温度、降雨量）、森林（覆盖面积、组成）、地理（距离）和与人类相关（进口）变量与β多样性成分之间的关联。对于外来树皮甲虫和食菌小蠹，β多样性主要由物种丰富度差异而非物种更替构成。对于外来树皮甲虫，由长距离跳跃或多次引入事件组成的不连续入侵过程很明显。物种丰富度差异主要与进口值的差异相关，而温度是物种更替的主要相关因素。对于外来食菌小蠹，更连续的入侵过程很明显，外来物种库抵达沿海地区，在向美国大陆内部扩散时往往会受到筛选。物种丰富度差异主要与各州降雨量的差异相关，而降雨量和温度是物种更替的主要相关因素。我们的研究表明，树皮甲虫和食菌小蠹不同的生态特性影响它们在新环境中的入侵过程。树皮甲虫对气候的依赖性较低，这使它们有可能在美国境内更多地区定殖，而依赖降雨的外来食菌小蠹通常会受到环境筛选。
