Species and their interactions are more dynamic over time and space in fragmented habitats than in continuous habitats. In fragmented habitats, the low nestedness of mutualistic networks may be related to the position change of stable (high persistence over time/space) species and interactions in the networks. Previous studies have shown that stable species and interactions tend to be in the core position of mutualistic networks. However, in fragmented habitats, it remains unknown whether stable species or interactions still tend to be in the core position. To address this gap, here we evaluated the correlation between the position of proximity to the network core and the temporal/spatial stability of species and interactions, using the observation of 42 plant–pollinator networks conducted in a fragmented island landscape over 3 years. We showed that temporally/spatially stable species and interactions deviated from the network core to varying degrees. Temporally stable plants were most likely to deviate from the network core, followed by pollinators and interactions, while only spatially stable pollinators tend to deviate from the network core. When unstable species (present in few time/space points, typically specialists) and interactions occupy the network core, they cannot interact with most species in the network as generalists do, resulting in the decrease of network nestedness. Therefore, from the perspective of position and stability, stable species and interactions deviate from the network core in fragmented habitats, which is an important reason for the decrease of nestedness in mutualistic networks. Our study suggests that protecting plants which occupy the core in large plant–pollinator networks is essential for maintaining the network persistence in fragmented habitats.

中文翻译：

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植物 - 传粉者网络中的稳定物种和相互作用偏离了分散生境中的核心位置

在分散的栖息地中，物种及其相互作用随着时间和空间的变化比在连续的栖息地中更具动态性。在碎片化的栖息地中，互惠网络的低嵌套性可能与稳定（随时间/空间的高持久性）物种的位置变化和网络中的相互作用有关。以往的研究表明，稳定的物种和相互作用往往处于互惠网络的核心位置。然而，在支离破碎的栖息地中，稳定的物种或相互作用是否仍然倾向于处于核心位置仍然未知。为了解决这一差距，我们在此评估了靠近网络核心的位置与物种和相互作用的时间/空间稳定性之间的相关性，使用在 3 年内在零散的岛屿景观中进行的 42 个植物-传粉媒介网络的观察。我们发现时间/空间稳定的物种和相互作用在不同程度上偏离了网络核心。时间稳定的植物最有可能偏离网络核心，其次是传粉媒介和相互作用，而只有空间稳定的传粉媒介倾向于偏离网络核心。当不稳定的物种（存在于少数时间/空间点，通常是专家）和相互作用占据网络核心时，它们无法像通才那样与网络中的大多数物种相互作用，导致网络嵌套性降低。因此，从位置和稳定性的角度来看，稳定的物种和相互作用在碎片化生境中偏离了网络核心，这是互惠网络中嵌套性降低的重要原因。