Rhodes Monika, Wardell-Johnson Grant W, Rhodes Martin P, Raymond Ben
Australian School of Environmental Studies, Griffith University, Nathan Campus, QLD 4111, Australia.
Conserv Biol. 2006 Jun;20(3):861-70. doi: 10.1111/j.1523-1739.2006.00415.x.
In Australia more than 300 vertebrates, including 43 insectivorous bat species, depend on hollows in habitat trees for shelter with many species using a network of multiple trees as roosts. We used roost-switching data on white-striped freetail bats (Tadarida australis; Microchiroptera: Molossidae) to construct a network representation of day roosts in suburban Brisbane, Australia. Bats were caught from a communal roost tree with a roosting group of several hundred individuals and released with transmitters. Each roost used by the bats represented a node in the network, and the movements of bats between roosts formed the links between nodes. Despite differences in gender and reproductive stages, the bats exhibited the same behavior throughout three radiotelemetry periods and over 500 bat days of radio tracking: each roosted in separate roosts, switched roosts very infrequently, and associated with other bats only at the communal roost. This network resembled a scale-free network in which the distribution of the number of links from each roost followed a power law. Despite being spread over a large geographic area (> 200 km2), each roost was connected to others by less than three links. One roost (the hub or communal roost) defined the architecture of the network because it had the most links. That the network showed scale-free properties has profound implications for the management of the habitat trees of this roosting group. Scale-free networks provide high tolerance against stochastic events such as random roost removals but are susceptible to the selective removal of hub nodes. Network analysis is a useful tool for understanding the structural organization of habitat tree usage and allows the informed judgment of the relative importance of individual trees and hence the derivation of appropriate management decisions. Conservation planners and managers should emphasize the differential importance of habitat trees and think of them as being analogous to vital service centers in human societies.
在澳大利亚，超过300种脊椎动物，包括43种食虫蝙蝠，依赖栖息树木的树洞作为庇护所，许多物种利用多棵树组成的网络作为栖息地。我们利用白纹无尾蝠（Tadarida australis；小蝙蝠亚目：犬吻蝠科）的栖息地转换数据，构建了澳大利亚布里斯班郊区日间栖息地的网络模型。蝙蝠从一棵有数百只个体栖息的群居栖息树上捕获，并安装发射器后放生。蝙蝠使用的每个栖息地代表网络中的一个节点，蝙蝠在栖息地之间的移动形成了节点之间的连接。尽管性别和繁殖阶段存在差异，但蝙蝠在三个无线电遥测周期和超过500个蝙蝠日的无线电跟踪中表现出相同的行为：每只蝙蝠都栖息在单独的栖息地，很少更换栖息地，并且只在群居栖息地与其他蝙蝠聚集。这个网络类似于无标度网络，其中每个栖息地的连接数分布遵循幂律。尽管分布在很大的地理区域（>200平方公里），但每个栖息地与其他栖息地的连接少于三条。一个栖息地（中心或群居栖息地）定义了网络的架构，因为它有最多的连接。该网络具有无标度特性，这对该栖息群体的栖息树木管理具有深远意义。无标度网络对随机事件（如随机移除栖息地）具有高耐受性，但容易受到枢纽节点的选择性移除影响。网络分析是理解栖息树木使用结构组织的有用工具，有助于明智地判断个别树木的相对重要性，从而做出适当的管理决策。保护规划者和管理者应强调栖息树木的不同重要性，并将它们视为类似于人类社会中的重要服务中心。
