Maitz Wendy E, Dickman Chris R
Institute of Wildlife Research, School of Biological Sciences, University of Sydney, 2006, NSW, Australia.
Oecologia. 2001 Aug;128(4):526-538. doi: 10.1007/s004420100689. Epub 2001 Aug 1.
This study investigates patterns of habitat use and competition in sympatric populations of the bush rat, Rattus fuscipes, and swamp rat, R. lutreolus, in the Blue Mountains National Park, New South Wales, Australia. Radiotracking showed that the home ranges of R. fuscipes tended to occupy woodland more than those of R. lutreolus, whereas use of heath and sedgeland by both species was equal. Home range overlaps were less between the two species than between individuals of R. lutreolus. Trap-captures showed that both species used structurally complex microhabitats, but also that R. fuscipes occupied relatively drier sites with denser leaf litter and taller canopy than R. lutreolus. In a field enclosure containing equal parts dense sedge and woodland, both species spent most time in the sedge. R. lutreolus frequently initiated agonistic behaviour and dominated its smaller congener; subordinate individuals fled or vocalized loudly. To test whether the observed patterns of habitat use of R. fuscipes resulted from habitat selection or competition with R. lutreolus, a field experiment was carried out in which the latter species was removed from two study sites but maintained in two controls. Following removal, the capture rate of R. fuscipes increased some 6.5-fold in sedgeland habitat that had been occupied formerly by R. lutreolus, while capture rates in sedge in the control sites remained unchanged. The rapidity of the habitat shift implicates current or intense competition, mediated by interference. Although interference is a costly process, it may benefit the dominant R. lutreolus by allowing priority of access to preferred moist habitats containing important food or shelter resources. Conversely, R. fuscipes may tolerate interference if it benefits from even temporary access to moist habitats, can reliably detect and avoid R. lutreolus prior to encounters, or has access to drier woodland areas under-used by the dominant species. We suggest finally that extensive gene flow in R. fuscipes may preclude adaptive shifts in habitat preferences in local populations that are sympatric with R. lutreolus, thus reducing the importance of competition but maintaining its intensity over time.
本研究调查了澳大利亚新南威尔士州蓝山国家公园中同域分布的灌丛鼠（Rattus fuscipes）和沼泽鼠（R. lutreolus）种群的栖息地利用模式及竞争情况。无线电追踪显示，灌丛鼠的活动范围比沼泽鼠更倾向于占据林地，而两种鼠类对石南灌丛和莎草湿地的利用程度相当。两种鼠类之间的活动范围重叠程度小于沼泽鼠个体之间的重叠程度。陷阱捕获结果表明，两种鼠类都利用结构复杂的微生境，但灌丛鼠所占据的地点相对更干燥，落叶层更茂密，树冠层也比沼泽鼠更高。在一个由等量茂密莎草和林地组成的野外围栏中，两种鼠类大部分时间都待在莎草区域。沼泽鼠频繁引发攻击行为并支配其体型较小的同类；处于从属地位的个体会逃离或大声鸣叫。为了测试观察到的灌丛鼠栖息地利用模式是由栖息地选择还是与沼泽鼠的竞争导致的，进行了一项野外实验，在两个研究地点移除了沼泽鼠，但在两个对照地点保留了该物种。移除后，在先前被沼泽鼠占据的莎草湿地栖息地中，灌丛鼠的捕获率增加了约6.5倍，而对照地点莎草区域的捕获率保持不变。栖息地转变的迅速性表明存在当前或激烈的竞争，这种竞争是由干扰介导的。尽管干扰是一个代价高昂的过程，但它可能使占主导地位的沼泽鼠受益，因为它能够优先获取含有重要食物或庇护资源的优质潮湿栖息地。相反，如果灌丛鼠能从偶尔进入潮湿栖息地中受益，在相遇前能可靠地察觉并避开沼泽鼠，或者能够利用优势物种较少使用的较干燥林地，那么它可能会容忍这种干扰。我们最终认为，灌丛鼠中广泛的基因流动可能会阻止与沼泽鼠同域分布的当地种群在栖息地偏好上发生适应性转变，从而降低竞争的重要性，但随着时间推移维持其强度。
