Stevens Virginie M, Leboulengé Eric, Wesselingh Renate A, Baguette Michel
Biodiversity Research Centre, Catholic University of Louvain, Croix du Sud 4, Louvain-la-Neuve, 1348, Belgium.
Oecologia. 2006 Nov;150(1):161-71. doi: 10.1007/s00442-006-0500-6. Epub 2006 Aug 3.
Like other pond-breeding amphibians, the natterjack toad (Bufo calamita) typically presents a patchy distribution. Because the species experiences high probabilities of local population extinction, its persistence within landscapes relies on both local and landscape-scale processes [dispersal allowing the (re)colonization of habitat patches]. However, the structure and composition of the matrix surrounding local populations can alter the dispersal rates between populations. As shown previously (Landscape Ecol 19:829-842, 2004), the locomotor performances of individuals at the dispersal stage depend on the nature of the component crossed: some landscape components offer high resistance to movement (high resistance or high viscosity components) whereas others allow high efficiency of movement (low resistance components). We now examine the ability of individuals to discriminate between landscape components and select low-resistance components. Our experimental study investigates the ways in which young natterjack toads choose from among landscape components common to southern Belgium. Toadlets (the dispersal stage) were experimentally confronted with boundaries between surrogates of sandy soils, roads, forests, agricultural fields and intensive pastures. Our results show: 1 the ability of toadlets to react to boundaries between landscape components, 2 differences in permeability among boundaries, and 3 our inability to predict correctly the permeability of the boundaries from the patch-specific resistance assessed previously. Toadlets showed a preference for bare environments and forests, whereas they avoided the use of agricultural environments. This pattern could not be explained in terms of patch-specific resistance only, and is discussed in terms of mortality risks and resource availability in the various landscape components, with particular attention to repercussions on conservation strategies.
与其他在池塘繁殖的两栖动物一样，黄条蟾蜍（Bufo calamita）通常呈现出斑块状分布。由于该物种局部种群灭绝的概率很高，其在景观中的存续依赖于局部和景观尺度的过程[扩散使栖息地斑块得以（重新）定殖]。然而，局部种群周围基质的结构和组成会改变种群之间的扩散速率。如先前所示（《景观生态学》19:829 - 842，2004年），处于扩散阶段的个体的运动表现取决于所穿越成分的性质：一些景观成分对移动具有高抗性（高抗性或高粘性成分），而其他成分则允许高效移动（低抗性成分）。我们现在研究个体区分景观成分并选择低抗性成分的能力。我们的实验研究调查了幼年黄条蟾蜍在比利时南部常见的景观成分中进行选择的方式。幼蟾蜍（扩散阶段）在实验中面对沙地、道路、森林、农田和集约化牧场的替代物之间的边界。我们的结果表明：1.幼蟾蜍对景观成分之间边界做出反应的能力；2.边界之间渗透性的差异；3.我们无法根据先前评估的斑块特定抗性正确预测边界的渗透性。幼蟾蜍表现出对裸露环境和森林的偏好，而它们避免使用农业环境。这种模式不能仅用斑块特定抗性来解释，并且将根据各种景观成分中的死亡风险和资源可用性进行讨论，并特别关注对保护策略的影响。
