Imong Inaoyom, Robbins Martha M, Mundry Roger, Bergl Richard, Kühl Hjalmar S
Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany; Wildlife Conservation Society, Nigeria Program, Calabar, Cross River State, Nigeria.
Am J Primatol. 2014 Oct;76(10):978-88. doi: 10.1002/ajp.22287. Epub 2014 Apr 15.
Connectivity among subpopulations is vital for the persistence of small and fragmented populations. For management interventions to be effective conservation planners have to make the critical distinction between structural connectivity (based on landscape structure) and functional connectivity (which considers both landscape structure and organism-specific behavioral attributes) which can differ considerably within a given context. We assessed spatial and temporal changes in structural and functional connectivity of the Cross River gorilla Gorilla gorilla diehli (CRG) population in a 12,000 km(2) landscape in the Nigeria-Cameroon border region over a 23-year period, comparing two periods: 1987-2000 and 2000-2010. Despite substantial forest connections between occupied areas, genetic evidence shows that only limited dispersal occurs among CRG subpopulations. We used remotely sensed land-cover data and simulated human pressure (using a spatially explicit agent-based model) to assess human impact on connectivity of the CRG population. We calculated cost-weighted distances between areas occupied by gorillas as measures of connectivity (structural based on land-cover only, functional based on both land-cover and simulated human pressure). Whereas structural connectivity decreased by 5% over the 23-year period, functional connectivity decreased by 11%, with both decreasing more during the latter compared to the earlier period. Our results highlight the increasing threat of isolation of CRG subpopulations due to human disturbance, and provide insight into how increasing human influence may lead to functional isolation of wildlife populations despite habitat continuity, a pressing and common issue in tropical Africa often not accounted for when deciding management interventions. In addition to quantifying threats to connectivity, our study provides crucial evidence for management authorities to identify actions that are more likely to be effective for conservation of species in human-dominated landscapes. Our approach can be easily applied to other species, regions, and scales.
亚种群之间的连通性对于小型和碎片化种群的存续至关重要。为使管理干预措施行之有效，保护规划者必须在结构连通性（基于景观结构）和功能连通性（同时考虑景观结构和特定生物行为属性）之间做出关键区分，而在特定环境中，二者可能存在显著差异。我们评估了尼日利亚 - 喀麦隆边境地区一片12000平方公里景观中，克罗斯河大猩猩（Gorilla gorilla diehli，简称CRG）种群在23年期间（1987 - 2000年和2000 - 2010年两个时期）结构和功能连通性的时空变化。尽管已占据区域之间有大量森林连接，但遗传证据表明，CRG亚种群之间仅发生有限的扩散。我们使用遥感土地覆盖数据并模拟人类压力（使用基于空间明确的主体模型）来评估人类对CRG种群连通性的影响。我们计算了大猩猩占据区域之间的成本加权距离，以此作为连通性的度量（结构连通性仅基于土地覆盖，功能连通性基于土地覆盖和模拟人类压力两者）。在这23年期间，结构连通性下降了5%，而功能连通性下降了11%，且后期下降幅度均大于前期。我们的研究结果凸显了由于人类干扰导致CRG亚种群隔离的威胁日益增加，并深入了解了尽管栖息地具有连续性，但人类影响的增加如何可能导致野生动物种群的功能隔离，这是热带非洲一个紧迫且常见的问题，在决定管理干预措施时往往未被考虑。除了量化对连通性的威胁外，我们的研究为管理当局提供了关键证据，以确定在人类主导的景观中更有可能有效保护物种的行动。我们的方法可轻松应用于其他物种、区域和尺度。
