Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, Kent, CT2 7NR, UK.
National Centre for Statistical Ecology, School of Mathematics, Statistics and Actuarial Science, University of Kent, Canterbury, Kent, CT2 7NF, UK.
Sci Rep. 2017 Nov 28;7(1):16491. doi: 10.1038/s41598-017-16534-8.
Biodiversity conservation requires reliable species assessments and rigorously designed surveys. However, determining the survey effort required to reliably detect population change can be challenging for rare, cryptic and elusive species. We used a tropical bromeliad-dwelling frog as a model system to explore a cost-effective sampling design that optimizes the chances of detecting a population decline. Relatively few sampling visits were needed to estimate occupancy and detectability with good precision, and to detect a 30% change in occupancy with 80% power. Detectability was influenced by observer expertise, which therefore also had an effect on the sampling design - less experienced observers require more sampling visits to detect the species. Even when the sampling design provides precise parameter estimates, only moderate to large changes in occupancy will be detected with reliable power. Detecting a population change of 15% or less requires a large number of sites to be surveyed, which might be unachievable for range-restricted species occurring at relatively few sites. Unless there is high initial occupancy, rare and cryptic species will be particularly challenging when it comes to detecting small population changes. This may be a particular issue for long-term monitoring of amphibians which often display low detectability and wide natural fluctuations.
生物多样性保护需要可靠的物种评估和精心设计的调查。然而，对于稀有、隐蔽和难以捉摸的物种，确定可靠地检测种群变化所需的调查力度可能具有挑战性。我们使用热带凤梨科附生蛙作为模型系统，探索了一种具有成本效益的抽样设计，该设计优化了检测种群下降的机会。相对较少的抽样访问就可以很好地估计占有率和可检测性，并以 80%的功效检测到 30%的占有率变化。可检测性受到观察员专业知识的影响，因此也会对抽样设计产生影响——经验较少的观察员需要更多的抽样访问才能检测到该物种。即使抽样设计提供了精确的参数估计，也只能以中等至较大的置信度检测到中等至较大的占有率变化。要检测到 15%或更少的种群变化，需要对大量地点进行调查，而对于在相对较少地点出现的分布范围有限的物种来说，这可能是无法实现的。除非初始占有率较高，否则稀有和隐蔽的物种在检测小种群变化时将特别具有挑战性。这可能是对通常显示出低可检测性和广泛自然波动的两栖动物进行长期监测的一个特别问题。
