Resting height of arboreal Littoraria in mangrove ecosystem

In April 2017, a preliminary experiment was conducted near transect C. Firstly, we captured the elevation changes across the transect using a Global Navigation Satellite System-Real Time Kinematic GPS (G970 GNSS RTK, UniStrong Inc.) with a 5-10 meters distance interval, standardizing all elevation data to a baseline where the local mean sea level was set to zero. We established sites at 25 cm vertical intervals within an elevation range of 0-150 cm. At each site, plots with 5×5 m² were established, then we recorded the resting height of all observed arboreal mollusks, identifying and removing each individual post-recording to prevent duplicate records. Upon completing each plot survey, these individuals were released. This pre-experiment surveyed a total of nine plots. Through data analysis, we selected three Littoraria species, L. ardouiniana, L. melanostoma and L. scabra, as the focal species for subsequent surveys due to their widespread presence, high frequency, and abundance within the study area. These three species are easily distinguishable morphologically, which minimized the risk of potential misidentification. During this survey, we found that at each site, it became difficult to discover new individuals after about 40 minutes to 1 hour of observation. Following the same methodology, six transects were established in July 2018, spanning approximately 400-700 meters each. Due to variations in the length and elevation changes of each transect, 4-9 plots were set up along each, totaling 36 plots. PVC pipes were used to mark the corners of each plot. In December 2018, these 36 plots were surveyed again. Each survey point was assigned three volunteers, comprising two groups in total; each location was searched for over 40 minutes.2017年4月，我们于C样带附近开展预实验。首先，采用全球导航卫星系统实时动态差分GPS（Global Navigation Satellite System-Real Time Kinematic GPS，型号G970 GNSS RTK，合众思壮（UniStrong Inc.）生产），以5-10米的间距采集该样带的高程变化数据，并将所有高程数据统一归化至以当地平均海平面为零点的基准面。我们在0至150厘米的高程范围内，以25厘米的垂直间隔设置采样点。于每个采样点内布设5×5平方米的样方，随后记录所有观测到的树栖软体动物的栖息高度；记录完成后，对每一个体进行识别并移除，以避免重复记录。每块样方调查结束后，将所采集的个体放归原地。本次预实验共调查9个样方。通过数据分析，我们选取滨螺属（Littoraria）的3个物种——阿氏滨螺（L. ardouiniana）、黑口滨螺（L. melanostoma）及粗糙滨螺（L. scabra）——作为后续调查的目标类群，原因在于它们在研究区域内分布广泛、出现频率高且种群丰度可观。这三个物种形态特征易于区分，最大程度降低了潜在的误识别风险。本次预调查发现，在每个采样点开展约40分钟至1小时的观测后，便难以发现新的个体。2018年7月，我们沿用相同方法布设6条样带，每条样带长度约为400至700米。由于各条样带的长度与高程变化存在差异，每条样带沿线设置4至9个采样点，总计36个样方。使用PVC管标记每个样方的四个角。2018年12月，我们对这36个样方再次开展调查。每个调查点位安排三名志愿者，分为两组开展工作；每个点位的搜寻时长均超过40分钟。