DU Nature Studies and Environmental Education Centre, Vienības Str. 13, Daugavpils, 5401, Latvia.
Institute of Life Sciences and Technology, Daugavpils University, Coleopterological Research Center, Parades Str. 1a, Daugavpils, 5401, Latvia.
Sci Rep. 2023 Jun 15;13(1):9715. doi: 10.1038/s41598-023-36242-w.
Dytiscus latissimus (Coleoptera Dytiscidae) is an endangered diving beetle throughout its range. It is one of the two species of Dytiscidae listed in Annex II of the Habitats Directive, IUCN red list and in many national level legislations and therefore strictly protected. The conservation of endangered species first of all requires an assessment of their population size. Until now, a method has not been developed for estimating the size of D. latissimus populations. The article summarizes the results of two studies carried out independently in Germany and Latvia. Both studies were carried out in one water body used recapture method but with a different spatial placement of traps, which, according to our data, is an important factor in population estimation. We evaluated Jolly-Seber and Schnabel approaches of estimating aquatic beetle's populations and found that confidence intervals obtained by different methods in our research do not differ significantly, but combination of both models provide the most accurate estimates of population dynamics. As part of the study, we concluded that the populations of Dytiscus latissimus are relatively closed, so we accept that the Schnabel estimate shows more accurate data. By fixing the places of capture of each individual, it was found that females live mainly locally, and males actively move within the water body. This aspect indicates the advantage of the spatial placement of traps compared to the use of transects. The results of our study show a significantly higher number of both captured and recaptured males Such a sex ratio may indicate both a greater activity of males and differences in the sex ratio in the population. The study confirmed that environmental changes, such as the water level in a water body, can also significantly affect the result of a population assessment. In the frame of D. latissimus monitoring, to obtain an objective estimation of the species population size we recommend using four traps for each 100 m of water body shoreline with 4-8 censuses, dependently on the recapture rate.
宽纹龙虱（鞘翅目龙虱科）在其分布范围内是一种濒危的潜水甲虫。它是栖息地指令附件二、IUCN 红色名录以及许多国家立法中列出的两种龙虱科物种之一，因此受到严格保护。保护濒危物种首先需要评估其种群规模。到目前为止，还没有开发出一种方法来估计 D. latissimus 种群的大小。本文总结了在德国和拉脱维亚独立进行的两项研究的结果。这两项研究都是在一个水体中进行的，使用了重捕法，但陷阱的空间位置不同，根据我们的数据，这是种群估计的一个重要因素。我们评估了 Jolly-Seber 和 Schnabel 两种方法来估计水生甲虫的种群，并发现我们研究中不同方法获得的置信区间没有显著差异，但两种模型的结合可以提供最准确的种群动态估计。作为研究的一部分，我们得出结论，Dytiscus latissimus 的种群相对封闭，因此我们接受 Schnabel 估计显示出更准确的数据。通过固定每个个体的捕获地点，发现雌性主要在当地生活，而雄性在水体中积极移动。这一方面表明与使用样带相比，陷阱的空间布置具有优势。我们的研究结果表明，无论是捕获的还是重新捕获的雄性数量都明显更高。这种性别比例可能表明雄性的活动量更大，并且种群中的性别比例存在差异。该研究证实，环境变化，如水体水位，也会对种群评估结果产生重大影响。在 D. latissimus 监测框架内，为了对该物种的种群规模进行客观估计，我们建议在每 100 米水体岸边使用四个陷阱，并根据重捕率进行 4-8 次计数。
