Quantitative modeling method for geolocating pollen samples

Pollen producing plants are present on every continent and the taxa of these plans can be distinguished based on the pollen grains. As a pollen assemblage can only come from a vegetation that produces the pollen types in that assemblage, pollen can give an indication of vegetation composition. Knowing the assemblage that produced a specific sample can be used to determine the origins of pollen on objects of interest such as footwear, drugs and poached goods. Most studies that used forensic palynology for geolocation were qualitative analyses of regions with low biodiversity. None are studies on a continental scale that involve the tropics. There is a need for objective qualitative forensic methods, which are expected to be effective and efficient with both high and low biodiversity regions. In this study a qualitative modeling method was developed using pollen samples from 705 neotropical sites and tested on pollen samples from 55 European sites. These samples came from pollen traps, soil samples, mud water interfaces of lakes and rivers, and moss samples. Ensemble species distribution models based on presence data were run for all genera present in these samples. The predicted range of all genera present in each individual sample were combined to produce a predicted range of origin of the site. A rate of 89.9% of all Neotropical sites was correctly predicted. The highest accuracy was achieved with samples from pollen traps, which were correct in 96.2% of cases. The results of European and Neotropical sites of the same sample origin were comparable. The results indicate that qualitative analysis can be accurate and efficient in the tropics at a continental scale. This file contains all used data and R scripts. With the contents the results can be recreated. Instructions on use are enclosed产花粉植物遍布各大陆，其类群可通过花粉粒加以区分。由于花粉组合仅能来自包含该组合内所有花粉类型的植被，因此花粉可用于指示植被组成。通过识别特定样本对应的花粉组合，可确定鞋类、药品、走私货物等目标物品上附着花粉的来源地。以往利用法医孢粉学（forensic palynology）进行地理溯源的研究，多为生物多样性较低区域的定性分析，尚无针对包含热带区域的大陆尺度研究。当前亟需客观的定性法医分析方法，以期在高、低生物多样性区域均能实现高效精准的溯源。 本研究基于705个新热带区点位的花粉样本开发了一种定性建模方法，并利用55个欧洲点位的花粉样本对该方法进行了测试。样本来源包括花粉陷阱、土壤样本、河湖泥水界面样本以及苔藓样本。针对样本中包含的所有属级类群，基于存在数据构建了集成物种分布模型。将单一样本中各属的潜在分布范围进行整合，即可得到该样本对应点位的预测起源范围。本方法对新热带区点位的正确预测率达89.9%，其中花粉陷阱样本的预测准确率最高，达96.2%。欧洲与新热带区同来源样本的测试结果相当，表明定性分析方法在大陆尺度的热带区域同样具备精准性与高效性。 本文件包含本次研究使用的全部数据与R脚本，可复现本次研究的全部结果，使用说明已随附其中。