Data from: Two for the price of one: eDNA metabarcoding reveals temporal and spatial variability of mussel and fish co-distributions in Michigan riverine systems

Freshwater mussels (family Unionidae) are among the world’s most
endangered taxa, with almost 75% of North American taxa classified as a
species of concern, threatened, or endangered. Despite the critical
importance of comprehensive distributional data for the conservation of
unionids and fishes, these data are often lacking because of the labor and
resources associated with traditional survey methods. During their larval
stage, unionid mussels use various fish species as obligate hosts, making
native fish species vital to unionid persistence and an understanding of
host distribution similarly important. Here, we utilized an eDNA
metabarcoding approach to evaluate patterns of co-distribution of unionid
mussels and fishes along ~362 km of the densely sampled Grand River
network as well as the outlets of 19 tributaries along the eastern shore
of Lake Michigan, USA. We detected a total of 21 mussel and 40 fish taxa,
with distinctive composition of both mussel and fish assemblages across
tributaries and differences in fish taxa between sampling periods.
Notably, we detected more mussel taxa within the Grand River watershed
than at the outlets of all 20 rivers combined. Within the Grand River
network, two fish taxa (Pylodictus olivaris and Cyprinella) were found
more frequently in areas of high mussel diversity, and three fish taxa
more frequently in areas of low mussel diversity (Umbra, Leuciscidae, and
Etheostoma). There was little difference between eDNA detections of
mussels from samples collected in June versus August, but we detected
significantly more fish taxa in August compared to June. Taken together,
our findings demonstrate the value of eDNA metabarcoding for evaluating
co-distribution of ecologically connected taxa. The use of eDNA as a tool
for determining distributions of mussels and their obligate hosts may
facilitate conservation efforts for these imperiled taxa.

蚌科（Unionidae）淡水蚌类是全球最濒危的类群之一，北美近75%的蚌类类群被列为受关注、受威胁或濒危物种。尽管全面的分布数据对于蚌类与鱼类的保护至关重要，但由于传统调查方法所需的人力与资源投入，这类数据往往较为匮乏。蚌类在幼虫阶段以多种鱼类作为专性宿主，因此本土鱼类对于蚌类的存续至关重要，而了解宿主的分布同样意义重大。本研究采用环境DNA（eDNA）元条形码技术，对美国密歇根湖东岸19条支流河口以及密采样的格兰德河（Grand River）水系约362公里河段内的蚌类与鱼类的共分布模式进行了评估。本次检测共发现21种蚌类与40种鱼类类群，不同支流的蚌类与鱼类群落组成均存在显著差异，且不同采样时段的鱼类类群组成也有所不同。值得注意的是，格兰德河水系内检测到的蚌类类群数量，多于全部20条河流河口检测到的总和。在格兰德河水系内，2种鱼类类群（Pylodictus olivaris与Cyprinella）在蚌类多样性较高的区域出现频率更高，另有3种鱼类类群（Umbra、Leuciscidae与Etheostoma）在蚌类多样性较低的区域出现频率更高。6月与8月采集的样本中，蚌类的eDNA检测结果差异不大，但8月检测到的鱼类类群数量显著多于6月。综上，本研究结果证实了eDNA元条形码技术在评估生态关联类群共分布模式中的应用价值。利用eDNA技术确定蚌类及其专性宿主的分布，将有助于推动这些濒危类群的保护工作。