A morphometric and genetic comparison of Sinanodonta woodiana (Lea, 1834) populations: does shape really matter?

Sinanodonta woodiana (Lea, 1834) is an invasive species which has spread rapidly across Europe over the last few decades. Although it is already well established throughout Italy (both in lakes and in rivers), during a regular monitoring of the mussel communities in Northern Italy, this species was found for the first time in the fluvial natural reserve of Ghiaia Grande (Po River basin). The strong differences in shell shape between these specimens and those from Lake Maggiore prompted a genetic comparison based on DNA barcoding analyses to establish whether specimens from both sites belong to the same species. Our results confirm that the wide shell plasticity may help to explain the role of environmental factors in driving shells' morphology. Additionally, it may also induce S. woodiana misidentification with the native Anodonta sp. This fact may have strong negative implications for freshwater conservation if on one hand, the native species distribution is falsely over represented; or on the other hand, if the invasive species has a much wider distribution than predicted.