Two new <i>Amphora</i> species from European rivers compared to morphologically similar species of the <i>Amphora copulata</i> complex (Catenulaceae, Bacillariophyceae)

<i>Amphora copulata</i> is a widely reported diatom name in water quality surveys throughout Europe. Following a survey of 1 000 floristic lists from the French part of the Rhine-Meuse basin (2000–2021), seven samples with the highest abundance of this species were selected for detailed examination-based on light (LM) and scanning electron microscopy (SEM) observations. In addition, samples from the Netherlands and Germany with a high abundance of the <i>Amphora copulata</i> species complex were also studied. The specimens previously identified as <i>A. copulata</i> sensu lato could not be assigned to an existing species based on the currently available literature, and proved to belong to two taxa described here as new: <i>Amphora vanderwerffiana</i> sp. nov. and <i>Amphora lucectoreana</i> sp. nov. The two new species are illustrated using both light and electron microscopy and compared to morphologically similar species. As such, type materials of <i>A. eileencoxiae</i> and <i>A. neglectiformis</i>, and recent material from the type locality of <i>A. macedoniensis</i> are also illustrated and discussed.