**2. Materials and Methods**

### *2.1. Occurrence Data Collection*

Occurrence data were collected from the original datasets [22], collection materials (I. I. Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, Kyiv), GBIF databases [23,24]—all non-duplicate. We also studied the typical biotopes generally occupied by these fish species in Eastern Europe (Ukraine and Turkey) within 2012–2021 period of conducted field research (20 expeditions) (Figure 1). Fish were registered visually or caught by a manual fishing net (d = 2 mm) with subsequent species determination and release at the place of capture; the biotopes were photographed. To account for sampling bias, we used the nearest neighbor distance ('ntbox' package in R [25]) method to thin the data, where occurrence points that were ≤0.1 units away from each other were removed to avoid errors due to spatial autocorrelation. As a result, the number of points has significantly decreased; from 26,140 total points to 2278 for *G. holbrooki* and from 4200 points to 1410—for *P. reticulata.*

**Figure 1.** Biotope occupied by (**A**)—*P. reticulata* along the Bortnychi sewage drain (Ukraine, localities are marked with red circles); (**B**)—*G. holbrooki* is found in roadside fresh water bodies (Turkey).
