Hybridisation between introduced and native species is an increasingly important issue concerning environmental stakeholders because it decreases genetic integrity of native stocks. However, hybridisation could also happen between non-native species even if these species belong to different genera. Our study illustrates this particular aspect of alien species invasion with the attempt of artificial hybridisation between sunbleak Leucaspius delineatus and topmouth gudgeon Pseudorasbora parva, both recent additions to the freshwater fish fauna of England. The crossed fertilisation of L. delineatus ova with P. parva sperm lead to viable eggs with a very high hatching rate of 86% although hybrids failed to develop beyond the 1st larval step. Early morphological development of these hybrids was quantified and compared to the early development of the pure bred species.
The impacts of aquatic invasive species vary from the population to ecosystem level most strikingly through modifications to native communities, often leading to a decline in native species. A primary impact mechanism is competitive displacement of native by invasive species through resource partitioning. However, the trophic interactions between native and invasive species occupying the same habitat remain poorly understood, particularly at the early stages of invasion. This study used stable isotope analysis of two co-occurring populations of invasive topmouth gudgeon, Pseudorasbora parva and native Caucasian dwarf goby, Knipowitschia caucasica in a highly productive shallow lake to characterize overlap of potential trophic niches. The trophic niches of both species were divergent, with no overlap. Mixing models suggest some inter-specific dietary differences. The trophic niche of the Caucasian dwarf goby was slightly and non-significantly larger than that of topmouth gudgeon. These results suggest that when introduced outside of their natural range, topmouth gudgeon might integrate into new fish communities via the exploitation of resources that are underexploited by native fishes, which could also explain the high invasion success of the species.