No abstract

This study examined the distribution and habitat selection of the invasive black bullhead [Ameiurus melas (Rafinesque)] in the ditches and surrounded temporary flooded habitats of an artificial wetland in western France. A multiscale approach was used to quantify patterns of A. melas abundance in relation to physical habitat characteristics in the ditch network. Young-of-the-year (YOY) and adult A. melas largely dominated the local fish assemblage but were highly variable among sites. Although we found evidence for some fine-scale habitat differences for YOY and adult individuals, the abundance of A. melas was positively and consistently related to the dominance of reed beds. Furthermore, A. melas preferentially used reed beds as opposed to marsh meadows during the flooding period. The results from this study suggest that the invasion of A. melas has been facilitated by the expansion of reed beds associated with the diminution of agricultural pressure in recent decades. This study represents an unusual example where human activities can have had an unexpected effect by facilitating an invasive fish species.

We assessed the mitochondrial DNA sequence divergence of a 718 bp fragment of the control region and 1007 bp of the cytochrome b gene between two allopatric morphologically different subspecies of bluethroat (Luscinia svecica). None of the 17 total haplotypes was shared between L. s. namnetum and L. s. svecica. However, the mean distances between subspecies were very low for both fragments (0.00168 +/- 0.00001 (mean +/- SE) for the control region; 0.00306 +/- 0.00016 for the cytochrome b gene). Only one substitution made the two subspecies genetically differentiated, highlighting their recent divergence. Interestingly, the control region was not more variable than the cytochrome b gene.