Lateral plate variation in Galician stickleback populations in the rivers Mino and Limia, NW Spain

We examined lateral plate variation in populations of stickleback, Gasteros teus aculeatus, from the rivers Mino and Limia in Galicia (Northwest Spain) , by analysing morphs, number of lateral plates, and position of the plates . In order to test for sexual dimorphism, the means and variances of plates were compared in males and females of some populations. No significant dif ferences were found between sexes, therefore all remaining populations were analysed without controlling fur sex. As stickleback populations in Galici a have an annual life span, the populations from the river Mino were divide d in two age groups to compare lateral plate number Analysis of each group revealed significant differences among populations, in accordance with the large amount of variation found in populations from other regions. Analysis of samples collected from the same place and at the same time of year, but in different years, indicated that there was little year to year variation . This suggests that populations are well adapted to their habitat, or that environmental conditions did not change significantly during, the period o f sampling. Finally, we propose a new method for the evaluation of scute variation anal ysis of the position of lateral plates. Cluster analysis of our data clearl y differentiated populations from the rivers Mino and Limia.