Comparative Cytogenetic Study of Y Chromosomes in Bovidae: Insights from Morphological Analysis of European Bison, American Bison, and Domestic Cattle.

In this study, we examined Y chromosome morphology in three species: European bison (Bison bonasus), American bison (Bison bison), and domestic cattle (Bos taurus). Peripheral blood lymphocytes were cultured, and C-banded metaphase preparations were analyzed to measure key Y chromosome parameters-absolute and relative length, absolute and relative area, and heterochromatin (C-band) content-using ImageJ software (ver. 1.54p). All traits deviated from normality (Shapiro-Wilk, p < 0.05). Non-parametric analyses revealed significant interspecific differences, with the strongest effects observed for C-band, followed by absolute and relative length. Principal Component Analysis (PCA) indicated a two-class structure, where domestic cattle formed a distinct cluster, while European and American bison grouped closely but remained separable. Linear Discriminant Analysis (LDA) achieved high classification accuracy (0.94), with misclassifications limited to American versus European bison. Generalized Linear Model (GLM) analyses further confirmed a strong species effect on C-band content (R2 = 0.916). These results identify the C-band as the most powerful discriminant, providing robust morphological differentiation among the three species and demonstrating the value of Y chromosome morphometry for comparative cytogenetic studies. Due to the limited sample size of American bison (n = 2), interpretations for this species should be made with caution.