Left: estimates of the local volume density (ρ₁₀) versus the local surface density (Σ₁₀) for the MATLAS traditional dwarf (non-UDG) galaxies (gray circles) and UDGs (green squares). The tidally disrupted UDGs and TDG UDGs discussed in Sect. 7 are marked in turquoise and yellow, respectively. The density estimates were calculated based on the tenth-nearest neighbor, using only the massive galaxies from the ATLAS^3D parent sample. Cappellari et al. (2011b) noted that nearly all galaxies in the Virgo cluster have log₁₀ρ₁₀ > −0.4 and log₁₀Σ₁₀ > 0.4; these boundaries are marked with dashed lines. The open ovals indicate where the dwarfs in select groups fall in the plot. Right: radial distribution of traditional dwarf (non-UDG) galaxies (filled gray) and UDGs (hashed green) in the group environments defined in Table 1. The projected group-centric distances have been normalized such that R_vir = 1. A KS test returns a p-value of 0.35, thus we cannot reject the null-hypothesis that the two samples originate from the same parent sample.