Mental Ray can use Maya built-in file textures, but sometimes using Mental Ray Textures have some advantages. Unlike Maya file, Mental Ray Textures cannot be connected to a material directly. They should be connected via some Texture Lookup node:
A mib_texture_filter_lookup node in this case. A mentalrayTexute node is connected to its tex, and a mib_texture_vector node is connected to its coord.
Image file is loaded in the mentalrayTexture node:
A mib_texture_vector produces the coordinate for texture lookup. UV coordinate is used by default. Select appears to be the index number of UV set, so select zero means the first UV set (map1), one is second, two is third, and so on.