is a specific kind of: hamamelid dicot genus.

has as a member: alder, alder tree | Alnus glutinosa, Alnus vulgaris, common alder, European black alder | Alnus incana, gray alder, grey alder | Alnus maritima, seaside alder | Alnus rhombifolia, mountain alder, white alder | Alnus rubra, Oregon alder, red alder | Alnus rugosa, speckled alder | Alnus serrulata, hazel alder, smooth alder | Alnus veridis, green alder | Alnus crispa, Alnus veridis crispa, green alder.

is a member of: Betulaceae, birch family, family Betulaceae.