Words to Describe intergradation

How intergradation often is described ("________ intergradation")

• such
• secondary
• lateral
• chromosomal
• definite
• much
• apparent
• gradual
• geographical
• primary
• perfect
• little
• probable
• direct
• endless
• considerable
• true
• actual
• subspecific
• possible
• morphological
• continuous
• complete
• extensive