All Hue products require a Hue Bridge (Gen 1 or Gen 2) to function. Hue bulbs, Hue Light strips, Hue Go, Hue Bloom, and all other Hue luminaires can be paired with Echo Dot, Echo, and Echo Tap only when used with Hue Gen 2 bridge (Gen 1 Bridge is not compatible)
All Hue products can connect directly to Echo Plus (without a Hue Bridge) though they will still need a Hue Bridge (Gen 1 or Gen 2) to be controlled via the Philips Hue App