Whisk together the pomegranate juice, vinegar, mustard, honey, lime and orange zest and poppy seeds in a medium bowl and season with salt and pepper. Slowly whisk in the oil until emulsified.
Put the citrus in a bowl; add the jicama and watercress. Add a few tablespoons of the reserved citrus juices and some of the pomegranate dressing, season with salt and pepper and toss to coat. Transfer to a platter and garnish with the pomegranate seeds.