No, there is no "trunk ajar" light, which is one of my few minor complaints about the car.
But while there is no warning light on the dash, the alarm will tell you indirectly - if any of the doors, hood or trunk are not closed properly, you will not get the confirmation flash of the blinkers when you lock the car. (The flash indicates that the alarm has been armed, which won't happen unless everything's secure.)
1985 RX-7 GSL-SE
2004 RX-8 Winning Blue Sport Ordered 1/8/03; Delivered 7/25/03
; Returned 10/21/03
2005 RX-8 Velocity Red Sport delivered 12/05 returned at lease end 12/07