At 1st level, the spire defender gains Combat Expertise and Dodge as bonus feats, even if he doesn’t meet the prerequisites.
Every class that grants a bonus feat should specify whether or not you need to meet the prerequisites. Usually, if you get one specific feat, you don’t need the prerequisites; if you get to pick off a list, you have to meet the prerequisites of the one you choose.
If a bonus feat specifies that you do not need to meet its prerequisites, that effectively changes the feat for you so that it does not have prerequisites. You can have it and use it without them.
If you do not meet the prerequisites of a (specific) bonus feat that requires you to meet them, then you get it but cannot use it (because you must meet a feat’s prerequisites to use it). If you do not meet the prerequisites of any of the feats on a list of bonus feats, then you get nothing (because you must meet a feat’s prerequisites to select it).