To JEEP-
You can get more information on the staggering diversity of animal sexuality and reproductive strategies from Bruce Bagemihl's
http://www.amazon.com/Biological-Exuberance-Homosexuality-Natural-Diversity/dp/0312192398.
Also Joan Roughgarden's
http://www.amazon.com/Evolutions-Rainbow-Diversity-Gender-Sexuality/dp/0520260120/ref=pd_sim_b_1.
Both of these are not strictly scientific tomes. However, both are very enlightening and will make you think quite a bit about previous assumptions regarding the presumed "natural" order of things.
For example, transgendered organisms and reproduction are not necessarily exclusive. Many North American freshwater sunfish, (Centrarchidae) travel in sex-segregated schools much of the year. When the spring mating season arrives, the female schools find males that have made up gravel beds for protection of the eggs. Males, especially first timers; can be very aggressive in their courtships towards females, scaring them off. This has opened up a niche. The female schools are
not exclusive female, up to half of the "female" schools may be made up of "female-mimicking males".
During the reproductive season, these transgendered males come into their own. They are very tolerant of the larger, gravel nesting males and vice-versa. The transgendered male rebuffs and nips the gravel-nesting male into proper courtship behavior. They both will undergo the full range of courtship, even spawning some milt together into the gravel nest. This is in full view of the females in the school. Eventually, a female loses her fear and accompanies both males in a triad courtship. Both males and the female release their roe and milt into the gravel bed nursery at the climax of courtship. While only the gravel bed male will put in the hard work of protecting the eggs and young, he has no compunctions about the transgendered male breeding along with him. He will raise the transgendered male's offspring as his own. In terms of natural and sexual selection, this strategy works very well; as up to 20% (likely much higher) of all reproductive courtships and matings are done this way.
In other words, this is a cooperative sexual/reproductive act which guarantees that all members of the triad have a shot at reproduction. Especially aggressive Gravel nesting males may be a good reproductive choice for both the transgendered males and the females because they are much more likely to defend the precious offspring from egg-predators.