Conclusion
The Mighty Males hypothesis has several attractive properties. First and
foremost, it is simple, relying on only a few assumptions that are well
supported. Second, a common difficulty when applying the Bull-Charnov
Model to a given situation is that sex-specific benefits can be argued
from the perspective of advantaging males, or advantaging females, even
within the same species (e.g., compare Harlow and Taylor 2000; Warner
and Shine 2005). The Mighty Males hypothesis generates the same or very
similar predictions for every species, some of which already have good
support, and therefore the hypothesis can be tested unambiguously.
Finally, Mighty Males also implies that environmental factors other than
temperature may affect sex determination, even in species traditionally
known to exhibit TSD. The hypothesis may therefore help explain why
species simultaneously exhibit TSD and other forms of ESD as well. More
broadly, I suggest that our knowledge of TSD is less complete than is
currently appreciated, and I hope in earnest that the present essay
spurs further investigation into TSD and other forms of ESD in reptiles
and elsewhere, perhaps guided by some of the ideas that fall naturally
out of the Mighty Males hypothesis.
Acknowledgements: I sincerely thank Fred Janzen, Daniel Warner,
Locke Rowe, and Melanie Massey for feedback that greatly improved an
earlier draft of this paper. Funding was provided by an NSERC Discovery
grant to NR.