Sexually-selected male weapon increases the risk of population
extinction under environmental change: an experimental evidence
Exaggerated sexually-selected traits, occurring more commonly in males,
help individuals to increase reproductive success, but are costly to
produce and maintain. These costs on the one hand may improve population
fitness by intensifying selection against maladapted males, but on the
other hand may increase the risk of extinction under environmental
challenge. However, the impact of sexually selected traits on extinction
risk have not been investigated experimentally. We used replicate
populations of a male-dimorphic mite, Rhizoglyphus robini, to test if
prevalence of an elaborate, sexually-selected weapon affected the risk
of extinction under gradual temperature increase (20C per generation).
As temperature increased, individual survival decreased, but this effect
was much more dramatic in populations with high weapon prevalence,
compared to populations in which weapon expression was low.
Consequently, the former was significantly more prone to extinction than
the latter, with 75% vs 8% populations going extinct, respectively.
Extinctions occurred despite partial suppression of the weapon
expression at increased temperature, and were not explained by increased
male mortality. Our results provide the first, to our knowledge,
experimental evidence demonstrating dramatic effect of elaborated sexual
traits on the risk of extinction under environmental challenge.