Male secondary sexual traits do not predict female preference in Caribbean livebearing fishes (Limia)

Female preference is widely described in various taxa, and the underlying
mechanisms shaping preferences remain a major focus of sexual selection
studies, particularly in species where males contribute minimally to
offspring. Female preference is associated with maintaining male secondary
sexual traits (SST). However, how male SST impact female preference is
less understood. We hypothesized the strength of female preference should
scale with the expression of male SST. To test this prediction, we
compared female preference for male body size (an easily quantifiable
trait that scales with other SST) in three species of Limia (Poeciliidae)
varying in secondary sexual traits: L. perugiae, L. dominicensis, and L.
zonata. The degree of SST was assessed based on the amount of
ornamentation and the presence of courtship in the species. Limia
perugiae, L. dominicensis, and L. zonata were designated as possessing
high, intermediate, and low male SST, respectively. Female preference was
quantified as the relative amount of time females associated with males of
various size classes: small, intermediate, and large. Therefore, we
predicted because L. perugiae males have the most SST, females would
associate more strongly with large males. Limia perugiae females were the
only species to display female preference in relation to male body size,
but they preferred small males. Although preference was observed, the
direction of preference was unexpected. Moreover, the lack of preference
for large male size and thereby other SST in the species suggests
pre-copulatory female preference is unimpacted by male SST. We suggest
cryptic female choice (i.e., preference enacted during or after
copulation) may maintain costly male traits. However, future work remains
necessary. The present study provides foundational behavioural work on
Limia and examines the ubiquity of the evolution of female preference in
poeciliids.