Why mollies? This
is the question I most often hear regarding my master’s thesis research. To be honest, I find myself wondering that
same question when I’m submerged up to my shoulders in stinky fish water
scrubbing the walls of their 150-gallon tanks.
Why do I do this? Well, sailfin
mollies (Poecilia latipinna) are an
excellent example of a species subject to strong sexual selection. Just like the male peacock with his
outrageous tail feathers, male mollies have developed an enormous dorsal fin that
serves to attract females. How do such traits
evolve? One hypothesis – the handicap
principle – suggests that because these enlarged traits are a burden to have,
they must signal high mate quality to interested females. So the debate is over – bigger is better, at
least in the animal kingdom! But wait –
what’s a small male to do? Well, smaller,
less preferred male mollies have adopted an alternative mating strategy in
which they try to sneak mating attempts on unsuspecting females. While not so nice, these strategies are
equally successful as the courtship strategy employed by large males (see
courtship video below), so both strategies, sneaking and courting, are maintained
in wild molly populations. Pretty cool
if you ask me.
male courtship display
hey girl, do you like my tail feathers?
large male (50mm)
small male (25mm)
