Evolve quickly...
or perish. A study published in a recent issue of the journal American Naturalist has found that guppies (Poecilia reticulata) are capable of evolving new and advantageous traits in the space of a few years.
Researchers led by Swanne Gordon studied 200 guppies originally from the Yarra River in Trinidad and introduced to the nearby Damier River, which was historically free of guppies.
The fishes were originally introduced upstream of a waterfall barrier, a habitat that was predator-free, but the guppies then spread downstream of the waterfall, a habitat that contained three species of sleeper gobies that were potential predators of the guppies.
Eight years after the introduction (corresponding to about 13"26 guppy generations), the researchers resampled the Damier River upstream and downstream of the waterfall barrier for guppies.
They found that in the high-predator, downstream environment, the females had evolved to produce more embryos per reproductive cycle.
This strategy makes sense in the face of high predation pressure, given that the chances of a female successfully reproducing before being eaten are considerably smaller.
The authors then transplanted more guppies from the Yarra River into the Damier River, and compared the survival rates of the newly transplanted fish against the established population.
They found that there were no significant differences in the survival rates of the adults between the newly transplanted and established populations, but that juveniles of the established population had an increase of 54"59% in their survival rate compared to the newly transplanted fish.
For more information, see the paper: Gordon, SP, DN Reznick, MT Kinnison, MJ Bryant, DJ Weese, K Rsnen, NP Millar and AP Hendry (2009) Adaptive changes in life history and survival following a new guppy introduction. American Naturalist 174, pp. 34"45.