Presentation Detail

Experimental Evolution

Bono, Lisa M. [1], Gensel, Catharine L. [2], Pfennig, David [3], Burch, Christina L. [4].

Alternative host-use morphs coexist only when trade-offs emerge in experimentally evolved viruses.

Competition for resources has long been considered a key driver of adaptive diversification. Previously, we confirmed that competition among bacteriophage for bacterial hosts (a vital resource) triggered the evolution of novel host use phenotypes (generalists). However, these new generalists tended to competitively exclude the ancestral host specialist, and coexistence between the two forms was therefore rare. We further found that the generalists did not face any fitness trade-offs on different hosts, which theory posits are necessary for coexistence. Here, we show that, under ecological conditions that slow the evolutionary dynamics, coexistence occurs following the emergence of a trade-off. We conducted bacteriophage evolution experiments that were exactly analogous to our previous experiments except that we reduced the relative abundance of novel hosts in our experimental microcosms. The resulting slower evolutionary dynamics allowed the emergence of trade-offs from a variety of mechanisms. In some cases, antagonistic pleiotropy arose when the generalist̢۪s fitness on one host directly imposed a cost on its fitness of the other host. In other cases, generalists paid an indirect fitness cost when the specialist further adapted to the standard resource but the generalist did not. Although we found strong evidence that competition promotes the origin of diversity through the evolution of novel phenotypes, we confirmed that competition only maintains that diversity when fitness trade-offs emerge and that these trade-offs can stem from multiple causes.

1 - University of North Carolina, Chapel Hill, Biology, Department of Biology, CB#3280, Chapel Hill, NC, 27599
2 - North Carolina State University, Food Science, Raleigh, NC, 27 695, USA
3 - University of North Carolina, Biology, Coker Hall, CB#3280, Chapel Hill, NC, 27599-3280, USA
4 - University of North Carolina, Chapel Hill, Biology, Department of Biology, CB#3280, NC, 27599, USA

Keywords:
Competition
Experimental Evolution
virus
generalists.

Presentation Type: Regular Oral Presentation
Session: 80
Location: Rendezvous B/Snowbird Center
Date: Sunday, June 23rd, 2013
Time: 1:45 PM
Number: 80002
Abstract ID:945
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation,Student Travel Awards from the ASN