Weak warning signals can persist in the absence of gene flow
|Author(s)||Lawrence J. P.1, 6, Rojas Bibiana2, Fouquet Antoine3, Mappes Johanna2, Blanchette Annelise4, Saporito Ralph A.4, Bosque Renan Janke1, Courtois Elodie A.5, Noonan Brice P.1|
|Affiliation(s)||1 : Univ Mississippi, Dept Biol, University, MS 38677 USA.
2 : Univ Jyvaskyla, Dept Biol & Environm Sci, Jyvaskyla 40014, Finland.
3 : CNRS, Lab Evolut & Divers Biol, UMR5174, F-31062 Toulouse 9, France.
4 : John Carroll Univ, Dept Biol, University Hts, OH 44118 USA.
5 : Univ Guyane, Ctr Rech Montabo, Lab Ecol Evolut Interact Syst Amazoniens, BP 70620, F-97334 Cayenne, France.
6 : Univ Calif Irvine, Dept Ecol & Evolutionary Biol, Irvine, CA 92697 USA.
|Source||Proceedings Of The National Academy Of Sciences Of The United States Of America (0027-8424) (Natl Acad Sciences), 2019-09 , Vol. 116 , N. 38 , P. 19037-19045|
|WOS© Times Cited||26|
|Keyword(s)||aposematism, frequency-dependent selection, polymorphism, unpalatability, secondary defenses|
Aposematic organisms couple conspicuous warning signals with a secondary defense to deter predators from attacking. Novel signals of aposematic prey are expected to be selected against due to positive frequency-dependent selection. How, then, can novel phenotypes persist after they arise, and why do so many aposematic species exhibit intrapopulation signal variability? Using a polytypic poison frog (Dendrobates tinctorius), we explored the forces of selection on variable aposematic signals using 2 phenotypically distinct (white, yellow) populations. Contrary to expectations, local phenotype was not always better protected compared to novel phenotypes in either population; in the white population, the novel phenotype evoked greater avoidance in natural predators. Despite having a lower quantity of alkaloids, the skin extracts from yellow frogs provoked higher aversive reactions by birds than white frogs in the laboratory, although both populations differed from controls. Similarly, predators learned to avoid the yellow signal faster than the white signal, and generalized their learned avoidance of yellow but not white. We propose that signals that are easily learned and broadly generalized can protect rare, novel signals, and weak warning signals (i.e., signals with poor efficacy and/or poor defense) can persist when gene flow among populations, as in this case, is limited. This provides a mechanism for the persistence of intrapopulation aposematic variation, a likely precursor to polytypism and driver of speciation.