Effect of multiple selective factors in vocal evolution

TUBARO, PABLO L.; GARCÍA, NATALIA C.; KOPUCHIAN, CECILIA; PODOS, JEFFREY; ARRIETA, RAMIRO S.

Vancouver

Congreso; 27th International Ornithological Congress; 2018

Characters can be subject to multiple and sometimes opposing selective forces. The trilled songs of many songbird species show a negative correlation between note rates and frequency bandwidth due to a motor constraint. The deviation from an upper-bound regression of these variables can provide a good estimator of ?vocal performance?. Yet, trilled songs can also be adapted to limit sound degradation through divergence in note rates in open or closed habitats. We studied the potential interaction of these two selective forces in a population of Rufous-collared sparrows using recordings from 2010/2011 We had previously found that trills of Rufous-collared sparrows from closed habitats have lower note rates, consistent with an acoustic adaptation hypothesis. Here, we show that trilled songs from both habitats express a significant negative upper-bound regression of frequency bandwidth on trill rate, implying that this species´ trills are performance-limited. Closed-habitat trills also have higher frequency bandwidth, perhaps in compensation for diminished note rates. In fact, vocal deviation is significantly lower in closed habitats than in open habitats. We propose that the effect of habitat type as a selective force is stronger than is selection for high performance songs, and/or that the constraints on minimum/maximum frequency production limits individuals from open habitats in their overall vocal performance, as compared to birds from closed habitats.