UC Merced

This thesis first examines the influence of population dynamics on the evolution of acoustic signals. Acoustic signaling is employed by many sexually reproducing species to select for mates and enhance fitness. However, signaling in dense populations can create an auditory background, or chorus, which can interfere with a signal receiver’s phonotactic selectivity, or the ability to distinguish signals. Feedback between the strength of an individual’s signal, phonotactic selectivity, and population size, may interact in complex ways to impact the evolution of the signaling trait within a population, potentially leading to the emergence of silence. Here I formulate a general model that captures the dynamic feedback between individual acoustic signalers, phonotactic selectivity, and the population-level chorus to explore the eco-evolutionary dynamics of an acoustic trait. I find that population dynamics has a significant influence on the evolutionary dynamics of the signaling trait, and that very sharp transitions separate conspicuous from silent populations. My frameworkalso reveals that increased phonotactic selectivity promotes the stability of signaling populations. I suggest that understanding the relationship between factors influencing population size such as environmental productivity, as well as factors influencing phonotactic selectivity such as anthropogenic noise, are central to understanding the complex mosaic of acoustically signaling and silent populations.

Then this thesis focuses on the effect of parasitoids on the evolution of the acoustic signal Acoustic signals used by organisms to attract mates are known to attract parasitoid flies. The parasitoid flies lay their eggs inside the host signaler, eventually killing the host. I build a host-parasitoid acoustic model to investigate the effect of parasitoid flies on the signalling host’s eco-evolutionary dynamics. I used field crickets as a system to build the framework of the model. I explore how the sex ratio and the female parasitoid fecundity impact the evolution of the acoustic signal and populationdensity of the signalling hosts. I also explore the stability of the host populations with an increase in parasitoid load. I find that up to a threshold value, an increase in parasitoid load leads to a thriving yet silent host population. Consistent with field observations, my results show how this emergence of silence as an evolutionary strategy is immediate. My results show that a drastic increase in the parasitoid load can rapidly push the signalling host population towards instability and extinction.

Finally, this thesis focuses on the differential impact of anthropogenic noise across taxa. Anthropogenic noise is one of the major pollutants on earth. Growing research has shed light on the impact of anthropogenic noise from the individual level to the community level. Although, most of these studies are either done on particular species, or on exclusive communities. We lack an understanding of which class or phylum is most affected and how they are affected by noise pollution. In this study, I explain how and why invertebrates are more likely to be affected by anthropogenic noise. I review their signal production mechanisms, how species are impacted on both physiological and ecological scales, and their response to both natural and anthropogenic noise sources. Further, I qualitatively compare the anthropogenic noises, and the extent towhich different taxa are impacted in various ways. I show that anthropogenic noise has vast and direct impacts on the fitness of invertebrates which may have evolutionary consequences. I suggest that the findings of this review would be helpful in prioritizing conservation efforts linked to noise pollution.