Meeting Abstract
A number of genetic, development, and selection factors can contribute to the evolution of convergent traits. So often, we focus on selection pressures as the driver of convergence; however, many anuran (frog and toad) species have independently evolved earlessness, the lack of a tympanic middle ear, despite limited evidence that shared selection pressures contribute to these independent middle ear losses. The tympanic middle ear normally transmits airborne sound from the environment to their inner ear sensory cells, making the middle ear’s loss puzzling given the importance of acoustic communication in most anuran mating systems. Here we investigate the genomic changes, developmental biases, and potential selection pressures affecting the lability of middle ear structures in the true toad family (Bufonidae). We characterized genomic changes across independent evolutionary transitions of ears to identify shared mutations and selection pressures on genes that pattern the middle ears. The minor differences between eared and earless skulls indicate that the middle ear is lost without change to other developmentally or genetically linked skull features. We have also shown that the middle ear forms very late in the development of toads despite high frequency sensory costs. I interpret these results in light of known natural history data for earless toad species and discuss interactions between selection and developmental processes in shaping the evolutionary lability of ear structures.
