Collaborative Research: The genetic basis of call diversity in acoustic insects

Murray State University, Murray KY

Investigators

Abstract

The behavior of animals plays an important role in biological diversity. For example, many insects have specific calls which are barriers to mating between species. This diversity is in large part under the control of genes. Patterns of gene expression and regulation during development can also result in specific behaviors. However, it is unclear how differences in behavior relate to genetic differences: what is the contribution of changes in the actual genes relative to that of changes in gene regulation? This remains a fundamental open question of general importance, far beyond the diverse calls of insects. In this research this question is addressed in a katydid species that produces two alternative calls in response to the environment experienced during development. The differences between these calls within a population are due to differences in gene regulation. Population-level differences also occur across the geographic range of this insect, and this variation is largely caused by differences in individual's genes. This allows the assessment of the contributions of both genes and genetic regulation to the diversity of behavior in this species. This project integrates genetics, neurobiology, behavior, and evolution. Its outcomes contribute to the understanding of the genetic foundation of biodiversity and are relevant in many areas outside of animal behavior, including medical research. Broader impacts include training opportunities for students of diverse backgrounds that prepare them for the challenges of careers in life sciences. Outreach activities introduce the public to modern biology research in a relatable study system. The goal of this project is to understand the genetic underpinnings of the call diversity in Neoconocephalus katydids. The species Neoconocephalus triops undergoes developmental plasticity (DP) that results in two alternative advertisement calls with species-level differences in two temporal properties (pulse rate and verse pattern). DP can be induced reliably by varying the photoperiod before sexual maturation. First, the relevant developmental stages and tissues (central pattern generators, CPG) in the CNS that contribute to the call pattern generation will be identified. Aim 1 identifies the location of the CPGs using lesion experiments, calcium imaging, and selectively heating of individual ganglia. In aim 2, the investigators identify the sensitive phase of phenotype induction by varying the exposure time of short day conditions and analyzing adult call phenotypes. Aim 3 explores the genetic underpinnings of the diversity of call patterns. RNAseq will be conducted using tissues containing the CPGs collected at the relevant times identified in aim 2. Correlations between phenotypes and differences in gene expression patterns as well as genetic differences among populations will be identified. Comparisons include two call phenotypes of three populations that differ significantly in call pattern and extent of DP. In aim 4, the investigators will manipulate the expression levels of candidate genes identified in aim 3, using RNAi and examine the consequences for call phenotypes, moving from identifying correlations to testing causation. The outcomes provide testable hypotheses about the genetic control of call variation, which plays a significant role in the diversification of this group. Training and outreach activities are focusing on the public and students of rural areas in MO, KY, and WV, which are traditionally underserved groups. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.