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Temperature variation and mating behavior in treehoppers

Global warming poses unknown challenges to the abilities of animals to attract and find suitable mates. A wide range of reproductive traits involved in sexual communication are thermally sensitive; yet, the consequences of global warming for sexual communication and other reproductive processes have been almost entirely ignored.

Warming is likely to pose two major challenges to sexually signaling ectotherms. First, mating often occurs within a particular range of temperatures; thus, changes in thermal conditions could narrow the amount of time that temperatures fall within the reproductive window, ultimately reducing mating rates. Second, the signals that males use to attract females, and the signals that females prefer, are often sensitive to thermal conditions. When temperatures change (e.g. following global warming), males may alter the signals they produce or females may alter the signals they prefer, leading to a signal-preference mismatch (i.e. a breakdown in sexual communication).

In this study, we use Enchenopa binotata treehoppers--captured across a latitudinal gradient--to better understand the plasticity of male signals and female preferences in response to temperature changes, as well as their potential consequences for reproduction.


Watch this video to discover how treehoppers converse through vibrations and touch.

Original event info: Thursday, July 20, Cliff Cave Branch of the St. Louis Library


Treehopper Communication

Enchenopa binotata treehoppers are small (~1/2 cm), plant-feeding insects that communicate using acoustic vibrations. Male treehoppers make vibrations on the stems, petioles, and leaves of their host plants that travel throughout the plant. Vibrational signaling is the most ubiquitous form of acoustic communication in the animal kingdom (more than 90% of insects use substrate-borne vibrations to communicate within and between species).

Explore the sounds of Treehopper vibrations

 
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SEXUAL SIGNALLING

To find mates, male treehoppers fly from plant to plant, searching for females and producing species-specific advertisement signals when they land. Females detect these signals with mechanosensors on their legs and, if they find the male’s signal attractive, they initiate a male-female vibrational duet that leads to mating.


Male signals and Female signal preferences are sensitive to thermal conditions

Listen to differences in both male signals and female responses at different temperatures

 
 
 To study vibrational signals, our lab uses a specialized laser recording device to capture the sounds of insect movement on the stems and leaves of plants. Photo:  Impact Media Lab

To study vibrational signals, our lab uses a specialized laser recording device to capture the sounds of insect movement on the stems and leaves of plants. Photo: Impact Media Lab

 
 

Preliminary Data

This study uncovers new consequences of climate change that can impact mating success and, ultimately, survival in vibrationally signalling animals (i.e. more than 90% of insects). Here we combine our temperature trials with studies that measure genetic-based variance in the temperature sensitivity of treehoppers, for an unparalleled look at reproductive behavior in the face of climate change.

Learn more about our expectations and early findings below

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Female mate preference functions

Female mate preference functions describe female response to male signals along continuous variation in signal frequency. This graph of preliminary data includes raw data (dots) and the extracted spline. The red arrow points to the frequency for female peak preference. This project focuses on “peak preference,” but other aspects of the function, like selectivity, can be extracted.

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Thermal performance curves

Reproductive thermal performance curves describe likelihood of males signaling or females responding as a function of temperature. The quadratic shape can be described in terms of: Performance breadth, the temperature range at which 90% of individuals signal/respond; thermal tolerance, the range at which >10% of individuals signal/respond; thermal optimum (Topt), the temperature that maximizes signals/responses.

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Thermal reaction norms

Thermal reaction norms describe male signal frequency or female peak preference as a function of temperature. Thermal reaction norms are linear with a positive slope. In this graph of preliminary data, the red line represents males, the black line females (Jocson and Fowler-Finn, unpublished).


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