The evolutionary responses of cuticular hydrocarbon production and compensatory feeding behaviours when crickets have evolved in different nutritional environments

Abstract

Condition dependent traits are reliant upon the acquisition and allocation of resources, with studies theorising that those individuals able to acquire more resources are then able to allocate more resources to these sensitive traits. These traits are often related to sexual reproduction, one of the most important aspect of an organism's life cycle. One such trait is chemical signalling, where the production of these chemicals is known to be linked to adequate, over- or under-consumption. However, relatively little is known on compensatory feeding behaviours and dietary adaptation to offset the nutritional value of resources. This includes either consuming more or less depending on the overall quality of the food sourced. Furthermore, little research has been conducted into how populations respond to diet over multiple generations, analysing whether feeding behaviours has the potential to evolve in response to different dietary environments. Thus, little is also known about whether potentially evolved dietary responses have an effect on condition-dependent traits. Here, nutritional geometry was used to determine the effect of protein and carbohydrate ratios and overall nutrition on compensatory feeding behaviours and cuticular hydrocarbon (CHC) production in the decorated cricket (Gryllodes sigillatus), studying the effect of different ratios on multiple generations. A common garden experiment was employed for to determine whether responses were genetic rather than phenotypic in nature. Populations of crickets were raised on either low or high nutritional diets, which were also either protein or carbohydrate biased. A population was also kept on a standard balanced diet (SCD) for comparison. For study into possible genetic dietary responses, some populations raised on the altered diets were switched back to the standard diet (SCD). Individuals maximised consumption when faced with low nutritional value diets, while those raised on high nutritional value diets consumed less. Individuals switched back to SCD consumed an amount similar to their ancestral diet, however still maintained a noticeable difference in consumption, suggesting an evolution of genetics behind compensatory feeding behaviour as well as the typical phenotypic response. This adaptation to differing diets has a direct influence on CHC production, impacting the overall amount and blend of short and long chain CHCs across and within all diet treatments. CHC composition was sex-specific, however, diet altered the overall production. Switched diet individuals showed evolved feeding behaviour, consequently affecting CHC production in line with altered macronutrient and caloric intake. CHC compositions indicated that while individuals changed from a protein or carbohydrate-biased diet to a more balanced diet, there is the possibility of a genetic tendency to produce CHC blends similar to their ancestors. Theoretically, this has a consequential effect on male fitness, as females are attracted to specific male CHC blends.

Date of Award	2020
Original language	English