Predicting ectotherm life cycles under a variable climate: physiological diversity of matchstick grasshopper eggs and their ecological and evolutionary implications
AuthorKong, Jacinta Dara
AffiliationSchool of BioSciences
Document TypePhD thesis
Access StatusThis item is embargoed and will be available on 2021-07-15. This item is currently available to University of Melbourne staff and students only, login required.
© 2019 Dr. Jacinta Dara Kong
Understanding the processes underlying the phenology and distribution of species is a key problem in ecology. These relationships are important for predicting the responses to species to environmental change. Phenology and distribution are closely linked to climate and weather through the thermal dependence of life cycles. However, for many biodiverse taxa, like insects, we have a poor understanding of the mechanistic links between adaptive traits and how life cycles are adapted to seasonal and variable temperature patterns. Insect life cycles are synchronised with suitable climatic conditions at critical life stages, such as the egg stage. Variation in thermal sensitivity of development and dormancy are two mechanisms by which insects can generate adaptive life cycle phenotypes. Eggs, therefore, present a unique opportunity to link adaptive variation in traits with corresponding variation in life cycles and thermal environments to examine how life cycles are adapted to variable climates. To understand the adaptation of insect life cycles to variable climates, we require a mechanistic understanding of the interactions between adaptive developmental traits of eggs and variation in the thermal environment on adaptations. Our ability to test thermal adaptation in ectotherms is also limited by our ability to efficiently characterise thermal responses. In this thesis, I described how thermocyclers are an efficient means of characterising the thermal response of small ectotherms with enough precision and sample size. I then used the widely distributed, endemic and flightless Australian matchstick grasshopper genera Warramaba (Orthoptera: Morabidae) as a model system to examine the significance of variation in thermal responses at the egg stage for life cycles under a variable climate. I used a mechanistic modelling framework to tease apart developmental and environmental sources of variation in life cycles at the egg stage and simulate their consequences for phenology and distribution in the field. Matchstick grasshoppers showed remarkable diversity in developmental responses to temperature at the egg stage, primarily in the expression of dormancy. I found that diverse Warramaba life cycles are shaped by the interactions between such developmental variation and local environmental temperatures. I demonstrated that we can achieve a mechanistic understanding of life cycle adaptation by considering the evolution of temperature-dependent traits and the evolution of life history within the context of seasonal temperature cycles. Mechanistic models are powerful tools to investigate the sources of life cycle variation and their consequences for insect distribution and phenology. Such frameworks are directly transferrable to other socio-economically important or threatened species to understand how insects are adapted to local climatic conditions and predict responses to a changing climate.
Keywordszoology; ecophysiology; ecology; evolutionary biology
- Click on "Export Reference in RIS Format" and choose "open with... Endnote".
- Click on "Export Reference in RIS Format". Login to Refworks, go to References => Import References