Experimental niche evolution in seed beetles: Simulating responses to climate change in a currently evolving global crop pest
Lead Research Organisation:
University of Aberdeen
Department Name: Inst of Biological and Environmental Sci
Abstract
Climates are currently changing at an unprecedented rate, and many organisms are responding to these changes with dramatic range shifts involving evolutionary responses. Among the organisms most strongly affected by changing climates are small, exothermic animals such as insects, which can evolve rapidly and quickly disperse into available niches, often posing new threats to food security (as crop or stored-food pests), human and animal welfare (as disease vectors), and affecting overall ecosystem function.1
The mechanisms of evolution and range shift under rapidly changing climates remain poorly understood. One question relates to the order of trait divergence, which has important consequences for how biodiversity is affected by environmental change. In a model of a-niche priority for population divergence, organisms first evolve traits related to their within-community niche (i.e., the a-niche), such as alternative patterns of resource-utilization, species-interaction, and microhabitat use. New ways of interacting with their local habitat may then facilitate range expansion by providing new ways to overcome prior geographic limitations. Conversely, under b-niche priority, environmental change induces range shifts (i.e., adaptation to novel habitats and locales, the b-niche) prior to or in lieu of local, a-niche differentiation.2 These alternative scenarios each have important implications for how organisms respond to changing climates over the long term. b-priority implies limited scope for fine-scale local adaptation, which may limit the success of organisms that have nowhere suitable to go as climates change, while a-priority suggests that climate change may trigger successful invasions and adaptive radiations. Each of these scenarios has been found to occur in a variety of natural systems, but the general conditions favouring each evolutionary pathway are currently unknown.
In this PhD project, the student will investigate conditions under which these alternative niche evolution scenarios may occur, using experimental evolution under quasi-natural selection in a captive lab colony of seed beetles (Coleoptera: Bruchidae). Seed beetles are major pests on stored legumes and grains worldwide, and have been shown to evolve local host-plant shifts (habitat utilization, an a-niche component) and range shifts associated with evolving thermal tolerances (a b-niche component) in response to changing climates.3 Dynamic models developed by Jörgen Ripa (Lund University) suggest that the priority of a- vs. b-niche evolution depends on the relative strengths of evolutionary trade-offs imposed by habitat shifts vs. alternative resource use, and also by dispersal capacities. The student will conduct experimental evolution of replicate lineages in a two-habitat scenario with connectivity, where habitats are characterized by alternative thermal regimes. Within each habitat, individuals will also have the opportunity to adapt to new resources (i.e., new seed types). Rates of climate change within habitats, population densities, dispersal rates between habitats, and prior adaptations of initial lineages will be independently manipulated. Dynamic models of niche evolution pathways developed by Jörgen Ripa will inform experiments, and our experimental results will refine and parameterize future models. Controlled crossing experiments of resulting lineages will indicate the quantitative genetic basis of niche divergence along habitat and resource utilization axes, providing a mechanistic explanation for observed patterns. The project can also be further developed to incorporate genomic methods for understanding the mechanisms of niche evolution. The outputs of this project will further evolutionary theory, particularly in the area of niche evolution, and will inform pest management decisions.
The mechanisms of evolution and range shift under rapidly changing climates remain poorly understood. One question relates to the order of trait divergence, which has important consequences for how biodiversity is affected by environmental change. In a model of a-niche priority for population divergence, organisms first evolve traits related to their within-community niche (i.e., the a-niche), such as alternative patterns of resource-utilization, species-interaction, and microhabitat use. New ways of interacting with their local habitat may then facilitate range expansion by providing new ways to overcome prior geographic limitations. Conversely, under b-niche priority, environmental change induces range shifts (i.e., adaptation to novel habitats and locales, the b-niche) prior to or in lieu of local, a-niche differentiation.2 These alternative scenarios each have important implications for how organisms respond to changing climates over the long term. b-priority implies limited scope for fine-scale local adaptation, which may limit the success of organisms that have nowhere suitable to go as climates change, while a-priority suggests that climate change may trigger successful invasions and adaptive radiations. Each of these scenarios has been found to occur in a variety of natural systems, but the general conditions favouring each evolutionary pathway are currently unknown.
In this PhD project, the student will investigate conditions under which these alternative niche evolution scenarios may occur, using experimental evolution under quasi-natural selection in a captive lab colony of seed beetles (Coleoptera: Bruchidae). Seed beetles are major pests on stored legumes and grains worldwide, and have been shown to evolve local host-plant shifts (habitat utilization, an a-niche component) and range shifts associated with evolving thermal tolerances (a b-niche component) in response to changing climates.3 Dynamic models developed by Jörgen Ripa (Lund University) suggest that the priority of a- vs. b-niche evolution depends on the relative strengths of evolutionary trade-offs imposed by habitat shifts vs. alternative resource use, and also by dispersal capacities. The student will conduct experimental evolution of replicate lineages in a two-habitat scenario with connectivity, where habitats are characterized by alternative thermal regimes. Within each habitat, individuals will also have the opportunity to adapt to new resources (i.e., new seed types). Rates of climate change within habitats, population densities, dispersal rates between habitats, and prior adaptations of initial lineages will be independently manipulated. Dynamic models of niche evolution pathways developed by Jörgen Ripa will inform experiments, and our experimental results will refine and parameterize future models. Controlled crossing experiments of resulting lineages will indicate the quantitative genetic basis of niche divergence along habitat and resource utilization axes, providing a mechanistic explanation for observed patterns. The project can also be further developed to incorporate genomic methods for understanding the mechanisms of niche evolution. The outputs of this project will further evolutionary theory, particularly in the area of niche evolution, and will inform pest management decisions.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/M010996/1 | 01/10/2015 | 31/03/2024 | |||
| 1654640 | Studentship | BB/M010996/1 | 01/10/2015 | 30/09/2019 |
| Description | This award is still in progress. In response to climate change, many species are range shifting to take advantage of new colonisation opportunities in habitats located pole-wards of their ancestral range, where temperatures have recently warmed to surpass minimally-suitable conditions for population growth (Hoffman & Sgró, 2011). Currently we have found that adaptation to cooler and more variable temperatures as is typically seen during a range shift results in beneficial, evolved changes in both heat and cold tolerance in the ancestral environment but these improvements are reversed under different developmental and short-term acclimation scenarios resulting in patterns of maladaptive thermal tolerance plasticity which prevent the expression of the evolved benefit in the novel environment. I have been running a resource-selection experiment in the laboratory for the past 3 years using seed beetles, where beetles have a choice of settling on a new resource (new bean species) or their ancestral resource to lay their eggs (egg laying decision determines the offspring rearing environment, as larvae complete development inside beans). Because she never removes any beetles from the system (but maintains resources at a constant level), and reproduction rate is very high (individual females can lay up to 100 eggs), there should be strong competition-based selection to utilize the novel resource, even though they initially have much lower fitness on it (which we know from pilot studies). Preliminary results show that there seem to be strong asymmetrical maternal effects deterring the outcome of bean choice in the evolved lines. Essentially, for beetles emerging from the ancestral bean type, their choice of bean type is determined by what kind of bean their mother emerged from (a consequence of the grandmother's resource choice, or possibly an evolved effect of adapting to the new bean type combined with a maternal effect benefit of emerging on the old bean type- it is a bit ambiguous at the moment). However, for beetles emerging from the novel bean type, the grandmother's choice had no effect on their choice- it is entirely a maternal effect which seems to erase any signal of a grand-maternal effect, if it existed. |
| Exploitation Route | These results are novel and may be of interest to readers interested in ectotherm physiological responses to climate change, and adaptations during range shifts. In the context of global pest or disease species, this may have important implications for a time limit on our ability to control populations establishing in a novel environment. Rapid eradication may be critical, when maladaptive plasticity is still present and before the acquisition of beneficial developmental plasticity which may ultimately allow a range expansion to gain momentum. |
| Sectors | Agriculture, Food and Drink |
| Description | Hosting school children to the university to learn about invertebrates |
| Form Of Engagement Activity | Participation in an open day or visit at my research institution |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Schools |
| Results and Impact | Stimulating interest in school children about the importance of diverse insect communities More broadly encouraged families to be interested and discuss science at home by sparking questions and discussions with us and amongst themselves. |
| Year(s) Of Engagement Activity | 2017 |