Host-parasite evolutionary ecology
Research in the group concerns the causes and consequences of genotypic and phenotypic diversity, with a focus on these issues in relation to the Evolution and Ecology of Host-Microbe Interactions, Ecological Immunology, Life History Investment and Pollinator Health. Principally, studies use bumblebee-parasite systems and decorated crickets to answer questions in these areas. We combine fieldwork, lab experiments, experimental infections, experimental evolution, and genetic, genomic, and transcriptomic approaches.
Although, interlinked, current research can be broken into the following main categories:
- Importance of local or global heterogeneity for immunity/infection
- Evolutionary ecology of trans-generational immunity
- Evolutionary and ecological perspective of gut microbiota as mediators of health
- Reproductive investment and immunity in the face of variable infection threats
- Threats to native pollinator health as a result of global change
Importance of local or global ecological heterogeneity for immunity/infection outcomes
The world we live in is a very changeable one, with environments varying over both space and time. How specific host-parasite interactions are influenced by this variation will have important consequences for understanding diversity, host-parasite dynamics, and a number of linked phenomena.
~We ask how host and parasite genotypes and local variation in the ecology of individual hosts (conspecific interactions, nutrition, parasite experience, pesticides) influences investment into immunity, infection outcomes, and ultimately evolutionary fitness.~
~On a broader scale, we ask how ecological variation across a host’s range, and host community composition impact the investment into and evolution of host defences against disease and the evolution of key parasite traits, such as virulence.~
Selected publications
McCormick, EC, Cohen, OR, Dolezal, AG, & Sadd, BM (2023) Consequences of microsporidian prior exposure for virus infection outcomes and bumble bee host health. Oecologia, 202, 325-335 pdf
Fowler, AE, Sadd, BM, Bassingthwaite, T, Irwin, RE & Adler, LS (2022) Consuming sunflower pollen reduced pathogen infection but did not alter measures of immunity in bumble bees. Philosophical Transactions of the Royal Society B: Biological Sciences, 377, 20210160 pdf
Tobin, KB, Calhoun, AC, Hallahan, MF, Martinez, A & Sadd, BM (2019) Infection outcomes are robust to thermal variability in a bumble bee host-parasite system. Integrative and Comparative Biology, 59, 1103-1113 pdf
Palmer-Young, EC, Calhoun, A, Mirzayeva, A & Sadd, BM (2018) Effects of the floral phytochemical eugenol on parasite evolution and bumble bee infection and preference. Scientific Reports, 8, 2074 pdf
Barribeau, SM, Sadd, BM, du Plessis, L & Schmid-Hempel, P (2014) Gene expression differences underlying genotype-by-genotype specificity in a host-parasite system. Proceedings of the National Academy of Sciences USA, 111, 3496-3501 pdf
Sadd BM & Barribeau SM (2013) Heterogeneity in infection outcome: lessons from a bumblebee-trypanosome system. Parasite Immunology, 35, 339-349 pdf
Evolutionary ecology of trans-generational immunity
Nested within the above section, there is a focus on insect trans-generational immunity. Under certain ecological conditions, there will be a benefit for mothers to adjust levels of offspring immunity contingent on their own parasite experience. This is seen for bumble bee antibacterial immunity.
~We are looking closer at the mechanisms underlying this phenomenon in insects, and carrying out further experiments to place the costs and benefits of trans-generational immunity into an evolutionary ecology framework.~
Selected publications
Roth, O, Beemelmanns, A, Barribeau, SM & Sadd, BM (2018) Recent advances in vertebrate and invertebrate trans-generational immunity in the light of ecology and evolution. Heredity, 121, 225-238 pdf
Barribeau, SM, Schmid-Hempel, P & Sadd, BM (2016) Royal decree: gene expression in trans-generationally immune primed bumblebee workers mimics a primary immune response. PLoS ONE, 11, e0159635 pdf
Sadd BM & Schmid-Hempel P (2009) A distinct infection cost associated with trans-generational priming of antibacterial immunity in bumblebees. Biology Letters, 5, 798-801 pdf
Evolutionary and ecological perspective of gut microbiota as mediators of health
It is increasingly apparent that microbial communities living on and within many organisms can have a profound impact on their health and evolutionary fitness. This includes interactions with the immune system and the determination of parasite infection outcomes.
~We are investigating the specificity of these relationships, and how the immune system plays a role in mediating these critical relationships.~
Selected publications
*Li, J, *Sauers, L, *Zhuang, D, Ren, H, Guo, J, Wang, L, Zhuang, M, Guo, Y, Zhang, Z, Wu, J, Yao, J, Yang, H, Huang, J, Wang, C, Lin, Q, Zhang, Z & Sadd, BM (2023) Divergence and convergence of gut microbiomes of wild insect pollinators. mBio. (*Joint first authors) pdf
Sauers, LA and Sadd, BM (2019) An interaction between host and microbe genotypes determines colonization success of a key bumble bee gut microbiota member. Evolution, 73, 2333-2342 pdf
Wang, L, Wu, J, Li, K, Sadd, BM, Guo, Y, Zhuang, DH, Chen, YP, Evans, J, Guo, J, Zhang, Z & Li, J (2019) Dynamic changes of gut microbial communities of bumble bee queens through important life stages. mSystems, 4, e00631-19 pdf
Reproductive investment and immunity in the face of variable infection threats
There is a strong connection between infection and life history investment, such that infection status may lead to plastic adjustment of life history strategies, particularly reproduction. On top of this, further biotic and abiotic cues may modulate any changes in investment to reproduction and immunity.
~We are investigating how life history strategies are influenced by interactions between infection, current status of an organism, and the external environment.~
Selected publications
Hampton, KJ, Duffield, KR, Hunt, J, Sakaluk, SK & Sadd, BM (2021) Male and female genotype and a genotype-by-genotype interaction mediate the effects of mating on cellular but not humoral immunity in female decorated crickets. Heredity, 126, 477-490 pdf
Duffield, KR, Hampton, KJ, Houslay, TM, Hunt, J, Sadd, BM & Sakaluk, SK (2019) Inbreeding alters context-dependent reproductive effort and immunity in male crickets. Journal of Evolutionary Biology, 32, 731-741 pdf
Duffield,KR, Hampton, KJ, Houslay,TM,Hunt, J, Rapkin, J, Sakaluk, SK & Sadd, BM (2018) Age-dependent variation in the terminal investment threshold in male crickets. Evolution, 72, 578-589 pdf
Duffield, KR, Bowers, EK, Sakaluk, S & Sadd, BM (2017) A dynamic threshold model for terminal investment. Behavioral Ecology and Sociobiology, 71, 185 pdf
Threats to native pollinator health as a result of global change
Native pollinators are crucial in many natural and agricultural ecosystems. However, many native pollinators have been undergoing worrying declines, and are faced with continuing threats as a result of global change. This is an important applied aspect of our work on native bumble bees under the research topics above.
~We are working to gaining a better understanding of the determinants of bumble bee pollinator health and the threats to it, particularly including pathogens, pesticides, and climate change.~
Selected publications
Rubén Martín-Blázquez, R, Calhoun,AC, Sadd,BM, & Cameron, SA (2023) Gene expression in bumble bee larvae differs qualitatively between high and low concentration imidacloprid exposure levels. Scientific Reports, 13, 9415 pdf
*Figueroa, LL, *Sadd, BM, *Tripodi, AD,Strange, JP, Colla, SR, Adams, LD, Duennes, MA, Evans, EC, Lehmann, DM, Moylett, H, Richardson, L, Smith, JW, Smith, TA, Spevak, EM & Inouye, DW(2023) Endosymbionts that threaten commercially raised and wild bumble bees (Bombus spp.). Journal of Pollination Ecology, 32, 14-36. (*Joint first authors) pdf
Calhoun, AC, Harrod, AE, Bassingthwaite, TA & Sadd, BM (2021) Testing the multiple stressor hypothesis: Chlorothalonil exposure alters transmission potential of a bumblebee pathogen but not individual host health. Proceedings of the Royal Society B: Biological Sciences, 288, 20202922 pdf
Cameron, SA & Sadd, BM (2020) Global trends in bumble bee health. Annual Review of Entomology, 65, 209-232 pdf
Czerwinski, MA & Sadd, BM (2017) Detrimental interactions of neonicotinoid pesticide exposure and bumblebee immunity. Journal of Experimental Zoology A, 327, 273-283 pdf
Fauser, A, Sandrock, C, Neumann, P & Sadd, BM (2017) Neonicotinoids override a parasite exposure impact on hibernation success of a key bumblebee pollinator. Ecological Entomology, 42, 306-314 pdf
