Publications
01
Evidence consistent with local adaptation to predation shaping stabilizing effects underlying local coexistence.
Ecosphere
Gómez-Llano et al. (2026)
Technical Summary:
We conducted experiments with larval and adult damselflies in the southeastern United States to understand if fish predators affected the ability of damselfly species to coexist in the same habitat.
Lay Summary:
We conducted experiments with damselflies in the southeastern United States to understand how fish predators affected the ability of multiple damselfly species to live in the same place.
02
The macroecology of immunity: predominant influence of climate on invertebrate immune response.
Ecography
Hasik et al. (2026)
Technical Summary:
We studied how temperature and precipitation affected immune defenses in dragonflies and damselflies from southeastern Canada. We found that immune defenses were most strongly related to precipitation, suggesting that immune defenses in these insects are the biproduct of adaptation to drier habitats.
Lay Summary:
We studied dragonflies and damselflies from southeastern Canada to understand how they defend themselves against parasites with their immune systems and how where they live might also affect that. We found that average rainfall predicted how good their immune systems were at fighting off parasites.
03
Parasite-mediated inbreeding depression: evidence from a wild population of red deer.
Heredity
Hasik et al. (2025)
Technical Summary:
In the Inner Hebrides of Scotland, we related a measure of inbreeding to multiple measures of fitness and parasite load. We found that more inbred deer had increased parasitism and that having more parasites and a greater inbreeding value decreased overwinter survival.
Lay Summary:
In the Inner Hebrides of Scotland, we studied if more inbred red deer had more parasites, and what that meant for their survival. We found that more inbred calves had more parasites, and being more inbred and having more parasites both increased the chances that the deer died over the winter.
04
Population density drives increased parasitism via greater exposure and reduced resource availability in wild hosts.
Parasitology
Hasik et al. (2025)
Technical Summary:
In the Inner Hebrides of Scotland, we related individual level population density of red deer to parasite load and immune defenses. We found that deer living at high density had both increased parasite loads and reduced immune defenses.
Lay Summary:
In the Inner Hebrides of Scotland, we studied the relationship between red deer population numbers and infection by parasites, finding that red deer living near a lot of other red deer were both more exposed to parasites and had weaker immune systems.
05
Parasitism as a driver of host diversification.
Nature Reviews Biodiversity
Hasik et al. (2025)
Technical Summary:
We proposed a novel framework using phylogenetic models to understand if the effects of parasites at the microevolutionary scale drive host macroevolutionary dynamics.
Lay Summary:
We designed a way to test if the immediate effects of parasites can have long-term consequences for the evolution of their hosts.
06
Parasite contingency loci and the evolution of host specificity: Bartonella krasnovii adaptation to a rodent host is dominated by mutations in simple-sequence repeats in an adhesin gene
PLoS Pathogens
Rodríguez‑Pastor et al. (2024)
Technical Summary:
We conducted an evolutionary experiment to understand how bacterial parasites adapt to their rodent hosts (sourced from southern Israel). We found that the bacteria have a highly variable section of their genetic code that allows them to quickly adapt to and overcome host immune defenses.
Lay Summary:
We created an experiment that tests how bacteria evolved in response to gerbils’ immune systems. We found that the bacteria are very adaptable and are better able to avoid the gerbils’ immune systems shortly after infecting them.
07
Is the local environment more important than within-host interactions in determining coinfection?
Journal of Animal Ecology
Hasik et al. (2024)
Technical Summary:
We studied how coinfection by ecto- and endoparasites varies across ecological gradients using damselflies in the southeastern United States. We found that the local environment is the best predictor of variation in infection by the two parasites, with no evidence for within-host interactions between the two parasites.
Lay Summary:
Using damselflies in the southeastern United States, we studied how infection by two different parasites can change due to environmental characteristics such as predators, competition from other damselflies, water quality, and other things going on in the ponds that they live in. We found that these environmental characteristics affected each individual parasite, but the two parasites did not affect one another.
08
Age-related changes in parasite infection occur independently of behavioural ageing in a wild ungulate.
Philosophical Transactions of the Royal Society B
Albery et al. (2024)
Technical Summary:
We investigated if infection patterns in red deer in the Inner Hebrides of Scotland change as a result of age-related movement and social structure. We found that the age-related changes in infection patterns were not due to age-related changes movement or social structure, implying that physiological mechanisms (i.e., immune changes over time) may be driving the infection patterns.
Lay Summary:
We investigated if infection with different parasites in red deer in the Inner Hebrides of Scotland change as the deer age. We found that the older deer having more or less parasites was not because the deer moved to different parts of the island nor because of which deer they spent their time with. This suggests that there are other changes that occur as the deer age that are making the deer have more or less parasites.
09
Bartonella infections are prevalent in rodents despite efficient immune responses.
Parasites & Vectors
Rodríguez-Pastor, R.; Hasik, A.Z. (co-first author) et al. (2023)
Technical Summary:
Gerbils in southern Israel are often infected by multiple parasites. To test if this was due to immune defenses waning over time, we monitored infection and immune dynamics using bacterial parasites. We found that both infection levels and immune defenses remained high, suggesting that high prevalence in wild populations is due to another mechanism.
Lay Summary:
We conducted an experiment using bacterial parasites and rodents sourced from southern Israel to understand why gerbils are always infected. We found that their immune systems do not weaken when infected, suggesting that a weak immune system is not why they’re always infected.
10
Interspecific host competition and parasite virulence evolution.
Biology Letters
Hasik et al. (2023)
Technical Summary:In this paper, we use evidence from empirical studies and evolutionary theory to suggest that competition between host species can affect the evolution of parasite virulence.
Lay Summary:
Using evidence from other studies, we suggest that competition among species can affect how much harm their parasites do to them.
11
Resetting our expectations for parasites and their effects on species interactions: a meta-analysis.
Ecology Letters
Hasik et al. (2023)
Technical Summary:
We conducted a phylogenetically-informed meta-analysis of the effects of parasites on the species interaction of their hosts. We found that although there was no net overall effect, the effects of parasites ranged from overwhelmingly positive to overwhelmingly negative.
Lay Summary:
We wanted to understand how parasites affect the way that the organisms they infect interact with predators and competitors. Analyzing data from other studies we found that there was no consistent effect but that the impact of parasites was context-dependent.
12
Odonata Immunity, Pathogens, and Parasites.
Dragonflies and Damselflies: Model Organisms for Ecological and Evolutionary Research, 2nd edition.
Hasik et al. (2023)
Technical/Lay Summary:
In the book chapter, we describe the various parasites infecting dragonflies and damselflies, as well as the tools the hosts use to defend themselves.
13
Evolutionary Community Ecology of Odonates.
Dragonflies and Damselflies: Model Organisms for Ecological and Evolutionary Research, 2nd edition.
Siepielski et al. (2023)
Technical/Lay Summary:
In this book chapter, we describe the ecology and evolution of dragonflies and damselflies.
14
A common measure of prey immune function is not constrained by the cascading effects of predators.
Evolutionary Ecology
Hasik et al. (2023)
Technical Summary:
We used lab and field experiments in the southeastern United States to understand if the anti-predator behavior of damselfly prey affected the strength of their immune defenses. We found no evidence that fish predators had an effect, only resource availability determined the strength of damselfly immune defenses.
Lay Summary:
We wanted to test if fish caused damselflies to eat less and therefore weaken their immune system. We found that only the amount of food that the damselflies ate and not the fish affected their immune system.
15
Parasitism shapes selection by drastically reducing host fitness and increasing host fitness variation.
Biology Letters
Hasik & Siepielski (2022)
Technical Summary:
We used a phylogenetically-informed meta-analysis to understand how parasites affect the fitness of their hosts. We found that parasites had a strong negative effect, with additional evidence suggesting that parasites increase the opportunity for selection.
Lay Summary:
Using data from other studies, we tested how parasite infection can affect host reproduction, finding that parasites strongly reduce the hosts’ ability to reproduce. We also found that the effects of parasites improved their hosts’ ability to evolve over time.
16
A role for the local environment in driving species-specific parasitism in a multi-host parasite system.
Freshwater Biology
Hasik & Siepielski (2022)
Technical Summary:
Using field experiments with damselflies in the southeastern United States, we tested if parasitism was driven by host population density, resource availability, or was instead determined by host species identity. We found that neither density nor resource availability affected parasitism, instead host species identity was the sole driver of infection.
Lay Summary:
Using damselflies in the southeastern United States, we tested if parasites prefer specific damselfly species or if they prefer the species with the highest population number. We found that the parasites strongly prefer to infect one species and the population number of the damselflies had no effect.
17
Predators weaken prey intraspecific competition through phenotypic selection.
Ecology Letters
Siepielski et al. (2020)
Technical Summary:
We used lab and field experiments in the southeastern United States to test if fish predation pressure affected the strength of damselfly competition with other damselflies. We found that fish predators reduced damselfly activity, which also reduced the strength of their competitive interactions.
Lay Summary:
We used lab and field experiments in the southeastern United States to test how fish affect how much food damselflies eat. We found that when there are more fish around damselflies eat less, which means there is less competition for their food.
18
Past selection impacts the strength of an aquatic trophic cascade.
Functional Ecology
Ousterhout et al. (2018)
Technical Summary:
We used lab and field experiments in the southeastern United States to test if fish predators affect how much prey damselflies consume. We found that the strength of fish predation pressure affected damselfly activity, which then affected the prey communities of the damselflies, which in turn affected the primary productivity of the ponds themselves.
Lay Summary:
We used lab and field experiments in the southeastern United States to test if fish make damselflies eat less food. We found that when there are more fish around the damselflies eat less food, which then has an effect on the plant matter in the ponds themselves.
19
An ecological and evolutionary perspective on coexistence under global change.
Current Opinion in Insect Science
Siepielski et al. (2018)
Technical/Lay Summary:
We discuss how global change (i.e., global warming) is affecting insects in the wild and whether or not prior studies have properly investigated how insect species coexist with one another. We found that very few studies properly demonstrated coexistence in wild insects and suggest that future research focus on both ecological and evolutionary angles.