Fungal infections pose a threat to various species globally. While many fungi play beneficial roles, certain species cause diseases, leading to population declines or extinctions. Understanding which species are most vulnerable is important for developing effective conservation strategies.
Biological Traits Increasing Susceptibility
Certain inherent biological characteristics can render species more susceptible to fungal pathogens. An inefficient immune system leaves organisms less equipped to combat fungi. Some species may have genetic variations leading to a compromised immune response, hindering their ability to clear fungal threats.
Genetic homogeneity within a population means there is little genetic diversity, which can be a disadvantage. Without diverse immune genes or resistance, a single pathogen strain can rapidly devastate a population. Specific physiological needs, like reliance on narrow temperature or humidity ranges, can increase infection risk if these conditions also favor fungal growth. Life history traits, including long lifespans, can increase an individual’s cumulative exposure to pathogens, while slow reproductive rates can hinder a population’s ability to recover from disease outbreaks.
Environmental Factors Amplifying Risk
External environmental conditions and human-induced alterations often amplify the risk of fungal infections in wildlife. Climate change alters temperatures and humidity, creating environments conducive to fungal proliferation or stressing host organisms, weakening their defenses. Extreme weather events can also facilitate fungal spore dispersal, spreading diseases.
Habitat degradation and loss reduce population health and size, increasing susceptibility to disease outbreaks and limiting escape from infected areas. Pollution weakens animal immune systems, diminishing their capacity to fight infections. Global trade and travel facilitate rapid pathogen spread, introducing novel fungal threats to naive populations lacking co-evolved resistance.
Amphibians and Chytrid Fungi
Amphibians are vulnerable to chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). Their highly permeable skin, essential for respiration and water absorption, makes them susceptible to fungal invasion. Bd infects skin keratinized cells, disrupting fluid transport and gas exchange, leading to electrolyte imbalance and cardiac arrest.
Amphibians’ reliance on aquatic environments for breeding exposes them to these waterborne pathogens. Their immune systems can be compromised by environmental stressors, reducing their ability to combat infection. Climate change, by altering temperatures and humidity, can create optimal conditions for chytrid fungi or stress amphibian populations.
Bats and White-Nose Syndrome
Bats face White-Nose Syndrome (WNS), a fungal disease caused by Pseudogymnoascus destructans (Pd). This fungus thrives in the cold, damp conditions of caves and mines where bats hibernate. Communal hibernation facilitates rapid fungal transmission within crowded hibernacula.
During hibernation, bats lower their body temperature and suppress immune systems, creating an ideal environment for Pd to grow on their skin. The infection causes frequent arousals from torpor, depleting fat reserves. This energy expenditure leads to weight loss, dehydration, and electrolyte imbalances, often resulting in starvation or freezing. Human disturbance in caves can spread the fungus or stress hibernating bats, exacerbating the disease’s impact.
Threats to Reptiles and Plants
Reptiles are affected by emerging fungal diseases like Snake Fungal Disease (SFD), caused by Ophidiomyces ophiodiicola. This fungus infects the skin, leading to crusted or ulcerated scales, nodules, and disfiguration. These lesions can impair shedding, feeding, and movement. Environmental factors, including moist conditions, can promote fungal growth and persistence, making certain habitats conducive to outbreaks.
Plants face numerous fungal threats, often exacerbated by human practices and environmental shifts. Ash Dieback, caused by Hymenoscyphus fraxineus, shows how a lack of genetic diversity in tree populations can make species vulnerable. Dutch Elm Disease, caused by Ophiostoma ulmi, devastated elm populations due to monoculture planting and lack of resistance. Bark beetles efficiently spread these pathogens, and climate change can influence their geographic range and severity.
References
Amphibian Chytrid Fungus. U.S. Geological Survey. [https://www.usgs.gov/centers/nwhc/science/amphibian-chytrid-fungus](https://www.usgs.gov/centers/nwhc/science/amphibian-chytrid-fungus)
White-Nose Syndrome. National Park Service. [https://www.nps.gov/articles/white-nose-syndrome.htm](https://www.nps.gov/articles/white-nose-syndrome.htm)
Snake Fungal Disease. U.S. Geological Survey. [https://www.usgs.gov/centers/nwhc/science/snake-fungal-disease](https://www.usgs.gov/centers/nwhc/science/snake-fungal-disease)
Ash dieback. The Woodland Trust. [https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/tree-diseases/ash-dieback/](https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/tree-diseases/ash-dieback/)
Dutch elm disease. The Woodland Trust. [https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/tree-diseases/dutch-elm-disease/](https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/tree-diseases/dutch-elm-disease/)