Threat of Disease Increases as Species Move Toward Extinction

• Published in: Conservation biology 2013-12, Vol.27 (6), p.1378-1388
• Main Authors: HEARD, MATTHEW J, SMITH, KATHERINE F, RIPP, KELSEY J, BERGER, MELANIE, CHEN, JANE, DITTMEIER, JUSTIN, GOTER, MAGGIE, MCGARVEY, STEPHEN T, RYAN, ELIZABETH
• Format: Article
• Language: English
• Subjects: amphibians; Amphibians - parasitology; Animal diseases; Animal, plant and microbial ecology; Animals; Applied ecology; Biodiversity; Biological and medical sciences; birds; Birds - parasitology; Conservation biology; Conservation of Natural Resources; Conservation, protection and management of environment and wildlife; Contributed Papers; Disease Susceptibility; en peligro; endangered; Endangered & extinct species; Endangered Species; enfermedad infecciosa; especies amenazadas; extinction; Extinction, Biological; Fundamental and applied biological sciences. Psychology; General aspects; Host-Pathogen Interactions; infectious disease; infectious diseases; invasive species; IUCN; land use change; mammals; Mammals - parasitology; methodology; natural resources conservation; parasite; parasites; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; parásito; pathogen; pathogens; patógeno; Phylogenetics; phylogeny; Population Density; population dynamics; risk; Species Specificity; threatened species; UICN
• ISSN: 0888-8892; 1523-1739
• DOI: 10.1111/cobi.12143

At local scales, infectious disease is a common driver of population declines, but globally it is an infrequent contributor to species extinction and endangerment. For species at risk of extinction from disease important questions remain unanswered, including when does disease become a threat to species and does it co‐occur, predictably, with other threats? Using newly compiled data from the International Union for Conservation of Nature (IUCN) Red List, we examined the relative role and co‐occurrence of threats associated with amphibians, birds, and mammals at 6 levels of extinction risk (i.e., Red List status categories: least concern, near threatened, vulnerable, endangered, critically endangered, and extinct in the wild/extinct). We tested the null hypothesis that the proportion of species threatened by disease is the same in all 6 Red List status categories. Our approach revealed a new method for determining when disease most frequently threatens species at risk of extinction. The proportion of species threatened by disease varied significantly between IUCN status categories and linearly increased for amphibians, birds, and all species combined as these taxa move from move from least concern to critically endangered. Disease was infrequently the single contributing threat. However, when a species was negatively affected by a major threat other than disease (e.g., invasive species, land‐use change) that species was more likely to be simultaneously threatened by disease than species that had no other threats. Potential drivers of these trends include ecological factors, clustering of phylogenetically related species in Red List status categories, discovery bias among species at greater risk of extinction, and availability of data. We echo earlier calls for baseline data on the presence of parasites and pathogens in species when they show the first signs of extinction risk and arguably before. La Amenaza de Enfermedades Incrementa a Medida que las Especies se Aproximan a la Extinción