Habitat structure and ecological drivers of disease

Abstract

Habitat can influence disease directly, through effects on hosts and parasites, or indirectly, through effects on ecological drivers of disease. We illustrated direct and indirect connections between habitat and outbreaks using a case study in the plankton. We sampled yeast epidemics in 18 populations of the lake zooplankter Daphnia dentifera. Lake size drove variation in two types of habitat structure, size of predation refuges and strength of stratification. Those habitat factors, in turn, indirectly linked to epidemics through two pathways involving nonhost species. In the first pathway, larger lakes had larger hypolimnetic refuges from vertebrate predation and greater densities of Daphnia pulicaria, a completely resistant species that can reduce disease risk for D. dentifera hosts by removing parasite spores from the environment. In lakes with more D. pulicaria, epidemics started later in autumn and remained smaller. In the second pathway, smaller lakes had shallower penetration of light, which correlated with stronger thermal stratification and higher densities of an invertebrate predator (Chaoborus) that spreads disease by releasing spores from infected hosts. Lakes with weaker stratification had fewer of these predators and smaller epidemics. In the second pathway, deeper light penetration may also decrease disease by imposing direct mortality on spores. Thus, this case study shows how habitat structure could influence epidemics through direct and indirect effects on the host-parasite system. Understanding these multiple mechanisms can enhance prediction of disease outbreaks as habitat modification continues in lakes and other ecosystems worldwide.

Understanding the ecology and evolution of host–parasite interactions across scales

“…This result likely reflects both the lack of parasite dispersal between lakes and the fact that lakes vary strongly in habitat characteristics and ecological drivers of disease (Penczykowski et al. ). Among populations of Pl.…”

Joint effects of habitat, zooplankton, host stage structure and diversity on amphibian chytrid

“…Armed with additional data, path analysis might further delineate the correlated pathways that modulate disease in this and other systems [42,43]. In the meantime, these present results demonstrate the importance of creating mechanistic, food web-based links between multiple habitat dimensions and disease [7][8][9]. Infection reached higher prevalence in ponds with more UVR, despite that UVR reduced survival of the free-living stage of the parasite (i.e.…”

“…Why? It remains challenging to answer this question because multiple correlated pathways drive disease [7][8][9]. Furthermore, these pathways may have contrasting effects; some factors enhance disease while others diminish it.…”

Parasites destabilize host populations by shifting stage‐structured interactions

“…These lakes span a total phosphorous (TP) gradient from low nutrient (oligotrophic) to higher nutrient (eutrophic): a range of 4–54 μg P/L (Penczykowski et al. ). At each visit, we collected hosts with two replicate plankton samples using a Wisconsin net (13 cm diameter, 153 μm mesh; towed bottom to surface).…”