Parasitism modifies the direct effects of warming on a hemiparasite and its host

Abstract

Climate change is affecting interactions among species, including host-parasite interactions. The effects of warming are of particular interest for interactions in which parasite and host physiology are intertwined, such as those between parasitic plants and their hosts. However, little is known about how warming will affect plant parasitic interactions, hindering our ability to predict how host and parasite species will respond to climate change. Here, we test how warming affects aboveground and belowground biomass of a hemiparasitic species (Castilleja sulphurea) and its host (Bouteloua gracilis), asking whether the effects of warming depend on the interaction between these species. We also measured how warming affected the number of haustorial connections between parasite and host. We grew each species alone and together under ambient and warmed conditions. Hosts produced more belowground biomass under warming. However, host biomass was reduced when plants were grown with a hemiparasite. Thus, parasitism negated the benefit of warming on belowground growth of the host. Host resource allocation to roots versus shoots also changed in response to both interaction with the parasite and warming, with hosts producing more root biomass relative to shoot biomass when grown with a parasite and when warmed. As expected, hemiparasite biomass was greater when grown with a host. Warmed parasites had lower root:shoot ratios but only when grown with a host. Under elevated temperatures, hemiparasite aboveground biomass was marginally greater, and plants produced significantly more haustoria. These findings indicate that warming can influence biomass production, both by modifying the interaction between host plants and hemiparasites and by affecting the growth of each species directly. To predict how species will be affected, it is important to understand not only the direct effects of warming but also the indirect effects that are mediated by species interactions. Ultimately, understanding how climate change will affect species interactions is key to understanding how it will affect individual species.

Distinct patterns of soil bacterial and fungal community assemblages in subtropical forest ecosystems under warming

“…As suggested elsewhere, warming may accelerate the degradation of organic compounds in forest soils and emissions of greenhouse gas by bacteria (Yang et al, 2016; Yu et al, 2021), given the increases in relative abundance of bacteria involved in chemoheterotrophy, fermentation, and ureolysis under S2 compared with ambient conditions (S0). Our finding of greater relative abundance of bacterial OTUs associated with animal parasites/symbionts and gut functions under increased temperatures indicates that animal health and plant productivity have potential to be impacted by climate warming in forest ecosystems (Kutz et al, 2005; Rafferty et al, 2019), while temperature‐related increases in the relative abundance of OTUs associated with saprotrophic fungi that mediate nutrient cycling indicate that warming may accelerate key forest ecosystem processes (Pec et al, 2021).…”

High temperature perception in leaves promotes vascular regeneration and graft formation in distant tissues

“…Parasitic plant infections are conceptually similar to grafting ( Kokla and Melnyk, 2018 ) and their infective structures, haustoria, form xylem connections known as xylem bridges to their hosts to withdraw nutrients. Elevated temperatures can increase haustoria numbers ( Rafferty et al, 2019 ), but we found that elevated temperatures did not affect haustoria number during A. thaliana infection by the facultative parasite P. japonicum ( ).…”

The Angiosperm Stem Hemiparasitic Genus Cassytha (Lauraceae) and Its Host Interactions: A Review

“…Temperature is the prevailing environmental factor that influences plant growth, and also affects angiosperm parasite–host interactions. A case study involving the interaction between the hemiparasite Castilleja sulphurea and its host Bouteloua gracilis under circumstances of changing environment has found that a 3°C temperature increase in summer exacerbated the adverse effects on host species due to the production of more haustoria and aboveground biomass of the hemiparasite ( Rafferty et al, 2019 ). Bell et al (2020) have also found increased effects of the dwarf mistletoe ( Arceuthobium tsugense ) on hemlock Tsuga heterophylla under warmer and drier conditions.…”