Functional Roles of Parasitic Plants in a Warming World

Abstract

We consider the mechanistic basis and functional significance of the pervasive influence of parasitic plants on productivity and diversity, synthesizing recent findings on their responses to drought, heat waves, and fire. Although parasites represent just 1% of all angiosperms, the ecophysiological traits associated with parasitism confer pronounced impacts on their hosts and disproportionate influence upon community structure, composition, and broader ecosystem function. New insights into the roles of their pollinators, seed dispersers, and litter-dependent detritivores have advanced our understanding of how parasitic plants modulate animal communities via their extended and complementary phenology. Direct and indirect impacts of climate change on parasitic plants and their ecological roles are already apparent. Trade-offs between maximizing efficiency at obtaining water from hosts and sensitivity to water stress underlie range shifts and host switching of parasitic plants and increased reliance on these plants by animal communities for food and shelter. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 53 is November 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mistletoes could moderate drought impacts on birds, but are themselves susceptible to drought-induced dieback

“…We also found effects of tree species composition on mistletoe abundance. Many mistletoe species are specialists on a small range of host tree genera [ 39 ], with specialisation at the genus or family level associated with increased susceptibility to drought [ 10 ]. In terms of our study species, needle-leaf mistletoes are specialists on she-oaks, which fringe riparian zones throughout southeastern Australia.…”

“…The results of our models reflected these trends, detecting a negative association between overall tree health and dead mistletoe abundance ( figure 2 a and electronic supplementary material, figure S7). The effect was small, however, suggesting that drought-induced die-off of host tree species only partly explains observed patterns of mistletoe mortality and that mistletoes are unlikely to be a key driver of host-tree mortality during drought [ 5 , 10 ].…”

“…By retaining cations in semi-succulent foliage, mistletoes maintain water balance by passively drawing down a concentration gradient [ 8 , 9 ]. While this enriches tissues, increases water flux and likely within-canopy humidity [ 10 ], their limited control over stomatal closure makes mistletoes sensitive to sudden reductions in moisture availability [ 7 ], with increased evapotranspiration from prolonged hot/dry conditions associated with mistletoe mortality [ 11 , 12 ].…”

“…Consequently, mistletoes provide predictable and reliable resources during droughts when ecosystem productivity such as eucalypt flowering is otherwise low [ 16 ]. Lush, dense foliage of healthy mistletoes are a key browsing resource for arboreal mammals and create microclimates that moderate temperature extremes [ 10 , 18 ], making mistletoe favourable nesting and roosting sites for many bird species [ 9 ]. With predicted increases in the frequencies of prolonged droughts and severe heatwaves under climate change [ 19 , 20 ], more species may depend on live mistletoe to survive such events in coming decades.…”

Protein Profiling of Psittacanthus calyculatus during Mesquite Infection

“…Parasitic plants are angiosperms that need to attach to other plants that are susceptible to being parasitized, and obtain nutrients from them through a specialized structure called a haustorium [ 1 ]. More than 4750 of the 374,000 reported flowering plants have a parasitic habit [ 2 ]. The parasitic plant diversity depends on the habit and site of attachment on the host and their ability to acquire nutrients derived from the host metabolism [ 3 , 4 ].…”