How vulnerable are holoparasitic plants with obligate hosts to negative climate change impacts?

Abstract

One of the anthropogenic causes affecting species distribution is climate change, which has significant implications for species conservation. However, little is known about the effects of changes in parasitic plant distribution on community-level interactions. Parasitic flowering plants make a limited numerical contribution to biodiversity. Their lifestyle may exhibit a moderate to the high degree of host dependence. Because of this host dependence, parasites may be more affected by environmental changes, such as climate change, compared to autotrophic representatives. To our knowledge, the effects of different climate change scenarios and their environmental variables on parasitic plants and their hosts have not yet been studied. This study aimed to construct a model which shows the current and future potential effects of climate change on the distribution of the two holoparasitic plants Hydnora abyssinica A.Br., and H. africana Thunb. in comparison to their respective Fabaceae and Euphorbiaceae hosts. We projected the future distribution of these species and their host plants using five models, nine bioclimatic, and five environmental variables. The global circulation model (CMIP5) for the years 2050 and 2070, applying two representative concentration pathways scenarios (RCP4.5 and RCP8.5) projected a 41–64% contraction of suitable habitats for H. abyssinica. For H. africana, more stable conditions are estimated, with a 12–28% contraction in suitable habitats, making this species putatively less prone to climate change effects, although this species has a more restricted distribution compared to H. abyssinica. Because climate change could affect the host differently than the parasites, the impact on the parasite could potentially be exacerbated due to host plant dependence. The models predict that the host plant distribution will be less affected, except for Vachelia Karroo, Vachellia xanthophloea, and Euphorbia gregaria, which indicated high contraction (40–66%). The predicted host species distribution ranges will only partially overlap with the respective distribution of the parasite.