An Account of the Ecology of the Parasitic Plant Cistanche phelypaea (L.) Cout. (Orobanchaceae) in the Canary Islands and Implications for Its Conservation

Parasitic plants are ecologically important because they can exert a profound influence on the surrounding ecosystem. Yet the ecology and host specificity of most parasitic plant species remain poorly known or undocumented. Cistanche phelypaea is a local and elusive parasitic plant in the Canary Islands. We carried out the first qualitative assessment of this plant’s ecology on the islands by examining 10 subpopulations over a 7-year period. We examined aspects of the plant’s ecology, distribution, and specificity for eight potential host species. Our observations suggest that four species are hosts: Afrosalsola divaricata, Bassia tomentosa, Suaeda vera, and Traganum moquinii, all of which are shrubby Amaranthaceae; however, host specificity varies across the plant’s range. Afrosalsola divaricata was inferred to be the predominant host and was parasitised wherever it co-occurred with the parasite (50% of sites). Cases of inferred parasitism on more than one host species at a given site were rare. Eight of the ten subpopulations occur in areas of high footfall or close to urbanisation; some disturbance, if managed sensitively, appears to favour recruitment and population dynamics. Based on our observations, we suggest that the integration of species distribution models (SDMs) with targeted surveys would be a promising route for scaling up from site-level observations to island-wide inference. We lay the groundwork for practical recommendations informed by such surveys; together with our long-term observations on host range, this offers a template for parasitic plant conservation more broadly.