Small and fragmented populations of hemiparasitic plants are dependent upon their host species and can be susceptible to inbreeding depression. In addition, they may also be strongly affected by a lack of suitable host species.
This study of selfed and open-pollinated parasites by Sandner and Matthies of two natural populations of the declining root hemiparasite Rhinanthus alectorolophus indicates that inbreeding depression was lowest for parasites grown with mixtures of hosts from three functional groups (grasses, forbs, legumes), suggesting the benefits of genetically diverse host communities. However, inbreeding did not affect specific host–parasite interactions.
Sandner, T. M., & Matthies, D. (2016). Interactions of inbreeding and stress by poor host quality in a root hemiparasite. Annals of Botany, 119(1), 143–150. https://doi.org/10.1093/aob/mcw190