Mistletoes are a group of shrubs that obtain nutrients from host plants through haustoria. Despite extensive studies on the effects of mistletoes on host plants, ecosystems, other organisms, and host-herbivore interactions, little is known about the effects of host plants on mistletoe herbivory. 

In a study published in Oecologia, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences presented a distinct pattern of effects associated with mistletoe herbivory in host plants. They investigated the effect of host species on parasitic mistletoe herbivory by examining the herbivory rates and defensive traits of three mistletoe species growing on a combined total of 11 host species.

The researchers measured leaf herbivory and leaf traits of three mistletoe species (Dendrophthoe pentandra, Scurrula chingii var. yunnanensis, and Helixanthera parasitica) and their associated 11 host species during both dry and wet seasons.

They found that leaf herbivory by D. pentandra and S. chingii var. yunnanensis varied significantly among different host species, while H. parasitica showed no significant variation. In addition, mistletoe herbivory was positively correlated with host plant leaf herbivory, with a strong positive correlation during the dry season.

Certain leaf chemical traits showed a significant positive relationship between mistletoe and host plants. However, no similar relationships were found for leaf moisture, leaf toughness, leaf thickness, and specific leaf area, suggesting that mistletoe leaf chemical traits may be influenced by their host traits. Mistletoe leaf herbivory was best predicted by a combination of mistletoe leaf traits, including total nitrogen (TN) and leaf thickness. The effect of TN on mistletoe herbivory was stronger in the wet season compared to the dry season.

"We have described a clear associative effect of parasitic host plants on herbivores, which differs from the neighboring plants in the same community. Our study suggests that mistletoe leaf herbivory is directly influenced by its leaf traits and indirectly affected by host associational effects, mainly through changes in mistletoe leaf traits," said ZHANG Ling of XTBG.