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, limited knowledge exists regarding the impact of host plants on mistletoe herbivory.
In a study published in Oecologia, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) presented a distinct pattern of associational effects mistletoe herbivory in host plants. They investigated the impact 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 did not show significant variation. Additionally, mistletoe herbivory was positively related with host plant leaf herbivory, with a strong positive correlation during the dry season.
Certain leaf chemical traits showed a significant positive association between mistletoes and host plants. However, no similar relationships were found for leaf moisture, leaf toughness, leaf thickness, and specific leaf area, indicating that mistletoe leaf chemical traits can 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 during the wet season compared to the dry season.
“We have described a distinct associational effect for the parasitic–host plants upon herbivores, which differs from the neighboring plants in same community. Our study suggests that mistletoe leaf herbivory is directly affected by its leaf traits and indirectly affected by host associational effects, primarily through changes in the mistletoes' leaf traits,” said ZHANG Ling of XTBG.

Contact
ZHANG Ling Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail:zhangl@xtbg.org.cn
First published: 9 January 2024