Contrasting arthropod communities associated with dwarf mistletoes Arceuthobium globosum and A. vaginatum and their host Pinus hartwegii

Arthropod communities and epiphytic plants associated with tree canopies have been widely studied and have revealed a great diversity of organisms; however, the community hosted by parasitic plants, such as dwarf mistletoes, remains poorly known. In the coniferous forests of North America, dwarf mistletoe infection (Arceuthobium spp.) significantly damages the health of the forest, causing large financial losses for the forest industry, but it also positively affects diversity, especially of mammals and birds. This study examined the attributes of the arthropod communities associated with two species of dwarf mistletoe [Arceuthobium globosum Hawksw. & Wiens and A. vaginatum (Humb. & Bonpl. ex Willd.) J. Presl] and their host Pinus hartwegii Lindl. In 2010, in five sites located in Zoquiapan (Central Mexico), we collected plant tissue from the three species bimonthly. Arthropods were separated from the plant tissue and identified to the finest level possible. We collected 32,059 individuals, for which 51 morphospecies were identified, belonging to 15 taxonomic orders; the most abundant orders for the three plants were Prostigmata, Thysanoptera and Homoptera. The community associated with P. hartwegii had the highest value of diversity (H′ = 1.47; A. globosum, H′ = 0.64; A. vaginatum, H′ = 0.68) and species richness (S = 40; A. globosum, S = 30; A. vaginatum, S = 35); while abundance was significantly higher for the mistletoes (A. globosum, n = 407 individuals/sample; A. vaginatum, n = 536 individuals/sample; P. hartwegii, n = 134 individuals/sample). Species richness, abundance and diversity were significantly different for the three studied plants, as well for sampling month and the interaction of these two factors (except for diversity). The results suggest that the canopy of P. hartwegii is an important element in the ecosystem, providing a mosaic of resources and conditions to the associated fauna. We also propose that mistletoes are key species within the forest canopy, as they greatly influence the establishment of diverse organisms, particularly arthropods.