Is palatability of a root-hemiparasitic plant influenced by its host species?

Abstract

Palatability of parasitic plants may be influenced by their host species, because the parasites take up nutrients and secondary compounds from the hosts. If parasitic plants acquired the full spectrum of secondary compounds from their host, one would expect a correlation between host and parasite palatability. We examined the palatability of leaves of the root-hemiparasite Melampyrum arvense grown with different host plants and the palatability of these host plants for two generalist herbivores, the caterpillar of Spodoptera littoralis and the slug Arion lusitanicus. We used 19 species of host plants from 11 families that are known to contain a wide spectrum of anti-herbivore compounds. Growth of M. arvense was strongly influenced by the host species. The palatability of the individual host species for the two herbivores differed strongly. Both A. lusitanicus and S. littoralis discriminated also between hemiparasites grown with different host plants. There was no correlation between the palatability of a host species and that of the parasites grown on that host, i.e., hemiparasites grown on palatable host species were not more palatable than those grown on unpalatable hosts. We suggest an interacting pattern of specific effects of chemical anti-herbivore defences and indirect effects of the hosts on herbivores through effects on growth and tissue quality of the parasites.

Hemiparasites can transmit indirect effects from their host plants to herbivores

“…To our knowledge, this possibility has not been explored to date, although it was hypothesized by Schädler et al. (). Since the herbivore we tested sequesters secondary metabolites, we expected chemical concentrations in the herbivore to correspond to those in the hemiparasite.…”

“…, Schädler et al. , Rowntree et al. ), but we know little about the traits that mediate this effect.…”

Glucosinolates from Host Plants Influence Growth of the Parasitic Plant Cuscuta gronovii and Its Susceptibility to Aphid Feeding

“…The latter hypothesis was posited four decades ago (Atsatt, 1977) but has rarely been subjected to rigorous empirical investigation, at least in part because it is difficult to isolate the effects of particular host metabolites from other aspects of the host-parasite interaction. For example, herbivore success in feeding on particular parasite species has been shown to vary when the parasite feeds on different hosts (Harvey, 1966;Marvier, 1996Marvier, , 1998Adler, 2002;Schädler et al, 2005;Rowntree et al, 2014), but this variation could be influenced by a wide range of factors other than host secondary metabolites, including parasite biomass accumulation (Rowntree et al, 2014), nitrogen content (Marvier, 1998), volatile emission patterns (Troncoso et al, 2010), and, presumably, parasite endogenous defenses. Consequently, it is hardly surprising that studies noting the transfer of insect-deterrent secondary metabolites into parasitic plants have reported inconsistent effects on insect herbivores (Stermitz et al, 1989;Marko, 1996;Marvier, 1996;Loveys and Tyerman, 2001;Adler, 2002;Adler, 2003), as few studies (Adler, 2000;Adler et al, 2001) effectively controlled for other potential influences of the host species on parasite resistance to (or quality for) herbivores.…”

Effects of Melampyrum extracts on the growth of axenic cultures of Cronartium flaccidum and Peridermium pini

“…This echoes the variation noted in virulence (Kaitera and Nuorteva 2008) and alternate host range of these rusts (Kaitera and Nuorteva 2003a, b). Chemical differences among Melampyrum species may be based on the physiological factors or linked to the relationship between the host plant and their ectomycorrhizal fungi (Salonen et al 2000, Phoenix and Press 2005, Schädler et al 2005, Walter 2005. Future work in this system should identify the phytocompounds produced by M. sylvaticum and M. pratense that are involved in their variable susceptibility to pine stem rusts.…”