Constraints on host use by a parasitic plant

Abstract

Consumers do not always utilize all suitable hosts. Understanding why parasitic plants do not always parasitize potentially suitable hosts requires a better understanding of the constraints that limit host use by parasitic plants. In Texas salt marshes, the parasitic plant Cuscuta indecora rarely parasitizes three hosts that support vigorous growth in the greenhouse. We identified three constraints on host use by C. indecora. First, a mismatch between the phenology of C. indecora and some suitable hosts meant that these hosts were not abundant when C. indecora was growing most vigorously, and therefore were underutilized. Second, C. indecora preferentially parasitized tall plants versus short ones, causing relatively short species to be underutilized. Third, C. indecora overwinters in some perennial hosts but has to reinfect annual hosts each year, causing annuals and perennials that do not support overwintering to be underutilized. In combination, these constraints, which reflect the general lack of mobility of parasitic plants relative to herbivores, remove half of the potential host species from the actual diet of C. indecora, and therefore likely represent a major limitation on the success of this parasite. Similar constraints are likely to limit the realized host range of many parasitic plants and select for generalized diet preferences.

Host preference of a temperate mistletoe: Disproportional infection on three co‐occurring host species influenced by differential success

“…This study is an approximation to factors affecting host use by a hemiparasitic plant, an issue which has seldom been addressed in the literature (Marquardt & Pennings 2010). The results showed that incidence and intensity of parasitic infection by T. verticillatus in the YLNS was disproportional to the availability and appearance of the three co-occurring hosts, S. montanus being the least abundant and less apparent host but that with the highest incidence and intensity of infection.…”

Range‐wide ecological niche comparisons of parasite, hosts and dispersers in a vector‐borne plant parasite system

“…As proposed in the 'host-quality hypothesis' (Watson, 2009), variation in host quality may account for non-random occurrence patterns of parasitic plants: parasites are expected to establish and survive on higher-quality hosts. Host quality for mistletoes often depends on tree height and architecture, bark texture, age and accessibility to water or drainage sites, and host species (Norton et al, 1997;Lei, 1999;Norton & Smith, 1999;Aukema & Mart ınez del Rio, 2002b;Callaway et al, 2002;Marquardt & Pennings, 2010). Examples of differential responses to host quality in P. californicum include birds' general preference for taller trees with larger numbers of mistletoe plantscausing concentrated intra-host infections (Aukema & Mart ınez del Rio, 2002a,b) and the responses of birds to mistletoe prevalence, causing disproportionate seed deposition patterns (Overton, 1996;Aukema, 2004).…”

Mistletoe macroecology: spatial patterns in species diversity and host use across Australia

“…Co‐evolutionary processes between Acacia and Eucalyptus host species may have been important in determining host ranges, similar to relationships between misteltoes and Nothafagus hosts in New Zealand (Norton & de Lange, 1999). Marquardt & Pennings (2010) demonstrated that the parasitic plant Cuscuta indecora did not parasitize all potential hosts, because of mismatches in parasite–host phenologies, preferential infection of tall hosts, and the apparent inability of some hosts to repel infection. A similar explanation might explain variability in the relationship between host range and plant species richness.…”