Predicting network topology of mistletoe–host interactions: do mistletoes really mimic their hosts?

Abstract

Network analysis provides a unified framework for investigating different types of species interactions at the community level. Network analysis is typically based on null models that test for specific patterns in network topology. Here we use a novel predictive approach to investigate the topology of a mistletoe-host network. It has been hypothesised that Australian mistletoes mimic the phenotype of their preferred hosts to avoid herbivory. We developed a deterministic model based on phenotypic similarity to predict the topology of a quantitative network between Lauranthaceaous mistletoes and their hosts. We quantified mistletoe-host interactions in a semi-arid woodland central Australia, along with the size, shape and colour of leaves produced by both players in the interaction. Traditional null model analyses showed support for negative co-occurrence patterns, web specialisation and strong links between species pairs. However, our deterministic model showed that the observed network topology could not be predicted by phenotypic similarity, suggesting that Australian mistletoes do not mimic their hosts.

Dominant network interactions are not correlated with resource availability: a case study using mistletoe host interactions

“…We recorded the number of individual mistletoes occurring on all trees as a single quantitative interaction matrix. Previous analyses of network structure at Fowlers Gap indicated that each mistletoe species occurs on a specific set of host tree species (conducted November 2009; Blick et al 2012). However, after surveying the same vegetation in August of 2011 we found A. maidenii growing on an additional host species ( Acacia tetragonophylla ) and A. preissii growing on two additional host species ( Acacia aneura and A. tetragonophylla ) indicating that a greater number of interactions in this plant community are possible, albeit rare.…”

“…Dispersion of individuals may be inextricably linked with resource availability in the community. Resource availability is critically important for mistletoes because each species is dependent on a specific set of host tree species in the community (Blick and Burns 2009, Blick et al 2012, Genini et al 2011). Thus, the number of interactions observed in a community may be determined by the relative number of mistletoe individuals and the number of trees in the ecosystem.…”

What causes size coupling in fruit–frugivore interaction webs?

“…Similar circumstances may apply to other types of ecological interactions, such as flower-pollinator and mistletoe-host interactions (c.f. Stang et al 2006, Olsen et al 2011, Blick et al 2012.…”

Host specificity in parasitic plants—perspectives from mistletoes

“…3). A negative co-occurrence pattern in mistletoe species that specialize on distinct suites of host species has been also reported in North America, New Zealand and Australia (Hawksworth and Wiens 1972; Blick and Burns 2009; Blick et al 2012). Similarly, Fadini (2011) showed that three congeneric and sympatric mistletoe species ( Psittacanthus biternatus , P. eucalyptifolius and P. plagiophyllus ) specialize on different host species in the Amazon.…”

“…The generalist mistletoes may encounter host species that vary in compatibility at different locality, thus may parasitize a subset of available host species at a given locality. This process could drive mistletoe specialization by selecting for host-specific adaptation at a local level (Norton and Carpenter 1998; Norton and de Lange 1999; Amico et al 2007; Blick et al 2012; Kavanagh and Burns 2012). …”