Interaction network of Phoradendron and its hosts and the influence of phylogenetic, geographic, and environmental factors on the probability of interaction

Premise

Phoradendron (Santalaceae) mistletoes consist of approximately 230 hemiparasitic species across the Americas. As obligate hemiparasites, their distribution depends partly on the distribution of their hosts, reflecting a shared evolutionary history.

Methods

Using network analysis and statistical modeling, we explored the bipartite host–parasite network, focusing on species organization and the likelihood of hosts sharing a Phoradendron species based on phylogenetic, geographic, and environmental factors.

Results

Our analysis suggests a modular and highly specialized interaction network influenced by evolutionary and biogeographical factors. Phoradendron parasitized hosts in genera from various families and orders, primarily Fabales, Malpighiales, and Sapindales. The network exhibited modularity and connectivity, with hosts sharing a higher likelihood of being parasitized by the same Phoradendron species when they were closer in phylogeny, geography, and environment, while phylogenetic distance emerged as the most relevant determinant. Moreover, we established a link between Phoradendron within-module connectivity and host phylogenetic distance, providing an evolutionary framework for understanding ecological patterns and network connectance.

Conclusions

The network of Phoradendron–host interactions is highly specialized, and the structure of this network depends mainly on the phylogenetic distance of the hosts.