Ancestral networks
Ecological interactions between extant species form networks where the species are the nodes that are connected by edges that represent the ecological interactions. In the past few decades, we’ve learned a lot about the structure of these networks, that is, how the interactions are organised, and how this varies in geographic space and with kinds of ecological interaction.
A less explored question is how networks vary over time, especially over deep-time scales. With the recent development of a method that allows the inference of ancestral interactions among multiple species (Braga et al. 2020 Syst Biol), it is now possible to reconstruct ancestral networks and thus, how they change over time.
So far, the method has only been applied to butterfly-host plant networks (Braga et al. 2021 Ecol Lett), but it should work for other herbivorous insects, parasites, pollinator-plant, and other mutualisms.
Evolution of the Pieridae-angiosperm network across nine time slices from 80 Ma to the present. Each panel (a–i) shows the butterfly lineages extant at a time slice (left) and the estimated network of interactions with at least 0.5 posterior probability (right). Edge width is proportional to interaction probability. Nodes of the network and tips of the trees are coloured by module, which were identified for each network separately and then matched across networks using the main host plant as reference. Names of the six main host-plant families are shown at the time when they where first colonised by Pieridae. (Click on the figure to see the original paper)
