When can host shifts produce congruent host and parasite phylogenies? A simulation approach

Abstract

Congruence between host and parasite phylogenies is often taken as evidence for cospeciation. However, ‘pseudocospeciation’, resulting from host‐switches followed by parasite speciation, may also generate congruent trees. To investigate this process and the conditions favouring its appearance, we here simulated the adaptive radiation of a parasite onto a new range of hosts. A very high congruence between the host tree and the resulting parasite trees was obtained when parasites switched between closely related hosts. Setting a shorter time lag for speciation after switches between distantly related hosts further increased the degree of congruence. The shape of the host tree, however, had a strong impact, as no congruence could be obtained when starting with highly unbalanced host trees. The strong congruences obtained were erroneously interpreted as the result of cospeciations by commonly used phylogenetic software packages despite the fact that all speciations resulted from host‐switches in our model. These results highlight the importance of estimating the age of nodes in host and parasite phylogenies when testing for cospeciation and also demonstrate that the results obtained with software packages simulating evolutionary events must be interpreted with caution.

Host-plant specificity and specialization in eriophyoid mites and their importance for the use of eriophyoid mites as biocontrol agents of weeds

“…Too little is known about either host-switching events or coevolution with plants in regards to speciation of eriophyoids. Undoubtedly, there is a strong demand for more phylogenetic comparisons of eriophyoids and their hosts and new molecular tools developed in recent years have great potential to facilitate such studies, although analysis is not always straightforward (Vienne et al 2007). …”

Cophylogenetic interactions between marine viruses and eukaryotic picophytoplankton

“…a significant amount of concomitant speciation in hosts and their parasites. For example, a host switch to a sister host species followed by a speciation of the parasite produces a false cospeciation pattern [58,65,67]. If this process is common across the whole host-parasite association, a spurious cospeciation signal might be found when comparing topologies [39], and this may lead to an overestimation of cospeciation patterns by cophylogenetic methods [68].…”

Speciation in fungi

“…Interestingly, the fungal symbionts do not appear to have free dispersal stages, which could restrain the possibility of host shifts. However, congruence between host and parasite trees is not always evidence for rampant cospeciations because host shifts can give rise to congruent phylogenies if they occur preferentially towards closely related hosts (de Vienne et al, 2007b). Temporal concordance therefore needs to be assessed with appropriate tests in order to elucidate whether cospeciation has occurred (de Vienne et al, 2007b;Hirose et al, 2005;Schardl et al, in press).…”