Phylogenetic and geographic patterns of bartonella host shifts among bat species

Abstract

The influence of factors contributing to parasite diversity in individual hosts and communities are increasingly studied, but there has been less focus on the dominant processes leading to parasite diversification. Using bartonella infections in bats as a model system, we explored the influence of three processes that can contribute to bartonella diversification and lineage formation: (1) spatial correlation in the invasion and transmission of bartonella among bats (phylogeography); (2) divergent adaptation of bartonellae to bat hosts and arthropod vectors; and (3) evolutionary codivergence between bats and bartonellae. Using a combination of global fit techniques and ancestral state reconstruction, we found that codivergence appears to be the dominant process leading to diversification of bartonella in bats, with lineages of bartonellae corresponding to separate bat suborders, superfamilies, and families. Furthermore, we estimated the rates at which bartonellae shift bat hosts across taxonomic scales (suborders, superfamilies, and families) and found that transition rates decrease with increasing taxonomic distance, providing support for a mechanism that can contribute to the observed evolutionary congruence between bats and their associated bartonellae. While bartonella diversification is associated with host sympatry, the influence of this factor is minor compared to the influence of codivergence and there is a clear indication that some bartonella lineages span multiple regions, particularly between Africa and Southeast Asia. Divergent adaptation of bartonellae to bat hosts and arthropod vectors is apparent and can dilute the overall pattern of codivergence, however its importance in the formation of Bartonella lineages in bats is small relative to codivergence. We argue that exploring all three of these processes yields a more complete understanding of bat-bartonella relationships and the evolution of the genus Bartonella, generally. Application of these methods to other infectious bacteria and viruses could uncover common processes that lead to parasite diversification and the formation of host-parasite relationships.

Keywords: Bartonella; Bats; Cophylogeny; Host-parasite relationships; Parasite diversification; Phylogeography.

Fig. 1

Geographic distributions of bat species represented in the study. Darker green areas show high levels of range overlap among sampled species, particularly within Central America, South America, and the Caribbean (a), and Europe, Africa, Central and East Asia, and Southeast Asia (b).

Fig. 2

Bayesian phylogeny of Bartonella genotypes reconstructing bat host suborders, shown by colored branches. Posterior probabilities for nodes are shown as circles (●) scaled by size from 0 to 1 (Posterior.prob) and colored by the support for the bat host suborder at that node (Suborder.prob). Mean tree likelihood = −9981.92, ESS = 2713; mean suborder tree likelihood = −18.95, ESS = 1785. Details on tip labels for Bartonella genotypes and associated host species are listed in Table S1 and S2.

Fig. 3

Bayesian phylogeny of Bartonella genotypes reconstructing bat host geographic regions, shown by colored branches. Posterior probabilities for nodes are shown as circles (●) scaled by size from 0 to 1 (Posterior.prob) and colored by the support for the bat host geographic region at that node (Region.prob). Mean tree likelihood = −9981.92, ESS = 2713; mean region tree likelihood = −95.84, ESS = 660. Details on tip labels for Bartonella genotypes and associated host species are listed in Table S1 and S2.

Fig. 4

Bayesian phylogeny of Bartonella genotypes reconstructing bat host or arthropod vector associations, shown by colored branches. Posterior probabilities for nodes are shown as circles (●) scaled by size from 0 to 1 (Posterior.prob) and colored by the support for the bat host geographic region at that node (Vector.prob). Mean tree likelihood = −9981.92, ESS = 2713; mean vector tree likelihood = −131.17, ESS = 5741. Details on tip labels for Bartonella genotypes and associated host species are listed in Table S1 and S2.