Untangling the coevolutionary history between doves and their parasitic lice

Parasites;Phylogenetics;Cophylogenetics;Population Genetics

Sweet, Andrew Donald

关键词: Parasites;    Phylogenetics;    Cophylogenetics;    Population Genetics;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/100942/SWEET-DISSERTATION-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In host-parasite systems, any given host species can be associated with multiple types of parasites, each of which can have a unique ecological relationship with the host. However, it remains unclear how these ecological differences link to evolutionary patterns. What shapes the dynamics of a host-parasite interaction over evolutionary time? An ideal approach for addressing this question is to compare multiple lineages of similar parasites that are associated with the same group of hosts but have distinct ecological differences – or “ecological replicates.” For my dissertation, I applied this strategy by focusing on the wing and body lice of doves. These two “ecomorphs” of lice are not closely related yet exclusively parasitize the same group of hosts. Notably, wing lice have a greater capability for dispersal than body lice. Dispersal is an important ecological component of host-parasite interactions and speciation in general.The first part of my dissertation examined broad cophylogenetic patterns across the dove-louse system. I found that wing and body lice did not have correlated patterns, and body lice showed more cospeciation with their hosts. This pattern agreed with previous studies, the results of which suggested that the increased cospeciation in body lice was due to differences in dispersal ability. In contrast with previous work, I also found that both wing and body louse phylogenies are statistically congruent with the host phylogeny. However, the previous studies had limited taxon sampling compared to my study, indicating that taxon sampling can have a significant impact on the results of cophylogenetic comparisons, and that there can be variable cophylogenetic patterns within a host-parasite system. Cophylogenetic variation in dove lice was further highlighted by my study on lice from phabine doves, a clade native to Australia and Southeast Asia. In this system, wing lice have higher levels of cospeciation with their hosts than did body lice, which is the opposite pattern found in other dove louse systems.The second part of my dissertation focused on the wing and body lice of New World ground-doves. All three groups (wing lice, body lice, and doves) are monophyletic and have relatively few species, which makes the system ideal for obtaining a comprehensive taxonomic sample. As a group that straddles the population-species boundary, ground-dove lice are also useful for gaining insight into host-parasite evolution at phylogenetic and population scales. I used Sanger or whole-genome sequencing data to estimate phylogenetic and/or population patterns of the ground-dove hosts and both groups of lice. For the louse genomes, I developed a novel pipeline to assemble nuclear genes for phylogenetic analysis and call SNPs for population analysis. My results indicate that dispersal is a key factor in shaping the evolution of this host-parasite system. Body lice had higher levels of cospeciation with their hosts, were more host-specific, and had higher rates of divergence than wing lice. At the population level, some body lice also showed host-specific structure, whereas wing lice did not. Body lice also had lower levels of heterozygosity than wing lice, suggesting higher levels of inbreeding. However, dispersal is likely not the only factor that shapes this host-parasite system. Host phylogeny appears to have a significant effect as well. Both wing and body louse phylogenies were statistically congruent with the host phylogeny, and the congruence metrics for individual associations were correlated between the two types of lice. Biogeography may also dictate host-parasite interactions. The wing louse phylogeny was significantly structured according to biogeographic region, and both wing and body lice also showed some biogeographic structure at the population level. Together, these results show that host-parasite interactions can be dictated by many ecological factors over evolutionary time, even in the presence of a primary, dominant factor (e.g., parasite dispersal).