Co-phylogeography and morphological evolution of sika deer lice (Damalinia sika) with their hosts (Cervus nippon)

Integrative taxonomic description of the chewing louse Tricholipeurus lipeuroides infesting Odocoileus virginianus veraecrucis white-tailed deer in Veracruz, Mexico

Chewing lice (Phthiraptera: Amblycera, Ischnocera) represent a component of the ectoparasite fauna associated with large sized mammals as deers. However, the diversity of chewing louse species infesting deer remains to be fully characterized in the Neotropics. Little is known about the chewing lice infesting the extant fourteen subspecies of white-tailed deer (Odocoileus virginianus) in Mexico. Known to infest white-tailed deer (WTD) in Canada and the United States (U.S.), Tricholipeurus lipeuroides is a chewing louse species that was originally described in the nineteenth century infesting O. v. mexicanus in Mexico. For the first time, infestation of O. v. veraecrucis, a Neotropical WTD subspecies in Mexico, with T. lipeuroides is reported herein. An integrative taxonomic approach was taken by combining morphological and molecular analyses to describe the T. lipeuroides infestion of O. v. veraecrucis. Ecological parameters of the T. lipeuroides infestations were also calculated. The prevalence was 91.7% of the 56 O. v. veraecrucis (29 females and 27 males) inspected while under chemical restraint that were sampled at 3 sites in the central region of Veracruz state in Mexico. The amplification and sequencing of previously reported T. lipeuroides Cytochrome Oxidase Subunit I gene confirmed the identity of all the chewing louse life stages. These results are discussed in the context of comparative analyses on the emergence of novel chewing lice-deer associations.

Tree shape-based approaches for the comparative study of cophylogeny

Cophylogeny is the congruence of phylogenetic relationships between two different groups of organisms due to their long-term interaction. We investigated the use of tree shape distance measures to quantify the degree of cophylogeny. We implemented a reverse-time simulation model of pathogen phylogenies within a fixed host tree, given cospeciation probability, host switching, and pathogen speciation rates. We used this model to evaluate 18 distance measures between host and pathogen trees including two kernel distances that we developed for labeled and unlabeled trees, which use branch lengths and accommodate different size trees. Finally, we used these measures to revisit published cophylogenetic studies, where authors described the observed associations as representing a high or low degree of cophylogeny. Our simulations demonstrated that some measures are more informative than others with respect to specific coevolution parameters especially when these did not assume extreme values. For real datasets, trees' associations projection revealed clustering of high concordance studies suggesting that investigators are describing it in a consistent way. Our results support the hypothesis that measures can be useful for quantifying cophylogeny. This motivates their usage in the field of coevolution and supports the development of simulation-based methods, i.e., approximate Bayesian computation, to estimate the underlying coevolutionary parameters.

Phylogenetic framework for coevolutionary studies: a compass for exploring jungles of tangled trees

Phylogenetics is used to detect past evolutionary events, from how species originated to how their ecological interactions with other species arose, which can mirror cophylogenetic patterns. Cophylogenetic reconstructions uncover past ecological relationships between taxa through inferred coevolutionary events on trees, for example, codivergence, duplication, host-switching, and loss. These events can be detected by cophylogenetic analyses based on nodes and the length and branching pattern of the phylogenetic trees of symbiotic associations, for example, host-parasite. In the past 2 decades, algorithms have been developed for cophylogetenic analyses and implemented in different software, for example, statistical congruence index and event-based methods. Based on the combination of these approaches, it is possible to integrate temporal information into cophylogenetical inference, such as estimates of lineage divergence times between 2 taxa, for example, hosts and parasites. Additionally, the advances in phylogenetic biogeography applying methods based on parametric process models and combined Bayesian approaches, can be useful for interpreting coevolutionary histories in a scenario of biogeographical area connectivity through time. This article briefly reviews the basics of parasitology and provides an overview of software packages in cophylogenetic methods. Thus, the objective here is to present a phylogenetic framework for coevolutionary studies, with special emphasis on groups of parasitic organisms. Researchers wishing to undertake phylogeny-based coevolutionary studies can use this review as a "compass" when "walking" through jungles of tangled phylogenetic trees.

Characterisation of microsatellite loci in two species of lice, Polyplax serrata (Phthiraptera: Anoplura: Polyplacidae) and Myrsidea nesomimi (Phthiraptera: Amblycera: Menoponidae)

Polymorphic microsatellite loci were characterised for two louse species, the anopluran Polyplax serrata Burmeister, 1839, parasitising Eurasian field mice of the genus Apodemus Kaup, and the amblyceran Myrsidea nesomimi Palma et Price, 2010, found on mocking birds endemic to the Galápagos Islands. Evolutionary histories of the two parasites show complex patterns influenced both by their geographic distribution and through coevolution with their respective hosts, which renders them prospective evolutionary models. In P. serrata, 16 polymorphic loci were characterised and screened across 72 individuals from four European populations that belong to two sympatric mitochondrial lineages differing in their breadth of host-specificity. In M. nesomimi, 66 individuals from three island populations and two host species were genotyped for 15 polymorphic loci. The observed heterozygosity varied from 0.05 to 0.9 in P. serrata and from 0.0 to 0.96 in M. nesomimi. Deviations from the Hardy-Weinberg equilibrium were frequently observed in the populations of both parasites. Fst distances between tested populations correspond with previous phylogenetic data, suggesting the microsatellite loci are an informative resource for ecological and evolutionary studies of the two parasites.

Rates of genomic divergence in humans, chimpanzees and their lice

The rate of DNA mutation and divergence is highly variable across the tree of life. However, the reasons underlying this variation are not well understood. Comparing the rates of genetic changes between hosts and parasite lineages that diverged at the same time is one way to begin to understand differences in genetic mutation and substitution rates. Such studies have indicated that the rate of genetic divergence in parasites is often faster than that of their hosts when comparing single genes. However, the variation in this relative rate of molecular evolution across different genes in the genome is unknown. We compared the rate of DNA sequence divergence between humans, chimpanzees and their ectoparasitic lice for 1534 protein-coding genes across their genomes. The rate of DNA substitution in these orthologous genes was on average 14 times faster for lice than for humans and chimpanzees. In addition, these rates were positively correlated across genes. Because this correlation only occurred for substitutions that changed the amino acid, this pattern is probably produced by similar functional constraints across the same genes in humans, chimpanzees and their ectoparasites.