Summary:
In this paper the authors tackle the question of which host variables (phylogenetic, seasonal, or host-pathogen-specific) affect parasite prevalence and specialization in various species of bird.
Overview:
This study used an impressive number of individuals from over a nine year period to address an interesting question that can have implications not only in ecology but also in human health and how it will interact with climate change. However, some of the participants found the narrative a bit confusing and thought a clearer description of the objectives in the introduction would be helpful. Additional clarification was also requested in the methods. In particular, the molecular methods were not clear particularly on how new lineages were determined with the PCR approach and how the authors dealt with co-infections.
Major point:
- One of the main questions that was raised during the discussion was how the 5 new parasite lineages were defined. The manuscript would benefit from more justification for the molecular approaches used to identify and define these lineages. For the PCR and sequencing for example, it was not clear why a single nucleotide difference equates to a new lineage. PCR amplification can cause single nucleotide changes and also this lineage identification is based on a single gene. Even if cytochrome b is conserved enough to allow this inference, single nucleotide changes could be a PCR artifact. Further discussion around these points would be significantly improve the manuscript.
Minor points:
- Table 3 was identified as confusing by a number of participants who also suggested that perhaps a more detailed caption could alleviate this. Also, the authors should expand on what it means to be rescaled, and what the biological meaning is.
- It would be helpful to include the phylogenetic trees (even in the supplemental) or combined with figure 1
- For figure 1, in addition to the above suggestion, it would be useful to include (n=) next to host species along x axis, and add "Parasite" to the "lineage" legend
- It would be interesting to see an additional figure that shows a plot across time: how prevalence changed over the 9 years of the study (even average prevalence)
- ggplot palates are not colour blind friendly and suggest using shapes or a colour blind friendly palate like https://www.nature.com/articles/nmeth.1618
- It would be helpful to mention how the authors accounted for potential co-infections. This is something that can be pretty common to be infected by more than one lineage, which may complicate the analyses. The authors should comment on this in the discussion, if not elsewhere
Typos: