Information on hidden birth events restores identifiability in phylodynamic inference
Tobias Dieselhorst, Tanja Stadler
TLDR
This paper shows that information on hidden birth events, especially mutations at birth, restores parameter identifiability in phylodynamic inference.
Key contributions
- Identifiability of time-dependent birth-death models is restored with hidden birth event data.
- This holds for both single-point and time-dependent sampling strategies.
- Proves that mutations occurring at birth provide the necessary hidden birth event information.
- Phylodynamic inference becomes fully identifiable when mutations accumulate at birth.
Why it matters
This paper solves a fundamental non-identifiability problem in phylodynamic inference. By showing that mutations at birth provide crucial information, it makes complex evolutionary models fully identifiable. This significantly improves the reliability and scope of phylodynamic studies.
Original Abstract
The parameters of many classes of birth-death processes cannot be inferred uniquely from phylogenetic trees: infinitely many parameter combinations yield the same distribution of phylogenetic trees. Here, we show that parameter identifiability can be recovered even for the most general cases of time-dependent rates when additional information on hidden birth events along branches of the reconstructed tree is available. This holds both for models in which individuals are sampled at a single point in time or through time at a time-dependent rate. Moreover, we prove that when mutations occur at birth - assuming two different models for the accumulation of mutations at a birth event - then information about hidden birth events is available in the sequences and thus all parameters of time-dependent birth-death models become identifiable. Thus, phylodynamic inference is identifiable whenever evolutionary models with mutation accumulation at birth (such as at speciation, transmission, or cell division) are plausible.
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