Aim: The lichenized fungus Pseudocyphellaria glabra has a disjunct distribution that is separated by the Tasman Sea and the Pacific Ocean. We collected samples from across its disjunct range to test whether major physical barriers resulted in genetic differentiation among populations. We tested two hypotheses (1) if large bodies of water isolate populations of P. glabra, then these populations will be genetically distinct, and (2) given the strong wind patterns in the southern hemisphere, P. glabra populations on different landmasses will be connected by frequent and ongoing long-distance dispersal (i.e. gene-flow). We predicted that the large distances between populations would generate genetically distinct clusters, but given the strong and sustained wind patterns present in the Southern Hemisphere and the microscopic size of P. glabra spores that migration is frequent enough to prevent speciation.
Location: Southeastern Australia, New Zealand, and Southern Chile
Methods: We used genomic data over 300 samples of P. glabra using restriction site-associated DNA sequencing to conduct phylogenomic and population genomic analyses.
Results: Maximum likelihood analysis recovers P. glabra as two distinct lineages that do not correspond to geography. Each of the major lineages contain individuals from all landmasses. Population genomic analyses identified four genetic clusters. Two clusters occur in New Zealand and both are found in Australia and Chile. The other two clusters contain only individuals from Chile and Australia that are isolated by the Tasman Sea and Pacific Oceans. Coancestry estimation analyses suggest that populations from New Zealand and Chile have higher levels of coancestry than both do with Australian populations.
Main conclusion: Populations from Australia, Chile, and New Zealand are genetically distinct, but frequent long-distance dispersal may sufficiently prevent speciation.
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