A global analysis of mosses reveals low phylogenetic endemism and highlights the importance of long-distance dispersal

Aim: Digitization of herbarium specimens and DNA sequencing
efforts in the past decade have enabled integrative analyses of patterns
of diversity and endemism in a phylogenetic context. Here, we compare the
best available floristic databases to a comprehensive specimen database to
examine spatial patterns of moss phylogenetic assembly. We test the
hypotheses that 1) mosses exhibit phylogenetic regionalization, 2) islands
contain significantly high phylogenetic diversity, and 3) that moss
phylogenetic endemism is low on a global scale. Location: Global
Taxon: Mosses Methods: We developed a phylogeny of 3,654
moss species using 25 markers and compiled a global specimen database from
online repositories. We calculated floristic and phylogenetic measures of
diversity and endemism and performed randomizations to test for
significant deviations from expectations. We use rarefaction and
extrapolation to alleviate substantial differences in sampling effort
across the globe. We used both phylogenetic and floristic methods to test
for spatial regionalization. We compare our specimen-based results to
those obtained using a floristic dataset. 
Results: Phylogenetic diversity is more robust to missing data
than species richness. Mean phylogenetic distance was significantly higher
than expected in areas with high species richness, indicating that
reported richness in these areas is likely a product of repeated
colonization. Phylogenetic endemism is low globally. Phylogenetic
regionalizations cluster into a Holarctic/Holantarctic temperate region, a
pantropical region, and a region composed of Australia, New Zealand, and
South Africa. Main Conclusions: Future efforts for collecting,
sequencing, and databasing moss species should focus on the tropics,
particularly Africa and Southeast Asia. We provide further evidence to
support several important theories developed in moss biogeography,
including the role of long-distance dispersal in shaping floristic
patterns, the dominance of anagenesis in driving patterns of island
diversity, and the role of climatic instability in driving patterns of
assembly in the Holarctic.