Conclusions
The total number of species recorded in our ploidy database is probably
close to the total for which ploidy has so-far been assessed in
macrophyte species. This ploidy database provides a useful resource to
support further studies about the effects of varying environmental
conditions on ploidy state in aquatic plants, at both regional and local
scales, particularly in the context of scenarios of future climate
change which suggest increased temperature and drought worldwide.
The findings of our study, utilising this database, improve knowledge of
patterns of global distribution and diversity relating to ploidy state
within a group of freshwater organisms, namely aquatic macrophytes,
which both occur widely across the planet and are inherently adapted to
a substantially-varied set of environmental stress conditions worldwide.
The study also provides new information about drivers of ploidy at
global-scale for this group of plants, including the use of plant
assemblage diversity parameters to predict ploidy. In particular, our
results provide evidence that climatic factors, especially temperature
and evapotranspiration, play a strong role in driving distributions of
macrophyte ploidy state, across the planet. Overall, our data strongly
support the assertion that increased chromosome number may be an
adaptation assisting vascular plant survival in a range of harsh
environmental conditions, especially those typifying
environmentally-stressed high latitudes.