The Andes of Colombia and Ecuador as a barrier to fern and lycophyte species from Mesoamerica

We compiled a list of the fern and lycophyte species that occur in
Mesoamerica and extend into Colombia and Ecuador where they are restricted
to the western side of the Andes; that is, they only occur west of the
crest of the easternmost cordillera and are absent from that cordillera’s
eastern slope and in adjacent Amazonia. We found 130 species with this
Mesoamerican and west-of-the-eastern-cordillera distribution. Those 130
species constitute 7% of the total 1805 fern and lycophyte species that
have been recorded west of the crest of the easternmost cordillera in
Colombia and Ecuador. All 130 species had elevation ranges with midpoints
lying in low (0–900 m) or middle (900–3000 m) elevations, and none were
above 3000 m. This suggests the cordilleras have acted as elevational
barriers. We also investigated the blockage of these 130 species by each
of the Andean cordilleras. We found that 74 (57%) of the 130 species were
limited eastward by the western cordillera, 15 (11%) by the central
cordillera (this cordillera in Colombia only), and 41 (32%) by the eastern
cordillera. If estimates of endemics to the western Andean region are
considered, then at least 20–22% of all fern and lycophyte species are
restricted west of the crest of the easternmost cordillera. Although
usually exhibiting larger geographic distributions compared to
angiosperms, fern and lycophyte species may show significant geographic
restriction by mountain ranges.