The Pleurothallis crateriformis complex (Orchidaceae): undescribed diversity and pollination biology of a newly recognized species group from Ecuador and Peru

A new complex of species is recognized within Pleurothallis subgenus Pleurothallis section Macrophyllae-Fasciculatae, comprising P. crateriformis, P. equipedites, P. nipterophylla, P. phymatodea and P. pyelophera, as well as two new species. Pleurothallis monteroae sp. nov. and Pleurothallis austrorientalis sp. nov. from southeastern Ecuador are described and illustrated, bringing the number of described species in the complex to seven.

Localities in southeastern Ecuador are confirmed for P. pyelophera and P. equipedites, species originally described from cultivated material lacking precise collection data. Diagnostic characters distinguishing the two new species from their most morphologically similar congeners, as well as from the other five members of the complex, are presented. Summarizing the traits characteristic of the group allowed recognition of eight additional undescribed species, mostly from Peru.

Unusual characteristics of the P. crateriformis complex include a deeply “ crateriform ” lip containing a nectar-like liquid, non-resupinate flowers, and extra-labellar nectar-like liquid. These attributes suggest a different pollination mechanism within P. sect. Macrophyllae-Fasciculatae, involving a shift from nototribic to sternotribic pollination.

A possible case of morphological convergent evolution between the P. crateriformis complex and a group of non-resupinate Pleurothallis species from Mesoamerica is discussed.