Data from: Pollinator-mediated isolation promotes coexistence of closely related food-deceptive orchids

Identifying the factors that contribute to reproductive isolation among
closely-related species is key for understanding the diversification of
lineages. In this study, we investigate the strength of premating and
postmating reproductive isolation barriers between Disa ferruginea and
Disa gladioliflora, a pair of closely-related species, often found
co-flowering in sympatry. Both species are non-rewarding and rely on
mimicry of different rewarding model flowers for attraction of
pollinators. We constructed abiotic niche models for different forms of
each taxon to measure ecogeographic isolation. Using experimental arrays
in sympatry, we recorded pollinator transitions to measure ethological
isolation. We performed hand pollinations to measure postpollination
isolation. We found strong, but not complete, premating isolation
associated with abiotic niches and absolute ethological isolation based on
pollinator preferences in sympatry. Pollinator preferences among the
orchids could be explained largely by flower colour (orange in D.
ferruginea and pink in D. gladioliflora) which matches that of the
pollinator food plants. Post-mating barriers were weak as the species were
found to be inter-fertile. Coexistence in the orchid species pair is due
mainly to ethological reproductive isolation arising from flower colour
differences resulting from mimicry of different rewarding plants. These
results highlight the importance of signalling traits for ethological
isolation of closely-related species with specialized pollination systems.