Data from: Preponderance of clonality triggers loss of sex in Bulbophyllum bicolor, an obligately outcrossing epiphytic orchid

Vegetative propagation (clonal growth) conveys several evolutionary
advantages that positively affect life history fitness and is a widespread
phenomenon among angiosperms that also reproduce sexually. However, a bias
towards clonality can interfere with sexual reproduction and lead to
sexual extinction, although a dearth of effective genetic tools and
mathematical models for clonal plants has hampered assessment of these
impacts. Using the endangered tropical epiphytic or lithophytic orchid
Bulbophyllum bicolor as a model, we integrated an examination of breeding
system with 12 microsatellite loci and models valid for clonal species to
test for the ‘loss of sex’ and infer likely consequences for long-term
reproductive dynamics. Bagging experiments and field observations revealed
B. bicolor to be self-incompatible and pollinator-dependent, with an
absence of fruit-set over four years. Challenging the assumptions that
clonal populations can be as genotypically diverse as sexually reproducing
ones and that clonality does not greatly influence genetic structure, just
22 multilocus genotypes were confirmed among all 15 extant natural
populations, 12 of the populations were found to be monoclonal and all
three multiclonal ones exhibited a distinct phalanx clonal architecture.
Our results suggest that all B. bicolor populations depend overwhelmingly
on clonal growth for persistence, with a concomitant loss of sex due to an
absence of pollinators and a lack of mating opportunities at virtually all
sites, both of which are further entrenched by habitat fragmentation. Such
cryptic life history impacts, potentially contributing to extinction debt,
could be widespread among similarly fragmented, outcrossing tropical
epiphytes, demanding urgent conservation attention.