Reproductive biology and isolation mechanisms in rupicolous species of the Acianthera prolifera complex (Orchidaceae) occurring in southeastern Brazil

Caught in the act: pollination of sexually deceptive trap-flowers by fungus gnats in Pterostylis (Orchidaceae)

“…While most sexual deceptive pollination systems involve Hymenoptera (Schiestl, 2005), there are many orchid genera pollinated by Diptera that may harbour such systems. For example, in the Pleurothallidinae, which contains over 4100 species, almost all records of pollination concern Diptera, but the mechanism of pollinator attraction has been resolved in only a handful of species (Pridgeon, 2005; but see Borba and Semir, 2001; Barbosa et al, 2009;Melo et al, 2011). Until now, the only well documented cases of pollination by sexual deception of Diptera in the Orchidaceae are in the large neotropical orchid genus Lepanthes (.700 species; Blanco and Barboza, 2005).…”

Two Self-Incompatibility Sites Occur Simultaneously in the Same Acianthera Species (Orchidaceae, Pleurothallidinae)

“…The presence of self-incompatibility in Orchidaceae, which is a family that is predominantly self-compatible, is mostly restricted to a few groups, such as species of Dendrobium C. Agardh [ 6 ], Oncidiinae [ 7 ], and Pleurothallidinae [ 8 ]. Since SI has not been genetically characterized in these groups, morphological aspects and the development of pollen grains and pollen tubes have been used to infer the type of SI in Pleurothallidinae [ 8 , 9 , 10 , 11 , 12 ]. Species of Pleurothallidinae (ca.…”

“…Species of Pleurothallidinae (ca. 4.100 species) are predominantly fly pollinated [ 13 , 14 , 15 ] since most of the species studied showed some degree of self-incompatibility [ 8 , 9 , 10 , 11 , 12 , 16 , 17 , 18 ]. In this subtribe, different sites of occurrence of self-incompatibility reactions were mentioned in other species such as, in the stigma, where pollen grains do not germinate (similar to that observed in SSI, [ 10 , 11 ]), the stylar canal, where pollen tube growth is interrupted in the column/style (similar to GSI, [ 8 , 9 ]), and in the ovary, where the pollen tubes are obstructed before the ovules are penetrated [ 9 , 17 ].…”

“…Some species of Acianthera Scheidw. (Pleurothallidinae) are partially self-incompatible, resulting in a low fruit set incidence (10–13%) after self-pollination [ 8 , 9 , 12 ]. These fruits from self-pollination have high levels (ca.…”

“…These fruits from self-pollination have high levels (ca. 80%) of seeds without the embryo, presenting only the seed coat or dead embryonic tissue [ 8 , 9 , 12 ]. Commonly, the high number of seeds without the embryo in fruits resulting from self-pollination has been explained as a possible consequence of inbreeding depression [ 8 , 9 , 19 , 20 ], which causes the death of zygotes and embryos [ 21 , 22 ].…”