Abstract
Pitcairnioideae is the second most diverse subfamily of bromeliads (Bromeliaceae), a group exclusive to tropical regions of the New World. Pitcairnioid bromeliads have floral traits assumed to promote outcrossing through biotic pollination systems; however, the reproductive biology of most of the species of this group has not been documented. Pitcairnia heterophylla is an epiphytic (seldom saxicolous) bromeliad occurring from Southern Mexico, into the Northern Andes. We studied the pollination and breeding system of P. heterophylla in an epiphytic population at a mountain forest in Costa Rica from January to April 2013. We performed hand pollination experiments (agamospermy, autonomous self-pollination, hand self-pollination and hand cross-pollination) on 89 flowers from 23 individuals (3–6 flowers per individual) in 2013 flowering season. Nectar production was measured on 18 unvisited flowers of six individuals with a hand-held refractometer. Simultaneously, floral visitors were recorded on eight individuals with trail cameras for a total of 918 hours (115 ± 52 hours per individual, mean ± SE). Under natural conditions, seed set (540.4 ± 55.2) was similar to manually selfed flowers (516.3 ± 41.5) and autonomously selfed flowers (521.1 ± 29.0), but lower to manually outcrossed flowers (670.2 ± 31.3). The flowers of P. heterophylla are self-compatible, capable of autonomous pollination, and non-agamospermous. Intrafloral self-pollination is facilitated by adichogamy and lack of floral herkogamy. The scentless red flowers of P. heterophylla with tubular corollas and nectar production suggested ornithophilic pollination which was confirmed by video recording of 46 hummingbird visits. The most common floral visitor was the short-billed hummingbird Lampornis calolaemus which accounted for 78 % of the visits. However, the visitation rate during the flowering season was low (0.6 visits per day per plant). Selfing in P. heterophylla might be explained as a mechanism of reproductive assurance and to reduce interspecific pollen flow with taxonomically unrelated plants.
Highlights
The Bromeliaceae family is a highly diverse group of monocotyledonous plants exclusive to the Neotropics (Benzing, 2000) and, nearly 56 % (1 770 spp.) of their members inhabits the forest canopy as epiphytes (Zotz, 2013)
Bromeliads of sub-family Pitcairnioideae constitute the second most diverse group within the family (Smith & Downs, 1974) and has received less attention in studies of reproductive biology compared to subfamilies Tillandsioideae and Bromelioideae (Ramírez-Morillo, Chi-May, Carnevali & May-Pat, 2009; Matallana et al, 2010)
We examined the reproductive biology of a population of P. heterophylla in a Costa Rican mountain forest
Summary
The Bromeliaceae family is a highly diverse group of monocotyledonous plants exclusive to the Neotropics (Benzing, 2000) and, nearly 56 % (1 770 spp.) of their members inhabits the forest canopy as epiphytes (Zotz, 2013). The presence of reproductive traits that facilitate self-pollination among plants with bisexual flowers and specialized pollination systems may function as a mechanism of reproductive assurance (Fenster & Martén-Rodríguez, 2007) and facilitate the maintenance of a mixed mating system (Goodwillie, Kalisz, & Eckert, 2005). Understanding the evolution and maintenance of breeding systems in Pitcairnia requires further information on their reproductive biology and pollination systems, which at present are scarcely documented This information is essential to explain processes such as gene flow and genetic structuring in epiphytic plant populations (e.g., Cascante-Marín, Oostermeijer, Wolf, & Fuchs, 2014). Our research had the following objectives: 1) to describe the floral biology and nectar production, 2) to determine the plant’s breeding system using manual pollination treatments, and 3) to estimate pollinator visitation rates
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