Abstract Detail

Reproductive Processes

Felton, Josh [1], Heschel, M. Shane [2], Jabaily, Rachel [3].

Comparative Reproductive Biology of Two Self-Compatible Bromeliaceae.

Bromeliaceae is a species rich and ecologically diverse Neotropical plant family that uses a variety of pollinators and dispersers. Greenhouse-based comparative experiments are rare in Bromeliaceae, particularly about reproductive biology. This study seeks to describe the difference in reproductive development, investment, and outcome between Vriesea rafaelii Leme and Billbergia brasiliensis L.B.Sm through pollination manipulation experiments. The focal species are both epiphytes capable of selfing and outcrossing, each producing a showy inflorescence seemingly adapted for different pollinators and seed dispersers. Billbergia brasiliensis is typical of subfamily Bromelioideae by being adapted to hummingbird pollinators and frugivores, producing colorful fleshy fruit. Vriesea rafaelii is typical of subfamily Tillandsioideae and particularly the subtribe Vrieseinae by being adapted to bat pollination and having capsular fruits and seeds with extensive plumose appendages for wind dispersal. We wanted to investigate how the different pollination syndromes and fruit types influenced reproductive effort (the proportion of biomass invested by a plant towards structures for sexual reproduction compared to vegetative structures) and if outcrossed flowers invested more biomass into the maturing fruit and yielded higher seed mass than selfed flowers. First, inflorescences were observed to discern the developmental timing and cues necessary to emasculate the flowers before anthers dehisce and pollen grains become visible. Populations of both study species were then divided into selfed and outcrossed groups. Outcrossing and nectar concentration data was taken on Vriesea rafaelii, which typically opened one flower at dusk with stigma and anthers in proximity, though occasional herkogamous morphology was noted. Outcrossing for Billbergia brasiliensis happened at dawn, which opened many flowers per day with no variation in floral morphology noted. After ~3-5 months of development time, the entire inflorescence structure was harvested, and individual fruits were dissected, with carpel mass and seed mass dried separately. A nested ANOVA was performed to determine if outcrossing or selfing affected seed and fruit mass for both study species. One-way ANOVAs of carpel mass ratios (carpel to inflorescence, seed and vegetative mass) were conducted to discern if either species allocates more energy towards attracting pollinators and dispersers. We found Vriesea rafaelii individuals allocated significantly more biomass towards inflorescence and carpel mass compared to vegetative mass than Billbergia brasiliensis. Carpel mass and total seed mass were higher in outcrossed flowers than selfed flowers of B. brasiliensis. A similar but non-significant trend was found in V. rafaelii. Lower seed mass in selfed flowers suggests that inbreeding depression is occurring in both species. Demonstration of inbreeding depressing in seed-grown bromeliads maintained in greenhouse conditions minimizing environmental variation is novel. Both species are endemic to the Brazilian Atlantic Forest, a global hotspot of biodiversity (particularly for bromeliads) that has been severely diminished and fragmented. Conservation efforts should focus on maintaining contiguous plant populations and healthy pollinator and frugivore communities to promote outcrossing. Additional plants of both species are fully developing fruits and seeds, allowing future comparative studies of fitness components.

1 - Colorado College, Organismal Biology and Ecology, 14 East Cache la Poudre St., Colorado Springs, Colorado, 80903, USA
2 - Colorado College, Organismal Biology, 14 E. Cache La Poudre St., Colorado Springs, CO, 80903, United States
3 - Colorado College, Organismal Biology & Ecology, 14 E Cache La Poudre St, Colorado Springs, CO, 80903, United States

Keywords:
Bromeliaceae
Neotropics
epiphyte
reproductive biology
selfing
Pollination.

Presentation Type: Oral Paper
Number: RP2004
Abstract ID:113
Candidate for Awards:None