This project studies plants with foul-smelling red flowers that bloom in early spring in the southeastern U.S.A. These plants are intriguing because they appear to be sending the same floral message to pollinators. This looks like a floral syndrome (where unrelated plants converge on a common appearance or odor to lure the same, specific pollinators) BUT something is amiss: these flowers attract as pollinators a guild of generalized insects that feed on decaying organic matter. Documenting blooming patterns, visitors, and floral characteristics in populations across three southeastern states will characterize this apparent syndrome. This project impacts undergraduates who will perform all stages of science for academic credit. Students will read relevant literature and design experiments, set out field plots, collect and analyze their data. The following spring, students will present their results at the Association for Southeastern Biologists? annual meeting and submit them for publication. This project initiates the Wine Guild Curriculum Partnership with the GSU Botanical Garden that will impact several thousand K-12 school children and their teachers. This outdoor curriculum provides hands-on experience with pollination biology. The children will run essentially the same experiments at the Botanical Garden that investigators run in the field, providing first-hand experience with the scientific process and a greater appreciation for this rich floral heritage.
This research was conducted to determine if flower color and odor makes a difference in the pollination and fruit production of 2 species of Trillium (red and white). The studies were conducted by graduate student Ha N. Nguyen (Antioch University) under the direction of Dr. Michelle Zjhra (Georgia University) (year 1), and Dr. Peter A. Palmiotto (Antioch University) (year 1-4), in collaboration with Dr. Robert Raguso (Cornell University), Dr. Amy Boyd (Warren Wilson College). All field work was completed over 3 spring seasons from 2009 to 2011 in Bat Cave Preserve North Carolina. Phenology: We set out to determine if plant emergence, flowering and fruiting (phenology) was affected by the amount of sunlight in the early spring just before the leaves come out. We examined the hypothesis that the red trillium (Trillium cuneatum) emerges before canopy closure while the white trillium (Trillium rugelii) emerges after sunlight levels dropped due to canopy closure. Result: Flowering of red trillium and white trillium commenced from March to late April each year. White trillium’s peak flowering was 7 to 10 days later than red trillium. Although bud initiation varied from year to year by a few days there was a consistent three week difference between bud emergence of red trillium compared to white trillium. Relevance: Over three years of observations, red trillium showed evidence of depending on climate clues to start its flowering season. Trillium’s first spotted bud dates were March 8, March 1, and February 20th, from 2009 to 2011. Variable weather in those years explains why we saw changes. Pollination: Experiments were conducted to investigate who the insect pollinators were and which cues played a role in attracting insects. Specifically we set out to determine if trillium color or odor plays a greater role in pollinator attraction using natural and artificial trapping experiments. Results: The total number of insects collected from all traps was 947 in 2009, 1874 in 2010 and 2477 in 2011. Flies, beetles and wasps comprised the majority of these samples. Spiders were found nesting inside red trillium’s flowers throughout the flowering season. Flies (Diptera) were the most abundance comparing to other insect groups regardless of treatments and years. Insect surveys from 2009 to 2011 revealed the insects visited when pollen was being shed and when the female flower was receptive. There were few insect visitors, except spiders coming to opening flowers. Click beetle (Elateridae), Curculionidae, Carabidae beetles and spiders were the most frequent visitors. Click beetles were often covered with red trillium pollen and moved extremely slowly between flowers (>30 minutes). Relevance: Even though red trillium and white trillium had overlapping flowering time, they were visited by non-overlapping visitors/pollinators. There was generally low pollinator visitation rate to these flowers. Insects were attracted to flower scent and the combination of odor and color cues more than control and scent only. The results suggest that odor plays an important role in attracting pollinators over visual cues. There is also a possibility that only one or two types of insects are the real pollinators of these plants; perhaps it is the click beetle. Breeding systems: To understand how red trillium and white trillium reproduce we followed self- and hand cross-pollinated individuals. We looked to characterize their reproduction strategies, and how they might relate to color or scent and phenology (flowering time). Results: The red flowered and white trillium showed a significant difference in fruit and seed production during the two years of the pollination experiments. There were few pollinated red flowers and fewer successful mature fruit set during and post-flowering (i.e. two fruits in 2009, three in 2010 and one in 2011 were found among over 3000 individuals outside of the study plot). Notably in the three treatments during the two years of study the red flowered Trillium yielded no mature fruit. Unlike red trillium which had no mature fruit set, 15% of the white trillium experimental plants set fruits in 2010 and 12% set fruits in 2011. In 2010 and 2011, cross pollinated plants produced more mature fruits than self-pollinated and control plants. In 2010, 35% of hand cross-pollinated white trillium produced successful fruits. In 2011, 60% of hand cross-pollinated white trillium produced mature fruits. Overall, cross-pollinated plants were more successful in fruit set ratio than control and self-pollinated plants. A high percentage, (65% in 2010 and 96% in 2011), of white trillium initiated fruit in the hand cross-pollinated treatment while about half of those were collected as mature fruits. A similar fruit set pattern in the hand cross-pollination treatment was observed in both years. Relevance: The results from hand cross-pollination treatment on both red and white trillium suggest that they cannot pollinate themselves. In sum, these plants are not very successful in reproducing by sexual reproduction which raises concerns about their ability to adapt to our changing climate.
