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A Comparison of Pollinator Landings on Lantana camara with Three Other Plant Species in Bloom at Forest Trails, Karnataka, India. Melissa Forester June 2010 Abstract Pollinators have preferences in their selection of plant species on which to feed. Lantana camara is an invasive plant that is decreasing plant biodiversity across India. How will this affect pollinators who feed on the plants that are giving way to Lantana camara? This study seeks to learn about the relationship between plants and their pollinators. This study counts the landings of butterflies, bees, and other pollinators on Lantana camara and three other plant species in bloom at Forest Trails, Karnataka: milkweed (Calitropis giganteum), touch-me-not (Mimosa pudica,) and periwinkle (Catharanthus roseus). The number of available inflorescences is determined for each plant and the number of landings recorded. The data shows that while Lantana camara had a greater percentage of landing sites, it received a smaller percentage of the landings than did Calitropis giganteum or Mimosa pudica. More interesting, the study showed that most pollinators were host species specific. Introduction Butterflies do not feed indiscriminately from any flowers that they may find; they have preferences for nectar with regard to its chemical composition, corolla tube length and height of flower (Gadgil in Kunte 2000). When butterflies (and other pollinators) feed from a flower they help in the pollination of that plant species (Gadgil in Kunte, 2000). Lantana camara is one of the ten worst invasive weeds in the world and is decreasing the biodiversity of plant species in one of the planet’s biodiversity hot spots - the Western Ghats (Dr. Arvind, pers. com 2010). This study was conducted at Forest Trails, which borders Bannerghatta National Park in Karnataka, India, where plant diversity is giving way to encroaching Lantana camara. What will happen to other organisms that live in these forests as the plant species composition changes? To understand how pollinator species may be affected by changing plant species composition, there first must be knowledge about local plant-pollinator relationships. This study is an attempt to get to know the local plant-pollinator relationships. This study compares pollinator landings on Lantana camara with three other local plant species: milkweed (Calitropis giganteum), touch-me-not (Mimosa pudica,) and periwinkle (Catharanthus roseus). It is expected that different species of pollinators will not indiscriminately land on different plant species, but will select one species more often than others. Inspired by work the Ashoka Trust for Research for Ecology and the Environment (ATREE) has done involving high school students with data collection about local bird populations, this study was created with the intention of conducting a research project that could be replicated with students in a 9th grade biology class in the US, involving them in meaningful data collection that develops a body of local ecological knowledge. Methods An individual blooming plant of Lantana camara, milkweed (Calitropis giganteum), touchme-not (Mimosa pudica,) and periwinkle (Catharanthus roseus) was selected for observation, based on their proximity to a Lantana camara plant of similar height. This allowed each of the three plant species to be observed simultaneously with a Lantana camara plant and minimized other variables that could affect number of landings recorded, (such as time of observation). The observer sat at an equal distance from each plant. Three periods of observations were conducted of one hour each. Pollinator landings on L. camara and M. pudica were recorded for one hour at a location with GPS coordinates N 12’ 43.082’ E 077’ 33.625’. Pollinator landings on L. camara and C. roseus were recorded at the same location for one hour. The third observation recorded pollinator landings on L. camara and C. giganteum at a location with GPS coordinates N 12’ 43.082’ E 077’ 33.483’. Thus in total the Lantana plant was observed thrice (one hour each) while each of the others were only observed once (one hour). Each inflorescence in view of observer was counted as an available landing site. The total number of landing sites per plant was recorded. The number of landings that occurred on each plant was recorded. A landing was counted if either a butterfly stopped on an inflorescence or another pollinator touched it. For examples, bees were never observed to land on a plant but would visit a flower by touching it with their proboscis. For each plant, the number of landings is divided by the number of available landing sites. The quotient gives us the number of pollinator landings per available site. Results/Analysis As shown in Appendix 1, 110 pollinator landings were recorded. Each plant observed received a visit from a pollinator. Calitropis giganteum had 16 landing sites, Mimosa pudica 7, Catharanthus roseus 5, and L. camara 72 landing sites. The total number of landing sites for the study was 100 (that number is based on the total number of landing sites in view of observer and not intentional). Figure 1 shows that six different species of pollinators were recorded landing on the plants being observed. The chart shows that each pollinator visited only one of the four plants. A tiny bee visited Catharanthus roseus. A small bee visited Mimosa Pudica. A large bee visited Calitropus giganteum. Only Lantana camara received landings by more than one species of pollinator: Blue Tiger (Tirumala limniace) and Common Rose (Pachliopta aristolochiae) butterflies and a third pollinator which is referred to as “Hummingbird Bee” in this study. Figure 1 Number of Landings 66 64 62 60 58 56 54 52 50 48 46 44 42 40 38 36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 Available Landing Sites Tirumala limniace (3) Pachliopta aristolochiae (2) Hummingbird Bee (52) Large Bee (34) Small Bee (17) Tiny Bee (2) Catharanthus roseus Calitropis giganteum Mimosa pudica 5 7 Lantana camara 57 Key Blue Tiger Butterfly (Tirumala limniace) Common Rose Butterfly (Pachliopta aristolochiae) Hummingbird Bee Large Bee Small Bee Tiny Bee Figure 1 shows a direct relationship between the number of available inflorescences and the number of pollinator landings. 72 Table 1 is a comparison of the number of pollinator landings per plant between the four plant species in observation. Calitropis giganteum received 2.13 landings for every landing site. Mimosa pudica received 2.43 pollinator landings for every available site. Both plants were favored by pollinator visits over Lantana camara, which received less than one visit for each of its landing sites at .79 visits per site. Catharanthus roseus received the least visits per site at only .4 visits for each available landing site. Table 1 Proportion of Plant Species Landings Received Per Available Site 2.13 Calitropis giganteum 2.43 Mimosa pudica 0.4 Catharanthus roseus 0.79 Lantana camara Table 1: A comparison between four plant species, in bloom at Forest Trails, Karnataka, of the number of pollinator visits received per inflorescence. Table 2 shows that while Lantana camara had 57% of the available landing sites, it only received 52% of the landings in the study. In comparison Calitropis giganteum had only 16% of the available landing sites and received 31% of the landings. Similarly Mimosa pudica had 7% of the available sites and received 15% of the landings. The percentage of landings on both Calitropis giganteum and Mimosa pudica were about double the percentage of available sites. Both Catharanthus roseus and Lantana camara had landing percentages that were less than the percentage of available sites. The data from this study suggest that pollinators are showing some preferential landing on Calitropis giganteum and Mimosa pudica compared to Catharanthus roseus and Lantana camara. Table 2 Available Landings Plant Species Landing Sites Received 16% 31% Calitropis giganteum 7% 15% Mimosa pudica 5% 2% Catharanthus roseus 57% 52% Lantana camara Table 2: A comparison between four plant species in bloom at Forest Trails, Karnataka, of the percentage of the study's available landing sites and the percentage of pollinator landings observed. Conclusion There is difficulty in quantifying pollinator preferences for different plant species. In this study the quantification of landing sites was problematic. A “landing site” was defined as an inflorescence in view of the observer. Lantana camara, Calitropis giganteum, and Mimosa pudica each have inflorescence of multiple flowers while the inflorescence of Catharanthus roseus consists of a single flower. Pollinators may visit any inflorescence multiple times because there are multiple flowers. It makes sense for future studies to count landings per individual flower rather than by inflorescence. This will be more time consuming and require a lengthier study but should offer more meaningful data. It should also be taken into consideration that a pollinator may need to make more frequent landings to small flowers (such as Lantana camera) than to larger flowers (such as Calitropis giganteum) in order to get the same amount of food. Length of time for landings could be included as a measurement in future studies. It was interesting to discover along the way a correlation between the size of the bee and the size of the flower it visited. In this study, a large bee visited the largest inflorescence being observed, Calitropis giganteum, and a tiny bee visited Catharanthus roseus. Perhaps this could be the subject a future study in a high school biology class. A study similar to this one would be useful in a high school biology classroom because it offered an opportunity to learn about pollinator-plant relationships and the scientific method through the process. Students could collect data about which plants pollinators land on in their local communities in order to develop understanding of local ecological relationships. Works Cited Arvind N.A. (Personal Communication) 2010, ATREE, Bangalore. Kunte, Krushnamegh. India a Lifescape: Butterflies of Peninsular India. University 2000. Press,