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Determination of the optimal pollinator of Stachytarpheta jamaicensis (Verbenaceae) based on nectar production throughou...

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Determination of the optimal pollinator of Stachytarpheta jamaicensis (Verbenaceae) based on nectar production throughout the day
Translated Title:
Determinación de los polinizadores óptimos de Stachytarpheta jamaicensis (Verbenaceae) basada en la producción de néctar durante el transcurso del día ( )
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English
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Siemek, Stephanie
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Pollination by insects   ( lcsh )
Pollination by animals   ( lcsh )
Verbenaceae--Costa Rica--Puntarenas--Cañitas   ( lcsh )
Polinizado por insectos
Polinizado por animales
Verbenaceae--Costa Rica--Puntarenas--Cañitas
Tropical Ecology 2006
Stachytarpheta jamaicensis
Ecología Tropical 2006
Stachytarpheta jamaicensis
Genre:
Reports   ( lcsh )
Reports

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Abstract:
Stachytarpheta jamaicensis has been found to have various visitors but its actual pollinator is unknown. I Collected nectar from 22 individual plants during various times of the day and I determined that S. jamaicensis produces most nectar during 6:00 am and 6:00 pm. Observation of the visitors were recorded for each hour and ten flowers were collected for each potential pollinator after they were observed obtaining nectar from the flowers. Nectar production was found to be significantly abundant early morning and late afternoon, this suggests that S. jamaicensis produces nectar for hummingbirds and moths since this is when they are most active. Flowers used in order to determine how much pollen remained on the stamen after visitation by each potential pollinator. Observation of activity and statistical analysis showed that butterflies were the most abundant in visiting, but pollen amounts on the stamens did not show any significance for any of the species. Due to lack of sufficient data on moths, the amount of pollen left over after visitation of these species was unable to be determined.
Abstract:
Stachytarpheta jamaicensis ha sido documentada como una especie que atrae diferentes visitantes pero su verdadero polinizador es desconocido. Muestre néctar de 22 plantas individuales durante varias horas del día y determine que S. jamaicensis produce la mayor parte del néctar durante las 6:00am y las 6:00pm. La visita de los polinizadores fue registrada a cada hora, diez flores fueron reunidas para cada uno de los polinizadores potenciales después de que ellos obtuvieran el néctar de las flores.
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Born Digital

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Determination of the optimal pollinator of Stachytarpheta jamaicensis (Verbenaceae) based on nectar production throughout the day Stephanie Siemek Department of Biology, Villa Julie College ABSTRACT Stachytarpheta jamaicensis has been found to have various visitors but its actual pollinator is unknown. I Collected nectar from 22 individual plants during various times of the day and I determined that S. jamaicensis produces most nectar during 6:00 am and 6:00 pm. Ob servation of the visitors were recorded for each hour and ten flowers were collected for each potential pollinator after they were observ ed obtaining nectar from the flowers. Nectar production was found to be significantly abundant early morning and late afternoon, this suggests that S. jamaicensis produces nectar for hummingbirds and moths since this is when they are most active. Flowers used in order to determine how much pollen remained on the stamen after visitation by each potential pollinator. Observation of activity and statistical analysis showed that butterflies were the most abundant in visiting, but po llen amounts on the stamens did not show any significance for any of the species. Due to lack of sufficient data on moths, the amount of pollen left over after visitation of these species was unable to be determined. RESUMEN Stachytarpheta jamaicensis ha sido documentada como una esperie que atrae diferentes visitantes pero su verdadero polinizador es desconocido. Muestrec el nctar de 22 plantas individuales du rante varias veces del da y determin que S. jamaicensis produce la mayora de los nctares durante las 6:00 am y 6:00 p.m. La visita de los polinizadores fue registrada por cada hora, diez despues flores fueron reunidas para cada potencial polinizador despus de que ellos obtuvieran el nctar de las flores. La produccin del nectar al principio de maana fue apreciablemente abundante y tambien al finalizar la tarde, esto sugiere que S. jamaicen sis produce el nctar para colibrs y polillas porque estas son los periodos cuando ellos son muy activos. Las flores utilizadas para determinar cunto pollen habia quedado en el estambre despus de cada visita por cada potential polinizador mariposas fueron los polinizadores ms abundantes vistos, pero la cantidad de pollen removidode los estambres no difirieron entre especies. Debido carecer de datos para las polillas, la cantidad de polen restante despus de cada visita de las polillas no pudo ser determinada. INTRODUCTION Community dynamics include many different relationships in which each species plays a distinct role. Angiosperms have been closely associ ated with pollinators, co-evolving to ensure a consistent relationship between the form of the flower and the sensory perception of specific pollinators. Plants have evolved to offer rewards, such as nutrient rich nectar, to ensure visitation by pollinators (Heywood, 1993). As ranges of plant species have extended some ha ve been found to adapt to new pollinators. Perez et al. (2006) found Schizanthus spp. (Solanaceae) to have evolved ne w flower morphology in order to accommodate a new pollinator. They found evidence of th is change by examining flower traits and DNA of Schizanthus spp Ancestral data showed that bees pollinated the plant, whereas today, bees, moths, and hummingbirds, depending on location, pollinate the flowers. The subject of this study, Stachytarpheta jamaicensis (Verbenaceae), is a native flowering plant, visited by many potential pollinato rs (Zuchowski 2005) and nectar r obbers (Miao & Dodd 2000). In order 1

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for plants to lessen competition betw een its pollinator and so called nec tar robbers it has been suggested that plants may have specific flow ering times (Robertson 1895, in Little 1983). Charles Robertsons results from his study on various Illinois woodland communities showed that flowering times were in sync with pollination guilds, which suggests that native species may have adapted to at tract a specific pollinator (Robertson 1895, in Little 1983). Pleasants (1980) study found signifi cance for flowering times of different pollination guilds within a complex community, but it is still unknown if the difference in flowering times depends on competition between pollinators only, or if other biotic or abiotic factors have influenced the plants. Another study, using herbaceous species, found that there was no relation between guild types and flowering times (Thomson 1997, in Little 1983). The purpose of my study was to determine if S. jamaicensis has adapted to attract a specific pollinator by investigating the timing of nectar pr oduction. Determining the exact pollinator will establish which species is critical in the reproduction of S. jamaicensis. Although studies have been unable to determine if flower production is dependent on its pollin ator, predictions of the po llinator will be based off of nectar production. If nectar produc tion is most abundant in the morning, this will suggest that the flowers are attracting hummingbirds since this is when they are most activ e. If nectar production is highest during the afternoon, then this sugge sts that the flower is at tracting insects since they are ectothermic and require the warmth of the day. If nectar production is grea test in the evening, then moths are implicated as pollinators. MATERIALS AND METHODS My study was performed in Caitas, Puntarenas Provide nce, Costa Rica at the Finca de Santamara (1300 m elevation). The subj ect of this study, S. jamaicensis, is a native, flowering plan t species that is a popular ornamental in Monteverde and the surrounding areas. It is visited by many potential pollinators such as butterflies, hummingbirds, moths, and bees that are attr acted by its nectar, however, it has not been shown if any of these organisms pollinat e the flowers (Zuchowski 2005). S. jamaicensis contains purple flowers that are 5-lobed with a narrow tube cal ibrated at 1.5 centimeters long that is light lilac or whitish (Zuchowski, 2005). Nectar robbers have been shown to lower the fitness of these flower by taking nectar without providing pollination services to the pl ant. A previous study showed that S. jamaicensis was visited by species that participate in action of nectar robbing, which resulted in a decrease in nectar production of those flowers (Miao & Dodd 2000). My observations of visitors were taken while sitti ng four meters away from 6:00 am to 6:00 pm on October 24 to October 30, for a total of 24 hours, taki ng note of which taxonomic group visited the flower for each specific hour. A species was considered a visi tor if found to be taking nectar from a flower. I collected each flower in order to measure at a later time how much po llen was left on the stamen after visitation. Ten flowers were collected total for each taxonomic group, as well as ten flowers from branches that were covered the night before in order to serve as controls. I used a total of 22 plants in order to test nectar production. Before taking measurements, I covered at least three branches that contained between 2-9 flowers for each plant the night before in order to keep potential pollinators from obtaining the nectar. The nectar was withdrawn from the flower by use of a capillary tube and then measured with a ruler using centimeters. Nectar production was measured at 6:00 am, 9:00 am, 12:00 pm, 3:00 pm, and 6:00 pm from October 24 to November 13 for a total of 30 hours. The plants were divided into six groups with three to five individuals in each group depend ing on the different locations of where they were found. The locations included disturbed areas, gr assy fields, and Lower Montane Moist Forest. 2

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After I measured nectar production of all 22 pl ants and ten flowers for each visiting taxonomic group was collected, the amount of pollen for the cont rol and experimental flowers was counted for each flower using a dissecting microscope (Olympus SZ40) The flowers of each species and the control were split apart using tweezers in order to focus on the stamen. Once the stamen was in focus, the dissecting microscope was focused as narrow as possible on the stamen, and the pollen grains were counted in this field of view. A ChiSquare Test was used in order to determ ine if the visitation by a particular pollinator was significantly more frequent than visitation by the ot her pollinators. Nectar pr oduction was analyzed, along with the amount of pollen for each of the collected flowers, using an ANOVA test. A LSD test for the Post Hoc test was used as well in order to determine wh ere the significant differen ces between nectar production was during the different hours. RESULTS I found that butterflies are th e most abundant visitor to S. jamaicensis (ChiSquare Test, x2 = 7.09; df = 2; p < 0.05) (Figure 1). Bees are the second most a bundant, and then hummingbirds. The results measuring nectar production showed that it wa s highest at 6:00 am and again at 6:00 pm (ANOVA test, F = 15.77; df effect = 4; df error = 101; p = 0.00) (Figure 2). When comparing the amount of pollen grains on each flower it was found that there was no significance am ong the pollinators (ANOVA test, F = 1.09; df effect = 3; df error = 36; p = 0.37) (Figure 3). When observing the stamens, however, almost all anthers of flowers visited by hummingbirds contai ned little or no pollen. DISCUSSION Since S. jamaicensis is known to have many hummingbird visito rs (Zuchowski 2005), it was expected that nectar production would be highest at 6:00 am when these birds are most active. According to the results, a significantly greater amount of nect ar is found during this time but agai n at 6:00 pm. This could suggest that S. jamaicensis produces nectar in order to attract hummingbi rds and moths because this is when they are most active. A study done on Centaurea scabiosa and Centaurea nigra, plants that have different insects as pollinators, found C. scabiosa to produce nectar continuously un til new flowers started to open. Similarly, C. nigra was found to produce nectar throughout the day until 6:00 pm (Lack 1982). Since these plants accommodated to their numerous ins ect pollinators by producing nectar throughout the day there is reason to believe that S. jamaicensis has done the same in order to accommodate to hummingbirds and moths. It was found that butterflies are significantly mo re abundant than the other pollinators. This could be due to the fact that ma jority of my observations were ta ken during the times when it was sunny or partly cloudy, which is when butterflies are most active. Bees are second most abundant, which could be because bees are quick learners and recognize colo rs, odors, and outlines very easily. In addition, since they are able to find flowers quickly they become consis tent with visits to a part icular flower if they find that flower to produce enough nectar (Raven et al. 1986). Sunny weather may have had an effect of how many hummingbird visitations were observed as well. Hummingbirds are active during any type of weather, while bees and butterf lies are only active during sunny weather. Because I only made observations during sunny weather, my data could be skewed towards observations of bees and butterflies. By not observing hummingbird activity during bad weat her, I may have underestimated the relative frequency of hummingbird visits, compared to other visitors. Moths were neve r seen visiting flowers, which could be due to cloudiness or lack of li ght in order to see the moths at night. 3

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When observing pollen grains in order to compare the amount of pollen missing from the stamens it was found that no significant amount of pollen was missing for any of the flowers visited. Although, results have found no difference in pollen amounts, I observed that most pollen was missing from stamens that were visited by hummingbirds. Pollination has b een described as being a sloppy procedure where pollen transfers do not always result between interactions of plants and visitors (Her rara and Olle 2002). Therefore, statistical analysis ma y have showed no difference between specific pollinators and amount of pollen missing from each of the visited flowers, there is reason to believe that at least one of these taxonomic groups is the actual pollinator of this plant. Since nectar production seemed to be most abundant at 6:00 am and 6:00 pm it is suggested that Stachytarpheta jamaicensis produces nectar in order to attract specific pollinators. Due to lack of data, I was unable to determine whether or not moths collect pollen. Future studies may be needed in order to increase data on this particular theory. In addition, final results showed that bu tterflies were most abundant visitors, but difference in pollen grains did not show any si gnificance between any of the taxonomic groups. Other studies that could be done in rela tion to this study include looking at other various flowers to determine nectar production in relation to when their pollinators are most activ e. This could then provide more evidence as to whether or not flowers, in general, produce nectar during cert ain times in order to attract their specific pollinator. ACKNOWLEDGEMENTS I would like to thank the Santamara family for letting me use thei r farm and helping me find the plants that I used for my pro ject. I would also like to thank them for the support and the coffee breaks in between working on my project and studying. I would al so like to thank Camryn Pennington and Thomas McFarland for answering all of my questions and helping me obtain the materials needed in order to complete my project. I would like to thank Tania Pizarro for helping me with my data and interpretations of my statistical analysis and for being such a great advisor. Also, a special thanks to Katherine Puzio and Lili Prahl for helping m e collect my data before the rain and during those dark gloomy evenings. Thank you to Katherine Lulling and to Lili Prahl for proof-reading my paper in order to make it the best it could be. Thank you to Alan and Karen Masters for answering my questions and helping me get through the semester. Lastly, thank you to the station and to all the students. You have made this experienc e worthwhile and I have enjoyed spending the semester with all of you. LITERATURE CITED Bawa, K. S. 1990. PlantPollinator Interactions in Tropical Rainforests. Annual Reviews Inc 21 :399-422. Herrera, C. and O. Pellmyr. 2002. PlantAnimal Interactions: An Evolutionary Ap proach. Blackwell Publishing: Massachusetts. Heywood, V.H. 1993. Flowering Plants of the World. Oxford University Press, New York. Lack, A. 1982. Competition for pollinators in the ecology of Centaurea scabiosa L. and Centaurea nigra L. II. Observations on nectar production. New Phytologist 91 : 309-320. Miao, Darren and Athena Dodd 2000 (Spring). Felony an d the flowering plant: Effect s of nectar robbery on Stachytarpheta jamaicensis pollen uses. OTSUngraduate Semester Abroad Program: 33-35. Perez, F., M. T. K. Arroyo, R. Medel, and M. A. Hershkovitz. 2006. Ancestral reconstruction of flower morphology and pollination syst ems in Schizanthus (Solanaceae). American Journal of Botany 93 : 1029-1038. Pleasants, J. M. 1980. Competition for bumblebee po llinators in Rocky Mountain plant communities. Ecology 61: 14461459. 4

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In: Handbook of Experimental Biology, Jones Little. Van Nostrand Reinhold Company Inc. New York, N.Y, pp. 282-283. Raven, P. et al. 1986. Biology of Plants. Worth Publishing Inc: New York. Robertson, C. 1895. The philosophy of flower seasons, and the phaenological relations of the entomophilous flora and the anthophilous insect fauna. Am. Nat. 29:97-117. In: Handbook of Experimental Biology, Jones Little. Van Nostrand Reinhold Company Inc. New York, N.Y, pp. 282283. Thomson, J.D 1978. Competition and cooperation in plantpollinator systems. Doctoral dissertation, University of Wisconsin, Madison. In: Handbook of Experimental Biology, Jones Little. Van Nostrand Reinhold Company Inc. New York, N.Y, pp. 282283. Zuchowski, W. 2005. A Guide to Tropical Plants of Costa Rica. Distribuidores Zo na Tropical, Miami, Florida. 0 20 40 60 80 100 120 140 hummingbird Butterfly BeesPollinator 5

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Std. Dev. Std. Err. Mean HOURNECTAR (cm) -0,04 0,00 0,04 0,08 0,12 0,16 0,20 6:00 am9:00 am12:00 pm3:00 pm6:00 pm Figure 2. Nectar production at di fferent hours of the day of Stachytarpheta jamaicensis in Caitas, measured by length in capillary tube (ANOVA, F=15.77; df effect= 4; df error= 101; p<0.05). Nectar ( cm ) Figure 1. Number of pollinators of different taxonomic groups visiting Stachytarpheta jamaicensis from 6:00 am to 6:00 pm during a two-day period (ChiSquare, 2 = 7.09; df = 2; p < 0.05). 6

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7 Std. Dev. Std. Err. Mean Pollinators 20 60 100 140 180 220 260 300 # POLLEN ControlBeesButterfliesHummingbirds Figure 3. Number of pollen grains found on flowers of Stachytarpheta jamaicensis after the visitation of poten tial pollinators (ANOVA, F = 1.09; df effect = 3; df error = 36; p=0.37). # Pollen g rains


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Determinacin de los polinizadores ptimos de Stachytarpheta jamaicensis (Verbenaceae) basada en la produccin de nctar durante el transcurso del da
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Stachytarpheta jamaicensis has been found to have various visitors but its actual pollinator is unknown. I Collected nectar from 22 individual plants during various times of the day and I determined that S. jamaicensis produces most nectar during 6:00 am and 6:00 pm. Observation of the visitors were recorded for each hour and ten flowers were collected for each potential pollinator after they were observed obtaining nectar from the flowers. Nectar production was found to be significantly abundant early morning and late afternoon, this suggests that S. jamaicensis produces nectar for hummingbirds and moths since this is when they are most active. Flowers used in order to determine how much pollen remained on the stamen after visitation by each potential pollinator. Observation of activity and statistical analysis showed that butterflies were the most abundant in visiting, but pollen amounts on the stamens did not show any significance for any of the species. Due to lack of sufficient data on moths, the amount of pollen left over after visitation of these species was unable to be determined.
Stachytarpheta jamaicensis ha sido documentada como una especie que atrae diferentes visitantes pero su verdadero polinizador es desconocido. Muestre nctar de 22 plantas individuales durante varias horas del da y determine que S. jamaicensis produce la mayor parte del nctar durante las 6:00am y las 6:00pm. La visita de los polinizadores fue registrada a cada hora, diez flores fueron reunidas para cada uno de los polinizadores potenciales despus de que ellos obtuvieran el nctar de las flores.
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Pollination by animals
Verbenaceae--Costa Rica--Puntarenas--Caitas
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Polinizado por insectos
Polinizado por animales
Verbenaceae--Costa Rica--Puntarenas--Caitas
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Tropical Ecology 2006
Stachytarpheta jamaicensis
Ecologa Tropical 2006
Stachytarpheta jamaicensis
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Reports
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CIEE
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