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Price, Jessica Rochelle
Influencia de la altitud, las especies hospedadoras, y el tamao del hospedador en la densidad del matapalo, Phorodendron robustissmum (Viscaceae)
Influence of elevation, host species, and host size on the density of mistletoe, Phorodendron robustissmum (Viscaceae)
Phorodendron robustissmum is an aerial hemiparasitic plant, dispersed by birds, that parasitize their hosts by tapping into the hosts vascular tissue. This research examines the density of mistletoe, Phorodendron robustissmum (Viscaceae) as a function of host species, host size, and elevation. This study was conducted in the Monteverde region in Costa Rica from 880- 1480 m. Data were collected on host species, density of mistletoe on two host species, elevation, and the diameter at breast height. ANCOVA and ANVOA showed that only host tree size influenced the clump density of Phorodendron robustissmum. Three different host species, Sapium glandulosum, Sapium laurifolium, and Sapium macrocarpum (Euphorbiaceae) harbor Phorodendron robustissmum in the study area.
Phorodendron robustissmum es una planta hemi-parsita area, dispersada por aves, que parasita a su hospedador tocando en el tejido vascular del husped. Esta investigacin examina la densidad del matapalo Phorodendron robustissmum (Viscaceae) en funcin de la especie hospedador, el tamao del hospedador y la elevacin. Este estudio fue hecho en la regin de Monteverde, Costa Rica a una altura de 880-1480 metros.
Text in English.
Mistletoes--Costa Rica--Puntarenas--Monteverde Zone
Cloud forest ecology--Costa Rica
Matapalos--Costa Rica--Puntarenas--Zona de Monteverde
Ecologa del bosque nuboso--Costa Rica
Tropical Ecology 2008
Phorodendron robustissmum--Costa Rica
Ecologa Tropical 2008
Phorodendron robustissmum--Costa Rica
t Monteverde Institute : Tropical Ecology
Influence of elevation, host species, and host size on the density of mistletoe, Phorodendron robustissmum Viscaceae Jessica Rochelle Price Department of Biology, Berea College ABSTRACT Phorodendron robustissmum is an ae rial hemiparasitic plant, disp ersed by birds, which parasitize their hosts by tapping into the hostÂ€s vascular tissue. This research examines the density of mistletoe, Phorodendron robustissmum Viscaceae as a function of host species, host size, and elevation. This study was conducted in the Monteverde region in Costa Rica from 880 1480 m. D ata were collected on host species, density of mistletoe on two host species, elevation, and the diameter at breast height. ANCOVA and ANVOA showed that only host tree size influenced the clump den sity of Phorodendron robustissmum. Three different host species, Sapium glandulosum, Sapium laurifolium, and Sapium macrocarpum Euphorbiaceae harbor Phorodendron robustissmum in the study area. RESUMEN Phorodendron robustissmum es una planta hemiparÃ¡si ta aÃ©rea, dispersada por aves, q ue parasita su hospedero tocando su tejido vascular. Esta investigaciÃ³n examina la densidad del matapalo Phorodendron robustissmum Viscaceae en funciÃ³n de la especie, tamaÃ±o del hospedero y elevaciÃ³n. Este e studio fue h echo en la regiÃ³n de Monteverde, Costa Rica de 880 Â 1480. Se tomaron datos de densidad en dos hospederos, elevaciÃ³n y diÃ¡metro a la altura del pecho DAP. ANCOVA y ANOVA muestran que solo el tamaÃ±o del hospedero influye en la densidad de Phorodendron r obustissmu m en una planta. Tres especies diferentes de hospedero Sapium glan dulosum, Sapium laurifolium, y Sapium macrocarpum Euphorbiaceae tienen Phorodendron robustissmum en el Ã¡rea de estudio . I NTRODUCTION Mistletoes are diverse members of the Ord er Santalales that represent the largest group of parasitic woody angiosperms in the world Kuijt, 1968. They are found in four families Loranthacea e, Misodendraceae, Santalaceae, and Viscaceae Amico, 2007. While being diverse in many regards, most mist letoe is bird dispersed, often epiphytic plants that parasitize their hosts by tapping into the hostÂ€s vascular tissue Sargent, 1994 , Amico, 2007. There are some types of mistletoes that are dispersed balistically or by wind , but most are bird disperse d Restrepo, 2002 . Birds usually eat the viscous berries from the mistletoes and then either defecate onto branches or in some cases rub the seeds from their beaks onto the branches of trees Thompson, unpublished data. This method of seed dispersal giv es rise to the high diversity in mistletoe spe cies found throughout the world Restrepo, 2002. When the birds disperse the mistletoe seeds onto tree branches, the seeds grow into the tree causing canker ous swellings to form in the branches . The n, mistleto e stems will grow out of the cankers and form clumps,
multiple mistletoe stems growing from one location o n the branch that range in size from small to large. Large infestations of mistletoe, meaning many clumps, can lead to the deat h of the host tree it i nhabit s but usually takes many years and depends on the host tree it inhabits Thompson, unpublished data . H ost tree species vary with the mistletoe species tha t inhabit them. Meaning, a species of mistletoe will be host specific to a certain species or g enus of tree and will only be found in that species or genus. Yet, not much is known about how or why mistl etoe species are host specific but p ossible explanations are that mistletoe distribution is 1 disperser dependent , or 2 host/mistletoe dependent. I f mistletoe distribution is disperser dependent, then mistletoe would be able to grow in any tree species but would depend on the disperserÂ€s preference. Conversely, if it was dependent on the mistletoe/host species , then mistletoe would only grow in certa in tree species even when dispersed in others. Mistletoes in the region of Monteverde, Costa Rica include Phorodendron robustissmum, a species that occurs on members of the genus Sapium that occurs from 0 m elevation to 2000 m elevation. It has been rep orted that Phorodendron robustissmum is host specific on Sapium oligoneurum in the Euphorbiaceae in the Monteverde region Willoughby, 1995. However, not enough research has been done to confirm that P. robustissmum is only found to inhabit the Sapium ge nus. Currently, there are four described Sapium spp . found in the Monteverde region from 700 1500m Fogden, 1993 . These species differ in that they vary in elevation and size. For instance, Sapium glandulossum is found from 900 2000m and is 5 20m tall whe re as Sapium laurifolium is found from 0 1200 m and is 8 25 m tall. In addition to the host specificity of mistletoe species, more research needs to done to determine what influences mistletoe growth in host trees. The elevation and size of the host tree could also influence the growth of Phorodendron robustissmu m and other mistletoe species . The purpose of this study is to investigate whether mistletoe clump density is influenced by the host species, diameter at breast height DBH, elevation, or some com bination of these three. In this study, I determined the DBH, elevation, number of clumps of mistletoe, and the species of host trees that Phorodendron robustissum was found to inhabit. With this information I determined whether the clump density of Phorod endron robustissum is influenced by elevation, species, or host size. This research determines the host species of Phorodendron robustissimum found along an elevational gradient and the possible role of host size and species in determining mistletoe densit y. By determining, what factors can influence the growth patterns of Phorodendron robustissmum; future research can determine such things as the affects of mistletoe on its host species and how that interaction is affecting the community. MATERIALS AND MET HODS T his study took place in the Monteverde region, of Costa Rica from April 11 May 8, 2008. In area A and B the mistletoe observed was within 20 m from the road whereas in areas C, D, and E the mistletoe observed was in fields off of the main road Figu re 1. Eighty eight host trees were observed from 883 m elevation to 1481 m within these five areas. Observations were made by first identifying the mistletoe to ensure that it was Phorodendron robustissimum . In order to determine if the size of the host s pecies influences the clump density, the circumference at breast
height was taken using a tape measure . The diameter was then calculated from the circumference measured for each tree. The trees that were branched below the breast height diameter were still measured for each branch and then added together to get the diameter. The number of clumps was counted for each host tree containing Phorodendron robustissimum . Clumps were determined by clearly separated clusters of mistletoe in the host tree. In some in stances, the clumps were so clustered together that they appeared to be one huge clump. In these circumstances, the tree was marked as infested because the tree had so much mistletoe, I could not differentiate between the clumps. For testing, I reported t he Â‚infestedÂƒ host trees containing approximately 20 clumps. The elevation was also recorded for each host tree with an altimeter to later use to determine if elevation influences that clump density or the growth of host species. The host species were iden tified by taking cut samples to William Haber. I ran an analysis of covariance ANCOVA between clump densities, elevation and species to determine whether clump density varied because of elevation, tree species, or the interaction of elevation and species . I also ran an ANCOVA between clump density, the diameter at breast height, and the species of tree to determine whether clump density varied with DBH, host species, or the interaction of host size and species. Lastly, I wanted to look at whether host s pecies varied with their average diameter at breast height, which I tested with an analysis of variance RESULTS I identified three different host species of Phorodendron robustissimum , specifically, Sapium glandulosum , Sapium laurifolium , and Sapium macro carpum Euphorbiaceae. The data collected from Sapium laurifolium was not used in any of these tests because only two trees were found to be occupied with Phorodendron robustissimum . The analysis of covariance ANCOVA relating clump densities to elevati on, host species or the interaction of elevation and species was not significant r 2 = 0.05, F = 2.56, P = 0.0607 , N = 85. However, the ANCOVA relating clump density to host species, host size, or an interaction was significant r 2 =0.11 , F for model 4.53, P 0.0055, N=85 Figure 2. Lastly, an Figure 1. Map of study site where Phorodendron robustissum was found in host species. Roads are signified by yellow. Each outlined box represents an area where mistletoe was found. Pink is Area A, teal is Area B, purple is Area C, green i s Area D, and red is Area E.
Figure 3. Average DBH for Sapium macrocarpum and Sapium glandulossum analysis of variance revealed that hosts differed significantly in size, with S. glandulosum being larger than S. macrocarpum r 2 = 0.49, F = 83.22, P = 0.0001 Figure 3 . y = 0.1025x + 4.5874 RÂ² = 0.04 y = 0.1025x + 4.5874 RÂ² = 0.04 y = 0.2044x 2.6934 RÂ² = 0.1863 y = 0.2044x 2.6934 RÂ² = 0.1863 Density of clumps per tree Diameter at breast height cm Sapium macrocarpum Sapium glandulossum Linear Sapium macrocarpum Linear Sapium macrocarpum Figure 2. Regression of the density of clumps of Phorodendron robustissimum and DBH of the host trees Sapium macrocarpum and Sapium glandulossum r 2 =0.110806, F = 4.5311, P 0.0055, N=85. Average diameter at breast height cm Host tree species
DISCUSSION My result s showed that there is no effect of species or elevation on the density of Phorodendron robustissimum . However, the diameter at breast height of host trees significantly affected the density of clumps of mistletoe. On average, the greater the DBH, the grea ter number of clumps found. The ANOVA showed that there was a significant difference in average size between S. macrocarpum and S. glandulossum . These results show that the larger the tree, the greater the density of Phorodendron robustissmum in Sapium and that on average, S. glandulossum is larger than S. macrocarpum . These results support a previous study suggesting that the size of the substrate influences the growth of the mistletoe yet adds new information that the size of the host tree influences the mistletoe growth. Still, the reason as to way is not answered in this study. Possible explanations could be 1 larger trees are l arger targets for the disperser, 2 larger trees are healthier than smaller trees, 3 larger trees are older trees , or 4 that larger trees provide larger canopies . In the case of larger trees being larger target areas for dispersers would indicate that the disperser prefers going to larger trees to perch or f eed. This would make since because larger trees could provide more pro tection than smaller trees Thompson, unpublished data . These findings could also suggest that larger trees are healthier trees, which would provide better substrate and nutrients to the mistletoe. Or, maybe larger trees are older which allow for more mis tletoe to be established which would account for a greater density of clumps in the host tree. Lastly, these results might indicate that l arger trees have larger crowns have higher amounts of sunlight to support the mistletoe. In a previous study, it was d etermined that the larger crowns support more mistletoe then smaller crowns and it was possibly do to 1 the amount of sunlight the mistletoe receives, or 2 larger crowns provide better branches for the mistletoe to grow Thompson, unpublished data . Wha tever be the explanation of the factors that influence mistletoe growth, the first step in understanding mistletoe interactions is determining the host species and growth patterns of the mistletoe. Without that information, you cannot look at how that mist letoe species is influenced by the host species or the disperser and vice versa. While seeming like an simple plant, the interacti ons that mistletoes have with its disperser and host species is complex and needs much more research than it is given. While t his research is only a small part in helping to better understand those interactions and how they work, it still is providing more information and possible explanations to explain this complex web. ACKNOWLEDGEMENTS I would like to thank Karen Masters for her time and patience to help me work through my research project. I greatly appreciate William Haber for taking the time to identify my mistletoe species and the host species. I would also like to thank Taegan McMahon for her understanding and help. I wo uld like to thank Martha Campbell and the Guindon Family for allowing me to use their property for my study sites.
LITERATURE CITED Amico, G. C. 2007. Phylogenetic relationships and ecological speciation in the mistletoe Tristerix Loranthaceae: the influence of pollinators, dispersers, and hosts. American Journal of Botany 944: 558 Â 567. Aukema, J. E. 2002. Mistletoes as parasites and seed dispersing birds and disease vectors: current understanding, challenges and opportunities. Seed dispersal a nd frugivory: ecology, evolution and conservation . D. J. Levey, ed . CABI Publishing, New York. pp. 99 110 Fogden, M. 1993. An annotated checklist of the birds of Monteverde and PeÃ± as Blancas. Michael Fogden Monteverde, Costa Rica. 1993. Kuijt, J. 196 8. Mutual affinities of Santalean families. Brittonia 20, 136 147. Kuijt, J. 1969. The biology of parasitic flowering plants. Seed dispersal and frugivory: ecology, evolution and conservation. D. J. Levey, ed. CAB I Publishing, New York, pp. 83 98 Rest repo, C. 2002. The role of vertebrates in the diversification of New World mistletoes. Seed dispersal and frugivory: ecology, evolution and conservation . Author. CABI Publishing, New York. pp. 83 98. Rowan, M. A. 1998. Mistletoe position in the host tre e Psidium guajava . Tropical ecology and conservation . Fall 1998. 1 8. Sargent, S. 1994. Dissertation: Seed dispersal of mistletoe by birds in Monteverde, Costa Rica. Cornell University. Thompson, R. L. Eastern Mistletoe Phoradendron leucarpum , Viscac eae in the City of Berea, Kentucky: a High Incidence of Infestation and Eight New Host Species for Kentucky . Unpubl. Data Willoughby, S. T. 1995. Preferential parasitism by mistletoe species on different host trees. UCEAP Tropical biology . Spring 1995 . 126 141.