Foraging preference of Atta cephalotes (Hymenoptera: Formicidae)


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Foraging preference of Atta cephalotes (Hymenoptera: Formicidae)

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Title:
Foraging preference of Atta cephalotes (Hymenoptera: Formicidae)
Translated Title:
Preferencia de forrajeo de Atta cephalotes (Hymenoptera Formicidae)
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Klein, Laurel
Reid, Joseph
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Ants--Behavior ( lcsh )
Hormigas--Comportamiento ( lcsh )
Costa Rica--Puntarenas--Monteverde Zone--Cerro Plano
Costa Rica--Puntarenas--Zona de Monteverde--Cerro Plano
CIEE Fall 2000
CIEE Otoño 2000
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Reports

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Abstract:
Leaf cutter ants, Atta cephalotes, were found to make distinct tree species choices as herbivores in the premontane wet forest of Cerro Plano, Costa Rica. One trail from each of six nests was studied. Trail lengths varied, ranging from 3.30 m to 40.40m. Trees were identified along the trail, as well as the host tree at the end of the trails. Three leaves were taken from each tree and tested for toughness, thickness, and percent water content. The results for each test for each tree along a trail were compared to those for the host tree. The ants selected for thinner leaves. A simple regression correlated leaf thickness and toughness. Because of the range of toughness per leaf thickness, however, the results for leaf selection based on toughness were not consistently significant with regards to being more or less tough than the host tree, suggesting that selection for toughness is secondary to selection to thickness. Selection for water content also yielded significant results, though; once again, not consistently significant with regards to having more or less water than the host tree. Our data suggests that other factors play a role in host selection of Atta, and further investigation of their selectivity would draw a more complete picture. ( ,, )
Abstract:
Las zompopas, Atta cephalotes, descubrieron ser especialistas en el bosque lluvioso de Cerro Plano en Monteverde, Costa Rica. Estudiamos seis nidos, un sendero de cada nido. Las longitudes de cada nido fueron diferentes, entre 12.30 y 40 metros. Identificamos los árboles a lo largo de los senderos, y los árboles anfitriones a los términos de los senderos. Tomamos tres hojas de cada árbol y pusimos cada hoja a prueba de espesor, dureza y contenido de agua. Comparamos los resultados todos de cada árbol con los resultados del árbol anfitrión. Los árboles anfitriones tenían hojas menos el espesor de las hojas de los árboles de los senderos. Es posible que las zompopas escogieran las plantas sin savia y terpenoids.
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Student affiliation: Department of Zoology, University of Texas-Austin.

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Monteverde Institute
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M39-00535 ( USFLDC DOI )
m39.535 ( USFLDC Handle )

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Foraging preference of Atta cephalotes Hymenoptera: Formicidae Laurel Klein Department of Zoology, University of Texas Austin. Joseph Reid Department of Botany, University of Wisconsin Madison. ABSTRACT Leaf cutter ants, Atta cephalotes , were found to make distinct tree species choices as herbivores in the premontane wet forest of Cerro Plano, Costa Rica. One trail from each of six nests was studied. Trail lengths varied, ranging from 3.30m to 40.40m. Trees were identified along the trail, as well as th e host tree at the end of the trails. Three leaves were taken from each tree and tested for toughness, thickness, and percent water content. The results for each test for each tree along a trail were compared to those for the host tree. The ants selected f or thinner leaves. A simple regression correlated leaf thickness and toughness. Because of the range of toughness per leaf thickness, however, the results for leaf selection based on toughness were not consistently significant with regards to being more or less tough than the host tree, suggesting that selection for toughness is secondary to selection to thickness. Selection for water content also yielded significant results, though; once again, not consistently significant with regards to having more or le ss water than the host . Our data suggests that other factors play a role in host selection of Atta, and further investigation of their selectivity would draw a more complete picture. RESUMEN Las zompopas, Atta cephalotes , descubrieron ser especialistas en el bosque lluvioso de Cerro Plano en Monteverde, Costa Rica. Estudiamos seis nidos, un sendero de cada nido. Las longitudes de cada nido fueron diferentes, entre 12.30 y 40 metros. Identificamos los árboles a lo largo de los senderos, y los árboles anfitr iones a los términos de los senderos. Tomamos tres hojas de cada árbol y pusimos cada hoja a prueba de espesor, dureza y contenido de agua. Comparamos los resultados todos de cada árbol con los resultados del árbol anfitrión. Los árboles anfitriones tenían hojas menos el espesor de las hojas de los árboles de los senderos. Es posible que las zompopas escogieran las plantas sin savia y terpenoids. INTRODUCTION The fungus growers Tribe Attini are limited to the New World, most of the 11 genera, approximatel y 200 species, occurring in the tropical portions of México, Central and South America Wilson, 1971. Atta cephalotes , leaf cutting ants, are found below 2000 meters throughout Costa Rica. The nests of Atta cephalotes have been observed to have up to 5 mi llion workers, including the small minimas, the large soldiers, and the most commonly noticed media. The nests of A. cephalotes can be seen as large bare areas with nest exits sometimes up to 50m apart. With the leaf material they collect, the ants grow a fungus, probably Leucocoprinus gogogylophora ,

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a Basidiomycete Martin, 1969 in Stevens, 1983. This fungus feeds the mature ants as well as the ant larvae Stevens, 1983. The ants also feed on the sap of the leaves that they cut Hölldobler and Wilson, 19 90. Leaf cutters are considered the dominant herbivores in the Neotropics, cutting an estimated 12% to 17% of all leaves Cherrett, 1986 in Hölldobler and Wilson, 1990. A. cephalotes is specialized to live in forest gaps, and thus thrives in plantation s and farms Cherret and Peregrine, 1976 in Hölldobler and Wilson, 1 990. They have the ability to utilize a diverse array of plant species, leading them to have a considerable impact of agriculture in the Neotropics. In Santa Rosa National Park, more th an 80 species of plants were taken by leaf cutters in one year Stevens 1983. Annual damage by these ants has been estimated to be in the billions of dollars Hö lldobler and Wilson, 1990. Plants have a variety of defenses from leaf cutter ants. Reducin g the nutritional quality of the leaves is one option. Lower levels of nitrogen and water have been shown to reduce herbivore preference. Leaf toughness has also been correlated with reduced herbivory. In addition, Howard 1988 has shown that selectivity is likely to be based on the presence of repellant substances in some plants, perhaps anti fungal compounds. Tropical leaves often have high levels of anthocyanins which have been shown to have anti fungal properties, making them inappropriate for leaf cut ters. Other repellent compounds include: terpenes, cyanogenic compounds, alkaloids, and saponins Coley and Barone, 1996. A study in Costa Rica showed that a colony of Paraponera clavata defended their host tree by attacking a foraging column of A. cephal otes Wetterer, 1994. Plants, therefore, can protect themselves by providing food for predators of the ants; in the case of P. clavata food is provided by extra floral nectaries Janzen and Carroll, 1983. Leaf cutting ants should not forage randomly. In stead, they should avoid well defended plants. A study done by Blanton and Ewel 1985 in Florencia Norte Forest of Costa Rica found that A. cephalotes attacked only 17 of 332 available plant species in Hölldobler and Wilson, 1990. Leaf cutter ants are known to avoid Hymenaea courbaril , which contains caryphyllene epoxide, a compound that has been shown to have anti fungal properties Howard and Wiemer 1986. Inga punctata , known for its extra floral nectaries which attract ants, has been shown to be def ended from leaf cutters at low elevations where nectar feeding ants are abundant Koptur, 1983. Leaf cutter ants may also have nutritional requirements for their fungi; however, these requirements aren€t well known Hlldobler and Wilson, 1990. In addit ion, Howard 1988 has shown that selectivity is likely to be based on the presence of repellant substances in some plants, perhaps anti fungal compounds. Of particular interest to us were the trails on which A. cephalotes forage. These trails can stretch for more than 100m Hölldobler and Wilson, 1990. The cost of transportation of leaves back to the nest should eventually offset the value of the leaves further down the trail Covich, 1976. One hypothesis is that the leaf cutters pass by suitable trees in order to preserve a back up supply of leaves, although this has also been refuted Hölldobler and Wilson, 1990. Previous studies have analyzed leaf cutter selection by placing rye flakes or leaf pieces in their trail and measuring rates of pick up How ard, 1988; Howard and Wiemer, 1986. Our study compared the choices made by leaf cutters in natural conditions. This way we were able to compare trees of the same species on the same trail. We hypothesized that A. cephalotes is a specialist herbivore. If s o, the plants passed on the way to the host should have been measurably

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different. To test this we compared leaf toughness, thickness, and water content between trees that the ants pass and trees that host the ants. We also noted the presence of secondary compounds as reported by Raffauf and Schultes 1990, and Mabberley 1997. MATERIALS AND METHODS Data collection on plant preference were carried out during the wet season in the premontane wet forest of Cerro Plano 1440m in Monteverde, Costa Rica. Col lection occurred between October 16 and November 10, 2000. We collected leaves from the trails of six colonies of Atta cephalotes . One trail was chosen for each of the six colonies. When possible, trails were chosen that went through a forested non monocu ltured area and had between 10 and 20 trees along the trail. Five of the six nests nests 1, 2, 4, 5, 6 were in forested areas, and their trails remained in the forest. Nest 3 was on the edge of an open field. The trail, however, went through a forested a rea. The length of each trail was measured Table 1. We collected leaves from all trees with a diameter at breast height DBH greater than 10cm within 2.5 meters of the ant trail. Leaves were also collected for trees with DBH greater than 10cm that were touching the host tree. Leaves were collected for identification and testing by breaking down small branches. Four methods were used in collecting specimens from the trees. If branches with leaves were low enough to reach, a branch was cut off with a knif e. Otherwise, a rope was thrown over a branch and then the branch was pulled down. If the branches were too high to throw the rope over, then a fishing line was shot over a branch. Then, with the fishing line, a rope was reeled over the branch and the bran ch was pulled down. Leaves were shot down with a slingshot and rocks when they were too high to throw a rope over, or shoot fishing line over. Twigs or small branches were collected and pressed in a plant press for identification. To aid in plant identifi cation, we also took note of the presence or absence and quality of sap, odor of the leaves and the DBH. Three additional leaves were collected from each tree to be for leaf measurements. The leaves were labeled with the tree they were from and placed in a plastic bag to protect them until the tests could be performed later that afternoon. Leaves were chosen on the basis of appearing to be an average, mature leaf with zero to minimal damage. Three leaf quality tests were performed: thickness, toughness, an d water content. First, we measured the leaf toughness with a penetrometer, which measured the weight at which a leaf was punctured. The total mass, in grams, required to break the leaf€s surface was recorded. The second test was a measurement of leaf thic kness with Spi Vernier calipers. For both tests, one measurement was taken per leaf. The measurement s were taken at the midway point on the leaf, avoiding the venation. For water content, we took an initial weight measurement after leaf toughness and thick ness were measured. The leaves were then left in a dry box at 28.5°C overnight, and the final weight measurement was taken the next day. Leaves not completely desiccated the following day were left in the dry box until they were dry. William Haber and Wil low Zuchowski identified plants to species. The term ‚host treeƒ indicates the tree from which the ants were currently harvesting leaves. The terms ‚trail treesƒ or ‚trail leavesƒ indicate those trees and their leaves on the trail leading up to the host tr ee. We compared the host tree species to the species of the

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other trees along the trail Tables 2, 3, 4, 5, 6, 7, and 8. The host was identified as common or rare, common meaning that the ants passed a tree of the same species along the trail, and rare me aning the host was a unique species to the trail. For some trees, we were able to get samples, but unable to identify those trees. For those trees, we included the results for the leaf tests, but did not include the tree species in our data. We looked up possible deterrent compounds for each tree identified Howard and Wiemer, 1986; Hölldobler and Wilson, 1990; Raffauf and Schultes, 1990; Mabberley, 1997. Each trail was analyzed separately in Stat View using One Grouped t tests. Trees along the trail and the touching trees were compared using the host tree as the expected mean for thickness, toughness, and percent water content. We also performed a simple regression correlating the toughness to the thickness of the leaves. Because trail two had two hos t trees, we separated the trail into 2A and 2B. For 2A, we compared the trees preceding host tree A to host tree A. For 2B, we compared trees preceding host tree B to host tree B. We exclude host tree A from our analysis of trail 2B. RESULTS For all six n ests, significant results were found for at least one of the three tests performed on the leaves Tables 2 9. Means and standard deviations are recorded in Tables 2 8. TOUGHNESS The host tree on trail 2A had a mean toughness in grams of 294.000 + 109.63 9. Trail 2A had trail leaves significantly less tough than the host tree€s p = 0.0005, mean = 243.433 + 52.547. Four out of five of the trail trees had leaves less tough than the host€s Table 3. Trail 2B€s host tree had leaves with a mean toughness of 362.367 + 209.464. All six trail trees had leaves less tough than the host€s leaves p = 0.004, mean = 223.75 + 67.332. Trails 4 and 6 had trail trees with tougher leaves than those of the host trees p = 0.014 and p = 0.0002 respectively. Trail trees on trail 4 had a mean of 173.257 + 65.495, nine of the ten trees were tougher than the host tree mean = 106.5 + 13.077. All 11 of the trees with toughness measurements on trail 6 had a mean toughness greater than the host tree€s. The host tree on trail 6 h ad a mean toughness of 66.233 + 27.863. Analysis of toughness on trails 1 and 5 yielded no significant results for differences in leaf toughness. Trails 1 and 5 had five out of 12 and nine out of 18 trees respectively with a mean toughness greater than the ir hosts. THICKNESS Analysis of leaf thickness on trails 1, 2A, 2B, 4, and 6 revealed that leaves along the trail were thicker than those of the host trees p = 0.0055, 0.0384, 0.0212, 0.0156, 0.0006 respectively. Nine of 12 trees on trail 1 had leaves th icker than the host€s. On trails 2A and 2B, five of five and five of six leaves, respectively, were thicker than their host trees € . There were eight out of ten and 11 of 12 leaves on trails 4 and 6 respectively that had thicker leaves than the host€s. Trai ls 3 and 5 yielded no significant results with respect to leaf thickness. The host trees had thicker leaves than

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three of ten and five of 18 trees on trail 3 and trail 5 respectively. In total there were 46 of 73 trees whose thickness was greater than thei r host€s thickness. Host trees 1 through 6 had mean thicknesses in millimeters of 0.233 + 0.058, 0.317 + 0.029, 0.167 + 0.029, 0.317 + 0.029, 0.113 + 0.012, 0.233 + 0.029, and 0.183 + 0.029 respectively. The trail trees in sequential order had mean thick nesses of 0.293 + .065, 0.39 + 0.049, 0.342 + 0.126, 0.24 + 0.134, 0.195 + 0.089, 0.219 + 0.081, 0.281 + 0.0748. WATER CONTENT The leaf cutter ants preferred leaves with a lower percent water content than the trail trees on trails 2B p = 0.0237, host mea n = 0.445 + 0.015, trail mean = 0.585 + .107 and 4 p=0.0086, host mean = 0.596 + 0.008, trail mean = 0.664 + .063. On trails 3 p = 0.0377, host mean = 0.634 + 0.018, trail mean = 0.568 + 0.086, 5 p = 0.0023, host mean = 0.683 + 0.014, trail mean = 0. 606 + 0.091, and 6 p = 0.002, host mean = 0.750 + 0.020, trail mean = 0.645 + 0.090, leaves with higher water content than the trail trees were preferred. Trails 1 and 2A yielded no significant results with respect to water content. In sequential order, 41.7%, 40%, 100%, 20%, 80%, 11.1%, and 8.3% of the trail trees on each trail had greater water content than the host tree did. TRAIL TREES VS. HOST TREES On the first five trails, the host trees were rare species, occurring only once on each trail. On tra ils 5 and 6 however, the host trees were common, occurring more than once on the trail. On trail 5, the ants both passed and harvested Oreopanax xalapensis Araliaceae, while on trail 6, the common host species was Alstomia pittieri Apocynaceae. Compari son of the trail O. xalapensis to the host O. xalapensis on trail 5 revealed a difference of 53.6% greater toughness, 49.8% more thickness, and 19.9% less water content in the host tree Table 10. In comparing the trail A. pittieri to the host A. pittieri on trail 6, however, there was only a difference of 3.1% less toughness, 8.7% more thickness, and 2.7% greater water content in the host tree Table 11. The thickness of the trail tree leaves in both trails was less than the thickness of the host tree le aves trail trees = 0.117 + 0.081, 0.167 + 0.074; host trees = .233 + 0.029, 0.183 + 0.029. This opposes the trend in Table 9, where the mean thickness of the trail leaves is generally greater than that of the host tree€s leaves. The ants consistently pa ssed up several species and families. Sorocea trophoides was passed a total of seven times on three trails. The S. trophoides were on average less tough, thicker, and contained more water mean toughness = 148.248 + 31.937, mean thickness = 0.264 + 0.067, mean water content = 0.641 + 0.0237 than the average of all the trees on all the trails mean toughness = 193.387 + 72.210, mean thickness = 0.250 + 0.096, mean water content = 0.608 + 0.092. Cupania glabra and Exothea paniculata of the family Sapindacea e were passed a total of 5 times on trails 1, 2A, 2B, and 3. The ants passed Inga punctata eight times on trails; it was also a host tree on trail 2B, although no I. punctata was passed on trail 2B. The I. punctata that were passed were significantly dif ferent from the I. punctata host tree in all three tests Table 12. The trail trees were 51.7% less tough host mean = 362.367 + 209.464,

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trail mean = 175.004 + 36.765, 30% thicker host mean = 0.167 + 0.029, trail mean = 0.221 + 0.039, and had 22.2% mo re water host mean = 0.445 + 0.015, trail mean = 0.544 + 0.058 than the host I. punctata . Results of the literature search for deterrent compounds are summarized in tables 14 and 15 Howard and Wiemer, 1986; Hölldobler and Wilson, 1990 ; Raffauf and Schu ltes, 1990; Mabberley, 1997. DISCUSSION TOUGHNESS Toughness showed significant differences within trails, but did not show a consistent trend across trails. Our simple regression correlated thickness and toughness Figure 1, however, within that correla tion; there is still a wide range of toughness per each leaf thickness. The ants appear to select for toughness secondary to thickness. It has been suggested that the forager size of leaf cutter ants has evolved over time for the optimal cutting of tough l eaves Wilson 1980 in Howard 1988. Previous studies have shown that toughness is unrelated to palatability, and that the evolution of body size in leaf cutters is a response to the challenges of leaf cutting, reducing the importance of tissue toughness in diet selection Howard 1988. The importance of leaf toughness in our study is difficult to ascertain. A more clear trend starts to emerge when taking into account the presence of deterrent compounds. THICKNESS In the four cases in which the data were si gnificant, the ants consistently showed a preference for thinner leaves. Thinner leaves may be easier for the ants to cut as well as carry. Previous studies have not looked at effects of leaf thickness in determining leaf selection Howard and Wiemer 1986; Howard 1988. A further course of study could attempt to correlate leaf thickness and carrying efficiency. WATER CONTENT Water content also showed significant differences within trails, but did not show a consistent trend across trails. We believe this t o be the result of different selection pressures for each nest. The moisture content of the leaves is a potentially important source of water for cultivating and maintaining proper humidity levels for their fungal gardens Howard and Weimer 1986. One nest may require higher water content for optimal fungal growth at a particular point in time, and thus choose leaves with more water than a different nest. TRAIL TREES VS. HOST TREES Some of the trees that were consistently passed up by A. cephalotes may hav e had some characteristics to make them particularly unattractive to the ants. Alternatively, the ants may be attracted to specific plants for their nutritional qualities, although the nutritional requirements of leaf cutters and their fungi are not well k nown. The family Moraceae is known for its thick latex, which may have been the repellent characteristic in Sorocea trophoides . When tested for sap, thick white sticky

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latex literally poured out of the tree. Latex has been known to adhere to the ants€ mand ibles, gluing them shut Howard and Wiemer 1986. However, this does not explain the ants€ choice of Alstomia pittieri Apocynaceae as a host tree. The I. punctata host tree, on trail 2B, had leaves that were significantly thinner, contained less water, and were tougher than the I. punctata found along the trails. The ant€s preference for thinner leaves is consistent with the overall trend noted earlier. Leaf thickness appears to be especially important because there should be little or no difference in l eaf chemistry between the Ingas . We already noted that leaf toughness is not likely to be a major factor in the ants€ choices, so the 51.7% change in toughness was surprising. The difference in water content was also relatively large and was not consistent with any trend we have yet observed. At high elevations, Inga is not protected from herbivory Koptur, 1983. Therefore, this is not a factor that needs to be considered in the ants€ choice of Inga as a host. Closer study of these I. punctata trees is req uired to understand the ants€ choice. There may have been factors involved that we were not able to measure, for example age or nitrogen levels, that may have influence d the ants on trail 2B to choose Inga as a host, while on other trails the Ingas were re peatedly passed. A pr evious study done by Howard 1988 examined the influence of leaf chemistry on leaf selection. This study suggests that the ants avoid substrates containing tannins as well as other deterrent compounds. Perhaps, if we had the time and resources to test the trail trees and host trees for secondary compounds, we would be able to paint a more complete picture to explain the host selection of the ants. While we were able to consult literature Howard and Wiemer, 1986; Hölldobler and Wilson , 1990; Raffauf and Schultes, 1990; Mabberley, 1997 on the presence or absence of secondary compounds Tables 14 and 15 in each of the trees identified, we do not know the nutritional necessities of the ants or their fungus. While we were able to ident ify some trees as having deterrent compounds, we still cannot definitively say that the ants would avoid these trees, as exhibited on trails 2A, 2B, and 6. Perhaps the concentrations of these compounds were so low that they did not affect the ants, or perh aps the particular compounds involved did not affect the ants. Also, the ants also discard leaves once they get to the nest. The ants may have been discarding these selections once they arrived at the nest. Without further investigation, we can only say t hat the ants appear to be moderately selective. There are definite trends in their selection related to thickness. They especially preferred leaves that were thinner than the typical leaves found along the trail. Toughness, as mentioned previously, appear s to be considered in the selection process secondary to thickness. There are so many factors involved in leaf selection toughness, thickness, water content, secondary compounds, that the ants may have to decide on a tree per tree basis. Some factors may be more important than others. Some leaves may have a particular nutritional quality so important that it overrides the consideration of thickness, toughness, or water content. Not knowing the nutritional needs of the colony, we cannot say whether or not the ants are actually selecting specific trees, or avoiding trees. The ants may not be very selective, and only have a few characte ristics they must select for to maintain their fungal gardens. In some cases, trees that had been passed by were seen to hos t the ants at a later date. Some trees, which were passed on the trail, also showed signs of being host to leaf cutters at an earlier time. We would have liked to have the opportunity to monitor the trails more closely to keep track of what trees were actu ally being used over a

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longer period of time along the trails. This might be especially helpful for the trails with a host of the same species as one of the trail trees. With these data, we would have a more comprehensive picture of why A. cephalotes in Ce rro Plano choose the trees they do. Greater knowledge of leaf cutters€ nutritional requirements would help us to decide if the ants are choosing plants they want, or simply avoiding plants they don€t want. ACKNOWLEDGEMENTS Thank you Mauricio Garcia for he lping to formulate the idea, Alan Masters for your guidance in the project, Andrew Rodstrom for your sling shot, Bill Haber and Willow Zuchowski for identifying our samples and for advice, the property owners who allowed us to use their land, Jim Wolfe, Ec ofarm, everyone else who helped us keep our sanity through long hours. LITERATURE CITED Blanton, C.M., and J.L. Ewel. 1985. Leaf cutting Ant Herbivory in Successional and Agricultural Tropical Ecosystems. Ecology 66 3: 861 869. Cherrett, J.M. 1986. H istory of the Leaf cutting Ant Proble m . Pages 10 17 in C.S. Lofgren and R.K. Vander Meer, eds., Fire Ants and Leaf cutting Ants: Biology and Management . Westview Press, Boulder, CO. Cherrett, J.M., and D.J. Peregrine. 1976. A Review of the Status of Le af cutting Ants and Their Control. Annals of Applied Biology 84 : 124 133. Coley, P.D., and J.A. Barone. 1996. Herbivory and Plant Defenses in Tropical Rainforests. Annual review of Ecology and Systematics 27 : 305 335. Covich, A.P. 1976. Analyzing Shap es of Foraging Areas: Sone Ecological and Economic Theories. Annual Review of Ecology and Systematics 7 :235 257. Hölldobler, B., and E.O. Wilson. 1990. The Fungus Growers. Pages 596 608 in The Ants . Harvard University Press, Cambridge, Massachusetts. Howard, J.J. 1988. Leafcutting Ant Diet Selection: Relative Influence of Leaf Chemistry And Physical Features. Ecology 69 1: 250 260. Howard, J.J., and D.F. Wiemer. 1986. Chemical Ecology of Host Plant Selection by the Leaf Cutting Ant, Atta cephalotes . Pages 260 272 in C.S. Lofgren and R.K. Vander Meer, editors. Fire Ants and Leafcutting Ants: Biology and Management . Westview Press, Boulder, CO. Janzen, D.H., and C.R. Carroll. 1983. Paraponera clavata . Pages 752 753 in D.H. Janzen, editor. Costa Rican Natural History . The University of Chicago Press, Chicago, IL. Koptur, S. 1983. Inga . Pages 259 261 in D.H. Janzen, editor. Costa Rican Natural History . The University of Chicago Press, Chicago, IL. Mabberley, D.J. 1997. The Plant „ Book . Ca mbridge University Press, Cambridge, United Kingdom Martin, M.M. 1969 . The Biochemical Basis of the Fungus Attine Ant Symbiosis. Science 169 : 16 20.

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Navas, H.R. 2000. Pages 94 95 in Ut ilidad de la s Plantas M edicinales . Editorial Universidad Nacional, San José, Costa Rica. Raffauf R.F., and R.E. Schultes. 1990. The Healing Forest: Medicinal and toxic Plants of the Northwest Amazonia . Dioscorides Press, Portland, OR. Stevens, G.C. 1983. Atta cephalotes . Pages 688 690 in D.H. Janzen, editor. Cost a Rican Natural History . The Univrsity of Chicago Press, Chicago, IL. Wetter, J.K. 1994. Attack by Paraponera clavata Prevents Herbivory by the Leaf cutting Ant, Atta cephalotes . Biotropica 26 : 462 465. Wilson, E.O. 1971. The Natural History of the F ungus growing Ants Tribe Attini. Pages 41 48 in The Insect Societies . Harvard University Press, Cambridge, Massachusetts. Wilson, E.O. 1980. Caste and Division of Labor in Leaf cutter Ants Hymenoptera: Formicidae: Atta . II. The Ergonomic Optimizati on of Leaf Cutting. Behavioral Ecology and Sociobiology 7: 157 165.

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__________________________________________________________________________________ Table 1 . Trail lengths and host trees . _______________________________________________________________ ___________________ Trail Length m Host Tree 1 40.40 Oreopanax panamensis 2A 3.30 Eugenia guatemalensis 2B 13.60 Inga punctata 3 21.70 Chionanthus panamensis 4 22.10 ??? 5 31.00 Oreopanax xalapensis 6 36.30 Alstomia pittieri ___________________ ________________________________________________________ Table 2 . Trail 1, means and standard deviations. Means greater than the host tree are bolded. Host tree values are italicized. P € val u es for One group t Test are in the sign column of the host t rees row, significant values are bolded. _____________________________________________________________________ Species Toughness mean g Std dev sign Thickness mean mm Std dev sign Water mean % mass Std dev sign Myrcianthes undesc. 327.233 7.681 + 0.320 0.069 + 0.413 0.051 Meliosma idiopoda 241.533 142.481 + 0.327 0.046 + 0.745 0.014 + Psychotria monteverdensis 204.000 82.194 0.207 0.012 0.458 0.139 Exothea peniculata 121.767 11.720 0.187 0.012 0.493 0.035 Sorocea trophoides 189.26 7 91.729 0.313 0.101 + 0.609 0.022 + Sapium laurifolium 299.133 147.846 + 0.393 0.012 + 0.625 0.331 + Hampea appendiculata 188.467 77.307 0.367 0.083 + 0.583 0.032 Hampea appendiculata 244.900 109.546 + 0.300 0.000 + 0.556 0.017 Ocotea flourbun da 173.700 49.109 0.200 0.000 0.563 0.002 Stauranthus perforatus 264.200 98.201 + 0.280 0.020 + 0.519 0.017 Sorocea trophoides 107.733 46.756 0.313 0.012 + 0.618 0.139 + Sorocea trophoides 143.033 34.512 0.307 0.012 + 0.654 0.047 + Oreopana x panamensis 225.367 45.600 0.223 0.233 0.058 0.0055 0.603 0.006 0.230 ______________________________________________________________________ Table 3 . Trail 2A, means and standard deviations. Means greater than the host tree are bolded. Host tree value s are italicized. P € values for One group t Test are in the sign column of the host trees row, significant values are bolded. ___________________________________________________________________________ Species Toughness mean g Std dev sign Thickness m ean mm Std dev sign Water mean % mass Std dev sign Billia colombiana 289.700 31.264 + 0.333 0.029 + 0.522 0.010 Dendropanax arboreus 188.100 56.524 0.467 0.058 + 0.637 0.036 + Cupania glabra 270.700 27.875 0.367 0.058 + 0.460 0.021 ??? 284. 000 64.286 0.383 0.029 + 0.623 0.060 + Cupania glabra 184.667 26.753 0.400 0.100 + 0.515 0.014 Eugenia guatemalensis 294.000 109.639 0.0005 0.317 0.029 0.04 0.586 0.006 0.365 ____________________________________________________________________ ____________ Table 4 . Trail 2B, means and standard deviations. Means greater than the host tree are bolded. Host tree values are italicized. P € values for One group t Test are in the sign column of the host trees row, significant values are bolded. __ _________________________________________________________________________ Species Toughness mean g Std dev sign Thickness mean mm Std dev sign Water mean % mass Std dev sign Billia colo mbiana 289.700 31.264 0.333 0.029 + 0.522 0.010 + Dendropanax arboreus 188.100 56.524 0.467 0.058 + 0.367 0.036 + Cupania glabra 270.7000 27.875 0.367 0.058 + 0.460 0.021 + ??? 284.000 64.286 0.383 0.029 + 0.623 0.060 + Cupania glabra 184.667 2 6.753 0.400 0.100 + 0.515 0.014 + Piper amalago 125.333 39.264 0.100 0.000 0.754 0.025 + Inga punctata 362.367 209.464 0.004 0.167 0.029 0.02 0.445 0.015 0.02

PAGE 11

__________________________________________________________________________________ Tab le 5 . Trail 3, means and standard deviations. Means greater than the host tree are bolded. Host tree values are italicized. P € values for One group t Test are in the sign column of the host tre es row, significant values are bolded. __________________________________________________________________________________ Table 6 . Trail 4, means and standard deviations. Means greater than the host tree ar e bolded. Host tree values are italicized. P € values for One group t Test are in the sign column of the host trees row, significant values are bolded. __________________________________________________________________________________ Table 7 . Trail 5, means and standard deviations. Means greater than the host tree are bolded. Host tree values are italicized. P € values for One group t Test are in the sign column of the host trees row, significant values are bolded. _______________________________ ___________________________________________________ Spec ies Toughness mean g Std dev sign Thickness mean mm Std dev sign Water mean % mass Std dev sign Cupania glabra 229.967 26.779 0.383 0.076 + 0.522 0.013 Cupania glabra 213.933 7.705 0.117 0.029 0.447 0.045 Panopsis suareolens 229.033 22.5 02 0.250 0.087 0.538 0.030 Citharexylum costaricensis 284.300 37.222 + 0.200 0.087 0.616 0.042 Ocotea whitei 217.800 49.368 0.100 0.000 0.573 0.015 Ocotea flouribunda 134.067 10.441 0.133 0.029 0.613 0.017 Trichilia havanensis 254 .967 16.224 + 0.517 0.029 + 0.665 0.008 + Prunus skutchii 203.567 16.393 0.333 0.058 + 0.499 0.006 Meliosma idiopoda 133.233 53.233 0.200 0.087 0.482 0.195 Meliosma idiopoda 162.500 14.290 0.167 0.029 0.721 0.152 + Chionanthus panamensis 247.333 32.234 0.028 0.317 0.029 0.09 0.634 0.018 0.04 Species Toughness mean g Std dev sign Thickness mean mm Std dev sign Water mean % mass Std dev sign Stauranthus perforatus 29 3.133 57.013 + 0.417 0.029 + 0.629 0.037 + Meliosma idiopoda 208.500 76.150 + 0.183 0.029 + 0.645 0.049 + Hasseltia flouribunda 182.567 49.400 + 0.200 0.000 + 0.659 0.014 + Sorocea trophoides 137.700 16.052 + 0.200 0.000 + 0.678 0.002 + Tabernaemonta l ongipes 41.100 8.741 0.200 0.000 + 0.729 0.023 + Picrasma excelsa 169.367 53.596 + 0.200 0.000 + 0.799 0.010 + Cassipourea elliptica 185.133 39.176 + 0.100 0.000 0.674 0.027 + Casearia sylvestris 223.300 52.514 + 0.107 0.012 0.584 0.009 Sorocea trophoides 148.967 31.970 + 0.217 0.029 + 0.653 0.015 + ??? 142.800 18.784 + 0.120 0.020 + 0.587 0.028 ??? 106.500 13.077 0.010 0.113 0.012 0.015 0.596 0.013 0.0086 Species Toughness mean g Std dev sign Thickness mean mm Std dev sign Water mean % mass Std dev sign Oreopanax xalapensis 86.600 0.900 0.117 0.029 0.819 0.003 + Hampea appendiculata 126.500 42. 686 0.283 0.029 + 0.634 0.015 Sorocea trophoides 191.233 84.475 + 0.167 0.058 0.629 0.062 Dendropanax arboreus 206.100 78.825 + 0.300 0.000 + 0.576 0.162 Sorocea trophoides 119.800 2.722 0.333 0.029 + 0.648 0.027 Nectandra salicina 207.83 3 98.320 + 0.133 0.058 0.484 0.069 Malvaviscus arboreus 131.200 38.074 0.417 0.076 + 0.665 0.007 Eugenia monticola 91.300 27.692 0.150 0.000 0.609 0.009 Stauranthus perforatus 259.867 10.401 + 0.317 0.029 + 0.724 0.031 + Nectandra salicin a 362.100 107.400 + 0.233 0.029 0 0.458 0.024 Styphnolobium montevirdensis 173.133 53.803 0.150 0.000 0.666 0.001 Meliosma idiopoda 204.833 44.615 + 0.183 0.029 0.621 0.004 Xylosma chlorantha 80.000 3.306 0.150 0.050 0.607 0.032 Ardis ia compressa 372.333 45.000 + 0.217 0.029 0.681 0.023 Inga punctata 223.033 121.006 + 0.200 0.000 0.514 0.029 Inga punctata 155.967 55.975 0.167 0.029 0.519 0.095 Inga punctata 137.800 30.216 0.200 0.000 0.530 0.033 Inga punctata 23 0.600 64.800 + 0.233 0.029 0 0.525 0.023 Oreopanax xalapensis 186.467 31.974 0.991 0.233 0.029 0.589 0.683 0.014 0.0023

PAGE 12

__________________________________________________________________________________ Table 8 . Trail 6, means and standard deviations . Means greater than the host tree are bolded. Host tree values are italicized. P € values for One group t Test are in the sign column of the host trees row, significant values are bolded . ________________________________________________________________ __________________ ______________________________________________________________ ____________________ Table 9 . Trends relative to the host. Positive signs indicate trail means greater than host mean. Insignificant results are reported as a zero . __________________________________________________________________________________ Leaf Characteristics Nest Toughness Thickness Water Content 1 0 + 0 2a + 0 2b + + 3 0 4 + + + 5 0 0 6 + + __________________________________________________________________________________ Table 10 . A comparison of average values for the two Oreopanax xalapensis trees on trail 5. Thickness of the trail tree leaves is less than that of the host trees, opposing the trend across all trails in Table 9. __________________________________________________________________________________ Tough ness g Thickness mm Water Content % mass P value .9916 .5891 .0023 Trail mean 86.600 0.117 81.9 Std. dev. 84.088 .081 .091 Host mean 186.467 0.233 68.3 Percent Difference 53.5% 49.8% +19.9% ___________________________________________________ _______________________________ Table 11 . A comparison of average values for the two Alstomia pitteri trees on trail 6. Thickness of the trail tree leaves is less than that of the host trees, opposing the trend across all trails in Table 9. Positive per cent difference values indicate trail mean greater than host . __________________________________________________________________________________ Toughness g Thickness mm Water Content % mass P value .0002 .0006 .002 Trail mean 68.333 0.167 73.0 S td. dev. 59.360 .074 .090 Host mean 66.233 0.183 75.0 Percent Difference +3.1% 8.7% 2.7% Species Toughness mean g Std dev sign Thickness mean mm Std dev sign Water mean % mass Std dev sign Inga punctata 160.300 29.858 + 0.217 0.029 + 0.602 0.005 + Inga punctata 140.800 22.926 + 0.267 0.029 + 0.659 0.001 + Inga punct ata 197.333 13.727 + 0.283 0.029 + 0.480 0.027 + Lasiantheae fruticosa No data No data 0 0.333 0.058 + 0.803 0.007 + Sapium macrocarpum 212.333 49.631 + 0.267 0.029 + 0.686 0.018 Sapium macrocarpum 174.833 70.234 + 0.250 0.000 + 0.737 0.008 Sapium macrocarpum 152.800 49.234 + 0.300 0.000 + 0.655 0.016 Psidium guajava 124.200 20.055 + 0.350 0.050 + 0.609 0.039 Psidium guajava 131.367 23.881 + 0.283 0.058 + 0.653 0.005 Alstomia pittieri 68.333 14.123 + 0.167 0.029 0.730 0.017 Clethra Ian ata 302.267 55.752 + 0.450 0.050 + 0.605 0.039 Inga punctata 154.200 7.908 + 0.200 0.000 + 0.521 0.010 Alstomia pittieri 66.233 27.863 0.0002 0.183 0.029 0.0006 0.750 0.020 0.002

PAGE 13

_________________________________________________________________________________ Table 12 . Results of One group t Test comparing Inga punctata found on the tra il to the I. punctata host tree. We gave p values a negative sign if the mean value of the trail trees was less than the host trees value. Positive percent difference values indicate trail mean greater than host . ________________________________________ __________________________________________ Toughness g Thickness mm Water Content % mass P value 0.0001 0.0062 0.0019 Trail mean 175.004 0.221 0.544 Std. dev. 36.765 0.039 0.058 Host mean 362.367 0.17 0.445 Percent Difference 51.7% +30% +22.2% __________________________________________________________________________________ Table 14 . Presence of deterrent compounds for trails 1, 2A, 2B, and 3. Host trees are in bold. __________________________________________________________________________________ Trail 1 ? Trail 2A ? Trail 2B ? Trail 3 ? Myrcianthes undesc. 0 Billia colombiana 0 Billia colombiana 0 Cupania glabra + Meliosma idiopoda 0 Dendropanax a rboreus 0 Dendropanax arboreus 0 Cupania glabra + Psychotria monteverdensis + Cupania glabra + Cupania glabra + Panopsis suareolens 0 Exothea peniculata 0 Cupania glabra + Cupania glabra + Citharexylum costaricensis 0 Sorocea trophoides 0 Eugenia guatem alensis + Piper amalago 0 Ocotea whitei + Sapium laurifolium + Inga punctata + Ocotea flouribunda + Hampea appendiculata 0 Trichilia havanensis + Hampea appendiculata 0 Prunus skutchii + Ocotea flouribunda + Meliosma idiopoda 0 Stauranth us perforatus 0 Meliosma idiopoda 0 Sorocea trophoides 0 Chionanthus panamensis 0 Sorocea trophoidea 0 Oreopanax panamensis 0 ___________ _______________________________________________________________________ Table 15 . Presence of deterrent compounds for trails 4, 5, and 6. Host trees are in bold . __________________________________________________________________________________ Trail 4 ? Trai l 5 ? Trail 6 ? Stauraundanthus perforatus 0 Oreopanax xalapensis 0 Inga punctata + Meliosma idiopoda 0 Hampea appendiculata 0 Inga punctata + Hasseltia flouribunda 0 Sorocea trophides 0 Inga punctata + Sorocea trophoides 0 Dendropanax arboreus 0 Lasi antheae fruticosa 0 Tabernaemonta longipes + Sorocea trophides 0 Sapium macrocarpum + Picrasma excelsa + Nectandra salicina + Sapium macrocarpum + Cassipourea elliptica + Malvaviscus arboreus 0 Sapium macrocarpum + Casearia sylvestris 0 Eugenia montico la + Psidium guajava 0 Sorocea trophoides 0 Stauranthus perforatus 0 Psidium guajava 0 ??? ? Nectandra salicina + Alstomia pitteri + ??? ? Styphnolobium montevirdensis + Clethra lanata 0 Meliosma idiopoda 0 Inga punctata + Xylosma chlorantha + Als tomia pitteri + Ardisia compressa 0 Inga punctata + Inga punctata + Inga punctata + Inga punctata + Oreopanax xalapensis 0

PAGE 14

Figure 1. Toughness vs Thickness Regression. Toughness is significantly correlated to thickness p = 0.039, R ^ 2 = 0.058


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