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Oviposition preference and larval growth rates of Caligo memnon (Nymphalidae: Brassolinae)

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Title:
Oviposition preference and larval growth rates of Caligo memnon (Nymphalidae: Brassolinae)
Translated Title:
Oviposición de las preferencias y las tasas de crecimiento de las larvas de Caligo memnon (Nymphalidae: Brassolinae) ( )
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Book
Language:
English
Creator:
Webb, Emily
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Subjects

Subjects / Keywords:
Caligo memnon   ( lcsh )
Insects--Behavior   ( lcsh )
Caligo memnon
Insectos--Comportamiento
Tropical Ecology 2006
Oviposition
Ecología Tropical 2006
Oviposición
Genre:
Reports   ( lcsh )
Reports

Notes

Abstract:
Caligo memnon caterpillars specialize on plants in three families, Heliconiaceae, Marantaceae, and Musaceea. These families are in the Order Zingiberales. Heliconiaceae and Marantaceae are native to the Neotropics, but Musaceae is an introduced family. I studied oviposition preference and larval performance of C. memnon on four host plants: Heliconia latispatha and Heliconia stricta (Heliconiacea), Calathea insignis (Marantaceae), and Musa acuminata (Musacea). Results showed that preferred host plants for oviposition did not correspond to the host plant that provided the fastest growth rate for caterpillars. Females preferred to oviposit on M. acuminata even though larval growth was lowest on this species, though not significantly. It may be that C. memnon is exhibiting maladaptive oviposition behavior and the introduced M. acuminata may be confusing the coevolved mechanisms for host plant choice.
Abstract:
Estudié la preferencia en el sitio de oviposición y el desarrollo de la larva de C. memnon en cuatro plantas hospederas: Heliconia latispatha y Heliconia stricta (Heliconiacea), Calathea insignis (Marantaceae) y Musa acuminata (Musaceae).
Language:
Text in English.
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Born Digital

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usfldc doi - M39-00184
usfldc handle - m39.184
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Caligo memnon caterpillars specialize on plants in three families, Heliconiaceae, Marantaceae, and Musaceea. These families are in the Order Zingiberales. Heliconiaceae and Marantaceae are native to the Neotropics, but Musaceae is an introduced family. I studied oviposition preference and larval performance of C. memnon on four host plants: Heliconia latispatha and Heliconia stricta (Heliconiacea), Calathea insignis (Marantaceae), and Musa acuminata (Musacea). Results showed that preferred host plants for oviposition did not correspond to the host plant that provided the fastest growth rate for caterpillars. Females preferred to oviposit on M. acuminata even though larval growth was lowest on this species, though not significantly. It may be that C. memnon is exhibiting maladaptive oviposition behavior and the introduced M. acuminata may be confusing the coevolved mechanisms for host plant choice.
Estudi la preferencia en el sitio de oviposicin y el desarrollo de la larva de C. memnon en cuatro plantas hospederas: Heliconia latispatha y Heliconia stricta (Heliconiacea), Calathea insignis (Marantaceae) y Musa acuminata (Musaceae).
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Insects--Behavior
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Oviposition
Ecologa Tropical 2006
Oviposicin
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Oviposition preference and larval growth rates of Caligo memnon (Nymphalidae: Brassolinae) Emily Webb Department of Biology, Indiana University Abstract Caligo memnon caterpillars specialize on plants in three families, Heliconiaceae, Marantaceae, and Musaceea. These families are in the Order Zingiberales. Heliconiaceae and Marantaceae are native to the Neotropics but Musaceae is an introduced family. I studied oviposition preferen ce and larval performance of C. memnon on four host plants: Heliconia latispatha and Heliconia stricta (Heliconiacea), Calathea insignis (Marantaceae), and Musa acuminata (Musacea). Results showed that preferred host plants for oviposition did not correspond to the host plant that provi ded the fastest growth rate for caterpillars. Females preferred to oviposit on M. acuminata even though larval growth was lowest on this species, th ough not significantly. It may be that C. memnon is exhibiting maladaptive ovipositi on behavior and the introduced M. acuminata may be confusing the coevolved mechan isms for host plant choice. Resumen Las orugas de la especie Caligo memnon se especializan en plantas de tres familias, Heliconiaceae, Marantaceae, y Musaceea. Esta s familias son del Orden Zingiberales. Heliconiaceae y Marantaceae son nativas de los Neotropics, pero Musaceae es una familia introducida. Yo estudi la preferencia en el sitio de oviposicin y el desarrollo de la larva de C. memnon en cuatro plantas husped: Heliconia latispatha y Heliconia stricta (Heliconiacea), Calathea insignis ( Marantaceae), y Musa acuminata (Musacea). Los resultados mostraron que la planta que la es pecie C. memnon prefiri para ovipositar no coincidi con la planta huspe d que proporcion el crecimient o ms rpido de las orugas. Las hembras prefieron ovipositin en M. acuminata an cuando el crecimiento de la larva fue menor en esta especie. Es possible que C. memnon est maladaptada en su comportamiento de ovipocisin y M. acuminata este confundiando sus mecanismos de coevolution para la selecci on de la planta husped. 1

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Introduction The host plant species on which female butterf lies lay their eggs can be important to the growth and survival of their offspring. E ggs are vulnerable to predation and the larvae are relatively immobile, so the plant on whic h larvae hatch will often serve as their food source until they pupate (Rausher 1997). Because of this it is very important that adult butterflies develop an oviposition preference th at facilitates fast growth rates, adequate nutritional sequestration, and high survival. Ovipositing butterflies encounter a variet y of possible larval host plant species with different physical and chemical characteristics. It is likely that there is a combination of cues that influence host plant preference, but some of the main factors seem to be secondary plant compounds, water and nutrient c ontent of leaves, and visual cues like the color, size, shape, and texture of the leaves (Chew and Robins 1989). Human caused introductions of closely related plants may present novel, but useful host plants. Since exotic plants did not coevolve with the spec ies in their new environments, they may not have defenses against herbivor es. Butterfly species may thrive on exotics as a result. However, exotics can also confuse butterflies and disrupt their normal behavior. Many butterflies have tightly adapted evolutionary histories to the plants in their habitats, but may respond to cues of exotic s that are similar to their host plants, even if the behavior is maladaptive. I studied the oviposition prefer ence and larval performance of Caligo memnon ( Nymphalidae: Brassolinae) on four potential host plants to determine if ovipositing females select their ovipoition sites in an adap tive manner. In this experiment, three of its major host plants are native, and one is exotic. I hypothesize that there will be a 2

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difference in host plant preference for oviposi tion and that there will be a difference in growth rates for caterpillars feeding on differe nt host plants. Females should prefer to oviposit on plants that result in fast er growth rates for their larval. Methods Natural history of the study system Caligo is one of the largest but terfly genera in the Neot ropics. They are commonly known as Owl butterflies because of the larg e ocelli on their hind wings. The eggs are round and can be laid singly or in clusters (De Vries 1983). Th e exact incubation time for the eggs is unknown, but it is believed that it takes one or two w eeks for the eggs to hatch. The exact number of instars for the la rvae also is unknown, but it is thought that they have six or seven. Host plants Observational studies show that the major host plants of Caligo spp. are in the families Heliconiaceae, Marantaceae, and Musaceae (De Vries 1987). These families share many similarities and belong to the same Order, Zingiberales (Berry and Kress 1991). They all have large and colorful br acht inflorescences and long pe tioles (Stiles 1983). Their leaves are large, stiff, and contain la rge amounts of cellulose. Heliconiaceae and Marantaceae are native to the Neotropics, wh ile Musaceae originated in South East Asia (Vandermeer 1983). Heliconia have very low nutrient valu e and are therefore eaten by only a few herbivores (Stiles 1983). Studies found that Caligo caterpillars that feed on Heliconiaceae grow very slowly. This is thought to be due to a low nitrogen concentration in the leaves (De Vries 1987). I could find no information regarding the nutrient content of Marantaceae and Musaceae. My study involves two species from the 3

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Heliconiaceae family Heliconia latispatha and Heliconia stricta one species from the Marantaceae family, Calathea insignis and one family from the Musacea family, Musa acuminata Study site My experiment was conducted in Monteverde, Costa Rica, in a garden enclosed by a net tent. The garden is used to rear various t ypes of butterflies for the Selvatura Butterfly Garden in Monteverde. The butterflies in th e garden were captured in the Monteverde area and allowed to freely oviposit on plants in the garden. There were approximately fifty female Caligos in the garden at the time of my study. The garden is fumigated every few months to control for pests, and had been fumigated ten days prior to my study. As a result, all the larvae in my study were recently hatched and of similar size. Measuring oviposition preference My project consisted of two experiment s conducted simultaneously. In the first experiment I counted the number of eggs on twenty randomly chosen leaves of each host plant. I did this on seven different days over a twelve-day period, each day choosing twenty leaves randomly. Studies of other butterfly species have shown that there may be preference for individual stalks within a plan t species because of age, phenological stage, condition, or size (Ladner and Altizer 2005). Choosing random leaves eliminated the pattern of preference of butterfli es for certain stalks within a host plant species. I circled the egg clusters with a pen after I counted them, to ensure that I would not recount them on another study day. I also took observations on the placement of eggs on the leaves and the number of eggs in each cluster. 4

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There was not an equal abundance of hos t plants in the garden, giving the butterflies more leaves to choose from for oviposition on certain host plants than others. To correct for this potentially confounding f actor, I counted the number of leaves for each host plant in the garden and took the width and height of ten leaves of each host plant species in order to find th e average leaf size. I did this so that I could compare the number of leaves I found per host plant and th e density of leaf area of each host plant to the actual number of observed eggs per host plant. Larval growth rate and survival In my second experiment I located twenty Caligo caterpillars on each of the potential host plants under study (H. stricta, H. latispatha, C. insigins and M. acuminata). Caterpillars were found on severa l different leaves of each host plant, in groups of one to ten. I labeled all the leaves containing caterpillars in my study as well as the number of caterpillars on it, ensuring that if more caterpillars hatched during my study I would not confuse them with my originals. I measur ed the body length of the caterpillars using a caliper on seven different days over a twelve -day period, and recorded their body lengths. At the end of the experiment I calculated th e average growth and survival rates of the larva for each of the host plants. Results Oviposition preference Females oviposited on all four plants studied. In general, I found eggs in clusters of one to eight, with clusters of three found significan tly more often than th e others (Chi-squared goodness of fit, X2 = 172.845, df = 7, p < 0.001) (tab le 1). I counted a total of 622 eggs 5

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on the four host plants in the garden. I counted 130 eggs on Heliconia stricta leaves, 30 eggs on C. Insignis 335 on M. acuminata leaves, and 127 eggs on H. latispatha. More eggs were deposited on M. acuminata and fewer were deposited on C. Insignis than would have been predicted by chance alone (Chi-squared goodness of fit, X2 = 317.88, df =3, p < 0.001) (figure 1). Heliconia stricta accounted for 38 % of the leaves H. latispatha had 33%, M. acuminata had 21%, and C. Insignis only accounted for 8% of the leaves. M. acuminata was found with many more eggs than would be expected compared to the relative abundance of its l eaves in the garden, and the other three host plants had fewer leaves than would be expected (Chi-squared goodness of fit, X2 = 29.83, df = 3, p < 0.001). M. acuminata had the highest total leaf area in the garden with 55%, followed by H. stricta with 31%, C. Insignis had 8%, and H. latispatha had 5%. M. acumin ata had an egg count that was close to wh at was expected according to its relative leaf area, H. latispatha had more eggs, and H. stricta and C. insignis had significantly fewer eggs than were expected for their re lative leaf area (Chi-s quared goodness of fit, X2 = 243.97, df = 3, p < 0.001 Table 1: Observed clusters of eggs Groups of 1 Groups of 2 Groups of 3 Groups of 4 Groups of 5 Groups of 6 Groups of 7 Groups of 8 32 41 73 42 15 5 1 1 6

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0 50 100 150 200 250 300 350 400 Heliconia stricta Heliconia latispatha Calathea insignis Musa acuminata Caligo memnon host plants Expected if unable to assess size/density Observed Expected if leaf number is important Expected if leaf area is important FIGURE 1 The observed and expected egg di stributions over four host plants. The observed number of eggs on H. stricta was clos e to the expected number that did not take plant abundance or leaf size in the garden in to consideration. However, it was much smaller than would be expected taking these factors into considera tion. H. latispatha showed similar to H. stricta, but its observ ed number of eggs was higher than would be expected according to its leaf area. The obs erved egg number for C. insignis was low for all three expected factors. M. acuminata had many more eggs on them than would be expected by chance alone, and the number of l eaves it had in the garden. However, the observed egg number was close to what would be expected if leaf area was important to the butterflies. Larval growth rate and survival The average change in size for a caterpillar on H. stricta was 13.52 mm, on H. latispatha is was 12.79 mm, for C.insignis it was 11.68 mm, and for M. acuminata it was 5.49 mm (figure 2). This trend s hows that caterpillars have a slower growth rate on M. acuminata. However, statistics do not detect a signifi cant difference in growth rate between M. acuminata and the three othe r host plants (Kolmogorov-Smirnov test M. acuminata vs. H. stricta P = .2034, M. acuminata vs. H. latispatha P > 0.999, M. acuminata vs. C. latispatha is was 12.79 mm, for C.insignis it was 11.68 mm, and for M. acuminata it was 5.49 mm (figure 2). This trend s hows that caterpillars have a slower growth rate on M. acuminata. However, statistics do not detect a signifi cant difference in growth rate between M. acuminata and the three othe r host plants (Kolmogorov-Smirnov test M. acuminata vs. H. stricta P = .2034, M. acuminata vs. H. latispatha P > 0.999, M. acuminata vs. C. 7

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insignis P = .2034). Survival rates s how that caterpillars feeding on H. stricta had a 95% survival rate, on M. acuminata and C. insignis they had a 76% survival rate, and on H. latispatha they had a 70% survival rate. 0 5 10 15 20 25 30 051 0 Time (days) Musa acuminata Heliconia latispatha Heliconia stricta Calathea insignis FIGURE 2. Caterpillar grow th on four host plants. C. insignis H. latispatha, and H. stricta show similar growth rates wi th nearly parallel slopes. M. acuminata shows a possible slower growth rate th an the other three host plants. Discussion Results from the oviposition experiment showed that C. memnon prefer M. acuminata over the other host plants, even though trends show that caterpillars grow slower on this species. T hough there is no statistical diffe rence amongst the growth rates of the larva on the four different host plants, larvae grew more slowly and, over a twelve 8

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day period, they were only half the size of larvae feeding on other plants. The observed number of eggs for M. acuminata was very close to the predicted number of eggs adjusted for relative leaf area. So large leaf area may be an important factor for the butterflies, when choosing to oviposit on M. acuminata. There were fewer eggs on H. stricta than were predicted by all three factors, though larvae grew just as well on it and had the highest survival rate. Females showed a much lower preference for oviposition on C. Insignis than the other three host plants, even though the larv a seemed to grow just as well on it as the two other Heliconia species and better than M. acuminata According to my data it seems the ovipostion behavior of Caligo butterflies is not adaptive to the growth and survival of their la rva. If females where acting in an adaptive manner, they should show a preference for H. stricta because caterpillars had the highest average growth on this species as well as highest survival. Females should be laying the fewest number of eggs on M. acuminata, yet they preferred it over the other three host plants. Marantacea is the most recently derived fa mily in the phylogentic lineage of the Order Zingiberales (Berry and Kress 1991). It may be that C. Memnon has not had as long an evolutionary history with this plant family. Females may have been confused by M. acuminata because it is phylogentically similar to their preferred native host plants in Heliconiaceae, but have not had enough evolutio nary time with the species to realize that it does not facilitate optimum larval growth. Other studies have found similar cases where adult butterf lies preferred to oviposite on exotic species rather than their native host plants even though larval fitness was decreased on the introduced plants. These exotic plants were biochemically similar 9

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to the native hosts, and may have been giving off the same cues to female butterflies (Singer 1989). The introduction of exotic plant species is a potential danger to many ecosystems, often disrupting the interac tions among animals and plants within communities that were formed over long coevolutionary histories (DiTommaso and Losey 2003). Further studies are needed involving a longer study time and a larger sample size to determine if there is a significan t difference in larvae growth rates on Caligo host plants. A study in an environment controlled for pests is needed to determine whether the survival rates found in my experiment are due to the plants or to predators. Also, the larval growth rates of different si zed feeding groups should be studied. Acknowledgements Thanks to Alan for being absolutely fabulous. Te amo. Thanks to Kathy for getting us out of crazy situations and being one of the girls. Tom and Cam, I hope you know how much I appreciated all your help! Karen, your class almost killed me, but I still love you. Thanks to all the boys on our trip for putting up with the girls, there is not many of you, but youre quality. Thanks to the taxi drivers for teaching me dirty words in Spanish. I love my roomies, we are th e fabulous four. Special thanks to everyone on the program, I have learned so much from all of you and I feel honored to have spent four months with so many amazing and weird people. I love each and every one of you. Keep in touch. Literature Cited Berry, F. and Kress J. W. 1991. Heliconia: an identification guide. Smithsonian Institution Press, Washington and London. pp. 30-31. Chew, R.S. and Robbins R.K. 1989. E gg-laying in Butterflies. In: The Biology of Butterflies Vane-Write, R.J. and P.R. Ackery, eds. Princeton University Press, Princeton, NJ, pp. 65-67. 10

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11 De Vries, P.J. 1983. Caligo memnon (Buhito Pardo, Caligo, Cream Owl Butterfly) In: Costa Rican Natural History D. H. Janzen, ed. The University of Chicago Press, Chicago, IL, pp. 703-704. De Vries, P.J. 1987. The Butterflies of Costa Rica and their Natural History Princeton University Press, Princeton, NJ, pp. 245-255. DiTommaso, A. and Losey J. E. 2003. Oviposition preference and larval performance of monarch butterflies ( Danaus plexippus) on two invasive swallow-wort species. Entomologia Experimentalis et Applica, Vol 108, pp. 205-209. Ladner, D. T. and Altizer S. 2005. Oviposition preference and larval performance of North American monarch butterflies on four Asclepias species. Entomologia Experimentalis et Applica, Vol. 116, pp. 9-20. Miller, J.C., D. H. Janzen, and W. Hallwachs. 2006. 100 Caterpillars. The Belknap Press of Harvard University Press, Cambridge, MA, pp. 4-5. Rausher, M.D. 1979. Larval habitat suitablility and ov ipostion preference in three related butterflies. Ecology, Vol. 60, No. 3., pp. 503-511. Singer, M.C. 1989. Butterfly-Hostplant Rela tionships: Host Quality, Adult Choice and Larval Success. In: The Biology of Butterflies Vane-Write, R.J. and P.R. Ackery, eds. Princenton University Press, Princeton, NJ, pp. 81-90. Stiles, F.G. 1983. :Heliconia latispatha (Plantanillo, Wild Plantain). In: Costa Rican Natural History D.H. Janzen, ed. The University of Chicago Press, Chicago, IL, pp. 249-251. Vandermeer, J. 1983. Banana (Platano, Banano). In: Costa Rican Natural History, D. H. J Janzen, ed. The University of Chicago Press, Chicago, IL, pp. 75-76