PARENT SESSION
Poster Session #55: Plant-Animal Interactions II.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
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Direct and indirect effects of herbivory on fitness of two sympatric species of Costus.
Sevillano, Lucero*,1, Dirzo, Rodolfo1, Mariano, Néstor*,1, 1 Instituto de Ecología, Universidad Nacional Autónoma de México, Ap. Post. 70275, México, D.F., MEXICO
ABSTRACT- Herbivory and pollination influence plant fitness. The study of their combined effects is limited. Herbivory may have direct and indirect effects on traits associated to pollination. Such effects may limit pollen flow and fruit/seed production. This study assessed natural variation in herbivory, and its effects on pollination and reproductive success of two sympatric species, Costus dirzoii and C. scaber. These species show striking differences in several ecological traits. This allowed us to explore the effects of herbivory in species with contrasting patterns of herbivory and pollination syndromes. The study was carried out at Los Tuxtlas, SE Mexico. We estimated levels and rates of herbivory, growth (no. and height of stalks), and chemical defenses. We also measured flower size and number, nectar production, and pollinator visitation rates and quantified fruit and seed production. We explored the relationship between these characters and intraspecific variation in herbivory. The standing level of damage of C. dirzoii (14.43%) was significantly greater than in C. scaber (5.47%). Mean rate of herbivory was 0.007%/day for C. dirzoii, and 0.0008%/day for C. scaber. Both species also differed significantly in the number (x= -1.78 in C. dirzoii, x= 0.32 in C. scaber), and height (C. dirzoii x= -2.92, C. scaber x= 14.99 cm) of stalks produced in a year. C. dirzoii showed a positive relationship between herbivory and nectar concentration (P<0.04, r2= 0.47) and visitation rate (P<0.002, r2= 0.65,). C. scaber showed a negative relationship between herbivory and mean number of fruits/inflorescence (P<0.04, r2= 0.18). Our results show that direct and indirect effects of herbivory are complex. While in C. scaber herbivory has a negative effect via reduction of fruits per inflorescence, in C. dirzoii it had a positive effect via the increase in nectar production and visitation rate. C. dirzoii may over compensate the negative effects of herbivory.
KEY WORDS: herbivory, pollination, direct and indirect effects on fitness, Costus