il ' ii - Northern Research Station - USDA Forest Service

The HR exhibited by the B. brevipes to the galling larvae dissected for observation of their contents, and factors
is easily observed as a brown circular spot around the site associated with mortality recorded and categorized as
of tissue penetration by the larva of Contarinia sp. The parasitism, predation, pathogen attack, hypersensitivity
interactions between B. brevipes and Contarinia sp. : reaction and unknown factors (see Femandes and Price
provide an excellent system to study the effects of 1992). Galls killed by the plant's hypersensitivity could A
induced plant defense on herbivore population dynamics, not be opened because the necrotic reaction fuses the gall "
The HR is easy to identify while Contarinia sp. has all walls. Data were then transformed into percent mortality
the characteristics of galling organisms, which make this and survivorship.
system well suited for population dynamics studies.
Because the subpopulations were not clearly distanded
The goal of this study was to answer the following from each other, we asked whether they would belong to
questions: (a) What is the relative importance of HR a single population. We tested this hypothesis by
against Contarinia sp. galls?; (b) What is the influence verifying if the number of shoots and leaves per shoot
of plant genotype and module growth on the HR of length class differed among subpopulations. The
Bauhinia brevipes against Contarinia sp.?; (c) Do B. frequency distribution of shoots and mean number of
, brevipes show memory after the attack by Contarinia leaves per shoot length class were similar in the three
sp.? subpopulations studied (fig. 1). Short shoots were
abundant while long shoots were rare, and larger shoot
METHODS length classes supported larger number of leaves in all
populations (One-way Anova, p < 0.0001). Since there
System and Area of Study was no difference in the pattern of distribution of shoots
and leaves per shoot length class among the subpopula-
The study was performed in the Estaq_o Ecolrgica de tions studied, we pooled the data into a single data set.
Pirapitinga (IBAMA) in Trrs Marias (MG), southeastern
Brazil between 1995 and 1996. The biological station is Influence of Plant Genotype and Module
. a man-made island, created in 1965 in the Tr_s Marias Length on HR
ReSelwoir (18° 23'S and 45° 20'W) at an altitude of 560
m above sea level. The vegetation of the island is To answer the question "what is the influence of plant
primarily cerrado (savanna) (Azevedo et al. 1987) and B. genotype and module growth on the HR of Bauhinia
brevipes is a leguminous shrub up to 3 meters high and brevipes against Contarinia sp.?" we analyzed the
abundant in the island (Comelissen et al. 1997). proportion of galls killed by natural enemies, plant
resistance, galls successfully formed, and HR reaction
Samples of galls were taken in October of both 1995 and through an ANCOVA test, which allowed us to control
1996 by the end of the galling period. Contarinia sp. for shoot length (continuous variable), while testing for
induces galls on the adaxial leaf surface of B. brevipes, differences between plants and year (categorical vari-
Galls are spherical, with long red hairs coveting their ables) (Zar 1996). Before data analysis with an
external wa!ls and contain a single chamber, with only ANCOVA, we observed whether there was no significant
one larva per chamber (Fernandes 1998, see also interaction between the covariates and independent
Femandes et al. 1988, Gagn6 1994). variables (test of the homogeneity of slopes) (see
SYSTAT 1992). Number of galls and percent HR were
Relative Importance of HR Against used as grouping factors, while shoot length (n = 8,216)
Contarinia sp. Galls was used as the covariate. Data on percent HR we_ arc-
•
sine transformed (Zar 1996).
' Toanswer the question "what is the relative importance u
of HR against Contarinia sp. galls", 25 shoots were Plant Memory
haphazardly collected around the canopy of 170 arbitrarily
selected plants in three subpopulations of B. To answer the question "Do B. brevipes show memory
. brevipes. The subpopulations were located in three after the attack by Contarinia sp.?", we divided the
adjacent trails (subpopulation a = 50 plants, subpopula- studied plants into two arbitrarily chosen categories that
tion b = 60 plants, subpopulation c = 60 plants). We indicate the level of induced resistance to Contarinia sp.
measured the length (to the nearest mm), total number of attack: Resistant plants (> 90 percent HR), Susceptible
leaves, and the number of galled leaves on each of the plants (< 75 percent HR). Plants that felt into the
8,216 sampled shoots. Shoot length was recorded and intermediate level of HR were not considered in the
then transformed into shoot length classes of 3 cm (n = analysis. We then verified the number of plants in each
24 classes), (see Price 1991). To evaluate the mortality category in 1995 and 1996 and the number of plants that
' factors associated with Contarinia sp., galls were moved from one category to another from 1995 to 1996.
145