Browsing by Author "FUENTES, ER"

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    2 TYPES OF ADAPTATION OF VERTEBRATE PREDATORS TO THEIR PREY
    (1979) JAKSIC, FM; FUENTES, ER; YANEZ, JL
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    ALLELOPATHIC EFFECTS OF THE CHILEAN MATORRAL SHRUB FLOURENSIA-THURIFERA
    (1987) FUENTES, ER; ESPINOZA, GA; GAJARDO, G
    This paper reports 4 types of evidence of the allelopathic effect of the drought-deciduous shrub Flourensia thurifera (Compositae) on forbs and shrubs. Field evidences include: (1) observed differences in grass abundances at neighboring sites with and without (removed) F. thurifera; (2) measured grass abundances at various distances and directions from isolated F. thurifera shrubs; and (3) the results of experiments in which F. thurifera was cut and the ensuing increment in the relative grass densities monitored. Laboratory evidences pertain to relative germination rates of rye and shrub seeds when irrigated with water in which shrub leaves had been soaked. All four evidences point in the same direction, namely, that F. thurifera produces water-soluble chemical substances capable of inhibiting the germination of other plant species. In addition, the paper supports previous results regarding the lack of demonstrable allelopathic effects in some evergreen species of shrubs. Finally, the ecological significance of these results is discussed.
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    CORRELATES OF TAIL LOSSES IN 12 SPECIES OF LIOLAEMUS LIZARDS
    (1980) JAKSIC, FM; FUENTES, ER
    The relative frequencies of naturally occurring tail losses in 12 spp. of central Chile Liolaemus [L. altissimus, L. chiliensis, L. fuscus, L. lemniscatus, L. leopardinus, L. monticola, L. nigromaculatus, L. nigroviridis, L. nitidus, L. platei, L. schroederi and L. tenuis] are reported. Percentages vary between 23.8-77.2%. In an attempt to explain these differences, percent tail loss was correlated with an estimate of time exposed to predators (size of the lizards), with an estimate of intraspecific susceptibility to predators (sexual dimorphism), and with percent occupation of conspicuous perches. Partial correlation analysis exhibited statistical significance only with the latter variable suggesting that visibility to predators could be causally related to tail losses. Frequency of tail loss is not a measure of predation pressure, but of successful escapes after at least 1 close encounter with a predator.
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    DEFOLIATION PATTERNS IN MATORRAL ECOSYSTEMS
    (1983) FUENTES, ER; ETCHEGARAY, J
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    DITERPENOIDS FROM GRINDELIA-TARAPACANA
    (1995) ZHOU, L; FUENTES, ER; HOFFMANN, JJ; TIMMERMANN, BN
    Seven new and two known diterpenoids, as well as alpha-spinasterol, were isolated from Grindelia tarapacana. The new diterpenoids were fully characterized, on the basis of spectroscopic analysis and chemical evidence, as 14,15-dihydroxy-13-epi-manoyloxide (tarapacol), 15-acetoxy-14-hydroxy-13-epi-manoyloxide (tarapacol 15-acetate), 14,15-diacetoxy-13-epi-manoyloxide (tarapacol diacetate), 11 alpha,14,15-trihydroxy-13-epi-manoyloxide (tarapacanol A), 14,15-diacetoxy-11 alpha-hydroxy-13-epi-manoyloxide (tarapacanol A 14,15-diacetate), 14,15-dihydroxy-11-keto-13-epi-manoyloxide (tarapacanone) and 12 alpha,14,15-trihydroxy-13-epi-manoyloxide (tarapacanol B). The known diterpenoids were identified as 13-epi-manoyloxide and 12 alpha-hydroxy-13-epi-manoyloxide.
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    DOES FIRE INDUCE SHRUB GERMINATION IN THE CHILEAN MATORRAL
    (1989) MUNOZ, MR; FUENTES, ER
    We tested the hypothesis that fire enhances the germination of shrubs of the Chilean evergreen shrublands (matorral), as shown for other areas with Mediterranean-type climates. We did laboratory tests in which we heated seeds for 5 min to 100.degree.C. These results suggest enhancement of germination. However, field measurements and experiments indicated that at depths where the seed bank is located temperatures are high enough to kill all seedlings and there are no places where temperatures are comparable to those usually used in laboratory to verify germination enhancement by high temperatures. These results are discussed in the perspective of selective pressure of fires for the induction of germination in the Chilean matorral species.
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    ECOLOGICAL SPECIES REPLACEMENT OF LIOLAEMUS LIZARDS ALONG A HABITAT GRADIENT
    (1980) FUENTES, ER; JAKSIC, FM
    Ecological species replacement of L. platei by L. lemniscatus may occur along a north-south oriented herb density gradient. Both congeners are the only ground-dwelling lizards in the area; this suggests that L. lemniscatus is an ecological counterpart of L. platei in herbaceous habitats. Relatively longer legs may be associated with the utilization of herb-free habitats by L. platei; the shorter legs possessed by L. lemniscatus are associated with the utilization of habitats of higher herb density. Morphological evidence indicates the presence of intermediate populations in the zone of intermediate herb density. Alternatives of a single-species cline vs. interspecific hybridization between the 2 taxa are discussed.
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    EUROPEAN RABBITS VERSUS NATIVE RODENTS IN CENTRAL CHILE - EFFECTS ON SHRUB SEEDLINGS
    (1983) FUENTES, ER; JAKSIC, FM; SIMONETTI, JA
    The importance of the introduced rabbit Ooryctolagus cunicueus and of the native rodent Octodon degus (= degu) as browsers of shrub seedlings in the central Chilean evergreen shrublands (-matorral) was experimentally assessed. Seedlings were planted in several spatial arrangements in 2 open successional stands and in 2 mature stands of different cover and exposure. The browsing impact of rabbits and degus was evaluated separately after .apprx. 1 yr since the start of the experiments. Degus cause important seedling mortality only within a 5 m-radius centered at the border of their retreats. Rabbits cause heavier seedling mortality, forage more widely and, consequently, have a greater impact than do degus. Rabbits may be halting the secondary succession process, shifting the matorral composition toward less palatable shrub species, and/or broadening the spacing between shrub clumps.
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    EVIDENCE FOR INTRASPECIFIC COMPETITION IN THE ACACIA-CAVEN (LEGUMINOSAE) SAVANNA OF CHILE
    (1979) GUTIERREZ, JR; FUENTES, ER
    In the Chilean savanna, A. caven plants exhibit a spatial distribution pattern in which larger individuals tend to be further apart than smaller individuals of this species. Since published models of interspecific competition in plants do not account for the phenomenon as observed in A. caven, a new model is developed in which root systems of nearest neighbors are allowed to overlap. In these circumstances resources actually available to the plants increase fairly linearly with nearest neighbors distance. The model predicts a positive linear correlation between the sum of squares of the trunk radii of nearest neighbors and the distance separating them. This prediction of the model was tested with A. caven and was able to generate the observed distribution pattern.
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    FRUIT AND SEED CHARACTERISTICS OF WOODY SPECIES IN MEDITERRANEAN-TYPE REGIONS OF CHILE AND CALIFORNIA
    (1989) HOFFMANN, AJ; TEILLIER, S; FUENTES, ER
    The distribution and characteristics of propagules of woody species were compared in four community types along a gradient of increasing annual rainfall, between 30.degree. and 38.degree. latitude in Chile and California. The hypothesis tested was that in these two regions climatic constraints determine similar responses in phylogenetically unrelated organisms. The abundance of fleshy fruits less than 15 mm in diameter (corresponding to the syndrome of bird-dispersal), their sizes, and the frequency of black fruits increased from xeric towards mesic communities, both in Chile and in California; the largest variety of fruit colors was found in the evergreen scrub in both regions. These trends support the convergence hypothesis. In contrast, the distribution and characteristics of wind-dispersed propagules and of "small" dry, not wind-dispersed propagules showed different, apparently non-convergent trends, in Chile and California.
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    GERMINATION RESPONSES AND RESIN PRODUCTION OF GRINDELIA-GLUTINOSA AND G-TARAPACANA FROM THE ATACAMA DESERT
    (1995) CASTRO, SA; FUENTES, ER; TIMMERMANN, BN
    Germination responses and early seedling growth were examined for Grindelia glutinosa and G. tarapacana, two species that preliminary held and laboratory results had suggested could become a new resin crop for the hyper-arid Atacama desert in northern Chile. Initially we examined the germination responses to cold stratification and soil moisture. Stratification inhibited the germination of both species, but mostly of G. tarapacana. Best germination was obtained with about 50% soil moisture levels. Based on these results, we carried out factorial experiments with both species, two levels of nutrients and two levels of soil moisture. Although significant differences were not detected for the growth rate of the species, both benefited from nutrient and humidity additions. Germination rate of G. glutinosa was, in all cases, significantly higher than that observed for G. tarapacana. Resin yields were 17% for G. glutinosa and 26% for G. tarapacana, very high compared with the yields of other species in the genus.
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    HABITAT USE BY 2 RODENT SPECIES IN THE HIGH ANDES OF CENTRAL CHILE
    (1985) SIMONETTI, JA; FUENTES, ER; OTAIZA, RD
    The pattern of habitat use by 2 cricetid rodent species, Akodon andinus and Phyllotis xanthopygus, in the high Andes of central Chile is described. Both rodents are spatially restricted to areas with protective cover (rock outcrops and shrub patches). The rodents partition the refuge areas: P. xanthopygus uses mainly rocks and A. andinus uses mainly shrub patches. Predation probably can account for habitat restriction; interspecific competition appears to explain microhabitat partitioning.
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    INTRASPECIFIC AND INTERSPECIFIC COMPETITION BETWEEN MATORRAL SHRUBS
    (1981) FUENTES, ER; GUTIERREZ, JR
    The model of Gutierrez and Fuentes, which adequately predicted sizes between neighbor distances in the Acacia caven savanna, is applied to the more diverse matorral community of central Chile. The model essentially predicts a positive linear relationship between the sizes of nearest neighbors and the distance separating them. This prediction is tested experimentally by cutting the nearest neighbors of individuals involved in species-pairs of known successional status. The experiments sustain the competition model; matorral shrubs [Lithraea caustica, Quillaja saponaria, Colliguaya odorifera, Muehlenbeckia hastulata, Baccharis rosmarinifolia] compete intra- and interspecifically; and matorral shrubs tested seem to fit into a model of hierarchical competitive dominance in their successional pattern.
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    INTRODUCED SPECIES IN NATURE RESERVES IN MEDITERRANEAN-TYPE CLIMATIC REGIONS OF THE WORLD
    (1988) MACDONALD, IAW; GRABER, DM; DEBENEDETTI, S; GROVES, RH; FUENTES, ER
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    MICROHABITAT USE BY EUROPEAN RABBITS (ORYCTOLAGUS-CUNICULUS) IN CENTRAL CHILE - ARE ADULT AND JUVENILE PATTERNS THE SAME
    (1982) SIMONETTI, JA; FUENTES, ER
    Rabbits (O. cuniculus) were recently introduced to central Chile; adult rabbits were previously reported to exhibit a release in their use of microhabitats due to lack of effective predation upon them. Kittens and juvenile rabbits do not exhibit the same microhabitat use pattern as adults, in spite of the very low predation pressure upon them. Small rabbits are ecologically comparable to native rodents.
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    PEST OUTBREAKS AND RAINFALL IN THE SEMI-ARID REGION OF CHILE
    (1985) FUENTES, ER; CAMPUSANO, C
    The paper has two main objectives: (i) to document rodent and insect outbreaks in the three main agricultural valleys of the semi-arid region of central Chile (30-32.degree. S) and (ii) to attempt to relate these outbreaks of rainfall in these same areas. Rodent and insect outbreaks are documented on the basis of qualitative complaint records by subsistence farmers of the area. Contingency table analysis of standard rainfall data and complaint records show a statistically significant relationship between these variables, for both types of pests. The relation between outbreaks of these wild species in agricultural valleys, primary productivity of the between-valley areas and presumptive movements of those species are discussed, particularly in relation to eventual pest management strategies.
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