Browsing by Author "MARTINEZ, E"
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- ItemCAN WE EXTRAPOLATE THE CALIFORNIA MODEL OF GRASSLAND-SHRUBLAND ECOTONE(1993) MARTINEZ, E; FUENTES, EIn California, a number of studies on the interaction between shrubs (Baccharis pilularis) and herbaceous species in annual grasslands have led to the proposal of a conceptual functional model for the dynamics of ecotones between species patches. In our study in Chile we used a similar shrub (Baccharis linearis) and annual grassland species to test the robustness of the hypothesis that ecotones between similar landscape elements under similar climate constraints also have similar dynamics. The herbaceous and shrubby ecotone vegetation was described using cover measurements along the same transects in aerial photographs of 1955, 1962, and 1980, and in the field in 1987. The herbaceous species were then determined and quantified by their mass on both sides of the ecotone. Colonization capacity of B. linearis was estimated by describing its establishment on perturbed sites and estimating its seed dispersion. Field and laboratory experiments evaluated the effect of herbaceous species on shrubs at seedling stages.
- ItemDISTRIBUTION AND ABUNDANCE OF 2 GALL-MAKERS ON THE EUPHORBIACEOUS SHRUB COLLIGUAJA-ODORIFERA(1992) MARTINEZ, E; MONTENEGRO, G; ELGUETA, MPrevious studies on the interaction between the two inflorescence gall-maker insects of the euphorbiaceous shrub Colliguaja odorifera postulated a parasitoid relationship, while effects on shrub reproduction were not addressed.
- ItemEFFECTS OF FILTER-FEEDERS AND GRAZERS ON ALGAL SETTLEMENT AND GROWTH IN MUSSEL BEDS(1988) SANTELICES, B; MARTINEZ, EMacroalgae and mussels are common users of the often limiting primary space on mid- and low-intertidal rocky surfaces. As a result most studies of their interactions have focused primarily on resource competition. Yet, frequently a diversity of algae is found coexisting with mussels.sbd.neither asphyxiating them nor being outcompeted by them. In this study, we look for other sets of ecologically important interactions between mussels and algae in the habitats where they coexist. Experimental studies showed that mussels ingest and digest algal spores, affect the pattern of algal settlement, and protect the algal germlings from desiccation. Probably, they also fertilize the growing thalli. Small grazers among the mussels select the type of algae surviving in the bed and together with the abiotic environment control algal growth and abundance. Reproductive output, antiherbivore escape and defense mechanisms, and tolerance to desiccation appear to be the most important algal adaptations for survival in this type of habitat. The resulting flora found among mussels is a function of all these interactions and of the age and history of the individual mussel bed.
- ItemSIZE HIERARCHY AND THE -3/2 POWER LAW RELATIONSHIP IN A COALESCENT SEAWEED(1992) MARTINEZ, E; SANTELICES, BThe size structure of plant populations has been characterized by two descriptors, size-density relations and size inequality. In even aged natural or experimental populations, the logarithm of mean size is a negative function of population density, with a slope of -3/2 and a maximum intercept of 4.3. Size inequality, measured by the Gini coefficient (G.C.), ranges from maximum size homogeneity (G.C. = 0) to maximum inequality (G.C. = 1). These two descriptors have been applied mainly to land plants, and only once have they been empirically related, suggesting that the onset of self-thinning (increase in mean size by decreasing density) reduces size inequality. We applied these descriptors and tested their empirical relations within populations of Iridaea laminarioides Bory, a red alga that, as other members of the Gigartinales and Gracilariales, exhibits coalescence of germinating spores, forming a clump of fronds with a single basal disc. Results indicate 1) lack of fit to the self-thinning rule and transgression of the limit slope, 2) high size inequality values, 3) absence of a significant negative correlation between mean size and Gini values, 4) spatial ordering in the distribution of size inequality, with fronds decreasing in size towards the periphery of the coalescing discs, and 5) reproduction occurring mostly in the large sized fronds. In I. laminarioides transgression of the self-thinning slope and high size inequality seems to result from spore coalescence and a growth pattern that allows the coalescing discs to grow into physiologically integrated fronds, the larger (and central) of which become reproductive. Therefore, rather than being considered exceptional, we suggest that transgression to the limit slope and high size inequality should be common among seaweeds with coalescing spores and physiological integration of individuals.
- ItemSORUS-SPECIFIC EPIPHYTISM AFFECTING THE KELPS LESSONIA-NIGRESCENS AND L-TRABECULATA (PHAEOPHYTA)(1993) MARTINEZ, E; CORREA, JAThis study characterizes a tissue-specific association between the green algal epiphyte Sporocladopsis sp. and the sori of its kelp hosts, Lessonia nigrescens Bory and L. trabeculata Villouta et Santelices, occurring on the Pacific coast of Chile. The hypothesis that the distribution pattern of the epiphyte was due to constitutive features of the host was assessed by combined field and laboratory observations. Results showed that the epiphyte was confined to sori of L. nigrescens and L. trabeculata, failing to invade adjacent vegetative tissues. Infected hosts were found in northern and central Chile, reaching an incidence of 100 % in low intertidal plants of L. nigrescens, Although important modifications in microtopography develop on the surface of the mature sorus of L. nigrescens, colonization by the epiphyte occurs rather early, on immature sori with only minor surface changes. Thus, microtopographical changes per se do not appear as the only explanation for the observed distributional pattern. The absence of periodical renewal of the outer.cell wall by the reproductive tissue, in contrast with its continous removal in the vegetative tissue, provides a complementary mechanism that explains the restricted distribution of the epiphyte. In the field, growth, reproduction of the epiphyte, and infection of new tissue of L. nigrescens was accomplished in 3 wk. In the laboratory, the epiphyte was successfully isolated, and grew to maturity within 1 mo.
- ItemTHE CONCHOCELIS-PHASE OF PORPHYRA (RHODOPHYTA) IN THE INTERTIDAL OF SAN-JUAN ISLAND, WASHINGTON, USA(1990) MARTINEZ, EA simple method of assessing field abundance of the Conchocelis-phase of Porphyra (Rhodophyta) and of quantifying its abundance within invertebrate shells is described. Working in the intertidal of San Juan Island, Washington, Conchocelis filaments were found within the plates of different barnacle species. Filament density within plates decreased significantly with height on the shore. In the upper shore, filament abundance was lower and showed greater variability than at lower heights. No significant correlation was found between Conchocelis density and cover of the leafy phase of Porphyra perforata J. Agardh, a common species at the site. Results are discussed in terms of the factors that affect Conchocelis abundance and the implications of assessing methods for understanding the ecology of microscopic algal stages.