Browsing by Author "Figueroa, JA"

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    Community-wide germination strategies in a temperate rainforest of Southern Chile: ecological and evolutionary correlates
    (2001) Figueroa, JA; Armesto, JJ
    Delayed seed germination ('dispersal in time'), as a component of a plant's germination strategy, was studied in dicotyledoneous species of a temperate rainforest flora in Chiloe Island (42 degrees 30' S), southern Chile. The objective of this investigation was to assess, for this temperate rainforest flora, what proportion of interspecific variation in the time of seed germination-measured in days since the onset of seed dispersal in space-could be attributed to the plants' historical and phylogenetic background and what proportion was associated with life history and ecological attributes such as seed mass, life form, dispersal syndromes and dispersal periods. To characterise germination times for 44 species from Chiloe forests (n = 150 seeds sowed per species in laboratory assays), we computed the mean germination time (GT), in days since sowing, for all seeds germinated of each species. Seeds were taken from the plants at the onset of dispersal and germinated in Petri dishes at 10/20 degrees C. Considering all species, GTs varied between 3 and 385 days and presented an L-shaped frequency distribution. One-way ANOVAs measured the effects of each factor across all other variables. Two-way ANOVAs were used to assess significant interactions between factors. Multifactorial ANOVAs were used to evaluate the independent effects of each of six historical, phylogenetic and ecological factors on GT and to detect associations between factors. In one-way ANOVAs, phylogenetic grouping (at or above order) explained 12% of the variance in GT; dispersal period (summer v. mainly autumn dissemination of ripe seeds), biogeographic element (endemic, austral, neotropical or cosmopolitan) and dispersal syndrome (fleshy v. dry propagules) explained 7, 6 and 5% of the variance in GT, respectively. The factors life form (trees, shrub and woody vines combined, herbs and non-woody epiphytes) and seed mass (light v. heavy) explained the 4 and 2% of the variance in GT, respectively. Taxa related to Ranunculales presented the longest mean GT (148 days). Endozoochorous species had a more delayed germination than species with other dispersal syndromes. Herbs and non-woody epiphyte species showed mean GT (41 days) significantly shorter than trees and shrubs plus woody vines combined (86 and 85 days, respectively). All interactions in two-way ANOVAs were significant. Multifactorial ANOVAs revealed that the three major factors contributing to differences in GT in this temperate rainforest flora were phylogenetic relatedness, dispersal syndromes and life form (7, 6 and 6% of the interspecific variation, respectively). In this analysis, biogeographic element, dispersal period and seed mass were not significantly related to GT. For the factors examined, failure-time analysis, which takes into account all viable seeds not germinating in laboratory assays, confirmed results from multifactorial ANOVAs.
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    Effects of bird ingestion on seed germination of four woody species of the temperate rainforest of Chiloe island, Chile
    (2002) Figueroa, JA; Castro, SA
    We study the effect of ingestion by birds on seed germination and the consequences of absence of dispersal, with the persistency of the seeds inside the fruit. We collected seeds of four woody species of the temperate rainforest of Chiloe: Gaultheria mucronata, Luma apiculata, Myrteola nummularia, and Myrceugenia planipes. The seeds tested had the following origins: 1) Ingested seeds: seeds collected from the feces of birds, 2) Extracted seeds: seeds obtained directly from the fruits, and 3) Intact fruits: fruits collected directly from the plants. Germination of Myrceugenia planipes under greenhouse conditions, Luma apiculata, and Myrteola nummularia under laboratory conditions, and Gaultheria mucronata under both conditions was analyzed. We found that the seeds reach their maximum germination between 15-20 days after sowing, with the exception of those of G. mucronata sown in the greenhouse, which showed a low germination rate. In the greenhouse assay, seeds of G. mucronata ingested by birds, seeds extracted manually from the fruits, and seeds inside the fruits did not show significant differences in their germination percentages. In the laboratory assays, the seeds of G. mucronata and M. nummularia ingested by birds and the seeds extracted manually from the fruits also did not show any significant difference in germination. Under laboratory conditions, the seeds of L. apiculata ingested by birds presented a statistically greater percentage of germination than the seeds extracted manually. Under greenhouse conditions, seeds of M. planipes ingested by birds did not present a statistically different germination percentage from those seeds extracted from the fruits. The seeds of M. planipes, and L. apiculata inside the intact fruits did not germinate. We conclude that birds do not affect the seed viability of any of the four species studied.
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    Seed germination in temperate rain forest species of southern Chile: chilling and gap-dependency germination
    (2003) Figueroa, JA
    Canopy gap and chilling requirements for seed germination were assessed in 61 and 44 species, respectively, in the temperate rain forest of southern Chile. Germination assays within canopy gap and understorey were carried out under natural conditions. Germination tests in cold stratified and non-stratified seeds were performed under laboratory conditions. Seeds were collected of common trees, shrubs, vines and perennial herbs of forests in southern Chile. Final percent germination was significantly enhanced under canopy gap conditions in 19 species, and significantly reduced in 11 species. Germination proved indifferent under gap vs. understorey conditions in half the species tested. Cold stratification affected germination in 11 species: significantly increasing final germination of four species, and significantly decreasing final percent germination of seven species. A Principal Components Analysis (PCA) was applied with the purpose of identifying groups of species with similar germination strategies. Four attributes were included in the PCA: final germination percentage in canopy gap, germination rate in the laboratory, and gap- and chilling-dependency indices (EGAP and STRAT, respectively). The first axis separated species mainly on EGAP variation while the second axis separated them mainly according to STRAT variation; the two axes together explaining 73% of the among-species variation. A small group of trees and vines germinating best in the understorey and neutral to chilling could clearly be distinguished from the remaining species analyzed. Multifactorial ANOVAs were used for evaluating the combined effect of successional status, seed mass, dispersal period, life form, phylogenetic categories, and dispersal syndrome on EGAP and STRAT variation. The EGAP value of secondary successional species proved significantly greater than that of primary successional species and species with endozoochorous seed dispersal were significantly less dependent on chilling (according to STRAT values) compared to species with mainly wind-dispersed seeds. The possible implications of these results for seedling establishment are discussed.