Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 495489
Title No second chances : Demography from the forest floor to the canopy and back again
Author(s) Balcázar-Vargas, M.P.; Salguero-Gómez, Roberto; Zuidema, P.A.
Source Journal of Ecology 103 (2015)6. - ISSN 0022-0477 - p. 1498 - 1508.
Department(s) Forest Ecology and Forest Management
Publication type Refereed Article in a scientific journal
Publication year 2015
Keyword(s) Amazon forest - Elasticity analysis - Heteropsis - Loop analysis - Matrix population models - Plant demography - Plant population and community dynamics - Secondary hemiepiphytes - Source-sink dynamics - Vegetative reproduction

Secondary hemiepiphytes have one of the most bizarre life histories among vascular plants. They germinate on the forest floor, climb onto a host tree, gradually grow up and start producing seeds if the host tree is taller than the minimum height required for reproductive onset. Because most of the host trees in the forest are too small to allow reproduction, most seedlings of secondary hemiepiphytes of the genus Heteropsis climb onto unsuitable hosts. This problem may be remediated by moving from unsuitable to suitable hosts by vegetative propagation, providing a second chance to contribute to recruitment. Still, such a strategy comes at a demographic risk of increased mortality and may thus contribute little to population growth. Here we ask what are the relative contributions of Heteropsis individuals on suitable vs. unsuitable hosts to their population growth rates (λ). We studied the demography of three species of the genus Heteropsis in the Colombian Amazon, distinguishing subpopulations on suitable and unsuitable hosts. We constructed multistate matrix population models and performed elasticity and loop analyses. For all three Heteropsis species, λ≥1, indicating that studied populations are viable. Vital rates and loop elasticities showed that individuals on suitable hosts contributed 85-98% and 80-96%, respectively. Consequently, individuals that climb directly to suitable hosts predominantly drive the population dynamics of the three studied Heteropsis species and second chances (vegetative reproduction) do not matter for demographic viability. Our results are evidence of a strong source-sink dynamic for the studied species, whereby individuals on unsuitable hosts act as sink subpopulations and individuals on suitable hosts as source subpopulations. The population growth rates of the examined Heteropsis species were strongly limited by recruitment of individuals on suitable hosts and the high proportion of seedlings climbing onto unsuitable hosts, which are demographic 'lost cases'. Synthesis. Our study illustrates a strong environmental filtering and multiple bottlenecks in the life cycle of secondary hemiepiphytes. Our findings contribute with an understudied plant life-history strategy to the extensive repertoire of better-known ecological plant strategies such as tree gap dynamics, clonal reproduction and permanent seedbanks. Secondary hemiepiphytes in the Heteropsis genus germinate on the tropical forest floor and then climb onto a host tree. At first attempt, only few seedlings find a tree that is sufficiently tall to allow development into a reproductive plant. We found that these initially successful individuals drive population growth of three Heteropsis species: second chances hardly contributed to population growth.

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