Spatial and Temporal Variability in Clonal Reproduction of Aechmea magdalenae, a Tropical Understory Herb¹

Abstract

Clonal reproduction is a common feature in tropical herbaceous plants and has been shown to be important for recruitment and population maintenance. Although numerous phenological responses (i.e.,leaf flushing, flowering, and fruit maturation) have been shown to be associated with seasonality in the tropics, little is known about the relationship between seasonality and levels of clonal reproduction. I examined the temporal and spatial variation in clonal reproduction and its potential trade–off with growth and survival for a tropical understory herb, Aechmea magdalenae (André) André ex Baker, Handb. Bromel (Bromeliaceae). I addressed the following questions: (1) how do vegetative growth, survival, and clonal reproduction (i.e., rhizome and ramet production) vary between seasons and between years? (2) how do these factors differ among populations? and (3) do simulated dry and wet season light levels cause similar variation in rosette survival and vegetative and clonal reproduction, as found in natural populations? Rhizome and ramet production in A. magdalenae was found to be highly influenced by seasonality. During the transition from dry to wet season, there was a significant decrease in survival and a significant increase in clonal reproduction, and rosettes tended to grow at a slower rate. Rosettes in the location with the longest dry season had significantly lower survival, higher clonal reproduction, and a slower growth rate. Clonal reproduction also started at smaller rosette sizes in the most seasonal forest. When light levels were manipulated, rhizome and ramet production were significantly greater under the high light conditions, and rosette growth (change in longest leaf length) was significantly lower. Results from this study suggest that A. magdalenae responds to higher light levels by shifting investment from vegetative growth to clonal reproduction. Possible implications of this response to light for population demography are discussed. RESUMES Reproducción clonal es comúnmente encontrada en las especies herbáceas tropicales y ha mostrado ser importance como medio de reclutamiemo y permanencia de la poblaciones. Aunque numerosos eventos fenológicos (producción de hojas, floractión, maduración de frutos) están asociados con las estaciones seca y lluviosa en los trópicos, poco se sabe sobre la relación entre la estacionalidad y la reproducción clonal. En este estudió se examinó la variatión temporal y espacial en la reproductión clonal y su balance con crecimiento y sobrevivencia en Aechmea magdalenae, una especie del sotobosque tropical. Se investingó lo siguiente: (1) cómo varia el cretimiento, la sobrevivientia y la reproducción clonal (productión de rizomas y rametas) entre estaciones y entre años? (2) cómo varian estos factores entre poblaciones? y (3) Pueden niveles de luz que simulan las condiciones en el sotobosque durante la estación seca y lluviosa, causar variaciones en la sobreviventia, crecimiento y reproducción clonal similares a aquellos observados en poblaciones naturales? En ...

Relationships between El Niño Southern Oscillation and Demographic Patterns in a Substitute Food for Collared Peccaries in Panama

“…When fruit production remained well below average levels in 1999, high levels of herbivory were observed for rosettes of all sizes and the A. magdalenae population was reduced to almost half of its original size. The elevated levels of mortality and herbivory in A. magdalenae populations associated with this ENSO event are striking because they contrast starkly with the low rates of mortality that have been reported for this species on BCI (Villegas 2001) and elsewhere (Ticktin 2000) and illustrate the importance of documenting the behavior of plants during environmental fluctuations. For example, Villegas found that mortality rates of large A. magdalenae rosettes from 1991 to 1993 on BCI were under 15 percent (Villegas 2001).…”

“…The elevated levels of mortality and herbivory in A. magdalenae populations associated with this ENSO event are striking because they contrast starkly with the low rates of mortality that have been reported for this species on BCI (Villegas 2001) and elsewhere (Ticktin 2000) and illustrate the importance of documenting the behavior of plants during environmental fluctuations. For example, Villegas found that mortality rates of large A. magdalenae rosettes from 1991 to 1993 on BCI were under 15 percent (Villegas 2001). These rates are consistent with those found during the first year of this study (when there was no herbivory), and are more than four times lower than those found during the second year (when there was herb ivory).…”

“…Rosettes commonly propagate vegetatively through rhizomes, which produce a single ramet at the tip. Aechmea magdalenae is monocarpic and seedlings are rarely found in nature (Brokaw 1983, Villegas 2001Ticktin, pers. obs.…”

“…The 45 percent reduction in population size and the great decrease in the number of large rosettes capable of vegetative and sexual reproduction found in this study can be expected to have an effect on A. magdalenae population dynamics. Research on A. magdalenae population dynamics has shown that the largest stage classes contribute most to population growth, so that increases in their mortality rates have the greatest negative effects on population growth (Ticktin 2000, Villegas 2001). Therefore, periodic decreases associated with collared peccary famine may help keep A. magdalenae populations in check.…”

“…Flowering of A. magdalenae appears to coincide with El Niño events (Villegas 2001;Ticktin, pers. obs.…”