Understory herbs are an essential part of tropical rain forests, but little is known about factors limiting their reproduction. Many of these herbs are clonal, patchily distributed, and produce large floral displays of nectar-rich 1-d flowers to attract hummingbird pollinators that may transport pollen over long distances. The aim of this study was to investigate the effects of clonality, cross-proximity, and patchy distribution on the reproduction of the hummingbird-pollinated Amazonian herb Heliconia metallica. We experimentally pollinated flowers within populations with self-pollen and with pollen of different diversity, crossed flowers between populations, and added supplemental pollen to ramets growing solitarily or in conspecific patches. Only flowers pollinated early in the morning produced seeds. Selfed flowers produced seeds, but seed number and mass were strongly reduced, suggesting partial sterility and inbreeding depression after selfing. Because of pollen competition, flowers produced more seeds after crosses with several than with single donor plants. Crosses between populations mostly resulted in lower seed production than those within populations, suggesting outbreeding depression. Ramets in patches produced fewer seeds than solitary ramets and were more pollen-limited, possibly due to geitonogamy and biparental inbreeding in patches. We conclude that high rates of geitonogamy due to clonality and pollen limitation due to the short receptivity of flowers and patchy distribution constrain the reproduction of this clonal herb. Even in unfragmented rain forests with highly mobile pollinators, outbreeding depression may be a widespread phenomenon in plant reproduction.Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp.

Summary 1.Clonal herbs are an important feature of the understorey of Amazonian forests. However, little is known about the environmental drivers determining the population genetics of these herbs and about the spatial scale of gene flow. 2. With amplified fragment length polymorphism markers, we analysed the clonal diversity and genetic structure of a clonal Amazonian herb (Heliconia metallica) in south-eastern Peru at two spatial scales. First, we sampled leaves in 24 patches differing in flooding frequency and canopy openness in 2 km 2 of a floodplain forest, and second in 21 riverine populations from the Andean foothills to the Amazon lowlands along a 550-km stretch of river. 3. At the small spatial scale in the floodplain forest, the clonal diversity of H. metallica was higher at flooded than at non-flooded sites, but clonal diversity did not increase with canopy openness. 4. At the large spatial scale, clonal diversity was very low in riverine populations at up-and downriver sites, suggesting that seedling recruitment was higher at mid-altitudes where the flooding intensity is intermediate. Genetic diversity of riverine populations monotonously increased downriver, indicating unidirectional gene flow mediated by hydrochory. 5. Genetic differentiation among riverine populations was very low (F ST = 0.06) and followed an isolation-by-distance pattern, indicating a stepping-stone type of gene flow by seeds. Despite the much smaller spatial scale, genetic differentiation among patches in the floodplain forest was higher (F ST = 0.16), due to spatially restricted gene flow in the forest understorey. 6. Synthesis. The genetic structure of H. metallica is the result of seedling recruitment being largely limited to flooded sites and of hydrochoric seed dispersal between populations growing on riverbanks. We conclude that river dynamics are the major determinant of the genetic structure of Amazonian plants and that largely undisturbed river systems, such as the Amazon, provide a crucial vector for gene flow, even at large spatial scales.

ResumenPuya raimondii Harms es una especie endémica de la zona altoandina del Perú y Bolivia, distribuida entre 3200 y 4800 m de altitud que sobresale por su gran tamaño y belleza. Es considerada una especie amenazada, por ello la importancia de conocer los factores que afectan la viabilidad y germinación de sus semillas, su único medio de propagación natural. Se colectaron semillas de P. raimondii en 1999 y 2000 de los rodales de Huashta Cruz (distrito Pueblo Libre, departamento Ancash, Perú) y se clasificaron en lotes según sus características externas. Se les determinó la viabilidad (calidad) por el método de tetrazolium y el contenido de humedad. En una selección de 5 lotes se evaluaron el efecto de la luz y la temperatura en la germinación. Se encontró que la viabilidad de las semillas depende de las condiciones a que estuvieron expuestas in situ manifestados por las características externas de las semillas y que se correlaciona con su contenido de humedad, afectando inclusive su apariencia. Las semillas expuestas a la luz presentaron alto poder germinativo (fotoblásticas positivas, requieren luz para germinar). Se encontró que temperaturas mayores a 21 °C afectan negativamente el porcentaje de germinación y el índice de velocidad de germinación.Palabras claves: Puya raimondii, Bromeliaceae, germinación, viabilidad de semilla. AbstractPuya raimondii Harms is an endemic species of the highlands of Peru and Bolivia between 3200 to 4800 m of altitude with noticeable great size and beauty. It is considered threatened species; therefore it is urgent to know the factors that affect its viability and germination of their seeds; aspects focused work presently. The seeds were collected in 1999 and 2000 in Huashta Cruz (Pueblo Libre, Ancash, Peru) and they classified as lots (considering their origin and appearance). They were determined their moisture content and the viability (quality). By means of germination tests, it was evaluated in 5 lots the effect of the light and temperature. The seeds presented different viability which depended on the conditions they were exposed in situ and that it is correlated inversely with its content of humidity, affecting its appearance inclusive. The seeds exposed to the light presented high percentage of germination (positive photoblastics, require light to germinate). Temperatures higher than 21°C had a negative effect in the percentage of germination and germination speed index.Key words: Puya raimondii, Bromeliaceae, germination, seed viability, IntroducciónPuya raimondii Harms (Bromeliaceae) es una especie distribuida en áreas restringidas de los Andes de Perú como rodales entre 3300-4300 m de altitud llegando hasta Bolivia. Esta especie puede vivir en forma vegetativa por más de 40 años antes que se inicie la floración, después de la cual la planta muere (Rivera, 1985). Al florecer, la planta produce (potencialmente) entre 6 a 12 millones de semillas (Rivera, 1985 y Cano et al., 2000 pese a ello su población y área de distribución han ido disminuyendo; debido probablemente a...

ResumenPuya raimondii Harms (Bromeliaceae) es una planta monocárpica que puede producir entre 6 y 12 millones de semillas, sin embargo es muy raro encontrar plántulas en su hábitat natural, lo que significaría la existencia de factores limitantes en el proceso de establecimiento. En el presente trabajo muestra los resultados de experimentos para determinar el sustrato más adecuado para el establecimiento de P. raimondii bajo condiciones de laboratorio. Se comparó la sobrevivencia y vigor de plántulas de P. raimondii en los substratos de turba, musgo, turba-tierra y musgo-tierra. El sustrato turba presentó la mayor supervivencia, mostrando que es el más adecuado para el establecimiento de las plántulas, porque mantiene una humedad adecuada y pH estable lo que permitiría que las plántulas presenten un mayor vigor; los sustratos con muy poca (caso turba-tierra) o demasiada (caso musgo) retención de humedad afectan negativamente su vigor y desarrollo.Palabras clave: Puya raimondii, Bromeliaceae, plántulas, establecimiento de plántulas. AbstractPuya raimondii Harms (Bromeliaceae) is a monocarpic plant, that can produce about 6 to 12 million seeds, nevertheless is very rare to find seedlings in their natural habitat, indicating difficulties for its establishment. In this work, the conditions for establishment of P. raimondii under laboratory conditions were determined carrying out experiments to determine the better substrate. It was compared the survival and vigour of P. raimondii seedling that were transplanted in peat, moss, peat-soil and moss-soil substrates. The peat substrate showed high survival and was better for establishment of seedlings because it maintains steady and suitable humidity and pH conditions, this allowed that seedlings presents a good vigour. Substrates with very little (case peat-earth) or too much (case moss) humidity retention had a negative effect over vigour and development.