Neighborhood and community interactions determine the spatial pattern of tropical tree seedling survival

Factors affecting survival and recruitment of 3531 individually mapped seedlings of Myristicaceae were examined over three years in a highly diverse neotropical rain forest, at spatial scales of 1–9 m and 25 ha. We found convincing evidence of a community compensatory trend (CCT) in seedling survival (i.e., more abundant species had higher seedling mortality at the 25-ha scale), which suggests that density-dependent mortality may contribute to the spatial dynamics of seedling recruitment. Unlike previous studies, we demonstrate that the CCT was not caused by differences in microhabitat preferences or life history strategy among the study species. In local neighborhood analyses, the spatial autocorrelation of seedling survival was important at small spatial scales (1–5 m) but decayed rapidly with increasing distance. Relative seedling height had the greatest effect on seedling survival. Conspecific seedling density had a more negative effect on survival than heterospecific seedling density and was stronger and extended farther in rare species than in common species. Taken together, the CCT and neighborhood analyses suggest that seedling mortality is coupled more strongly to the landscape-scale abundance of conspecific large trees in common species and the local density of conspecific seedlings in rare species. We conclude that negative density dependence could promote species coexistence in this rain forest community but that the scale dependence of interactions differs between rare and common species

Seasonality of reproduction in an ever-wet lowland tropical forest in Amazonian Ecuador

We thank Pablo Alvia, Alvaro Pérez, Zornitza Aguilar, Paola Barriga, Matt Priest, Caroline Whitefoord, and Gorky Villa for assistance in collecting data or identifying species; Elina Gomez for entry of trap data; Hugo Navarrete, Katya Romoleroux and the QCA herbarium staff, and David Lasso and the ECY staff for help with logistics and needed permitting; Rick Condit, Elizabeth Losos, Robin Foster, and Henrik Balslev for initial encouragement to work within the Yasuní Forest Dynamics Plot; Hugo Romero for initially summarizing the YFDP and SSP weather data sets; Pablo Jarrin for setting up the TEAM weather station, and David Lasso and Carlos Padilla for maintaining that equipment and making the data available; and the Ecuadorian Ministerio del Ambiente for permission to work in Yasuní National Park [No 014-2019-IC-PNY-DPAO/AVS, No 012-2018-IC-PNY593-DPAO/AVS, No 008-2017-IC-PNY-DPAO/AVS, No 012-2016-IC-FAU-FLO-DPAO-PNY, No 594-014-2015-FLO-MAE-DPAO-PNY, and earlier permits]. The Forest Dynamics Plot of Yasuní National Park has been made possible through the generous support of the Pontifical Catholic University of Ecuador (PUCE) funds of donaciones del impuesto a la renta, the Government of Ecuador, the US National Science Foundation, the Andrew W. Mellon Foundation, the Smithsonian Tropical Research Institute, and the University of Aarhus of Denmark. The phenology project began while NCG was at the Natural History Museum, London, with funding (2000–2004) from the Department of Botany (NHM), the Andrew W. Mellon Foundation, British Airways, and the Natural Environment Research Council (GR9/04037). It continued with NCG at Southern Illinois University Carbondale (2005–2023). We thank the Center for Tropical Forest Science for transitional funding (2006–2008, 2017–2018) and the National Science Foundation LTREB program for long-term funding (2006–2020; DEB-0614525, DEB-1122634, DEB-1754632, DEB-1754668).Peer reviewedPublisher PD

Population genetics of the understory fishtail palm Chamaedorea ernesti-augusti in Belize: high genetic connectivity with local differentiation.

BACKGROUND: Developing a greater understanding of population genetic structure in lowland tropical plant species is highly relevant to our knowledge of increasingly fragmented forests and to the conservation of threatened species. Specific studies are particularly needed for taxa whose population dynamics are further impacted by human harvesting practices. One such case is the fishtail or xaté palm (Chamaedorea ernesti-augusti) of Central America, whose wild-collected leaves are becoming progressively more important to the global ornamental industry. We use microsatellite markers to describe the population genetics of this species in Belize and test the effects of climate change and deforestation on its recent and historical effective population size. RESULTS: We found high levels of inbreeding coupled with moderate or high allelic diversity within populations. Overall high gene flow was observed, with a north and south gradient and ongoing differentiation at smaller spatial scales. Immigration rates among populations were more difficult to discern, with minimal evidence for isolation by distance. We infer a tenfold reduction in effective population size ca. 10,000 years ago, but fail to detect changes attributable to Mayan or contemporary deforestation. CONCLUSION: Populations of C. ernesti-augusti are genetically heterogeneous demes at a local spatial scale, but are widely connected at a regional level in Belize. We suggest that the inferred patterns in population genetic structure are the result of the colonization of this species into Belize following expansion of humid forests in combination with demographic and mating patterns. Within populations, we hypothesize that low aggregated population density over large areas, short distance pollen dispersal via thrips, low adult survival, and low fruiting combined with early flowering may contribute towards local inbreeding via genetic drift. Relatively high levels of regional connectivity are likely the result of animal-mediated long-distance seed dispersal. The greatest present threat to the species is the potential onset of inbreeding depression as the result of increased human harvesting activities. Future genetic studies in understory palms should focus on both fine-scale and landscape-level genetic structure

Seed polyphenols in a diverse tropical plant community

1.Polyphenols are one of the most common groups of secondary metabolites in plants and thought to play a key role in enhancing plant fitness by protecting plants against enemies. Although enemy‐inflicted mortality at the seed stage can be an important regulator of plant populations and a key determinant of community structure, few studies have assessed community‐level patterns of polyphenol content in seeds. 2.We describe the distribution of the main seed polyphenol groups across 196 tree and liana species on Barro Colorado Island (Panama) and community‐level patterns in two aspects of their biological activity (protein precipitation and oxidative capacity). Taking advantage of substantial variation in morphological and ecological traits in the studied plant community, we test for correlations and trade‐offs between seed polyphenols and nonchemical plant traits hypothesised to make plant species more or less likely to invest in polyphenol production. 3.The majority of species have polyphenols in their seeds. The incidence and concentrations of polyphenols were related to a set of nonchemical plant traits. Polyphenols were most likely to be present (and where present, to be expressed in high concentrations) in species with large seeds, short seed dormancy times, low investment in mechanical seed defences, high wood density, high leaf mass per area, tough leaves and slow growth rates. 4.Synthesis. Our study reveals a potential trade‐off between chemical and mechanical seed defences and shows that plant species that invest in physical defences at later life stages (high wood density and tough leaves) tend not to invest in physical defences of seeds but instead produce secondary metabolites likely to act as seed defences. Overall, our results conform to predictions from the resource availability hypothesis, which states that species in resource‐limited environments (such as slow‐growing shade‐tolerant tree species) will invest more in defences than fast‐growing pioneer species. </p

Efecto de la luz y de la escarificación en la germinación de las semillas de cinco especies de árboles tropicales secundarios

We studied the effect of light and scarification of the seed coat on the germination of seeds of five tree species which are characteristic of secondary growth: Apeiba membranacea, A. tibourbou, Luehea seemannii, Trichospermum mexicanum and Guazuma ulmnifolia. The seeds were scarified in sulfuric acid or hot water for 2 or 10 minutes, then germinated in a screened growing house in sunlight and shade.The seeds were not light sensitive. In the controls, germination was very low in both light and shade except in L. seemannii. A requirement for light did not develop after scarification.Scarification increased percent germination in all species by either softening the seed coat or providing a high temperature cue. In L. seemannii, the species with the softest seed coat, hot water increased germination while acid decreased it.Se estudió el efecto de la luz y de la escarificación de la testa en la germinación de las semillas de cinco especies de árboles característicos de sucesión secundaria, Apeiba membranacea, A. tibourbou, Luehea seemannii, Trichospermum mexicanum y Guazuma ulmnifolia. Las semillas se escarificaron con ácido sulfúrico o agua caliente por 2 o 10 minutos y se pusieron a germinar en invernadero bajo condiciones de luz o sombra.Las especies no son fotoblásticas. En los testigos, la germinación fue muy baja en luz y sombra con excepción de L. seemannii. No se desarrolla una necesidad de luz después de la escarificación.La escarificación incrementa el porcentaje de germinación en todas las especies al ablandar la testa o al proveer un indicador de alta temperatura. En L. seemannii, la especie con la testa más suave, el agua caliente incrementa la germinación pero el ácido la disminuye. En las otras especies tanto el agua caliente como el ácido incrementan la germinación

Taxonomic scale-dependence of habitat niche partitioning and biotic neighbourhood on survival of tropical tree seedlings

In order to differentiate between mechanisms of species coexistence, we examined the relative importance of local biotic neighbourhood, abiotic habitat factors and species differences as factors influencing the survival of 2330 spatially mapped tropical tree seedlings of 15 species of Myristicaceae in two separate analyses in which individuals were identified first to species and then to genus. Using likelihood methods, we selected the most parsimonious candidate models as predictors of 3 year seedling survival in both sets of analyses. We found evidence for differential effects of abiotic niche and neighbourhood processes on individual survival between analyses at the genus and species levels. Niche partitioning (defined as an interaction of taxonomic identity and abiotic neighbourhood) was significant in analyses at the genus level, but did not differentiate among species in models of individual seedling survival. By contrast, conspecific and congeneric seedling and adult density were retained in the minimum adequate models of seedling survival at species and genus levels, respectively. We conclude that abiotic niche effects express differences in seedling survival among genera but not among species, and that, within genera, community and/or local variation in adult and seedling abundance drives variation in seedling survival. These data suggest that different mechanisms of coexistence among tropical tree taxa may function at different taxonomic or phylogenetic scales. This perspective helps to reconcile perceived differences of importance in the various non-mutually exclusive mechanisms of species coexistence in hyper-diverse tropical forests

Population genetics of the understory fishtail palm Chamaedorea ernesti-augusti in Belize: high genetic connectivity with local differentiation.

BACKGROUND: Developing a greater understanding of population genetic structure in lowland tropical plant species is highly relevant to our knowledge of increasingly fragmented forests and to the conservation of threatened species. Specific studies are particularly needed for taxa whose population dynamics are further impacted by human harvesting practices. One such case is the fishtail or xaté palm (Chamaedorea ernesti-augusti) of Central America, whose wild-collected leaves are becoming progressively more important to the global ornamental industry. We use microsatellite markers to describe the population genetics of this species in Belize and test the effects of climate change and deforestation on its recent and historical effective population size. RESULTS: We found high levels of inbreeding coupled with moderate or high allelic diversity within populations. Overall high gene flow was observed, with a north and south gradient and ongoing differentiation at smaller spatial scales. Immigration rates among populations were more difficult to discern, with minimal evidence for isolation by distance. We infer a tenfold reduction in effective population size ca. 10,000 years ago, but fail to detect changes attributable to Mayan or contemporary deforestation. CONCLUSION: Populations of C. ernesti-augusti are genetically heterogeneous demes at a local spatial scale, but are widely connected at a regional level in Belize. We suggest that the inferred patterns in population genetic structure are the result of the colonization of this species into Belize following expansion of humid forests in combination with demographic and mating patterns. Within populations, we hypothesize that low aggregated population density over large areas, short distance pollen dispersal via thrips, low adult survival, and low fruiting combined with early flowering may contribute towards local inbreeding via genetic drift. Relatively high levels of regional connectivity are likely the result of animal-mediated long-distance seed dispersal. The greatest present threat to the species is the potential onset of inbreeding depression as the result of increased human harvesting activities. Future genetic studies in understory palms should focus on both fine-scale and landscape-level genetic structure

Morphometric data for PCA analysis

Morphometric data for PCA analysi

Data from: Trema domingensis rises like a phoenix from the ashes of Trema integerrima: a reassessment of the entire-leaved species of Neotropical Trema (Cannabaceae)

We resolve three problems concerning the three entire-leaved species of Neotropical Trema. 1) Phylogenetic and morphological results showed that T. integerrima (Beurl.) Standl., T. domingensis Urb., and T. laxiflora Lundell are a single species; therefore, we combine them under a single name. 2) The date of publication gives priority to T. integerrima, as the basionym Sponia integerrima Beurl. was published in 1856. However, the type specimen, Billberg 308 (S), is not a species of Trema but Pouzolzia obliqua (Wedd.) Wedd. (Urticaceae). The next available name for this species is T. domingensis, published in 1912. 3) The type of T. domingensis, Fuertes 312, is a mixed collection. Specimens of Fuertes 312 held at B, NY, U, and USD are T. domingensis, while those at P, G, US, and Z are Celtis trinervia Lam. We provide a historical review to understand how these problems arose and persisted unnoticed for decades