Inga Species Research Articles

Diversity and divergence: evolution of secondary metabolism in the tropical tree genus Inga.

Plants are widely recognized as chemical factories, with each species producing dozens to hundreds of unique secondary metabolites. These compounds shape the interactions between plants and their natural enemies. We explore the evolutionary patterns and processes by which plants generate chemical diversity, from evolving novel compounds to unique chemical profiles. We characterized the chemical profile of one-third of the species of tropical rainforest trees in the genus Inga (c. 100, Fabaceae) using ultraperformance liquid chromatography-mass spectrometry-based metabolomics and applied phylogenetic comparative methods to understand the mode of chemical evolution. We show: each Inga species contain structurally unrelated compounds and high levels of phytochemical diversity; closely related species have divergent chemical profiles, with individual compounds, compound classes, and chemical profiles showing little-to-no phylogenetic signal; at the evolutionary time scale, a species' chemical profile shows a signature of divergent adaptation. At the ecological time scale, sympatric species were the most divergent, implying it is also advantageous to maintain a unique chemical profile from community members; finally, we integrate these patterns with a model for how chemical diversity evolves. Taken together, these results show that phytochemical diversity and divergence are fundamental to the ecology and evolution of plants.

Metabolic Profiling of Inga Species with Antitumor Activity.

This work evaluated the metabolic profiling of Inga species with antitumor potential. In addition, we described the antigenotoxicity of polyphenols isolated from I. laurina and a proteomic approach using HepG2 cells after treatment with these metabolites. The in vitro cytotoxic activity against HepG2, HT-29 and T98G cancer cell lines was investigated. The assessment of genotoxic damage was carried out through the comet assay. The ethanolic extract from I. laurina seeds was subjected to bioassay-guided fractionation and the most active fractions were characterized. One bioactive fraction with high cytotoxicity against HT-29 human colon cancer cells (IC50 = 4.0 µg mL−1) was found, and it was characterized as a mixture of p-hydroxybenzoic acid and 4-vinyl-phenol. The I. edulis fruit peel (IC50 = 18.6 µg mL−1) and I. laurina seed (IC50 = 15.2 µg mL−1) extracts had cytotoxic activity against the cell line T98G, and its chemical composition showed a variety of phenolic acids. The chemical composition of this species indicated a wide variety of aromatic acids, flavonoids, tannins, and carotenoids. The high concentration (ranging from 5% to 30%) of these polyphenols in the bioactive extract may be responsible for the antitumor potential. Regarding the proteomic approach, we detected proteins directly related to the elimination of ROS, DNA repair, expression of tumor proteins, and apoptosis.

Species Delimitation of the Atlantic Forest Endemic Inga subnuda (Leguminosae, Caesalpinioideae, Mimosoid Clade) Subspecies Based on Morphological, Ecological, and Palaeoecological Data

Abstract— Inga subnuda is one of 31 Inga species endemic to the Brazilian Atlantic Forest and is currently treated as having two subspecies (I. subnuda subsp. subnuda and I. subnuda subsp. luschnathiana). However, due to intermixed leaf and floral traits, these subspecies are difficult to morphologically distinguish. This study aimed to better understand the boundaries of these two subspecies and to test if these taxa should be treated at the species level. Morphological variation and bioclimatic data related to the two subspecies of the complex were assessed using multivariate morphometric analyses and ecological niche modeling. Different groups were recognized using morphological quantitative characters. The climatic space was similar but not identical, and recent climatic cycles that could have shaped the current distributions of the subspecies are discussed. The results of our integrative study suggest the subspecies are distinct species. Thus, we propose changing the status of I. subnuda subsp. luschnathiana to the rank of species. The new taxon is described and illustrated.

Flora of Espírito Santo: Inga (Fabaceae, Mimosoid clade)

Abstract This study aims to assess the diversity of Inga in the state of Espírito Santo (ES), in order to establish diagnostic characters and circumscription of the species through a detailed analysis of botanical collections. This analysis was based on morphological analysis of specimens collected in the ES and deposited in herbarium collections. The study provides identification keys, descriptions, illustrations, taxonomic comments, geographic distributions, distribution patterns, and phenology data for the species. Twenty-six taxa of Inga were recognized in ES. Of these, 14 (52%) are endemic to Brazil, one of which, Inga teresensis, is restricted to ES. Species of Inga occur predominantly in dense ombrophilous forest (23 taxa), followed by seasonal semideciduous forest (16 taxa), open ombrophilous forest (nine taxa), and pioneer formations (eight taxa). Among dense ombrophilous forests, a higher diversity of Inga species was present in slope forests (22 taxa) than tabuleiro forests (15 taxa). Inga aptera, I. cabelo, I. maritima, I. platyptera, and I. unica are listed as threatened. The distribution of four taxa, I. aptera, I. ciliata subsp. ciliata, I. cylindrica, and I. subnuda var. luschnatiana was extended to ES.

Unraveling relationships of prompt germination among four species of Inga Mill detected by morpho-anatomical and histochemical traits

Seeds are structured with specific morphological attributes that influence their ability to establish new sporophytes in their environments. In this sense, studies of the morphological traits of seeds contribute to the understanding of processes related to the germination, storage and management of plant species. The aim of this study was to characterize the seeds of four species of Inga in terms of biometrics, morphoanatomy and histochemistry. Furthermore, the relationships between these trait variations among Inga species and their impact on seed germination were investigated. The seeds presented high moisture levels, above 40%. I. edulis had 20% viviparity, in contrast to I. cinnamomea, which had 0.1% viviparity. The seeds of I. pezizifera presented more than 50% polyembryony, which influenced seedling vigor. The tegument did not affect the germination percentage. On the other hand, the presence of the tegument influenced the mean germination time for I. cinnamomea, whose seeds with tegument germinated, on average, after 16 days, while the seeds of the other species germinated in 2 to 3 days. Morphologically, the seeds were anatropous, elliptical and exalbuminous. The embryonic axis was well developed and hairy. The tegument was membranous or leathery and caused no physical barrier to germination. However, differences were observed among species in terms of the thickness of the tegument and of the tegument cell walls. In cotyledons and on the embryonic axis, there was a wide distribution of neutral polysaccharides, starches and proteins. Lipids were scarce. Therefore, when taken together, the results concerning Inga seed characteristics contributed to elucidating the factors related to their accelerated and high rates of germination, which reflect their potential for early seedling establishment.

Antifungal and cytotoxicity activities and new proanthocyanidins isolated from the barks of Inga laurina (Sw.) Willd

• Inga laurina is widely found in Brazilian flora. • Phenolic compounds were identified from I. laurina barks by HPLC(–)-ESI-MS/MS. • These compounds showed good antifungal activity (MIC between 23.4–46.8 μg mL −1 ). • Five new compounds of the genus Inga were isolated for the first time. • Proanthocyanidins were isolated and described in the literature for the first time. The Inga genus comprises approximately 300 species that can be found from Mexico to northern Argentina. In folk medicine, Inga species are used to treat various diseases. The species Inga laurina is widely found in the Brazilian flora; however, there are few studies about its biological activity and chemical composition. The main purpose of this study was to identify and isolate the chemical constituents of Inga laurina barks and to evaluate the antifungal and cytotoxic activities. The total content of phenolics, proanthocyanidins, and flavonoids from the barks of Inga laurina were performed by spectrophotometric methods and the ethyl acetate (EAF) and n -butanol (BF) fractions showed the best results. Eleven compounds were identified in EAF by HPLC-ESI(−)-MS/MS, which showed good antifungal activity with MIC values of 23.4 and 46.8 μg mL −1 , evaluated by broth microdilution method. Five new compounds of the genus Inga were isolated for the first time. Three of these compounds were isolated and reported on the literature for the first time: a proanthocyanidin B-type, gallocatechin-(4α→8)-4’- O -methylgallocatechin ( XI ) and two proanthocyanidins A-type, gallocatechin-(2→ O →7,4→8)-4’- O -methylgallocatechin ( XII ) and gallocatechin-3- O -galloyl-(2→ O →7,4→8)-4’- O -methylgallocatechin ( XIII ). The chemical study of the plant bark showed that this species is rich in phenolic compounds and it has great potential for the discovery of new bioactive compounds.

Scientific literature on Inga (Fabaceae) from Santa Catarina state, Southern Brazil (1983-2017)

Inga Mill. belongs to mimosoid clado (Fabaceae, Caesalpinioideae) with 131 species in Brazil. It is the most expressive genus of Fabaceae. This study aimed to perform a bibliometric analysis on Inga from Santa Catarina state. A survey of the published literature was conducted using the electronic databases of the Web of Science, Scopus and Scielo, with the accepted names of Inga species and its synonyms. Papers were distributed in four subject categories: C1 (Ecological), C2 (morphology, anatomy, histology, physiology and genetics), C3 (production and use) and C4 (biochemical and nutritional properties). We registered 232 papers for 13 species of Inga, exhibiting remarkable growth over time. C1 was the most expressive subject category, mainly by nutrient supply, shading and nitrogen fixing capacity. The subjects diversifying over the years, with registered papers in all categories. Inga edulis, I. vera and I. marginata were the most registered species in our survey. We did not find papers on I. edwallii, I. sellowiana and I. vulpina. Our results showed an increase in the number of articles on Inga over time, especially in the last 13 years. However, some important gaps need to be addressed, such as the relatively small number and/or lack of studies conducted for some species.

Photosynthesis, growth, and biomass allocation responses of two Inga species to contrasting light

Inga marginata and Inga subnuda are evergreen N-fixing tree species that are frequently found in the initial stages of forest regeneration. I. marginata has a wide geographic distribution, encompassing the Brazilian Atlantic Rainforest and dry forests of central Brazil, whereas I. subnuda is endemic to the Brazilian Atlantic Rainforest. We conducted this study to compare the physiological, growth, and biomass allocation responses of I. marginata and I. subnuda to contrasting light environments. Considering that I. marginata and I. subnuda have a similar position in the forest succession and different geographic distributions, we tested a hypothesis that these two congeneric species have similar photosynthetic and growth responses to light availability but different biomass allocation. The plants were grown under three light conditions (36, 15, and 6 mol photons m−2 day−1) for 105 days. Growth, biomass allocation, light–response curves, and leaf pigments were compared among the light conditions and between species by using two-way ANOVA. Our hypothesis was partially supported because the two species had similar photosynthetic responses to changes in light availability, but differences in growth and biomass allocation. The higher relative growth rate in mass of I. subnuda is associated with its higher allocation of biomass to light capture, as shown by the higher values of leaf mass fraction (LMF) and leaf area ratio (LAR). Conversely, the higher values of root mass fraction for I. marginata were in contrast to the higher values of LMF, LAR, and specific leaf area for I. subnuda; this indicates that I. marginata should be better adapted to environments where water could be a limiting factor, which is consistent with its wide geographic distribution.

Macroevolutionary patterns in overexpression of tyrosine: An anti‐herbivore defence in a speciose tropical tree genus, Inga (Fabaceae)

Abstract Plant secondary metabolites are a key defence against herbivores, and their evolutionary origin is likely from primary metabolites. Yet for this to occur, an intermediate step of overexpression of primary metabolites would need to confer some advantage to the plant. Here, we examine the evolution of overexpression of the essential amino acid, L‐tyrosine and its role as a defence against herbivores. We examined overexpression of tyrosine in 97 species of Inga (Fabaceae), a genus of tropical trees, at five sites throughout the Neotropics. We predicted that tyrosine could act as an anti‐herbivore defence because concentrations of 4% tyrosine in artificial diets halved larval growth rates. We also collected insect herbivores to determine if tyrosine and its derivatives influenced host associations. Overexpression of tyrosine was only present in a single lineage comprising 21 species, with concentrations ranging from 5% to 20% of the leaf dry weight. Overexpression was pronounced in expanding but not in mature leaves. Despite laboratory studies showing toxicity of L‐tyrosine, Inga species with tyrosine suffered higher levels of herbivory. We therefore hypothesize that overexpression is only favoured in species with less effective secondary metabolites. Some tyrosine‐producing species also contained secondary metabolites that are derived from tyrosine: tyrosine‐gallates, tyramine‐gallates and DOPA‐gallates. Elevated levels of transcripts of prephenate dehydrogenase, an enzyme in the tyrosine biosynthetic pathway that is insensitive to negative feedback from tyrosine, were found only in species that overexpress tyrosine or related gallates. Different lineages of herbivores showed contrasting responses to the overexpression of tyrosine and its derived secondary metabolites in their host plants. Synthesis. We propose that overexpression of some primary metabolites can serve as a chemical defence against herbivores, and are most likely to be selected for in species suffering high herbivory due to less effective secondary metabolites. Overexpression may be the first evolutionary step in the transition to the production of more derived secondary metabolites. Presumably, derived compounds would be more effective and less costly than free tyrosine as anti‐herbivore defences.

A Remarkable New Bifoliolate Species of Inga (Leguminosae) from the Brazilian Atlantic Forest

Abstract We describe and illustrate the new mimosoid legume Inga bifoliolata (Leguminosae) from the highly endangered Brazilian Atlantic Forest domain. The new species is morphologically unique among all Atlantic Forest-inhabiting taxa because of the leaves consistently bearing only two leaflets. Only a few Amazonian Inga species are known to have bifoliolate leaves, yet they are clearly distinct from the new species described herein, which is further characterized by an unwinged leaf petiole and spicate inflorescences on which the sessile flowers are laxly arranged and have puberulous corollas.

Coevolutionary arms race versus host defense chase in a tropical herbivore–plant system

Coevolutionary models suggest that herbivores drive diversification and community composition in plants. For herbivores, many questions remain regarding how plant defenses shape host choice and community structure. We addressed these questions using the tree genus Inga and its lepidopteran herbivores in the Amazon. We constructed phylogenies for both plants and insects and quantified host associations and plant defenses. We found that similarity in herbivore assemblages between Inga species was correlated with similarity in defenses. There was no correlation with phylogeny, a result consistent with our observations that the expression of defenses in Inga is independent of phylogeny. Furthermore, host defensive traits explained 40% of herbivore community similarity. Analyses at finer taxonomic scales showed that different lepidopteran clades select hosts based on different defenses, suggesting taxon-specific histories of herbivore-host plant interactions. Finally, we compared the phylogeny and defenses of Inga to phylogenies for the major lepidopteran clades. We found that closely related herbivores fed on Inga with similar defenses rather than on closely related plants. Together, these results suggest that plant defenses might be more evolutionarily labile than the herbivore traits related to host association. Hence, there is an apparent asymmetry in the evolutionary interactions between Inga and its herbivores. Although plants may evolve under selection by herbivores, we hypothesize that herbivores may not show coevolutionary adaptations, but instead "chase" hosts based on the herbivore's own traits at the time that they encounter a new host, a pattern more consistent with resource tracking than with the arms race model of coevolution.

Genetic diversity and hybridization in the two species Inga ingoides and Inga edulis: potential applications for agroforestry in the Peruvian Amazon

Slash and burn practices affect tropical forests. Our results showed strong introgression between Inga ingoides and Inga edulis in the species contact area. Interspecific hybridization could be sought to improve yield and tolerance to flooding and further increase the economic potential of the poorly drained Amazonian soils and minimize deforestation. Inga species are important components of tropical American forests, as well as a local food source. Little is known about the genetic structure of these species; in particular the amount of introgression among species remains unknown. We assessed the degree of genetic divergence and introgression among populations of I. ingoides (Rich.) Willd. and I. edulis Mart. (Fabaceae) from three Peruvian Amazon tributary rivers. Using microsatellite markers we determined the genetic structure of populations using an analysis of molecular variance and a Bayesian analysis of population structure in areas affected by seasonal river fluctuations and in ‘terra firme’ forests. Overall genetic differentiation was weak. The degree of genetic variation was similar in the two species. A putatively strong introgression was detected between the two species and an intense gene flow was identified among populations. This indicates that an intense gene flow had happened in the past, leading also to a small differentiation among populations within species. Selection of natural hybrids or artificial hybridization between I. edulis and I. ingoides could be applied to improve legume size and yield in the later species, while maintaining tolerance to flooding. Improved I. ingoides could be used in multipurpose agroforestry on open areas along the rivers, instead of using the usual slash and burn practice to create inland open areas.

Rhamnosyl gallates and proanthocyanidins produced by Inga species and their antioxidant and antitumoral potential

Rhamnosyl gallates and proanthocyanidins produced by Inga species and their antioxidant and antitumoral potential

Using targeted enrichment of nuclear genes to increase phylogenetic resolution in the neotropical rain forest genus Inga (Leguminosae: Mimosoideae).

Evolutionary radiations are prominent and pervasive across many plant lineages in diverse geographical and ecological settings; in neotropical rainforests there is growing evidence suggesting that a significant fraction of species richness is the result of recent radiations. Understanding the evolutionary trajectories and mechanisms underlying these radiations demands much greater phylogenetic resolution than is currently available for these groups. The neotropical tree genus Inga (Leguminosae) is a good example, with ~300 extant species and a crown age of 2–10 MY, yet over 6 kb of plastid and nuclear DNA sequence data gives only poor phylogenetic resolution among species. Here we explore the use of larger-scale nuclear gene data obtained though targeted enrichment to increase phylogenetic resolution within Inga. Transcriptome data from three Inga species were used to select 264 nuclear loci for targeted enrichment and sequencing. Following quality control to remove probable paralogs from these sequence data, the final dataset comprised 259,313 bases from 194 loci for 24 accessions representing 22 Inga species and an outgroup (Zygia). Bayesian phylogenies reconstructed using either all loci concatenated or a gene-tree/species-tree approach yielded highly resolved phylogenies. We used coalescent approaches to show that the same targeted enrichment data also have significant power to discriminate among alternative within-species population histories within the widespread species I. umbellifera. In either application, targeted enrichment simplifies the informatics challenge of identifying orthologous loci associated with de novo genome sequencing. We conclude that targeted enrichment provides the large volumes of phylogenetically-informative sequence data required to resolve relationships within recent plant species radiations, both at the species level and for within-species phylogeographic studies.

The generalist Inga subnuda subsp. luschnathiana (Fabaceae): negative effect of floral visitors on reproductive success?

Inga species are characterised by generalist or mixed pollination system. However, this feature does not enhance reproductive rates in species with very low fruit set under natural conditions. Some ecological and genetic factors are associated with this feature, and to test the effect of massive visits on pollination success in Inga subnuda subsp. luschnathiana, we studied the efficacy of polyads deposited on stigmas of flowers isolated from visitors and polyads exposed to visitors. The proportion of polyads fixed in stigmas decreased after exposure to visitors (24h) in comparison to stigmas isolated from visitors (hummingbirds, bees, wasps, hawkmoths and bats), and fruit set was very low. Furthermore, nectar production, sugar composition and other floral biology traits were evaluated. Increased nectar production, sugar availability and sucrose dominance during the night indicates adaptation to nocturnal visitors and supports their role as main pollinators; although the brush-flower morphology, time of anthesis, nectar dynamics and chemical composition also allow daytime visitors. Thus the species is an important resource for a diverse group of floral visitors. We conclude that excess visits (diurnal and nocturnal) are responsible for the decrease in fixed polyads in stigmas of I.subnuda subsp. luschnathiana flowers, thus contributing, with others factors, to its low fruit set. Therefore, the generalist pollination system does not result in reproductive advantages because the low fruit set in natural conditions could be the result of a negative effect of visitors/pollinators.

Anatomical Characteristics of Leaf of Five Species of Family Fabaceae Found in Sinop, MT.

ABSTRACT: It was evaluated the anatomical characteristics of five species of the family Fabaceae (Inga sp.1, Inga cf. marginata Kunth, Inga cf. Cylindrical (Vell.) Mart, and Abarema sp. Inga sp. 2), Found in Bandeiras square in Sinop, Mato Grosso. The material was prepared according to the usual techniques in plant anatomy, analyzed in optical microscope and documented by digital camera coupled to the equipment. All species present epderme uniseriate, epidermal cells with sinuous walls on both sides, paracytic stomata on the abaxial surface, species Abarema sp., Inga cf. cylindrica, Inga sp. 2, Inga cf. marginata showed simple unicellular and uniseriate trichomes, Inga species and an individual sp.1 Inga cf. marginata showed uniseriate, uni-and multicellular trichomes; midrib vascular bundle with bicolateral, parenchyma fill in the adaxial and abaxial collenchyma. Only Abarema sp. presented papillary cells in abaxial; Inga cf. marginata, and Abarema sp. Inga sp1. showed dorsiventral mesophyll; Inga cf. cylindrica and Inga cf. marginata showed isobilateral mesophyll. In conclusion, could separate anatomically species of Inga species Abarema. It could this way help the taxonomy of the group. Keywords: leaf anatomy; anatomical characterization; Fabaceae.

Leaf damage and density-dependent effects on six Inga species in a neotropical forest

Many models have been proposed to explain the possible role of pests in the coexistence of a high diversity of plant species in tropical forests. Prominent among them is the Janzen-Connell model. This model suggests that specialized herbivores and pathogens limit tree recruitment as a function of their density or proximity to conspecifics. A large number of studies have tested the predictions of this model with respect to patterns of recruitment and mortality at different life stages, yet only a few have directly linked those density- or distance-dependent effects to pest attack. If pest-attack is an important factor in density- or distance-dependent mortality, there should be spatial heterogeneity in pest pressure. I studied the spatial distribution of leaf damage in saplings of six common Inga species (Fabaceae: Mimosoideae) in the 50ha forest dynamic plot of Barro Colorado Island, Panama. The percent leaf damage of Inga saplings was not heterogeneous in space, and the density of conspecific, congener or confamilial neighbors was uncorrelated with the observed damage levels in focal plants. One of the focal species did suffer density-dependent mortality, suggesting that spatial variation in plant performance in these species is not directly driven by leaf damaging agents. While multiple studies suggest that density-dependent effects on performance are common in tropical plant communities, our understanding of the mechanisms that drive those effects is still incomplete and the underlying assumption that these patterns result from differential herbivore attack deserves more scrutiny.

Beyond the pollination syndrome: nectar ecology and the role of diurnal and nocturnal pollinators in the reproductive success of Inga sessilis (Fabaceae)

Inga species present brush-type flower morphology allowing them to be visited by distinct groups of pollinators. Nectar features in relation to the main pollinators have seldom been studied in this genus. To test the hypothesis of floral adaptation to both diurnal and nocturnal pollinators, we studied the pollination ecology of Inga sessilis, with emphasis on the nectar secretion patterns, effects of sequential removals on nectar production, sugar composition and the role of diurnal and nocturnal pollinators in its reproductive success. Inga sessilis is self-incompatible and pollinated by hummingbirds, hawkmoths and bats. Fruit set under natural conditions is very low despite the fact that most stigmas receive polyads with sufficient pollen to fertilise all ovules in a flower. Nectar secretion starts in the bud stage and flowers continually secreting nectar for a period of 8 h. Flowers actively reabsorbed the nectar a few hours before senescence. Sugar production increased after nectar removal, especially when flowers were drained during the night. Nectar sugar composition changed over flower life span, from sucrose-dominant (just after flower opening, when hummingbirds were the main visitors) to hexose-rich (throughout the night, when bats and hawkmoths were the main visitors). Diurnal pollinators contributed less than nocturnal ones to fruit production, but the former were more constant and reliable visitors through time. Our results indicate I.sessilis has floral adaptations, beyond the morphology, that encompass both diurnal and nocturnal pollinator requirements, suggesting a complementary and mixed pollination system.

Functional trait divergence of juveniles and adults of nine Inga species with contrasting soil preference in a tropical rain forest

Summary1. Community‐wide studies have shown that functional traits of tropical trees vary with soil‐type preference, but few have examined trait diversification among closely related taxa. In this study, we asked how functional traits of adults and saplings within a speciose genus, Inga, differ in relation to their soil‐type preferences.2. We quantified soil‐type preference and functional traits of nine Inga species (Fabaceae) in the wet tropical forest at La Selva Biological Station, Costa Rica, where rich alluvial soil and less fertile residual soil of volcanic origin occur in close proximity.3. From the extensive trail network, we randomly selected 104 trail segments, each 50 m long, along which all Inga individuals >50 cm tall were counted and identified to species. Five and three common species showed significant bias to residual or alluvial soil, respectively, while the remaining one showed no significant bias. For these nine species, we quantified five leaf traits for saplings and adults, as well as wood‐specific gravity (WSG) and three seed traits.4. For both adults and saplings, leaf mass per area (LMA) and lamina density were higher for residual‐soil specialists than fertile alluvial‐soil specialists. The opposite trend was found for nitrogen (N) and phosphorus (P) concentrations in leaves. Lamina thickness did not differ between soil‐type preference groups. All leaf trait values except N concentration increased from saplings to adults, with adults showing larger interspecific variations in trait values than saplings.5. Saplings and adults of the single species found on both soils had trait values intermediate between residual and alluvial‐soil specialists.6. Seed mass and seed N, as well as WSG of adults, were higher in residual‐soil specialists than alluvial‐soil specialists. Higher seed N indicates higher maternal investment of species growing on less fertile soil.7. These differences in traits among closely related species across continuous soils suggest that habitat filtering has contributed to the evolution of seed, juvenile and adult traits within a speciose tropical tree genus.

Historical effects on beta diversity and community assembly in Amazonian trees.

We present a unique perspective on the role of historical processes in community assembly by synthesizing analyses of species turnover among communities with environmental data and independent, population genetic-derived estimates of among-community dispersal. We sampled floodplain and terra firme communities of the diverse tree genus Inga (Fabaceae) across a 250-km transect in Amazonian Peru and found patterns of distance-decay in compositional similarity in both habitat types. However, conventional analyses of distance-decay masked a zone of increased species turnover present in the middle of the transect. We estimated past seed dispersal among the same communities by examining geographic plastid DNA variation for eight widespread Inga species and uncovered a population genetic break in the majority of species that is geographically coincident with the zone of increased species turnover. Analyses of these and 12 additional Inga species shared between two communities located on opposite sides of the zone showed that the populations experienced divergence 42,000-612,000 y ago. Our results suggest that the observed distance decay is the result not of environmental gradients or dispersal limitation coupled with ecological drift--as conventionally interpreted under neutral ecological theory--but rather of secondary contact between historically separated communities. Thus, even at this small spatial scale, historical processes seem to significantly impact species' distributions and community assembly. Other documented zones of increased species turnover found in the western Amazon basin or elsewhere may be related to similar historical processes.