Introduction to the Genus Inga
The Genus Inga Mill. (1754) belongs to the Subfamily Mimosoideae tribe Ingeae Benth. (1875) and comprises near 300 species of trees with a strictly Neotropical distribution. Brazil harbors the greatest number of species (near 140 spp.), followed by Peru (92 spp.), Colombia (near 76+ spp.) and Ecuador (75 spp.) (Pennington, 1997). Due to its great number of species, the Genus Inga is subdivided into 14 Taxonomic Sections characterized by shared morphological attributes (Pennington, 1997).
- Pennington, T. D. 1997. The Genus Inga. Botany. The Royal Botanic Gardens, Kew.
General Distribution of the Genus
Neotropical, extending into temperate zones in the North of Mexico and in the South of Uruguay. The distributional range comprises from Durango and Coahuila (aprox. 25 degrees N)in Mexico, to the delta of Rio de la Plata (aprox. 34 degrees S) in Uruguay. The genus is abundant in the pluvial montane forests and in the lowland pluvial forests along the Neotropical humid zone, and occupies habitats from sea level to 3000 m of elevation. Inga is restricted to riparian habitats and in periodically flooded areas, although many species are confined to pluvial forests in non-flooded areas. Inga species occupy humid environments with well drained soils.
- Romero, C. & A. López. 2005. Taxonomía del Género Inga Mill. In: Forero, E. & C. Romero (Eds.). Estudios en Leguminosas Colombianas. Academia Colombiana de Ciencias Exactas, Físicas y Naturales.
Inga look alikes
The genus Inga is generally regarded as very easy to identify within the species of the Neotropical flora. Its characteristic generic morphological uniformity makes it completely unmistakable from other Neotropical tree genera. However, there is one legume species that resembles very closely the morphology of the genus Inga. This legume tree species belongs to the genus Cojoba (which is also a member of the subfamily Mimosoideae as Inga is). The species of Cojoba that very close resembles one of the genus Inga is Cojo rufescens (Cojoba rufescens (Benth.) Britt. & Rose). This species vegetatively resembles very close an Inga species, but although the leaves are simply pinnate and the structure of the flowers is similar, in Cojoba rufescens the legume is dehiscent, moniliform and the interior of the legume valves is deep reddish in color; on the contrary, in Inga the legume is indehiscent, the legume is continuous (not moniliform), and the valves never have red coloration.
Seed and Seed Development
The Inga seed structure is completely distinguishable from other genera of the Mimosoideae. The white, "cotton like", seed coat is produced by the Malpighian cells of the integument, which become an hypertrophied layer (Maumont, 1990). This enlarged, sugar-rich Malpighian cells form the white edible sarcotesta, which is the attractant for many dispersing animals. Germination of Inga seeds need correct conditions of moisture and shade. The seeds usually begin to germinate inside the unopened pod with the splitting of the seed coat followed by the development of a radicle of several centimeters long.
The embryo grows quickly, beginning with the elongation of the radicle and followed by the growth of the cotyledons which become green and photosynthetic. The first pair of leaves often have one pair of pinnae and are opposite, the petiole appears also winged. The leaves that will form later are always arranged spirally. Leaves always have stipules (including the first-formed leaves), and their shape is usually much narrower than that shown by the adult leaves.
- 1. Maumont, S. 1990. Interet taxonomique de l'histologie des teguments seminaux chez les Acacieae et les Ingeae (Leguminosae-Mimosoideae). Thesis, Université Paul Sabatier, Toulouse.
- 2. Pennington, T. D. 1997. The Genus Inga. Botany. Royal Botanic Gardens, Kew.
Chocó-Darién Moist Forests Habitat
This taxon can be found in the Chocó-Darién moist forests ecoregion, one of the most species rich lowland areas on Earth, with exceptional abundance and endemism over a broad range of taxa including plants, birds, amphibians and arthropods. The biological distinctiveness is exceptional, with considerable biodiversity.
There are three principal geomorphologic types in the ecoregion: alluvial plains of recent origin, low mountains formed by the relatively recent dissection of sediments from the Tertiary and Pleistocene periods, and the complexes in mountain areas consisting of mesozoic rocks. The high precipitation and the topography mean that the ecoregion includes a complex of great hydrographic basins, the most important being those of the Atrato, Baudó, and San Juan Rivers and the Micay and Patía Rivers in the south. The force of the water in many of these rivers form deep gorges cutting through the mountains, creating spectacular rapids and waterfalls in the mountains. At lower elevations, large rivers become very wide and with many meanders. Given the high precipitation in the region, it is not surprising that the soils are severely leached and poor in nutrients. Most of the ecoregion has typical laterite soils with reddish clay, although the soils are younger and less leached in some areas, especially close to the base of the Andes and in the floodplains of the major rivers. Of particular botanical interest are the white clay soils in the region of Bajo Calima in Colombia, which are associated with the gigantic sclerophyllous leafed and unusually large fruited vegetation.
Depending on the altitudinal gradient, soil water content and the effect of the sea, there are various types of vegetation that make up the ecoregion. In broad terms, in the northern part of the ecoregion, the lowland rainforests correlate to the Brosimun utilis alliance, including communities dominated by the deciduous Cuipo tree (Cavanillesia platanifolia), the Espavé wild cashew (Anacardium excelsum), the Panamanian rubber tree (Castilla elastica), Brosimum guianense, Bombacopsis spp., Ceiba pentandra, Dipteryx panamensis, and others. In the undergrowth Mabea occidentalis, Clidemia spp., Conostegia spp. and Miconia spp. are abundant. In zones that are occasionally flooded, the Cativo (Prioria copaifera) flourishes as well. In the southern part of the ecoregion, these rainforests have multiple strata, with two layers of trees, lianas, and epiphytes with vigorous growth rates. The number of deciduous plants increases in the north and south, where there is a dry season, particularly near the coast. The forests at higher altitudes, starting at 600 meters, have communities with the following species: Guamos (Inga spp.), Billia columbiana, Brosimum sp., Sorocea spp., Jacaranda hesperia, Pourouma chocoana, Guatteria ferruginea, Cecropia spp., Elaegia utilis, and Brunellia spp.
There are at least 127 species of amphibians in the Choco-Darien, including the following endemic anuran species: Isla Bonita robber frog (Craugastor crassidigitus); Kokoe poison frog (Phyllobates aurotaenia NT), found on western slopes of the Cordillera Occidental , along the Rao San Juan drainage south to the Rao Raposo; Golden poison frog (Phyllobates terribilis EN); La Brea poison frog (Oophaga occultator); Andagoya robber frog (Pristimantis roseus); Antioquia beaked toad (Rhinella tenrec); Atrato glass frog (Hyalinobatrachium aureoguttatum); Blue-bellied poison arrow frog (Ranitomeya minuta); Colombian egg frog (Ctenophryne minor), known only to the in the upper Rao Saija drainage; Condoto stubfoot toad (Atelopus spurrelli VU); Flecked leaf frog (Phyllomedusa psilopygion); LeDanubio robber frog (Strabomantis zygodactylus). An endemic salamander present in the Choco-Darien is the Finca Chibigui salamander (Bolitoglossa medemi VU).
Some other non-endemic anurans found here are: Anatipes robber frog (Strabomantis anatipes); Banded horned treefrog (Hemiphractus fasciatus); Black-legged poison frog (Phyllobates bicolor NT); Horned marsupial frog (Gastrotheca cornuta EN), known for having the largest amphibian eggs in the world; El Tambo stubfoot toad (Atelopus longibrachius EN); Elegant stubfoot toad (Atelopus elegans CR). Endemic caecilians in the ecoregion include the Andagoya caecilian (Caecilia perdita).
There are a number of reptilian taxa within the ecoregion, including: Adorned graceful brown snake (Rhadinaea decorata); the endemic Black centipede snake (Tantilla nigra); Boulenger's least gecko (Sphaerodactylus scapularis VU); the endemic Iridescent ground snake (Atractus iridescens); the endemic Cauca coral snake (Micrurus multiscutatus); the endemic Colombian coral snake (Micrurus spurelli); the endemic Dark ground snake (Atractus melas); the endemic Colombian mud turtle (Atractus melas VU); and the endemic Echternacht's ameiva (Ameiva anomala).
There are 577 species of birds recorded; Tyrannidae is listed as the most diverse avian family, presenting 28 genera and 60 species within the ecoregion. The Choco-Daroemis is a center of avian endemism of the Neotropics; moreover, according to Stattersfield, this ecoregion spans two Endemic Bird Areas, one in Central America and one in South America.
Between these two Endemic Bird Areas there are over sixty restricted range species, including the Chocó tinamou (Crypturellus kerriae VU), Chestnut-mantled Oropendola (Psarocolius cassini EN), Viridian dacnis (Dacnis viguieri), Crested ant-tanager (Habia cristata), Lita woodpecker (Piculus litea), and Plumbeous forest-falcon (Micrastur plumbeus EN). Also to be noted is the presence of the Harpy eagle (Harpia harpyja), the Black and white crowned eagle (Spizastur melanoleucus), taxa increasingly rare in many areas of the Neotropics, and possibly the Speckled antshrike (Xenornis setifrons EN) although one has not been recorded in Colombia since the 1940s.
The region is rich in mammalian taxa, but the larger animals have received inadequate research. These include the Bush dog (Speothos venaticus NT); Chocó tamarin (Saguinus geoffroyi EN), the Baird's Tapir (Tapirus bairdii EN), the Giant anteater (Myrmecophaga tridactyla VU), the Brown-headed spider monkey (Ateles fuscipens CR), the Puma (Puma concolor VU), the Ocelot (Leopardus pardalis LC), and the jaguar (Panthera onca NT).
- C. Michael Hogan & World Wildlife Fund. 2014."Chocó-Darién moist forests". Encyclopedia of Earth, National Council for Science and the Environment, Washington DC ed.Mark McGinley.
- S. D. Davis, V.H. Heywood, O. Herrera-MacBryde, J. Villa-Lobos, and A.C. Hamilton, editors. 1997. Centres of Plant Diversity. A Guide and Strategy for their Conservation. Volume 3: The Americas. World Wildlife Fund and IUCN. ISBN: 283170197X
The genus Inga occupies mainly wet forest habitats. For successful germination the seeds of Inga require shade and high humidity. A few number of known species can occupy semi-arid areas, although they are restricted to temporary or permanent water courses. Within the wet-rainy forests, members of Inga can be found in a variety of niches. They can represent understorey elements as well as properly canopy trees. Many of the known species require high light conditions for development and can be found as a gregarious species. Many others are typically found in secondary forest conditions with high rates of growth and with really large leaves that allow them to success over other competitors. These species in particular prefer poorly drained or periodically inundated areas, swamps, and riverbanks.
- Pennington, T. D. 1997. The Genus Inga. Botany. The Royal Botanic Gardens, Kew.
Dispersal in Inga
The seed coat, the white edible sarcotesta with cotton-like appearance, constitutes the attractant for the dispersing animals (mostly primates). In order to reach to the sweet sarcotesta, dispersers and predators can eat from one of the sides of the pod, thus taking the seeds individually, or they eventually peel the pod from the end tip like a banana. Besides primates, which constitute the main known dispersers of Inga, other animals that could potentially act as a dispersor agents are some species of parrots.
Inga and insects
Different insect taxa represent floral visitors and pollinators for Inga, including 19 families representing 5 orders: Hemiptera, Coleoptera, Diptera, Hymenoptera, and Lepidoptera (Koptur, 1983a). Effective pollinators in Inga are represented by hummingbirds and species of the lepidopteran families Hesperiidae, Sphingidae, and Uranidae.
Up to one third or more of the developing foliage of species of Inga may be eaten by herbivores (Kursar et al. 2009). It has been shown that as high as up to 43 species of Inga may coexist at a single site, and this may in part be explained because species differ considerably in antiherbivore defences, the defences varying independently between the species (Kursar et al. 2009).
- Gallardo, C. F. 1987. Platypus ratzeburgi Chapuis (Coleoptera: Platypodidae): a new pest attacking coffee. J. Agric. Univ. Puerto Rico 11: 335-336.
- Hernandez-Ortiz, V., and R. Perez-Alonso. 1993. The natural host plants of Anastrepha (Diptera: Tephritidae) in a tropical rain forest of Mexico. Fla Entomol. 76: 447-460.
- Koptur, S. 1983a. Flowering phenology and floral biology of Inga (Fabaceae: Mimosoideae). Systematic Botany 8: 354-368.
- Koptur, S. 1983b. Inga (Guaba, Guajiniquil, Caite, Paterno). Pp. 259-261. In: D. H. Janzen, (ed.), Costa Rican Natural History. University of Chicago Press, Chicago.
- Kursar, T. A., K. G. Dexter, J. Lokvam, R. T. Pennington, J. E. Richardson, M. G. Weber, E. T. Murakami, C. Drake, R. McGregor, and P. D. Coley. 2009. The evolution of antiherbivore defenses and their contribution to species coexistence in the tropical tree genus Inga. Proc. National Acad. Sci. U.S.A. 106: 18073-18078.
- Nichols-Orianz, C. M., and J. C. Schultz. 1990. Interactions among leaf toughness, chemistry, and harvesting by attine ants. Ecol. Entomol. 15:311-320.
- Valente, R. D. M., and I. D. S. Gorayeb. 1984. Biology and description of immature forms of Conotrachelus imbecilus Fiedler (Coleoptera: Curculionidae: Molytinae) in Inga heterophylla fruits. Boletin Museu Paraense Emilio Goeldi, N. S., Bot.
Nodulation and Nitrogen Fixation in Inga
Various authors have reported nodulation in several species of Inga (Allen & Allen, 1981; Moreira et al., 1992) as well as effective associations between different Inga species and mycorrhizal fungi. Rhizobial partners have also been found in members of Inga (Allen & Allen, 1939; de Faria, 1995). The mycorrhizal fungi that have been found to be associated with Inga belong to the group endomycorrhizae (Reategui et al., 1995). In many species of Inga nodulation has been reported, but N2-fixation has only been quantified in few of these species (Roskoski and Van Kessel, 1985).
- Allen, O. N., and E. K. Allen. 1939. Root nodule bacteria of some tropical leguminous plants: II. Cross inoculation tests within the cowpea group. Soil Science 47: 63-76.
- Allen, O. N., and E. K. Allen. 1981. The Leguminosae, a source book of characteristics, uses, and nodulation. University of Wisconsin Press. Madison, Wisconsin, USA.
- de Faria, S. M. 1995. Occurrence and rhizobial selection for legume trees adapted to acid soils. Pp. 295-300. In: D. O. Evans and L. T. Szott, (eds.), Nitrogen-fixing trees for acid soils. Proceedings of a workshop held July 3-8, 1994. Turrialba, Costa Rica. Published by the Nitrogen Fixing Tree Association (NFTA), Bangkok, Thailand.
- Moreira, F. M. M., M. F. Silva, and S. M Faria. 1992. Occurrence of nodulation in legume species in the Amazon region of Brazil. New Phytologist 121: 563-570.
- Reategui, A. U., L. T. Szott, and A. Ricse. 1995. Mycorrhizal infection in Inga species from the Peruvian Amazon. Pp. 301-312. In: D. O. Evans and L. T. Szott, (eds.), Nitrogen-fixing trees for acid soils. Proceedings of a workshop held July 3-8, 1994. Turrialba, Costa Rica. Published by the Nitrogen Fixing Tree Association (NFTA), Bangkok, Thailand.
- Roskoski, J. P., and C. Van Kessel. 1985. Annual, seasonal and diel variation in nitrogen fixing activity by Inga jinicuil, a tropical leguminous tree. Oikos 44: 306-312.
Life History and Behavior
Growth and Habit in Inga
Throughout the genus, leaf arrangement and branching pattern appear constant. This pattern agrees to the architectural model of Troll (Halle and Oldeman, 1970), in which all axes are plagiotropic from an early stage. The broad, shallow, horizontal crown typical of Inga members is produced by the distichous phyllotaxis and horizontal growth of the branches. Poncy (1985) discusses with great detail the growth of the young Inga plants.
- Halle, F., and R. A. A. Oldeman. 1970. Essai sur l'architecture et la dynamique de croissance des arbres tropicaux. Masson, Paris.
- Poncy, O. 1985. Le Genre Inga (Legumineuses: Mimosoideae) en Guyane francais. Memoirs du Museum Nationale d'Histoire Naturelle, B., Bot. 31: 1-124.
Evolution and Systematics
Evolution of the Genus Inga
Inga, with near 300+ species constitutes an important component of Neotropical lowland forests. DNA sequence data is consistent with a recent diversification in the Genus (molecular evidence suggests that Inga seems to have diversified within the last two million years, Richardson et al. 2001). Richardson and colleagues (2001) estimated that speciation in Inga had to be concentrated in the past 10 million years, with the bulk of the species arising in the last 2 million years. This chapter of extensive diversification coincides (according to the authors) with relatively recent major geological phenomena, such as uplift of the Andes, the bridging of the Isthmus of Panama, and Quaternary glacial fluctuations.
- Richardson, J. E., R. T. Pennington, T. D. Pennington, and P. M. Hollingsworth. 2001. Rapid Diversification of a Species-Rich Genus of Neotropical Rain Forest Trees. Science 293: 2242-2245.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimen Records: 1011
Specimens with Sequences: 299
Specimens with Barcodes: 289
Species With Barcodes: 69
Public Records: 201
Public Species: 51
Conservation Status of Inga
The Conservation Status of Inga has not been evaluated thoroughly. The IUCN inventory of the global conservation status of species for the Genus Inga has not been addressed yet. Since the status of the some of the widely cultivated species (e.g., Inga edulis) is probably well known, the majority of the species remain poorly known or undercollected and their conservation status remain uncertain for science.
List of Inga species
- Inga adenophylla
- Inga alba
- Inga allenii
- Inga amazonica L.Cardenas
- Inga amboroensis
- Inga andersonii
- Inga approximata
- Inga aptera
- Inga arenicola
- Inga augusti
- Inga balsapambensis
- Inga barbata Benth.
- Inga bella
- Inga bicoloriflora
- Inga bijuga
- Inga blanchetiana
- Inga bollandii
- Inga bracteifera
- Inga bullata
- Inga bullatorugosa
- Inga cabelo
- Inga calantha
- Inga calanthoides
- Inga calcicola
- Inga canonegrensis
- Inga carinata
- Inga caudata
- Inga chiapensis
- Inga coragypsea
- Inga cordistipula Mart.
- Inga cuspidata
- Inga cynometrifolia
- Inga edulis Mart. – Ice-cream-bean (= I. vera Kunth, I. vera sensu Brenan)
- Inga enterolobioides
- Inga exalata T.S.Elias
- Inga exfoliata
- Inga exilis
- Inga extra-nodis
- Inga lacustris
- Inga lanceifolia
- Inga latipes
- Inga laurina (Sw.) Willd. (= I. fagifolia (L.) Benth.)
- Inga lenticellata
- Inga lentiscifolia
- Inga leptantha
- Inga leptingoides
- Inga litoralis
- Inga macarenensis
- Inga macrantha
- Inga maritima
- Inga martinicensis
- Inga megalobotrys
- Inga mendoncaei
- Inga microcalyx
- Inga mortoniana
- Inga mucuna
- Inga multicaulis
- Inga multinervis
- Inga oerstediana Benth.
- Inga pallida
- Inga pedunculata
- Inga platyptera
- Inga pleiogyna
- Inga pluricarpellata
- Inga porcata
- Inga portobellensis
- Inga praegnans
- Inga punctata Willd.
- Inga ruiziana G.Don (= I. fagifolia G.Don)
- Inga saffordiana
- Inga salicifoliola
- Inga saltensis
- Inga santaremnensis
- Inga sapindoides Willd.
- Inga sarayacuensis
- Inga sellowiana
- Inga semialata (Vell.) C. Mart.
- Inga sessilis (Vell.) Mart.
- Inga silanchensis
- Inga sinacae
- Inga skutchii
- Inga spiralis
- Inga stenophylla
- Inga suberosa
- Inga suborbicularis
- Inga vera Willd.
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