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Digestion and excretion (pathway cause)

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Datasheet

Digestion and excretion (pathway cause)

Summary

  • Last modified
  • 13 July 2017
  • Datasheet Type(s)
  • Pathway Cause
  • Preferred Scientific Name
  • Digestion and excretion (pathway cause)
  • Overview
  • The digestion and excretion pathway is probably the single most important means for plant dispersal or spread within an area once introduced, established and naturalized. Livestock are common vectors in managed system...

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Identity

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Preferred Scientific Name

  • Digestion and excretion (pathway cause)

International Common Names

  • English: Endochory; Endozoochory
  • Spanish: Digestión/excreción
  • Portuguese: Digestão/excreção

Overview

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The digestion and excretion pathway is probably the single most important means for plant dispersal or spread within an area once introduced, established and naturalized. Livestock are common vectors in managed systems especially grazing land, whereas wild animals, mostly birds and mammals, often play a critical role in natural or semi-natural systems such as forests. However, there are examples where it has been considered as the cause for international introductions, either from the migration of birds or large herbivores, or the long-distance transport of livestock either by ship, or overland.

Description

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Summary of organism types or species introduced

Concerning the animal vectors themselves, most invasions via endozoochoric pathways are by large herbivores or birds, though not exclusively so. Many plants are also dispersed by a variety of organism types, though some have a specialized mutual relation with one animal species or a single organism type. Snails consume and disperse seeds from a few species; earthworms are dispersal agents for many more. Some fish also eat the fruits/seeds of fruits that fall on the water surface and aid in dispersal. There are specialized terms for dispersal by digestion and excretion by specific organism types, such as mammaliochory (by mammals), ornithochory (by birds), saurochory (by reptiles) and chiropterochory (by bats). Humans could also be responsible, as demonstrated by the introduction of the tomato as an invasive species on some uninhabited islets in the Galapagos, as they may have been excreted by visiting researchers (if they were not merely dropped). 

As for the species introduced and/or spread, there are far too many invasive plants that have digestion and excretion as a pathway to list exhaustively; it is estimated that 64% of all gymnosperm species and 27% of all angiosperms produce fruit that attract animals (Traveset et al., 2007). Endozoochory is a widely studied area, but a thorough review of the current state of knowledge would be beneficial, though this may require dividing into manageable sub-units for thoroughness.

Principal processes

The process is, as described in the pathway title, digestion and excretion. However, in addition to the geographic movement of seed by animals, other processes may be advantageous to the plant. The first occurs during digestion, as chemicals and/or physical action are widely reported to break the dormancy of the seeds of many species (Traveset et al., 2007). For example, with the hard-coated seed of leguminous plants, germination percentages may be many times more than the control. The second occurs during excretion, with the increased chance of the seed being placed in a favourable micro-environment, i.e., near to a water source, and being enclosed in a ready source of plant nutrients. 

Geographical routes and corridors

Long-distance introduction would have followed migratory routes (natural), or trade routes, overland livestock movements following grazing and water, or to a port or railhead (human-induced). Local spread could be considered to be random, though may be more prevalent where animals are likely to collect, such as roosts, sources of drinking water, etc. 

Human-mediated history

The only anthropogenic role in digestion and excretion as a pathway involves the raising and movement of domesticated livestock. Long-distance endozoochory is thought to have been responsible for some plant introductions, in livestock transported by ship or overland. However, this has been mainly responsible for the spread of invasive plants on managed and natural grasslands, and extensive grazing land such as steppes, savannas and other dry areas, even deserts. Significant areas in the Americas were invaded by native legume trees in the late 1850s, e.g. Texas and the southwestern USA, and the Chaco of Argentina and Paraguay, when cattle ranching was introduced, disturbing the ecosystem and providing native trees with an environment where they 'densified' into impenetrable monocultures. Many other examples have since been identified, with cattle being the predominant vector, though sheep, goats and camels are also implicated. 

Man has also been indirectly responsible via the introduction of animals into an environment, and which became feral, or naturalized, and these then became vectors for the spread of invasive plants; such as feral pigs, goats and even rabbits and other small mammals, also birds. The invasion of wild fig trees in Australia, which had a restricted range for many decades, is thought to have been triggered by the introduction of the myna bird, which proved to be a very effective dispersal agent. The spread of the fire tree in Hawaii is also considered to be have been induced, but by multiple triggers. Trees had been naturalized for many years, but were few in number, as were feral pigs: the trigger was the introduction and establishment of European earthworms. The pigs now had a sufficient source of food and multiplied, and the ground disturbance from digging for this food provided a very suitable environment for the spread of the fire tree.

Species Transported by Cause

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SpeciesNotesLong DistanceLocalReferences
Acacia auriculiformis (northern black wattle)Seeds are dispersed by birds Yes ,
Acacia crassicarpa (northern wattle) Yes
Acacia glauca (wild dividivi) Yes
Acacia hockii Yes Wickens et al., 1995
Acacia saligna (Port Jackson wattle)Birds Yes Cronk and Fuller, 1995
Aegilops cylindrica Yes Yes
Alyssum desertorum (desert madwort)Seeds eaten by browsing wild and domestic animals Yes Olliff et al., 2001
Ampelopsis arborea (peppervine)Dispersed by bird and mammal droppings Yes Kimbrough, 2008; Titus, 1991
Annona glabra (pond apple) Yes Land Protection, 2005
Aphanomyces astaciExperimental Yes Oidtmann et al., 2002
Ardisia elliptica (shoebutton ardisia) Yes Koop and Horvitz, 2005
Argyreia nervosa (elephant creeper)Seeds dispersed by birds and other animals Yes PIER, 2016
Asparagus asparagoides (bridal creeper)Fruits eaten by birds, rabbits and foxes Yes Graham and Mitchell, 1996; Loyn and French, 1991; Raymond, 1999; Stansbury, 1996; Stansbury, 2001
Asparagus densiflorus (asparagus fern)Fruit eaten by birds Yes
Atriplex semibaccata (Australian saltbush) Yes
Axonopus fissifolius Yes
Bocconia frutescens (plume poppy)Non-native birds frequently consume and disperse seeds within the invaded range Yes Chimera and Drake, 2010; Johnson and Nishida, 2008
Brassica tournefortii (African mustard)Rapidly invades disturbed areas. Yes Berry et al., 2014
Bromus secalinus (rye brome)seeds can pass through animals’ digestive systems Yes ,
Bunias orientalis (Turkish warty-cabbage) Yes Yes
Calliandra houstoniana var. calothyrsus (calliandra) Yes
Canna indica (canna lilly) Yes PIER, 2008
Cassia fistula (Indian laburnum)Seeds survive digestion Yes Yes PIER, 2014
Cassia grandis (pink shower)Animals consume edible pods and excrete the seeds Yes Yes Janzen, 1971
Castilla elastica (Mexican rubber tree)Frugivores eat fruits but cannot consume the seeds so dispersal is through excretion Yes Richard, 2007
Centaurea melitensis Yes Fernàndez and Sàiz, 2007
Centaurea solstitialis (yellow starthistle) Yes
Cinnamomum verum (cinnamon)Birds Yes Kueffer et al., 2009
Clerodendrum indicum (Turk's turban)Berries eaten by birds and animals, seeds dispersed after passing through the gut Yes Yes
Clerodendrum speciosissimum (Java glory bower)Birds eat fruits; propagules survive passage through the gut Yes Yes PIER, 2014
Clerodendrum wallichii (Wallich's glorybower)Species produces seed-bearing fruit which are eaten by birds Yes Yes Rueda, 1993
Clidemia hirta (Koster's curse)Mainly birds Yes Mandon-Dalger et al., 2004
Cornus sericea (redosier dogwood)North America Yes Yes
Cotoneaster horizontalis (wall-spray) Yes Yes
Crassostrea virginica (eastern oyster) Yes Yes
Crataegus monogyna (hawthorn) Yes Bass et al., 2006
Crypsis vaginiflora (African pricklegrass)Waterfowl feed on this plant and may transport seeds throughout their wide distribution. Yes Yes Fleskes et al., 2005
Daphnia lumholtziEphippial transport, possibly in digestive tract of Nile Perch hypothesized as mode of introduction Yes Havel and Hebert, 1993
Delonix regia (flamboyant) Yes Briones-Salas et al., 2006
Descurainia sophia (flixweed) Yes Blackshaw and Rode, 1991
Elaeagnus angustifolia (Russian olive) Yes Katz and Shafroth, 2003
Elaeagnus pungens (thorny olive) Yes Miller, 2003
Elaeagnus umbellata (autumn olive) Yes Munger, 2003
Elaeis guineensis (African oil palm)Probable, but no supporting refs Yes
Eragrostis lehmanniana (Lehmann lovegrass)Used as a forage grass; seeds excreted by livestock remain largely viable Yes Yes PROTA, 2015; Uchytil, 1992
Eugenia uniflora (Surinam cherry) Yes
Festuca arundinacea (tall fescue)Seeds can be transported in animal dung Yes Campbell and Gibson, 2001
Ficus carica (common fig)Where pollinator wasp is persent, seeds can be dispersed by birds and animals which eat the figs Yes Morton, 1987
Ficus elastica (rubber plant)Birds and animals eat the fruit and disperse seeds Yes Yes PIER, 2014
Ficus microcarpa (Indian laurel tree)Seeds of this species are known to be dispersed by over 200 vertebrate species including birds and b Yes Yes Shanahan et al., 2001; Starr et al., 2003
Flacourtia indica (governor's plum)Birds Yes ,
Flemingia strobilifera (wild hops) Yes
Foeniculum vulgare (fennel)Seeds are small and eaten by rodents and birds Yes Cal-IPC, 2015
Globodera pallida (white potato cyst nematode)USA Yes Brodie, 1976
Globodera rostochiensis (yellow potato cyst nematode) Yes
Halogeton glomeratus (halogeton) Yes
Hedychium coccineum (scarlet ginger lily) Yes Henderson, 2003
Hedychium coronarium (white butterfly ginger lily) Yes
Hedychium gardnerianum (kahili ginger) Yes Yes
Hirschfeldia incana (shortpod mustard) Yes South East Natural Resources Management Board, 2009
Hydrilla verticillata (hydrilla) Yes
Hymenachne amplexicaulis (hymenachne)Seed dispersal by native fish in seasonal wetlands of the Pantanal, Brazil; likely waterfowl Yes Yes Australian Weeds Committee, 2012; Silveira and Weiss, 2014
Impatiens glandulifera (Himalayan balsam)by rodents, assumed Yes Beerling and Perrins, 1993
Indigofera tinctoria (true indigo)Said to be eaten by cattle Yes Yes Duke, 1981
Juncus ensifolius (swordleaf rush)Probably transported by waterfowl, deer, livestock Yes Yes Cowan, 1945; Koch, 1991
Lepidium virginicum (Virginian peppercress)Remaining viable in intestinal tract of sea birds. Yes Yes Proctor, 1968
Leucaena leucocephala (leucaena) Yes
Ligustrum lucidum (broad-leaf privet)Seeds are dispersed by birds Yes Aragón and Groom, 2003
Ligustrum sinense (Chinese privet)Birds eat the fruits Yes
Limnocharis flava (yellow bur-head) Yes
Macaranga tanarius (parasol leaf tree)Seed dispersed by birds Yes Yes
Morella faya (firetree)Birds and feral pigs Yes PIER, 2007
Mucuna pruriens (velvet bean)Cultivated as a cover crop and fodder/forage crop; ingested by cattle Yes Yes Duke, 1981
Muntingia calabura (Jamaica cherry)Bats and birds disperse the seeds Yes Yes NAS, 1980
Neonotonia wightii (perennial soybean)Viable seed passed by livestock Yes Gardener et al., 1993a; Gardener et al., 1993b
Opuntia elatior (red-flower prickly pear) Yes
Opuntia engelmannii (cactus apple) Yes
Opuntia ficus-indica (prickly pear) Yes
Opuntia monacantha (common prickly pear) Yes
Opuntia stricta (erect prickly pear)Wild animals, birds Yes
Pandanus tectorius (screw pine) Yes
Pennisetum clandestinum (kikuyu grass)Seeds can be eaten and spread via dung Yes
Phoenix canariensis (Canary Island date palm) Yes DiTomaso and Healy, 2006
Pimenta dioica (allspice)Fruits are eaten by birds, bats and lizards and seeds excreted locally; migratory birds could cause Yes Rodriguez, 1969
Pimenta racemosa (bay rum tree) Yes
Pinus pinaster (maritime pine)Baboons in South Africa Yes Dean et al., 1986
Pittosporum undulatum (Australian cheesewood) Yes Goodland and Healey, 1996
Plectranthus amboinicus (Indian borage)Plectranthus species are used for fodder Yes Yes Lukhoba et al., 2006
Portulaca pilosa (kiss-me-quick) Yes
Potamopyrgus antipodarum (New Zealand mudsnail)Mudsnails are able to survive the pass through the digestive tracts of different fish species Yes Vinson and Baker, 2008
Prosopis glandulosa (honey mesquite)Livestock and wild animals Yes Pasiecznik et al., 2001
Prosopis juliflora (mesquite)Livestock and wild animals Yes Pasiecznik et al., 2001
Rhamphicarpa fistulosaPresumably dispersed by free-grazing cattle Yes
Rhus typhina (staghorn sumac) Yes
Rosa rugosa (rugosa rose) Yes Fremstad, 1997
Rottboellia cochinchinensis (itch grass) Yes Thomas and Allison, 1974
Roystonea oleracea (Caribbean royal palm)Birds and bats Yes Staples et al., 2000; ,
Rubus argutus (sawtooth blackberry)Seeds germinate after passing through digestive systems (e.g., birds) Yes , ; University of Hawaii Botany Department, 2012
Rubus ellipticus (yellow Himalayan raspberry)Birds etc. Yes Jacobi and Warschauer, 1992
Rubus niveus (Mysore raspberry)Birds, mammals and reptiles Yes Buddenhagen and Jewell, 2006
Rytidostylis carthagenensisFruits consumed by birds and small mammals Yes Delascio-Chitty and López, 2007
Salsola kali (common saltwort) Yes
Salsola paulsenii (barbwire Russian thistle) Yes
Schinus terebinthifolius (Brazilian pepper tree)Birds and other wild animals Yes Ferriter and Clark, 1997
Securigera varia (crown vetch)Deer as local and long distance dispersers of the seeds Yes Yes Encyclopedia of Life, 2016
Senna alata (candle bush)Seeds reported as surviving passage through the gut Yes PIER, 2016
Senna occidentalis (coffee senna)Reported as dispersed in livestock dung Yes PIER, 2016
Senna septemtrionalis (smooth senna)Leaves, seeds and shoots are locally eaten as vegetable, and seeds are used as a coffee substitute Yes Hanelt et al., 2001; Sosef and Maesen, 1997
Sesbania sericea (silky sesban)Used as fodder Yes Yes Ipor and Oyen, 1997
Solanum capsicoides (cockroach berry)May be dispersed by cows Yes Markle et al., 2014
Solanum elaeagnifolium (silverleaf nightshade)Benefits from grazing livestock – seed remains viable up to 2 weeks after ingesting Yes Yes EPPO, 2007
Solanum viarum (tropical soda apple) Yes Mullahey et al., 2006
Sporobolus africanus (rat’s tail grass) Yes
Syzygium cumini (black plum) Yes Morton, 1987
Syzygium grande (sea apple)Fruits are eaten by bats, monkeys, and squirrels Yes Ridley, 1894; ,
Ulex europaeus (gorse)Transported by ants, and eaten by quail Yes Chater, 1931
Urtica dioica (stinging nettle) Yes
Ziziphus mauritiana (jujube) Yes Land Protection, 2006

Management

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Controlling the movement of free-ranging livestock and wild mammals is only feasible with high cost and high maintenance fencing, and may only be practical in small and localized cases such as protected areas. Preventing the movement of birds would, of course, be impossible. Eradication of the animal vector would be effective if possible, but the costs on biodiversity are likely to outweigh any benefits in such circumstances and ethical or moral issues would also need considering. 

Quarantine would be the only possible means of reducing the risks associated with human-mediated animal movement, such as the sale of cattle through town markets, international trade in live animals, or the translocation of wild animals such as rogue bull elephants from one reserve to another. Enforcing a quarantine period would ensure that any previously digested seeds are excreted before they are moved into uninfested areas.

Contributors

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6/30/2009 Original text by:

Nick Pasiecznik, Consultant, France