I'm a creep, I'm a weirdo
What the hell am I doing here?
I don't belong here.
Radiohead. 1993. "Creep," from the album Pablo Honey. Written by Mike Hazlewood, Albert Hammond, Colin Greenwood, Jonathan Greenwood, Edward O'brien, Philip Selway, and Thomas Yorke.
In 1866 Ernst Haeckel (1834-1919) coined the word "ecology"
1:
"By ecology we mean the body of knowledge concerning the economy of nature—the investigation of the total relations of the animal both to its inorganic and to its organic environment; including above all, its friendly and inimical relations with those animals and plants with which it comes directly or indirectly into contact—in a word ecology is the study of all those complex interrelations referred to by Darwin as the conditions of the struggle for existence."
(Allee et al., 1949, p. vi; see also Stauffer 1957, pp. 140-1412)
Ecology is "the scientific study of how living things interact with each other and their natural environment" (Eco-Globe 2016). There are lots of different kinds of ecology -- population ecology, community ecology, ecosystem ecology, landscape ecology, urban ecology, behavioral ecology, etc.
One thing that becomes apparent when you look at ecology: Except perhaps for the evolutionary ecologists, there's a strong (and somewhat cryptic) tendency to focus on
now. How are animals and plants relating
now. How are ecosystems being affected by people or changes in the environment
now.
Now is not a very long stretch of time. Now is the endpoint, and the journey to now may not have been easy.
In 1982 Daniel Janzen and Paul Martin published a groundbreaking paper: "Neotropical Anachronisms: The Fruits the Gomphotheres Ate" (Janzen and Martin 1982). To summarize: The fruits of numerous tropical and subtropical plants make no real ecological sense -- unless we remember that until about 13,000 years ago there were huge herbivorous animals that roamed the Americas. When the giant ground sloths, mammoths, mastodons, gomphotheres (an elephant relative), glyptodonts,
Mixotodon species, etc. disappeared, all of the plants that had co-evolved with them (by protecting their seeds and leaves from being eaten, or by using these animals to spread their seeds), were suddenly without their partners.
Giant ground sloth (Nothrotheriops shastensis [Shasta ground sloth]).
Drawing of a gomphothere.
Glyptodonts
Mixotodon species.
When we look at New World ecosystems, we are seeing a diminished and impoverished community, a community haunted by specters.
There are many examples: Avocado (
Persea spp.), Papaya (
Carya spp.), Honey locust (
Gleditsia triacanthos), Mesquite (
Prosopis spp.), Osage orange (
Maclura pomifera), Pawpaw (
Asimina triloba) and American Persimmon (
Diospyros virginiana) (see Barlow 2000). All of these have seeds that are
sometimes spread by small mammals (squirrels, gophers, etc.) or
sometimes by larger browsers (deer, pronghorn, etc.), or
occasionally by floods and storms. But mostly the fruit (or seedpod) just falls on the ground and rots. The animals that are supposed to eat them and spread their seeds just aren't there anymore. There are also plants that depend on animals to spread their seeds by hitching a ride, like devil's claw (
Ibicella lutea) and cockleburs (
Xanthium spp.). They too have been waiting for partners who departed long ago.
This idea of ecological anachronisms in the landscape has become important in understanding how plant and animal communities function, and in understanding how introduced species like horses and cows may actually help restore ecosystems -- new "megafauna" to replace the animals that the plants have missed all these centuries.
It got me to wondering -- are there any good examples of "ghosts" here in Southern California? Are there plants or plant communities that are impoverished today because the animals they once largely depended on are now gone?
To begin to answer that question I needed to know two things: First, the kinds of animals and plants that used to be common here during the Pleistocene (which, according to current geological thinking, ended 11,700 years ago). Second, how to determine if a plant is "anachronistic."
The first question is surprisingly easy to answer: There is an excellent source for that kind of knowledge -- The La Brea Tar Pits.
The La Brea tar pits are located in Los Angeles. Natural asphalt bubbles to surface here -- and has been bubbling up for at least 38,000 years. During that time a great many animals and plants have fallen into the tar. Scientists have been excavating and studying the fossils since 1913, and the George C. Page Museum of La Brea Discoveries has been displaying (and more importantly, cataloging) what's been found since 1977.
Their online list of mammals (
http://www.tarpits.org/research-collections/collections/mammal-faunal-list) includes a number of extinct potential megafauna "seed dispersal agents," including
- Ground sloth (Megalonyx jeffersonii)
- Ground sloth (Nothrotheriops shastensis)
- Ground sloth (Glossotherium harlani)
- Mammoth (Mammut americanum)
- Mammoth (Mammuthus columbi)
- Horse (Equus occidentalis)
- Horse (Equus conversidens)
- Tapir (Tapirus californicus)
- Camel (Camelops hesternus)
- Camel (Hemiauchenia macrocephala)
- Bison (Euceratherium collinum)
- Bison (Bison latifrons)
- Bison (Bison antiquus)
Plants that needed megafauna are a little trickier, but using the online listing from the George C. Page Museum (
http://www.tarpits.org/research-collections/collections/flora-list) there are at least four possibilities:
- California black walnut (Juglans californica)
- Spiny hackberry (Celtis ehrenbergiana)3
- California bay laurel (Umbellularia californica)
- Devil's claw (Proboscidea louisianica)4
The second question -- how to determine if a plant is "anachronistic" -- is less easy to answer, but there are 11 criteria spelled out by Janzen and Martin. Their list is quite long and includes many examples. At the risk of oversimplifying, here are their criteria:
- The fruits are big, have pulp that contain sugar or oil, and the fruits do not normally split open to release seeds.
- The fruits are similar to those known from Africa that are spread by large mammals.
- Large nuts or seeds are protected by thick, tough or hard seed coverings that let them pass intact through both the teeth and the digestive tract.
- If the seeds are soft or weak, they are small and embedded in a core or "nut."
- Different species bear ripe fruit at different seasons.
- Many fruits fall off the tree, giving access to small seed-dispersers.
- Fruits do not attract birds, bats or monkeys.
- Most fruit today rots on the ground.
- Small mammals eat the seeds, and are only sometimes dispersal agents.
- Introduced large animals (cows, horses, pigs) like the fruit and disperse the seeds.
- The natural habitats of these plants are on the edges of grasslands or forests, in areas that are attractive to large mammals. (Janzen and Martin 1982, pp. 22-23)
Comparing the mammal and flora list, it seems to me that there are at least a few Southern California species that might "miss the mammoths." Devil's claw (
Proboscidea louisianica) has been shown, fairly persuasively, to be an "evolutionary anachronism": without large animals (horses, bison, etc.) to disperse its seeds, it is confined to limited areas (see Barlow 2000).
Devil's claw (Proboscidea louisianica), dry fruit
California black walnut (
Juglans californica) has been described as "difficult":
"Nothing I have ever done, not winemaking, gardening, big-game hunting, processing acorns or curing olives is as labor-intensive as harvesting, hulling and shelling black walnuts" (Shaw 2010)
It's been observed that there are usually enormous piles of black walnuts to be found at the base of most trees. It is at least possible that California black walnut used to be dispersed by megafauna.
The Rancho Camulos black walnut (Juglans californica), planted about 1860
Black walnuts, just before they start to rot.
Spiny hackberry (
Celtis ehrenbergiana) is in a somewhat different category. Instead of seeking out megafauna to disperse its seeds, it seems to be trying very hard to protect them from mammals. It is the only hackberry in the US that grows spines -- and they are reasonably impressive:
Spiny hackberry (Celtis ehrenbergiana)
Thorns like these would not have discouraged a mammoth (nor would those rather widely spaced thorns be much of a problem for the narrow nose of a pronghorn)-- but they might have been a deterrent to the mouth of a camel or horse.
California bay laurel (
Umbellularia californica) produces seeds that have been compared to miniature avocados. Since avocados are one of the prime examples of an evolutionary anachronism, it's at least reasonable to wonder about it.
Seeds of the California bay laurel (Umbellularia californica), looking very much like miniature avocados.
Though not very large, it's at least possible that California bay laurel employed megafauna as a seed dispersal mechanism (although considering the size, bears, elk, peccaries or maybe even deer could also be seed dispersers). Perhaps it's worth mentioning that the leaves of the California bay laurel are extremely pungent (one might even say overwhelming), which could also be a defense against large leaf-browsers.
Not everything is an example of evolutionary anachronism. Darren Naish has pointed out:
"...it can be all too easy to jump to conclusions about perceptions of co-evolution and we often need to consider other possibilities: plants may grow tall, may grow weird or giant fruit, or may exhibit ‘defensive’ adaptations for reasons unrelated to the presence of their predators, for example, since plants have complex evolutionary interactions all their own. Indeed, some classic alleged examples of co-evolution that supposedly involve lost partners are now thought to be erroneous" (Naish 2013)
The quite plausible theory about the extinction of the Dodo (
Raphus cucullatus) on the island of Mauritius about 1690 and the decline of the tambalacoque tree (
Sideroxylon grandiflorum) has turned out to be wrong (the tambalacoque is doing just fine without dodos to spread their seeds -- see Hershey 2004; Naish 2013; Young 2016). The idea that extinct raptors are responsible for coloration and behavior in New Zealand's birds is considered somewhat dubious today (see Diamond 1990; Naish 2013). To reiterate: Not everything that
might be an anachronism is an anachronism.
It may be a bit melodramatic to say that we are living in a world haunted by ghosts. But it's undeniable that "ecosystems have been truncated or decapitated by the loss of larger animals" (Eisenberg 2010). Perhaps an awareness of the things that were, of the phantoms that shaped our ecosystems, may help us understand how fragile and how precious what we have today really is. Perhaps we might even try preserve what we still have, before it too is lost.
Notes
1In addition to "ecology," Haeckel also coined the terms "anthropogeny," "phylum," "phylogeny," "stem cell," "protista," and "First World War."
2Stauffer notes that "this translation ... is a free rather than a literal rendering, [but] I consider it very faithful to Haeckel's meaning" (1957, p. 141).
3Actually,
Celtis ehrenbergian is not listed, but a closely related species,
C. reticulata, is. Since
C. ehrenbergian is distributed from Arizona to Florida, and south to Argentina, it seems plausible to think that it might have been here in Southern California (at least in desert areas) during the last few thousand years.
4Devil's claw (
Proboscidea louisianica) is not among the flora listed by the George C. Page Museum. However, it is currently found growing in Southern California and is distributed throughout the Southwest, Mexico and most of the US and Canada, so it seems reasonable to include it.
References
Allee, W.C., A.E. Emerson, O. Park, T. Park, and K.P. Schmidt. 1949. Principles of Animal Ecology. Saunders: Philadelphia. Online:
https://archive.org/details/principlesofanim00alle
Barlow, Connie. 2000. The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms. Basic Books: New York.
Barlow, Connie. 2001. Anachronistic fruits and the ghosts who haunt them. Arnoldia 61(2): 14-21. Online:
http://www.thegreatstory.org/anachronistic_fruits/anachronistic_fruits_for_printing.pdf
Bronaugh, Whit. 2010. The Trees That Miss The Mammoths. American Forests. Online:
http://www.americanforests.org/magazine/article/trees-that-miss-the-mammoths/
Diamond, Jared. 1990. Biological effects of ghosts. Nature 345, 769-770. Online:
http://www.sfu.ca/geog315-new/readings/diamond.pdf
Eco-Globe. 2012. Types of ecology. Online:
http://eco-globe.com/types-of-ecology/
Ecology: Origins. Online:
http://science.jrank.org/pages/9045/Ecology-Origins.html
Eisenberg, Cristina. 2010. Living in a Landscape of Fear: How Predators Impact an Ecosystem. Scientific American Blogs. Online:
https://www.scientificamerican.com/article/predators-create-landscape-of-fear/
Guimarães, Paulo R., Mauro Galetti, and Pedro Jordano. 2008. Seed Dispersal Anachronisms: Rethinking the Fruits Extinct Megafauna Ate. PLOS One:
http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0001745
Hershey, David R. 2004. The Widespread Misconception that the Tambalacoque or Calvaria Tree Absolutely Required the Dodo Bird for its Seeds to Germinate. Plant Science Bulletin 50(4): 105-108. Online:
http://botany.org/PlantScienceBulletin/psb-2004-50-4.php
Janzen, Daniel Hunt and Paul S. Martin. 1982. Neotropical Anachronisms: The Fruits the Gomphotheres Ate. Science. Vol. 215 1 January 1982, pp. 19-27. Online:
https://fission.sas.upenn.edu/caterpillar/index.php?action=retrieve&article=Janzen%2C1982anachronisms.pdf
Naish, Darren. 2013. The ‘ghosts’ of extinct birds in modern ecosystems. Scientific American Blogs. Online:
https://blogs.scientificamerican.com/tetrapod-zoology/the-e28098ghostse28099-of-extinct-birds-in-modern-ecosystems/
Ornduff, Robert, Phyllis M. Faber and Todd Keeler-Wolf. 2003. Introduction to California Plant Life. California Natural History Guides number 69. University of California Press: Berkeley and Los Angeles.
Shaw, Hank. 2010. Black walnuts and holiday cheer. Honest food. Online:
http://honest-food.net/2010/12/14/black-walnuts-and-holiday-cheer/
Smith, K. Annabelle. 2013. Why the Avocado Should Have Gone the Way of the Dodo. Smithsonian Magazine. Online:
http://www.smithsonianmag.com/arts-culture/why-the-avocado-should-have-gone-the-way-of-the-dodo-4976527/?no-ist
Stauffer, Robert C. 1957. Haeckel, Darwin, and Ecology. The Quarterly Review of Biology. 32(2): 138-144. Online:
https://www.jstor.org/stable/2816117?seq=1#page_scan_tab_contents
Young, Lauren. 2016. The Scientific Squabble Over the Dodo Tree. Atlas Obscura. Online:
http://www.atlasobscura.com/articles/the-scientific-squabble-over-the-dodo-tree
