Confidential Carnivore

This is a guest post. Words and images by Jeremiah Sandler

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If you live in North America or Europe, chances are you have seen Dipsacus fullonum, commonly called teasel.  Its tall (up to 2 meters), spiky flower stalks with large purple flowers are easy to spot in low-lands, ditches, or along highways.  Since this prolific seeder’s introduction to North America from Europe, it has steadily increased its habitat to occupy nearly each region of the United States. Of course, like all plants, teasel has its preferences and is more frequent in some areas than in others.

dipsacus fullonum_jeremiah sandler

Teasel is an unassuming, herbaceous biennial.  It takes two years to complete its life cycle: First-year growth is spent as a basal rosette, and second-year growth is devoted to flowering.  Standard biennial, right?  As of 2011, an experiment was conducted on this plant that changed the way we see teasel, and possibly all other similar plants.

“Here we report on evidence for reproductive benefits from carnivory in a plant showing none of the ecological or life history traits of standard carnivorous species.” -Excerpt from the report titled Carnivory in the Teasel Dipsacus fullonum — The Effect of Experimental Feeding on Growth and Seed Set by Peter J.A. Shaw and Kyle Shackleton.

We all have favorite carnivorous plants, Venus flytraps, pitcher plants, sundews, etc.. Their showy traps and various means of attracting insects are all marvels of evolution in the plant kingdom.  These insectivorous plants evolved these means of nutrient acquisition in an answer to the lack of nutrients in their environment’s soil.  In some of these plants, there is a direct relationship between number of insects consumed and the size of the entire plant. In others, there is no such relationship.

The unassuming, biennial teasel can now join the ranks of carnivore, or protocarnivore.  It didn’t evolve in bogs or swamps where soil nutrients are depleted.  It has no relationship to the standard carnivorous species. It doesn’t have any flashy traps. In fact, it has no obvious traits which suggest it can gain nutrients from insects. Teasel’s carnivorous habits can be likened somewhat to the carnivorous habits of bromeliads; water gathered in their leaves traps insects.

In Shaw and Shackleton’s experiment (done in two field populations), maggots were placed in water gathered in the center of some first-year rosettes of teasel.  Other rosettes in the same population were left alone as controls.  Not surprisingly, the teasels which were ‘fed’ larvae did not change in overall size.  The size of the overwintering rosette did not offer any predictability towards the size of flower shoots for the coming year. However, something strange did happen:

“…addition of dead dipteran larvae to leaf bases caused a 30% increase in seed set and the seed mass:biomass ratio.”…“These results provide the first empirical evidence for Dipsacus displaying one of the principal criteria for carnivory”

Teasel has some physiology to absorb nutrients from other macroorganisms despite teasel evolving in an entirely different setting than typical carnivorous plants.  Teasel’s already proficient reproductive capacity is enhanced by using insects as a form of nutrients in a controlled setting.  

Many exciting questions have been raised by this experiment. How has this absorption mechanism come about, without the obvious use of lures or other structures to attract insects? And how does teasel maximize upon its own morphology in the wild, if at all?  What would the results be if these experiments were recreated on other similar species?

There are studies being conducted all the time that further the boundaries of what we know about these stationary organisms. There are new discoveries waiting just around the corner. Carnivory in plants is amazing because it transcends common notions about plants; especially in the case of the unassuming teasel.

Selected Resources:

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Jeremiah Sandler lives in southeast Michigan where he works in the plant health care industry. He is currently pursuing a degree in horticulture and an arborist license. He is interested in all things plant related and plans to own a horticulture business where he can share his passion with others. Follow Jeremiah on Instagram: @j4.sandler

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Poisonous Plants: Lima Beans

I don’t recall being a picky eater as a child, but one food I could barely stomach was lima beans. The smell, the texture, the taste, even the look of them, really didn’t sit well with me. I know I’m not alone in this sentiment. Lima beans are a popular thing to hate, and I have avoided them ever since I was old enough to decide what was allowed on my plate. To be fair, the only lima beans I remember trying were the ones included in the familiar bag of frozen mixed vegetables, which might explain why I didn’t like them. But little did I know there is another reason to avoid them – lima beans are poisonous.

That’s a strong statement. In case you’ve eaten lima beans recently or are about to, I should ease your concerns by telling you that you have little to worry about. Commonly cultivated lima beans are perfectly safe to eat as long as they are cooked properly, and even if they are eaten raw in small doses, they are not likely to hurt you. But again, why are you eating lima beans? They’re gross.

lima beans in cans

Phaseolus lunatus – commonly known as lima bean as well as a number of other common names – is in the legume family (Fabaceae) and is native to tropical America. It is a perennial, twining vine that reaches up to 5 meters. It has trifoliate leaves that are alternately arranged, and its flowers are typically white, pink, or purple and similar in appearance to pea flowers and other flowers in the legume family. The fruits are hairy, flat, 5 – 10 cm long, and often in the shape of a half moon. The seeds are usually smooth and flat, but are highly variable in color, appearing in white, off-white, olive, brown, red, black, and mottled.

P. lunatus experienced at least two major domestication events – one in the Andes around 4ooo years ago and the other in Central America more than 1000 years ago. Studies have found that the first event yielded large seeded varieties, and the second event produced medium to small seeded varieties. Wild types of P. lunatus have been given the variety name sylvester, and cultivated types are known as variety lunatus; however, these don’t appear to be accepted names by plant taxonomists and perhaps are just a way of distinguishing cultivated plants from plants growing in the wild, especially in places where P. lunatus has become naturalized such as Madagascar.

Distinguishing wild types from cultivated types is important though, because wild types are potentially more poisonous. Lima bean, like several other plants we eat, contains compounds in its tissues that produce cyanide. These cyanide producing compounds are called cyanogenic glucosides and are present in many species of plants as a form of defense against herbivores. The predominant cyanogenic glucoside in lima beans is called linamarin, which is also present in cassava and flax.

Fruits of lima bean (Phaseolus lunatus) - photo credit: wikimedia commons

Fruits of lima bean (Phaseolus lunatus) – photo credit: wikimedia commons

In order for lima beans to poison you, they must be chewed. Chewing brings linamarin and the enzymes that react with it together. Both compounds are present in the cells of lima beans, but they reside in different areas. Once they are brought together, a reaction ensues and hydrogen cyanide is produced. Because cyanide isn’t produced until after the plant is consumed, the symptoms of cyanide poisoning can take a little while to occur – often several hours.

Cyanide poisoning is not a pretty thing. First comes sweating, abdominal pain, vomiting, and lethargy. If the poisoning is severe, coma, convulsions, and cardiovascular collapse can occur. There are treatments for cyanide poisoning, but if treatment comes too late or if the dose is large enough, death results.

Cassava (Manihot esculenta) is particularly well known for its history of cyanide poisonings. It is a staple crop of people living in tropical areas of Africa and South America. Humans can readily metabolize small amounts of cyanide, and processes like crushing and rinsing, cooking, boiling, blanching, and fermenting render cassava safe to eat. However, consuming cassava that isn’t prepared properly on a consistent basis can result in chronic illnesses, such as konzo, which is a major concern among cultures in which cassava is an important food source.

I guess I should reiterate at this point that most cultivated lima beans contain low (read “safe”) levels of cyanogenic glucosides and, particularly when cooked, are perfectly safe to eat. I’m still not totally convinced that I should eat them though. While researching this article I came across numerous sites claiming that lima beans are delicious while offering various recipes to prove it. I even came across this story in which a self-proclaimed “lima bean loather” was converted to the side of the lima bean lovers. I don’t fancy myself much of a cook, so I’m hesitant to attempt a lima bean laden recipe for fear that it will only make me hate them more. If anyone out there thinks they can convince me otherwise with their tasty creation, be my guest.

And now a haiku:

You are lima beans
I despised you as a child
Perhaps unfairly?

Follow these links to learn more about cyanide producing crops and lima beans:

Book Review: Bringing Nature Home

Since Bringing Nature Home by Douglas Tallamy was first published in 2007, it has quickly become somewhat of a “classic” to proponents of native plant gardening. As such a proponent, I figured I ought to put in my two cents. Full disclosure: this is less of a review and more of an outright endorsement. I’m fawning, really, and I’m not ashamed to admit it.

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The subtitle pretty much sums it up: “How You Can Sustain Wildlife with Native Plants.” Ninety three pages into the book, Tallamy elaborates further: “By favoring native plants over aliens in the suburban landscape, gardeners can do much to sustain the biodiversity that has been one of this country’s richest assets.” And one of every country’s richest assets, as far as I’m concerned. “But isn’t that why we have nature preserves?” one might ask. “We can no longer rely on natural areas alone to provide food and shelter for biodiversity,” Tallamy asserts in the Q & A portion of his book. Humans have altered every landscape – urban, suburban, rural, and beyond – leaving species of all kinds threatened everywhere. This means that efforts to protect biodiversity must occur everywhere. This is where the You comes in. Each one of us can play a part, no matter how small. In closing, Tallamy claims, “We can each make a difference almost immediately by planting a native nearby.”

A plant is considered native to an area if it shares a historical evolutionary relationship with the other organisms in that area. This evolutionary relationship is important because the interactions among organisms that developed over thousands, even millions, of years are what define a natural community. Thus, as Tallamy argues, “a plant can only function as a true ‘native’ while it is interacting with the community that historically helped shape it.” A garden designed to benefit wildlife and preserve biodiversity is most effective when it includes a high percentage of native plants because other species native to the area are already adapted to using them.

Plants (and algae) are at the base of every food chain – the first trophic level – because they produce their own food using the sun’s energy. Organisms that are primarily herbivores are at the second trophic level, organisms that primarily consume herbivores are at the third trophic level, and so on. As plants have evolved they have developed numerous defenses to keep from being eaten. Herbivores that evolved along with those plants have evolved the ability to overcome those defenses. This is important because if herbivores can’t eat the plants then they can’t survive, and if they don’t survive then there will be little food for organisms at higher trophic levels.

The most important herbivores are insects simply because they are so abundant and diverse and, thus, are a major food source for species at higher trophic levels. The problem is that, as Tallamy learned, “most insect herbivores can only eat plants with which they share an evolutionary history.” Insects are specialized as to which plants they can eat because they have adapted ways to overcome the defenses that said plants have developed to keep things from eating them. Healthy, abundant, and diverse insect populations support biodiversity at higher trophic levels, but such insect populations won’t exist without a diverse community of native plants with which the insects share an evolutionary history.

That is essentially the thesis of Tallamy’s book. In a chapter entitled “Why Can’t Insects Eat Alien Plants?” Tallamy expounds on the specialized relationships between plants and insects that have developed over millennia. Plants introduced from other areas have not formed such relationships and are thus used to a much lesser degree than their native counterparts. Research concerning this topic was scarce at the time this book was published, but among other studies, Tallamy cites preliminary data from a study he carried out on his property. The study compared the insect herbivore biomass and diversity found on four common native plants vs. five common invasive plants. The native plants produced 4 times more herbivore biomass and supported 3.2 times as many herbivore species compared to the invasive plants. He also determined that the insects using the alien plants were generalists, and when he eliminated specialists from the study he still found that natives supported twice as much generalist biomass.

Apart from native plants and insects, Tallamy frames much of his argument around birds. Birds have been greatly impacted by humans. Their populations are shrinking at an alarming rate, and many species are threatened with extinction. Tallamy asserts, “We know most about the effects of habitat loss from studies of birds.” We have destroyed their homes and taken away their food and “filled their world with dangerous obstacles.” Efforts to improve habitat for birds will simultaneously improve habitat for other organisms. Most bird species rely on insects during reproduction in order to feed themselves and their young. Reducing insect populations by filling our landscapes largely with alien plant species threatens the survival of many bird species.

In the chapters “What Should I Plant?” and “What Does Bird Food Look Like?,” Tallamy first profiles 20 groups of native trees and shrubs that excel at supporting populations of native arthropods and then describes a whole host of arthropods and arthropod predators that birds love to eat. Tallamy’s fascinating descriptions of the insects, their life cycles, and their behaviors alone make this book worth reading. Other chapters that are well worth a look are “Who Cares about Biodiversity?” in which Tallamy explains why biodiversity is so essential for life on Earth, and “The Cost of Using Alien Ornamentals” in which Tallamy outlines a number of ways that our obsession with exotic plants has caused problems for us and for natural areas.

Pupa of ladybird beetle on white oak leaf (photo credit: wikimedia commons)

Pupa of a ladybird beetle on a white oak leaf. “The value of oaks for supporting both vertebrate and invertebrate wildlife cannot be overstated.” – Doug Tallamy (photo credit: wikimedia commons)

Convincing people to switch to using native plants isn’t always easy, especially if your argument involves providing habitat for larger and more diverse populations of insects. For those who are not fans of insects, Tallamy explains that “a mere 1%” of the 4 million insect species on Earth “interact with humans in negative ways.” The majority are not pests. It is also important to understand that even humans “need healthy insect populations to ensure our own survival.” Tallamy also offers some suggestions on how to design and manage an appealing garden using native plants. A more recent book Tallamy co-authored with fellow native plant gardening advocate Rick Darke called The Living Landscape expands on this theme, although neither book claims to be a how to guide.

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2015: Year in Review

Raise your glass. 2015 has come to a close, and Awkward Botany is turning three. Two great reasons to celebrate.

I started the year with the goal of posting at least once per week. Consider that goal accomplished, with a couple of bonus posts thrown in for good measure. I had also deemed 2015 the “Year of Pollination.” The underlying purpose was to teach myself more about pollinators and pollination while also sharing my interest in pollination biology with the wider world. That endeavor yielded 17 posts. There is still so much to learn, but we are making some headway. I started two new series of posts (Poisonous Plants and Botany in Popular Culture) and I continued with two others (Ethnobotany and Drought Tolerant Plants). I also went on a couple of field trips and wrote a few book reviews. All of that is reflected below in “Table of Contents” fashion.

Year of Pollination:

Botany in Popular Culture

Poisonous Plants

Ethnobotany

Drought Tolerant Plants

Book Reviews

Field Trips

Three posts that perhaps didn’t get the attention they deserve:

juniper in the snow

Going forward, I will continue to post regularly – as there is no shortage of plant-related things to write about – but I will likely take a week off here and there. I have other projects in mind – some related to Awkward Botany, some not – that will certainly demand much of my attention and time. I have some big ideas for Awkward Botany and beyond, and I will share those with the wide world in due time. For now, I would just like to say thanks all for reading, for commenting, and for sharing Awkward Botany with your friends. Overall, it has been a great year here at Awkward Botany headquarters, and I have you to thank for that. I feel privileged to be part of a community that is infatuated with plants and is fascinated by the natural world.

Good riddance to 2015. It was good, but it gets better. Now we look ahead to 2016. May it be filled with peace, love, and botany.