Scientists challenge notion of binary sexuality with naming of new plant species

Scientists challenge notion of binary sexuality with naming of new plant species
The unusual fluidity the flower form of S. plastisexum inspired its name Credit: Chris Martine

A collaborative team of scientists from the US and Australia has named a new plant species from the remote Outback. Bucknell University biology postdoctoral fellow Angela McDonnell and professor Chris Martine led the description of the plant that had confounded field biologists for decades because of the unusual fluidity of its flower form. The discovery, published in the open access journal PhytoKeys, offers a powerful example of the diversity of sexual forms found among plants.

The new of bush tomato discovered in remote Australia provides a compelling example of the fact that sexuality among Earth's living creatures is far more diverse—and interesting—than many people likely realize.

Bucknell University postdoctoral fellow Angela McDonnell and biology professor Chris Martine led the study following an expedition last year to relocate populations of the new plant, which were first noted by Australian botanists during the 1970s.

Herbarium specimens from those few earlier collections are peppered with notes regarding the challenge of identifying the sexual condition of this plant, which appeared at various times to be female, male, or bisexual.

According to Martine, about 85% of the planet's quarter-million flowering have flowers that are bisexual—with both male and female organs present in every blossom.

"So that's already quite different than what some people might expect; but the remaining 15% or so come in all sorts of forms that push the envelope further, including unisexual flowers and (like we see in a plant like Cannabis) whole that are either male or female."

"For the most part, a given plant species will stick to one primary and predictable type of sexual expression," said Martine "but what makes Solanum plastisexum stand out is that it is one of a just a few plants that kind of do it all. It really seems like you never know what you'll get when you come across it."

Scientists challenge notion of binary sexuality with naming of new plant species
Fruit of Solanum plastisexum. Credit: McDonnel

When DNA studies in Martine's lab offered proof that these plants were not only all the same thing, but a species not yet described, he, McDonnell, Jason Cantley (San Francisco State University), and Peter Jobson (Northern Territory Herbarium in Alice Springs) set out to hunt for populations along the unpaved Buchanan Highway in the remote northwestern region of the Northern Territory.

The botanists were able to collect numerous new specimens and have now published the new species description in the open-access journal PhytoKeys, choosing the name Solanum plastisexum as a nod to the notable variation exhibited by this plant in its sexual condition.

"This name, for us, is not just a reflection of the diversity of sexual forms seen in this species," wrote the authors in the article. "It is also a recognition that this plant is a model for the sort of sexual fluidity that is present across the Plant Kingdom—where just about any sort of reproductive form one can imagine (within the constraints of plant development) is present."

Also known as the Dungowan bush tomato, Solanum plastisexum is a distant cousin of the cultivated eggplant and is a close relative of two other Australian species recently discovered by Martine and colleagues that were also published in PhytoKeys: Solanum watneyi, named for Mark Watney, the space botanist of the book/film The Martian; and Solanum jobsonii, a species named last year for S. plastisexum co-author Jobson.

The scientists hope that the naming of this latest new species turns a spotlight on the fact that nature is full of examples for the myriad ways in which living things behave sexually.

"In a way, S. plastisexum is not just a model for the diversity of sexual/reproductive form seen among plants—it is also evidence that attempts to recognize a "normative" sexual condition among the planet's living creatures is problematic."

"When considering the scope of life on Earth," the authors conclude, "The notion of a constant sexual binary consisting of two distinct and disconnected forms is, fundamentally, a fallacy."


Explore further

Newly established, a national park in Australia unveils a new plant species

More information: Angela J. McDonnell et al, Solanum plastisexum, an enigmatic new bush tomato from the Australian Monsoon Tropics exhibiting breeding system fluidity, PhytoKeys (2019). DOI: 10.3897/phytokeys.124.33526
Journal information: PhytoKeys

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Jun 19, 2019
Congratulations! They found another one of the many plants on earth that doesn't identify as heterosexual. Mammals, on the other hand, are binary. You still need a male sperm to fertilize a female egg in order to reproduce. Been that way for a few million years or so. Biology is a drag, right?

Jun 20, 2019
Congratulations! They found another one of the many plants on earth that doesn't identify as heterosexual. Mammals, on the other hand, are binary. You still need a male sperm to fertilize a female egg in order to reproduce. Been that way for a few million years or so. Biology is a drag, right?

Mammals are not just binary. There are intersex animals, including humans. It's not that rare.

Jun 20, 2019
Congratulations! They found another one of the many plants on earth that doesn't identify as heterosexual. Mammals, on the other hand, are binary. You still need a male sperm to fertilize a female egg in order to reproduce. Been that way for a few million years or so. Biology is a drag, right?

Mammals are not just binary. There are intersex animals, including humans. It's not that rare.

What you mean by "intersex"?

Jun 22, 2019
Mammals are not just binary. There are intersex animals, including humans. It's not that rare.


The typical mammal sexual distribution is bimodal, not binary. In humans ~ 1 % of individuals are atypical, either not interested in sex or having sex variants such as XYY. But in other species we have patterns such as alpha males or females, like in our sister lineage chimps and the more distant to both, gorillas.

And of course, mammals are also typically displaying more common homosexual or interspecies sex behaviors on top of the bimodal sex chromosome expression. Mostly, the original comment is making the natural fallacy, trying to decide social mores from biological circumstances - grown ups do what they like (as long as it does not harm others).

Jun 22, 2019
Sexual desire has no other purpose than to compel organisms to reproduce. The ones that found it more pleasurable are the ones that reproduced more often.

Any species will produce more offspring than can be expected to survive to maturity. The tropical human animal has always had problems with overpopulation ever since it upset the balance between natural attrition and growth through the use of technology.

But life has dealt with overgrowth in the past and has left these adaptive genes within our genome for us to use as well. Humans have many mechanisms both cultural and biological to combat overgrowth. One of them involves epigenetically neutering offspring in the womb by making them gay, in response to a mother's perception of tribal overcrowding and potential shortage of resources for offspring already born.

Other such mechanisms include eating disorders which return individuals to a prepubescent state, metabolic disorders, and compulsion for substance abuse.
Cont>

Jun 22, 2019
A cultural example - the artificial invention of adolescence. Although the perceived delay in the onset of sexual maturity may be in part biological. Adolescence is the excuse to belay reproduction throughout the period of greatest fecundity in most any animal. Religions have devised rituals such as the bar and bas mitzvahs to thwart this tendency and maximize growth.

Other examples of modulating the growth rate culturally would be caste systems which limit choice, the emancipation of women, one child per family laws, and of course contraception and ABORTION which have preempted over ONE BILLION people and their decendents since roe v wade. Not to mention postnatal infanticide, common throughout history.

Even the bible suggests the murder of firstborn heathens and the unfaithful.

Our powerful compulsion to reproduce is the result of our prehistoric environment. All the many ways we have of countering it tells us that overpopulation has always been perhaps our greatest problem.

Jun 22, 2019
Our world is plagued by religion-dominated cultures which seek to maximize our tropical growth rate for the heinous purposes of outgrowing and overwhelming. This strategy was very useful when the world was a miasma of tribal conflict due to our innate tendency toward overpopulation. The city mounds throughout the middle east attest to the repeated attempts to establish order, and its repeated failure and collapse from without and within.

The tropical religions subdued this world. But they are now obsolete. Their basic foundations are tribal, and this nature cannot be removed. Their primary message will always be the tribal edict - us vs them - and will never change.

They will always resist attempts to restrict their growth. Their laws against nonprocreative sex carry the strictest penalties because forced growth is expressly WHY they have survived to the present while all the less prolific religions were extincted.

For the good of the world tribalism and religion must end.

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