A
recent study led by Bucknell University Professor Chris Martine, biology, the
David Burpee Professor of Plant Genetics and Research, has identified and
described a new species of bush tomato with a special connection to ants—a
taxonomic journey sparked by unusual specimens held in Australian herbarium
collections.
The study, co-authored by a set of
Australian botanists and Jason Cantley—the former Burpee Postdoctoral Fellow in
Botany at Bucknell who is now Associate Professor of Biology at San Francisco
State University—appears in PhytoKeys and
underscores the critical role that natural history collections play in
biodiversity science.
The new species, Solanum nectarifolium
(Tanami bush tomato), was named for the location of its original collection
area—the northern edge of the Tanami Desert—and for the uniquely conspicuous
nectar-producing organs on the undersides of its leaves. These extrafloral
nectaries exude a sweet liquid to attract ants that might protect the plant
from herbivores. This remarkable trait marks the first known Solanum species
with extrafloral nectaries visible to the naked eye, a feature previously
observed only microscopically in a handful of related Australian species.
Martine first had an inkling that something was unusual about the plants from that region of the Northern Territory while working on a project with another former Burpee Postdoc, Angela McDonnell, now an Assistant Professor at St. Cloud State University. The pair included DNA extracted from two herbarium specimens representing Solanum ossicruentum, a species known as the blood bone tomato, that the Martine Lab described in the same journal in 2016, in an ongoing analysis meant to build a new bush tomato evolutionary tree.
Investigating unusual herbarium specimens
"We couldn't understand why
the two collections of the same species kept showing up in different parts of
the tree," says Martine. "I had collected one of them and was certain
that it represented Solanum ossicruentum, so I reached out to the person who
collected the other one, David Albrecht, and asked whether he thought the
plants he saw in 1996 at a place called Jellabra Rockhole could be something
else."
Albrecht, Senior Botanist at the
Northern Territory Herbarium at Alice Springs, suggested that the best way to
know would be for botanists to revisit that remote region of the northwestern
Tanami Desert and see for themselves. Martine, who had participated in seven
collecting expeditions to northern Australia since 2004, wasn't disappointed.
"I was kind of hoping he'd
tell me that," Martine says. "Because I was already planning some new
fieldwork in the Northern Territory and this would give me a great season to
visit an area I had never been to before. But to really be prepared for a trip
like that, I first needed to understand what other botanists had recorded and
collected there in the past—and there is only one surefire way to do that:
check what is in the herbarium collections."
So Martine started by using the
Australasian Virtual Herbarium (AVH), a database of every plant specimen held
in every herbarium in Australia. He searched for collections made of Solanum
ossicruentum and a similar species called Solanum dioicum in the northern
Tanami, finding 15 records for specimens gathered as far back as 1971.
Fieldwork and discovery in Australia
"It was a really interesting
distribution of points on the map, too," Martine says. "These were
far south of the other records for Solanum ossicruentum, with hundreds of miles
of 'empty' country between the two clusters. I couldn't wait to get to
Australia to see what those Tanami plants looked like."
In May 2025, Martine headed to
Australia to meet his team for the trip: Cantley and paper co-authors Kym
Brennan, Aiden Webb, and Geoff Newton, all associated with the Northern
Territory Herbarium at Palmerston. But, first, Martine made a stop at another
plant collection in the southwestern city of Perth.
"The visit to the Western
Australian Herbarium was my first chance to spend a bunch of time with some of
the actual specimens that I had earmarked based on the data in AVH,"
Martine explains. "And what
I saw there legitimately blew my mind."
Every specimen looked similar to
Solanum ossicruentum, except for a few subtle characteristics—and one thing
that Martine had never seen in more than two decades of Outback botanizing.
"On the backs of the leaves,
along the veins, were these visible round disks," Martine notes.
"They were each around a half-millimeter wide, really obvious, and the
only bush tomato specimens that had them—we're talking hundreds and hundreds of
collections—were the ones from the northern Tanami."
Extrafloral nectaries and ant interactions
Martine thought they could be
extrafloral nectaries (EFNs), non-flower organs on a plant that exude sweet
liquid, typically as a means to attract ants that might protect the plants from
herbivores. These were known to exist in a few Australian bush tomatoes, but
those are tiny and have only been confirmed with microscopes. EFNs that could
be seen without magnification would be something truly novel.
A few days later, Martine was in
the herbarium at Palmerston and found the same pattern: more visible disks and
only on plants from that same geographic area. Then he noticed that the most
recent collection, from 2021, had been made by Kym Brennan—a renowned field
biologist with an expertise in photography who was preparing for their trip in
the next room.
"I ran in there and asked
whether he remembered anything unusual about that collection—and before I could
finish my explanation for why, he was already showing me an incredible photo of
the leaves of that same plant. They were positively oozing with shiny, round
droplets of nectar, all from those disks on the veins."
Eight days and more than 1,000
kilometers of driving later, the team arrived near Brennan's collection site 50
kilometers southwest of the community of Lajamanu, right along the edge of the
unpaved Lajamanu Road.
"This was more or less the
same place where others had collected it in the early 1970s, so we were
cautiously optimistic that we'd not only find it there again, but that the
plants would have the flowers and fruits on them that we needed to describe
this as a new species," explains Martine. "But it's a harsh
environment and the abundance of bush tomatoes is often dependent on fire
occurrence. Sometimes you get to a place and there is nothing but old gray
stems. Other times there are more happy plants than you can count. In this
case, it was the latter situation."
The team got to work taking notes,
making measurements, and shooting photographs. Then Cantley called for Martine
to come over to the plant he was examining. There were ants all over the leaf undersides, avidly moving from
disk to disk and probing them for nectar. That confirmed the hypothesis.
The collaborators decided on the
scientific name "nectarifolium"—which translates to "nectar
leaf," for obvious reasons—and the English-language name Tanami bush
tomato. Martine then contacted a few experts about the conspicuous nature of
the EFNs and whether they had been seen anywhere else in the genus Solanum, a
group of around 1,200 species that includes the tomato, potato, and eggplant.
"As far as we know, this is
the first Solanum species to be described as having extrafloral nectaries that
you can see with your naked eye. That's a pretty cool finding—and it all
started with the examination of specimens that have been waiting in herbaria
for as long as a half-century for someone to come along and take a closer
look."
Significance of herbarium collections
Bucknell's own Wayne E. Manning
Herbarium, which holds approximately 25,000 plant specimens, now includes new
samples of the Tanami bush tomato. But the official holotype remains at the
Northern Territory Herbarium in Palmerston—almost 10,000 miles away from
Bucknell's campus.
"The Manning Herbarium may be
small, but every specimen is a snapshot of biodiversity," Martine says.
"These collections allow us to study where species occur, how they've
changed over time, and—in cases like this—even help discover new ones."
The publication of the new species
comes amid broader concern over the fate of natural history collections, such
as Duke University's recently announced closure of its herbarium housing more
than 800,000 specimens. Martine and his colleagues agree that such closures
could hinder future discoveries and conservation efforts.
Martine, a leading expert on
Australian bush tomatoes, was recently elected president of the Botanical
Society of America. He will begin his term as president following the
organization's annual meeting in August 2026.
"It still doesn't feel real and probably won't until I start my term just after Botany 2026," Martine says. "But I promise to do my best because plants are awesome and so are botanists."
Source: New species of bush tomato with visible nectar glands discovered in the Australian outback
No comments:
Post a Comment