Researchers discover new species in critically imperiled ecosystem


Date:
March 14, 2022
Source:
Florida Museum of Natural History
Summary:
Researchers working in one of the world's most biodiverse and
threatened ecosystems have discovered a new plant species, Castela
senticosa, which they recommend be designated as endangered. The
plant, which grows as a small bush sheathed in an imposing layer
of spines, was found during a survey to catalog the flora of the
Marti'n Garci'a mountain range in the Dominican Republic.



FULL STORY ========================================================================== Researchers working in one of the world's most biodiverse and threatened ecosystems have discovered a new plant species, Castela senticosa, which
they recommend be designated as endangered. The plant, which grows as
a small bush sheathed in an imposing layer of spines, was found during
a survey to catalog the flora of the Marti'n Garci'a mountain range in
the Dominican Republic.


==========================================================================
"We were collecting everything we came across with the goal of having a complete species list for the entire mountain range," said lead author
Lucas Majure, an assistant curator at the Florida Museum of Natural
History and curator of the University of Florida Herbarium.

Hispaniola's mountains support large swaths of intact tropical dry
forests, highly diverse ecosystems that -- like the rainforests
they border -- are globally imperiled due to the combined effects of deforestation, overharvesting and climate change. But although they face
the same threats, the destruction of a tropical dry forest might mean the
loss of considerably more species. That's because rainforests are often
found in lowland basins, where conditions like rainfall, temperature and
soil type are similar over large areas. While species diversity is high,
many rainforest plants can have distributions that span hundreds of miles.

Dry forests can be just as diverse, but their plants tend to be
geographically restricted; up to 73% of plant species of dry forests in
the American tropics are endemic to a particular region. Plants growing on Caribbean islands, which have been separated from continental landmasses
for more than 50 million years, have an extra layer of isolation built
in. As a result, much of the Caribbean flora can be found nowhere else
on Earth.

"The overall diversity is amazing," Majure said. "If you go across
Hispaniola, Cuba and Jamaica, there are quite a few plant groups that make these forests incredible places to work." Along the slopes of the Sierra Marti'n Garci'a alone, Majure and other researchers from the U.S. and
Dominican Republic identified more than 700 plant species during their
survey. But when Majure and Teodoro Clase of the Dominican Republic's
National Botanical Garden stumbled across a non-descript shrub halfway
up the mountain, both botanists were stumped. The plant was largely
a tangle of thorns, with few leaves and no flowers or fruits, which
left little in the way of identifying characteristics. They carefully
collected and pressed one of the branches, which Majure took with him
back to the Florida Museum for further study.



========================================================================== After returning from the field, Majure set to work determining the
identity of the plant. After documenting the diversity of Caribbean
plants for almost a decade, he had a good reference frame for what the
species wasn't. But finding a positive match would require some careful sleuthing. "This sat around for a while and just bothered me to no end
because I couldn't figure it out," he said.

He found a strong candidate while sifting through the digital records
of plant specimens stored at the New York Botanical Garden. There,
tucked away among more than 7 million preserved plants, was a small,
severed branch with a profusion of pale-green thorns. The specimen had
been collected in northwestern Haiti in 1929 by Smithsonian botanist
E. C. Leonard and later identified as Castela depressa, a species endemic
to Hispaniola and related to the highly invasive tree of heaven that's
spread across much of North America. It seemed Majure had found a match.

To confirm the identification, he extracted DNA from both the old and
new collection, along with related species, finding that the nearly
century-old plant was indeed the match he'd been looking for. But it
wasn't Castela depressa or anything else that had ever been collected.

Instead, Majure had discovered something entirely new. Given that it had
only ever been collected twice, it was likely also something incredibly
rare. But to officially name a new species, he would need to find another specimen that had both flowers and fruit, which would allow him to paint
a complete picture of what the plant looked like.

So Majure went back to the Dominican Republic with one of his
Ph.D. students, Yuley Pin~eyro, to hunt for the elusive plant. When they
hiked out into Hispaniola's dry tropical forests in late spring, however,
the climate was living up to its name. "It was incredibly dry, and I
thought there was no way we were going to find this thing in flower,"
Majure said.



==========================================================================
But after hiking to about mid-elevation, Pin~eyro spotted a flash of
red against the backdrop of dull-green vegetation, which upon closer
inspection turned out to be the exact plant they were looking for. One
of the only things in full bloom that early in the year, the plant had
small, white to cream- colored flowers and crimson, scythe-shaped fruit resembling miniature peppers.

"Most other species in these forests have totally lost their leaves
during the dry season, but it appears the strategy of this Castela is
to flower and fruit while everything else is dormant. That way, it's
fully exposed to pollinators and dispersers," Majure said.

It's unclear what pollinates the plant's flowers or eats its fruit,
but Majure thinks its natural history might provide a clue. Castela
senticosa likely originated on the island, but it's closely related to
species native to the Sonoran Desert in western North America. Since
the seeds are too large to be dispersed by winds, they must have been transported long-distance.

"We think that birds are the primary dispersal agents here, but we
don't actually have any good hypotheses about what birds might have
been dispersing something all the way from the Sonoran Desert to the Caribbean," he said. "It's still a bit of an enigma." Castela senticosa
isn't the first, nor will it be the last new species Majure and Clase
describe from Hispaniola's dry forests. The pair recently collaborated
on naming a new plant with leaves as small as Aspirin pills, and there
are more waiting to be described, Clase said.

"There are several very rare and endemic species that grow in Hispaniola's
dry forests that make them important targets for conservation, and future studies will reveal even more discoveries," he said.


========================================================================== Story Source: Materials provided by
Florida_Museum_of_Natural_History. Original written by Jerald
Pinson. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Castela_senticosa ========================================================================== Journal Reference:
1. Lucas C. Majure, Kasey Pham, Teodoro Clase. Castela senticosa
(Simaroubaceae: Sapindales), a New Species from the Caribbean Clade
Endemic to Seasonally Dry Tropical Forest on Hispaniola. Systematic
Botany, 2021; 46 (4): 1033 DOI: 10.1600/036364421X16370109698560 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220314105617.htm

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