New study analyzes role of scent compounds in the coevolution of bats
and pepper plants

Date:
August 11, 2021
Source:
University of Washington
Summary:
A study reports on how bats and pepper plants in Central America
have co- evolved to help each other survive.



FULL STORY ==========================================================================
A study published Aug. 11 in the Proceedings of the Royal Society B by researchers at the University of Washington and Stony Brook University
reports on how bats and pepper plants in Central America have coevolved
to help each other survive.


==========================================================================
The team -- led by Sharlene Santana, a UW professor of biology and curator
of mammals at the Burke Museum of Natural History and Culture -- focused
on the complex mixture of volatile organic compounds, or VOCs, produced
by fruits on pepper plants in the genus Piper at prime ripeness. The
study showed how these VOCs may have evolved to attract scent-oriented, short-tailed fruit bats from the genus Carollia, who then eat the fruits
and excrete the seeds into the landscape.

Plant-animal interactions have captured the attention of biologists
for centuries, and are key to maintaining the biodiversity of tropical ecosystems.

The dispersal syndrome hypothesis -- an explanation of how mutually
beneficial relationships between plants and fruit-eating animals may
lead to coevolution - - proposes that, when animals are effective
seed dispersers, they may select for fruit traits, including size,
color and odor, that match their sensory abilities, such as vision
and olfaction. But few studies have tested this hypothesis for complex
traits like fruit scents. This research provides one of the first tests
of bat-driven, fruit scent evolution.

The study is based on data collected during fieldwork at La Selva
Biological Station in Costa Rica. There, Piperis highly diverse, with
more than 50 recognized species. It is also a location where three Carolliaspecies -- C.

castanea, C. sowelliiand C. perspicillata -- are some of the most abundant
bats year-round and coexist with approximately 62 other bat species.

The team spent hundreds of hours searching and collecting ripe fruits
from Piper to extract and quantify the VOCs that make up their fragrant
scent. They also collected fecal samples from live bats and then released
them back into the wild to determine which Piper species the bats were
eating and how much. In addition, the researchers conducted behavioral experiments with wild bats where they offered options of unripe fruits
enhanced with the most common VOCs found in local Piper plants. Video
cameras and microphones recorded the bats' feeding behaviors and
echolocation calls.

The team found Piper fruit scent bouquets were complex and diverse. The
authors identified and quantified 249 VOCs in ripe fruit scents
across 22 Piper species. Some compounds were found in the fruit scent
of most species -- like alpha-caryophyllene, which has a spicy scent
like cinnamon or cloves. Others, like 2-heptanol, were only found in a
few Piper species. The diet experiments showed that, while the three Carolliafruit batspecies varied in their reliance on Piper as a food
source, all consumed a lot of a few Piperspecies, and a little of many
others. Surprisingly, this was not related to how abundant the Piper
species are at La Selva, so the bats must choose Piper fruits based on
other characteristics and not just how well represented they are across
the landscape. The team's behavioral experiments provided some clues to
what might be happening: Bats preferred samples spiked with 2-heptanol,
a VOC found in the fruit scents of the Piper species they eat the most.

"These findings suggest bats use specific chemicals in the fruit scent
bouquet not only to select ripe fruits, but to find the specific Piper
species that make up the bulk of their diet," said Santana, who is
co-lead author on the study. "By helping them communicate with the bats,
these chemical signals are likely a component of a dispersal syndrome
in these plants." Through statistical and evolutionary analyses of the
data on fruit scent chemistry and bat diet, the team further demonstrated
that the evolutionary patterns of chemical diversity and the presence
of specific compounds in Piper fruit scents is associated with greater
bat consumption and scent preferences.

This highlights the potential effect of bat fruit consumption on the
evolution of fruit chemistry, a relationship that contributes to the
extreme diversity of tropical fruiting plants worldwide.

"Flying in the dark means bats cannot find ripe fruit by sight, but rely
on olfaction instead," said co-author Liliana Da'valos, a professor at
Stony Brook University. "Olfaction is the bridge between the plant signal
and bat fruit consumption, and finding the specific VOCs bats respond to
opens the door to matching olfactory receptor genes to important VOCs,
which has been impossible until now." Understanding the relationship
between bats and pepper plants not only contributes to knowledge about coevolution of these species, but also has benefits for rainforest habitat conservation. Piperare some of the first plants to grow in forest gaps
and edges, and Carollia? as key dispersers of Piper seeds ? can help
restore plant life in logged areas.

"Our current and future work is identifying the odorant receptors that
allow the bats to detect the fruit scents. This will allow us to link
the ecology and evolution of these relationships with the physiological mechanisms," said co- author Jeffrey Riffell, a UW professor of biology.

Co-lead author on the paper is former UW postdoctoral researcher Zofia Kaliszewska. Other co-authors are UW doctoral alum Leith Leiser-Miller, M.

Elise Lauterbur at the University of Arizona and Jessica Arbour at Middle Tennessee State University. The research was funded by the National
Science Foundation.

========================================================================== Story Source: Materials provided by University_of_Washington. Original
written by Andrea Godinez. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Sharlene E. Santana, Zofia A. Kaliszewska, Leith B. Leiser-Miller,
M.

Elise Lauterbur, Jessica H. Arbour, Liliana M. Da'valos, Jeffrey A.

Riffell. Fruit odorants mediate co-specialization in a
multispecies plant-animal mutualism. Proceedings of the Royal
Society B: Biological Sciences, 2021; 288 (1956): 20210312 DOI:
10.1098/rspb.2021.0312 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210811162901.htm

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