Biodiversity may limit invasions: Lessons from lizards on Panama Canal
islands

Date:
August 10, 2020
Source:
Smithsonian Tropical Research Institute
Summary:
Introduced species can become invasive, damaging ecosystems and
disrupting economies through explosive population growth. One
mechanism underlying population expansion in invasive populations
is 'enemy release', whereby the invader experiences relaxation of
agonistic interactions with other species, including parasites.



FULL STORY ==========================================================================
When the U.S. flooded Panama's Chagres River valley in 1910, Gatun
Lake held the record as the world's biggest reservoir. This record was surpassed, but researchers at the Smithsonian Tropical Research Institute (STRI), who are now studying invading lizards on the tiny islands that
dot the lake, discovered that islands with native lizards act as another
kind of reservoir, harboring the parasites that control invaders. The
study, published in the journal Biology Letters, is valuable experimental evidence that biodiversity is better, making ecosystems more resistant
to invasion.


==========================================================================
As part of another study to find out how many generations it takes for
slender anole lizards (Anolis apletophallus) to adapt to climate change,
a research team led by Christian Cox, a visiting scientist at STRI from
Florida International University, and Mike Logan from the University
of Nevada, Reno, transplanted lizards from the tropical forest on the
mainland to the islands, which tend to be hotter and drier. Before the transplant, they did a general health check of the lizards that included counting the number of parasites (mites) on their bodies.

When they came back several times during the next two years to see how
the lizards were doing in their new habitats, they recounted the number
of mites.

"We found that on the islands with no resident species of anole lizard,
the slender anole lizards that were transplanted to the islands lost
their mites within a single generation, and the mites are still gone
several generations later (up until the present)," Cox said. "Indeed, individual founding lizards that had mites during the initial transplant
had no mites when they were later recaptured. In contrast, anole lizards
that were transplanted to an island with another resident (native)
species of anole lizard kept their mites for three generations, and
some of the founders on the two-species island never lost their mites."
"Our study turned out to be a large-scale experimental test of the
enemy release hypothesis," said Logan, who did this work as a three-year STRI/Tupper postdoctoral fellow. "Often, when an invasive animal shows
up in a new place, all of its pathogens and parasites are left behind or
do not survive, giving it an extra survival advantage in the new place:
thus the term enemy release." The team also found that the two-species
island had lower density and lower biomass per unit area of the invasive
lizard species, indicating that the continued presence of the mites may
be keeping their populations under control.

"Our study is a clear example of something that conservationists have been trying to communicate to the public for some time," Logan said. "Diverse
native communities sometimes function as 'enemy reservoirs' for parasites
and diseases the keep down the numbers of invaders." Funding for this
study was provided by the Smithsonian Institution, Georgia Southern
University, the Theodore Roosevelt Memorial Foundation and the American
Museum of Natural History.


========================================================================== Story Source: Materials provided by
Smithsonian_Tropical_Research_Institute. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Christian L. Cox, Sean Alexander, Brianna Casement, Albert
K. Chung, John
David Curlis, Zachariah Degon, Madeline Dubois, Cleo Falvey,
Zackary A.

Graham, Edita Folfas, Maria A. Gallegos Koyner, Lauren K. Neel,
Daniel J.

Nicholson, Dylan J. Padilla Perez, Xochitl Ortiz-Ross, Adam
A. Rosso, Quinn Taylor, Timothy J. Thurman, Claire E. Williams,
W. Owen McMillan, Michael L. Logan. Ectoparasite extinction
in simplified lizard assemblages during experimental island
invasion. Biology Letters, 2020; 16 (8): 20200474 DOI:
10.1098/rsbl.2020.0474 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200810103310.htm

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