Islands are cauldrons of evolution
Study explores adaptation in island, mainland anoles

Date:
October 12, 2021
Source:
Washington University in St. Louis
Summary:
Islands are hot spots of evolutionary adaptation that can also
advantage species returning to the mainland, according to a
new study.



FULL STORY ========================================================================== Islands are hot spots of evolutionary adaptation that can also advantage species returning to the mainland, according to a study published the
week of Oct. 11 in the Proceedings of the National Academy of Sciences.


========================================================================== Islands are well known locations of adaptive radiation, where species
diversify to fill empty niches. In contrast, species that evolved on
islands are thought to be evolutionarily disadvantaged when attempting
to recolonize the mainland.

Jonathan B. Losos, the William H. Danforth Distinguished University
Professor, professor of biology in Arts & Sciences and director of
the Living Earth Collaborative at Washington University in St. Louis,
is senior author of the new study.

Losos and his colleagues used a time-calibrated phylogeny and measurements
of relevant ecological and morphological traits of neotropical anoles (Anolisspp.) to explore the collision of island and mainland adaptive radiations.

Anolis lizards originated in South America, colonized and radiated
on various islands in the Caribbean and then returned and diversified
on the Central American mainland. All of the Anolis groups exhibited significant adaptive radiations, but the results suggested that they
followed different evolutionary paths.

The island Anolis species, and to a lesser extent the ancestral species, experienced higher initial rates of evolution as ecological niches
were filled.

In contrast, the Anolis species that recolonized the Central American
mainland from the islands diversified ecologically without developing significant morphological differences between species.

When the Isthmus of Panama reconnected the two mainland groups, the recolonizing Central American Anolis species outcompeted the ancestral
South American Anolis species, contrary to expectations.

According to Losos, rather than being evolutionary dead ends, islands
are cauldrons of evolutionary innovation and diversification.

"The traditional thinking is that plant and animal groups that evolve
on islands can't invade the mainland because the mainland has more
species, and thus a more competitive biotic milieu due to higher rates
of competition, predation, parasitism, etc.," Losos said. "So the idea is
that species on islands aren't 'tough' enough to cut it on the mainland.

"In recent years, many studies have documented contradictory
examples of island species successfully invading the
mainland," Losos said. "Ours goes further by showing that
island species not only can invade, but diversify greatly." ========================================================================== Story Source: Materials provided by
Washington_University_in_St._Louis. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Austin H. Patton, Luke J. Harmon, Mari'a del Rosario Castan~eda,
Hannah
K. Frank, Colin M. Donihue, Anthony Herrel, Jonathan B. Losos. When
adaptive radiations collide: Different evolutionary trajectories
between and within island and mainland lizard clades. Proceedings
of the National Academy of Sciences, 2021; 118 (42): e2024451118
DOI: 10.1073/ pnas.2024451118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211012112317.htm

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