Genetic differences between global American Crocodile populations
identified in DNA analysis

Date:
July 13, 2020
Source:
University of Bristol
Summary:
A genetic analysis of the American crocodile (Crocodylus acutus)
has re- established our understanding of its population structure,
aiding its conservation.



FULL STORY ==========================================================================
A genetic analysis of the American crocodile (Crocodylus acutus) has re- established our understanding of its population structure, aiding its conservation. The collaborative study spanning seven countries and led by
the Wildlife Conservation Society and University of Bristol researchers
is published in PLOS ONE.


==========================================================================
The American crocodile is widespread across the American continent (from
South Florida to Venezuela, across the Greater Antilles, and from Mexico
to Ecuador).

Successful due to its ability to thrive within brackish and saltwater environments. Efforts to conserve the crocodile species have existed since
1975 when their status was set to vulnerable on the IUCN (International
Union for Conservation of Nature) red list. However, although conservation efforts have been put in place, the American crocodile faces further
threats including habitat degradation due to coastal development.

Replenishing these populations requires understanding of population
structures through genetic analysis, which can elaborate on the evolution
of the species' distribution. Gaining more understanding on how a species
has come to be distributed so widely and how populations can differentiate genetically, can inform regions how best to manage their populations.

The study reflected a regional collaborative effort, where DNA
sampling occurred across seven countries including Venezuela, Jamaica
and Cuba. There has been ongoing discussion on how these regional
populations of C.acutus are similar. However, the study's results found
that populations in Northern, Central and Southern America's and Great
Antilles differed genetically. There were similarities found between
Costa Rica and Jamaican populations. In Venezuela, they identified three
new haplotypes, which are closely related genes that help scientists
identify an origin of distribution.

Researchers believe that the mating with different species could have contributed to this distribution, also known as hybridisation. Crocodiles hybridise easily, contributing to their ability to survive since the prehistoric era. Additionally, in Florida genetic analysis showed there
had been a case of unintentional translocation, where the species had
been moved from a different location over time. This had been flagged
by previous research, where crocodiles with haplotypes from Central and
South America had been transported to Florida, most likely for the pet
trade, and later escaped or released into the wild by owners.

By identifying these differences between regional populations of
C. acutus, conservation efforts can establish population clusters which consider the populations as independent management units that may have different needs and focuses.

Natalia Rossi, Country Manager of the Cuba Program at the Wildlife
Conservation Society and the study's co-author explains some of the
challenges around taking samples from large crocodiles: "Our study
involved several research teams across multiple sites and countries and
often in difficult field conditions.

For four years between May to July the team would record, mark and
sample crocodile hatchings, and juvenile and adult crocodiles in Cuba's
Birama Swamp, one of the study sites. It was not unusual for us to
have to spend hours in the mangrove lakes waiting for one to appear,
and when a crocodile was spotted the whole team would have to enter
the water to help net it. While both exciting and rewarding work,
it is also dangerous as the crocodiles are powerful and it involves
lots of team co-ordination and trust to secure the crocodile to enable
us to take samples." The study was ambitious and could not have been
achieved without its global collaboration and efforts from its long list
of authors. In particular, the late John Thorbjarnarson and Rafael Crespo,
who dedicated their lives to this research.


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


========================================================================== Journal Reference:
1. Natalia A. Rossi, Angelica Menchaca-Rodriguez, Rafael Antelo, Byron
Wilson, Kurt McLaren, Frank Mazzotti, Rafael Crespo, Joe Wasilewski,
Fernando Alda, Ignacio Doadrio, Tito R. Barros, Evon Hekkala,
Manuel Alonso-Tabet, Yairen Alonso-Gime'nez, Manuel Lopez,
Georgina Espinosa- Lopez, Joe Burgess, John B. Thorbjarnarson,
Joshua R. Ginsberg, Kent A.

Vliet, George Amato. High levels of population genetic
differentiation in the American crocodile (Crocodylus acutus). PLOS
ONE, 2020; 15 (7): e0235288 DOI: 10.1371/journal.pone.0235288 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200713104332.htm

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