Date: November 22, 2016
Source: Swansea University
Research published by a Swansea
University scientist has found amphibians which have a toxic defense against
predators -- such as the iconic poison dart frogs -- have a much higher risk of
extinction than species which use other types of defense mechanisms.
The key finding of Dr Kevin
Arbuckle's latest study, published in the journal Royal Society Open Science, is that poisonous species are 60% more
likely to be threatened than species without chemical defenses.
Amphibians are usually considered
the most threatened group of vertebrate animals and are experiencing population
declines globally, raising conservation challenges.
The threats to amphibian
biodiversity are numerous and include rapid habitat destruction, exploitation,
and pollutants entering the environment.
Many characteristics of animals
may be linked to contemporary extinction risk. For instance, certain traits are
either known or suspected to influence factors such as mortality rates or the
ability of populations to recover after declines, and are therefore potential
predictors of extinction risk.
The work by Dr Arbuckle, Lecturer
in Biosciences (Evolutionary Biology) in the University's College of Science,
used amphibians as a model system and tested whether chemical antipredator
defense is associated with contemporary extinction rates. This is possible by
using conservation status (e.g. 'endangered', 'vulnerable') as a measure of
extinction risk in species alive today.
Dr Arbuckle said: "The
results of this new study suggest that while toxic defense can be great for
avoiding predators, it might be bad news in the long-term for a species. It's
another example of how evolution doesn't act 'for the good of the species', but
instead for the good of the individual.
"The results also suggest
that how a species defends itself might be part of the puzzle of working out
which species are in need of conservation efforts.
"The study builds on my
previous work, which found that toxic amphibians were also more likely to
become extinct over their evolutionary history, and the next step is to figure
out what mechanism is behind the link between defense and extinction.
Dr Arbuckle previously suggested
three main possibilities to explain higher extinction rates in toxic
amphibians, and figuring out which of these have been important are the focus
of another study.
The different ideas are:
• Costly chemical hypothesis: Chemical
defense is energetically costly;
• Marginal habitats hypothesis:
Chemical defense allows shifts to 'marginal' (low carrying capacity) habitats,
which are intrinsically more vulnerable, and;
• Slow life-history hypothesis:
Chemical defense is associated with slow life-histories, which damages the
recovery of populations after declines.
Story Source:
Journal Reference:
1 Kevin Arbuckle. Chemical antipredator
defence is linked to higher extinction risk. Royal Society Open Science, 2016;
3 (11): 160681 DOI: 10.1098/rsos.160681
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