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IGUANA  •  VOLUME 15, NUMBER 4  •  DECEMBER 2008 245CONSERVATION RESEARCH REPORTS

New Pacific Iguana
The Pacific iguanas of the Fijian and
Tongan archipelagos are a biogeographic
enigma in that their closest relatives are
found only in the Western Hemisphere.
These iguanas were thought to comprise
two genera and four species of extinct
and extant taxa. The two currently recog-
nized extant species, Brachylophus fascia-
tus, from Fiji, Tonga, and Vanuatu, and
Brachylophus vitiensis, from western Fiji,
are of considerable conservation concern,
with B. vitiensis listed as critically endan-
gered. In a recent molecular study,
KEOGH ET AL. (2008. Philosophical
Transactions of the Royal Society B
(Biological Sciences) 363:3413–3426)
showed that Brachylophus comprised
three evolutionarily significant units. To
test these conclusions and to reevaluate
the phylogenetic and biogeographic rela-
tionships within Brachylophus, the
authors generated a mitochondrial DNA
dataset for 61 individuals from 13
islands, representing both currently rec-
ognized species of Brachylophus. The data
rejected the monophyly of specimens
previously believed to comprise B. fascia-
tus, instead demonstrating that
Brachylophus includes three distinct
species: B. fasciatus from the Lau group of
Fiji and Tonga, a new species, B. bulab-
ula, from the central regions of Fiji, pop-
ulations which until now were considered

to be B. fasciatus or B. vitiensis. These
molecular and taxonomic results have
important implications for future conser-
vation initiatives for Pacific iguanas.

Emerging Threats to 
Long-lived Vertebrates

Persistent contaminants are ubiquitous in
the environment, often present at concen-
trations that may jeopardize reproductive
fitness only after long periods of exposure.
As the duration of exposure is largely reg-
ulated by life span, long-lived species of
high trophic status, such as many reptiles,
birds, and mammals, may be at risk of
reduced fitness and population decline.
ROWE (2008. BioScience 58:623–631)
suggested that delayed maturation and
iteroparity (repeated production of off-
spring at intervals throughout the life
cycle) confer the potential for cumulative
effects to be expressed prior to reproduc-
tion, and large parental investments in
yolk and milk may threaten offspring
because of exposure during critical devel-
opmental periods. Long generation times
may delay emergence of obvious effects
on populations, perhaps eluding early
intervention, while constraining rates at
which populations may recover if condi-
tions subsequently improve. Life history
theory thus suggests that the suite of traits
that optimized reproductive fitness
throughout long-lived species’ evolution-

ary histories may ultimately put them in
peril in the modern anthropogenically
altered environment.

Frogs with Disease-resistance Genes
May Escape Extinction

As frog populations die off around the
world, researchers have identified certain
genes that can help the amphibians
develop resistance to harmful bacteria
and disease. The discovery may provide
new strategies to protect frog populations
in the wild. New research examines how
genes encoding the major histocompati-
bility (MHC) complex affect the ability
of frogs to resist infection by a bacterium
that is commonly associated with frog
population declines.

“In the short term, captive manage-
ment of frogs with complementary disease-
resistance genes may offer the best hope for
saving species from extinction,” says Bruce
Waldman, a biologist at Lincoln University
in New Zealand and one of the paper’s
authors. “Management practices that
maintain or enhance diversity in MHC
genes may prove the key to safeguarding
frog populations in the wild.” “Massive
die-offs of frogs may indicate environmen-
tal problems that ultimately will affect
other species, including humans,”
Waldman says. “But, despite the concern,
little is known about factors that make
individuals susceptible to disease.”

C O N S E R V A T I O N  R E S E A R C H  R E P O R T S

Populations from central regions of Fiji, for-
merly assigned to Brachylophus fasciatus, were
shown to represent a new species, B. bulabula. 

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Top predators such as Nile Monitors (Varanus niloticus) may be at risk of reduced fitness and
population declines due to cumulative effects of persistent environmental contaminants to which
they are exposed over long life spans.

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246 IGUANA  •  VOLUME 15, NUMBER 4  •  DECEMBER 2008 CONSERVATION RESEARCH REPORTS

BARRIBEAU ET AL. (PLoS One 3:
e2692, <www.plosone.org/article/info:
doi/10.1371/journal.pone.0002692>)
exposed African Clawed Frog tadpoles to
several doses of the bacterium Aeromonas
hydrophila and examined the number of
tadpoles that survived and measured how
fast they grew. Certain genes allowed tad-
poles to survive bacterial infection but at
a cost, as these tadpoles sometimes grew
more slowly. Among siblings, patterns of
disease resistance corresponded to tad-
poles’ MHC genes rather than other genes
that they shared, demonstrating that the
MHC genes conferred immunity.

Programs currently are underway to
rescue frogs from declining wild popula-
tions and breed them in captivity to ensure
that species are not lost to extinction. This
study suggests that selective breeding of
individuals with known disease-resistance
genes might produce frogs that can survive
infection by pathogens, even after the frogs
are reintroduced into the wild.

The research team studied the African
Clawed Frog because its immune system
already had been well characterized, but as
most frogs and toads have similar immune
systems, they believe that their results will
be generally applicable to all threatened
and endangered amphibians.

New Approach to 
Conserving Amphibians

The global extinction crisis demands
immediate action to conserve species at
risk. However, if entire groups such as
superfamilies are at risk due to shared
evolutionary history, a shift towards con-
serving such groups rather than individ-
ual species may be needed. Using phylo-

genetic autocorrelation analysis, COREY

AND WAITE (2008. Diversity and
Distributions 14:614–629) demonstrated
that multiple kinds of extinction threat
clump within the amphibian tree of life.
Their study provided insight into how
these threats might collectively influence
the extinction risk of whole groups, con-
sistent with the supposition that related
species, with similar traits, share an
intrinsic vulnerability to common kinds
of threat. Most strikingly, they found a
significant concentration of ‘enigmatic’
decline and critically endangered status
within families of the hyloid frogs. This
phylogenetic clumping of risk is also geo-
graphically concentrated, with most
threats found in Central and South
America, and Australia, coinciding with
reported outbreaks of chytridiomycosis.
They speculated that the phylogenetic
clumping of threat represents, in part,
shared extinction proneness due to
shared evolutionary history. However,
even if the phylogenetic clumping of
threat were simply a by-product of shared
geography, this concordance between
phylogenetic and geographical patterns
represents a prime opportunity. Where
practical, conservation plans should focus
on biogeographical regions where threat-
ened groups occur, thereby improving
the capacity for conserving species. This
approach could outperform the usual
triage approach of saving individual
species after they have become critically
endangered.

Surveying Herpetofaunal Mortality 
on Rural Highways

Road mortality can contribute to local
and regional declines in amphibian and
reptilian populations. Consequently,
accurately and efficiently identifying
hotspots of road-mortality is necessary
for hazard assessment and mitigation. In
2002, LANGEN ET AL. (2007. Journal of
Wildlife Management 71:1361–1368)
conducted walking and driving surveys
throughout an extensive rural highway
network in northern New York to evalu-
ate survey methods and to quantify spa-
tial and temporal patterns of herpetofau-
nal road-mortality. In 2004, they
repeated the surveys at a subset of loca-
tions to quantify interannual repeatabil-
ity. Reptilian and amphibian species had
different peak periods of road-mortality
because they differed in the causes of
movements that resulted in crossings.

Spatial locations of herpetofaunal road-
mortality were concentrated at a limited
number of hotspots. Hotspots over-
lapped across species and were located at
consistent locations across years. Results
of walking and driving surveys were
highly repeatable among survey teams,
but driving surveys underestimated the
density of road-mortality because many
animals were missed. Detection failure
was higher in some taxa (e.g., frogs) than
others (e.g., turtles). Their results indi-
cated that designing a valid, efficient
methodology for locating hotspots of
reptilian and amphibian road-mortality
along a road network is possible, thus
pinpointing priority sites for mitigation.

A study of tadpoles of African Clawed Frogs
(Xenopus laevis) indicated that some individ-
uals with disease resistant genes grew more
slowly. 

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A clumping of threats to groups of frogs,
especially the hyloid frogs such as this Red-
eyed Treefrog (Agalychnis callidryas), might
represent, at least in part, a shared extinction
proneness due to shared evolutionary history. 

Reptilian and amphibian species had differ-
ent peak periods of road-mortality because
they differed in the causes of movements that
resulted in crossings. Spatial locations of her-
petofaunal road-mortality were concentrated
at a limited number of hotspots, such as
those used by female turtles moving to nest-
ing areas. 

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