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It is predicted that climate change will cause species extinctions and distributional shifts in coming decades, but data to validate these predictions are relatively scarce. Here, we compare recent and historical surveys for 48 Mexican lizard species at 200 sites. Since 1975, 12% of local populations have gone extinct. We verified physiological models of extinction risk with observed local extinctions and extended projections worldwide. Since 1975, we estimate that 4% of local populations have gone extinct worldwide, but by 2080 local extinctions are projected to reach 39% worldwide, and species extinctions may reach 20%. Global extinction projections were validated with local extinctions observed from 1975 to 2009 for regional biotas on four other continents, suggesting that lizards have already crossed a threshold for extinctions caused by climate change.
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DOI: 10.1126/science.1184695
, 894 (2010); 328Science et al.Barry Sinervo,
Altered Thermal Niches
Erosion of Lizard Diversity by Climate Change and
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could occur in C. maculatus through sexual se-
lection on males (18,2628). If sexual selection is
responsible for the greater strength of the r
coefficients in males, it raises the possibility of
positive feedback, where sexual selection
increases the contribution of deleterious muta-
tions to trait expression, in turn increasing both
good genes benefits from sexual selection and the
benefit of sex itself.
References and Notes
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29. We thank J. Chan for the maintenance of the pedigree
and the collection and management of the data set;
R. Black and F. Gonzalez for statistical advice; B. Booth,
A. Sutton, and S. Jennings for their assistance with the
experiment; and N. Colegrave, W. Hazel, M. Puurtinen,
J. Radwan, M. Ritchie, and L. Simmons for their comments
on the manuscript. This work was supported by Australian
Research Council fellowships to J.L.T. and N.R.L.
Supporting Online Material
Materials and Methods
SOM Text
Figs. S1 to S6
Tables S1 to S10
5 February 2010; accepted 24 March 2010
Erosion of Lizard Diversity by Climate
Change and Altered Thermal Niches
Barry Sinervo,
*Fausto Méndez-de-la-Cruz,
Donald B. Miles,
Benoit Heulin,
Elizabeth Bastiaans,
Maricela Villagrán-Santa Cruz,
Rafael Lara-Resendiz,
Norberto Martínez-Méndez,
Martha Lucía Calderón-Espinosa,
Rubi Nelsi Meza-Lázaro,
ctor Gadsden,
Luciano Javier Avila,
Mariana Morando,
Ignacio J. De la Riva,
Pedro Victoriano Sepulveda,
Carlos Frederico Duarte Rocha,
Nora Ibargüengoytía,
sar Aguilar Puntriano,
Manuel Massot,
Virginie Lepetz,
Tuula A. Oksanen,
David G. Chapple,
Aaron M. Bauer,
William R. Branch,
Jean Clobert,
Jack W. Sites Jr.
It is predicted that climate change will cause species extinctions and distributional shifts in coming
decades, but data to validate these predictions are relatively scarce. Here, we compare recent
and historical surveys for 48 Mexican lizard species at 200 sites. Since 1975, 12% of local
populations have gone extinct. We verified physiological models of extinction risk with observed local
extinctions and extended projections worldwide. Since 1975, we estimate that 4% of local
populations have gone extinct worldwide, but by 2080 local extinctions are projected to reach 39%
worldwide, and species extinctions may reach 20%. Global extinction projections were validated
with local extinctions observed from 1975 to 2009 for regional biotas on four other continents,
suggesting that lizards have already crossed a threshold for extinctions caused by climate change.
Global climate change affects organisms
in all biomes and ecosystems. Two nat-
ural compensatory responses are possi-
ble. Given enough time and dispersal, species
may shift to more favorable thermal environ-
ments, or they may adjust to new environments
by behavioral plasticity, physiological plasticity,
or adaptation. Alternatively, failure to adjust or
adapt culminates in demographic collapse and
extinction. Despite accumulating evidence of
contemporary climate change affecting species
ranges and phenologies (13), evidence of ex-
tinctions at either local or global scales is lack-
ing (46). Moreover, current forecasting models
(7,8) are not calibrated with actual extinctions,
but are premised on hypothesized effects of
thermal physiology on demography and extinc-
tion. Alternatively, models are based on range
shifts or species-area relations in mobile species
(1), but not extinctions (9). Hence, there is still
much uncertainty regarding the expected mag-
nitude of extinctions resulting from climate
change (10).
Empirical validation of global extinction fore-
casts requires three forms of evidence. First,
actual extinctions should be linked to macro-
climate and validated to biophysical thermal
causes arising from microclimate (11). Second,
the pace of climate change should compromise
thermal adaptation (10), such that evolutionary
rates lag behind global warming owing to con-
straints on thermal physiology (12,13). Third,
extinctions due to climate should be global in
From 2006 to 2008, we resurveyed 48
Sceloporus lizard species at 200 sites in Mexico
that were first sampled in 1975 to 1995, and 12%
of sites were locally extinct by 2009 (table S1).
Although Sceloporus lizards are heliotherms
that bask and require solar radiation to attain
physiologically active body temperatures (T
(14,15), activity in hot weather may result in T
exceeding CT
, the critical thermal maximum,
leading to death. Lizards retreat to cool refuges
rather than risk death by overheating. However,
hours of restriction (h
) in thermal refuges limit
foraging, constraining costly metabolic functions
like growth, maintenance, and reproduction, there-
by undermining population growth rates and
raising extinction risk. Lizards could evolve
higher T
, but this brings them closer to CT
which increases risk of overheating. Extinction
risk may increase because of other thermal adap-
tations. For example, viviparity, which is posited
to be a thermal adaptation to cold climates (16),
may elevate extinction risk because high T
can compromise embryonic development in
utero (17).
We analyzed rate of change in maximum air
temperature Tmax
at 99 Mexican weather sta-
tions and constructed climate surfaces (tables S2
and S3, 1973 to 2008; fig. S1). Rate of change in
was greatest for winter-spring (January to
May; fig. S1 and table S3A) and increased faster
in northern and central México and at high ele-
vation, as evidenced by significant coefficients for
fitted climate surfaces. We found a correlation
between rate of change in T
during winter-
spring breeding periods and local extinctions of
Sceloporus species (table S3).
Many viviparous species in México are con-
fined to high-elevation islands,where climate
change has been most rapid. Logistic regression
and multiple regression with phylogenetic inde-
pendent contrasts (18,19) revealed that extinction
risk was significantly related to low latitudinal
and altitudinal range limits (Fig. 1, A and B),
where thermal physiology and/or ecological
interactions limit species (20,21). Phylogenetic
correlation analysis (18) showed that extinction
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risk of viviparous lizards (18%) was twice that
of oviparous lizards (9%, n=10000 bootstrap
replications P< 0.001). Moreover, multiple re-
gression based on phylogenetic independent
contrasts (PICs; Fig. 1C and table S4) showed that
extinction risk of viviparous taxa was significant-
ly related to low TbðTb,viviparous ¼31:8-CT
0:31 ½SE,Tb,oviparous ¼34:8-CT0:40, t¼
5:92, P<0:0001Þand cool montane habitats
ðTair,viviparous ¼22:4-CT1:79, Tair ,oviparous ¼
28:39-CT1:38, t¼2:89, P<0:006Þ,where
climate has changed most rapidly in México.
To validate patterns of extinction risk and
, we deployed thermal models (22) that record
operative temperatures (T
) at two extinct and
two persistent Yucatán sites of S. serrifer. Hours
of restriction in activity (h
) during reproduction
was significantly higher at extinct versus per-
sistent sites (t=9.26,P< 0.0001). By April
2009, h
at extinct Yucatán sites had become
so severe that if S. serrifer were still present, it
would have to retreat shortly after emergence
(fig. S4A). Daily T
was positively correlated
with h
assessed by T
(P< 0.001, fig. S4B). The
relation between h
as a function of T
to S. serrifersT
eq. S2 (23)] is a general formula for predicting
We modeled extinct/persistence status based
on values for h
at Sceloporus sites derived from
eq. S2 (23). The Yucatán ground truth for S.
serrifer suggests that extinction occurs when h
exceeds 4. We calibrated this value with extinct/
persistent Sceloporus sites. Goodness-of-fit tests
of the model indicate that the best fit for ob-
served and predicted extinctions at Sceloporus
sites is h
> 3.85. If a species with a given T
a given geo-referenced site, subjected to T
experienced h
> 3.85 during the 2-month re-
productive period (March to April), we assumed
that it would go extinct by 2009. Association of
predicted and observed extinctions from this
physiological model was significant for ovipa-
rous (c
= 49.0, P< 0.001) and viviparous taxa
As demography of high-elevation taxa be-
comes compromised due to climate change, spe-
cies at low elevation that were previously limited
by physiology and competition should expand
into historically cooler habitat that is now warmer
(20,24), perhaps accelerating extinction of high-
elevation forms. For viviparous taxa, six errone-
ously assigned extinct sites involved six of the
eight cases of range expansion by low-elevation
taxa, which all invaded from low to high altitudes
or latitudes (table S1; significant by sign test, P<
0.001). Adding range shifts of competitors as a
factor improved fit significantly between observed
and predicted extinctions (Dlog likelihood = 45.37,
1df,P< 0.0001, logistic regression). Therefore,
competitive exclusion by invading low-elevation
taxa appears to exacerbate climate-change ex-
tinctions of high-elevation taxa.
Lizards cannot evolve rapidly enough to track
current climate change because of constraints
arising from the genetic architecture of thermal
preference (12,13). A phylogenetic correlation
between T
and CT
constrains adaptation.
PIC regression of CT
on T
among Phryno-
somatidae suggests that a shift in T
by 1°C yields
only a 0.5°C correlated response in CT
may not evolve
fast enough to keep up with evolved change in
. Furthermore, adaptive increase in T
due to
climate change is constrained by genetic cor-
relations in which high T
necessarily requires
prolonged activity out of retreat sites (25),
further increasing risk of overheating. Genetic
trade-offs with energetically costly traits such as
growth (25) also constrain adaptation.
The evolutionary response (R=h
s;sis the
selection differential) necessary to keep pace with
climate change is further constrained by low
heritability for T
, which we previously estimated
at h
=0.17forSceloporus occidentalis in the
laboratory (25). We used the physiological model
to compute the sustained selection differential at
each site j, such that T
evolves to
match T
, yielding Dh
thereby rescuing population j from extinction [D
computed over 1975 to 2009 (historical), 2009 to
2050, and 2050 to 2080]. We assumed s
, and generation times of 1 year versus
2 years (i.e., lowland versus montane Sceloporus,
table S1). We expressed these critical levels of
adaptive response as surfaces for s
, the
sustained selection differential (Fig. 2B).
We compared the magnitude of selection al-
lowing a species to adapt to climate change with
maximum rates sustained under artificial or
natural selection (26). Such comparisons are
facilitated by dividing each sustained selection
differential by the standard deviation (s
1.23 for T
of Mexican lizards) to obtain i,the
standardized intensity of selection (26). Whereas
i> 0.4 can be sustained in laboratory artificial
selection for nine generations (27), studies in
nature (26) indicate that i> 0.4 computed on
an annual basis are rare (<5%). We also refer-
ence ito other anthropogenic causes of selection.
Overfishing of Atlantic cod yielded i=0.55,
among the highest measured, but this selection
regime caused demographic collapse of the fish-
ery (28). In México, extinct sites sustained sig-
nificantly higher ithan persistent sites ðiextinct ¼
0:34 T0:05 versus ipersistent ¼0:13 T0:02, t¼
4:17, P<0:001Þ. The relation between inten-
sity of selection and demographic collapse is
simple. If sustained for decades, the mortality
fraction necessary for selective shifts to new opti-
ma compromises population growth rate precip-
itating local extinction.
If climate change Tmax
continues unabated in
México, 56% of viviparous sites will be extinct
by 2050 and 66% by 2080 (Fig. 2B). For
oviparous sites, 46% will be extinct by 2050
and 61% by 2080. Based on local extinction of
all populations surveyed for species, we project
58% species extinction of Mexican Sceloporus
by 2080. Species extinction (58% by 2080) mir-
rors local population extinction (61 to 66%) be-
cause high-elevation endemics will go completely
extinct as widespread lowland taxa expand to
high elevations.
We used the model to derive global extinc-
tion projections (Fig. 3) for 34 lizard families
(Table 1) with 1216 geo-referenced T
(table S6). Our data include heliotherms that
bask and thermoconformers that do not bask,
but track ambient air and surface temperature.
was obtained from the WorldClim database
(29)at10arc min resolution (1975, 2020, 2050,
and 2080). We used distributional limits of he-
liothermic lizards of the world in 1975 to cal-
ibrate h
by family, which if exceeded at a given
site would precipitate extinction. The extinction
model is easily adapted to thermoconformers that
maintain T
close to T
or retreat when T
and T
(24-hour period), if the cumulative
hours that T
for a thermoconformer at a
given geo-referenced site (table S6) exceeded
the h
of a given lizard family, we assumed it
would go extinct. Given T
at each geo-
referenced site, we computed the h
each species
sustained in 1975, and for each family we used
Department of Ecology and Evolutionary Biology, University of
California, Santa Cruz, CA, 95064, USA.
Laboratorio de
Herpetología, Instituto de Biología, Universidad Nacional
Autónoma de México, D.F., 04510, México.
Department of
Biology, Ohio University, 131 Life Sciences Building, Athens,
OH 45701, USA.
CNRS UMR 6553, Station Biologique,
35380 Paimpont, France.
Laboratorio de Biología de la
Reproducción Animal, Departamento de Biología Comparada,
Facultad de Ciencias, Universidad Nacional Autónoma de
xico, D.F., 04510, México.
Instituto de Ciencias Naturales,
Universidad Nacional de Colombia, Sede Bogotá, Colombia.
Instituto de Ecología, A.C., Miguel de Cervantes No. 120
(Cubículo 30C), Complejo Industrial, C.P. 31109, Chihuahua,
Centro Nacional Patagónico, Consejo Nacional de
Investigaciones Científicas y Técnicas, Blvd. Brown 2915,
U9120ACD, Puerto Madryn, Chubut, Argentina.
Nacional de Ciencias Naturales, CSIC, C/ José Gutiérrez, Abascal
2, 28006 Madrid, Spain.
Universidad de Concepción, Dpto.
Zoología, Casilla 160-C, Concepción, Chile.
Department of
Ecology, Institute of Biology, Universidade do Estado do Rio de
Janeiro, Rua São Francisco Xavier 524, Maracanã 20550-019,
Rio de Janeiro, Brazil.
Instituto de Investigación en Biodiversi-
dad y Medio Ambiente (INIBIOMA), Consejo Nacional de
Investigaciones Científicas y Técnicas, Centro Regional Uni-
versitario Bariloche, Universidad Nacional del Comahue,
Quintral 1250, San Carlos de Bariloche, Río Negro 8400,
Departamento de Herpetología, Museo de
Historia Natural, Universidad Nacional Mayor de San Marcos,
Av. Arenales 1256, Jesús María Apdo 14-0434, Lima 14, Perú.
Laboratoire Ecologie-Evolution, Université UPMC, CNRS UMR
7625, 7 quai Saint Bernard, 75005 Paris, France.
d'Ecologie Expérimentale du CNRS a Moulis USR 2936, Moulis,
09200 Saint-Girons France.
Centre of Excellence in Evolu-
tionary Research, Department of Biological and Environmental
Science, Post Office Box 35, FI-40014, University of Jyväskylä,
School of Biological Sciences, Monash University,
Victoria 3800, Australia.
Department of Biology, Villanova
University, 800 Lancaster Avenue, Villanova, PA 19085, USA.
Bayworld, Post Office Box i13147, Humewood 6013, South
Department of Biology and Bean Life Science Museum,
Brigham Young University, Provo, UT 84602, USA.
*To whom correspondence should be addressed. E-mail:
Present address: Laboratoire d'Etude Environnementales des
Systèmes Anthropisés (LEESA), UFR Sciences, 2 Bd Lavoisier,
49045 Angers cedex 01, France. SCIENCE VOL 328 14 MAY 2010 895
on May 13, 2010 www.sciencemag.orgDownloaded from
the upper 95% confidence level of h
(Table 1)
as the extinction threshold (iteratively estimated,
given global climate surfaces). Calibration with
these 1975 distributional limits for Sceloporus
yields h
= 3.9, which was cross-validated by
= 3.85 computed from observed extinctions
in México (1975 to 2009), and h
= 4, which
was estimated directly from T
at persistent
S. serrifer sites on the verge of extinction.
Fig. 1. (A) Logistic regression of
extinction probability (0 = extant,
1 = extinct) of Sceloporus lizards
and reproductive mode: c
= 7.41,
P=0.025,Delevation (c
P=0.014),Dlatitude (c
0.004), and Dlongitude (not signif-
icant), where Drefers to deviations
from species range midpoints. (B)
Phylogenetic independent contrasts
(PICs) of lineage survival (survival
probability of local populations)
and Delevation (t= 2.15, P=0.03),
Dlatitude (t=3.94,P= 0.0001),
and Dlongitude (t = 2.66, P=
0.009). (C) PICs of lineage surviv-
al, T
(t= 2.32, P= 0.02), T
2.31, P= 0.02), and reproductive
mode (t=2.92, P= 0.005).
Latitude Longitude
PIC Latitude PIC LongitudePIC Elevation
-2000 -1000 0
6 -4 -2 0 2 4 6 8
0 2 4 6-8 -6 -4 -21000
PIC Lineage Survival
PIC Lineage Survival
PIC Lineage Survival
-8 -6 -4 -2 0 2 4 6 8
-1000 0 1000 -6 -4 -2 0 2 4 6
4 -3 -2 -1 0 1 2 3
-10 -5 0 5 10
-0.60 -0.30 0.00 0.30 0.60
PIC Air Temperature (° C)PIC Body Temperature (° C)
PIC Lineage Survival
PIC Lineage Survival
PIC Lineage Survival
PIC Oviparity-Viviparity
Fig. 2. (A) Sustained selection differentials per year required for T
to keep pace with global warming. (B) Extinctions of Mexican Sceloporus lizards
(1975 to 2009, 2009 to 2050, 2050 to 2080).
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As in the validation of Mexican Sceloporus
extinction, we computed h
for temperate lizards
over 2 critical reproductive months, but were
conservative in modeling critical months re-
quired for h
to be exceeded in the equatorial
zone (T12° latitude) where lizards potentially
breed year-round (h
exceeded over 12 months),
and in the wet-dry tropical zone (T12° to 24°
latitude: h
exceeded for 5 to 6 months).
Geo-referenced T
samples indicate that current
(2009) local extinctions average 4% worldwide
(Table 1). Global averages will increase fourfold
to 16% by 2050 and nearly eightfold to 30% by
2080, while equatorial extinctions will reach 23%
by 2050 and 40% by 2080. Assuming reproduc-
tion shifts 1 month earlier in temperate zones [h
1.0 lay date (30)] and proportionately less to the
trade zones (i.e., no shift), 2080 global extinctions
jump to 38% because spring seasons are warm-
ing faster across the globe. Our model is robust
to plasticity in T
(table S7) and initial assump-
Fig. 3. Contour plots of global levels of local extinction for heliothermic lizards (1975 to 2009, 1975 to 2050, 1975 to 2080), assuming hr= 4.55
(23) and various T
values. SCIENCE VOL 328 14 MAY 2010 897
on May 13, 2010 www.sciencemag.orgDownloaded from
tions made for reproductive periods in the tropics.
If h
for equatorial taxa is computed over the 9
hottest months of reproduction, rather than the
conservative assumption of 12 months, global
extinctions increase to 39% by 2080.
The global generality of our model is verified
by concordant distributions of current observed
and predicted local extinctions of lizard biotas
from four other continents (table S7). Our model
pinpoints exact locations of two Liolaemid species
going extinct in South America (Liolaemus lutzae,
Phymaturus tenebrosus:c
=32.1,P< 0.0001).
In addition, the model predicts recent (2009)
extinctions among 24 resurveyed populations of
L. lutzae (c
=8.8,P= 0.003). In Europe, our
Table 1. Sample size, T
range, TbTSE,Tmax ,h
for 34 lizard
families. Local extinction rates are based on geo-referenced T
data and a
physiological model of extinction. We also validated model predictions of local
extinction risk in 2080 for six families: 57% (T3, n= 200) for Mexican
Phrynosomatidae, 13% (T2, n= 3155) for South American Liolaemidae, 56%
(T5, n= 117) for European Lacertidae (L. vivipara), 13% (T2, n= 1438) for
African Cordylidae + Gerrhosauridae, 57% (T4, n= 125) on Madagascar, and
10% (T1, n= 2841) for Australian Egernia Group lizards species. Estimates of
species extinctions in each family are derived from the relationships for
extinction of all local populations for these six families (table S8).
Family nT
range Tb±SE Tmax h
Mode of
Local extinction levels Species extinction
2009 2050 2080 2050 2080
Agamidae 74 19.043.8 35.6T0.34 29.8 7.0 Heliothermic 381 0.000 0.169 0.292 0.059 0.266
Amphisbaenidae 2 21.121.2 21.2T0.05 28.8 16.2 Fossorial
160 0.000 0.000 0.250 0.000 0.228
Anguidae 10 21.432.3 26.7T0.94 20.9 5.6 Heliothermic, a few
112 0.111 0.111 0.111 0.039 0.101
Annielliidae 2 21.023.6 22.3T2.09 20.5 11.5 Fossorial
2 0.000 0.000 0.000 0.000 0.000
Chamaeleonidae 18 22.233.5 30.0T0.70 26.8 12.0 Forest
161 0.063 0.063 0.063 0.022 0.057
Cordylidae 11 27.833.8 31.5T0.82 23.6 6.8 Heliothermic 54 0.000 0.000 0.200 0.000 0.182
Corytophanidae 4 26.035.0 31.9T1.48 29.4 13.4 Forest
9 0.250 0.250 0.250 0.088 0.228
Crotaphytidae 23 35.538.9 37.3T0.62 23.3 1.2 Heliothermic 12 0.111 0.167 0.222 0.059 0.202
Carphodactylidae 11 15.135.5 24.5T1.59 34.7 10.9 Thermoconformer 30 0.350 0.820 0.820 0.289 0.748
Diplodactylidae 42 16.935.9 27.3T0.59 31.2 10.9 Thermoconformer 141 0.070 0.190 0.190 0.067 0.173
Eublepharidae 18 26.633.0 28.5T0.44 32.9 10.9 Thermoconformer 28 0.060 0.240 0.240 0.084 0.219
Gekkonidae 40 26.035.3 30.1T0.58 32.6 10.9 Thermoconformer 700 0.000 0.000 0.000 0.000 0.000
Phyllodactylidae 13 16.638.9 30.6T1.42 30.4 10.9 Thermoconformer 100 0.000 0.000 0.000 0.000 0.000
Pygopodidae 21 24.935.1 25.4T0.46 17.9 11.5 Fossorial
38 0.000 0.000 0.000 0.000 0.000
Sphaerodactylidae 19 25.338.6 30.2T0.75 33.0 10.9 Thermoconformer 200 0.000 0.000 0.000 0.000 0.000
Gerrhosauridae 4 31.833.3 32.6T2.09 28.3 6.8 Heliothermic 16 0.333 0.333 0.333 0.117 0.304
Gymnophthalmidae 20 21.529.9 26.4T0.66 30.3 13.8 Leaf litter
193 0.095 0.333 0.667 0.117 0.608
Helodermatidae 2 29.430.2 29.8T2.09 24.8 2.7 Heliothermic/thermal
2 0.000 0.000 1.000 0.000 0.912
Iguanidae 20 32.942.1 37.3T0.79 28.1 3.7 Heliothermic 36 0.143 0.143 0.286 0.050 0.261
Lacertidae 89 26.740.2 35.4T0.31 25.6 3.1 Heliothermic 279 0.034 0.241 0.460 0.085 0.420
Lanthanotidae 1 28.0 30.5 9.4 Forest
1 1.000 1.000 1.000 0.352 0.912
Leiocephalidae 1 36.3 31.7 2.8 Heliothermic 29 0.000 1.000 1.000 0.352 0.912
Liolaemidae 125 24.440.8 33.7T0.27 17.8 1.4 Heliothermic 219 0.027 0.071 0.107 0.025 0.098
Opluridae 3 36.239.8 37.7T1.71 31.8 4.0 Heliothermic 7 0.333 0.667 0.667 0.235 0.608
Phrynosomatidae 215 26.841.5 35.2T0.20 24.9 3.9 Heliothermic 125 0.037 0.087 0.149 0.031 0.136
Polychrotidae 121 19.635.0 29.6T0.27 29.6 14.4 Forest
393 0.018 0.043 0.068 0.015 0.062
Scincidae 210 20.338.0 32.9T0.20 26.5 6.2 Heliothermic, a few
1305 0.015 0.092 0.308 0.032 0.281
Sphenodontidae 1 14.521.0 14.5T2.09 18.0 10.7 Nocturnal
1 0.000 0.000 0.000 0.000 0.000
Teiidae 91 26.841.3 37.9T0.31 29.0 4.2 Heliothermic 121 0.012 0.136 0.210 0.048 0.192
Trogonophidae 2 22.022.5 22.3T0.25 28.8 16.2 Fossorial
8 0.000 0.000 0.000 0.000 0.000
Tropiduridae 72 26.238.0 33.7T0.35 28.3 7.7 Heliothermic 111 0.043 0.058 0.087 0.020 0.079
Varanidae 46 28.838.9 35.8T0.44 29.7 4.6 Heliothermic/thermal
68 0.001 0.023 0.178 0.008 0.162
Xantusidae 8 18.733.0 25.4T1.32 20.7 0.0 Thigmothermic
29 0.000 0.000 0.000 0.000 0.000
Xenosauridae 5 20.325.6 23.2T1.48 26.4 11.4 Thigmothermic
6 0.200 0.200 0.600 0.070 0.547
14 MAY 2010 VOL 328 SCIENCE www.sciencemag.org898
on May 13, 2010 www.sciencemag.orgDownloaded from
resurvey of Lacerta vivipara revealed 14 extinct
sites out of 46 (30%), which are predicted quite
precisely by the model (c
=24.4,P< 0.001). In
Australia, the model pinpoints 2009 extinctions
of Liopholis slateri (c
= 17.8, P< 0.00001) and
2009 extinctions of Liopholis kintorei (c
= 3.93,
P= 0.047). In Africa, analysis of Gerrhosauridae
and Cordylidae at 165 sites predicts <1% extinc-
tions, and yet the model pinpoints the single ex-
tinction reported by 2009 (exact P-value = 0.006).
We temper this value with extinction projections
of 23% for 2009 at Malagasy Gerrhosauridae sites,
which is validated by the observed 21% levels
of local extinction across several lizard families
in Madagascar nature reserves (23).
Thermoconforming lizards have been posited
(31) to be more vulnerable to climate change
relative to heliotherms. Even though Tbof ther-
moconformers (27.5°C T1.8°) is significantly
less than Tbof heliotherms (33.5ºC T1.3, t=
2.66, P< 0.02, n= 34 families; Table 1), PICs
show that extinction risk was unrelated to ther-
moregulatory mode (fig. S8), but was signifi-
cantly increased by low Tb,lowh
, and high
Tmax. The similar level of local extinctions in
2009 for Malagasy thermoconformers (21%, n=
63) and heliotherms [21%, n= 34; (23)] supports
this view. Evolved changes in thermoregulatory
mode, T
, lay date, and habitat preference set
risk as T
rises, but owing to trade-offs, T
cannot be simultaneously maximized, hence
extinction risk is independent of mode (fig. S8).
Moreover, extinction risk is not higher for con-
formers because heliotherms inhabit equatorial
regions (i.e., sub-Saharan Africa) that are un-
available to thermoconformers [a factor not con-
sideredby(31)orothermodels(10)], and these
areas are warming rapidly (Fig. 3).
Our model, based on T
in activity during
reproduction, and timing of breeding, assesses
salient adaptations that affect thermal extinc-
tions. Concordant verification of 2009 levels of
local lizard extinction in North and South Amer-
ica, Europe, Africa, and Australia confirm that
extinctions span tropical, temperate, rainforest,
and desert habitats. Estimates of evolutionary
rates required to keep pace with global change
indicate that sustained and intense selection
compromises population growth rates, precip-
itating extinctions. Probability of local extinction
is projected to result in species extinction prob-
abilities of 6% by 2050 and 20% by 2080 (table
S8). Range shifts only trivially offset losses, be-
cause widespread species with high T
shift to
ranges of endemics, thereby accelerating their
demise. Although global efforts to reduce CO
may avert 2080 scenarios, 2050 projections are
unlikely to be avoided; deceleration in Tmax
atmospheric CO
storage by decades (4). There-
fore, our findings indicate that lizards have al-
ready crossed a threshold for extinctions.
References and Notes
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32. Research of B.S. was funded by the National Geographic
Society, UC Mexus, UCSC Committee-On-Research, NSF
awards (DEB 0108577, IBN 0213179, LTREB DEB
051597), CNRS fellowships, and visiting professorships
(Museum Nationale dHistoire Naturelle, Université Paris
6, Université Paul Sabatier Toulouse III), PAPIIT-UNAM
IN213405 and 224208 to F.M.-C., a Université Paul
Sabatier Toulouse III Visiting Professorship to D.B.M.,
CONACYT grants (4171N and 52852Q) to M.V.-S.C.,
grant CONACYT-SEP (43142-Q) to H.G., a CONACYT
fellowship to R.N.M.-L., CNRS funding to B.H., and M.M.,
Biodivera: Tenlamas and from ANR Blanche: DIAME
to J.C., CONICET grants to L.J.A. and M.M., FONDYCET
1090664 grants to P.V.S., CGL2005-03156 and
CLG2008-04164 grant from SMSI to I.J.R., APCT-
PICT1086 grant to N.I., scholarships and grants from
Universidad Nacional Autónoma de México and American
Museum of Natural History to M.V.-S.C., Academy of
Finland grant (108955) to T.A.O., Australian Research
Council grants to D.G.C., NSF awards DEB 0515909
and 0844523 to A.M.B., NSF award OISE 0530267,
PIRE-Patagonia grant to J.W.S., L.J.A., M.M., and P.V.S.
and Brigham Young University funding (Biology
Department, Kennedy Center for International Studies,
Bean Life Science Museum) to J.W.S.
Supporting Online Material
Materials and Methods
Figs. S1 to S9
Tables S1 to S8
16 November 2009; accepted 7 April 2010
Carbon Dioxide Enrichment Inhibits
Nitrate Assimilation in Wheat
and Arabidopsis
Arnold J. Bloom,*Martin Burger,Jose Salvador Rubio Asensio, Asaph B. Cousins
The concentration of carbon dioxide in Earths atmosphere may double by the end of the
21st century. The response of higher plants to a carbon dioxide doubling often includes a decline
in their nitrogen status, but the reasons for this decline have been uncertain. We used five
independent methods with wheat and Arabidopsis to show that atmospheric carbon dioxide
enrichment inhibited the assimilation of nitrate into organic nitrogen compounds. This inhibition
may be largely responsible for carbon dioxide acclimation, the decrease in photosynthesis and
growth of plants conducting C
carbon fixation after long exposures (days to years) to carbon
dioxide enrichment. These results suggest that the relative availability of soil ammonium and
nitrate to most plants will become increasingly important in determining their productivity
as well as their quality as food.
The concentration of CO
in Earthsatmo-
sphere has increased from about 280 to 390
mmol CO
per mol of atmosphere (mmol
) since 1800, and predictions are that it will
reach between 530 and 970 mmol mol
by the end
of the 21st century (1). Plants could mitigate these
changes through photosynthetic conversion of
atmospheric CO
into carbohydrates and other
organic compounds, yet the potential for this miti-
gation remains uncertain. Photorespiration is the
biochemical pathway in which the chloroplast
enzyme Rubisco catalyzes the oxidation of the
high-energy substrate RuBP rather than cata-
lyzes the carboxylation of RuBP through the C
carbon-fixation pathway (2). Elevated CO
Department of Plant Sciences, University of California at Davis,
Davis, CA 95616, USA.
*To whom correspondence should be addressed. E-mail:
Present address: Department of Land, Air and Water Resources,
University of California at Davis, Davis, CA 95616, USA.
Present address: School of Biological Sciences, Post Office
Box 646340, Washington State University, Pullman, WA
991646340, USA. SCIENCE VOL 328 14 MAY 2010 899
on May 13, 2010 www.sciencemag.orgDownloaded from
... Therefore, plastic thermoregulatory behavior may buffer populations against selection on these traits and slow down population shifts toward higher thermal optima and larger tolerances (the "Bogert effect"; Gunderson & Stillman, 2015;Huey et al., 2003;Logan et al., 2019). Given the pessimistic forecasts for ectotherm species (Deutsch et al., 2008;Sinervo et al., 2010), an important challenge is to accurately estimate the complementary and conflicting contributions of plastic and evolutionary responses of thermal phenotypes to species adaptation. ...
... Importantly, maximum temperatures are below the critical thermal limits of common lizards (Van Damme et al., 1991), and the mesocosms provide many opportunities for thermal refuges, thus selection is unlikely to act through strong physiological damage. However, climate warming could act through increased metabolic demands increasing the risk of physiological exhaustion, potential increases in intraspecific competition, or reduced thermal windows for activity and foraging before retreating into thermal refuges (Sinervo et al., 2010), which could all affect lizard survival and mediate selection on thermal traits. ...
... If thermal traits are partly genetically determined, warmer climates may exert an upward selection on these thermal traits that favors higher thermal optima in warmer environments, and species adaptation to warmer climates. Current evidence suggests that there is low additive genetic variation in behaviors related to thermal preference (Logan et al., 2018;Paranjpe et al., 2013), which dramatically limits the rate of evolutionary response under projected levels of climate change (Sinervo et al., 2010), while melanism is more heritable in several species (Roulin, 2016). Here, additive genetic effects inherited from both parents, and to a lesser extent, maternal effects, explained a proportion of the variance in the thermal preference, and dorsal color traits (darkness and contrast). ...
Facing warming environments, species can exhibit plastic or microevolutionary changes in their thermal physiology to adapt to novel climates. Here, using semi-natural mesocosms, we experimentally investigated over two successive years whether a 2°C-warmer climate produces selective and inter- and intragenerational plastic changes in the thermal traits (preferred temperature and dorsal colouration) of the lizard Zootoca vivipara. In a warmer climate, the dorsal darkness, dorsal contrast and preferred temperature of adults plastically decreased and covariances between these traits were disrupted. While selection gradients were overall weak, selection gradients for darkness were slightly different between climates and in the opposite direction to plastic changes. Contrary to adults, male juveniles were darker in warmer climates either through plasticity or selection and this effect was strengthened by intergenerational plasticity when juveniles' mothers also experienced warmer climates. While the plastic changes in adult thermal traits alleviate the immediate overheating costs of warming, its opposite direction to selective gradients and to juveniles' phenotypic responses may slow down evolutionary shifts towards phenotypes that are better adapted to future climates. Our study demonstrates the importance of considering inter- and intragenerational plasticity along with selective processes to better understand adaptation and population dynamics in light of climate change.
... (iii) Bioregions of reptiles were compared to Holt et al. (2013) regionalizations at the two nested levels of realms and regions, calculating the general similarity of the spatial structure of bioregions and the correlation between the occurrence of terrestrial boundaries across different clades. (Sinervo et al., 2010). We further predict that reptiles are strongly affected by physical barriers due to their small size, low metabolic rates and lack of wings, all of which make them generally poor dispersers (Esquerré et al., 2019); (2) Amphibians respond to different factors compared with mammals and birds (see Ficetola et al., 2021). ...
... Sharp climatic transitions are a major physiological constraint for ectotherms such as amphibians and reptiles, as they often have narrow climatic niches. Ectotherm metabolism is more dependent on climate compared with endothermic vertebrates, and variation in temperature and water availability poses major constraints to their activity and to embryonic development (Buckley et al., 2012;Cunningham et al., 2016;Ma et al., 2018;Sinervo et al., 2010). Nevertheless, reptile biogeographical boundaries were also strongly related to physical barriers, resembling mammals and birds (see Figure 3 and Ficetola et al., 2021). ...
Full-text available
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Abstract Aim: The identification of biogeographical zones has been fundamental in broadscale biodiversity analyses over the last 150 years. If processes underlying bioregionaliza-tion, such as climatic differences, tectonics and physical barriers, are consistent across vertebrate clades, we expect that groups with more similar ecological characteristics would show more similar bioregions. Lack of data has so far hampered the delineation of global bioregions for reptiles. Therefore, we integrated comprehensive geographic distribution and phylogenetic data of lepidosaurian reptiles to delineate global reptile bioregions, compare determinants of biogeographical boundaries across terrestrial vertebrates and test whether clades showing similar responses to environmental factors also show more similar bioregions. Location: Global. Time Period: Present. Major Taxa Studied: Reptiles, amphibians, birds, mammals. Methods: For reptiles, we used phylogenetic beta diversity to quantify changes in community composition, and hierarchical clustering to identify biogeographic 'realms' and 'regions'. Then, we assessed the determinants of biogeographical boundaries using spatially explicit regression models, testing the effect of climatic factors, physical barriers and tectonics. Bioregions of reptiles were compared to those of other vertebrate clades by testing the overall similarity of the spatial structure of bioregions, and the match of the position of biogeographical boundaries. Results: For reptiles, we identified 24 evolutionarily unique regions, nested within 14 realms. Biogeographical boundaries of reptiles were related to both climatic factors and past tectonic movements. Bioregions were very consistent across vertebrate clades. Bioregions of reptiles and mammals showed the highest similarity, followed by reptiles/birds and mammals/birds while amphibian bioregions were less similar to those of the other clades. Main Conclusions: The overall high similarity among bioregions suggests that biore-gionalization was affected by similar underlying processes across terrestrial vertebrates. Nevertheless, clades with different eco-physiological characteristics respond
... Otro factor importante de considerar es que el intervalo de distribución altitudinal de S. aeneus y S. bicanthalis se solapa en algunas cotas de elevación en diferentes zonas geográficas, ya que la especie vivípara se restringe al intervalo vertical comprendido entre los 1,600 a 4,500 m snm; no obstante, se reconocen otras poblaciones de esta especie vivípara en elevaciones menores (Chávez-León y Lemos-Espinal, 2021), mientras que la especie ovípara se encuentra entre los 1,858 y los 4,000 m snm (Chávez-León y Lemos-Espinal, 2021;Meza, 2007;Sinervo et al., 2010). ...
Sceloporus aeneus y Sceloporus bicanthalis son especies de reciente evolución, similares en morfología e historia de vida, pero difieren en el modo reproductor y número de escamas cantales. Sin embargo, este último carácter es altamente variable y es el único, a una escala morfológica, que se ha usado hasta la fecha para diferenciarlas. En el presente trabajo se analizó el grado de variación morfológica de las escamas cefálicas, mediante morfometría geométrica y estadística multivariada, para determinar si el uso de estos métodos permite separar con mayor precisión ambas especies. Para ello, se utilizaron fotografías digitales de S. aeneus y S. bicanthalis y se colocaron marcas en escamas de la región dorsal, ventral y lateral de la cabeza. Los resultados muestran diferencias significativas en la forma de las escamas entre ambas especies para todas las vistas, de manera que cada especie presenta un morfotipo definido en lo que respecta a la escutelación del cráneo. El análisis sugiere que ambas especies pueden ser identificadas mediante variaciones en la forma de las escamas parietal e interparietal y no por el número de escamas cantales.
... However, previous work by Germano and Rathbun (2016) suggests that while the home ranges of G. sila contain more shrub habitat, it is still possible for this species to travel and establish home ranges in the absence of shrubs. Challenges to thermoregulation-and dependency on the local environment for refuge-for lizards, including G. sila, are becoming more acute as global temperatures and the likelihood of drought events increase (Dell et al., 2014;Lortie et al., 2020;Sinervo et al., 2010;Westphal et al., 2016). Lortie et al. (2020) found that there was a significant association between increasing shrub cover, the Normalized Difference Vegetation Index (NDVI), and G. sila presence-that is, an individual observation of each individual during data collection. ...
Full-text available
Positive associations between animals and foundational shrub species are frequent in desert ecosystems for shelter, resources, refuge, and other key ecological processes. Herein, we tested the impact of the density of the shrub species Ephedra californica on the presence and habitat use of the federally endangered lizard species, Gambelia sila. To do this, we used a 3-year radio telemetry dataset and satellite-based counts of shrub density across sites at the Carrizo Plain National Monument in San Luis Obispo County, CA. The effect of shrub density on lizard presence was contrasted with previous shrub cover analyses to determine whether measures of shrub density were superior to shrub cover in predicting lizard presence. Increasing shrub density increased lizard presence. As shrub density increased, lizards were located more frequently “above ground” versus “below ground” in burrows. Male lizards had significantly larger home ranges than females, but both sexes were similarly associated with increasing shrub densities. Shrub density and shrub cover models did not significantly differ in their prediction of lizard presence. These findings suggest that both habitat measures are effective analogs and that ecologically, both cover and the density of foundation shrub species are key factors for some desert lizards.
... This species uses leaf-litter as the main microhabitat to develop its vital activities (Rodrigues, 2003;Silva et al., 2015). The habitat changes associated with changes in conditions and resource loss should influence C. meridionalis survival (Sinervo et al., 2010;Sutton et al., 2014). Finally, the increase in abundance of lizards in more anthropized areas has also been identified in other lizard studies (e.g. ...
Anthropogenic changes in habitats are one of the main threats to biodiversity. Understanding how species diversity and their functions are affected by these changes is crucial to assess environmental impacts. In this work, we aim to understand how lizard composition, taxonomic and functional diversity respond to differences in native vegetation regeneration stages (conserved vegetation and open secondary vegetation) and agricultural land use in different vegetation types (Caatinga sensu stricto, Cerrado sensu stricto and Relictual Humid Forest) in Caatinga domain, Brazil. In more degraded areas (open secondary vegetation and agricultural areas), we found a decline in species evenness, shown by greater dominance of few species. Moreover, we found a lower functional evenness in agricultural areas than in areas of conserved vegetation, which suggests that a smaller portion of functional traits present greater dominance in more anthropized areas. We did not detect any significant differences in species richness, but we did registered differences in species composition in Relictual Humid Forest. Contrary to our expectations, lizard abundance was also greater in more degraded areas, probably as a result of the increased abundance of species benefited by anthropization. In this work, we advance the knowledge of how anthropogenic changes influence lizard diversity and emphasize the importance of analysing different facets of diversity and different habitat environments to understand how anthropization affects patterns in community ecology.
... Here, we aim to determine how early developmental environments affect thermal physiology (CT max and thermal preference: T pref ) in reptiles. CT max and T pref are two common thermal indices used as proxies for how the environment influences individual fitness and are used to predict how species distributions are predicted to shift with climate change [3,24,25]. We first conduct a laboratory experiment to test how maternal investment and developmental temperature both influence CT max and T pref in a common skink (Lampropholis delicata). ...
On a global scale, organisms face significant challenges due to climate change and anthropogenic disturbance. In many ectotherms, developmental and physiological processes are sensitive to changes in temperature and resources. Developmental plasticity in thermal physiology may provide adaptive advantages to environmental extremes if early environmental conditions are predictive of late-life environments. Here, we conducted a laboratory experiment to test how developmental temperature and maternal resource investment influence thermal physiological traits (critical thermal maximum: CTmax and thermal preference: Tpref) in a common skink (Lampropholis delicata). We then compared our experimental findings more broadly across reptiles (snakes, lizards and turtles) using meta-analysis. In both our experimental study and meta-analysis, we did not find evidence that developmental environments influence CTmax or Tpref. Furthermore, the effects of developmental environments on thermal physiology did not vary by age, taxon or climate zone (temperate/tropical). Overall, the magnitude of developmental plasticity on thermal physiology appears to be limited across reptile taxa suggesting that behavioural or evolutionary processes may be more important. However, there is a paucity of information across most reptile taxa, and a broader focus on thermal performance curves themselves will be critical in understanding the impacts of changing thermal conditions on reptiles in the future.
Full-text available
The global-scale decline of animal biodiversity ('defaunation') represents one of the most alarming consequences of human impacts on the planet. The quantification of this extinction crisis has traditionally relied on the use of IUCN Red List conservation categories assigned to each assessed species. This approach reveals that a quarter of the world's animal species are currently threatened with extinction, and 1% have been declared extinct. However, extinctions are preceded by progressive population declines through time that leave demographic 'footprints' that can alert us about the trajectories of species towards extinction. Therefore, an exclusive focus on IUCN conservation categories, without consideration of dynamic population trends, may underestimate the true extent of the processes of ongoing extinctions across nature. In fact, emerging evidence (e.g. the Living Planet Report), reveals a widespread tendency for sustained demographic declines (an average 69% decline in population abundances) of species globally. Yet, animal species are not only declining. Many species worldwide exhibit stable populations, while others are even thriving. Here, using population trend data for >71,000 animal species spanning all five groups of vertebrates (mammals, birds, reptiles, amphibians and fishes) and insects, we provide a comprehensive global-scale assessment of the diversity of population trends across species undergoing not only declines, but also population stability and increases. We show a widespread global erosion of species, with 48% undergoing declines, while 49% and 3% of species currently remain stable or are increasing, respectively. Geographically, we reveal an intriguing pattern similar to that of threatened species, whereby declines tend to concentrate around tropical regions, whereas stability and increases show a tendency to expand towards temperate climates. Importantly, we find that for species currently classed by the IUCN Red List as 'non-threatened', 33% are declining. Critically, in contrast with previous mass extinction events, our assessment shows that the Anthropocene extinction crisis is undergoing a rapid biodiversity imbalance, with levels of declines (a symptom of extinction) greatly exceeding levels of increases (a symptom of ecological expansion and potentially of evolution) for all groups. Our study contributes a further signal indicating that global biodiversity is entering a mass extinction, with ecosystem heterogeneity and functioning, biodiversity persistence, and human well-being under increasing threat.
Since 1970, there has been an overall decline in wildlife populations in the order of 52%. Freshwater species populations have declined by 76%; species populations in Central and South America have declined by 83%; and in the Indo-Pacific by 67%. These are often not complete extinctions, but large declines in the numbers of animals in each species, as well as habitat loss. This presents us with a tremendous opportunity, before it is too late to rescue many species. This book documents the present state of wildlife on a global scale, using a taxonomic approach, and serving as a one stop place for people involved in conservation to be able to find out what is in decline, and the success stories that have occurred to bring back species from the brink of extinction - primarily due to conservation management techniques - as models for what we might achieve in the future.
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The range extension of animals is influenced by various factors, particularly environmental variables and ecological requirements. In this study, we have attempted to quantify the potential current distribution range of the Burmese Python Python bivittatus in and around the Ganga Basin. We collected the Burmese Python sightings between 2007 and 2022 from various direct and indirect sources and recorded 38 individuals, including eight females and five males; the rest were not examined for their sex. Out of these, 12 individuals were rescued from human habitations. Most python sightings were observed in Uttarakhand and Uttar Pradesh (n = 12 each), followed by Bihar (n = 6). The expanded minimum convex polygon (MCP) range was calculated as 60,534.2 km2. In addition, we quantified the potential current distribution status of this species using 19 bioclimatic variables with the help of MaxEnt software and the SDM toolbox in Arc GIS. The suitable area for the python distribution was calculated as 1,03,547 km2. We found that the following variables influenced the python distribution in the range extended landscape: Annual Mean Temperature (20.9%), Precipitation of Wettest Quarter (6.4 %), Precipitation of Driest Quarter (30.1 %), Precipitation of Warmest Quarter (0.3%), Isothermality (0.1%), Temperature Annual Range (18.7 %), Mean Temperature of Wettest Quarter (11.4 %), Mean Temperature of Driest Quarter (2.2 %), Land use/land cover (3.3 %), and Elevation (6.6 %). These results will support the field managers in rescuing individuals from conflict areas and rehabilitating them based on the appropriate geographical region.
Herein we review our work involving dispersed adrenocortical cells from several lizard species: the Eastern Fence Lizard (Sceloporus undulatus), Yarrow's Spiny Lizard (Sceloporus jarrovii), Striped Plateau Lizard (Sceloporus virgatus) and the Yucatán Banded Gecko (Coleonyx elegans). Early work demonstrated changes in steroidogenic function of adrenocortical cells derived from adult S. undulatus associated with seasonal interactions with sex. However, new information suggests that both sexes operate within the same steroidogenic budget over season. The observed sex effect was further explored in orchiectomized and ovariectomized lizards, some supported with exogenous testosterone. Overall, a suppressive effect of testosterone was evident, especially in cells from C. elegans. Life stage added to this complex picture of adrenal steroidogenic function. This was evident when sexually mature and immature Sceloporus lizards were subjected to a nutritional stressor, cricket restriction/deprivation. There were divergent patterns of corticosterone, aldosterone, and progesterone responses and associated sensitivities of each to corticotropin (ACTH). Finally, we provide strong evidence that there are multiple, labile subpopulations of adrenocortical cells. We conclude that the rapid (days) remodeling of adrenocortical steroidogenic function through fluctuating cell subpopulations drives the circulating corticosteroid profile of Sceloporus lizard species. Interestingly, progesterone and aldosterone may be more important with corticosterone serving as essential supportive background. In the wild, the flux in adrenocortical cell subpopulations may be adversely susceptible to climate-change related disruptions in food sources and to xenobiotic/endocrine-disrupting chemicals. We urge further studies using native lizard species as bioindicators of local pollutants and as models to examine the broader eco-exposome.
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The impact of anthropogenic climate change on terrestrial organisms is often predicted to increase with latitude, in parallel with the rate of warming. Yet the biological impact of rising temperatures also depends on the physiological sensitivity of organisms to temperature change. We integrate empirical fitness curves describing the thermal tolerance of terrestrial insects from around the world with the projected geographic distribution of climate change for the next century to estimate the direct impact of warming on insect fitness across latitude. The results show that warming in the tropics, although relatively small in magnitude, is likely to have the most deleterious consequences because tropical insects are relatively sensitive to temperature change and are currently living very close to their optimal temperature. In contrast, species at higher latitudes have broader thermal tolerance and are living in climates that are currently cooler than their physiological optima, so that warming may even enhance their fitness. Available thermal tolerance data for several vertebrate taxa exhibit similar patterns, suggesting that these results are general for terrestrial ectotherms. Our analyses imply that, in the absence of ameliorating factors such as migration and adaptation, the greatest extinction risks from global warming may be in the tropics, where biological diversity is also greatest. • biodiversity • fitness • global warming • physiology • tropical
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Both male and female Sceloporus jarrovi thermoregulate on every day during the summer when weather is suitable for lizard activity. Pregnant females, however, regulate a lower body temperature (x̄ 32.0 C) than do males or post-parturient females (x̄ 34.5 C) and, using the standard deviation about the mean as a measure of precision, also thermoregulate more carefully (x̄SD: females = 0.9 C, males and post-parturient females = 1.4 C). The variability in mean body temperature both within and between pregnant and non-pregnant lizards is related to shifts in the maximum and minimum body temperatures voluntarily tolerated in the field. Demographic and climatic considerations that make early birth advantageous at both high and low altitudes result in the prediction that lizards should regulate the highest body temperature possible during pregnancy. The shift to a lower preferred body temperature by female S. jarrovi during pregnancy could thus reflect a compromise by the female between two conflicting thermal optima, her own preferred body temperature and a lower optimum temperature for development of her embryos.
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Describes how local environmental conditions could cause flip-flops in population dynamics depending on the dynamics of the driving variables. More appropriate models for animal metabolic heat production and internal temperature profiles illustrate shortcomings of older (and simpler) resistance and capacitance models. Components of the heat- and mass-balance equations for whole animals include recent physiological and behavioral data relating to food ingestion and digestion and water loss. Water loss rates show year-to-year variability in a lizard population and are affected by wind speed, air temperature, and radiant fluxes. Sensitivity analyses indicate the effects of air, radiant temperature, and wind speed on growth and reproductive potential for Sceloporus undulatus. Estimations of metabolism and water loss outdoors made on the basis of climate measurements (for microclimate-lizard calculations) compare favorably with measurements of doubly labeled water. Calculated growth and reproductive potential in lizards owing to changes in altitude and climate illustrate how subtle changes in behavior or climate can give either increasing or decreasing growth or reproductive rates with increasing elevation. Growth or reproductive potential calculations based on only laboratory data can yield opposite predictions from those based on combinations of laboratory data and heat- and mass-transfer models for altitude effects on growth or reproductive potential. -from Author
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Male Callosobruchus maculatus F. (Coleoptera: Bruchidae) inseminate more sperm than females can effectively store in their spermathecae. This study examines the adaptive significance of excess sperm transfer by measuring components of male and female reproductive success in response to manipulating the number of sperm inseminated. The number of sperm transferred during copulation was reduced from 56,000 4,462 to 8,7001,194 by sequentially mating males to virgin females. Reducing the number of sperm inseminated by the first male to mate had no effect on the extent of sperm precedence, but reducing the number of sperm inseminated by the second male resulted in a significant reduction in the extent of sperm precedence. When large numbers of sperm are inseminated the remating refractory period of females is increased. These results indicate that males transferring large numbers of sperm during copulation have a two-fold advantage at fertilization; they are more effective at preempting previously stored sperm and they are likely to father more offspring by delaying the time of female remating. The transfer of excess sperm does not appear to serve as nonpromiscuous male mating effort; the number of eggs laid, their fertility and the subsequent survival of zygotes were unaffected by manipulating the number of sperm inseminated. The underlying mechanisms of sperm precedence were also examined. Simple models of sperm displacement failed to accurately predict the patterns of sperm precedence observed in this species. However, the results do not provide conclusive evidence against the models but rather serve to highlight our limited understanding of the movement of sperm within the female's reproductive tract.
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This paper examines different concepts of a ‘warming commitment’ which is often used in various ways to describe or imply that a certain level of warming is irrevocably committed to over time frames such as the next 50 to 100 years, or longer. We review and quantify four different concepts, namely (1) a ‘constant emission warming commitment’, (2) a ‘present forcing warming commitment’, (3) a‘zero emission (geophysical) warming commitment’ and (4) a ‘feasible scenario warming commitment’. While a ‘feasible scenario warming commitment’ is probably the most relevant one for policy making, it depends centrally on key assumptions as to the technical, economic and political feasibility of future greenhouse gas emission reductions. This issue is of direct policy relevance when one considers that the 2002 global mean temperatures were 0.8± 0.2 ∘C above the pre-industrial (1861–1890) mean and the European Union has a stated goal of limiting warming to 2 ∘C above the pre-industrial mean: What is the risk that we are committed to overshoot 2 ∘C? Using a simple climate model (MAGICC) for probabilistic computations based on the conventional IPCC uncertainty range for climate sensitivity (1.5 to 4.5 ∘C), we found that (1) a constant emission scenario is virtually certain to overshoot 2 ∘C with a central estimate of 2.0 ∘C by 2100 (4.2 ∘C by 2400). (2) For the present radiative forcing levels it seems unlikely that 2 ∘C are overshoot. (central warming estimate 1.1 ∘C by 2100 and 1.2 ∘C by 2400 with ∼10% probability of overshooting 2 ∘C). However, the risk of overshooting is increasing rapidly if radiative forcing is stabilized much above 400 ppm CO2 equivalence (1.95 W/m2) in the long-term. (3) From a geophysical point of view, if all human-induced emissions were ceased tomorrow, it seems ‘exceptionally unlikely’ that 2 ∘C will be overshoot (central estimate: 0.7 ∘C by 2100; 0.4 ∘C by 2400). (4) Assuming future emissions according to the lower end of published mitigation scenarios (350 ppm CO2eq to 450 ppm CO2eq) provides the central temperature projections are 1.5 to 2.1 ∘C by 2100 (1.5 to 2.0 ∘C by 2400) with a risk of overshooting 2 ∘C between 10 and 50% by 2100 and 1–32% in equilibrium. Furthermore, we quantify the ‘avoidable warming’ to be 0.16–0.26 ∘C for every 100 GtC of avoided CO2 emissions – based on a range of published mitigation scenarios.
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We developed interpolated climate surfaces for global land areas (excluding Antarctica) at a spatial resolution of 30 arc s (often referred to as 1-km spatial resolution). The climate elements considered were monthly precipitation and mean, minimum, and maximum temperature. Input data were gathered from a variety of sources and, where possible, were restricted to records from the 1950-2000 period. We used the thin-plate smoothing spline algorithm implemented in the ANUSPLIN package for interpolation, using latitude, longitude, and elevation as independent variables. We quantified uncertainty arising from the input data and the interpolation by mapping weather station density, elevation bias in the weather stations, and elevation variation within grid cells and through data partitioning and cross validation. Elevation bias tended to be negative (stations lower than expected) at high latitudes but positive in the tropics. Uncertainty is highest in mountainous and in poorly sampled areas. Data partitioning showed high uncertainty of the surfaces on isolated islands, e.g. in the Pacific. Aggregating the elevation and climate data to 10 arc min resolution showed an enormous variation within grid cells, illustrating the value of high-resolution surfaces. A comparison with an existing data set at 10 arc min resolution showed overall agreement, but with significant variation in some regions. A comparison with two high-resolution data sets for the United States also identified areas with large local differences, particularly in mountainous areas. Compared to previous global climatologies, ours has the following advantages: the data are at a higher spatial resolution (400 times greater or more); more weather station records were used; improved elevation data were used; and more information about spatial patterns of uncertainty in the data is available. Owing to the overall low density of available climate stations, our surfaces do not capture of all variation that may occur at a resolution of 1 km, particularly of precipitation in mountainous areas. In future work, such variation might be captured through knowledge-based methods and inclusion of additional co-variates, particularly layers obtained through remote sensing.
For many years plant ecologists have espoused the notion that habitats differ in an intrinsic quality that has been called favorableness. Here I point out that the concept of favorableness is circular and counterproductive. I develop the thesis that species diversity is determined by the balance of several dynamic processes: speciation, competition, immigration, adaptation, and extinction. A simple kinetic model places each of these processes in a definite perspective. My arguments are based on the observation that widespread mesic environments commonly support vegetation containing greater species diversity than environments of more unusual character such as sand dunes, inundated depressions, bogs, mountain tops, saline soils, etc. Habitats such as these, that incorporate uncommon features and are often patchy and of small total area, are called peripheral habitats. Empirical and theoretical considerations both lead to the opinion that the pressure of competition in the species-rich communities of mesic ...
Aim Concern over the implications of climate change for biodiversity has led to the use of species–climate ‘envelope’ models to forecast risks of species extinctions under climate change scenarios. Recent studies have demonstrated significant variability in model projections and there remains a need to test the accuracy of models and to reduce uncertainties. Testing of models has been limited by a lack of data against which projections of future ranges can be tested. Here we provide a first test of the predictive accuracy of such models using observed species’ range shifts and climate change in two periods of the recent past. Location Britain. Methods Observed range shifts for 116 breeding bird species in Britain between 1967 and 1972 (t1) and 1987–91 (t2) are used. We project range shifts between t1 and t2 for each species based on observed climate using 16 alternative models (4 methods × 2 data parameterizations × 2 rules to transform probabilities of occurrence into presence and absence records). Results Modelling results were extremely variable, with projected range shifts varying both in magnitude and in direction from observed changes and from each other. However, using approaches that explore the central tendency (consensus) of model projections, we were able to improve agreement between projected and observed shifts significantly. Conclusions Our results provide the first empirical evidence of the value of species–climate ‘envelope’ models under climate change and demonstrate reduction in uncertainty and improvement in accuracy through selection of the most consensual projections.
Global warming impels species to track their shifting habitats or adapt to new conditions. Both processes are critically influenced by individual dispersal. In many animals, dispersal behaviour is plastic, but how organisms with plastic dispersal respond to climate change is basically unknown. Here, we report the analysis of interannual dispersal change from 16 years of monitoring a wild population of the common lizard, and a 12-year manipulation of lizards' diet intended to disentangle the direct effect of temperature rise on dispersal from its effects on resource availability. We show that juvenile dispersal has declined dramatically over the last 16 years, paralleling the rise of spring temperatures during embryogenesis. A mesoscale model of metapopulation dynamics predicts that in general dispersal inhibition will elevate the extinction risk of metapopulations exposed to contrasting effects of climate warming.