Annual temperature data for two Malagasy sites of high anuran diversity

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A Conservation Strategy for the
Amphibians of Madagascar
Monografie del Museo Regionale di Scienze Naturali
di Torino, XLV (2008): pp. 85-94
1
Technical University of Braunschweig.
2
University of California, Berkeley.
Katharina C. WOLLENBERG
1
, David R. VIEITES
2
, Miguel VENCES
1
Annual temperature data for two Malagasy sites
of high anuran diversity
ABSTRACT
We present microclimatic temperature data for two Malagasy rainforest sites with high
amphibian diversity. Our data show that daily, monthly and annual temperature ranges in these
microhabitats are relatively narrow and, as expected, temperatures are much more buffered in
streams than in the leaf litter. A successful ex-situ conservation of many species may require
adaptation to the reported thermal conditions. Because many Madagascan amphibians seem to be
restricted to certain elevations and hence climatic conditions, global warming could endanger
stenothermic amphibian species adapted to these narrow climatic envelopes, which highlights the
need for more detailed monitoring, and for an assessment of temperature tolerances and
preferences.
Key words: amphibians, ex-situ conservation, Madagascar, temperature variation, ecology.
INTRODUCTION
Species' fundamental ecological niches are determined by both biological
and physical environmental conditions. Among those conditions, microclimatic
data are critical to understand species activity rhythms and annual phenology,
especially in ectothermic vertebrates like amphibians. Large-scale global
warming has already been related to amphibian declines in Neotropical areas
(Pounds et al., 2006). If this turns out to be a global phenomenon,
microclimatic data and long-term comparative studies on amphibian declines in
other tropical areas of the world are urgently needed. Although temperature and
rainfall data are available from the global network of meteorological stations
and can be interpolated to develop climate surfaces (Hijmans et al., 2005),
those data usually do not reflect actual microclimatic conditions for most
amphibian habitats.
wollenberg:•5-12 Pessani 31-10-2008 14:47 Pagina 85
Despite the recent technological advances in field temperature recordings
(i.e. miniaturized data loggers), few studies report their use in this group of
vertebrates, being normally employed for a short period of time (Kusano et al.,
2006). Long-term data-logging of temperature in local amphibian microhabitats
will not only provide the dynamics and range of microclimatic conditions
where species live, but can also be of great interest in developing protocols for
captive breeding of endangered species.
For Madagascar, temperature data are available from many meteorological
stations, and data on general Madagascan climate zones have been published
(e.g., Donque, 1975), yet to our knowledge no data exists about annual
temperatures in microhabitats relevant for anurans, such as leaf litter or small
streams. Therefore, annual temperature curves from leaf litter and streams in
Madagascar can be helpful to fill in these gaps, and provide preliminary data on
these microhabitats critical for both adult and larval stages of amphibians.
Current studies suggest that highest values of amphibian diversity in
Madagascar are concentrated in the primary rainforests of the central-east and
south-east (Lees et al., 1999; Andreone et al., 2005; own, unpublished data).
Microclimatic data for the above mentioned localities are especially interesting
in the context of ex situ conservation because they are applicable to captive
breeding of multiple species, especially those that live mainly on the forest
floor or in streams. Here we present data about microhabitat temperatures
gathered during 2006-2007 at two sites of high amphibian species diversity in
Madagascar: Andasibe and Ranomafana.
METHODS
In total, five data loggers (ibutton DS1921G-F5, Dallas Technologies) were
set for one year (2006-2007) in Andasibe and Ranomafana. These data loggers
can record temperature data from -40°C to 85°C at 0.5°C precision, and can
record data in different time periods. We set them up to record data every 4
hours, providing three measurements during the night and three during the day.
In Andasibe, one data logger was placed in the vicinities of the “Station
forestiére” in the leaf litter on a slope, about 200 m from the nearest stream. In
Ranomafana, we placed each two data loggers at two localities, Sahamalaotra
and Talatakely. Both these sites are located in Ranomafana National Park. At
each site, one data logger was set in the water of a permanent stream and the
second one in the leaf litter (2-5 cm underground) near the stream (Tab. I). All
loggers were placed in primary rainforest under a closed canopy. At all three
sites, diverse amphibian communities occur, which mostly comprise stream-
breeding species of Boophis and Mantidactylus, but also various leaf-litter
dwelling cophyline microhylids (Stumpffia and Plethodontohyla) and
mantellids (Gephyromantis, Glaw & Vences, 2007). In general, from both the
Ranomafana and Andasibe areas, high amphibian diversities of about 100
species occurring within a few square kilometers have been recorded.
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Tab. I. Locality information, data acquisition time and coordinates of the sampled sites.
RESULTS AND DISCUSSION
Our data show the typical temperature patterns for a tropical climate, with
relatively small temperature ranges and only two seasons during the year. In
figures 1, 2 and 3, a temperature curves typical for Malagasy rainforests can be
observed; mean annual temperatures in the leaf litter range between 15.8°C
(Sahamalaotra leaf litter) and 17.2°C (Andasibe leaf litter). Mean annual
temperatures in the two sampled streams were 16.0°C and 16.9°C (Tab. II). In
the dry season from April to September, temperatures are lower than their
annual mean in all sampled localities, and in the rainy season (October to
March) the mean temperatures increase (see Tab. II).
Comparison of the annual temperatures in water and leaf litter shows that
temperatures in the streams are generally more constant than leaf litter
temperatures. In Sahamalaotra, the annual leaf litter temperatures shift between
+2.0°C (rainy season) and -1.9°C (dry season) compared to annual means; the
water temperature shifts only between +1.0°C (rainy season) and -1.0°C (dry
season). In Talatakely, the annual leaf litter temperature shifts between +1.3°C
(rainy season) and -1.3°C (dry season) compared to annual mean; the water
temperature shifts only between +0.7°C (rainy season) and -0.6°C (dry season).
For Andasibe, no data for stream temperatures could be obtained. However,
leaf litter temperatures in Andasibe were the highest among the three sampled
localities. Information on temperature fluctuations between daytime and night
can be seen in Tab. III (and are visualized in Fig. 4). Characteristically, the
mean temperature shifts between daytime and night are small (≤0.2°C) in rainy
and dry season, respectively. Also, temperature differences between rainy and
dry season are generally smaller in streams than in the leaf litter at daytime and
at night.
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Fig. 1. Annual temperature curves for stream and leaf litter data in Sahamalaotra. Leaf litter
temperature is indicated by a continuous line, stream temperatures are indicated by a broken line.
Line fit: Distance weighted least-squares.
Fig. 2. Annual temperature curves for stream and leaf litter data in Talatakely. Leaf litter
temperature is indicated by a continuous line, stream temperatures are indicated by a broken line.
Line fit: Distance weighted least-squares.
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Fig. 4. Mean temperatures at day and night time, and their minimal and maximal values. Values are
shown for dry and rainy season separately. A = Andasibe, T = Talatakely, S = Sahamalaotra, st =
stream, ll = leaf litter, r = rainy season, d = dry season.
89
Fig. 3. Annual temperature curves for temperature data for the leaf litter in Andasibe. Line fit:
Distance weighted least-squares.
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90
Tab. II. Summary statistics of the obtained temperature data for all sites. The arithmetic mean,
standard deviation, minimal and maximal values are given for (a) the whole sampling period, (b)
the dry season (04/01/2006 - 10/01/2006) and (c) the rainy season (10/02/2006 - begin of sampling
in February / March, see Tab. I).
Whole period Dry season T [°C] Rainy season
Sahamalaotra leaf litter
7.71 naem 9.31 naem 8.51 naem
9.1 ds 0.2 ds 8.2 ds
0.72 xam 0.91 xam 0.72 xam
5.9 nim 0.9 nim 0.9 ni
m
Sahamalaotra stream
0.71 naem 0.51 naem 0.61 naem
0.1 ds 2.1 ds 5.1 ds
0.91 xam 0.81 xam 0.91 xam
5.31 nim 5.21 nim 5.
21 nim
Talatakely leaf litter
3.81 naem 7.51 naem 0.71 naem
4.1 ds 6.1 ds 0.2 ds
5.02 xam 5.91 xam 5.02 xam
5.21 nim 5.21 n
im 5.21 nim
Talatakely stream
6.71 naem 3.61 naem 9.61 naem
7.0 ds 1.1 ds 2.1 ds
0.91 xam 5.81 xam 0.91 xam
5.51 nim
5.41 nim 5.41 nim
Andasibe leaf litter
6.81 naem 61 naem 2.71 naem
9.1 ds 9.1 ds 3.2 ds
5.22 xam 5.02 xam 5.22 xam
0.11
nim 5.11 nim 0.11 nim
T [°C] T [°C]
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91
Our data indicate that natural microclimatic conditions for a large number
of Malagasy frog species involve relatively low minimum temperatures around
9-11°C (Tab. III), and that temperature changes are much more buffered in
streams. Adjusting tank temperatures as well as water temperatures (for tadpole
rearing) to the observed conditions may at least in some cases be a premise for
successful captive breeding (e.g., in the context of ex-situ conservation) of
these frogs. Furthermore, our data suggest that the temperature range in the
sampled microhabitats is relatively narrow, both on a daily, monthly and annual
scale. This may be relevant to the potential decline of amphibian species under
future global warming scenarios, as these narrow climatic envelopes could be
largely affected by a global increase in temperature (Williams et al., 2007).
Climate change has naturally occurred over millions of years, and most
Malagasy species of amphibians have a strong genetic differentiation and hence
an old age (Köhler et al., 2005), and therefore must have survived past climate
shifts. However, under the present conditions of largely fragmented and
destroyed forests in Madagascar, species may not always be able to adequately
respond to such shifts by moving into habitats at different elevations.
Therefore, long-term monitoring efforts should also include measurements of
other environmental parameters like humidity or temperatures at various
heights above the ground which are relevant to anurans, to understand possible
changes in these parameters.
T [°C]
Sahamalaotra stream
9.41 yad naem 9.61 yad naem
mean day r/d 2.0
2.1 yad ds 0.1 yad ds
sd day r/d 0.2
0.81 yad xam 0.91 yad xam
max day r/d 1.0
5.21 yad nim 5.31 yad nim
min day r/d 1.0
mean night 17.0 mean night 15.1
mean night r/d 2.0
2.1 thgin ds 0.1 thgin ds
sd night r/d 0.2
0.81 thgin xam 5.81 thgin xam
max night r/d 0.5
5.21 thgin nim 5.31 thgin nim
min night r/d 1.0
mean day/night 0.1 mean day/night 0.1
sd day/night 0.0 sd day/night 0.0
max day/night 0.5 max day/night 0.0
min day/night 0.0 min day/night 0.0
Sahamalaotra leaf litter
9.31 yad naem 8.71 yad naem mean day r/d 3.9
1.2 yad ds 9.1 yad ds
sd day r/d 0.2
0.91 yad xam 0.72 yad xam
max day r/d 8.0
0.9 yad nim 5.9 yad nim
min day r/d 0.5
mean night 17.6 mean night 13.8
mean night r/d 3.8
0.2 thgin ds 9.1 thgin ds
sd night r/d 0.2
0.91 thgin xam 5.32 thgin xam
max night r/d 4.5
5.9 thgin nim 0.01 thgin nim
min night r/d 0.5
Rainy season
T [°C]
T [°C]
Dry season
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92
mean day/night 0.2 mean day/night 0.1
sd day/night 0.0 sd day/night 0.1
max day/night 3.5 max day/night 0.0
min day/night 0.5 min day/night 0.5
Talatakely stream
0.61 yad naem 5.71 yad naem mean day r/d 1.3
1.1 yad ds 7.0 yad ds
sd day r/d 0.4
5.81 yad xam 0.12 yad xam
max day r/d 2.5
5.41 yad nim 5.51 yad nim
min day r/d 1.0
mean night 17.6 mean night 16.3
mean night r/d 1.3
1.1 thgin ds 7.0 thgin ds
sd night r/d 0.4
5.81 thgin xam 5.02 thgin xam
max night r/d 2.0
0.51 thgin nim 5.51 thgin nim
min night r/d 0.5
mean day/night 0.1 mean day/night 0.1
sd day/night 0.0 sd day/night 0.0
max day/night 0.5 max day/night 0.0
min day/night 0.0 min day/night 0.5
Talatakely leaf litter
7.51 yad naem 3.81 yad naem mean day r/d 2.6
6.1 yad ds 4.1 yad ds
sd day r/d 0.2
5.91 yad xam 5.02 yad xam
max day r/d 1.0
5.21 yad nim 5.21 yad nim
min day r/d 0.0
mean night 18.3 mean night 15.8
mean night r/d 2.5
6.1 thgin ds 4.1 thgin ds
sd night r/d 0.2
5.91 thgin xam 5.02 thgin xam
max night r/d 1.0
0.31 thgin nim 0.31 thgin nim
min night r/d 0.0
mean day/night 0.0 mean day/night 0.0
sd day/night 0.0 sd day/night 0.0
max day/night 0.0 max day/night 0.0
min day/night 0.5 min day/night 0.5
Andasibe leaf litter
9.51 yad naem 8.81 yad naem mean day r/d 2.9
9.1 yad ds 9.1 yad ds
sd day r/d 0.0
5.02 yad xam 5.22 yad xam
max day r/d 1.5
5.11 yad nim 0.11 yad nim
min day r/d 0.5
mean night 18.6 mean night 16
mean night r/d 2.6
9.1 thgin ds 9.1 thgin ds
sd night r/d 0.0
5.02 thgin xam 5.12 thgin xam
max night r/d 1.0
5.11 thgin nim 5.11 thgin nim
min night r/d
mean day/night 0.2 mean day/night 0.1
sd day/night 0.1 sd day/night 0.0
max day/night 0.5 max day/night 0.0
min day/night 0.5 min day/night 0.0
Tab. III. - Daily temperature ranges and the absolute differences between day/night and rainy/dry
season values (in °C, indicated by Δ). See Figure 4.
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93
ACKNOWLEDGEMENTS
We are grateful to Emile Rajeriarison, Teo Rajaofiarison, Rainer Dolch and Ylenia Chiari for
setting and retrieving the dataloggers, to Helmut Kurrer for discussions about captive breeding of
Malagasy frogs, to the Département de Biologie Animale, Université d’Antananarivo, for help and
partnership, and to the Malagasy authorities for issuing research permits. DRV is currently funded
by the NSF ATOL Grant EF-0334939.
RÉSUMÉ
Température annuelle pour deux sites malgaches sur une grande diversité d’anuran.
Nous présentons des données de températures microclimatiques de deux sites malgaches de
forêts pluvieuses avec une grande diversité d’amphibiens. Nos données montrent que les gammes
de températures, quotidiennes, mensuelles et annuelles dans ces micro habitats sont relativement
proches, et comme on pouvait l’attendre, les variations de température sont bien plus marquées
dans les rivières que entre les litières de feuilles. Une conservation ex-situ réussie pour de
nombreuses espèces nécessite une adaptation à ces conditions thermiques rapportées. En effet,
beaucoup d’amphibiens malgaches semblent être limités par certaines altitudes et donc par les
conditions climatiques. Le réchauffement global pourrait mettre en danger les espèces
d’amphibiens sténo thermiques adaptés dans ces étroites enveloppes climatiques, ce qui souligne le
besoin de plus de détails de suivi.
Mots clés: Amphibiens, Conservation, Écologie, Madagascar, variation de température.
Katharina W
OLLENBERG
Miguel VENCES
Zoological Institute
Technical University of Braunschweig
Spielmannstr. 8
38106 Braunschweig, Germany
Email m.vences@tu-bs.de
David R. VIEITES
Museum of Vertebrate Zoology and Department of Integrative Biology
3101 Valley Life Sciences Bldg.
University of California
Berkeley, CA 94720-3160. USA
Email vieites@berkeley.edu.
wollenberg:•5-12 Pessani 31-10-2008 14:47 Pagina 93
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