Vol. 35 – 2009 - Ecologia Mediterranea - Université d'Avignon et des ...

TALI GOLDBERG, EVIATAR NEVO, GAD DEGANI
Figure 1 – Map of various breeding sites in Israel colonized by amphibian
larvae and examined in this study. Sites - Ponds: Po1 = Manof, Po2
= Kash, Po3 = Dovev, Po4 = Matityahu, Po5 = Lehavot, Po6 = Sasa,
Po7 = Fara and Po8 = Raihaniya. Springs: Sp1 = Balad, Sp2
= Humema and Sp3 = Navoraya. Pits: Pi1 = Maalot and Pi2
= Nimrod. Stream: St1 = Tel-Dan.
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Urodela, Salamandridae); and four Anuran
species, including the tree frog, Hyla savignyi;
the green toad, Bufo viridis; the water frog,
Rana bedriagae; and the spadefoot, Pelobates
syriacus (Degani 1982; Degani 1986). Israel
offers mainly xeric habitats, unusual for
amphibians, and constitutes the southeastern
range of distribution of these species (Degani
& Mendelssohn 1983). Hence, amphibian larvae
occupy a very narrow and specific ecological
niche in the region and are under
severe pressure from predators and other
biotic and abiotic factors (Degani 1986;
Degani 1996; Degani & Mendelssohn 1983).
Amphibian larvae have been sited and studied
in a variety of ephemeral pools, ponds and
streams of hilly woodlands in northern Israel,
as well as on the coastal plain, during winter,
spring and summer. The biotic and abiotic
factors of these water bodies appear to be the
limiting factors regarding the distribution of
the larvae.
Habitats chosen by animals often reflect the
balance between conflicting demands, e.g.,
various ecological conditions. Environmental
stressors, such as temperature, water quality
and chemical conditions can also affect habitat
selection by many organisms, including
amphibians, a group very sensitive to environmental
conditions (Bancroft et al. 2008).
Generally, the selection of the habitat is
assumed to have fitness consequences, since
selecting optimal habitats will increase the fitness
of organisms (Jaenike & Holt 1991).
Environmental parameters influence habitat
use and selection by animal species (Huk &
Kuhne 1999). In the case of amphibians,
which have a complex life cycle, habitat
selection is critical to survival. The early lifehistory
stages of many amphibian species
occur in aquatic habitats of varying temporal
stability. Larvae situated in ephemeral ponds
must develop quickly and undergo metamorphosis
before the pond dries up or freezes
(Blaustein & Johnson 2003).
Little is known about the ecological
conditions suitable for larval growth and the
natural selection of aquatic habitats by the six
amphibian species located in northern Israel,
which have selected different water bodies for
breeding (Degani & Kaplan 1999). The northern
Israeli landscape is characterised by varying
altitudes, Mediterranean forest cover and
exposed areas. The influence of landscape
characteristics (primarily the forest cover and
wetland hydroperiod) on amphibian distribution
has been described and shown to have an
effect on the larval amphibian assemblage
(Herrmann et al. 2005; Mazerolle et al. 2005).
For the last 50 years, the Upper Galilee area
has been, and still is, under intensive cultivation
and urban use, and it has been proposed
that amphibian breeding sites may possibly be
affected by intensive agriculture and hydroperiods
(Beja & Alcazar 2003).
The aim of the present study was to examine
the ecological and biological conditions and
variables of different breeding sites located at
various altitudes in northern Israel, where
amphibian larvae grow and reach metamorphosis.
Such a study may increase the understanding
of the breeding site selection by
species of which the breeding period is critical
for survival.
Materials and Methods
Sites studied and larvae collected
The fourteen breeding sites of amphibian
populations in northern Israel, namely winter
pools, pits, springs and streams, were examined
over four consecutive years (2005-2008),
and their locations and descriptions are pre-
ecologia mediterranea – Vol. 35 – 2009