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