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

TALI GOLDBERG, EVIATAR NEVO, GAD DEGANI
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T. vittatus larvae are carnivores (Kutrup et al.
2005) and prey on the same foodstuff as do
S. infraimmaculata larvae (Degani &
Mendelssohn 1978; Degani & Mendelssohn
1982). However, the T. vittatus larvae are
observed during different time periods and in
water of a different temperature, as was found
in the present, and in previous investigations
(Degani 1982; Degani 1986). R. bedriagae,
H. savignyi and B. viridis larvae are herbivores
that consume mainly algae of various
kinds (Seale & Beckvar 1980). Since they are
not present at the same time in the breeding
sites, the interaction among them is very low.
B. viridis larvae are found in the winter and
at the beginning of spring; H. savignyi larvae
are observed in the spring and R. bedriagae
during the summer. On the other hand, P. syriacus
grow and go through metamorphosis at
the same time as the three species, H. savignyi,
B. viridis and T. vittatus larvae. Degani
(1986) has proposed that P. syriacus exists in
a microhabitat differing from that of the other
species.
In the present investigation, some species,
e.g., S. infraimmaculata, were found in breeding
sites possessing different water conditions.
Such a difference among various larvae
is documented for other species. Ambystomids
are known as opportunistic breeders and
exploit a number of different permanent and
temporary aquatic habitats, which include disturbed
and human-affected areas (Braun
2006; Pilliod & Fronzuto 2005), which help
explain their presence in the artificial watering
tanks on the National Bison Range. Egea-
Serrano et al. (2006; 2006) reported that S.
infraimmaculata has a macrohabitat scale that
includes aquatic habitats located in mountainous
topography and at altitudes higher
than 1250 m.a.s.l. In this study, the breeding
sites of S. infraimmaculata were located 150-
1000 m.a.s.l, according to ecological conditions
and not altitudes. Still, some findings are
not fully understood and need further studying.
For example, it is not clear whether the
adult amphibians living in northern Israel
select the breeding sites and breed only where
suitable for larval growth and metamorphosis
completion, or breed randomly where water
is available.
The invertebrate biomass results in the present
study are in agreement with those of previous
studies (Degani 1986; Degani &
Mendelssohn 1978; Degani & Mendelssohn
1982), i.e., fewer invertebrates are present in
the more permanent water bodies (streams
and springs), as compared to in the winter
ponds. These results explain the large larval
community in the winter ponds, especially
during the spring and at the beginning of summer.
With regard to habitat types, these different
water bodies have different environmental
conditions and exhibit habitat niche widths
that vary in size (Figure 5). This implies that
the ability of larvae to cope with these different
habitats may reflect local adaptation of the
larvae to these water parameters. The variations
in temperature, oxygen and conductivity
seem to be very important. However, other
investigators of amphibians have chosen to
study other parameters (Holenweg-Peter et al.
2002; Pagano et al. 2001; Pagano et al. 2008;
Voituron et al. 2005). In the present study, the
range of environmental parameters and the
interactions between these parameters and
various species belonging to six different genera,
as shown in figure 5, demonstrate that R.
bedriagae has a wider niche size than all other
larvae. This is due to the long period (from
summer to winter) that the larvae are present
in the water and the relatively small niches
occupied by T. vittatus, P. syriacus and B.
virdis. The time during which B. virdis was
observed in the pond was relatively short
(Degani 1982; Degani 1986), while the distribution
of this species in Israel is very high
(Degani & Kaplan 1999).
To summarise this investigation, the major
factors affecting habitat selection for breeding
are the ecological conditions suitable for
survival, growth and completion of metamorphosis
of the various amphibian larvae. Furthermore,
the major factor affecting habitat
selection and larval growth is the temperature.
ecologia mediterranea – Vol. 35 – 2009