Ecologia Mediterranea

CATERINA MAGRINI, MICHELE CENTO, EMILIANO MANZO, MASSIMO PIERPAOLI, LIVIA ZAPPONI, ROBERTO COZZOLINO
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equilibrium were found in sampled population
(p≥0.05).
From all captured weasels, only one pair
(1,09%) from the total possible pair wise
comparisons (91) showed close genetic kinship:
the animals F2-M5 were certainly constituted
by parent/offspring (r=0.4; R=0;
p ≤0.001). For all others simulated comparisons
made by KINGROUP program, r values
(relatedness) varied from – 0.48 to 0.59, but
no significant values of R (ratio) were
detected (R≥0; p≥0.001) linked to r≥0.4.
Spatial distribution of capture localities is
shown in Figure 1. The related pair (F2-M5)
trap sites are at a distance of about 100 m.
Discussion
The average number of alleles per locus (5.3)
is in the middle part of the range of other
Mustela species, going from the lowest (1.2)
detected in black footed ferret (Mustela
nigripes) (Wisely et al. 2002) to the highest
(11.7) found in stoat (Mustela erminea)
(Fleming et al., 1999). Instead, estimated He
(0.62) is at the highest end of the range, going
from black footed ferret (0.07) (Wisely et al.,
2002) to the stoat (0.83) (Fleming et al. 1999),
and inside the range found in weasel by Pertoldi
et al. 2006 (0.6-0.73).
The analysis of genetic kinship in sampled
population revealed no full siblings, only one
parent-offspring pair and a low degree of
relatedness.
Combining these genetic results with spatial
distribution of traps we generated hypotheses
regarding pattern of dispersal.
The genetic relatedness of the pair F2-M5
represents a relation between sire and female
offspring. The distance between the capture
sites of the two animals (100 m) was inside
the range of the average home range size calculated
for the same population (Magrini et
al. 2009), moreover the absence of siblings
inside the studied population means a spacing
tactic that involves dispersal of the offspring:
these two observations are in agreement with
the hypothesis in which M5 is the father of
F2, but in disagreement with the supposition
in which F2 is the mother of M5 (which
means that M5 didn’t move away from natal
area).
The same absence of siblings between sampled
animals (in particular constituted by
males) means the absence of sex biased dispersal
for female. The other two possibilities
(both sexes dispersal or male dispersal) are in
agreement with the kinship discovered in the
sampled population.
Despite the lack of data about weasels dispersal
in previous studies, our results are yet
in agreement with data on dispersal strategy
of stoats, for which was detected a pattern of
dispersal not sex biased (Erlinge 1977; King
& McMillan 1982; Debrot & Mermod 1983).
For the evaluation of kinship results we were
not able to use data about age class of animals
because of the difficulty in estimating the age
of living weasels: actually the young reach
sexual maturity in only three months
(Sheffield & King, 1994), so from the end of
the breeding season the generations may
appear to overlap, and despite kits, it is impossible
to determine an age class with any confidence
(King 2007). Another problem is the
lack of data about females (only three were
captured during the study), that didn’t permit
to clarify prospective sex biased dispersal.
Weasels were described as an r-selected
species (Sandell 1984; Stenseth 1985) with
short life span, high natural mortality in the
first year (75%-90%) (King 1980, 2007;
Sheffield & King 1994; McDonald & Harris
1998) but also rapid production of young and
high population turn-over: so natural populations
suffer great numerical fluctuations that
involve local extinctions and recolonizations
in which a different set of resident animals is
observed every year (King 1983, 1989, 2007).
Even if these ecological and biological traits
seem to converge in an opportunistic philopatry
strategy (Waser & Jones 1983), data from
this study disprove this hypothesis: the lack
of sibling kinship in the sampled population
can suggest the presence of dispersal strategy,
probably promoted by survival of resident
animals in the second life year.
Also Pertoldi et al. (2006) found a high
genetic variance in wild weasel population,
that does not agree with an high population
turnover and density fluctuations (Caballero
1994).
Genetic structure is strongly influenced by
patterns of individual movement and reproduction
as stressed by Cutrera et al. (2005):
molecular studies seem the most useful way
to investigate these patterns in very elusive
small carnivore species.
ecologia mediterranea – Vol. 38 (2) – 2012