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Animal Biodiversity and Conservation 39.2 (2016) 165

Table 1. Context and scenario in evaluating hypothetical dispersal fluxes to the volcanic islands:
*Â Continental islands.

Tabla 1. Contexto y supuestos utilizados en la evaluación de los hipotéticos flujos de dispersión hacia
las islas volcánicas: * Islas continentales.

Context Scenario Target islands Possible source areas

North of Sicily 1 Lipari, Salina, Vulcano, Stromboli, Sicily, Calabria, Lipari, Salina,
Vulcano, Stromboli, Filicudi, Alicudi,
Filicudi, Alicudi, Panarea, Ustica Panarea, Ustica

As above + Egadi islands
(Favignana*, Levanzo*, Marettimo*)
North of Sicily 2 Lipari, Salina, Vulcano, Stromboli,
Filicudi, Alicudi, Panarea, Ustica Sicily, Tunisia, Pantelleria, Linosa

South of Sicily 1 Pantelleria, Linosa As above + Egadi Islands
(Favignana*, Levanzo*, Marettimo*),
South of Sicily 2 Pantelleria, Linosa Malta*, Lampedusa*

patterns in the north of Sicily are equivalent in both which was colonized from Salina). The flow linking
scenarios with both Lipari and Vulcano acting as Ustica to Lipari suggests that the former was most
major source areas (three fluxes each) followed by likely colonized from the latter, noteworthy results
Sicily (two fluxes) and Salina (one flux) (tables 2, 3; since these islands are 150Â km apart and Ustica is
figs. 2, 3). Both scenarios show two equivalent fluxes just 54 km away from Sicily. A chromosomal study
towards Alicudi (Lipari and Vulcano). (Colomba et al., 1995) about Thorectes intermedius
populations of the mainland Sicily, Marettimo (Egadi
Results in the Sicily Channel (south of Sicily) differ Islands), Caprera (Sardinia) and Ustica revealed, as
depending on the scenario. In the first scenario, Tuni� one would expect, that the populations of Ustica seem
sia acts as a major source area (two fluxes), followed to be related to those of mainland Sicily. However,
by Sicily (one flux). Linosa has two equivalent fluxes this study did not take into account the population of
starting from Tunisia and Sicily, while the flux into intervening areas, such as the Aeolian archipelago,
Pantelleria indicates that it was probably colonized by as we did. The same is true for Alicudi, Filicudi, and
Tunisian fauna. In the second scenario, Malta acts as Stromboli, all of which would have been colonized
a major source area (two fluxes) followed by Tunisia from Vulcano and Lipari, again acting as core source
(one flux). Pantelleria shows two equivalent fluxes areas, as opposed to being targeted from their nearest
starting from Malta and Tunisia. Linosa was colonized neighbour in a stepping–stone fashion.
by Maltese fauna (one flux).
Although the cluster analysis used by Fattorini
Discussion (2010) to examine the similarity of island assemblages
does not allow to determine the direction of disper�
This study focused on the hypothetical dispersal sal, our results are in agreement with some of those
routes of dung beetles in the circum–Sicilian volca� established by this author: Salina and Panarea are
nic islands. The survey was conducted applying the grouped together (see figure 3 in Fattorini, 2010), and
DD2 coefficient of dispersal direction (Legendre & in our work Salina is the source for Panarea. In the
Legendre, 1984), a method that highlights the most alternative solution of Kulczynski 2 (Fattorini, 2010:
probable routes of colonization considering the entire 1066), Salina was grouped with Lipari and Vulcano,
assemblages of each area. and Lipari appears as the source of dung beetles
for Salina. In Fattorini’s Jaccard results, Alicudi is
It is interesting to note that the distribution of related to the Vulcano and Lipari group, and our re�
dung beetles on the circum–Sicilian volcanic islands sults confirm this pattern with Alicudi displaying two
could be the result of a coherent dispersal process equivalent fluxes departing from Lipari and Vulcano.
rather than due to chance. This is corroborated by In the Sicily Channel, Linosa has three equivalent
the fact that all DD2 major fluxes had a significant fluxes, two in the first scenario and one in the sec�
value according to the McNemar test. In the north ond, with three possible source areas (Malta, Sicily,
of Sicily, the dispersal fluxes led towards Vulcano and Tunisia). Pantelleria has two equivalent fluxes
and Lipari. These two islands thus acted as core (Tunisia in the first and second scenarios, and Malta
source areas for the other islands (except Panarea, in the second). Linosa is centrally located in the Sicily