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Eur. J. Entomol. 108: 659–672, 2011
http://www.eje.cz/scripts/viewabstract.php?abstract=1665

ISSN 1210-5759 (print), 1802-8829 (online)

Biogeography of tenebrionid beetles (Coleoptera: Tenebrionidae)
in the circum-Sicilian islands (Italy, Sicily): Multiple biogeographical

patterns require multiple explanations

SIMONE FATTORINI

WET – Water Ecology Team, Department of Biotechnology and Biosciences, University of Milano Bicocca, Piazza della Scienza 2,
20126 Milano, Italy; e-mail: simone_fattorini@virgilio.it

Azorean Biodiversity Group, Departamento de Ciências Agrárias, Universidade dos Açores, Pico da Urze,
9700-042 Angra do Heroísmo, Portugal

Key words. Biogeography, Coleoptera, Tenebrionidae, Mediterranean, Pleistocene, Sicily, species-area relationship

Abstract. The tenebrionid beetles on 25 circum-Sicilian islands were studied to determine the influence of island geographical and
landscape features on three main intercorrelated biogeographical patterns: (1) species richness, studied using species-area and spe-
cies environment relationships, (2) species assemblage composition, investigated using Canonical Correspondence Analysis (CCA),
and (3) inter-site faunal similarity, investigated using Canonical Correlation Analysis (CANCOR) applied to multidimensional
scaling of inter-island faunal dissimilarities. Species richness was mostly influenced by island area and landscape heterogeneity
(expressed using various indices of diversity based on land cover categories). When species identities were considered in the CCA,
no substantial effect of landscape was detected. Current island isolation did not have a strong influence on species richness, but has a
distinct effect in determining species assortments on the remotest islands. Historical influences of Pleistocene landbridge connections
were not detectable in species richness relationships using geographical variables in species richness analyses or in assemblage gra-
dients in the CCA, but emerged distinctly from inter-island similarities in the CANCOR.

INTRODUCTION sions summarizing the biogeographical positions of
islands in multidimensional space (e.g. dimensions from
Recently there have been advances in Mediterranean Multidimensional Scaling) and values of geographical/
island biogeography in terms of the influence of geo- environmental variables (see Fattorini, 2006a).
graphical and ecological (environmental) factors on spe-
cies richness (Foufopoulos & Ives, 1999; Fattorini, Finally, there are few studies on how geographical and
2002b, 2006b, 2007, 2009b, c; Hausdorf & Hennig, 2005; environmental factors may explain species composition
Dapporto & Dennis, 2008a, b), species composition on islands and the use of Canonical Correspondence
(Dennis et al., 2008; Dapporto & Dennis, 2009; Fattorini, Analysis (CCA) to correlate species distributions with
2011) and inter-island faunal similarities (Dennis et al., island characteristics was only recently proposed (Fatto-
2000; Fattorini, 2002a, 2006a, 2009a, 2010; Hausdorf & rini, 2011). No study, however, has integrated these dif-
Hennig, 2005; Dapporto & Cini, 2007; Dapporto et al., ferent approaches by simultaneously investigating these
2007). three aspects of variation on community structure.

There is a large body of literature on the relationships In this paper, these three aspects of the fauna of tenebri-
between species richness and geographical and ecological onid beetles (Coleoptera: Tenebrionidae) on the islands
factors, such as area, isolation, age and environmental surrounding Sicily, the largest Mediterranean island, were
diversity in the most disparate kinds of archipelagos investigated simultaneously. Sicily is surrounded by a
(Whittaker et al., 2008). These studies typically use corre- number of small islands, collectively known as the
lation analyses, multiple regressions, structural equations “circum-Sicilian” islands. Some of them form small
or similar techniques to relate species number to the vari- archipelagos, while others are isolated, and their distance
ables of interest (Fattorini, 2002a, b, 2006a, 2007, 2009a, c; from Sicily varies considerably. The biogeography of the
Hausdorf & Hennig, 2005; Dapporto et al., 2007; Dap- circum-Sicilian islands is particularly complex (e.g. Corti,
porto & Cini, 2007; Dapporto & Dennis, 2008a). 1973; Capula, 1994; Corti et al., 1998; Harris et al.,
2009), because the islands vary greatly in terms of their
The importance of geographical and ecological factors geological origin (volcanic vs. sedimentary), paleogeog-
in explaining inter-island faunal similarities has received raphy (some were connected to Sicily or Africa during
less attention. Studies in this field typically correlate Pleistocene glaciations, others remained isolated), dis-
(using Mantel tests) matrices of biogeographical distances tance to the main source of colonization (Sicily or
with matrices of geographical/environmental distances Africa), area (Malta, the largest island, has an area of
(see, for example, Hausdorf & Hennig, 2005; Dapporto & 245.7 km2, but most of the islands are smaller than 30
Cini, 2007; Fattorini, 2009a, c, 2010) or use a Canonical km2) and environmental conditions. Moreover, their loca-
Correlation Analysis (CANCOR) of a number of dimen-

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