Abstract
The phylogenetic relationships and the geographical origin of 27 of the 34 species and of 3 of the 9 subspecies of Iberian endemic Dytiscidae are studied, based on species level phylogenies constructed with two mitochondrial gene fragments (16S rRNA and Cytochrome Oxidase I). All Iberian endemic species for which more than one specimen was included were monophyletic with the exception of the complex Deronectes aubei sanfilippoi Fery & Brancucci, 1997-D. delarouzei (Jac. Du Val, 1857). The genus Stictotarsus as presently defined is polyphyletic, containing three different lineages: the S. duodecimpustulatus group —including the Iberian endemic S. bertrandi (Legros, 1956)—, Trichonectes otini (Guignot, 1941) (new combination) and the S. griseostriatus and S. roffii groups, which are in need of a new generic name. The genus Oreodytes is found to be paraphyletic, although with low bootstrap support. The species Nebrioporus (Nebrioporus) martinii (Fairmaire, 1858) (new combination) is transferred from the subgenus Zimmermannius to Nebrioporus. The Iberian populations of Stictotarsus griseostriatus (De Geer, 1774) and the endemic subspecies Oreodytes davisii rhianae Carr, 2001, O. sanmarkii alienus (Sharp, 1872) and Hydroporus normandi normandi Regimbart, 1903 do not form well characterised lineages, as measured with the mitochondrial markers used in this study. The Iberian endemic species of Dytiscidae are divided in three groups according to the type of vicariant origin: 1) within-Iberian species, when the sister species (or clade) of the Iberian endemic is also and Iberian endemic; 2) Iberian/European, when the sister occurs in Europe north of the Pyrenees; and 3) Iberian/North African, when the sister occurs in North Africa. Within-Iberian endemics are found to be on average older than Iberian/European and Iberian/North African species, they have more restricted distributions within the Iberian peninsula (they occur typically in only one of the main biogeographical regions), and tend to occur exclusively in running waters. The withinIberian species are best represented by the “Iberian” clade of the genus Deronectes, formed by six endemic species plus two species with wider distributions. Most species in this group originated in rapid succession in the Late Miocene-Early Pliocene boundary by repeated vicariant events in the three main mountain massifs in the Iberian peninsula: the Pyrenees, the Baetic ranges, and the Sistema Central plus mountain massifs of the NW. On the contrary, most of the Iberian/European species seem to be the recent (Pleistocene) vicariants of a species with a widespread distribution encompassing the Iberian peninsula, at present restricted to south and west of the Ebro valley. The results of these analyses suggest that the Iberian peninsula was an isolated refuge during the Quaternary glaciations, in where allopatric speciation was frequent among some lineages of Dytiscidae diving beetles.
Highlights
Most of the Iberian/European species seem to be the recent (Pleistocene) vicariants of a species with a widespread distribution encompassing the Iberian peninsula, at present restricted to south and west of the Ebro valley. The results of these analyses suggest that the Iberian peninsula was an isolated refuge during the Quaternary glaciations, in where allopatric speciation was frequent among some lineages of Dytiscidae diving beetles
TAXON SAMPLING There are at present 33 recognised species and nine subspecies of endemic Dytiscidae in the Iberian peninsula, including eight which occur in some areas in south France, on the north side of the Pyrenees (Ribera, 2000; Millán et al, 2002, Table 1)
The two topologies (Iberoporus sister to Rhithrodytes or to Metaporus plus Graptodytes) are not significantly different, as measured with the non-parametric Templeton (1983) Wilcoxon signed-ranks statistic (p = 0.78), or the Shimodaira & Hasegawa (1999) test using RELL with 10,000 bootstrap replicates (p= 0.13), using the maximum likelihood (ML) model implemented for the calibration of the branch lengths
Summary
The Mediterranean basin, and within it the Iberian peninsula, are among the world’s most diverse areas (Mittermeier et al, 1998; Blondel & Aronson, 1999; Médail & Quézel, 1999; Myers et al, 2000), with up to 20% of endemic taxa in several groups of plants and animals in mountain areas of Spain and Portugal (Baletto & Casale, 1991; Greuter, 1991; Domínguez Lozano et al, 1996; Blanca et al, 1998; Blondel & Aronson, 1999). Doadrio, 1988; Dennis et al, 1998; Puente et al, 1998; Vargas et al, 1998; Ribera, 2000; García-. 2002) and in establishing the origin of selected Iberian taxa and their phylogenetic and phylogeographic relationships, mainly with molecular methods There is, a paucity of studies bringing together these two approaches, that is, searching for general patterns in the origin and the phylogenetic and phylogeographic relationships in relatively rich groups of organisms with Iberian representation Areas: geographic distribution within Iberia (see Fig. 7a): 1, Pyrenean; 2, Cantabrian; 3, Hercinian; 4, Baetic; 5, S West. a, Present in the north side of the Pyrenees
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