Dichromacalles, STUBEN, 1998

Stüben, Peter E. & Astrin, Jonas J., 2010, Molecular phylogeny in endemic weevils: revision of the genera of Macaronesian Cryptorhynchinae (Coleoptera: Curculionidae), Zoological Journal of the Linnean Society 160 (1), pp. 40-87 : 71-72

DICHROMACALLES STÜBEN, 1998 ( FIG. 22A–E )

Type species: Rhynchaenus diocletianus Germar, 1817 – Croatia (including type locality), south-west Europe, north-west Africa

Boheman, 1844; Brisout et al., 1864; Solari & Solari, 1907; Hoffmann, 1958; Stüben & Behne, 1998; Bayer & Stüben, 2000; Riede & Stüben, 2000; Sprick & Stüben, 2000; Stüben, 2000b, c, d, 2002b, 2004b, 2005b, 2007b, 2008a; Bahr, 2001; Stüben et al., 2001; Stüben & Germann, 2005; Astrin & Stüben, 2008.

Compilation of the species of the genus

Dichromacalles of the Macaronesian Islands

Dichromacalles dromedarius ( Boheman, 1844) (formerly: Acalles ) – Canary Islands, Madeira, Azores, Portugal (including type locality), southwest Europe, north-west Africa

= Acalles fasciculatus Boheman (1844) syn. Bahr (2001: 126).

= Acalles plagiatofasciatus Costa, 1847 syn. Bahr (2001: 126).

= Acalles impressicollis Lucas, 1849 syn. Bahr (2001: 126).

Discussion: The widespread Dichromacalles diocletianus presumably lives on all Canary Islands in an altitude between 50 and 2000 m (until now not reported from Fuerteventura). Individuals of this species have often been found in great abundance on plants of the daisy family ( Asteraceae : Sonchus sp. , Tolpis sp. , Andryala pinnatifida Ait. , Picris echioides L., etc.), on umbelliferous plants ( Apiaceae , e.g. Foeniculum sp. ) and sporadically also on plants of the orpine family ( Crassulaceae ) (P. E. Stüben, pers. observ.). Hence Dichromacalles diocletianus is markedly polyphagous and on its host plants it is socialized with several other species of Cryptorhynchinae .

In the year 1971, the first Canarian D. dromedarius specimens were reported for Tenerife. According to the current omnipresence of this species on the Canary Islands, Madeira, and the Azores, we exclude the possibility that this species – not found during the extensive collecting of T. V. Wollaston in the mid-19 th century – could have simply been overlooked before (cf. also minimal genetic distance – in Fig. 1A – separating a European and a Canarian specimen). Hence it is undoubtedly an adventitious species that was introduced for instance with plants of the daisy family [ Tempère & Péricart (1989) mention the cotton thistle ( Onopordon illyricum L.) as host plant in south-western Europe; we also found D. dromedarius on several ligneous perennials in the coastal belts of Morocco, southern Spain, and Portugal]. Spreading very rapidly, D. diocletianus is the only recent settler from the mainland on the Macaronesian Islands. On Madeira, it lives (amongst others) on Tolpis succulenta ( Fig. 22C ) and thus it has become a serious competitor of the endemic Madeiracalles pulverosus and Madeiracalles tolpis ( Stüben, 2002b: 147) .

Distribution: Presumably present on all Canary Islands (hitherto no report only for Fuerteventura); also on Madeira and the Azores (although not reported from all of the islands within these archipelagos). See also the ‘Key to the genera and subgenera of Macaronesian Cryptorhynchinae’.

Figures

Figure 1. A, Bayesian 50% majority rule consensus for the two analysed mitochondrial genes. Numbers indicate nodal posterior probabilities. The scale shows the expected nucleotide substitutions per site. Abbreviations in parentheses denote subgenus (see text). Genus names in bold indicate new nomenclature. Circles mark colonization events (in black: invasive species). For many Macaronesian species, the respective host plants are depicted. The second page of the tree shows the taxa corresponding to the ‘Atlantic clade’. B, chronogram based on relaxed phylogenetic analysis of the two mitochondrial genes, using the uncorrelated lognormal model of substitution rate variation. Numbers next to the nodes indicate mean divergence times (in Myr), with 95% confidence intervals of divergence times depicted as bars at the corresponding nodes. N.B. Although the underlying topology is that delivered by MrBayes, BEAST does not allow polytomies, which it resolves arbitrarily.

Figures 2–22. Morphological, biological, and ecological comparison of the genera and subgenera of Macaronesian Cryptorhynchinae along with the respective sections of the tree; (TS) = type species. Figures 4E and 5E show a section of the tree that results when 16S sequences for Aeoniacalles aeonisimilis* and Dendroacalles euphorbiacus* are excluded.