Dendroacalles, STUBEN, 2005

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 : 58-59

DENDROACALLES STÜBEN, 2005 ( FIGS 3A–E, 4A–E )

Type species: Acalles ornatus Wollaston, 1854

Wollaston, 1854, 1857, 1865; Roudier, 1954; Behne, 2000; Stüben, 2000a, b, c, 2002b, 2004a, 2006, 2007b, 2008a; Stüben, Behne & Bahr, 2003; Stüben & Germann, 2005; Germann & Stüben, 2006; Astrin & Stüben, 2008; Stüben, Fabian & Astrin, 2009 in press.

Compilation of the subgenera and species of the genus Dendroacalles

(N.B. in the following (re)descriptions, bold type indi-

cates taxa from Macaronesian locations for which

DNA sequences are presented.)

Dendroacalles s.s.

Dendroacalles ornatus ( Wollaston, 1854) – Madeira (including type locality)

= Acalles fortunatus Wollaston (1864) syn. Stüben & Germann, 2005: 43 – La Gomera

Dendroacalles sigma ( Wollaston, 1864) – La Palma

Dendroacalles ruteri ( Roudier, 1954) – Tenerife (including type locality), La Gomera, El Hierro, La Palma

Euphorbioacalles Stüben (2005) subgen.

Type species: Acalles brevitarsis Wollaston, 1864

Dendroacalles (Euphorbioacalles) brevitarsis ( Wollaston, 1864) – Gran Canaria

Dendroacalles (Euphorbioacalles) poneli (Stüben, 2000) – Tenerife (including type locality), La Gomera, El Hierro

Dendroacalles (Euphorbioacalles) euphorbiacus (Stüben, 2000) – La Palma

Discussion

The species of this genus have been (re)described by Stüben (2000a). Based on the analysis of morphological characters, 11 of the 29 endemic taxa of Canarian Acalles s.l. have been presented in a preliminary cladogram ( Stüben, 2000b). Furthermore, first hypotheses on biogeography and evolution were proposed for the Canarian Cryptorhynchinae ( Stüben, 2000c) , especially for the species of the recently described genus Dendroacalles ( Stüben & Germann, 2005) .

In the first description of this genus, the five species of the ‘ Acalles instabilis -group’ (now Silvacalles ) were preliminarily included in Dendroacalles ( Fig. 6 ). The reasons for the inclusion were that these species also possess a double sclerotic structure of the internal sac of the aedeagus (endophallus) ( Fig. 6B ), that they show an elongated, canoelike habitus (cf. Fig. 6A ), and that they belong to the ecological group of the so-called ‘tree-climbers’ of the Canarian and Madeiran laurel forest (Stüben et al., 2009 in press; cf. Fig. 6C ). According to our phylogenetic analysis, these tree-climbers represent an artificial grouping ( Fig. 1A ). The species of the Dendroacalles instabilis -group belong to the new genus Silvacalles . As numerous species from the laurel forest herb layer are also included in this taxon, we also describe a subgenus, Silvacalles s.s., that accommodates the instabilis -group (fully supported in our reconstruction).

The host-plant relationships of the more xerothermophilic taxa Dendroacalles poneli (La Gomera, El Hierro, Tenerife: Teno Mts; Fig. 4A ) and D. euphorbiacus (La Palma) have recently been studied much more extensively than for most species of Dendroacalles s.s. from the actual laurel forest ( Stüben, 2004a, 2007b; Stüben & Germann, 2005; Germann & Stüben, 2006). These two species, endemic to the western Canary Islands, belong to the subgenus Dendroacalles (Euphorbioacalles) Stüben, 2005 (in Stüben & Germann, 2005). However in our analysis, this subgenus proved to be paraphyletic with respect to the Dendroacalles s.s. species (cf. Fig. 4E ). The ‘detached’ position of D. euphorbiacus ( Figs 1A , 3E ) is because of the signal of the 16S gene (incomplete lineage sorting?). When analysing the genus only for CO1, Dendroacalles becomes monophyletic (cf. Fig. 4E ).

Our phylogenetic reconstruction implies that Dendroacalles anagaensis (Tenerife, La Gomera) has to be separated from the genus Dendroacalles (to avoid polyphyly). Unlike the already-mentioned species that develop in dendriform taxa of the spurge family ( Euphorbiaceae ), D. anagaensis is the only Macaronesian cryptorhynchine species developing in Echium strictum L., which belongs to the borage family ( Boraginaceae ) (Germann, 2004). Thus, we propose the new monotypic genus Echiumacalles ( Fig. 12A–E ) to accommodate this species. As the above-mentioned double sclerotic structure of the endophallus is also characteristic for Echiumacalles anagaensis , this character must have evolved independently three times during the evolution of the Cryptorhynchinae on the Macaronesian archipelagos; namely in Dendroacalles ( Figs 3B, 4B ), Silvacalles s.s. ( Fig. 6B ), and Echiumacalles ( Fig. 12B ).

The aforementioned hypothesis of Acalles s.l. evolution pointing from the succulent belt into the laurel forest is supported by the position of the highly derived Dendroacalles species in the mitochondrial tree. The supposedly great age of the Macaronesian laurel forest, a forest also characteristic of warm Tertiary Europe, should not be taken to imply that this plant association also shelters life-forms of great age.

Differential diagnosis: See below (‘Key to the genera and subgenera of Macaronesian Cryptorhynchinae’).

Distribution: Canary Islands (except Lanzarote and Fuerteventura), Madeira.

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.