Lauriacalles, 2010

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 : 63-64

LAURIACALLES STÜBEN & ASTRIN GEN. NOV.

( FIG. 10A–E )

Type species by monotypy: Acalles acutus Wollaston, 1864

Wollaston, 1864, 1865; Roudier, 1954; Israelson et al., 1982; Kulbe in: Stüben, 2000a; Behne, 2000; Stüben, 2000a, b, 2007b; Stüben et al., 2003; Stüben & Germann, 2005; Astrin & Stüben, 2008; Stüben et al., 2009 in press.

The species of the genus Lauriacalles Lauriacalles acutus ( Wollaston, 1864) comb. nov. (formerly: Acalles ) – Tenerife (including type locality), La Palma

A detailed redescription of Lauriacalles acutus ( Wollaston, 1864) (formerly Acalles ), the types species of the new monotypic genus, is given by Stüben (2000a: 73–75).

Description

Size: 2.9–4.9 mm.

Head: Rostrum of the ♂ four-fifths as long as pronotum, brown, punctures deep and close; rostrum of the ♀ as long as pronotum, punctures finer and glossy; antennae reddish-brown; insertions of the antennae in (♂) or behind (♀) the middle of the rostrum.

Pronotum: Slender, as long as wide or slightly longer (c. 1.04¥); from the base towards the middle on the side broadening nearly rectilinearly and towards the fore-margin rounded ovally; in front of the foremargin with a lateral depression. The pronotum is more slender than the elytra, which are 1.5¥ wider ( Fig. 10A ). On the disk of pronotum and in front of the scutellum with a small hollow followed by a furrow.

Elytra: 1.40–1.50¥ as long as wide; strongly rounded (bulbously); widest directly in front of the middle; next to the apex more slender and constricted, with a deep lateral depression. On the suture with a small bristled hump, on the second and fourth interval with two and on the third with one bristled hump; the hump of the elytral slope (on the second interval) is very high, with long, robust, and upright elevated aggregations of bristles; on this elytral slope always with a wide, triangular (less often with a v-like), white, and distinctive fascia.

Legs: Very long, the front femur projecting above the front margin of pronotum; femur and tibia more or less clearly annulated with one or two dark rings. Femur with raised, short, and slender bristles; the outer edge of tibia with short and clubbed bristles sticking out vertically; femur and tibia brown, tarsus reddish brown.

Venter: First abdominal sternite very long, longer than the second, the latter as long as or longer than both following sternites combined, fifth sternite again longer.

Aedeagus: Endophallus only with a single ‘fork’- shaped structure ( Fig. 10B ).

Differential diagnosis: The new genus is distinguished from the species of the genera Dendroacalles and Silvacalles s.s. by its lack of the disc-shaped structures above the fork of the endophallus ( Fig. 10B vs. Figs 3B, 4B ). Equally, L. acutus cannot be confused with the species of the genus Aeoniacalles described above: The latter always has a falciform structure at the basal ends of the fork-like structure of the endophallus ( Fig. 5B ) that is not present in L. acutus .

Finally Lauriacalles is compared with the species of the subgenus Tagasastacalles of the genus Silvacalles that also possesses a simple fork-like structure of the internal sac of the aedeagus only slightly different in shape ( Fig. 8B ). The elytral slope of Lauriacalles is covered with humps and very long and upright aggregations of bristles (sticking out almost vertically) of which the anterior ones are coloured dark brown to black and the posterior ones are light brown to white. However, the elytral slope of the species of Tagasastacalles is characterized by smaller humps covered with shorter bristles that are of less contrasting colouring. Furthermore, the apex of the elytra of L. acutus is conspicuously elongated in a ‘beak-like’ way ( Fig. 10A ), whereas the elytra of S. hakani hakani , S. hakani tagasaste , and S. pedestris have only a slight lateral depression towards the apex, which is only slightly elongated (cf. Fig. 8A ). The species of Tagasastacalles are monophagous on Chamaecytisus proliferus Link. ( Fig. 8C ) and L. acutus has exclusively been collected by beating of dead twigs of several species of the laurel family ( Lauraceae ). Thus, confusing these groups is impossible even in the field. See also the ‘Key to the genera and subgenera of Macaronesian Cryptorhynchinae’.

Discussion

The affiliation of this species to any informal taxonomic group has been problematic until now. First it was placed in the group of Acalles sigma ( Stüben, 2000a: 73) , which was then separated as the genus Dendroacalles s.s. However, the option of describing a new genus for the species according to morphological characters only seemed too speculative. Consequently, the species was declared incertae sedis with the comment that ‘according to its habitus, this species is very similar to the species of Dendroacalles . However, it does not have the double structure of the internal sac of the aedeagus which is typical for the genus [cf. Figs 3B, 4B vs. Fig. 10B in current paper]. Hence at present one can only speculate about the phylogenetic position of this Macaronesian species of Acalles as there are no results from molecular genetic investigations to recur to’. (translated from Stüben & Germann, 2005: 42).

The Bayesian analysis underlines the particular position of this new monotypic genus from the Canarian laurel forest ( Fig. 1A ): it appears in a trichotomy, together with the species Pseudodichromacalles fernandezi and the Silvacalles cluster. Merging these genera into one genus, maybe also including Echiumacalles and Ficusacalles , is not an option. Neither can we consider a fusion with just the (equally monotypic) genus Pseudodichromacalles . The impossibility of joining Pseudodichromacalles and Lauriacalles (not even recovered as exclusive sister groups) lies in the morphological and ecological differences regarding habitat preference as well as the markedly different host plants. Whereas L. acutus is a species of the laurel forest (and its substitute vegetative associations or contacting plant communities on Tenerife and La Palma; Fig. 10C ), Pseudodichromacalles fernandezi inhabits the Canarian succulent belt and prefers more arid and open areas (cf. section on biology and ecology of Pseudodichromacalles ).

Etymology: The name Lauriacalles refers to the shady and moist laurel forest of the thermo-Canarian belt that is the habitat of this monotypic genus.

Distribution: Endemic to the Canary Islands Tenerife (including type locality) and La Palma (rare on this island).

PSEUDODICHROMACALLES STÜBEN & ASTRIN

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.