Acalles maraoensis

Schütte, André & Stüben, Peter E., 2015, Molecular systematics and morphological identification of the cryptic species of the genus Acalles Schoenherr, 1825, with descriptions of new species (Coleoptera: Curculionidae: Cryptorhynchin, Zootaxa 3915 (1), pp. 1-51: 12

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Acalles maraoensis


Acalles maraoensis  species complex

Small p-distances but high morphological distinctness

At a first glance the four species of the Acalles maraoensis  clade offer a uniform appearance like all other species that belong to the Acalles sierrae  group of the Spanish and Northern African high mountains (fig. 7; couplets 32–41, ‘Key to the species of Acalles’). These montane open-landscape species have long, oval, egg-shaped, rarely obovate elytra. The intervals of the elytra are much broader than the striae. The integument is consistently dark brown in most species, occasionally with a faded, not rich in contrast, beige spot of scales in front of the base and / or with an indicated fascia behind the middle of the elytra. The elytral bristles are placed distantly in a single row, often at a distance 2 to 3 times bristle length. There are no tufts of bristles like many central European forest species. In this respect, the bristle structure is similar to that of Echinodera  . The pronotum is nearly always dark brown and laterally bulbous and rounded, and it is therefore clearly distinct from the broader elytra, which are 1 to 2 intervals wider than the pronotum. The eyes are circular. The rostrum in both sexes is strikingly narrow, and it is approximately as long as the pronotum in the females.

Differences in the previously described exoskeletal traits are not extensive or overlap with intraspecific variability within these species. A reliable feature for determination of species of the Acalles maraoensis  clade ( A. sarothamni  , A. monasterialis  , A. cytisi  and A. maraoensis  ) is the shape of the median lobe (apex of aedeagus) and the internal sac structure of the aedeagus (couplets 32-43: ‘Key to Acalles  ’), and for A. cytisi  , by using the apically split mid-tibia spine. At least for male specimens, morphological assignment to one of the known species is thus quite possible based on the aforementioned characteristics.

According to the molecular results of the CO 1 gene analysis, species differentiation is not possible. The phylogenetic reconstruction (Tree 1, lower part) depicts a paraphyletic conflict with the A. maraoensis  group. Within the last few years these results have been checked repeatedly—genetically and morphologically. For Cryptorhynchinae  systematics, the mitochondrial CO 1 gene provided reliable results in virtually 98.5 % of the cases, but it is not sufficient for species differentiation within the A. maraoensis  group. This is a rare case, but also not the only one in which CO 1 fails ( Bourke et al. 2013).

A similar inconsistency between the morphological and molecular method, can be observed between A. testensis  and A. asniensis  . These two species from the Morcoccan high mountains do not show extensive exoskeletal differences, but have a totally different internal sac structure of the aedeagus (digit 35). The p-distance between these two species is just 3.2 % for CO 1 gene and 0.9 % for the 16 S gene.

These values are necessary to evaluate the situation described below. Also, the newly described species Acalles iblanensis  can be found within the Moroccan high mountains and has an apically split mid-tibia spine. Acalles iblanensis  is the sister species to A. testensis  and A. asniensis  . Not only does the aedeagus show significant differences (couplets 34, 35), but also the p-distances of A. iblanensis  relative to its sister species are at least 11.2 % for the CO 1 gene and 2.2 % for the 16 S gene, much larger than the examples cited above. Based on these facts one may assume we are on the safe side for a new species differentiation and description.