Acalles sierrae

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: 13

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Acalles sierrae


Acalles sierrae  species complex

Huge p-distances but little morphological distinctness

The type locality of Acalles bazaensis Stüben, 2001  is located in the Sierra de Baza (Santa Barbara) in Spain. During the snowmelt in mid-May 2013 we were able to sieve this species under Astragalus  . Like the other species of the Acalles sierrae  group, this species also prefers Fabaceae  host plants. To our surprise, the CO 1 sequence of Acalles bazaensis  was virtually identical to a specimen found in the eastern Sierra Nevada in 2005 under Erinacea anthyllis  . Because of a slightly wider aedeagus, distinct elytra bristles and shorter elytra (digit 41), the eastern one was determined to be Acalles sierrae Brisout, 1865  . The formerly depicted differential characters are therefore certainly not species-specific. It has been found that A. bazaensis  is a junior synonym of Acalles sierrae  , which has been described based on specimens from the Sierra Nevada range. In fact, it is likely the Acalles sierrae  species of the Sierra Nevada (not only there) consists of a complex of morphological closely related (sub-) species, that are virtually indistinguishable from each other. For example, a western A. sierrae  variant of the Sierra Nevada shows a long rostrum (Stüben 2009: 105) which also applies to specimens that were collected by us just 6 km west of the short rostrum variant on the Puerto de la Ragua mountain. The rostrum length of the Puerto de la Ragua specimen is similar to the ones from Sierra Baza, but the p-distance of the CO 1 gene shows at least 6.1 % (1316 -PST and 1318 -PST from Sierra Baza vs. E-0261-sie from Puerto de la Ragua).

Specimens of the Acalles sierrae  complex of the more distant mountain ranges, namely Sierra La Yedra, Sierra Almadén, Sierra Magina and Sierra de la Pandera, show similar large CO 1 p-distances (Tree 1, lower part). These might have slightly wider elytra, but do not provide sufficient morphological characters for species delineation. The differences in the structures of the inner sac of the aedeagus are usually easily comprehensible and a speciesspecific feature. However, in this case they are marginal. They consist of two stripes, more or less parallel in position. We need to accept the fact that the Acalles sierrae  species complex (see key below) cannot be resolved based on morphological characters or standard barcoding genes (CO 1 and 16 S). Further population genetic studies are in preparation. All of these very similar looking variants live in high altitudes—usually above 1300 m—and in isolated mountain massifs of the Betic Cordilleras. They are not found in the plains between the mountain ranges (at least anymore). There could be two possible reasons for this: 1) Under similar environmental conditions, similar structures could have been formed (convergence) or (and more likely), 2) there was not enough time for morphological speciation. In contrast, island species of the Canary Islands and the Madeiran Archipelago show high morphological diversity and very low molecular differences.