Ambrosiophilus Hulcr & Cognato

Hulcr, Jiri & Cognato, Anthony I., 2009, Three new genera of oriental Xyleborina (Coleoptera: Curculionidae: Scolytinae), Zootaxa 2204, pp. 19-36 : 21-22

Genus Ambrosiophilus Hulcr & Cognato gen. n.

Type species: Ambrosiodmus restrictus ( Schedl) 1939 .

Diagnosis: Similar to the related genus Ambrosiodmus , from which it differs by the absence of asperities on pronotal disc, and by flat, not rounded, pronotal disc. Ecologically, many species of Ambrosiophilus are associated with other xyleborines, which is not known for any Ambrosiodmus . Other similar species are included in a complex of species ( Xyleborus decumans Schedl , X. dimidiatus Eggers , and X. tunggali Schedl ), from which Ambrosiophilus differs by the antennal club type 3, the club being approximately rounded (not broad), flat frons, parallel striae 1 (as opposed to divergent), and steep elytral declivity.

Description: Eyes shallowly emarginate, upper portion of eyes smaller than lower part. Antennal club more or less circular in shape, club type three (with first segment straight or convex). First segment of club straight (may be slightly concave or convex) on anterior face, margin of the first segment mostly costate, may appear softer on posterior side. Second segment of club visible on both sides of the club, either soft and pubescent, or corneous on one side of the club, or corneous on both sides of club. Third segment of club clearly visible on both sides of the club. First segment of antennal funicle shorter than pedicel, funicle composed of 4 segments, scapus of regular shape (relatively robust and curved, not long and slender). Frons above epistoma mostly smooth, alutaceous, with minor punctures, or rugged, coarsely punctate. Submentum flat, flush with genae, or slightly impressed, narrow (shaped as a very narrow triangle). Anterior edge of pronotum with no conspicuous row of serrations (at most serrations that do not differ from those on the pronotal slope). Pronotum from lateral view sometimes of basic shape (type 0), but mostly tall (type 2), flat on the disc and rounded or bulging on the frontal slope (type 4). From dorsal view it is basic, short, parallelsided, rounded frontally (type 2). Pronotal disc densely and evenly punctured, lateral edge of pronotum obliquely costate. Procoxae contiguous, prosternal posterocoxal process short, conical or flat, inconspicuous, or tall and pointed, or conical and slightly inflated. Tuft on pronotal basis associated with mesonotal mycangium absent, setae on elytral bases associated with elytral mycangium absent. Scutellum flat, flush with elytra. Elytral bases straight, with oblique edge, elytral disc longer than declivity, flat, elytral disc with distinct punctures in strial lines. Lateral profile of elytral declivity flat or rounded, sometimes steep or very steep. Dorsal profile of elytral apex rounded, often broadened laterally. In one species ( A. sexdentatus ) the declivity is excavated. Elytral declivity with few setae or scales, not conspicuously pubescent. Posterolateral costa ending on 7th interstriae. The inner part of declivity has no tubercles on interstria 1 (sutural), and several tubercles on interstriae 2, 3 and beyond. First interstriae are parallel (sometimes slightly broadened towards elytral summit). Protibiae with evenly rounded edge, or obliquely triangular, broadest at 2/3 of the length. Posterior side of protibia flat, without tubercles (setae only). Protibial denticles large, distinctly longer than wide, bases of the denticles not enlarged or only slightly enlarged, usually between 6 and 8 protibial denticles present. Metatibiae of regular size. Body length between 2.4 and 3.2 mm. Mostly black, sometimes dark brown.

Discussion. The genus represents either a sister group or a subgroup of Ambrosiodmus Hopkins. Most of its species were in fact until now included in Ambrosiodmus ( Wood & Bright, 1992) . Their sister-clade relationship to Ambrosiodmus is also supported by a five-gene molecular phylogeny (Cognato et al., unpublished). There are two main reasons for separation of the two genera. The first is the inconsistent morphological definition of contemporary Ambrosiodmus . Ambrosiodmus has traditionally been defined by an autapomorphic asperate surface of pronotal disc. In many species, including the type species A. tachygraphus (Zimmermann) , the pronotum is different than in most other genera of Xyleborina, both in terms of its surface and its very globular shape. However, a number of species currently included in the genus lack the asperities and were presumably included based on superficial resemblance. On the other hand, a number of other species were included only because of this one character, while other characters contradicted it. The transfer of several such species from Ambrosiodmus into Ambrosiophilus will help to alleviate this ambiguity. The second reason to recognize the new genus is the special ecological adaptation seen in many (not all) Ambrosiophilus spp. but never observed in Ambrosiodmus s. str., that is, parasitism of fungal gardens of other ambrosia beetles.