A new species, a new combination, and a new record of Crossotarsus Chapuis, 1865 (Coleoptera, Curculionidae, Platypodinae) from China

Abstract This study describes a new species, Crossotarsus beaveri Lai & Wang, sp. nov., designates a new combination, C. brevis (Browne, 1975, comb. nov. from Platypus Herbst, 1793), and notes a new record, C. emorsus Beeson, 1937, from China. Genetic data from four genes indicate that the new species and C. brevis form a clade clustered with other Crossotarsus species. Molecular phylogeny and morphological characters support their taxonomic placement.


Introduction
The genus Crossotarsus Chapuis 1865 was erected for 29 species of pinhole borers. Crossotarsus wallacei (Thomson, 1857) was designated as the type species of the genus (Hopkins 1914). Wood (1993)  Adults of the new species were collected by log dissection. The samples were immediately preserved in tubes containing 99.9% ethyl alcohol, which were stored at −20 °C for DNA extraction and examination. Specimens were examined using an Olympus SZX160 stereoscopic zoom microscope. Photographs were taken with a KEYENCE VHX-6000 Digital Microscope System. All photos were further adjusted and assembled with Adobe Photoshop CS6. Body length was measured between the anterior margin of the pronotum and the elytral apex (head not included).
Genomic DNA was extracted from the adult head. The total genomic DNA was extracted from each individual using the Ezup Column Animal Genomic DNA Purification Kit (Sangon Biotech Co. Ltd). Amplification of four gene fragments (COI, EF-1α, CAD, 28S) was made by PCR, using primers (Table 1) and cycling conditions previously described (Jordal et al. 2011). The PCR products were sent to Sangon Biotech Co. Ltd (Shanghai, China) for sequencing, and the sequences were analyzed using the software DNAstar. Additional information on Crossotarsus material was collected by the authors in China or downloaded from NCBI (The National Center for Biotechnology Information) ( Table 2). Concatenated DNA sequence data from Jordal (2013) were analysed in MrBayes v. 3.2.6 (Ronquist et al. 2012). Partitions and models were estimated by PartitionFinder 2 (Lanfear et al. 2017) and ModelFinder (Kalyaanamoorthy et al. 2017) respectively in PhyloSuite (Zhang et al. 2020), GTR+G+I were selected for each partition. 10 million generations were run, with 25% of the generations as burn-in. PSRF close to 1.0 and standard deviation of split frequencies below 0.01 were accepted.   males RIFID; 2 males, 2 females SYU; 2 males, 2 females USNM; 2 males, 2 females ZIN; 20 males, 20 females JXAU).
Head. Frons flat, slightly shining, with irregular large punctures; finely, sparsely punctured above the epistoma, bearing bristly, erect, long setae, weakly concave, smooth around short median line, upper part of frons with scattered, coarse punctures, the punctures with moderate, semierect, dorsally directed setae. Antennal scape clavate with scattered, forwardly directed hairs on apical half; club oval, flattened, evenly covered with short setae. Labial palps two-segmented, with basal segments fused along the midline.
Pronotum. About 1.2 times longer than wide, shining, no mycangial pores, the lateral femoral grooves angulate anteriorly, pronotum widest in front of the grooves, with finely, scattered, irregular punctures, a few semierect backwardly pointed hairs close to anterior margin, median line extending about 1/4 from base.
Scutellum. Depressed below level of elytra, with a median longitudinal groove between lateral carinae.
Elytra. About 2.0 times as long as wide, about 1.4 times as long as pronotum. Surface of disc smooth, shining, striae distinctly impressed for almost their entire length, except striae 6 and 7, other striae with circular, distinct, shallow punctures, the bases of striae 1 and 2, striae 3 and 4, respectively, conjoint, more impressed; interstriae slightly raised on disc, interstriae 1, 3 and 5 distinctly raised and conjoint at base, interstriae 8 and 9 fused at apex of disc, forming ventral, rounded angle; cylindrical declivity obliquely truncate, acutely margined all around except at sutural apex, strongly concave, forming a cup-like structure, surface shining, with 4 rows of longitudinal granules bearing erect, long, golden setae, a row of sparse, medially directed, erect golden setae at the inner margin of declivity, elytral apex broadly emarginate, the main emargination approximately U-shaped, about as wide as deep, extending about 1/3 of the height of the declivity, at its inner end a much smaller, V-shaped second emargination (Fig. 1A, D).
Head. Similar to male, but frons flatter, very shining, smooth, with shallow, small punctures; finely, sparsely punctured above the epistoma, bearing bristly, erect, long setae; very shallowly concave in median line, upper part of frons with scattered, shallow, small punctures, the punctures with moderate, semierect, dorsally directed setae.
Pronotum. Similar to male. Elytra. About 1.8 times as long as wide, about 1.5 times as long as pronotum, sides subparallel. Similar to male, but disc of elytra shining, with dense, longitudinal, semierect, backwardly pointed hairs at apex and declivity, striae weakly impressed, interstriae smoother, declivity vertical, a few irregularly granules, sparsely hairy.
Etymology. The species is named for Roger A. Beaver to honor his contributions to the study of platypodines and scolytines. Distribution. China (Jiangxi, Fujian).

Diagnosis. The species is placed in Crossotarsus because it possesses a combination of characters similar to that cited in the introduction.
Crossotarsus beaveri is very similar to Crossotarsus brevis (Browne, 1975) (new combination, see below) and Crossotarsus platypoides (Browne, 1955). They can be easily distinguished from other Crossotarsus species by the male elytral apex truncate with a large, circular, concave declivity. The elytral apex of male of C. beaveri and that of C. brevis possess a deep, acutely margined declivity, with a broad, almost circular, apical emargination.
Key to the species of Crossotarsus with a circular, truncate elytral declivity Male striae weakly impressed on disc of elytra (Fig. 1A); declivity gradually, obliquely truncate, its face shining, cylindrical, apex rounded with a double sutural emargination, borders of inner emargination weakly elevated, outer emargination forming pointed angles; surface of declivity with 4 longitudinal rows of granules, bearing erect, long golden setae (Fig. 1D). Female frons flat, more shining, smoother, very shallowly concave in median line; dense, shallow, small punctures bearing semierect hairs on upper part; almost flat above the epistoma below median line (Fig. 2B); striae weakly impressed on disc of elytra ( Fig. 2A) Male striae moderately impressed on disc of elytra (Fig. 3A); declivity abruptly, vertically truncate, its face subnitid, cylindrical, apex rounded with a double sutural emargination, borders of inner emargination distinctly elevated and dilated, outer emargination forming obtuse angles; surface of declivity with sparse, obscure granules, bearing erect, long golden setae (Fig. 3D). Female frons slightly shining, reticulate, very distinctly concave, smooth around median line; dense, deep, large punctures bearing semierect hairs on upper part; weakly, irregularly impressed above the epistoma below median line (Fig. 4B); striae moderately impressed on disc of elytra (Fig. 4A) Taxonomy. The specimens in the RAB were identified by comparison to a paratype C. brevis, which is also in the RAB. Browne put this species in Platypus Herbst, noting that the apical emargination of the elytra was rather similar to that of Platypus caliculus Chapuis 1865 (Beaver and Browne 1975). In fact, C. brevis has the typical characters of Crossotarsus: labial palps two-segmented, with basal segments fused in the midline, whereas Platypus has the labial palps three-segmented, with separate basal segments. Beaver (1998) transferred the species from Platypus to Dinoplatypus Wood following Wood's (1993) attempt to split the genus Platypus. Wood diagnosed Dinoplatypus largely on the basis of the circular, truncate, elytral declivity of the male, with the sutural apex emarginate. However, this is an adaptive character of the declivity which has evolved independently more than once in the Platypodinae, as it has in the Scolytinae (Hulcr et al. 2015). Molecular phylogenetic study also shows that the few morphological characters used by Wood (1993) to erect several groups of Neotropical and Indo-Malayan/Australasian species in Platypodini to new genera are not sufficiently diagnosable for all those groups (Jordal 2015). Browne (1961) and Beaver and Sanguansub (2015) suggested that the adult generic characters of primary value in Crossotarsus included the structure of the labial and maxillary palps, the form of the pronotum, the sexual dimorphism of the protibia, and various modifications of the abdominal sternites in the male. Based on the twosegmented labial palps, the lateral pronotal emarginations angulate anteriorly, the pronotum without mycangial pores, and the sexual dimorphism of the protibiae, Platypus brevis belongs in the genus Crossotarsus, and is here transferred to that genus.
Host. The species is recorded from trees in the families Lecythidaceae, Fabaceae, Sterculiaceae and Verbenaceae (Beeson 1937), and is presumably polyphagous (Beaver 2016 Molecular data. The phylogenetic tree for analyzing the evolutionary relationships of 13 taxa including the ingroups (Crossotarsus species) and the outgroups (P. contaminatus) was constructed based on four genes (Fig. 7). The BI tree shows the new species (C. beaveri) and the new combination (C. brevis) forming a clade, with high node support. These group with Schedl's (1972a) 'Crossotarsi coleoptrati' (C. fractus Sampson, 1912, C. squamulatus and C. terminatus) and cluster with all remaining Crossotarsus species. It confirms that the taxonomic changes and the relationship of C. brevis and C. brevis are correct. It also indicates that C. emorsus, C. fractus, C. squamulatus and C. terminatus should be considered distinct species (as by Beaver and Liu 2013), and not considered synonyms or subspecies (Schedl 1972a).

Discussion
Crossotarsus beaveri is clearly related to C. brevis. They are the sister lineage to the Crossotarsi coleoptrati group, not the genus Dinoplatypus. This is a good example that declivity in males usually is an adaptive character and not of generic significance. We consider that the morphologically diagnosable characters of the genus Crossotarsus should refer to the summary by Browne (1961) and Sanguansub (2015, 2020), as introduction.  The genus Crossotarsus is one of the largest genera of Platypodinae, with more than 100 species. Although there are 13 previously recorded species of Chinese Crossotarsus (Yin and Huang 1987;Yin et al. 2002;Zhang et al. 2008), many additional species have been reported from countries neighboring China (Beaver and Shih 2003;Goto 2009;Beaver and Liu 2013;Beaver 2016) which still have not been found in China. This strongly indicates that many more species remain to be discovered, especially on the Chinese mainland. Crossotarsus is monophyletic in the latest molecular phylogeny (Jordal 2015). There are few molecular data for the genus in GenBank, less than 10% of the whole. More taxonomic samples are needed. Male size 4.56-4.80 mm long, 3.20-3.42 times as long as wide; Male size 3.32-3.40 mm long, 2.78-3.00 times as long as wide; Female size 4.8-5.34 mm long, 3.38-3.43 times as long as wide. Female size 3.44-3.58 mm long, 2.87-2.93 times as long as wide.

Frons
Male frons almost flat, with shallower, irregularly placed punctures; circularly concave in median line.
Male frons coarser, with deeper, irregularly placed punctures; linearly concave in median line. Female frons almost flat, without concave around median line. Female frons concave forming a big, circular impression around concave median line. Elytra Male without lateral emargination at declivity base, semicircular lateral borders with serrated, lateral tubercles.
Male with lateral emargination at declivity base, semicircular lateral borders rounded, without distinct serrated, lateral tubercles.