Apatrobus hekosanus Sasakawa, 2020

Sasakawa, K., 2020, A new species of the genus Apatrobus Habu et Baba, 1960 (Coleoptera: Carabidae: Patrobini) from Japan, Far Eastern Entomologist 413, pp. 1-7 : 3-6

Apatrobus hekosanus Sasakawa , sp. n.

http://zoobank.org/NomenclaturalActs/ 6BCCCA09-D865-48C2-BEA3-8B5E4D19A4BE

Figs 1–9

TYPE MATERIAL. Holotype: ♂, Japan: Fukui Prefecture, Ôno City, Hôkyôji ,

Mt. Hekosan, alt. 1100 m, 30.IX 2019, leg. S. Inoue [CHUJ].

DESCRIPTION. Dorsal surface ( Fig. 1 ) black and shiny, without metallic luster.

Appendages dark brown.

Head widest at mid-eye level; mandibles short; labrum 6-setose, with anterior margin weakly emarginate; frontal impressions large and deep, with posterior ends reaching those of the eyes; surface of frontal impressions markedly punctate; frons almost smooth; two pairs of supraorbital setae, anterior pair at mid-eye level and posterior pair at the level of the basal 1/3 of tempora; longitudinal line between eye and supraorbital seta deep and long, with posterior ends reaching apical 1/3 of tempora; eyes convex and almost the same length as tempora; tempora swollen,

with the surface almost smooth; mentum tooth bifid, with a pair of setae at base;

submentum with two pairs of setae. Antennae long; segments 1–2 without pubes-

cence; one seta on segment 1; three setae on segment 2.

Pronotum quadrate, widest at apical 1/3; anterior margin weakly emarginated;

posterior margin almost straight; lateral margins arcuate at apical 2/3, slightly sinuate at basal 1/3; anterior angles barely produced; posterior angles almost right-

angled, with apices narrowly rounded; two pairs of marginal setae, anterior pair at apical 1/3 and posterior pair at the tip of hind angle; surface with punctations at anterior, lateral, and posterior margins and laterobasal impressions; laterobasal impression single and deep; median line deep in mid-region, but absent near anterior margin and rudimentary near posterior margins.

Elytra oblong, widest slightly behind middle; shoulders rounded, without a denticulate tooth; apices narrowly rounded, but not denticulate; intervals almost flat; scutellar stria present, but not connected to stria 1; one dorsal pore at the anterior end of stria 1; three dorsal pores on interval 3, the anterior two adjoining stria 3 and the posterior one adjoining neither stria 2 nor stria 3; hind wings atrophied.

Ventral side with punctations at neck base, prosternum, episternum, and lateral sides of sternum 2; sternum 7 with a pair of setae in holotype male. Legs stout; hind tarsomeres with two to three setae on both ventrolateral margins.

surface membranous except for apical part; apical part thick from lateral view, widely rounded from dorsal view. Right and left parameres ( Figs 4, 5 ) almost the same shape, broad, barely protruded at their apices; right paramere slightly smaller than left paramere.

aedeagus, left lateral view; 3 – aedeagus, dorsal view; 4 – left paramere, left lateral view; 5 –

right paramere, left lateral view; 6 – endophallus, left lateral view; 7 – endophallus, dorsal view; 8 – endophallus, right lateral view; 9 – ligula, dorsal view. Abbreviations: gp – gonoporal piece; lb – left basal lobe; lg – ligula; ss – spiny sclerites.

Endophallus ( Figs 6–8 ) short, directed left dorsolaterally; left dorsolateral surface near ostium largely swollen (left laterobasal lobe); ligula ( Fig. 9 ) crescent,

widest at basal 1/3, with apex narrowly pointed; spiny sclerites densely developed;

gonoporal piece large, strongly sclerotized.

MEASUREMENTS. BLm 8.51 mm; BLl 8.25 mm; BLc 8.00 mm. PW/HW 1.29;

PW/PL 1.23; PW/PA 1.37; PW/PB 1.31; PA/PB 0.95; EW/PW 1.30; EL/EW 1.63.

Length along the midline of ligula on the endophallus 1.13 mm.

DIAGNOSIS. New species similar to locally adjacent species ( A. echigonus , A.

hasemiya, A. iwasakii , and A. narukawai ) in general appearance, but distinguished from them as follows (see also Table 1): from A. echigonus by narrower, quadrate pronotum (PW/PL 1.26–1.30 and cordate in A. echigonus ) and more pointed apex of ligula on the endophallus; from A. hasemiya by larger body (BLc 7.38–7.82 mm

in A. hasemiya ), longer and arcuate ligula (smaller and not arcuate in A. hasemiya ),

and larger and strongly sclerotized gonoporal piece (gonoporal piece small and only weakly sclerotized in A. hasemiya ); from A. iwasakii by smaller body (BLc 8.25–

8.40 mm in A. iwasakii ), larger right paramere with the apex not protruded (smaller

4

and protruded in A. iwasakii ), crescent and longer ligula (wedge-shaped and shorter in A. iwasakii ), and thicker aedeagal apex; and from A. narukawai by smaller body

(BLc 8.55–9.75 mm in A. narukawai ), narrower, quadrate pronotum (PW/PL 1.28–

1.38 and cordate in A. narukawai ), longer ligula (<1.00 mm in A. narukawai vs

>1.00 in A. hekosanus ), and thicker aedeagal apex.

DISCUSSION

Unexpectedly, A. hekosanus is more similar morphologically to distant species than the nearest species P. iwasakii ( Fig. 10 ; Table 1). Of the five characters for which interspecies differences are recognized (four genital and one external characters), A. hekosanus shares only one character state with A. iwasakii , but four, four,

and three character states with A. echigonus , A. hasemiya , and A. narukawai , res-

pectively. In particular, the narrower quadrate pronotum shared by A. hekosanus and A. hasemiya is found only in these two species within Apatrobus (Morita, 1985);

thus, this character state in the pronotum is considered apomorphic within the genus and is probably a synapomorphy uniting these two species as sister taxa.

hasemiya ; 3 – A. hekosanus sp. n.; 4 – A. iwasakii ; 5 – A. narukawai .

The finding that A. hekosanus is probably more closely related to a more distant species, A. hasemiya , than to the nearest species A. iwasakii might be explained by speciation along an elevation gradient. A. hekosanus and A. hasemiya occur at high altitudes, whereas A. iwasakii occurs at low altitudes ( Table 1). For Apatrobus , differences in elevation between nearby localities may have greater effects as geographic barriers than differences in horizontal distance at higher elevations. This assumption is compatible with the fact that of the five species compared, only A. iwasakii , which occurs at low altitudes, has many peculiar morphological characters ( Table 1).

altitude of the type locality of five Apatrobus species.

In Apatrobus , similar, putative speciation along an elevation gradient was re-

ported between two closely related species in Shikoku: A. satoui (Habu, 1976) and

A. tsurugiensis (Habu, 1976) (Dejima & Sota, 2017) . Of the two, A. satoui occurs at low altitudes and A. tsurugiensis is at high altitudes, and their distributions are geographically very close to each other. Morphological similarities and possible distributional continuity have led some authors to question the independence of these two species (e.g., Nakane, 1978). However, morphometric and molecular phylogenetic analyses have shown that A. satoui and A. tsurugiensis are clearly differentiated, which is a typical result of speciation along an elevation gradient

(Dejima & Sota, 2017). The relationships among A. hekosanus and related species also need to be analyzed in ways similar to those performed for A. satoui and A.

tsurugiensis.

Figures

Figs 1–9. Apatrobus hekosanus sp. n., holotype male. 1 – habitus, dorsal view; 2 –

Fig. 10. Distributions of Apatrobus spp. in Central Honshu. 1 – A. echigonus; 2 – A.