Dorcadion axillare moldavicum, Dascălu, Maria-Magdalena & Fusu, Lucian, 2012

Dascălu, Maria-Magdalena & Fusu, Lucian, 2012, Dorcadion axillare Küster, 1847 (Coleoptera, Cerambycidae): distribution, morphometrics, karyotype and description of a new subspecies from Romania, Zootaxa 3322, pp. 35-48 : 39-47

Dorcadion axillare moldavicum ssp. nov

Type material. Holotype, 3: Romania, Iaşi county, ‘Valea lui David’ Nature Reserve, leg. Dascälu & Fusu, 18.IV.2008 (first author’s collection). Paratypes: Romania, Iaşi county, ‘Valea lui David’ Nature Reserve: leg. Fusu L., 19.V.2004, 73 2Ƥ; leg. Dascälu M., 10.X.2004, 1Ƥ colected as pupa from pupal cell in soil under roots of Stipa sp.; leg. Dascälu M., 8.V.2005, 13; leg. Dascälu M., 14.V.2005, 1Ƥ; leg. Dascälu M., 16.IV.2006, 1Ƥ; leg. Fusu L., 17.IV.2006, 23; leg. Fusu L., 21.IV.2006, 33 2Ƥ; leg. Dascälu M., 12.V.2006, 13; leg. Dascälu M., 13.V.2006, 23 1Ƥ; leg. Dascälu M., 29.V.2006, 1Ƥ; leg. Dascälu & Fusu, 24. IV.2007, 131Ƥ; leg. Fusu L., 18.V.2007, 13; leg. Dascälu & Fusu, 29.III.2008, 13; leg. Dascälu & Fusu, 18.IV.2008, 103 3Ƥ; leg. Dascälu & Fusu, 25.IV.2008, 33; leg. Fusu L., 17.IV.2011, 13; leg. Dascälu & Fusu, 27.IV.2011, 43 4Ƥ (first author’s collection); leg. Fusu L., 19.V.2004, 43 1Ƥ; leg. Dascälu M., 8.V.2005, 33 3Ƥ ( MHNB); leg. Dascälu M., 16.IV.2006, 13; leg. Dascälu M., 18.IV.2008, 1Ƥ; leg. Dascälu & Fusu, 25.IV.2008, 13 (Natural History Museum of Iaşi); Romania, Iaşi county, Rediu village, Mârzeşti: leg. Fusu L., 20.V.2004, 13; leg. Dascälu M., 25. IV.2005, 13; leg. Fusu L., 3.V.2007, 1Ƥ; leg. Chinan V., 17.IV.2011, 1Ƥ; Romania, Vaslui county, ‘Movila lui Burcel’ Nature Reserve, near Chirceşti: leg. Fusu L., 28.IV.2011, 13 (first author’s collection); Romania, Vaslui county, Chirceşti, slope with steppic vegetation by the highway, leg. Dascälu, Fusu & Chinan: 27.IV.2006, 13 ( MHNB); 27.IV.2006, 63 3Ƥ; 23.V.2007, 33; 11.V.2008, 43 1Ƥ; 28.IV.2011, 83 2Ƥ (first author’s collection).

Etymology. The subspecies is named after the historical region Moldova, where the type locality is situated.

Description. Male ( Fig. 6 g). Body length: 11.3–14.3 mm; body width: 4.2–5.3 mm. Gena 0.62–0.88 times as long as width of lower eye lobe; antennae reaching apical 1/3 of elytra; first antennal joint 1.1–1.2 times as long as the third. Pronotum subquadrate, 0.94–1.12 as long as wide at base, with a sharp spine at each side ( Figs 5 h, 6g). Elytra 1.71–2.09 times as long as wide, with humeral prominences rounded but evident; humeral carinae well developed in basal 2/3 of elytra but traceable almost to apex; external dorsal carinae present in basal 1/3 of elytra. Genitalia as in Figs 5 d, f–g, 6j. Body black; antennae almost black with first and sometimes also the second antennal joint brownish red. Legs brownish red, with blackish tarsi. Head with a median white stripe and two black lateral spots. Pronotum covered with dense, black pubescence, with a median white stripe and moderately developed lateral grey pubescence. Elytra with dense, dull black pubescence and white sutural and lateral stripes; small spots of velvety black pubescence near sutural stripe; humeral stripe reduced to a small, white humeral spot.

Female ( Fig. 6 h). Body length: 13–16.1 mm; body width: 5.5–6 mm. Gena 0.77–0.95 times as long as width of lower eye lobe; antennae not reaching middle of elytra; first antennal joint 1.4–1.5 times as long as the third. Pronotum transverse, 0.76–0.9 times as long as wide at base, with longer and sharper spines ( Fig. 5 i). Elytra 1.58–1.78 times as long as wide, with more evident humeral prominences and elytral carinae.

Variation. The specimens from Mârzeşti (Rediu village), situated at five km in strait line from ‘Valea lui David’, are morphologically identical with those from the type locality. We also regard the specimens from Chirceşti, 20 km southern from the type locality as Dorcadion a. moldavicum ssp. nov.; they are similar to those from ‘Valea lui David’ in pronotum shape, pronotal spine length and male genitalia ( Figs 5 e, 6d, e) but are slightly smaller in size. Also this population has both androchrome and autochrome females ( Fig. 6 f) the latter form being very rare (only one specimen collected in several years).

Morphometric analysis. All the univariate measures (pL, pbW, eL, eW, bL) for the northern and southern populations are largely overlapping, even though the differences between mean values are statistically significant. When variables are combined as ratios (bivariate analysis) only pL/pbW is almost not overlapping ( Table 1 ) and can be used to separate the two groups of populations ( Bulgaria and Romanian Dobruja versus NE Romania); a bivariate plot showing this is presented in Fig. 3 .

The PCA extracted five components based on the seven analysed variables. In the scatterplot ( Fig. 4 ) only the first two principal components are shown as they account together for 86.67 % of the total variance (67.72% for PC1 and 18.95 % for PC2). Although some overlapping exists, the two clusters that correspond to the two groups of populations ( Bulgaria and NE Romania) are evident. The population from Chirceşti lays in-between the two clusters but it overlaps more with D. axillare moldavicum cluster. Table 2 shows the proportion of variance, the eigenvalues and the contribution of each variable to the first two components. Along the first component pL, eL and bL have a high contribution, and eL/eW the smallest one. Along the second component pL/pbW and eL/eW have the largest weight and bL almost none.

Comparative note. Dorcadion axillare moldavicum ssp. nov. differs from the nominal subspecies in its bigger and more elongated body (length up to 14.3 mm in males and 16.1 in females), elongated pronotum which in males is about 1.1 times longer than wide at the base to subquadrate (usually 0.8–0.9 times in D. axillare axillare males), much longer pronotal spines (short or nearly absent in almost all specimens of the nominal subspecies) ( Fig. 5 h–l), presence on the endophalus (on the ventral side of the median tube, before the central chamber) of a small spine which is absent in the nominal subspecies ( Figs 5 c–e, 6i, j), and absence of autochrome females in the most northern populations.

The population from Chirceşti is characterized by a smaller body length (in males 10.5–13 mm, with a mean of 11.84 mm, n = 22 and 12.5–14.5 mm in females, with a mean of 13.3 mm, n = 6), which makes it more similar to the nominal subspecies; unlike the population from the type locality the Chirceşti population has both androchrome and autochrome females, but the latter ones are apparently different from those in Bulgaria having the humeral and dorsal elytral stripes broadly fused at elytral apex ( Fig. 6 c, f).

Cytogenetics. The karyotype of D. axillare moldavicum ssp. nov. has 24 pairs of chromosomes that we divide into three groups based on centromere position and size ( Fig. 7 a–d). The first group (I) is represented by four pairs of large chromosomes, three acrocentric and the fourth metacentric-submetacentric (in fact pseudoacrocentric, as shown by C banding); the second group (II) is formed by two pairs of metacentric chromosomes, those in the second pair evidently smaller. The third group (III) has five pairs of small chromosomes, the second pair submetacentric and the others acrocentric; the X chromosome belongs to this group. The chromosome number observed in the metaphasic plates is confirmed by the observations in male meiosis. All autosomes form regular pairs, and the sex bivalent is parachute shaped, easily distinguished because of this heteromorphy (male meioformula 11 + Xy p); the heterosomes are the smallest from the entire chromosomal set ( Fig. 7 e, f). In the C banding karyotype ( Fig. 7 c) all the chromosomes have small blocs of pericentromeric heterochromatin, except pair 3, where the short arm is entirely heterochromatic. This chromosome is in fact pseudoacrocentric (an acrocentric chromosome with extraordinarily elongated, heterochromatic short arm) and not metacentric, if it is to follow the terminology proposed by Imai (1991).

The ideograms for ‘Valea lui David’ and Chirceşti populations are shown in Fig. 8 . Statistically significant differences exist between the 3rd and 4th pairs of chromosomes. Chromosome 3 is longer in Chirceşti population (relative chromosome length is 10.4% of the total haploid complement length compared with 9.3% in ‘Valea lui David’ population); chromosome 4 is longer in ‘Valea lui David’ population (10.3% compared with 9.4%) and the centromeric indices are also different (r = 1.8 compared with r = 2.6 for Chirceşti population). The differences that appear between the chromosomes 4 of the two populations are due to the elongation of the completely heterochromatic short arm and not to a pericentromeric inversion, the long arm having the same length in both populations ( Table 3 ). The differences that appear in the size of the Y chromosome ( Fig. 8 , Table 3 ) could be due to the small number of measurements.

A karyotype with nine pairs of autosomes plus one pair of heterosomes (9 + Xy p male meiotic chromosome formula) is the most common karyotype in Polyphaga and as a result, this condition has been suggested to be the primitive character state of the suborder ( Virkki 1984; Gómez-Zurita et al. 2004). In Lamiinae , as in most Cerambycidae , 9 + Xy p male meioformula is by far the most common situation ( Smith & Virkki 1978; Dutrillaux et al. 2007). Monochamini and Lamiini are groups closest to Dorcadionini ( Danilevsky et al. 2005) and most of their species have a karyotype with nine pairs of autosomes ( Smith 1953; Lanier & Raske 1970; Cesari et al. 2005), but in Monochamus sartor (Fabricius) and Morimus funereus Mulsant , 2n = 24 (male meioformula 11 + Xy p) similar to D. axillare ( Cesari et al. 2005; Dutrillaux & Dutrillaux 2011). It seems that a karyotype with 2n = 24 is apomorphic and perhaps a synapomorphy for Morimus plus Dorcadionini , but more data are needed to confirm this.

Ecology. D. axillare moldavicum ssp. nov. inhabits hill slopes with xerophilic vegetation. One specimen was found as pupa under the roots of Stipa sp. and it is very likely that this is one of the food plants of this taxon.

Distribution. The nominal subspecies is distributed all over Bulgaria and in S Romania (Banat and Dobruja) ( Fig. 9 ). The record of D. arenarium v. axillare from Cornurile, Prahova Valley ( Montandon 1908) was connected with a dark form of Dorcadion pusillum Küster (1Ƥ, Roumanie, Cornurile Prahova, A. L. Montandon, in MHNB). The specimens from Babadag (Dobruja), listed above under examined material, were wrongly mentioned as D. pusillum ( Panin & Sävulescu 1961) . D. axillare moldavicum ssp. nov. is known so far from three populations, two near Iaşi city (‘Valea lui David’ and Mârzeşti) and one in the north part of Vaslui county (Chirceşti).

Figures

FIGURE 3. Relationship between pronotum length (pL) and pronotum base width (pbW) in Dorcadion a. axillare and D. a. moldavicum ssp. n.

FIGURE 4. Plot of the first two components from the Principal Component Analysis of the log-transformed data based on the correlation matrix.

FIGURE 5. Endophallus. (a) Dorcadion arenarium, Croatia, Krk Island and (b) Italy, Ripalda, (c) D. a. axillare, Bulgaria, Stara Zagora, (d) D. a. moldavicum, Romania, ‘ Valea lui David’ and (e) Chirceşti. Aedeagus. D. a. moldavicum: (f) median lobe, (g) parameres. Pronotum. (h) D. a. moldavicum, male and (i) female, (j, k) D. a. axillare, males and (l) female. Abbreviations. (bt) basal tube, (mt) medial tube, (ct) central trunk, (cb) central chamber with (vs) ventral swelling and (vp) ventral plates.

FIGURE 6. Habitus. (a) Dorcadion a. axillar e, male and (b, c) females from Stara Zagora, (d) D. a. moldavicum, male and (e, f) females from Chirceşti, (g) D. a. moldavicum, male and (h) female from ‘ Valea lui David’. Endophalus. (i) D. a. axillare, (j) D. a. moldavicum. Arrow points to the small spine on the ventral side of the median tube.

FIGURE 7. Chromosomes of Dorcadion a. moldavicum. (a) female, Chirceşti, (b, c) females, ‘ Valea lui David’, (d) male, ‘ Valea lui David’, (e) prophase I, male, Chirceşti, and (f) ‘ Valea lui David’. (a, b, d, e, f) conventional staining, (c) C banding. Arrows point to the sex bivalent.

FIGURE 8. Ideogram of the haploid karyotype of Dorcadion a. moldavicum. Chirceşti (dark chromosomes), ‘ Valea lui David’ (grey chromosomes). Arrows show significant differences.

FIGURE 9. Distribution of Dorcadion axillare. (VD) ‘ Valea lui David’, (Mz) Mârzeşti, (Ch) Chirceşti, (Mc) Mäcin, (Bb) Babadag, (It) Istria, (Mg) Mangalia, (Hg) Hagieni, (Ot) Oltina, (EB) Esechioi and Bugeac, (VB) Valea Beiului. Black rectangles: D. a. moldavicum, black dots: D. a. axillare. The distribution in Bulgaria is based on the locality data published by Kantardjieva-Minkova (1934) and Minkova (1961), and on specimens in first author’s collection and public collections.

Tables

TABLE 2. Proportion of variance, eigenvalues and coefficients of the components of the Principal Component Analysis.

	Component 1	Component 2
variance (%)	67.72	18.95
eigenvalue	4.74	1.33
pL	0.96	0.04
pbW	0.87	-0.40
eL	0.96	0.09
eW	0.92	-0.34
bL	0.95	-0.008
pL/pbW	0.56	0.58
eL/eW	0.25	0.84

TABLE 3. Relative chromosome length, centromeric index and r (means ± SD) for two populations of Dorcadion axillare moldavicum. (*) indicates statistically significant differences, t - test, p <0.05.

1 2	‘Valea lui David’ (n=10) Relative length (%) CI ± SD 12.84 ± 0.65 - 11.34 ± 0.77 -	r ± SD - -	Chirceşti (n=10) Relative length (%) CI ± SD 12.92 ± 0.82 - 11.70 ± 0.67 -	r ± SD - -
3* 4*	9.32 ± 0.50 - 10.35 ± 0.57 34.93 ± 3.34	- 1.89 ± 0.28	10.36 ± 0.47 - 9.40 ± 0.47 26.58 ± 1.58	- 2.66 ± 0.36
5 6 7 8	10.54 ± 0.74 43.69 ± 2.53 8.16 ± 0.50 46.21 ± 2.64 7.57 ± 0.39 - 7.0 4 ± 0.71 29.83 ± 4.08	1.30 ± 0.14 1.17 ± 0.13 - 2.42 ± 0.53	11.05 ± 0.83 45.86 ± 1.63 8.21 ± 0.30 47.24 ± 1.55 7.30 ± 0.42 - 6.90 ± 0.35 29.99 ± 3.69	1.15 ± 0.15 1.06 ± 0.19 - 2.27 ± 0.60
9 10	6.77 ± 0.53 - 5.99 ± 0.34 -	- -	6.60 ± 0.43 - 5.82 ± 0.47 -	- -
11 X Y	5.43 ± 0.71 - 4.65 ± 0.87 - 1.46 (n=2) -	- - -	5.02 ± 0.54 - 4.71 ± 0.51 - 2.19 (n=2) -	- - -