Tragosoma harrisii LeConte, 1851

Laplante, Serge, 2017, Description of a new Nearctic species of Tragosoma Audinet-Serville (Coleoptera: Cerambycidae: Prioninae), with species validations, new synonymies and a lectotype designation, Insecta Mundi 2017 (578), pp. 1-17 : 7

Tragosoma harrisii LeConte, 1851

Laplante (2010: 42) stated that none of the North American taxa previously considered as synonyms of Tragosoma depsarium ( Linnaeus, 1767) were conspecific with it and that the latter was exclusively Palaearctic in distribution. It could therefore be inferred that T. harrisii LeConte, 1851 , the oldest name available in the list of synonyms of T. depsarium , was implicitly the valid name for the most widespread North American species. The reinstatement of T. harrisii , revised status, as a valid species is formally proposed here. I have not studied the type of Cerambyx depsarius but examined the four photographs of a syntype, a female, in the Linnean Society insect database ( Linnean Society of London 2017). Since the type matches the female specimens of T. depsarium studied, I assumed that it is conspecific with the only species known from the Palaearctic zone and so based my concept of that species on the 124 Eurasian specimens examined. I have also not seen types of T. harrisii , but I examined photographs of a syntype in the MCZ Type Database ( Museum of Comparative Zoology 2010); the images clearly show a female specimen on which the features of the pronotum and antennomere 3 confirm that the numerous eastern specimens of Tragosoma I examined are conspecific with it. Furthermore, considering its type locality (“Newfoundland; Connecticut”), I concluded that LeConte’s type is conspecific with the only species of Tragosoma known from northeastern North America. The main differences between the two species are as follows. Males of T. harrisii have the pronotal hypomeron rough, covered with contiguous punctures all over ( Fig. 7 ); males of T. depsarium have the pronotal hypomeron mainly smooth, showing at most few scattered variably coarse punctures anterior to the lateral spine ( Fig. 8 ). Males of T. harrisii also have the medioanterior part of the prosternum distinctly less convex than in T. depsarium . Females of T. harrisii have the middle of the prosternum rugose with a rather dense punctation; females of T. depsarium have the middle of the prosternum smooth between the rather sparse punctures. The difference of the two species was confirmed in a genetic distance analysis performed with full-length barcodes of nine T. harrisii included in the dataset (from New Brunswick [1], Ontario [1], Manitoba [1], Alberta [5] and British Columbia [1]) and one T. depsarium (from Bavaria, Germany). The specimens of T. harrisii clustered congruently with an intraspecific variation ranging from 0.15–1.70% (mean = 0.72%) and the interspecific variation between them and the specimen of T. depsarium ranged from 12.25–12.81% (mean = 12.49%) ( Fig. 11 ).

I observed much morphological variation among specimens of T. harrisii , especially in the shape of the median prothoracic process. The surface covered by the poriferous area on the dorsal face of the antennomere 3 also tends to be larger in western specimens, particularly in the southwest. The genetic distance of 1.70% observed between the barcodes of some specimens of T. harrisii included in the dataset reflects that intraspecific variation ( Fig. 11 ). Furthermore, when the barcode of one more T. harrisii excluded from the dataset was included in an analysis of the genetic distances with the nine T. harrisii of the dataset, the intraspecific variation obtained between the 10 specimens was 0.15–3.62% (mean = 1.21%), and the distance between the added specimen and the nine others, 2.81–3.62% (mean = 3.15%). This is an indication that, as presently conceived, T. harrisii may be a complex of closely related species and the specimen excluded from the dataset could be a distinct species. Study of more specimens is needed to confirm that hypothesis and eventually resolve the taxonomy of that complex. Tragosoma harrisii , as variable as it may be, shows marked morphological similarities with T. depsarium and T. nigripenne , and together they constitute what I recognize as the depsarium group.

Figures

Figure 11. Neighbor joining tree for the 16 barcodes of Tragosoma included in the dataset; each record with province or state of origin, GenBank accession number, and sample ID. Full length sequences (658 base pairs) analyzed, unless otherwise indicated in parentheses.

Figures 7–8. Left pronotal hypomeron of male Tragosoma in ventrolateral view. 7) T. harrisii. 8) T. depsarium.