Linnaemya bergstroemi, Pohjoismäki, Jaakko & Haarto, Antti, 2015

Pohjoismäki, Jaakko & Haarto, Antti, 2015, Linnaemya bergstroemi n. sp. (Diptera: Tachinidae) — a new parasitoid fly from the Finnish Lapland, Zootaxa 4059 (3), pp. 581-597 : 593-595

Distinction of Linnaemya bergstroemi n. sp. from the other species of Linnaemya

Although Linnaemya bergstroemi n. sp. is an unusual representative of the genus in the Palaearctic, four similarly dark species with irregular discal abdominal setae, Linnaemya anthracina ( Figs 2 , 7 , 13–14 , 23–24 , 34, 36 , 42, 43 ), L. varia ( Figs 3 , 8 , 15–16 , 25–26 , 32, 37 , 44 ), L. nigrescens ( Figs 4 , 9 , 17–18 , 27–28 , 38 , 45 ) and L. tessellata ( Figs 5 , 10 , 19–20 , 29–30 , 39 , 46 ), are known from the northern parts of North America. While these species have all been assigned to the subgenus Ophina Robineau-Desvoidy , L. anthracina differs considerably from the remaining three by its external characters. For example, L. nigrescens , L. tessellata and L. varia have prementum shorter than eye height, always 3+3 acrostichal setae, epandrium high, in lateral view more prominent than the surstylus, surstylus slender, truncate and shorter than syncercus, whereas L. anthracina (and L. bergstroemi n. sp.) has prementum longer than eye height, 3+1–3 acrostichal setae, epandrium flat, almost as high as surstylus, surstylus broad, pointed and longer than syncercus. The male L. anthracina specimen at BIO was originally misidentified as L. varia , as it has 3 post-sutural acrostichal setae on the thorax instead of 1 (see diagnosis in Brooks 1944). This confusion is also explained by the fact that L. anthracina , L. bergstroemi n. sp. and L. varia all have 3 dorsal preapical setae on all tibiae and commonly 4 katepisternal setae, character states not known in any other Linnaemya ( Brooks 1944; van Emden 1960; Mesnil 1971; Shima 1986). There are only two male L. anthracina specimens in CNC, one of which was examined from high resolution images to confirm the identity of the BIO specimen. The specimens are identical except for the CNC male having only 1 post-sutural acrostichal seta as indicated by Brooks (1944).

Despite their similarity, L. anthracina and L. bergstroemi n. sp. can be readily differentiated by a number of characters. The first flagellomere, which in both sexes of L. bergstroemi n. sp. is broad and rectangular ( Figs 11 , 21 ), is more elongated and rounded in L. anthracina ( Figs 13 , 23 ). Furthermore, the first flagellomere of L. bergstroemi n. sp. is scarcely longer than the pedicel while it is twice as long in L. anthracina . The male of L. bergstroemi n. sp. has a strong outer vertical seta, which is weaker, although present, in L. anthracina . The prementum in L. bergstroemi n. sp. is narrow and elongated, longer than the face in both sexes ( Figs 1 , 6 ), but is distinctly wider and shorter than the face in L. anthracina ( Figs 2 , 7 ). The female abdominal chaetotaxy in L. anthracina is markedly sparser than in L. bergstroemi n. sp., like for example the single pair of discal setae on tergite 4. This, however, might not be a stable feature, as chaetotaxy varies also between specimens of L. bergstroemi n. sp. In the female of L. anthracina the parafacial is covered with dense, silvery microtomentum and the wing veins are infuscated. The medial cleft of sternite 5 in L. bergstroemi n. sp. is U-shaped, whereas in L. anthracina it is V-shaped ( Figs 33–34 ). Other differences in the male genitalia are surprisingly small, the greatest being the shape of the dorsal part of the distiphallus and the relative length of the pregonites ( Figs 41–42 ), which are 1.7 times as long as their narrowest point in L. bergstroemi n. sp. compared to 3.0 times as long in L. anthracina . The basiphallus is also more rounded and distinctly wider in lateral view in L. bergstroemi n. sp.: 3.0 times as long as its narrowest point as opposed to 4.3 in L. anthracina ( Figs 41–43 ). The presence of a sclerotized ridge on the distiphallus separates L. anthracina and L. bergstroemi n. sp. from all the other members of the subgenus Ophina analyzed in this study ( Figs 44–48 ). However, a similar feature is present in L. tessellans of the subgenus Bonellimyia Townsend ( Fig. 49 ).

Linnaemya varia is readily distinguished from all the other Linnaemya species included in this study by its broad frons, which is wider than the eye width in both sexes ( Figs 16 , 26 ). Besides the color of the epistomeyellow in L. nigrescens —males of L. nigrescens and L. tessellata differ by the shape of the antenna, the first flagellomere of L. nigrescens being broadly rectangular ( Fig. 17 ) compared to cylindrical in L. tessellata ( Fig. 19 ). Additionally, the surstylus of L. tessellata is strikingly wide at its base ( Fig. 39 ) and the gonites are distinctive in all three species ( Figs 44–46 ). While L. nigrescens and L. tessellata males are easily identifiable, we are not confident in differentiating the females based on the material at hand. Based on this material, the two species also have an overlapping distribution in North America.

In the CoI sequence similarity analysis ( Fig. 55 ; Tab. 1 ), L. bergstroemi ’s closest match is L. anthracina , these two species being separated from each other by about a 1% sequence difference. Similar poor separation by CoI is evident also in L. nigrescens – rossica – tessellata – varia and some other Tachininae with a boreoalpine-arctic distribution, such as Peleteria aenea (Staeger) , P. prompta (Meigen) and P. rubescens (Robineau-Desvoidy) , as well as Nowickia alpina (Zetterstedt) and N. marklini (Zetterstedt) ( Fig. 55 ). As a note, the CoI tree does not represent a true phylogeny but helps to illustrate differences between taxa. For example, in our analyses Nowickia Wachtl is embedded within Tachina Meigen , whereas 12S and 16S sequences combined with morphological data place them as sister genera ( Novotná et al. 2009).

CoI is known not to work well in separating species in other brachyceran taxa and this could be due to a number of reasons ( Whitworth et al. 2007; Haarto & Ståhls 2014). Despite this shortcoming, the CoI comparison suggests that L. bergstroemi n. sp. and L. anthracina do not show any affinity to the known species in the subgenus Ophina . The same is suggested by features of the male genitalia, such as the size and shape of sternite 5 and epandrium, and the prominent sclerotized ridge on the distiphallus ( Figs 44–49 ). Although L. bergstroemi n. sp. and L. anthracina seem to share features with L. tessellans of the subgenus Bonellimyia , a more detailed phylogenetic analysis will be needed to solve their correct placement.

Figures

FIGURE 55. Neighbor-Joining tree of CoI sequences of selected Tachininae (see Tab. 1) based on Jukes-Cantor distances among sequences and rooted using an Exoristinae (Onychogonia cervini) as outgroup. Bootstrap confidence estimates are indicated on the nodes (values <70 % omitted). The arrow points to Linnaemya bergstroemi n. sp. In agreement with the phallic features, L. nigrescens, L. varia, L. rossica, L. tessellata, L. haemorrhoidalis and L. picta (all in the subgenus Ophina Robineau-Desvoidy) cluster together, whereas L. bergstroemi n. sp. and L. anthracina have a closer affinity to L. tessellans (subgenus Bonellimyia Townsend). Notice the poor separation of some northern Linnaemya Robineau-Desvoidy, Peleteria Robineau-Desvoidy and Nowickia Wachtl species. Tachina sp. nr. magnicornis is morphologically distinct from T. magnicornis but its identity is currently unclear (Novotná et al. 2009). The scale bar shows a 2 % sequence difference.

FIGURES 1 – 5. Linnaemya spp., male habitus in lateral view. Scale bars: 1 mm. 1. Linnaemya bergstroemi n. sp., holotype (Finland, Inari). 2. Linnaemya anthracina Thompson (Canada, Northwest Territories) (photo by J. E. O’Hara (CNC), used with permission). 3. Linnaemya varia Curran (Canada, Yukon). 4. Linnaemya nigrescens Curran (Canada, Yukon). 5. Linnaemya tessellata (Brooks) (Canada, Yukon).

FIGURES 6 – 10. Linnaemya spp., female habitus in lateral view. Scale bars: 1 mm. 6. Linnaemya bergstroemi n. sp., paratype (Finland, Inari). 7. Linnaemya anthracina Thompson (Canada, Alberta). 8. Linnaemya varia Curran (Canada, Yukon). 9. Linnaemya nigrescens Curran (Canada, Yukon). 10. Linnaemya tessellata (Brooks) (Canada, Quebec).

FIGURES 11 – 20. Heads of Linnaemya spp., males. Scale bars: 1 mm. 11 – 12. Linnaemya bergstroemi n. sp., holotype (Finland, Inari). 11. Lateral view. 12. Dorsal view. 13 – 14. Linnaemya anthracina Thompson (Canada, Alberta). 13. Lateral view. 14. Dorsal view. 15 – 16. Linnaemya varia Curran (Canada, Yukon). 15. Lateral view. 16. Dorsal view. 17 – 18. Linnaemya nigrescens Curran (Canada, Yukon). 17. Lateral view. 18. Dorsal view. 19 – 20. Linnaemya tessellata (Brooks) (Canada, Yukon). 19. Lateral view. 20. Dorsal view.

FIGURES 21 – 30. Heads of Linnaemya spp., females. Scale bars: 1 mm. 21 – 22. Linnaemya bergstroemi n. sp., paratype (Finland, Inari). 21. Lateral view. 22. Dorsal view. 23 – 24. Linnaemya anthracina Thompson (Canada, Alberta). 23. Lateral view. 24. Dorsal view. 25 – 26. Linnaemya varia Curran (Canada, Yukon). 25. Lateral view. 26. Dorsal view. 27 – 28. Linnaemya nigrescens Curran (Canada, Yukon). 27. Lateral view. 28. Dorsal view. 29 – 30. Linnaemya tessellata (Brooks) (Canada, Quebec). 29. Lateral view. 30. Dorsal view.

FIGURES 31 – 39. Linnaemya spp., males. Scale bars: 0.5 mm. 31. Linnaemya bergstroemi n. sp., holotype (Finland, Inari), undissected terminalia in left lateral view. The arrow shows the characteristically rounded projection on the posterior margin of sternite 5, a feature shared with Linnaemya anthracina Thompson. 32. Linnaemya varia Curran (Canada, Yukon), undissected terminalia in left lateral view. Notice the differences in the size and shape of the epandrium and convex posterior margin of sternite 5 as compared with L. bergstroemi n. sp. Both these features are in common with all other members of the subgenus Ophina Robineau-Desvoidy. 33 – 34. Sternite 5 in ventral view. 33. Linnaemya bergstroemi n. sp., paratype (Finland, Inari). The arrow points to the rounded projection on the posterior margin. 34. Linnaemya anthracina Thompson (Canada, Alberta). Notice the differences in the size and shape of the rounded projection on the posterior margin as well as in the shape of the median cleft of the sternite as compared with L. bergstroemi n. sp. 35 – 39. Syncercus and surstyli in dorsal (A) and lateral (B) views. 35. Linnaemya bergstroemi n. sp., paratype (Finland, Inari). 36. Linnaemya anthracina (Canada, Alberta). 37. Linnaemya varia Curran (Canada, Northwest Territories). 38. Linnaemya nigrescens Curran (Canada, Nova Scotia). 39. Linnaemya tessellata (Brooks) (Canada, Yukon).

FIGURES 40 – 49. Linnaemya spp., structures of the male terminalia in lateral view. Scale bars: 0.5 mm. Abbreviations: aed apod = aedeagal apodeme; bph = basiphallus; da-ds = dorsoapical surface of distiphallus; ds = distiphallus; ej apod = ejaculatory apodeme; epiph = epiphallus; pog = postgonite; prg = pregonite; sc = sclerotized ridge. 40. Generalized view of the Linnaemya anthracina Thompson (Canada, Alberta) phallus with gonites attached. The epiphallus is partially covered by the postgonite. 41. Linnaemya bergstroemi n. sp., paratype (Finland, Inari). Gonites separated from the phallus. 42. Linnaemya anthracina (Canada, Alberta). Gonites separated from the phallus. Notice the difference in the relative dimensions of the pregonite as compared with L. bergstroemi n. sp. 43. Basiphalli of L. bergstroemi n. sp. and L. anthracina. 44. Linnaemya varia Curran (Canada, Yukon). 45. Linnaemya nigrescens Curran (Canada, Nova Scotia). 46. Linnaemya tessellata (Brooks) (Canada, Yukon). 47. Linnaemya picta (Meigen) (type species of the subgenus Ophina Robineau-Desvoidy) (Germany, Hessen). 48. Linnaemya rossica Zimin (Finland, North Karelia). 49. Linnaemya tessellans (Robineau-Desvoidy) (subgenus Bonellimyia Townsend) (Germany, Hessen). Notice the sclerotized ridge on the distiphallus.