Abstract. Status of Ampedus auripes (Reitter, 1895) was long considered to be controversial. Only relatively few specimens were known in total. Based on 363 individuals of the species from the Bavarian Forest, the most important characters described in the literature were checked. Additionally, further morphological characters validating the separation of Ampedus auripes from Ampedus nigrinus (Herbst, 1784) were discovered: venation of the metathoracic wings, shape of the lateral edge of pronotum and the appearance of ventral vestiture. 14 of the specimens studied could not be identified as belonging to either of these two species. The morphological characters of these possible “hybrids” are herein illustrated and described.
Zusammenfassung.Ampedus auripes (Reitter, 1895) galt lange Zeit als umstrittene Art. Insgesamt waren nur relativ wenige Exemplare bekannt. Auf der Basis von 363 Individuen der Art aus dem Bayerischen Wald wurden die wichtigsten in der Literatur beschriebenen Merkmale überprüft. Zusätzlich wurden als weitere morphologische Merkmale die Hautflügel, der Halsschildseitenrand und die ventrale Behaarung für die Unterscheidung von Ampedus auripes und Ampedus nigrinus (Herbst, 1784) ergänzt. 14 der untersuchten Individuen konnten nicht eindeutig einer der beiden Arten zugeordnet werden. Die morphologischen Merkmale dieser möglichen „Hybriden“ werden dargestellt und beschrieben.
Until recently (Wurst & Kaupp, 1995), Ampedus auripes (Reitter, 1895) was considered to fall within the range of variation of Ampedus nigrinus (Herbst, 1784). Following the comparison of material from various collections, A. auripes was once more accorded the status of a valid species by Wurst & Kaupp (1995), who also summarized constant characters for the reliable separation of the two species. Their study was, however, based on a restricted number of individuals, which hindered interpretation of the identification characters. In the course of a research project undertaken by the staff of the Bavarian Forest National Park, 363 individuals of A. auripes were collected. Never before has this much-discussed species been found in such numbers. Objective of this study is to check and augment the previously known most important characters of A. auripes, using the extensive material and data from the Bavarian Forest, as well as to document the characters of the possible “hybrids”.
Study area and methods
The study area in the Bavarian Forest reaches from 650 m to 1420 m a.s.l.. A detailed description is given in Bässler et al. (2008). To ensure a standardized survey of the arthropod fauna along the altitudinal gradient, four transects were established at different heights and in different areas (Lackenberg, Rachel, Plattenhauser). Insects were sampled with window eclectors placed every 100 m along the transects, with Malaise traps placed on specially selected sections: in total 181 window eclectors and 36 Malaise traps were used. These sampling methods were supplemented by hand collecting on logs and snags. Sampling period was from May to October 2007. With all sampling methods, 363 individuals of A. auripes and 329 individuals of A. nigrinus were recorded. Of these, 357 specimens of A. auripes and 329 specimens of A. nigrinus were caught with eclectors. Only six A. auripes und 26 A. nigrinus were caught with Malaise traps. Hand collecting yielded no A. auripes, but it provided eight A. nigrinus. 14 of the sampled specimens could not be clearly identified as A. auripes or A. nigrinus. These possibly hybrid specimens are discussed further in section „Hybrid“. Comparison of sampling methods shows that flight window traps are a very effective method for recording the high montane click beetles.
Results and discussion of morphological characters of Ampedus auripes (Reitter) in comparison with Ampedus nigrinus (Herbst)
Body size. Measurements of 302 individuals of Ampedus auripes yielded a body size ranging from 7.50 to 10.00 mm (median 8.90 mm) for females (n=104) and 7.10 to 9.50 mm (median 8.20 mm) for males (n=198). A range in size from 7.10 to 10.00 mm results for all individuals (Fig. 1). Reitter (1895, 1918) and Kuhnt (1911) give a length of 9.50 mm. Whilst Laibner (2000) measured lengths from 8.00 to 9.50 mm, the range in Wurst & Kaupp (1995) lies between 9.50 and 10.50 mm. Collating all these results, a body size of 7.10 to 10.50 mm can be established.
Measurements of A. nigrinus were not made, because sufficient data for this species were already available. The body size lies between 6.00 and 9.00 mm (Reitter (1911, 1918), Kuhnt (1911), Leseigneur (1972), Freude et al. (1979), Gurjeva (1979), Dolin (1988), Platia (1994), Laibner (2000)).
Fig. 1. Histogram of the distribution of body sizes of both sexes of Ampedus auripes (Reitter) n=302
Histogramm über die Körpergrößenverteilung der beiden Geschlechter von A. auripes (Reitter) n=302
Body shape and appearance. The parallel-sided body shape of Ampedus auripes, described amongst others by Reitter (1895, 1911, 1918), Kuhnt (1911), Wurst (1992) and Wurst & Kaupp (1995), has proved to be a constant character. The narrowing of the elytra begins approximately in the posterior third, whilst in A. nigrinus this starts at about the middle (Figs. 2-5). Identification of females of A. auripes was difficult in some cases, because females of A. nigrinus are often very large and tend to have a parallel-sided body. Therefore it was especially important to check all the morphological characters of large female specimens of the above-mentioned species.
The reddish brown legs and deeply incised elytral grooves of Ampedus auripes are also mentioned by many authors as good distinguishing characters (Reitter (1895, 1911, 1918), Kuhnt (1911), Wurst (1992), Wurst & Kaupp (1995), Laibner (2000)). The latter character is often more pronounced in female than in male. Both characters are, however, hardly helpful for determination, because of their variable degree of expression.
Sclerotization of the radio-medial (r-m) crossvein of the hind metathoracic wings as an identification character. The sclerotization of the membranous hind metathoracic wings plays an important role in the identification of Diptera, Hymenoptera and other insects. In the Coleoptera, Elateridae in particular, this character has scarcely been used, with the exception of the work of Tarnawski (2000), who used it to identify genera. In the examination of over 300 individuals of Ampedus auripes and at least as many A. nigrinus, the hind metathoracic wings of each specimen were prepared. It was found that in 92% of A. auripes specimens, that the radio-medial (r-m) crossvein (Fig. 6, 8) is weakly or very weakly sclerotized. This applies to both sexes of this species. In the remaining 8% this character is not so clear. In every case, the sclerotization of the radio-medial (r-m) crossvein in A. nigrinus is strongly or very strongly developed (Fig. 7, 9). This character proved to be very helpful in the determination of A. auripes in other projects undertaken by the Bavarian and Czech National Parks.
Vestiture of the ventral parts of the body. Reitter (1895, 1911) described the body of Ampedus auripes as shining, completely covered with fine, black, slightly upstanding pubescence. Laibner (2000) likewise mentioned black pubescence, which may sometimes be brown ventrally.
Wurst & Kaupp (1995), according to their morphological investigations, regard the predominantly black pubescence of the venter as a character that is not very constant.
In the present study, we confirm that hardly any specimens were found to possess predominantly black pubescence on the underside. However, vestiture of the two species was nevertheless very different: whilst Ampedus auripes has mainly red-brown pubescence on the ventral part of body (Fig. 10), A. nigrinus is immediately recognizable by its dense, golden-yellow pubescence (Fig. 11). Because of its sparse pubescence, A. auripes appears shiny in comparison to A. nigrinus (Fig. 10).
As shown in Figs. 10 and 11, pubescence on the ventral part of the body can certainly be used for identification. (Specimens in alcohol should, however, be dried thoroughly before identification, so that the setae are well visible!)
Pronotum. The shape of pronotum is one of the most important characters for the distinction of Ampedus auripes from A. nigrinus. Whilst that of the female of A. nigrinus is narrowing anteriorly at a acute angle (Fig. 13), that of the female of A. auripes is narrowing anteriorly at a obtuse angle, and is less broad than long (Fig. 12). This is also mentioned by Reitter (1895) in his original description.
All male specimens of Ampedus auripes exhibit a roughly trapezoid pronotum, narrowing in a straight line towards the front (Fig.14). The pronotum of A. nigrinus is narrowing towards the front, but with a curved outline (Fig.15). Wurst (1992), Wurst & Kaupp (1995) and Laibner (2000) also described this character as being different between the two species. The shape of the lateral edge of pronotum can be clearly observed from lateral view: whilst the lateral edge in the male of A. auripes runs straight along the underside (Fig. 16), it is arched in A. nigrinus (Fig. 17).
he flattened pronotum of A. auripes, as described by Laibner (2000), was also clearly observed in the specimens from the Bavarian Forest (Fig. 16). However, a direct comparison with A. nigrinus is necessary to appreciate this (Fig. 17).
The outline of the lateral edge of pronotum in the female does not show such clear differences between the species as in the males. In females of Ampedus auripes and A. nigrinus the edge is weakly curved (Fig. 18, 19). Identification of females using this character is therefore not recommended. On the other hand, females of A. auripes (Fig. 18) exhibit flattened pronotum, which is convex in A. nigrinus (Fig. 19).
Both sexes of Ampedus auripes show a more or less clearly visible median furrow on the basal part of pronotum, whilst A. nigrinus may sometimes have a shallow longitudinal impression on pronotum (Wurst & Kaupp 1995) (see also Fig. 13).
Shape of pronotum proved to be a quick and reliable identification character. In the possibly hybrid specimens, the shape of pronotum did not allow definite placement of the specimens (see results “Hybrid”).
The femoral plate. Wurst and Kaupp (1995) described the excised femoral plates of the hind legs of Ampedus auripes for the first time. This character has proved to be very helpful during the determination of more than 300 specimens. However, the development of this excision in the male is extremely variable. Some specimens possessed very deep, others more shallow excisions. Fig. 20 (a) shows a specimen with strongly excised femoral plates. In the female of A. auripes, the femoral plates are only weakly excised, and may thus be confused with the female of A. nigrinus. In the latter species the femoral plates may have entire margins (Wurst & Kaupp, 1995) or be slightly excised (Fig. 21 (b)).
Fig. 20. Femoral plates of male Ampedus auripes (Reitter). a = +/- deep excision of inner margin
Schenkeldecken eines Männchens von Ampedus auripes (Reitter). a= +/- tiefer Einschnitt des Innenrands
Fig. 21. Femoral plates of male Ampedus nigrinus (Herbst). a = excision of inner margin absent or very shallow Schenkeldecken eines Männchens von Ampedus nigrinus (Herbst). b= kein bzw. flacher Einschnitt des Innenrands
“Hybrid” between Ampedus auripes (Reitter) and Ampedus nigrinus (Herbst)
As we already mentioned, we were not able to place 14 individuals as definitely belonging to one or the other of the two species using morphological characters. Study of their alae revealed that additional (“new”) fragments of veins were present in 11 of these specimens (Fig. 24-26, 28-30), which do not occur in the ground plan of the genus Ampedus Dejean, 1833 (Fig. 27). Reasons for this may be a modification (non hereditary change caused by external factors), or the activation of a basal (primitive) gene caused by the hybridization of the two species. Tarnawski (2000) outlined the phylogeny of Elateridae (Fig. 22), that implies the subfamily Elaterinae descended from the Cardiophorinae. Viewing the metathoracic wing of a “hybrid” (Fig. 24), a similarity with that of the genus Cardiophorus Eschscholtz, 1829 (Fig. 23) can be observed: the fork of A1 (anal vein) (Fig. 23) in Cardiophorus spec. is also weakly visible as in three “hybrid specimens” (Fig. 24, 25, 26).
Further investigation revealed an anteriorly shortened margin of the lateral pronotal edge in three individuals (Fig. 36), similar to that which can be found in Cardiophorinae. (Both sides of pronotum need to be inspected, since development may differ even between them.) One can thus postulate that plesiomorphic (primitive) characters are activated by the hybridization of the two species. This must, however, not necessarily result from hybridization. To verify the hypothesis, breeding experiments must be undertaken (Ampedus auripes female with A. nigrinus male and the reverse). Until then, the existence of “hybrids” remains only a conjecture.
Fig. 23. Sketch of a metathoracic wing of the genus Cardiophorus Eschscholtz (from Tarnawski, 2000).
Skizzter Hautflügel der Gattung Cardiophorus Eschscholtz (aus Tarnawski, 2000).
Fig. 36. Lateral view of pronotum of a male „hybrid“ with shortened lateral margin (arrowed)
Seitenansicht des Halsschildes eines männlichen „Hybriden“ mit verkürzter Seitenlinie (s. Pfeil)
We owe our thanks to Claus Wurst (Heilbronn, Germany) for checking the determination of the first specimens of A. auripes, Nikola Rahmé (Budapest, Hungary) for the photographs of beetles, as well as Andrew Liston (Müncheberg, Germany) for translating this work into English. Tomáš Lackner (Sapporo, Japan) is being thanked for improvement of the manuscript.
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