Research Article |
Corresponding author: Christophe J. Praz ( christophe.praz@unine.ch ) Academic editor: Jack Neff
© 2023 Christophe J. Praz, Dimitri Bénon.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Praz CJ, Bénon D (2023) Revision of the leachella group of Megachile subgenus Eutricharaea in the Western Palaearctic (Hymenoptera, Apoidea, Megachilidae): A renewed plea for DNA barcoding type material. Journal of Hymenoptera Research 95: 143-198. https://doi.org/10.3897/jhr.95.96796
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The leafcutting bees of the leachella group of Megachile Latreille subgenus Eutricharaea Thomson are revised for the Western Palaearctic region using a combination of morphology and phylogenetic analyses of three genes (COI, LW-Rhodopsin, CAD). Although only seven species are recognized, much effort was needed to link delimitated taxonomic units to taxon names because of the difficulties in identifying type specimens. Numerous types were in a poor state of conservation, preventing straight-forward identification using morphology. This was in some cases aggravated by the fact that they often belonged to a sex that could not easily be identified; one type was a gynandromorph specimen whose identification is even more challenging. In several cases, the type locality was vague or unclear; in three cases, the type specimens originated from introduced populations for which the source of the introduction needed to be determined using DNA barcoding. In two cases, the type specimens consisted of several body parts not originating from a single individual but from two heterospecific specimens. We argue that this tedious nomenclatural work would have been greatly facilitated if a reference library of type specimens had been available. Our revision leads to the following taxonomic changes. Megachile argentata (Fabricius, 1793), described from northern Africa and with a convoluted taxonomic history, is demonstrated, based on morphometric analyses of its lectotype, to be conspecific with the species hitherto known as M. pilidens Alfken, 1924. After discussing and excluding several alternative options that would minimize nomenclatural changes, we place M. pilidens in synonymy with M. argentata (syn. nov.). Two new subspecies are described for morphologically slightly divergent insular populations, M. leachella cretica Praz, ssp. nov. from Crete, and M. leachella densipunctata Praz, ssp. nov. from Cyprus. In addition, M. albipila Pérez, 1895 is treated as a subspecies of M. leachella Curtis, 1828 (stat. nov.). The following new synonymies are proposed: M. compacta Pérez, 1895 (not M. compacta Smith, 1879) and the replacement name M. crassula Pérez, 1896, M. argyrea Cockerell, 1931 and Perezia maura Ferton, 1914, are placed in synonymy with M. argentata (syn. nov.). M. beaumonti Benoist, 1951, is newly treated as a valid species (stat. rev.). M. schmiedeknechti Costa, 1884 is treated as a subspecies of M. argentata (stat. nov.), and M. xanthopyga Pérez, 1895 is placed in synonymy with M. argentata schmiedeknechti (syn. nov.). M. bioculata Pérez, 1902, M. discriminata Rebmann, 1968 and M. ichnusae Rebmann, 1968 are placed in synonymy with M. leachella (syn. nov.). M. variscopa Pérez, 1895, M. timberlakei Cockerell, 1920, M. atratula Rebmann, 1968, M. striatella Rebmann, 1968 and M. sudai Ikudome, 1999 are placed in synonymy with M. pusilla Pérez, 1894. Lectotypes are designated for M. albipila, M. bioculata, M. compacta Pérez, M. pusilla, M. variscopa and M. xanthopyga.
DNA barcoding, morphometry, speciation, species delimitation, subspecies
The subgenus Eutricharaea Thomson, 1872 of the genus Megachile Latreille, 1802 (Hymenoptera: Megachilidae) is taxonomically difficult: it includes numerous species with rather homogeneous morphology, leading to challenging identifications and intricate species boundaries. In addition, in the absence of proper examination of their type material, the status of several taxa remains unclear. The subgenus is native to the Eastern Hemisphere but has been introduced both accidentally (Megachile apicalis Spinola, 1808, M. pusilla Pérez, 1884, M. concinna Smith, 1879) and intentionally [M. rotundata (Fabricius, 1793)] into the Western Hemisphere. The latter species was introduced into North America and is reared commercially for the pollination of alfalfa (Medicago sp.) (
In the Palaearctic no comprehensive revision is available for this subgenus. Otto Rebmann described several species and presented identifications keys for some species groups (Rebmann 1967–1970), but he did so without a full revision of the type material. Species of Eutricharaea fall into several species groups segregated based on male genitalia, mainly the rotundata group [sometimes referred to as a distinct subgenus, Neoeutricharaea Rebmann, 1967; see
The leachella group includes two widely distributed species in the Palaearctic, M. pilidens Alfken, 1924 and M. leachella Curtis, 1828, which are the only species present in Central Europe (
In the present study, we use a combination of genetic analyses and morphology to delimitate the species of the leachella group of the Western Palaearctic, and examine most type specimens to present a comprehensive revision of this challenging group of bees.
The 658-bp fragment of the mitochondrial gene Cytochrome Oxidase I (DNA barcoding fragment; hereafter COI) was generated using the primers LepF and LepR or, if this primer pair did not yield amplicons or high-quality sequences, the alternate forward primer UAE3. Primer sequences and lab protocols are given in
We used our genetic analyses as a complement to morphology for species delimitation. We also used DNA barcodes for the identification of female specimens, which are often challenging to identify in the leachella group. For species delimitation, particular attention was given to the structure of male genitalia. The morphology of male sterna, the colour of front tarsi and the shape of a tooth on the gena just behind the base of the mandible were also important characters. In females, sculptural differences were primarily used for species delimitation, in particular the punctation of the terga (especially the disc of T4) and of the vertex, the length of the ocelloccipital distance and the shape of the apical clypeal margin. Vestiture colour was given low priority for species delimitation given the known variation in this character, even if vestiture colour is useful for identification if geographic variation is considered. We recognize subspecies in a few cases for geographically well-separated, allopatric forms diverging from conspecific forms by either a single significant morphological feature, or by a small number of unsignificant features, taking into account the molecular results. A significant morphological feature corresponds to morphological differences typically observed between species in the subgenus Eutricharaea; examples include significant and discriminating differences in tergal punctation, the length of the ocelloccipital distance, or differences in the structure of the genital capsule. Unsignificant features include weak differences in punctation, differences in vestiture colour, or differences in integument colour. Taxa presenting a broad morphological cline (that is, intergradation of morphological features over a large geographic distance, typically over 100 km or so) were not separated as distinct subspecies. A rationale for recognizing subspecies is presented in each case. Overall, we favor a broad species concept, where geographically isolated forms are preferably treated as subspecies rather than split as distinct species.
Morphology follows
The females in the leachella group are notoriously difficult to identify, particularly in northwestern Africa, where four species occur, all of which exhibit snow white vestiture, unlike in southern Europe where vestiture colour can be used to separate at least M. pilidens from M. leachella, M. anatolica and M. pusilla. The lectotype of M. argentata (Figs
Vertex of the lectotype female of Megachile argentata (Fabricius, 1793), showing the ocelloccipital distance OOD (yellow line), two tangentials placed behind the lateral ocellus and along the inner margin of the compound eye (red lines), and the white rectangle with dimensions 1.1× OOD × 0.55× OOD within which the punctures were measured in our morphometric analyses.
Once the scale was set, we first rotated, if necessary, each picture so that the two lateral ocelli would form a horizontal line. We measured the ocelloccipital distance (OOD), defined as the shortest distance between the posterior margin of the left ocellus (including the black, shiny, circular margin of the ocellus) and the occipital ridge (Fig.
Material from the following institutions has been examined. The type material has been examined by one of us (CP), and the distribution given for each species is based on material examined by CP.
CPCN Collection of Christophe Praz, University of Neuchatel, Neuchatel, Switzerland.
CSE Collection of Christian Schmid-Egger, Berlin, Germany.
ETHZ Entomological Collection of ETH Zurich, Zurich, Switzerland.
MZL Musée cantonal de zoologie, Lausanne, Switzerland.
NHMD Natural History Museum of Denmark, Copenhagen, Denmark.
NMB Naturhistorisches Museum, Basel, Switzerland.
OUMNH University Museum of Natural History, Oxford, UK.
SMFD Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt am Main, Germany.
Identification of type specimens was performed after species delimitation had been done using combined molecular and morphological data (see below) but is presented first to settle the names of the different taxa before discussing their morphology and phylogenetic relationships.
Megachile argentata was described from “Barbaria”, a region corresponding to the coastal area of northern Africa from Algeria to Libya. The specimens available to Fabricius were collected by R. L. Desfontaines, probably in modern Tunisia or eastern Algeria [“régences de Tunis et d’Alger” (Beylik of Tunis and Ottoman Algeria); Dureau de la Malle 1838]. Depending on the author, this name was used until 1968 for one of the species currently known as M. leachella or M. pilidens, or for both. In early works these two species were probably lumped under M. argentata (e. g.
Also aware of the presence of two distinct species in this group,
Unfortunately, although Alfken clearly differentiated these two widespread European species, he did not examine the type specimen of M. argentata.
We have examined the lectotype female of M. argentata (Figs
The separation of the females of these three taxa can be difficult: unlike in central and northern Europe, the vestiture of both M. leachella and M. pilidens is snow-white in northern African populations, just as in M. inexspectata. Moreover, the differences in the punctation of the disc of the terga, especially T4, between M. leachella and M. pilidens appear to be less pronounced in northwestern Africa than in Europe, where this characteristic mostly (but not always) allows for the separation of both species (
Comparison of the females of Megachile inexspectata, M. leachella albipila and M. argentata in northwestern Africa.
Characters | Megachile inexspectata | Megachile leachella albipila | Megachile argentata |
---|---|---|---|
Vestiture | |||
Vestiture of dorsal side of scutum | Entirely consisting of white hairs; short scale hairs present over entire disc of scutum (Fig. |
As in M. inexspectata | scutum covered with intermixed light and dark hairs; short scale-like hairs mosty present anteriorly and posteriorly, less abundant on central parts of disc of scutum |
Lateral hairs on terga | Dark, erect hairs restricted to lateral parts of T6, sometimes T5 (Fig. |
As in M. inexspectata (Fig. |
Dark, erect hairs present laterally on T3-T6 (Fig. |
Light hairs on disc of T6 | Sometimes forming one large spot of hairs (Fig. |
Mostly forming two separated spots of hairs | always forming two well-separated spots of hairs (Fig. |
Sculpture | |||
Punctation of vertex | Dense, punctures small (diameter on average 40 μm) (Fig. |
As in M. inexspectata, puncture diameters 35–40 μm, punctation slightly less dense, often with shagreened interspaces (Fig. |
Punctures larger (on average 50 μm), punctation less dense, interspaces up to one puncture diameter, surface of interspaces smooth (Figs |
Punctation of disc of T4 | Dense, interspaces mostly smaller than one puncture diameter (Fig. |
Mostly sparse, interspaces mostly larger than one puncture diameter (Fig. |
Dense, interspaces smaller than one puncture diameter (Fig. |
This identification is confirmed by our measurements of the OOD and of the size of the punctures on the vertex (Figs
Results of the morphometric analyses of female specimens of Megachile argentata (red circles), M. inexspectata (yellow) and M. leachella (blue); three measurements of the lectotype of M. argentata are shown as open red circles; relationship between the ocelloccipital distance and the average diameter of the punctures included in the white rectangle of Fig.
In summary, the identity of the lectotype designated by
The first option would be to follow
Two additional aspects need to be discussed. First, given that the lectotype of M. argentata originates from an undersampled geographic region (Algeria and Tunisa), could it belong to an additional, hitherto unknown taxon? We consider this possibility as very unlikely. In contrast to other groups of bees, such as osmiine (e.g.,
Second, there are minimal morphological differences between northwestern African populations of “M. pilidens” (in the following paragraph “argentata”), and other western Palaearctic populations of this taxon (“pilidens”): vestiture is snow white in “argentata” (Fig.
Based on the evidence assembled here, we thus place M. pilidens in synonymy with M. argentata (syn. nov.).
Megachile inexspectata was described from a single male specimen collected in Mut, Turkey in 1965 by Maximilian Schwarz. The holotype is in poor condition, probably because it has been relaxed for the preparation of the genitalia. It is labeled as follows (here and throughout the paper, the order of labels starts with the label closest to the body): 1. [a cardboard piece to which the genitalia and a T7 are glued]; 2. “Türkei Mut 12.VI.1965 leg. M. Schwarz”. 3. [A yellow label with number 27, handwritten]. 4. “inexspectata n. sp. ♂ det. Dr Rebmann 1966”. 5. “Typus” [printed on red paper, with SMFH 1866, handwritten on the reverse side]. 6. Senckenberg-Museum Frankfurt/Main. 7. “Megachile walkeri ♂? D. B. Baker det. 1990”. The examination of the holotype reveals the following issue. The nearly entire metasoma, including T7, is still attached to the pinned specimen. The genitalia have been extracted and are glued on a piece of cardboard attached to the same pin (Fig.
The holotype of M. striatella Rebmann, 1968, also in poor condition, is labeled as follows: 1. a cardboard with the genitalia glued; 2. “El Kantara [Algeria], 7. Juli 1904, Dr. Gulde”. 3. Typus [printed on red paper]; SMF H 1593 [written on reverse side of label]. 4. Megachile concinna D. B. Baker det. 1990. 5. Senckenberg Museum Frankfurt am Main. Examination of this specimen reveals that the body of the holotype is most probably M. inexspectata, as indicated by the lack of tooth behind the mandibular base and the conspicuous patch of yellow hairs medially on S4 (cf. Fig.
Rebmann relaxed his specimens during 24 hours for the preparation of the hidden sterna (
Assuming that our hypothesis is correct, we are left with the following two possibilities to resolve this confused taxonomic situation. The first possibility would be to submit a request to the International Commission on Zoological Nomenclature to discard current holotypes and to designate neotypes for both taxa. The second possibility is to invoke article 73.1.5 of the code, which states that “if a subsequent author finds that a holotype which consists of a set of components (e.g. disarticulated body parts) is not derived from an individual animal, the extraneous components may, by appropriate citation, be excluded from the holotype”. Following this last approach, we assume that the genitalia (but not the body) of the specimens originate from the correct location (Mut, Turkey for the genitalia of the holotype of M. inexspectata and Kantara, Algeria for the genitalia of the holotype of M. striatella), exclude the body of these two specimens from the holotype, and declare that only the genitalia serve as name-bearing types for these two taxa. Based on current knowledge of this group of bees in Turkey and Algeria, only M. inexspectata (see
The labelling of the taxa in the tree is done in anticipation of our final delimitation and taxonomic decisions. For clarity, specimens of M. argentata from outside of northwestern Africa are labeled as “pilidens”, those from Sardinia and Malta as M. schmiedeknechti. The phylogenetic tree (Fig.
Within-species distances in the taxa of the concinna complex have been presented elsewhere (
By contrast, within-species genetic distances were considerable in M. leachella. First, two specimens from Crete (treated here as a new subspecies, M. leachella cretica ssp. nov.) were divergent and formed a well-supported clade that was sister to all other specimens of M. leachella (Fig.
Within M. argentata, within-species genetic distances were small (max: 0.5%). Three specimens from northwestern Africa were weakly divergent from all other specimens (average genetic distances 0.2%; minimum 0.2, maximum 0.5%). Two specimens from Sardinia, attributed to the subspecies M. argentata schmiedeknechti, were only weakly separated from all other specimens (average genetic distances 0.2%; minimum 0.2, maximum 0.5%). One specimen from Malta, attributed to M. argentata schmiedeknechti, had identical sequence with several specimens from central Europe (Fig.
Single genes phylogenies based on opsin and CAD (data not shown) were little resolved, but all species were recovered as monophyletic groups, except as follows: Megachile pusilla did not form a monophyletic group in analyses of opsin, and M. leucostoma in analyses of CAD; in analyses of opsin, some populations of M. leachella shared an allele with M. anatolica and M. viridicollis (see
Best tree found in maximum likelihood analyses of sequence data of the two nuclear genes lw rhodopsin and CAD showing the phylogenetic relationships among the Palaearctic species of the leachella group of Megachile (Eutricharaea). Bootstrap support values are based on 1000 bootstrap replicates. The oblique line along the branch joining the outgroup taxa and the ingroup indicates that this branch has been shortened for better graphic representation.
Within M. argentata, the only sequenced specimen from northwestern Africa was sister to all other specimens; both specimens from Sardinia (M. argentata schmiedeknechti) were weakly divergent from two specimens from Greece and Switzerland.
This species is sculpturally very uniform throughout its range. The colour of the vestiture is however variable geographically. As discussed above, the populations from northwestern Africa (Fig.
The vestiture is red-orange on the Islands of Malta (Fig.
Contrasting the current view, we propose to treat M. schmiedeknechti as a subspecies of M. argentata, for the following reasons. First, only vestiture colour appears to separate it from continental (including northwestern African) populations, and no sculptural difference, except that tergal punctation in both sexes is finer and denser in M. schmiedeknechti, especially in the female; as discussed above, vestiture colour is variable in the leachella group and in bees in general. Second, DNA barcodes are shared or very similar between continental and insular forms (Fig.
We recognize M. schmiedeknechti as a valid subspecies of M. argentata and propose the following new combination: Megachile argentata schmiedkechti, stat. nov. This subspecies is morphologically well characterized, geographically well-delimitated and no intermediate form is known to exist (except for the populations found on the Island of Karpathos, which are not located near the contact zone between M. argentata schmiedeknechti and the continental form). The main argument for treating this insular form as a subspecies and not simply as a geographic form is the abrupt contact zone with no transitional populations between Malta and the Italian mainland. Such an abrupt transition may be indicative of some reproduction interference between both forms, and suggests that the recognition of schmiedeknechti as a distinct conservation unit is meaningful. We do not recognize a distinct subspecies for the populations of Karpathos because the phenotypic differentiation of these populations with respect to those found in mainland Greece is weak. Our treatment of the Maltese populations as belonging to that subspecies has to be considered as tentative. Future work including more in-depth genetic analyses should further examine the relationships between mainland European, insular and northern African populations of M. argentata.
This taxon forms two putatively allopatric populations, one from the Sinai Peninsula to southern Turkey (eastern populations), the other in northwestern Africa (western populations). The mitochondrial genetic divergences between these two populations were considerable (3.4% in COI analyses; Fig.
Unlike M. argentata, M. leachella exhibits considerable morphological variation over its wide range, including variation in vestiture colour, in sculpture and in the structure of the genital capsule. There was also considerably more genetic structuring in M. leachella than in M. argentata (Figs
In continental Europe and in the UK, phenotypic variation is essentially restricted to vestiture colour in the female sex (
The populations from northwestern Africa (from Tunisia to Morocco) exhibit a striking difference in the structure of the genital capsule: the gonostylus has a short preapical process (Fig.
On the Islands of Crete, a distinct form is found, which is morphologically slightly divergent but genetically strongly divergent from all other populations of M. leachella (genetic distances in COI on average 5.3%). Morphological differences include the presence of numerous dark hairs laterally on the terga, smaller spots of white hairs on the disc of T6 (Fig.
On the Island of Cyprus, the populations of M. leachella are morphologically strongly divergent from those on continental Europe. The punctation of the terga in the female sex is fine and dense (Figs
Lastly, the populations from Sardinia and to some extend Corsica exhibit weak morphological differentiation compared to continental European populations. In particular, in males the front tarsi are yellowish white (Fig.
Lastly, we have examined several females of M. leachella from Lesvos, in which the ocelloccipital distance was particularly long, approaching the condition observed in M. anatolica (cf. Fig.
Megachile anatolica Rebmann, 1968: 37, ♂ nec ♀, “Mut [Turkey, approx. 36.64°N, 33.44°E]”. Holotype ♂ (SMFD).
Type material. Holotype ♂ (SMFD) of M. anatolica (Fig.
104 specimens from the following countries: Croatia, Cyprus, Greece, Iran, Israel, Italy, Jordan, Lebanon, Turkey (Suppl. material
From Italy eastwards through the Levant including Lebanon, Turkey, Israel northwest of the Dead Sea, Iran; distribution in Central Asia remains to be established due to unclear relationship with M. viridicollis.
The species varies in the colour of the vestiture as well as in body size and in the length of the OOD. In Italy, Greece, Cyprus and western Turkey, the scopa is white (black on S6) and the OOD is large (Fig.
The relationship between M. anatolica and the Central Asian species M. viridicollis is not clear; these two taxa may eventually be treated as conspecific, in which case M. anatolica would be placed in synonymy with M. viridicollis; see under M. viridicollis.
Megachile argentata (Fabricius, 1793)
Figs
Apis argentata
Fabricius, 1793: 336 [sex not indicated], “in Barbaria” [Algeria or Tunisia]. Lectotype ♀ (NHMD), by designation of
Megachile compacta
Pérez, 1895: 24, ♀, [Algeria]. Preoccupied, not Megachile compacta Smith, 1879. Lectotype ♀ (
Megachile crassula Pérez, 1896: 1. Nomen novum for M. compacta Pérez. New synonymy.
Perezia maura
Ferton, 1914: 233, ♀ [gynandromorph specimen], “Cimetière de Djidjelli” [Jijel, Algeria]. Holotype intersex (
Megachile pilidens
Alfken, 1924: 88, ♀ ♂, “Triest [Trieste, Italy]”. Lectotype ♀ (
Megachile argyrea
Cockerell, 1931: 275, ♀ ♂, “Asni [Morocco]”. Holotype ♀ (
Type material. Lectotype ♀ of M. argentata (NHMD) (Figs
Lectotype
♀ of M. crassula (
Megachile argentata 15 female metasoma of northwestern African populations, M. argentata argentata 16 female metasoma of European, Levant, Turkey and Central Asian populations, M. argentata argentata 17 female metasoma of Malta populations, M. argentata schmiedeknechti 18 female metasoma of Corsican and Sardinian populations, M. argentata schmiedeknechti 19 female metasomal tergum 4 20 female vertex 21 apex of female clypeus 22 male front tarsi 23 male metasomal sterna 3–5 24 male genitalia.
Holotype
[gynandromorph] of Perezia maura (
Lectotype
♀ of M. pilidens (
Paratypes
♀ and ♂ of M. argyrea (
Megachile beaumonti Benoist, 1951, is currently treated as a synonym of M. crassula (
216 specimens from the following countries: Croatia, France, Germany, Greece, Iran, Italy, Kyrgyzstan, Lebanon, Morocco, Northern Macedonia, Portugal, Russia, Serbia, Spain, Switzerland, Tunisia, Turkey, Ukraine (Suppl. material
Widespread and abundant in southern Europe; in expansion in central and northern Europe, e.g., in northern Switzerland (C. Praz et al., in prep.), the Netherlands (
Geographic variation has been discussed above in detail. The northwestern African populations, as well as populations from the Island of Pantelleria, have overall snow-white vestiture in the female sex (Fig.
Megachile Schmiedeknechti Costa, 1884: 169, ♀ ♂, [Italy, Sardinia].
Megachile xanthopyga
Pérez, 1895: 25, ♀ ♂, “Sassari [Italy, Sardinia]”. Lectotype ♀ (
Lectotype
♀ (
We did not examine type specimens of M. schmiedeknechti and do not know whether syntypes exist. The identity of the species is clear from the original description. The date of the original description of M. schmiedeknechti is unclear; its first, very brief description in Latin was published in the “Rendiconto dell’Accademia delle Scienze fisiche e matematiche, fascicolo 12, anno XXIII, dicembre 1884”; it is unclear if this volume was printed in 1884. A longer description, including a description in Italian, was published in 1885 (
18 specimens from France (Corsica), Italy (Sardinia) and Malta (Suppl. material
Restricted to Malta, Corsica, and Sardinia.
The Maltese populations have the vestiture bright red orange (Fig.
As noted above, it is possible that the superficially similar appearance of the Maltese and Corso-Sardinian populations is the result of independent convergent evolution. Our genetic analyses did not suggest a close relationship between these populations (although no nuclear sequence data was available for the Maltese populations). Awaiting additional genetic results, we continue to refer the Maltese populations as M. argentata schmiedeknechti.
Megachile inexspectata Rebmann, 1968: 43, ♂, “Mut [Turkey, approx. 36.64°N, 33.44°E]”. Holotype ♂ (restricted to genitalia) (SMFD).
Type material. Holotype ♂ of M. inexspectata (SMFD) (Fig.
63 specimens from the following countries: Cyprus, Greece (Rhodes), Israel, Jordan, Lebanon, Morocco, Turkey (Suppl. material
Morocco, Egypt (Sinai), Israel, Lebanon, Cyprus, Rhodes, Turkey.
See above, species delimitation.
Megachile leachella Curtis, 1828
Figs
Megachile albipila
Pérez, 1895: 23, ♀ ♂, “Alger [Algeria]”. Lectotype ♂ (
Type material. Lectotype ♂ (
44 specimens from Algeria, Morocco and Tunisia (Suppl. material
Morocco, Algeria and Tunisia. All males examined from these three countries had the preapical process of the gonostylus short (Fig.
Holotype
♀ (Fig.
Paratypes
(Suppl. material
Restricted to the Island of Crete, Greece.
Female: highly similar to southern populations of the nominal subspecies, differs as follows: apical tergal fringes snow white (Figs
Male: nearly identical to the nominal subspecies (Fig.
Megachile leachella 32–36 female metasoma 32 UK, M. leachella leachella 33 Corsica and Sardinia, M. leachella leachella 34 northwestern Africa, M. leachella albipila 35 Crete, M. leachella cretica ssp. nov. 36 Cyprus, M. leachella densipunctata ssp. nov. 37–39 female metasomal tergum 4 37 UK, M. leachella leachella 38 Crete, M. leachella cretica ssp. nov. 39 Cyprus, M. leachella densipunctata ssp. nov.
Megachile leachella 40–43 female vertex 40 UK, M. leachella leachella 41 northwestern Africa, M. leachella albipila 42 Crete, M. leachella cretica ssp. nov. 43 Cyprus, M. leachella densipunctata ssp. nov. 44 holotype female of M. leachella cretica ssp. nov. 45 holotype female of M. leachella densipunctata ssp. nov.
Megachile leachella 46, 47 male metasoma 46 Switzerland, M. leachella leachella 47 Cyprus, M. leachella densipunctata ssp. nov. 48–52 male front tarsi 48 UK, M. leachella leachella 49 Switzerland, M. leachella leachella 50 Corsica and Sardinia, M. leachella leachella 51 Crete, M. leachella cretica ssp. nov. 52 Cyprus, M. leachella densipunctata ssp. nov. 53 male sterna 4–6 54–56 male genitalia 54 UK, M. leachella leachella 55 northwestern Africa, M. leachella albipila 56 Crete, M. leachella cretica ssp. nov.
The subspecies epithet refers to the geographic distribution of this taxon, which is probably restricted to the Island of Crete.
Holotype
♀ (Fig.
Paratypes
(Suppl. material
Restricted to Cyprus.
Female: similar to southern populations of the nominal subspecies, differs as follows: apical tergal fringes yellowish white (Figs
Male: nearly identical to the nominal subspecies, differs as follows: light vestiture of terga particularly developed, forming two conspicuous bands of hairs, one basally and one apically (Fig.
The subspecies epithet refers to the particularly dense punctation of the terga of the female.
Megachile leachella Curtis, 1828: [explanation to Plate 218], [sex not indicated], “[England]”.
Megachile dorsalis
Pérez 1879: 223, ♀ nec ♂, “Bordeaux; environs de l’étang de Cazaux; Arcachon; Royan [France]”. Lectotype ♀, by designation of
Megachile bioculata
Pérez, 1902: 119, ♀ [erroneously indicated as ♂], “Catalogne [Spain: Catalonia]”. Lectotype ♀, by present designation (see below) (
Megachile argentata var. fossoria
Ferton, 1909: 550, [sex not indicated], “Propriano [France, Corsica]”. Lectotype ♀, by designation of Schwarz & Gusenleitner (2011: 258) (
Megachile ichnusae Rebmann, 1968: 31, ♂ nec ♀, “Sardinien, Siniscola” [Italy, Sardinia, approx. 40.58 N, 9.70 E]. Holotype ♂, (SMFD). New synonymy.
Megachile discriminata
Rebmann, 1968: 34, ♂, “Turkestan, 189., Golodnaja Step. [Uzbekistan]”. Holotype ♂ (
Megachile leachella maadiensis van der Zanden, 1986: 67, ♂, “[no locality given: Egypt]”. Details on type material or type locality not given.
Type material. Lectotype ♀ (
Lectotype
♀ (
Lectotype
♀ (
Holotype ♂ (SMFD) of M. ichnusae (SMFD). The female paratype is a female of M. fertoni.
Holotype
♂ (
174 specimens from the following countries: Croatia, Egypt, UK, France, Greece, Iran, Israel, Italy, Kyrgyzstan, Montenegro, North Macedonia, Portugal, Spain, Switzerland, Syria, Turkey, Uzbekistan (Suppl. material
Widely distributed in Europe from Portugal, Spain, France, north to the UK, Scandinavia, northern, central, southern and eastern Europe, Levant (Turkey, Lebanon, Egypt, Israel), Iran, central Asia. We have examined specimens of the nominal subspecies from Chios, Lesvos, Rhodos and Santorini, but from no other Aegean Islands (see above for the populations of Crete and Cyprus). Highly similar (>98% similarity) DNA barcodes from unidentified specimens from the Beijing Region (Genbank accession number KC560312;
See above (species delimitation).
Megachile leucostoma
Pérez, 1907: 489, ♂, “Dibba [Oman]”. Holotype ♂ (
Megachile submucida
Alfken, 1926: 126, ♀, ♂ partim, “Kingi [Maryut, sw von Alexandria; Egypt]”. Lectotype ♀, by designation of
Megachile microxantha
Cockerell, 1937: 205, ♂, “Aden [Yemen]”. Holotype ♂ (
Megachile privigna
Rebmann, 1968: 40, ♂, “Fayed [Egypt]”. Holotype ♂ (SMFD). Synonymy in
See
In Israel, Jordan and Oman, the scopa is nearly entirely orange (see above under M. anatolica); in the UAE, the scopa is mostly white, orange on S6. In Egypt, the scopa is usually dark on S6, white on S2–S5, but often slightly orange on S5. Whether the white scopa, as observed in Egypt, is the result of introgression with M. pusilla, remains unknown. It is also possible that the orange scopa is the result of introgression with the taxon referred to as M. venusta from Africa, which nearly always has orange scopa. Given its wide distribution in Egypt and in the Arabian Peninsula, M. leucostoma may in fact be present in the Afrotropical region, and could be conspecific with an African taxon, for example M. modestissima Dalla Torre, 1896 (a replacement name for M. modesta Smith, 1879, presumably described from the Karthoum area; see below). Megachile modestissima is currently placed in synonymy with M. venusta.
Megachile pusilla
Pérez, 1884: 263, ♀ ♂, “Portugal”. Lectotype ♀, by present designation (
Megachile variscopa Pérez, 1895: 24, ♀, “Bône” [Annaba, Algeria]. Lectotype ♀, by present designation. New synonymy.
Megachile timberlakei
Cockerell, 1920: 119, ♂ ♀, “Kaimulai [sic]|, Oahu” [Kaimuki, Honolulu, Hawai, USA; introduced]. Holotype ♂ (
Megachile atratula Rebmann, 1968: 38, ♂ ♀, “Rapallo” [Italy]. Holotype ♂ (SMFD?), paratypes ♂ ♀ (SMFD). New synonymy.
Megachile striatella Rebmann, 1968: 41, ♂ ♀, “El Kantara” [Algeria]. Holotype ♂ (restricted to genitalia) (SMFD), paratypes ♂ ♀ (SMFD). New synonymy.
Megachile sudai Ikudome, 1999: 3, ♀, [Okinawa, Japan; introduced]. New synonymy.
Type material. Lectotype ♀ (
Lectotype
♀ (
Paratypes ♂ ♀ (SMFD) of M. atratula. The holotype, indicated to be in Rebmann’s collection (SMFD) could not be located.
Holotype ♂ (SMFD) of M. striatella (see above). Paratypes ♀ ♂ of M. striatella (SMFD).
Notes: we did not examine the holotype of M. timberlakei, but pictures are available on the online catalogue of
We did not examine the type material of M. sudai, but examined and sequenced specimens from Okinawa kindly sent by H. Nagase; these specimens perfectly agree with M. pusilla; see
54 specimens from the following countries: Argentina (introduced), France, Greece, Greece (Crete), Italy, Japan (introduced) Malta, Morocco, Spain, Tunisia, USA (introduced) (Suppl. material
See
Specimens from Algeria and Tunisia have the scopa often partly orange on S5; whether this condition results from introgression with M. leucostoma remains to be established.
A published barcode generated from a specimen collected near Perth, Western Australia (BOLD accession number MSAPB1368-19) is 100% identical to sequences of M. pusilla, suggesting that M. pusilla has also been introduced into Australia. This specimen is identified as M. obtusa Smith, 1853. We examined a picture of the holotype of M. obtusa (OUMNH) ; this species has modified front tarsi and does not belong to the same species group as M. pusilla.
Megachile fulvescens Walker, 1871: 47, ♀ ♂, “Harkeko; Wâdy Gennèh; Wâdy Ferran; Mount Sinai [Arkiko, Eritrea; ?; Wadi Feiran, Sinai, Egypt; Sinai, Egypt]”. Preoccupied, not M. fulvescens Smith, 1853.
Megachile walkeri Dalla Torre, 1896: 452. Replacement name for M. fulvescens Walker, 1871.
Megachile argentata var. moricei Friese, 1899b: 334, ♀ ♂, “Elephantinen; Philae; Ober-Aegypten-Assuan [Egypt, Elephantine and Philae Island; Aswan].
Megachile blanda
Rebmann, 1968: 44, ♂, “Luxor [Egypt]”. Holotype ♂, SMFD. Preoccupied, not M. blanda Mitchell 1930. Synonymy in
See
Megachile concinna
Smith, 1879: 79, ♀, “St. Domingo [Dominican Republic; introduced]”. Syntype (or holotype) ♀ (
Megachile multidens Fox, 1891: 345, ♀ ♂, “Kingston [Jamaica; introduced]”.
Type material. Syntype (or holotype) ♀ of M. concinna (
Note: It is likely that M. derelictula Cockerell, 1937, described from Barbados, is also a synonym of M. concinna.
13 specimens from the following countries: Benin, Cape Verde, Dominican Republic (introduced), French Guyana (introduced), Kenya, Republic of Trinidad and Tobago (introduced) (Suppl. material
This species is difficult to separate from other members of the concinna complex. The genetic analyses of
Megachile venusta
Smith, 1853: 159, ♀, “Port Natal; Cape of Good Hope [Durban; Cape of Good Hope; South Africa]”. Syntype ♀ (
Megachile modesta
Smith, 1879: 63, ♀, “White Nile. Collected by Consul Petherick [following
Megachile modestissima Dalla Torre, 1896: 439. Replacement name for M. modesta Smith, 1879.
Type material. Syntype ♀ of M. venusta (
Syntype
♀ of M. modesta Smith, 1879 (
11 specimens from the following countries: Central African Republic, Kenya, Senegal, South Africa (Suppl. material
The identity of this species is unclear and requires additional work; for this reason, the list of synonyms given above is incomplete. In the phylogenetic analyses of
Megachile viridicollis Morawitz, 1875: 117, ♂, “поймать только раз в степи Кизиль кумъ 15 мая у восточной окрайны горы Каракъ [Caught only once in the steppe of Kyzyl Kum, the 15. May, at the eastern edge of the mountain Karak; Kyzyl Kum does not refer to the Kyzyl Kum Desert, but probably to the locality Қызылқұм, approx. 41.911N 67.988E, Kazakhstan]”.
Type material. We were not able to examine the type material of M. viridicollis. The placement of this species into the concinna complex is based on the original description, which mentions that the species is highly similar to “M. argentata” (either M. pilidens or M. leachella), but markedly larger, and with a conspicuous tooth at the base of the mandible. We interpret this tooth as the tooth present just behind the base of the mandible (as in Fig.
Eight specimens from Kazakhstan and Uzbekistan (Suppl. material
The following description is based on one male specimen from Baygekum and several female specimens from Gazli, Uzbekistan, presumed to be conspecific.
Male: Member of the concinna complex, as determined by the presence of the tooth behind the mandibular base and the apically simple genitalia. OOD as in European populations of M. anatolica (as in Fig.
Female: similar to M. anatolica, differs from that species in the following characteristics: larger (body length 11 mm). Vertex laterally covered with short, brownish hairs, so that integument is not visible under vestiture unless the hairs are removed (Fig.
So far known only from few specimens from Kazakhstan and Uzbekistan.
The identity of this taxon remains unclear, as very little material has been studied.
Males
1 | S4 medially with a small tubercule covered with yellowish to greyish hairs (Fig. |
Megachile argentata (Fabricius) |
– | S4 medially without tubercule, with a small (Figs |
2 |
2 | S4 medially with particularly dense patch of yellowish hairs (Fig. |
3 |
– | S4 with a small spot of yellowish hairs medially (Fig. |
4 |
3 | Integument of T1-T2 predominantly orange (Arabian Peninsula, Egypt including Sinai Peninsula, Israel, Iran) | M. walkeri Dalla Torre |
– | Integument of T1-T2 predominantly dark brown (Northern Africa, Israel, Sinai Peninsula, Lebanon, Turkey, Cyprus, Rhodos) | M. inexspectata Rebmann |
4 | Gonostylus apically bifid, with short or long preapical process (Figs |
Megachile leachella Curtis |
– | Gonostylus apically simple (Figs |
5 |
The separation of the following species is difficult in the male sex
5 | Vertex mostly longer, ocelloccipital distance subequal to interocellar distance (Fig. |
M. anatolica Rebmann |
– | Vertex shorter, ocelloccipital distance shorter than interocellar distance (Fig. |
6 |
6 | Southern Europe, northwestern Africa (identity of populations located between Egypt and Tunisia unclear) | M. pusilla Pérez |
– | Arabian Peninsula, southern Israel, Egypt | M. leucostoma Pérez |
Females
1 | Integument of T1 and T2 predominantly brown-orange ( |
M. walkeri (Dalla Torre) |
– | Integument of T1 and T2 dark brown. Ventral surface of trochanters and femora 2 and 3 without short, modified hairs | 2 |
2 | Vertex mostly longer, ocelloccipital distance approximately equal to 1.5–1.8 x diameter of lateral ocellus (Fig. |
M. anatolica Rebmann |
– | Vertex shorter, ocelloccipital distance approximately subequal to diameter of lateral ocellus (e.g. Fig. |
3 |
3 | Apical clypeal margin with emargination narrow, often with only three little-visible, rounded teeth (Figs |
4 |
– | Apical clypeal margin with emargination broad, either straight with little visible rounded teeth, or with five very small teeth (Fig. |
5 |
4 | Scopa usually white, black on S6, sometimes with isolated orange hairs on S5. Southern Europe, northwestern Africa (identity of populations comprised between Egypt and Tunisia unclear) | M. pusilla Pérez |
– | Scopa often extensively orange, sometimes entirely orange, although also white (dark on S6) in Egypt. Arabian Peninsula, southern Israel, Egypt | M. leucostoma Pérez |
5 | Disc of T4 with comparatively sparse punctation (there is much variation in this character; a separation from M. argentata is not always straightforward, especially in regions where the vestiture colour of M. leachella is not snow white and does not offer additional discriminating characters with M. argentata), interspaces on average as large or larger than puncture diameters (Fig. |
M. leachella Curtis |
– | Disc of T4 more densely punctured (Figs |
6 |
6 | Vestiture snow white (Fig. |
M. inexspectata Rebmann |
– | Vestiture grey-brown (Fig. |
M. argentata (Fabricius) |
This taxonomic revision of a small group of widely distributed leafcutting bee taxa exemplifies one of the problems associated with taxonomic revisions: the identification of type material. This task was complicated by: i. poorly preserved types, where the morphological characters were difficult to examine (e.g., many holotypes of species described by O. Rebmann); ii. type specimens belonging to a sex that was not easily identified (e.g., M. argentata), or consisting of a gynandromorph individual (Perezia maura); iii. type specimens consisting of several body parts not originating from a single individual (M. inexspectata, M. striatella); iv. type specimens originating from introduced populations, where the source of the introduced population was initially unknown (M. timberlakei and M. sudai; M. concinna); and v. type specimens whose type locality is unclear (e.g., M. modesta Smith, 1879: type locality “White Nile”, a nearly 4000-km river segment that flows from Uganda to Sudan). DNA barcoding was pivotal for solving most of these issues, especially for confidently establishing the identity of introduced populations of M. pusilla and M. concinna. However, what should have been a simple taxonomic revision of seven rather well-characterized species turned into a tedious study. This case exemplifies a major paradox in taxonomy, as our study would have been completed at least twice as quickly if no previous taxonomic work had been conducted at all, enabling us to simply describe the species as new.
One approach would have strongly accelerated the process: the assembly of a DNA barcode reference library for the most problematic type specimens. We could have focused on the scientifically interesting part of a taxonomic revision – species delimitation – and the fastidious nomenclatural translation of species delimitation into names would have been more straightforward. Laboratory protocols are available to obtain full DNA barcodes from 19th century specimens (Strutzenberg et al. 2012; Prosser et al. 2015;
This study was only possible with the continuous support of Maximilian Schwarz, to whom CP expresses his gratitude. We thank all people who kindly made material available for study, especially Felix Amiet, Achik Dorchin, P. Andreas Ebmer, Alireza Monfared, Andreas Müller, Christian Schmid-Egger, Maximilian Schwarz, Thomas Wood, and the people mentioned in Suppl. material
List of examined specimens, with BOLD and genbank accession numbers
Data type: Occurences