Synergus, Hartig, 1840
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publication ID |
https://doi.org/ 10.1093/zoolinnean/zlab085 |
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publication LSID |
lsid:zoobank.org:pub:A4CC7782-97F4-4246-B070-1C4FF62B1950 |
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DOI |
https://doi.org/10.5281/zenodo.6992961 |
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persistent identifier |
https://treatment.plazi.org/id/039887DF-C614-FF9F-FC8B-9506BF13F93A |
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treatment provided by |
Plazi |
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scientific name |
Synergus |
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IS SYNERGUS View in CoL View at ENA A MONOPHYLETIC TAXON?
Synergus has traditionally been considered to constitute a monophyletic taxon based on molecular and morphological data ( Pénzes et al., 2009, 2012; Ács et al., 2010; Bozsó et al., 2014; Schwéger et al., 2015a, b; Ide et al., 2018), but earlier analyses included only Palaearctic specimens. Despite the obtained phylogenies, these authors considered that the proposed global monophyly of Synergus should be treated with care, and that Nearctic and Neotropical species, which show significant morphological differences with respect to the Palaearctic taxa, must be included in future analyses. The description of new species from the New World during the last decade ( Nieves-Aldrey & Medianero, 2011; Lobato-Vila & Pujade-Villar, 2017, 2021; Lobato-Vila et al., 2017, 2018, 2019, 2020a, b, c) has reinforced the idea that Old World and New World Synergus will eventually be separated into different taxa (Lobato-Vila & PujadeVillar, 2017; Lobato-Vila et al., 2020c). This was already proposed by Bozsó et al. (2014) and Schwéger et al. (2015a), who suggested that the Nearctic Synergus should be separated at least into three distinct groups based on preliminary unpublished analyses. Our phylogeny confirms this premise, since the included New World Synergus are resolved into three, wellsupported molecular clades (named herein as New World clades 1, 2 and 3; see Fig. 2 View Figure 2 ) that are clearly separated from the Old World (Palaearctic) species. Furthermore, our results are coherent with those of Ward et al. (2020), who suggested the existence of two sets of fauna (Nearctic and Palaearctic) and at least two groups of Nearctic Synergus , according to their early combined molecular tree based on a single gene (COI). At this point, and in accordance with previous studies, can Synergus still be considered monophyletic? Our analyses suggest not.
The Palaearctic or Old World clade encompasses all the species from the WP and the EP without exceptions. These species are intermingled within the clade, with no evidence that WP and EP species represent independent regional radiations. We consider this clade as the ‘true Synergus ’ ( Synergus s.s.) since it includes the type species of the genus, Sy. facialis Hartig, 1840 [= Sy. gallaepomiformis (Boyer de Fonscolombe, 1832) ] (WP). Except for Synergus castaneus , Sy. plagiotrochi Nieves-Aldrey & PujadeVillar, 1987 and Sy. acsi Melika & Pujade-Villar, 2006 , all Palaearctic species have a lateral pronotal carinae, which is always absent in the Nearctic and Neotropical species. On the other hand, most of the species within this clade have lateral frontal carinae, female antennae are 14-segmented and the radial cell of the forewings are closed, and all of them have the mesopleuron completely sculpted ( Nieves-Aldrey, 2001; Melika et al., 2006; Sadeghi et al., 2006; NievesAldrey & Medianero, 2011; Bernardo et al., 2013; Schwéger et al., 2015a; Lobato-Vila & Pujade-Villar, 2017, 2021; Lobato-Vila et al., 2020a, b, c). Most of the Palaearctic species associate with oaks ( Quercus ) of section Quercus (see Fig. 2 View Figure 2 ).
The species in ‘New World clade 1’ (NA + NT) have more or less defined lateral frontal carinae; female antennae are always 14-segmented; the mesopleuron is either completely sculpted or with a smooth and shiny speculum; the radial cell of the forewings are mostly closed, rarely open; and the head and the mesosoma are weakly to strongly sculpted (LobatoVila & Pujade-Villar, 2017, 2021; Lobato-Vila et al., 2017, 2018, 2020a, b, c). None of the species in this clade has been reared from tuberous galls [except for Sy. pseudofilicornis (NA) and its related morphotypes] and they are usually reared from the oak sections Quercus , Lobatae or Protobalanus (see Fig. 2 View Figure 2 ).
The species in ‘New World clade 2’ (NA) have poorly defined and weak lateral frontal carinae, which are sometimes absent; the female antennae are either 13- or 14-segmented; the mesopleuron is always completely sculpted; the radial cell of the forewings are mostly closed, rarely open; and the head and the mesosoma are strongly sculpted ( Ashmead, 1885; Pujade-Villar & Melika, 2005; Lobato-Vila et al., 2018, 2019). All the species in this clade are associated with tuberous galls (except for Synergusconiferae), which are induced principally by Andricus spp. , formed on members of the oak sections Quercus and Lobatae (see Fig. 2 View Figure 2 ).
Lastly, species in ‘New World clade 3’ (NA + NT) always lack lateral frontal carinae; female antennae are always 14-segmented; the mesopleuron is always partially smooth, with the speculum finely sculpted to not sculpted; the radial cell of the forewings are always closed; and both the head and the mesosoma are weakly sculpted ( Lobato-Vila & Pujade-Villar, 2017; LobatoVila et al., 2020c). None of the species in this clade has been reared from tuberous galls and they are found on the oak sections Quercus and Lobatae (see Fig. 2 View Figure 2 ). The ‘New World clade 3’ is the most morphologically homogeneous among the three New World clades.
According to Lobato-Vila & Pujade-Villar (2017) and Lobato-Vila et al. (2020c), Synergus from the New World should be classified into three morphological groups: (1) species with the radial cell of the forewings open or partially open along the wing margin, which includes only two species: Synergus mexicanus and Sy. pedroi ; and species with the radial cell of the forewings closed, which are divided into two subgroups; (2) species with the mesopleuron completely sculptured, with parallel or subparallel transverse striae covering all its surface; (3) and species with the mesopleuron partially smooth, with the speculum always shining, smooth, not sculptured. The latter group, analysed in detail by Lobato-Vila et al. (2020c), seems to be unique to the New World. This morphological division is not supported by the presented molecular data, since the species with the radial cell of the forewings open and/ or with partially smooth mesopleuron are distributed among all three New World clades (Lobato-Vila et al., 2019, 2020a, c).
Based on the above mentioned, Synergus is undoubtedly a polyphyletic group and species in the New World clades ( Synergus s.l.) can no longer be considered as Synergus . From now on, we face the challenge of resolving the position of the four molecularly supported clades in Synergini and characterizing them morphologically in order to describe new taxa (genera), since all the species display a lot of evolutionary convergences (which is common among gall wasps; Pujade-Villar & Arnedo, 1997; Liljeblad et al., 2008). To this end, further studies should be conducted combining molecular, fine morphological and biological data (regarding both host plants and galls) from a large assemblage of Synergus from both the Palaearctic and the Nearctic and Neotropical areas.
SAPHONECRUS , SYNOPHRUS AND UFO
Saphonecrus has been considered as a nonmonophyletic taxon by various authors ( Pénzes et al., 2009, 2012; Ács et al., 2010; Bozsó et al., 2013, 2014; Schwéger et al., 2015a, b) and this is also supported by our analyses. Saphonecrus species included in our study are resolved into two main molecular clades: the Saphonecrus + Synophrus clade and the Saphonecrus + Ufo clade (see Fig. 2 View Figure 2 ).
The Saphonecrus + Synophrus clade is encompassed by a few WP and EP Saphonecrus [including its type species, Saphonecrus connatus (Hartig, 1840) (WP) ] and all the species within the genus Synophrus (WP) (including its type species, Synophrus politus Hartig, 1843 ). The inclusion of Synophrus in this clade creates a paraphyletic scenario for Saphonecrus ( Pénzes et al., 2009, 2012). Saphonecrus and Synophrus share two important characteristics: the radial cell of the forewings open along the wing margin and female antennae 13-segmented. Furthermore, both Saphonecrus species in this clade and Synophrus lack lateral pronotal carinae (Pujade-Villar & NievesAldrey, 1990; Nieves-Aldrey, 2001; Pénzes et al., 2009; Schwéger et al., 2015b; Melika et al., 2018). The species in this clade, group according to their host plants (see Fig. 2 View Figure 2 ). Pénzes et al. (2009) have suggested that Saphonecrus in the Saphonecrus + Synophrus clade would become synonymous with Synophrus if the topology supported by the morphological and combined molecular analyses was upheld. The topology of our molecular trees is constant regarding the species that are included in the clade, but the support of the relationships between the included species still needs to be improved. Thus, further combined molecular, morphological and biological analyses should be conducted. Resolving the internal position of the species in this clade could bring us to two possible scenarios: (1) if the analyses recover Saphonecrus and Synophrus in a unique, strongly supported group, Saphonecrus must be synonymized with Synophrus , in which case Saphonecrus will disappear because the type species of this genus ( Sa. connatus ) would be a Synophrus ; (2) if the analyses support the division of Saphonecrus and Synophrus , then these genera would coexist, with Saphonecrus species within this clade being considered as the ‘true Saphonecrus ’ ( Saphonecrus s.s.).
The Saphonecrus + Ufo clade comprises the rest of Saphonecrus species (WP + EP) and the two Ufo species that have been included in the analyses, with Saphonecrus being paraphyletic with respect to Ufo . Saphonecrus and Ufo have the radial cell of the forewings open and female antennae 13-segmented. Furthermore, Saphonecrus species within this clade have lateral pronotal carinae (Pujade-Villar & NievesAldrey, 1990; Sadeghi et al., 2006; Schwéger et al., 2015b), which are strong in Ufo , thus giving the pronotum an extreme angled shape from the dorsal view ( Melika et al., 2005, 2012). Species within this clade tend to group according to their host plant, as it happens with the Saphonecrus + Synophrus clade (see Fig. 2 View Figure 2 ). The species Saphonecrus nantoui appears grouped with the two Ufo species included in our analyses with a moderate support (BS = 69, PP = 0.93). However, Sa. nantoui cannot be considered to belong to Ufo because it lacks two of the main morphological characteristics that currently define this genus ( Melika et al., 2005): the strong pronotal carina, with the pronotum showing an extreme angled shape (well-defined and complete pronotal carina, but the pronotum not extremely angled from the dorsal view in Sa. nantoui ), and both the frons and vertex smooth or weakly sculpted (conspicuously sculpted in Sa. nantoui ) ( Schwéger et al., 2015b). Therefore, we face several possible scenarios in which the genus Ufo should be redescribed to include: (1) Sa. nantoui ; (2) Sa. nantoui and the rest of the species from Saphonecrus gilvus to Sa. shirakashii ( Fig. 2 View Figure 2 , upper to lower); (3) all the species from Saphonecrus lithocarpi to Sa. shirakashii ( Fig. 2 View Figure 2 , upper to lower); or (4) all the Saphonecrus species in the Saphonecrus + Ufo clade, in which all Saphonecrus species with lateral pronotal carina will be transferred to Ufo , with the current Ufo species being a possible extreme form in the newly redescribed Ufo in all scenarios. Regardless of which is the most plausible scenario, it is certain that Saphonecrus species in the Saphonecrus + Ufo clade ( Saphonecrus s.l.) can no longer be considered Saphonecrus . Further analyses combining molecular and morphological data exclusively from Eastern Palaearctic and Oriental Saphonecrus and Ufo species, including its type species Ufo abei Melika & PujadeVillar, 2005 , will help to redefine the limits of the genus Ufo in the clade; thus, we will be able decide whether the current Ufo species are an extreme form of the morphological variability in this ‘ Saphonecrus ’ subclade or form a distinct genus.
Regardless of the internal relationships in the two Saphonecrus clades ( Saphonecrus + Synophrus and Saphonecrus + Ufo ), the real challenge is to characterize both of them morphologically, because Saphonecrus also shows evolutionary convergences similar to Synergus . Furthermore, in case the combined analyses uphold the existence of internal radiations in these clades, it will also be necessary to provide morphological diagnoses of all of them.
SYNERGUS VS. SAPHONECRUS CONFLICT
Synergus a n d Saphonecrus h av e a l way s been considered to be related genera, but their morphological boundaries have never been clearly defined and thus the continuous description of new species with morphological characteristics between these two genera (especially in the New World) are making it more and more difficult to separate them. This has led to some authors transferring species from one genus to the other [e.g. Synergus brevicornis to Saphonecrus by Weld (1952), which was then transferred back to Synergus by Lobato-Vila et al. (2019)] or to describe dubiously placed species.
Our molecular data show that: (1) the existence of the genus Saphonecrus is questionable because it is paraphyletic with respect to Synophrus (see above); (2) Synergus and Saphonecrus species never fall into the same clade (see Fig. 2 View Figure 2 ). This suggests that Synergus and Saphonecrus have always been clearly separated, despite the fact that they will eventually be split into different taxa (genera). Therefore, the possibility that some Synergus from the New World belong to Saphonecrus can be totally ruled out in light of these results.
The current challenge is to define the Synergus and Saphonecrus clades and subclades morphologically in order to set the boundaries between them. The external morphological characteristics most commonly used to describe species within these genera have a high degree of evolutionary convergence and have proved insufficient. Therefore, combined analyses should be conducted on finer morphological differences between the molecularly supported groups within Synergus and Saphonecrus .
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