The American Tribes Anypotactini and Eudiagogini (Coleoptera, Curculionidae) in Eocene of Europe as Indicators of Eocene Climate with Description a New Species

Abstract

From the modern distribution of the tribes Anypotactini and Eudiagogini (Coleoptera, Curculionidae), it can be assumed that the climate of the late Eocene amber forests was similar to that of the Valdivian temperate forests. A new species, Paonaupactus zosimovichi sp. n. from the tribe Anypotactini of the subfamily Entiminae is described from Late Eocene Rovno amber. It differs from Paonaupactus gracilis by its rarer, decumbent scales on the elytral interstriae, elytral interstriae, which are clearly visible between scales, and its smaller body size. This is the third species of the genus Paonaupactus found in Rovno amber.

1. Introduction

The genus Paonaupactus Voss, 1953 belongs to the tribe Anypotactini and includes seven species from European Eocene ambers [1,2,3,4]. Initially, species of this group were described in the extinct genera Paonaupactus and Protonaupactus Zherikhin, 1971 (tribe Naupactini), and Sucinophyllobius Wanat & Borowiec, 1986 (tribe Phyllobiini), or assigned to extant genera Polydrusus Germar, 1817, Phyllobius Germar, 1823, and Otiorhynchus Germar, 1822, respectively, in the tribes Polydrusini, Phyllobiini, and Otiorhynchini [5,6,7,8]. Subsequently, the genus Paonaupactus was placed in the tribe Anypotactini [1]. The names Sucinophyllobius and Protonaupactus were synonymized with Paonaupactus [3,9]. Here, we describe a new species of the genus Paonaupactus from late Eocene Rovno amber, the third of this genus in Rovno amber.

2. Materials and Methods

The amber piece with a new species was found between Voronki and nearby Luko [10,11] in the Varash district of Rivne Oblast.

The studied specimens were deposited in the amber collection of the Schmalhausen Institute of Zoology of the National Academy of Sciences of Ukraine, Kiev (SIZK), Museum of Amber Inclusions, University of Gdańsk, Poland (MAIG) and the Institute of Systematics and Ecology of Animals, Siberian Branch, Russian Academy of Sciences, Novosibirsk (ISEA).

Images were taken using a Leica Z16 APO stereomicroscope equipped with a Leica DFC 450 camera (Leica Microsystems, Wetzlar, Germany).

The morphological terminology used in this paper follows Lawrence et al. [12].

Nomenclatural acts introduced in the present work are registered in ZooBank (www.zoobank.org) under LSID urn:lsid:zoobank.org:pub:54BE23FB-E3AA-4F04-9317-F315F2B02965.

3. Results

Systematic Paleontology

Family Curculionidae Latreille, 1802

Subfamily Entiminae Schoenherr, 1823

Tribe Anypotactini Champion, 1911

Genus Paonaupactus Voss, 1953

Paonaupactus zosimovichi Legalov, Vasilenko & Perkovsky, sp. n. (Figure 1)

LSIDurn:lsid:zoobank.org:act:66BF4F73-5795-43C0-A53B-59CBEE980C0F

Description. Size. Length without rostrum 3.8 mm, rostrum length 0.6 mm. Body black, covered with dense greenish scales. Rostrum weakly widened at apex, punctate. Rostrum about twice as long as wide at middle, about 1.2 times shorter than pronotum. Mandibles massive, with scar of deciduous process. Apex of rostrum with carina forming posterior edge of large epistoma. Eyes oval, strongly protruding from head, roughly compound, about 1.3 times as long as wide at middle. Forehead slightly wider than base of rostrum, flattened, with median line. Temples 0.9 times as long as eye, transversely wrinkled. Antennal scrobes lateral. Antennae inserted slightly behind middle of rostrum. Scape elongated, extending beyond anterior margin of pronotum, about 11.2 times as long as wide at apex. Antennal is compact, fusiform. Pronotum bell-shaped, densely wrinkly-punctured, rather wide. Elytra elongated, convex. Elytra about 3.7 times as long as pronotum. Humeri slightly flattened. Elytral interstriae barely convex, with 3–4 rows of semierect narrow scales. Surface of interstriae clearly visible between scales. Interstriae 3.3–4.0 times as wide as striae. Striae distinct and deep. Prosternum without postocular lobes. Metaventrite about 2.7 times as long as metacoxa. Abdomen convex. Ventrites located almost in the same plane. First and second ventrites long. First ventrite 1.7 times as long as metacoxa. Second ventrite 0.9 times as long as first ventrite. Femora thickened, without teeth. Metafemora about 4.7 times as long as maximum width. Tibia almost straight, flattened, slightly widened at apex, without mucro and uncus. Metatibial corbels open. Protibiae about 11 times as long as wide. Metatibia about 17 times as long as wide. Tarsi elongated. First tarsomere elongate-trapezoid. Second tarsomere trapezoid. Third tarsomere bilobed. Fifth tarsomere elongated. Claws free, without teeth. First protarsomere 3.1 times as long as wide at apex. Second protarsomere 1.6 times as long as wide at apex, 0.6 times as long as first protarsomere. Width of second protarsomere about 1.1 times as wide as first protarsomere. Third protarsomere 0.8 times as long as wide at apex, 0.9 times as long as and 1.8 times as wide as second protarsomere. Fifth protarsomere 5.7 times as long as wide at apex, twice as long as third protarsomere and approximately 0.3 times as wide.

Material examined. Holotype (SIZK L-960), female, Rovno amber.

Derivation of name. The species is named in honor of outstanding Ukrainian stratigrapher and author of the concept of Subparatethys, Vladimir Yurievich Zosimovich (1933–2022).

Diagnosis. The new species is very close to Paonaupactus gracilis Legalov, Nazarenko & Perkovsky, 2019, but is well distinguished by the rarer, semierect scales on the elytral interstriae and elytral interstriae, which are clearly visible between the scales, as well as the smaller body size. Remarks. The new species belongs to the subfamily Entiminae because it is characterized by massive mandibles with a scar of deciduous process, a short rostrum, and tibiae without uncus. The apex of the rostrum with a carina forming posterior edge of the large epistoma, free claws, lateral antennal scrobes, and prosternum without postocular lobes indicate that the new species belongs to the tribe Anypotactini. The open corbels of the metatibia allow it to be placed in the genus Paonaupactus.

Paonaupactus katyae Legalov, Nazarenko and Perkovsky, 2019 (Figure 2)

Material examined. Holotype MAIG, 5981, Rovno amber.

Paonaupactus gracilis Legalov, Nazarenko et Perkovsky, 2019 (Figure 3)

Material examined. Holotype SIZK, K-647, Klesov, Rovno amber. Paratype, SIZK, UA-1139, Rovno amber. Specimens RA2021/1 (ISEA), Rovno amber and RA2021/2 (ISEA), Rovno amber.

Key to species of the genus Paonaupactus of Rovno amber

1. Antennal scape barely extending beyond posterior margin of eye (Figure 2). P. katyae.

2. Antennal scape protruding beyond anterior margin of pronotum (Figure 3).

3. Scales on elytral interstriae denser, almost contiguous. Elytral interstices between scales almost invisible (Figure 3). Body larger (4.2–4.3 mm). P. gracilis.

4. Scales on elytral interstriae more sparse, semierect. Elytral interstices between scales clearly visible (Figure 1). Body smaller (3.8 mm). P. zosimovichi sp. n.

4. Discussion

It has been assumed that the low representation of Baltic amber beetle species in Rovno amber is an artefact of insufficient sampling [13]. Current knowledge based on larger numbers of specimens, however, could indicate that it reflects a real community difference with only two new species in common [14,15], while there are over a dozen and a half new species known only from Rovno amber [16,17,18,19,20,21,22,23,24,25,26,27,28,29,30], including 15% in common with Baltic amber. In contrast, the well-studied Trichoptera of Baltic and Rovno ambers have 32.4% [31,32,33,34] and non-ant hymenopterans have 32% [35,36,37,38] shared species.

Species of the genus Paonaupactus agree with this pattern; three are known from Rovno amber (P. gracilis Legalov, Nazarenko & Perkovsky, 2019, P. katyae Legalov, Nazarenko & Perkovsky, 2019, and P. zosimovichi sp. n.), and four are known from Baltic amber (P. microphthalmus (Zherikhin, 1971), P. sitonitoides Voss, 1953 (=Polydrosus scheelei Voss, 1953, =Phyllobius cephalotes Voss, 1972, =Otiorhynchus pellucidipes Voss, 1972), P. sobrinus (Voss, 1972), and P. viridis (Wanat & Borowiec, 1986)), collected in Yantarny (Russia), and Gdańsk region (Poland). Two Baltic amber Paonaupactus species were also found in Danish amber from the west coast of Jutland. There are no common species between Baltic and Rovno ambers, despite the fact that species of the genus account for 30% and 50% of the weevils in unbiased collections of Rovno and Danish amber. It is difficult to accurately estimate the abundance of Paonaupactus in Baltic amber. This cannot be compared with Baltic amber, which is subject to collecting bias of private collectors for “interesting” and rare taxa (see Dlussky and Rasnitsyn [39] and Perkovsky et al. [40]). Species of Paonaupactus and Electrotribus Hustache, 1942, are the most common weevils in the amber collections of the Kaliningrad Regional Amber Museum and the National Museum of Natural History (Paris), as well as in online stores and auctions. They make up 100% of all weevils in the unbiased Giecewicz collection of the Museum of the Earth in Warsaw [41]. Thus, despite this collecting bias, Paonaupactus were undoubtedly the dominant leaf weevils at least in the late Eocene of Northern and Eastern Europe, and we believe that the observed absence of shared species of this genus in Rovno and Baltic ambers results from a real community difference and indicates a real difference in terrestrial environments affecting them more than, e.g., ants [39,42].

Today, the tribe Anypotactini (Figure 4), which includes 14 extant genera, is distributed in Central America north to the southeast of the USA (Texas), on most islands of the West Indies, in the Northern Andes (mainly on the eastern slopes), in southeastern Brazil, and in the Valdivian region of Chile [1]. This distribution is relictual; their fossils are only known in the late Eocene ambers of Europe and not in the rich Eocene Lagerstättes of the Green River Formation and Florissant Formation, nor in Miocene Dominican amber [43,44]. They were probably replaced later in the Cenozoic by competing weevils occupying a similar arboreal ecological niche, the so-called “leaf” Adelognatha weevils, represented in Europe by the tribes Phyllobiini and Polydrusini. There are no reliable identified fossil Phyllobiini. Three species of Polydrusini are known from Baltic amber, but they are rare. We assume that Anypotactini were displaced in North America and Europe by ecological similar forms from Tanymecini (e.g., Pandeleteius Schoenherr, 1834), Scythropini (e.g., Pachyrhinus Schoenherr, 1823) and Polydrusini (Polydrusus Germar, 1817).

The genus Nototactus Kuschel, 1952 occurs in isolation from the main range of the tribe Anypotactini in relict warm temperate forests of their host Dombey’s beech (Nothofagus dombeyi). Nototactus may be a modern ecological analogue of the late Eocene Paonaupactus, today inhabiting a relictual analogue of the late Eocene middle latitude climate, and it further diminished as competitors appeared. In this case, one would expect a significantly greater abundance and diversity of Paonaupactus in Baltic amber compared to Rovno amber, observed for example in Scleroderminae [45], or at least a much greater diversity of the Baltic Paonaupactus compared to Rovno amber, as in extant Chilean–Argentine Bethylidae, common in subtropical regions of Chile including the Valdivian forests [46,47]; however, there are three Rovno species of Paonaupactus and four Baltic species, and the five Rovno + Danish species are even more common than the Baltic ones, albeit from greatly differing sample sizes.

However, the supposed wide range of the host plants of Anypotactini (nonspecialized Entiminae) may have contributed to the dominance of Paonaupactus in the amber forests of Europe. Thus, the generally more thermophilic American tribe Eudiagogini (Figure 5) associated in the Nearctic with trees of the legume family (Sesbania, Prosopis) [48,49] is represented in Europe by one species. Extant species of Eudiagogus close to the oldest species of the genus from the early Eocene Green River feed on Sesbania. Eudiagogini is known from early Eocene Oise amber, late Eocene Florissant, and Miocene Dominican amber, but not late Eocene amber of Europe. It can be assumed that species of this tribe were associated with legumes in the Oise amber forest, in which the amber tree was supposedly close to Hymenaea [50], and possibly also in the Dominican amber forest (the tribe Eudiagogini is absent in the modern Dominican fauna). In the late Eocene forests of Europe, legumes are almost unknown: two species have been reported in Baltic amber [51], but they are absent in the Eocene floras of Polissya [52]. The paratropical forests that produced Oise amber may have provided favorable conditions for Eudiagogini. Interestingly, the oldest narrow pod with seeds parallel to the axis of the fruit characteristic of Sesbania and several other extant genera of legumes [53] are thought to have originated in the rich late Oligocene swamp and riparian Eger Wind Brickyard flora of Hungary.

5. Conclusions

The geological and geographic distribution of the Neotropical tribes Anypotactini and Eudiagogini in Europe might be explained by a combination of climate and the presence or absence of host plants and competitors. The extinction of European Anypotactini coincides with an increase in temperature seasonality of the climate in the middle latitudes with the transition to the Oligocene. Even the genus Nototactus, the most adapted of the genera of the tribe to a temperate climate, endemic to the Valdivian temperate forests [54], is found in the mountains on the border of Chile and Argentina, which has an average coldest monthly temperature of 2–3 °C and is not found south of there, while the range of its host Nothophagus dombeyi extends to regions with frosts down to −10 °C [55]. There is no evidence to suggest that Paonaupactus had a greater ability to endure cold winters.