Spermacoce verticillata L. (synonym: Borreria verticillata (L.) G. Mey.) (Rubiaceae) conserves important pollinators and natural enemies around it (Dale et al. 2019). Commonly known as “shrubby false buttonweed” (GBIF 2021a), S. verticillata is a native herb from tropical America, but it is considered a weed in Brazil probably due to its tolerance to nutrient-poor soils and the easy dispersal of its seeds (Lorenzi 1991). This plant is part of folk medicine due to its antimicrobial (Koné et al. 2004) and anti-inflammatory properties (Lima et al. 2018); it is also a source of raw material for handicraft products (Lima et al. 2013). Spermacoce verticillata is also useful in biological control programs as it is the main source of nectar for wasps (Arévalo & Frank 2005, Leppla et al. 2007, Abraham et al. 2010, Portman et al. 2010). In addition, it has larvicidal activity against Aedes aegypti (Linnaeus, 1762) (Oliveira et al. 2010).
Chrysomelidae is the fourth largest family of the order Coleoptera. Because it is essentially phytophagous, it plays a big role in insect-plant interactions. Members of the subfamily Cryptocephalinae, represented in Brazil by 723 species in 37 genera (Chamorro et al. 2021), feed on green leaves, decaying plant material, and girdle stems (Chamorro 2014); some are myrmecophilous (Agrain et al. 2015). Members of the Cryptocephalini tribe are flower eaters and pollen eaters (Chamorro 2014). Some groups, as subtribe Pachybrachina, pose a complex identification challenge at genus level even for specialists (Sassi 2018).
Worldwide, two species are associated with Rubiaceae: Cryptocephalus trizonatus Suffrian, 1852 on Coffea sp. (Maes & Staines 1991) and Cryptocephalus moraei (Linnaeus, 1758) on Gallium sp. (Biondi & Di Casoli 1996, Maican & Munteanu 2008). None of the reports provide information about the presence of immatures on the plant.
We report a new record of Pachybrachis sp. whose adults and immature stages are in association with S. verticillata in Brazil. We also summarize the distribution records of this genus and its plant associations in Brazilian territory.
Two adults and two mature larvae specimens were collected in an urban area of Maceió, Alagoas (-9.558304, -35.776127) (Fig. 1), on S. verticillata (Fig. 2), near the Catolé e Fernão Velho Environmental Protection Area, fragment of the Atlantic Forest, in September of 2019. The plant was identified by Dra. Letícia Ribes de Lima (Universidade Federal de Alagoas). In the laboratory (24.1 - 26.0 °C, 62 - 77% RH, photoperiod 12:12 h), the larvae and adults were reared with daily addition of fresh parts of the plant, from which pupae and eggs were obtained. Morphometric determinations under stereomicroscope were performed too. Subsequently, a genera key (Chamorro-Lacayo 2013) of the subtribe Pachybrachina was used for identification of the beetles, which was confirmed by Dr. Davide Sassi (Università degli Studi di Milano). The analysis of publications related to the occurrence records made it possible to trace the current state of the genus occurrence and plant association for Brazil. Voucher specimens of the beetles will be deposited in the Padre Jesus Santiago Moure Entomological Collection, Federal University of Paraná, Brazil; plant exsiccates will be deposited in the Institute of the Environment of Alagoas’s Herbarium-MAC.
The beetles were identified as Pachybrachis Chevrolat, 1836 (Chrysomelidae: Cryptocephalinae: Cryptocephalini) (Figs. 3, 4), with female, ≈ 3.2 mm long (n = 1), being larger and more robust than the male, ≈ 3.0 mm long (n = 1). The following characters were confirmed by the key to identify specimens as in the genus Pachybrachis and differentiating it from similar genera such as Metallactus Suffrian, 1866 and Griburius Haldeman, 1849: (a) intercoxal process of the proesternum do not go further the posterior margin of the protrax; (b) broad and evident punctuations in the head, prothorax and elytra; (c) baseline of the elytra is wider than prothorax posterior line; and (d) dorsally flat prothorax, not domed. The egg fecal capsule is ≈ 0.7 mm long (n = 6) (Fig. 5) and the pupa fecal case is ≈ 5.1 mm long (n = 2) (Fig. 6).
Pachybrachis sp. adults feed on leaves of S. verticillata, while late instar larvae feed on inflorescences. Mature larvae seem to seek a position under the inflorescences, where they feed until pupation. Females lay their eggs on the inflorescences, but eggs were also found on substrate.
The genus Pachybrachis (220 species) is poorly studied in Brazil, with scarce and incomplete records. There is not a single record registered for Brazil in the GBIF (GBIF 2021b), the largest biodiversity data network. Ten studies have information about the genus Pachybrachis in Brazil (Table 1). The characteristics of the exact locations of occurrence are barely presented. Most (Baly 1877, Bowditch 1913, Albertoni 2008, Dias 2016, Guedes et al. 2019, Rafael et al. 2020) do not provide any information about plants. Only one study reports the presence and collection of immatures.
Four records provide information about the plants on which the specimens were found. The genus was recorded on Mimosa pigra L. (Fabaceae) and on Mimosa pigra var. berlandieri (A.Gray) B.L.Turner (accepted name: Mimosa pigra var. asperata (L.) Zarucchi, Vincent & Gandhi) (Fabaceae) (Harley et al. 1995); on Baccharis stylosa Gardner (Asteraceae) in a high altitude area (above 1600 meters) (Flinte et al. 2009); on Ipomoea carnea subsp. fistulosa (Mart. ex Choisy) D.F.Austin (Convolvulaceae) in Caatinga (Martins 2015); and on Chamaecrista cathartica (Mart.) H.S.Irwin & Barneby (Fabaceae) in urban area (Lopes 2020). However, only B. stylosa was confirmed as a host plant as immatures and adults were feeding on it.
In summary, we present as a novelty Pachybrachis sp. on S. verticillata, the first record of Rubiaceae as a host for this beetle genus. Not least, this is the first report of Pachybrachis immatures from Brazil.
Pachybrachis (name as reported) | State | Municipality or Distrite | Location | Phytophysiognomy | Plant (name as reported) | Notes on plant association | Literature |
---|---|---|---|---|---|---|---|
Pachybrachys contortus | Pará | Santarém | Banks of the Amazon | - | - | - | Baly 1877 |
Pachybrachys contortus | Ceará | - | - | - | - | - | Bowditch 1913 |
Pachybrachys contortus | Ceará | Maranguape | - | - | - | - | Bowditch 1913 |
Pachybrachys sp. 1 | Ceará | Independência | - | - | - | - | Bowditch 1913 |
Pachybrachys sp. 2 | Ceará | Independência | - | - | - | - | Bowditch 1913 |
Pachybrachys sp. 3 | Ceará | Independência | - | - | - | - | Bowditch 1913 |
Pachybrachys sp. 4 | Rio Grande do Norte | Natal | - | - | - | - | Bowditch 1913 |
Pachybrachis contortus | Minas Gerais | - | - | - | Mimosa pigra | The authors just report that adults were found on plant. Nothing about feeding. | Harley et al. 1995 |
Pachybrachis sp. nr. musiva | Minas Gerais | - | - | - | Mimosa pigra | The authors just report that adults were found on plant. Nothing about feeding. | Harley et al. 1995 |
Pachybrachis sp. | Amazonas, Minas Gerais, Pará, Paraná, São Paulo | - | - | - | Mimosa pigra | The authors just report that adults were found on plant. Nothing about feeding. | Harley et al. 1995 |
Pachybrachis sp. | Amazonas, Minas Gerais, Pará, Paraná, São Paulo | - | - | - | Mimosa pigra var. berlandieri | The authors just report that adults were found on plant. Nothing about feeding. | Harley et al. 1995 |
Pachybrachis sp. 1 | Santa Catarina | - | - | - | - | - | Albertoni 2008 |
Pachybrachis sp. 2 | Santa Catarina | - | - | - | - | - | Albertoni 2008 |
Pachybrachis sp. | Rio de Janeiro | - | Serra dos Orgãos National Park | High-montane forest | Baccharis stylosa | Plant should be considered a host plant because adults and larvae were found feeding on plant. | Flinte et al. 2009 |
Pachybrachis sp. | Rio de Janeiro | - | Serra dos Orgãos National Park | High altitude grassland | Baccharis stylosa | Plant should be considered a host plant because adults and larvae were found feeding on plant. | Flinte et al. 2009 |
Pachybrachis sp. | Paraíba | - | Caatinga | - | Ipomoea carnea ssp. fistulosa | Plant could be considered a food plant because adult was found feeding on plant. | Martins 2015 |
Pachybrachys sp. | Rio Grande do Sul | Aceguá | Pampa | - | - | - | Dias 2016 |
Pachybrachys sp. 1 | Paraíba | Santa Terezinha | Caatinga | Riparian forest | - | - | Guedes et al. 2019 |
Pachybrachys sp. 2 | Paraíba | Santa Terezinha | Caatinga | Riparian forest and xerophilous vegetation | - | - | Guedes et al. 2019 |
Pachybrachys sp. 3 | Paraíba | Santa Terezinha | Caatinga | Riparian forest and xerophilous vegetation | - | - | Guedes et al. 2019 |
Pachybrachys sp. 4 | Paraíba | Santa Terezinha | Caatinga | Riparian forest | - | - | Guedes et al. 2019 |
Pachybrachis sp. | Minas Gerais | Uberlândia | Urban area | (Don’t apply) | Chamaecrista cathartica | Plant could be considered a food plant because adult rearing on plant was performed. | Lopes 2020 |
Pachybrachis sp. | Pernambuco | Fernando de Noronha | Fernando de Noronha Marine National Park | - | - | - | Rafael et al. 2020 |