Print version ISSN 0373-5680
Rev. Soc. Entomol. Argent. vol.70 no.3-4 Mendoza July/Dec. 2011
Biological notes on two species of Oxycorynus (Coleoptera: Belidae) associated with parasitic plants of the genus Lophophytum (Balanophoraceae), and new distribution records in Argentina
Notas biológicas sobre dos especies de Oxycorynus (Coleoptera: Belidae) asociadas con plantas parásitas del género Lophophytum (Balanophoraceae), y nuevos registros de distribución en Argentina
Ferrer, María S.*, Adriana E. Marvaldi*, Héctor A. Sato** and Ana M. Gonzalez**
* Laboratorio de Entomología, Instituto Argentino de Investigaciones de Zonas Áridas (IADIZA), CCT CONICET- Mendoza, C.C. 507, 5500 Mendoza, Argentina; e-mail for correspondence: email@example.com
** Instituto de Botánica del Nordeste C.C. 209. 3400 Corrientes, Argentina
ABSTRACT. This contribution provides new information on the association of weevils of the genus Oxycorynus Chevrolat (Belidae: Oxycoryninae) with parasitic plants of the genus Lophophytum Schott & Endl. (Balanophoraceae). New distribution records of Oxycorynus in Argentina are provided.
KEY WORDS. Weevils; Oxycoryninae; Hostplants; Jujuy; Misiones.
RESUMEN. Se brinda nueva información sobre la asociación de gorgojos del género Oxycorynus Chevrolat (Belidae: Oxycoryninae) con plantas parásitas del género Lophophytum Schott & Endl. (Balanophoraceae). Se proveen, además, nuevos registros de distribución de Oxycorynus en Argentina.
PALABRAS CLAVE. Gorgojos; Oxycoryninae; Plantas hospedadoras; Jujuy; Misiones.
Weevils of the subtribe Oxycorynina (Belidae: Oxycoryninae) occur in Central and South America, and the species of its four genera are associated with root parasitic dicots belonging to the families Hydnoraceae and Balanophoraceae (Marvaldi & Ferrer, in press). Three genera occur in South America from southern Peru, through Bolivia, to northern and central Argentina and southern Brazil. The South American genera are: Hydnorobius Kuschel, with three species endemic to Argentina, associated with species of Prosopanche de Bary (Hydnoraceae) (Ferrer & Marvaldi, 2010); Alloxycorynus Voss, with two species distributed in Argentina, Bolivia, and Peru, associated with species of Ombrophytum Poepp (Balanophoraceae) (Bruch, 1923; Anderson, 2005); and Oxycorynus Chevrolat, with five species from Argentina, Bolivia and Brazil, whose biology and host plant associations remained unknown (Kuschel 1959, 1995). The species Balanophorobius gamezi Anderson from Central America (Costa Rica), the only one of the genus, was described based on adults reared from larvae collected in inflorescences of a Balanophoraceae, most likely Helosis cayennensis (Sw.) Spreng. (Anderson, 2005). A weevil association with a balanophoraceous plant is provided by Borchsenius & Olesen (1990), who report the occurrence of adults and larvae of an unidentified weevil ("Curculionidae sp.") on inflorescences and infrutescences of Lophophytum mirabile Schott & Endl. in Ecuador (observed from April to June). Access to reference specimens is no longer possible (Borchsenius & Olesen, in litt. 2009), but according to Fig. 2 (p.503) such weevil species is almost certainly a member of the subtribe Oxycorynina. Anderson (2005) reported the association of species of Oxycorynus with parasitic plants of the genus Lophophytum Schott & Endl. (Balanophoraceae), from label data of two specimens from Argentina housed at the Canadian Museum of Nature, identified as O. nigripes Kuschel and O. armatus Buquet, although identification of the latter is not certain (Anderson, 2010 in litt.).
Figs. 1-4. 1, 2: The balanophoraceous hostplants of Oxycorynus spp. 1, habitus of Lophophytum leandrii, hostplant of O. missionis, detail of tuber and basal portion of the inflorescence, some scales that cover the inflorescence are still attached to the base; 2, habitus of Lophophytum mirabile subsp. bolivianum, hostplant of O. nigripes. 3, 4: Biology of Oxycorynus missionis. 3, adult feeding between female flowers; 4, larva developing in the infrutescence. Scale = 5mm. Photos 1-3: A. M. Gonzalez, photo 4: A. E. Marvaldi.
The plant family Balanophoraceae comprises 17 genera containing about 42 species of root holoparasites, distributed primarily throughout the tropical areas of the world (Nickrent, 2002). So far, the Neotropical species of the balanophoraceous genera Lophophytum, Ombrophytum and Helosis are the only known host plants of the oxycorynine weevils (Anderson, 2005; Marvaldi et al., 2006, Marvaldi & Ferrer, in press).
In order to corroborate the association of Oxycorynus spp. with Lophophytum (Balanophoraceae), several localities from Northern Argentina were explored for balanophoraceus plants and their weevil hosts. Two field trips resulted in the finding of Oxycorynus spp associated to L. leandrii Eichler in Misiones (by A. M. G.) (Fig. 1) and to L. mirabile subsp. bolivianum (Wedd.) in Jujuy (by H. A. S.) (Fig. 2). Adult weevils of both sexes were found feeding on the inflorescences of the plants (Fig. 3), that were dug out and kept in bags for further inspection in the laboratory. The weevils correspond to two different species of Oxycorynus: O. missionis Kuschel (Figs. 5, 6) associated to L. leandrii, and O. nigripes (Figs. 7, 8) associated to L. mirabile subsp. bolivianum. The adults were identified using Kuschel's (1995) key and by comparison with reference specimens of O. missionis, including types from the Bruch collection, from the "Museo Argentino de Ciencias Naturales" (MACN). The associated larvae found in the infrutescences (Fig. 4) have the diagnostic features of Oxycorynina according to Marvaldi (2005) and Marvaldi et al. (2006).
Figs. 5-8. Habitus of Oxycorynus species associated with Lophophytum. 5-6, Oxycorynus missionis, 5, female; 6, male. Scales = 1mm. 7-8, O. nigripes; 7, female; 8, male. Scales = 5 mm. Photos: A. E. Marvaldi.
Biological observations. Both plant species of Balanophoraceae consist of a subterranean body or tuber, and inflorescences emerging from the soil (Gonzalez & Mauseth, 2010). The inflorescences can reach 50 cm in height, being the female flowers located at the basal portion and the male flowers at the apex (Figs. 1, 2). In Misiones, L. leandrii blooms by the end of the winter season (September), and in Jujuy, L. mirabile shows its flowers during the summer (January).
In both cases adult weevils were found feeding nectar (Fig. 3) and mating on the female flowers which are at ground level. No pollen feeding was observed, although the weevils may carry pollen in their bodies, from the male flowers (located above) to the female flowers (located below) (Fig. 1). Their function as pollinators is not confirmed though. Larvae were found inside the female inflorescences, in the parenchymatic tissue, one larva per inflorescence branch (Fig. 4), continuing their development in the vegetative tissue of the infrutescence. Although no pupae were found, pupation most likely takes place in situ, in the plant tissues, as it is known to occur in other oxycorynine species (Marvaldi, 2005; Marvaldi et al. 2006).
The association of Oxycorynus missionis with Lophophytum leandrii is herein documented for the first time, as well as the association of Oxycorynus nigripes with Lophophytum mirabile subsp. bolivianum. The collecting localities are new distribution records for both weevil species, being O. nigripes the first record for Jujuy province. The previous known distribution, host plant data, and the new records are provided below. Voucher weevil specimens are deposited in the entomological collection of IADIZA (two individuals of each species dry pinned and the other specimens preserved in pure ethanol) and in the MACN collection. Voucher plant specimens of L. leandrii and L. mirabile subsp. bolivianum are deposited in the herbarium of IBONE (Instituto de Botánica del Nordeste, Corrientes, CTES).
Oxycorynus missionis Kuschel, 1995 Previous known distribution. Argentina, Misiones: Loreto.
Previous host plant association: Unknown. New records. Argentina, Misiones, Colonia Aborígen Andresito, San Ignacio, 27°15'32''S, 55°31'9'' W (11/09/2010), A. M. Gonzalez, 20 adult specimens (16 specimens deposited in IADIZA, 4 (2♂, 2♀) deposited in MACN), ex. flowers of Lophophytum leandrii parasitizing Parapiptadenia rigida Benth. (Fabaceae).
Oxycorynus nigripes Kuschel, 1959 Previous known distribution. Southern Bolivia: Villa Montes; Argentina: Chaco. Previous host plant association: Unknown. New records. Argentina, Jujuy, sendero Herradura del Parque Nacional Calilegua, 23º41'12.3'' S, 64º53'51'' W, 1611 m.s.n.m. (21/01/2011), H. A. Sato, 7 adult specimens (6 specimens, both sexes, deposited in IADIZA, 1 deposited in MACN), ex. flowers of Lophopytum mirabile subsp. bolivianum.
We are very grateful to Gustavo E. Flores and Rodolfo Carrara for leading the trip to Jujuy and for their help to H.A.S in the field collection activities. Thanks also to Axel Bachmann and Arturo Roig Alsina for the loan of oxycorynine specimens of the Bruch collection (MACN, Buenos Aires), and the two reviewers for their suggestions and comments. This work was supported through the following research grants: PIPs from CONICET #5766 and #112-200801-00162 to A.E.M, and grant # AVG 966 to H.A.S and A.M.G. The continuous support of Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina) is greatly acknowledged.
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