First records of three species of Oxycraspedus Kuschel ( Coleoptera : Belidae ) in Argentina and use of a predictive model to compare their potential distribution with the range of their hostplant , Araucaria araucana

The first records of the three known species of Oxycraspedus Kuschel (Belidae: Oxycoryninae) in Argentina are reported, and added to their known distribution in Chile. These weevils are of interest because of their association with the pehuén or monkey puzzle tree, Araucaria araucana, a species of conservation concern. Their distribution data are of value for the protection of biodiversity in natural areas of Patagonia. The potential distribution of Oxycraspedus, as predicted by a model using bioclimatic variables, is coincident as expected, with the geographic range of the araucaria host-plant.


INTRODUCTION
The genus Oxycraspedus Kuschel (Coleoptera: Belidae: Oxycoryninae) has three described species, which were, so far, only known from Chile (Kuschel 1959, 1995, 2001, Marvaldi 2005. The three species are associated with the conifer Araucaria araucana (Molina, 1782) C. Koch, being their adults and larvae found in decayed female cones of this plant (Kuschel 2001, Marvaldi et al. 2003 ). According to recent phylogenetic studies, the New World oxycorynines form a monophyletic tribe Oxycorynini, with Oxycraspedus retaining the ancestral belid association with conifers and being the sister group of the remaining Oxycorynini (Marvaldi et al. 2006). These weevils are considered to be survivors from Mesozoic times (Kuschel 1959, Farrel 1998, Marvaldi et al. 2002, thus antedating the Andes mountains uplift in the Cenozoic (Uliana & Biddle 1998). Their specific association with the conifer Araucaria is also thought to be very ancient, probably ancestral for the group (Marvaldi et al. 2006).
Araucaria araucana, commonly known as "pehuén" or Monkey-Puzzle tree, is an evergreen conifer endemic to the Valdivian forests of Chile and Argentina. The actual distribution range covers from 37 to 40º S, at both sides of Los Andes mountains in Chile and Argentina, and also a small area in Nahuelbuta mountains in Chile (Newton et al. 2003, Fig. 1). Although this tree species has been classified as vulnerable by the International Union for the Conservation of Nature (IUCN) and is listed on Appendix 1 of the Convention on International Trade in Endangered Species (CITES), there is still pressure from different land uses (Newton et al. 2003 (Eggers, 1942) (Curculionidae: Scolytinae). All known distribution records for Oxycraspedus are from Chilean localities, where pehuén occurs. Due to this close association with pehuén, it would have been expected to find these weevils also in the Argentine araucaria forests, however, no records of Oxycraspedus had been reported so far outside Chile. The goal of testing the hypothesis that the distribution of the weevil would coincide with that of the host-plant, which occurs at both sides of the Andean barrier, prompted the search of Oxycraspedus in decayed female cones from Argentine trees. Consequently, one of us (MSF) conducted a field expedition, in April 2006, to araucaria forests in Argentina to search for the presence of adults and immature specimens of Oxycraspedus. Additionally, we used a species distribution model (Guisan & Thuillier 2005) to further test the congruence between the distribution ranges of Oxycraspedus and pehuén.

MATERIAL AND METHODS
The araucaria forests visited are located in the following localities of Neuquén province, Argentina: Primeros Pinos, Moquehue and Villa Pehuenia. The accession to them is from Zapala through the provincial route Nº 13, and from the locality of Aluminé through the provincial route Nº 23.
Our target were dead female cones on ground, based on previous collecting experiences (Kuschel 2001, Marvaldi et al. 2003, but decayed female cones (without seeds) that were still on the trees, were also collected. Cones were placed in different bags grouped by locality. Male cones were collected as well, and kept separately from the female ones. They were both brought to the laboratory for close inspection. Larvae were killed in hot water and preserved in 80 % ethanol. Most adult specimens were placed in 96 % ethanol (for further molecular studies) and some were pinned and kept dried for morphological studies. Several cones were set aside and their larvae were reared until the adults emerged. The adult specimens were identified to species and sexed, following descriptions and keys provided by Kuschel (1959Kuschel ( , 1995Kuschel ( , 2001. All adult and immature weevils found are deposited in the Entomology collection of the Instituto Argentino de Investigaciones de Zonas Aridas (IADIZA).

Predictive models of species distribution
Species distribution models are used to predict species potential distribution by relating known species collection localities to a set of environmental variables that, presumably, reflect the ecological niche of the species (Guisan & Thuillier 2005). They produce spatial predictions of habitat suitability indicating where the target species might occur. The modeled niches can be projected under different environmental scenarios, thus producing habitat suitability maps for past or future climatic conditions (Graham et al. 2004). Accordingly, we georeferenced and mapped the presently known localities of the three species of Oxycraspedus and used them to model their distribution utilizing predictive methods based on bioclimatic variables. Information about localities where Oxycraspedus is distributed in Distribución de Oxycraspedus spp. en Chile y Argentina: registros publicados (triángulos negros), nuevos registros (círculos blancos). La distribución potencial del género se muestra en escala de grises, con los colores más oscuros indicando una probabilidad de ocurrencia más alta. La línea de puntos muestra el rango de distribución geográfica aproximado de la planta huésped Araucaria araucana. El área con líneas diagonales representa la ecorregión del matorral chileno.
Chile was taken from the literature and labels of the material deposited in the entomological collection of IADIZA. We used the program MaxEnt (Phillips et al. 2006), combined with 19 bioclimatic variables obtained from the WorldClim dataset (Hijmans et al. 2005) to model the distribution of Oxycraspedus. The resolution of the environmental layers used was, approximately, 4.6 x 4.6 km. The distribution range of Araucaria araucana was reconstructed from the data provided by Echeverría et al. (2004).

Biological notes
Adult specimens were found hidden between the bracts or sporophylls at the base of female strobili. They feed on the parenchimatous tissues of the bracts, and on the cone axis (pith). Larvae of different sizes (probably different instars and species) were feeding inside the cone axis and at the base of the sporophylls. A few adult individuals were also collected on male cones, but this seems to be fortuitous. Oxycraspedus larvae were found exclusively in female strobili. This contrasts with male araucaria cones which nurse larvae belonging to several species of different beetles (Kuschel & May 1990, 1996, Kuschel 2001, Mecke et al. 2005.

Potential distribution of Oxycraspedus and comparison with the distribution range of the host-plant
Given the host fidelity of the species of Oxycraspedus with A. araucana, it is clear that their distribution data are of value for the protection of biodiversity in natural areas of Patagonia. The potential distribution area for Hábito dorsal de Oxycraspedus spp. (A) O. cribricollis, hembra, cabeza y pronoto (protibia aumentada mostrando hilera de largas setas en su margen inferior, diagnóstica de la especie); (B) O. minutus, hembra (áreas humeral y pronotal amplificadas mostrando setas escamiformes blancas, diagnósticas de la especie); (C) O. cornutus, macho (notar las proyecciones corniformes a cada lado de la frente, diagnósticas del sexo masculino de la especie); (D) O. cornutus, hembra (notar la ausencia de dichas proyecciones frontales).

(A) (B) (C) (D)
Oxycraspedus predicted by the model is clearly coincident with the range of the araucaria hostplant (Fig. 1). The disjunct distributions of both the weevils and pehuén lie within the Valdivian Forest ecoregion, and are separated by the Chilean Matorral ecoregion (Fig. 1)