On the presence of Cissites maculata (Coleoptera: Meloidae) in Mexico

Sobre la presencia de Cissites maculata (Coleoptera: Meloidae) en México

Mario García-París¹*, Celeigher Piñango², Jesús Manzanilla² and Alejandro Zaldívar-Riverón³

¹ Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas. José Gutiérrez Abascal, 2, 28006 Madrid, Spain. *mparis@mncn.csic.es

³ Colección Nacional de Insectos, Instituto de Biología, Universidad Nacional Autónoma de México. 3er. circuito exterior s/n, Cd. Universitaria, Copilco. Apartado postal 70-233, 04510 México, D.F., México.

Recibido: 29 octubre 2012
Aceptado: 21 enero 2013

Abstract

The presumed sympatry and validity of morphological diagnostic characters used to separate the only 2 described species of Cissites (Coleoptera: Meloidae), C. maculata (Swederus) and C. auriculata Champion, are assessed. Morphological diagnostic features between both species (head shape, antennae length, thorax shape, first metatarsal segment length, and elytral coloration) are constant over their entire geographic distribution, without the existence of intermediate morphs. Regional sympatry between these species was found in central Mexico, confirming the presence of C. maculata in Central America and Mexico, whereas C. auriculata, widely distributed in Central America, has not colonized South America. Sequences of the mitochondrial gene cytochrome oxidase were obtained from single Mexican specimens of each species. Divergence between the sequences is considerably high (14.5%), suggesting separation of both species as a result of an ancient cladogenetic event.

Key words: Nemognathinae, Mexico, South America, sympatry, COI.

Se investiga la probable simpatría y validez de los caracteres morfológicos diagnósticos empleados para distinguir a las 2 únicas especies de Cissites (Coleoptera: Meloidae), C. maculata (Swederus) y C. auriculata Champion. Los caracteres morfológicos diagnósticos de ambas especies (forma de la cabeza, longitud antenal, forma del tórax, longitud del primer segmento del metatarso y color de élitros) son constantes a lo largo de toda su distribución geográfica, sin existencia de formas intermedias. Se encontró simpatría regional entre ambas especies en el centro de México, confirmándose la presencia de C. maculata en América Central, mientras que C. auriculata, ampliamente distribuida en América Central, no ha colonizado América del Sur. Las secuencias del gen mitocondrial citocromo oxidasa, obtenidas a partir de un ejemplar mexicano de cada especie, muestran una divergencia considerablemente alta (14.5%), por lo que la separación entre ambas especies sería consecuencia de un evento cladogenético muy antiguo.

Palabras clave: Nemognathinae, México, América del Sur, simpatría, COI.

Introduction

Beetles of the subfamily Nemognathinae (Coleoptera: Meloidae) are represented in the Americas by species classified in 2 tribes: Horiini and Nemognathini (Pinto and Bologna, 1999). American Nemognathini are represented by about 130 species grouped in 8 genera, whereas the New World fauna of Horiini only has 2 species, both in the genus Cissites Latreille, 1804: C. maculata (Swederus, 1787) and C. auriculata Champion, 1892. According to literature, the geographic distribution of the New World species of Cissites appears to be mostly parapatric. Cissites maculata occurs from northern Argentina and Brazil to Panama and the Antilles (Selander and Bouseman, 1960; Genaro, 1996), with questionable isolated records in Costa Rica, Nicaragua, Mexico (Champion, 1892; Enns, 1958), and southern United States (Champion, 1892; Enns, 1958; Werner et al., 1966). The geographic range of C. auriculata extends from Costa Rica to northern Mexico and southern United States (Champion, 1892; Enns, 1958; Maes, 1989; Lewis, 2004; Maes and Huether, 2007; García-París et al. 2007, 2009). Records of C. auriculata from the Antilles (Champion, 1892; Leng and Mutchler, 1914; Blackwelder, 1945) require confirmation according to Enns (1958) and Selander and Bouseman (1960). This last species was introduced in Hawaii, apparently without success (Bianchi, 1962; Pinto and Bologna, 1999).

Since the discovery and description of C. auriculata (Champion, 1892), all previous records of C. maculata (Swederus, 1787) located north of Panama have been questioned or discarded. Rejection of records previous to Champion (1892) was based in objective reasons, because at that time only C. maculata was known, and consequently all subsequently revised material certainly corresponded to C. auriculata. This is apparently the case of Dugés' (1869, 1889) records of C. maculata from Colima, which were transferred to C. auriculata by Champion (1892). In other cases, however, rejection was made only based on the implicit assumption that both species would not occur sympatrically. As a result, records of C. maculata within the geographic area of C. auriculata would be treated as erroneously labeled or accidentally introduced (Werner et al., 1966). Such were considered, for example, the Mexican records of C. maculata of Champion (1892) from Morelia (Michoacán), or Enns' (1958) records from Arizona. Those uncertainties led García-París et al. (2007) to conclude that C. maculata probably had to be excluded from the Mexican fauna of Meloidae. With this large amount of possible erroneous historical identifications or labeling mistakes it is easy to believe that C. maculata and C. auriculata are easy to confuse with each other; however, despite a common general facies, and considerable sexual and intrapopulational variability, the specific characters reported by Champion (1892) have not been challenged for consistent species identification.

In order to shed light on the geographic distribution and presumable sympatry between C. maculata and C. auriculata, we revised 2 large series of Cissites from Mexico and Venezuela. Our objectives were to determine the validity of morphological diagnostic characters used to separate C. maculata and C. auriculata, to document the existence of regional sympatry between the 2 taxa in Mexico, and to determine mitochondrial differentiation level between single Mexican specimens of each taxon.

Materials and methods

External morphology was studied under a stereomicroscope. Habitus and morphological details were photographed with a Nikkon digital camera. For morphological descriptions we follow Enns (1958).

A 658 bp fragment of the cytochrome oxidase I mitochondrial DNA gene, was generated for 2 specimes of Cissites following Alcobendas et al. (2008) procedures (HF586634 C. auriculata y HF586635 C. maculata). These specimens, each morphologically assignable to C. maculata and C. auriculata following Champion's (1892) criteria, were obtained from nocturnal inspection of building lights in Estación de Biología de Los Tuxtlas (Veracruz) and Estación de Biología de Chamela (Jalisco) respectively, both administrated by the Instituto de Biología (UNAM). These 2 specimens were the only individuals found after 8 and 3 visits made to Chamela and Los Tuxtlas regions during 3 years and 2 years, respectively (including settings of UV light traps).

Results

Morphological diagnostic characters. Adult specimens of Cissites are easily identified as such among Neotropical and Nearctic Coleoptera based on their characteristic habitus. Large size, buprestoid shape, orange-red coloration spotted with large irregular black dots, large prothorax, large wide head, with oversized black mandibles in males, give to Cissites an unmistakably appearance (Figs. 1-4).

According to Champion (1892), the 2 species currently included in Cissites are diagnosed by differences in head shape, antennae length, thorax shape, first metatarsal segment length, and to a lesser extent, elytral coloration. Champion's (1892) description of C. auriculata is precise, and allows a readily and accurate identification of specimens of both sexes; however, individual variation is extreme in Mexican samples. This is particularly evident in male head and prothorax shape, which seems to vary in relation to specimen size. Large males of C. auriculata show marked bumps in head temples, strong and robust prominent mandibles, and a much more robust and subcylindrical prothorax (Figs. 2, 4). A similar variation pattern occurs within C. maculata (Figs. 1, 3), in which larger males present the anterior portion of the pronotum wider than the base, as already indicated by Champion (1892). Specimens with reduced black elytral pattern, or totally black, were reported amongst normal colored specimens of C. maculata (Perty, 1830; Pic, 1929; Betrem, 1932).

Champion's (1892) diagnostic characters were checked in our examined specimens. The head in C. maculata is flattened or broadly depressed frontally, while it is narrowly and more deeply incised in C. auriculata. Antennae are comparatively shorter in C. maculata than in C. auriculata, both in males and females. Thorax strongly transverse (length / width ratio= 0.61, n= 10) and with anterior angles raised in C. maculata, while it is less transverse, almost subquadrate (in some specimens it actually looks longer than wide at naked eye) (length / width ratio= 0.76, n= 12) and with anterior angles deflexed in C. auriculata (Figs. 3, 4). First metatarsal segment clearly shorter than the following articles together in C. maculata (first segment vs. 2 to 4 segments length ratio= 0.68, n= 10), subequal or slightly shorter in C. auriculata (first segment vs. 2 to 4 segments length ratio= 0.96, n= 11). Coloration pattern is quite similar in specimens of both species, but in C. maculata the spots on central areas of the elytra are terminology, the antemedial juxta-sutural spots are fused generally smaller (Figs. 1c, d) disappearing completely along the suture forming a transverse large black patch in some specimens. In contrast, in C. auriculata medial (Figs. 2a, c). Individual variation across Champion's (1892) elytral spots are larger, and, following Champion's (1892) diagnostic characters is minimal, and allows separation of all specimens into 2 specific groups, which correspond to the species currently accepted.

Sympatry between Cissites maculata and C. auriculata. All specimens from Colombia, Ecuador, Guyane Française, Peru, Dominican Republic, Trinidad and Tobago, and Venezuela share the diagnostic characters described for C. maculata, showing the typical variation reported for the species (Perty, 1830; Champion, 1892). Most of our Mexican specimens examined (51), share the diagnostic features described for C. auriculata, encompassing the individual variation already mentioned for the species (Champion, 1892); however, 13 specimens from the state of Veracruz (Los Tuxtlas), and 1 from the state of Puebla (Jicotepec de Juárez) are unambiguously assignable to C. maculata, including specimens without the medial elytral dots, like those described by Perty (1830).

The specimen of C. maculata from Jicotepec de Juárez is located north from any currently known Mexican continental population of the species, including the questioned records of C. maculata from Morelia (Champion, 1892), that Enns (1984), reported erroneously as "Morelos". Populations of C. maculata from Jicotepec de Juárez and Los Tuxtlas are in close proximity to localities where C. auriculata is present, including some in Veracruz (Tierra Blanca, Plan del Río), and more distantly, in Puebla (Tehuacán). In any case, Jicotepec de Juárez and Los Tuxtlas are deeply nested inside the geographic range of C. auriculata. Consequently, the implicit hypothesis of lack of sympatry between C. maculata and C. auriculata, used to question former localities of C. maculata located north of Panamá, should be disregarded. We therefore revalidate former Champion's (1892) records of C. maculata in Chontales (Nicaragua) and Morelia (Mexico). Based on habitat differences, and lack of presence along geographically intermediate localities, we agree with Werner et al. (1966) and treated records of C. maculata from Arizona (Enns, 1984) as the result of a possible man made introduction. We had also the opportunity to study the 2 specimens upon which Duges (1869, 1889) reported the presence of C. maculata in Colima (Mexico), and, in agreement with Champion (1892), we conclude that they actually belong to C. auriculata.

Adult activity and phenology. Data presented in labels of specimens of C. maculata from Venezuela show that adult specimens are active throughout the year. The maximum number of specimens captured per collecting event was normally one, but 2 specimens were collected in 12 occasions, and 3 in 3 occasions. Indications of capture methods report the use of mercury lamps and unspecified lights.

Fifty four specimens of C. maculata were collected in the nearby localities of El Limón and Maracay, in the state of Aragua, Venezuela, between 1952 and 1987 (with 1 additional record from 1996). The Museo of Zoología Agrícola is located in Maracay, where highly active entomologists have been collecting material along the period indicated. This large species is easily spotted and generally collected always when found, so it is probable that all specimens of Cissites found by MIZA researchers were kept in the collection. Counting all specimens captured along the period 1952-1987 in El Limón and Maracay, we obtained a collecting rate of 1.5 specimens of C. maculata per year. The maximum number of specimens captured per collecting event was 3 (1 occasion), and 2 (1 occasion also). These figures of per year collection rate and maximum number of specimens captured per event, are an additional indication of the rarity of the species even in highly favorable areas. The specimens collected in Maracay and El Limón were distributed along the year, with a maximum in September and a minimum in March, as follows: I (4 specimens), II (4), III (1), IV (2), V (4), VI (3), VII (2), VIII (4), IX (11), X (6), XI (10), XII (3).

The 15 specimens of C. maculata collected at Los Tuxtlas (Veracruz, Mexico) were found from January to July, with almost half of the records obtained in June (7 specimens). Adult specimens of C. auriculata are active along the Mexican territory during most of the year, though there are no records for March, October and December. Eleven records from Chamela (1976-1982) show activity as follows: II (2), IV (3), V (3), VII (3), but this pattern may reflect taxonomist's preferred collecting periods for other taxa.

Discussion

Morphological diagnostic features between C. maculata and C. auriculata are constant and expressed over large geographic areas, without any sign for the existence of intermediate morphs. Cytochrome oxidase sequence divergence between C. maculata and C. auriculata is deep, suggesting that the split amongst them was the result of an ancient cladogenetic event. Lack of intermediate morphs and deep mitochondrial divergence indicate that C. maculata and C. auriculata have been separated as independent species for a long period of time. Current sympatry in Mexico could be a consequence of relatively recent colonization events, resulting from C. maculata dispersals into the range of C. auriculata, that ocurred once the speciation process was concluded. Evidence of regional sympatry of C. maculata and C. auriculata in central Mexico, allows to reconsider all previous "questionable" reports of C. maculata in Central America and Mexico, while the study of large series of Venezuelan material, confirms Champion's (1892) opinion that C. auriculata has not colonized South America.

Acknowledgments

We appreciate all the help from the Museo del Instituto de Zoología Agrícola (MIZA) of the Universidad Central de Venezuela (Maracay), and from the Colección Nacional de Insectos of the Instituto de Biología (CNIN-IBUNAM) of the Universidad Nacional Autónoma de México, for allowing the study of material. We are particularly indebted to Vilma Savini (MIZA), Luis José Joly (MIZA), Ma. Cristina Mayorga (IBUNAM), and Santiago Zaragoza (IBUNAM). We thank Marco Bologna for allowing us to study his meloid collection at the University Roma Tre. We especially thank Valeria Salinas, Erik Luque, Oscar Pérez, and Nohemí Percino for field assistance looking for or finding Cissites samples, and Yolanda Jiménez for obtaining the mitochondrial sequences. MGP collaborative research with the Universidad Central de Venezuela was supported by a grant of the AECI (Agencia Española de Cooperación Internacional). This work was funded by the project grant CGL2010-15786 (Ministerio de Ciencia e Innovación, Spain).

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