Francisco Armendáriz-Toledano

Two Species within Dendroctonus frontalis (Coleoptera: Curculionidae): Evidence from Morphological, Karyological, Molecular, and Crossing Studies

ABSTRACT Dendroctonus frontalis Zimmermann is considered one of the most important economic and ecological forest pests in the United States, Mexico, and Central America. Recently, two apparent morphological variants of this species were discovered occurring syntopically in Central America and southern Mexico. Morphotype A beetles lack a series of fine parallel ridges on the episternal area of the prothorax that are present on morphotype B. The goal of the present work was to clarify the taxonomic status of the morphotypes of the D. frontalis species complex. Geometric morphometric analyses of seminal rod and spermatheca shape together with the characterization of 16 attributes of external morphology revealed differences in quantitative and qualitative characters that distinguished adults of the two morphotypes from each other as well as from the closely related species Dendroctonus vitei Wood and Dendroctonus mexicanus Hopkins. Karyotype analysis of morphotype B revealed a chromosomal formula (5AA + Xyp) distinct from that found in morphotype A previously reported for D. frontalis (7AA + Xyp). In the laboratory, forced intermorphotype crosses produced F1 progeny but at lower frequency than intramorphotype pairings, and dissections of spermatheca revealed a lower frequency of insemination at least one type of heterotypic cross. Phylogenetic analysis of the D. frontalis species complex based on 786 bp of the cytochrome oxidase I gene indicated that morphotypes B and A are two independent groups with 98% nodal support within D. frontalis. These data provide compelling evidence that the two syntopic morphotypes represent two distinct sibling species.

A New Species of Bark Beetle, Dendroctonus mesoamericanus sp. nov. (Curculionidae: Scolytinae), in Southern Mexico and Central America

ABSTRACT The bark beetle Dendroctonus mesoamericanus sp. nov. is described from a population in Parque Nacional Lagunas de Montebello, La Trinitaria, Chiapas, Mexico. This species belongs to the D. frontalis complex, which includes D. adjunctus Blandford 1897, D. approximatus Dietz 1890, D. brevicomis LeConte 1876, D. frontalis Zimmermann 1868, D. mexicanus Hopkins 1905, and D. vitei Wood 1975. The new species can be distinguished from closely related species D. frontalis, D. mexicanus, and D. vitei by four diagnostic morphological characters: the presence of striations on the preepisternal area of the prothorax (anterolateral pronotum) in both sexes, seminal rod with an approximately linear posterior margin of the dorsal process (in lateral view), irregularly sized ornamentations on the distal edge of squamiform plates present on the eighth abdominal tergite in females, and an inconspicuous pronotal callus in females. Furthermore, the karyotype of D. mesoamericanus sp. nov. (5AA+Xyp / XX) differs from that of its sister species D. frontalis (7AA + Xyp/XX). Dendroctonus mesoamericanus sp. nov. is distributed in Belize, Guatemala, El Salvador, Honduras, Nicaragua, and in the Michoacán, Oaxaca, and Chiapas states in Mexico. In these countries, this species has been collected at elevations above from 311 to 2600 m on six pine species, and it commonly occurs in syntopy with D. frontalis.

Comparative Study of the Antennae of Dendroctonus rhizophagus and Dendroctonus valens (Curculionidae: Scolytinae): Sensilla Types, Distribution and Club Shape

ABSTRACT We compared the antennae of two sibling bark beetle species, Dendroctonus rhizophagus Thomas and Bright and Dendroctonus valens LeConte, to identify biologically and taxonomically relevant differences. Specifically, we characterized the diversity of sensilla types by using environmental scanning electron microscopy, quantified the abundance and distribution of the different types of sensilla on the antennal club, and characterized club shape through multivariate and geometric morphometric analyses. We identified four classes of sensilla in both species: chaetica, fluted, trichodea (three distinct types), and basiconica (long and short). ANOVA and MANOVA demonstrated that the number and distribution of sensilla with the potential for chemoreception (i.e., short and long basiconica) differed between species and sexes. Notably, the long sensilla basiconica in the third sensory band were clustered in D. rhizophagus but not in D. valens. Geometric morphometric analysis using 27 landmarks showed that antennal club shape differed significantly between the two species and was not correlated with antennal size. The shape differences were associated with the number and distribution of sensilla.

Review of the Geographical Distribution of Dendroctonus vitei (Curculionidae: Scolytinae) Based on Geometric Morphometrics of the Seminal Rod

ABSTRACT The known distribution of the bark beetle Dendroctonus vitei Wood has been basically restricted to species-type location in Patzun, Guatemala, and in San Cristobal de las Casas, Chiapas, Mexico. There are also reports of the species in Veracruz, Oaxaca, and Nuevo Leon, Mexico. This bark beetle cannot be confidently distinguished from its sibling species Dendroctonus frontalis Zimmermann, Dendroctonus mexicanus Hopkins, and Dendroctonus sp. nov. by morphological characteristics (e.g., color and pronotum width). It has been proposal that the seminal rod is a useful characteristic to distinguish these species; however, its robustness has not been assessed quantitatively. The goal of the present work was to analyze the seminal rod from 601 specimens of the D. frontalis complex, collected in 89 locations from Mexico and Guatemala, using geometric morphometrics to clarify and update the distribution of D. vitei. Our results confirmed the presence of this species not only in the previously recognized locations (Patzun, Guatemala; San Cristobal de las Casas, Chiapas; Perote Veracruz, and Chipinque, Nuevo Leon) but also in seven new ones. The analyzed specimens of D. vitei and other D. frontalis complex species showed a strong differentiation in seminal rod shape among them. The accumulated information indicates that D. vitei is distributed across the entire Sierra Madre Oriental, the east Trans-Mexican volcanic belt, the Sierra Madre de Chiapas, and the Cordillera Central of Guatemala.

Illustrated Key to Species of Genus Dendroctonus (Coleoptera: Curculionidae) Occurring in Mexico and Central America

Abstract We provide an illustrated key of species of Dendroctonus Erichson from Mexico and Central America based on characters of the male genitalia and external morphology. The key incorporates newly identified diagnostic characters for this genus that enhance discrimination of particularly difficult sibling species.

The Current Status of the Distribution Range of the Western Pine Beetle, Dendroctonus brevicomis (Curculionidae: Scolytinae) in Northern Mexico

Abstract The distribution range of the western pine beetle Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae) is supported only by scattered records in the northern parts of Mexico, suggesting that its populations may be marginal and rare in this region. In this study, we review the geographical distribution of D. brevicomis in northern Mexico and perform a geometric morphometric analysis of seminal rod shape to evaluate its reliability for identifying this species with respect to other members of the Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae) complex. Our results provide 30 new records, with 26 distributed in the Sierra Madre Occidental and 4 in the Sierra Madre Oriental. These records extend the known distribution range of D. brevicomis to Durango and Tamaulipas states in northern Mexico. Furthermore, we find high geographic variation in size and shape of the seminal rod, with conspicous differences among individuals from different geographical regions, namely west and east of the Great Basin and between mountain systems in Mexico.

The Current Status of Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae) in Mexico

The mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins, 1902, has been referred to as the most destructive bark beetle of native pine forests in western Canada and the USA (Taylor et al. 2006). It is considered an aggressive species that colonizes and kills about 22 species of Pinus L. (Pinaceae), including four pine species not native to North America. Its preferential hosts are ponderosa pine (Pinus ponderosa Douglas ex C. Lawson), Mexican white pine (Pinus strobiformis Engelman), lodgepole pine (Pinus contortaDouglas), whitebark pine (Pinus albicaulis Engelman), sugar pine (Pinus lambertiana Douglas), and western white pine (Pinus monticola Douglas ex D. Don) (Furniss and Schenk 1969; Smith et al. 1981; Amman and Cole 1983; Six and Bracewell 2015). During outbreaks, however, it may also colonize other members of the Pinaceae (Wood 1982; Safranyik et al. 2010). Due to increasing outbreaks, ranging from small stands to hundreds of hectares, and the subsequent average annual loss in timber resources, this species is one of the most important ecological forces at the landscape level and has impacts over a large portion of western North America (Logan and Powell 2001; Safranyik et al. 2010). Dendroctonus ponderosae is widely distributed in western North America, fromBritish Columbia in Canada to Baja California in northern Mexico, as well as from South Dakota to the Pacific coast (as far as southern California) and central Arizona in the USA (Wood 1982; Mock et al. 2007). Climate change has promoted large-scale outbreaks of MPB populations and enabled the colonization of higher elevations, northern latitudes, and new host species (West et al. 2016). The beetle has extended its distribution to northern British Columbia in Canada and overcome the geographical barrier of the Rocky Mountains to colonize forests inAlberta (Carroll et al. 2003; McFarlane et al. 2006; Janes et al. 2014). In Mexico, there were only two records of MPB prior to the present study, both of which are from San Pedro Martir, Baja California (Wood 1982; Wood and Bright 1992; Atkinson 2007). The presence of the MPB in Mexico was thought to be apparently confined to San Pedro Martir at 2,300–2,400 m elevation, but unfortunately no data are available that indicate the host trees in this area (Wood and Bright 1992; Cibrián-Tovar et al. 1995; Salinas-Moreno et al. 2004, 2010). The absence of vouchers in entomological collections and the fact that MPB has not since been collected again in Baja California suggested that the occurrence of this species in Mexico is questionable (EquihuaMartı́nez and Estrada-Venegas 2011). Based on the presence of some known hosts, such as P. strobiformis and members of the ponderosae section (i.e., P. arizonica Shaw and P. engelmannii Carrière) in northwestern Sierra Madre Occidental (SMOc) in Chihuahua, we led an expedition to Mesa de las Guacamayas between May and June 2009 to obtain updated information on the distribution of Dendroctonus Erichson in northern Mexico and to verify the presence of theMPB in this region. Our efforts to collect this bark beetle during that survey were unsuccessful. A second survey was undertaken during the months of June and July 2015 in San José de los Tambos in the municipality of Janos, 7.3 km northeast of the GuacamayasMountains (30°320540N, 108°370350W). On this occasion, we found adult specimens in two dead P. strobiformis trees that had galleries typical of those reported for MPB (Wood 1982). Twenty-five specimens were identified using the key for Dendroctonus species of Mexico and Central America (Armendáriz-Toledano and Zu~niga 2017). Distinguishing characters of adults (\, _) that we collected include: 1) body color dark brown to completely black (Fig. 1A, B); 2) median region of the frons round andwithout a median groove (though theremay be a groove or line on the vertex) (Fig. 1C); 3) lateral margins of epistomal process elevated and