Cryptic Species Discrimination in Western Pine Beetle, Dendroctonus brevicomis LeConte (Curculionidae: Scolytinae), Based on Morphological Characters and Geometric Morphometrics

Abstract

The western pine beetle (WPB), Dendroctonus brevicomis LeConte, is a major mortality agent of pines in North America. A total of 706 adults of WPB from 81 geographical sites were analyzed with traditional and geometric morphometric methods to evaluate the variation of discrete and quantitative morphological characters with particular attention to the antenna, spermatheca, and seminal rod. Principal coordinates and canonical variate analyses supported three geographical groups in WPB: (1) West, from British Columbia to southern California along the Pacific coast, Idaho, and Montana; (2) East-SMOC, including Nevada, Utah, Colorado, Arizona, New Mexico, Texas, Chihuahua, and Durango; and (3) SMOR, including Coahuila, Nuevo Leon, and Tamaulipas. The pubescence length on the elytral declivity was a robust character for separating West specimens from the other groups. Additionally, the genitalia shape both female and male in dorsal view was a reliable character for discriminating among groups. Based on these results, which agree with genetic and chemical ecology evidence, we herein reinstate Dendroctonus barberi Hopkins (East-SMOC group) and remove it from synonymy with D. brevicomis (West group). Differences in the spermatheca and seminal rod shape of SMOR specimens suggest that these populations might be a different species from D. barberi and D. brevicomis.

The spermatheca in the genus Dendroctonus (Curculionidae: Scolytinae): morphology, nomenclature, potential characters for taxonomic use and phylogenetic signal

“…Morphometric analyses support that the shape of the seminal receptacle allows the recognition of distinct geographic groups in D. brevicomis, information that contributed to removing D. barberi Hopkins from synonymy (Valerio-Mendoza et al, 2019). In other congeners, this structure presents a species-specific shape, as is the case of D. approximatus-D. parallelocollis and D. mexicanus-D. vitei, whereas, in others such as D. frontalis and D. mesoamericanus, the shape of the spermatheca has only been partially differentiated (Armendáriz-Toledano et al, 2014).…”

“…The taxonomy of the genus Dendroctonus Erichson is traditionally based on external morphological attributes, such as the abundance, distribution, and size of cuticular ornamentation and pubescence on the different body parts (Hopkins, 1909;Wood, 1982). The use of these characteristics has shown that some of them are not useful to separate closely related species, because they present wide intraspecific geographic variation (Armendáriz-Toledano et al, 2014;Lanier et al, 1998;Valerio Mendoza et al, 2019).…”

“…Of the 21 species recognized for the genus (Valerio-Mendoza et al, 2019;Víctor & Zúñiga, 2016;Wood, 1982), the anatomy of the female genitalia is only known in detail in D. ponderosae Hopkins (Cerezque, 1964) and for 7 more species (D. approximatus Dietz, D. brevicomis LeConte, D. frontalis Zimmerman, D. mesoamericanus Armendáriz-Toledano & Sullivan, D. mexicanus Hopkins, D. parallelocollis Chapuis, and D. vitei Wood) the studies have only focused on describing and comparing qualitative and quantitative attributes of the "spermatheca" (= seminal receptacle, sensu De Marzo, 2009) as well as the patterns of variation in shape, all for taxonomic purposes (Armendáriz-Toledano et al, 2014García-Román et al, 2019;Ríos-Reyes et al, 2008;Valerio-Mendoza et al, 2019).…”

“…Therefore, the aim of this work is to describe and compare the elements that integrate the female reproductive apparatus, with emphasis on the spermatheca, among Dendroctonus species, clarify its nomenclature, and evaluate its interspecific variation to propose taxonomically useful characteristics for the identification of females. Furthermore, we reconstruct the evolutionary history of the shape of the seminal receptacle (spermatheca sensu Armendáriz-Toledano et al, 2014García-Román et al, 2019;Ríos-Reyes et al, 2007;Valerio-Mendoza et al, 2019) by detecting its phylogenetic signal, thus determining whether there is a structure between the patterns of the shape variation of receptacle and the phylogenetic relatedness of species.…”

Applied Chemical Ecology of the Western Pine Beetle, an Important Pest of Ponderosa Pine in Western North America

“…Dendroctonus barberi Hopkins occurs in eastern Nevad rado, Arizona, New Mexico, and Texas, U.S., and Mexico. We caution the barberi was synonymized with D. brevicomis in 1963 but was reinstated as a cies in 2019 based on differences in morphological characteristics, chemica other factors [10][11][12][13].…”