Abstract
Yumtaax Boucher (Coleoptera: Passalidae) is an endemic genus from the temperate sierras of Mexico and includes six narrowly distributed species. Yumtaax species have been assigned to several genera of Passalidae throughout history, and a phylogenetic approach is necessary to understand species delimitation and interspecific relationships. This study reconstructed the molecular phylogeny of six Yumtaax morphotypes using parsimony and Bayesian analysis of DNA sequence data from the ribosomal nuclear gene region 28S and the mitochondrial gene regions 12S and cytochrome oxidase I (COI) in addition to morphological characters. Analyses recovered two well-supported Yumtaax clades (the Yumtaax laticornis and Yumtaax imbellis clades) that are possible sister lineages. One synapomorphic morphological character state and the geographic isolation of the group provide corroborative evidence for monophyly. Molecular phylogenetic analyses and traditional morphological examinations also resulted in the discovery of two undescribed Yumtaax species and the discovery of two separate evolutionary lineages (cryptic species) within Yumtaax recticornis. As a result we describe three new species (Yumtaax veracrucensis Beza-Beza, Reyes-Castillo & Jameson, sp. n., Yumtaax cameliae Beza-Beza, Reyes-Castillo & Jameson, sp. n., and Yumtaax jimenezi Beza-Beza, Reyes-Castillo & Jameson, sp. n.), redescribe two species (Yumtaax recticornis [Burmeister 1847] and Yumtaax laticornis [Truqui 1857]), and provide a key to all nine Yumtaax species. This study is one of two studies to use molecular data to evaluate the evolutionary relationships of a genus of Bess Beetles (Passalidae), an ecologically important insect group exhibiting low morphological variability and heretofore lacking molecular phylogenetic study.
Highlights
Yumtaax Boucher (Coleoptera: Passalidae: Proculini) is an endemic genus of the southern and eastern Sierra Madre (Boucher 2006)
The morphological characters of the Y. laticornis species group include a short frontal area (Fig. 1B), dorsal mesotibial ridge elevated at the middle (Fig. 2), presence of the infraocular ridge (Fig. 3), and the striatopunctatus-type mesofrontal structure (MFS) (Castillo and Reyes-Castillo 1984)
Morphological character states shared by Yumtaax species (P. laticornis species group + P. recticornis species group [- P. tenuis]) include the short frontal area (Fig. 1A, B) and the dorsal mesotibial ridge elevated at the middle (Boucher 2006)
Summary
Yumtaax Boucher (Coleoptera: Passalidae: Proculini) is an endemic genus of the southern and eastern Sierra Madre (Boucher 2006). Species of Yumtaax are associated with high altitude habitats such as cloud and pine-oak forests (Castillo and Reyes-Castillo 1984, Boucher 2006). Yumtaax species exhibit low morphological variability (Castillo and Reyes-Castillo 1984), rendering a traditional morphological phylogenetic approach of limited utility. A traditional morphological approach in combination with molecular data are needed to define species and reconstruct the phylogeny of the genus. Molecular data have historically proven useful in the family Passalidae (Villatoro 1997, Archila 2009, Beza-Beza et al 2011, Jiménez-Ferbans et al 2016), and these data are essential for species delimitation and phylogeny reconstruction in the absence of strong morphological data. The aims of this study are to: (1) test the monophyly of Yumtaax and (2) reconstruct the phylogenetic relationships among Yumtaax species
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