Montane and coastal species diversification in the economically important Mexican grasshopper genus Sphenarium (Orthoptera: Pyrgomorphidae)

Phylogeography of Falagonia mexicana Sharp, 1883 (Coleoptera, Staphylinidae, Aleocharinae)

Falagonia mexicana is an aleocharine distributed from northern Mexico to Guatemala and El Salvador. It is associated with Atta mexicana ants and lives within their piles of waste or external debris. The phylogeography and historical demography of 18 populations from Mexico, Guatemala, and El Salvador were studied. The data set encompasses a 472 bp fragment of the COI. Results suggest that F. mexicana was originated during Middle Pliocene (ca. 0.5 Mya), starting its diversification at the Upper Pleistocene and Holocene. Populations were recovered forming at least four main lineages, with a significant phylogeographic structure. Evidence of contemporary restricted gene flow was found among populations. The historical demography suggests that the geographic structure is due to recent physical barriers (e.g., Isthmus of Tehuantepec) rather than ancient geological events. Also, recent geological and volcanic events in the east of the Trans-Mexican Volcanic Belt and the Sierra Madre Oriental might be responsible for the restricted gene flow among populations. Skyline-plot analyses suggested that a demographic expansion event took place at the end of the Late Quaternary glacial-interglacial cycles.

Multiple introgression events during the diversification history of the edible mexican grasshopper genus sphenarium (orthoptera: pyrgomorphidae)

Speciation with gene flow often leads to ambiguous phylogenetic reconstructions, reticulate patterns of relatedness and conflicting nuclear versus mitochondrial (mt) lineages. Here we employed a fragment of the COI mtDNA gene and nuclear genome-wide data (3RAD) to assess the diversification history of Sphenarium, an orthopteran genus of great economic importance in Mexico that is presumed to have experienced hybridisation events in some of its species. We carried out separate phylogenetic analyses to evaluate the existence of mito-nuclear discordance in the species relationships, and also assessed the genomic diversity and population genomic structure and investigated the existence of interspecific introgression and species limits of the taxa involved based on the nuclear dataset. The species delineation analyses discriminated all the currently recognised species, but also supported the existence of four undescribed species. The mt and nuclear topologies had four discordant species relationships that can be explained by mt introgression, where the mt haplotypes of S. purpurascens appear to have replaced those of S. purpurascens A and B, S. variabile and S. zapotecum. Moreover, our analyses supported the existence of nuclear introgression events between four species pairs that are distributed in the Sierra Madre del Sur province in southeast Mexico, with three of them occurring in the Tehuantepec Isthmus region. Our study highlights the relevance of genomic data to address the relative importance of allopatric isolation versus gene flow in speciation.

Phylogeny and species delimitation of the genus Longgenacris and Fruhstorferiola viridifemorata species group (Orthoptera: Acrididae: Melanoplinae) based on molecular evidence

Phylogenetic positions of the genus Longgenacris and one of its members, i.e. L. rufiantennus are controversial. The species boundaries within both of L. rufiantennus+Fruhstorferiola tonkinensis and F. viridifemorata species groups are unclear. In this study, we explored the phylogenetic positions of the genus Longgenacris and the species L. rufiantennus and the relationships among F. viridifemorata group based on the 658-base fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) barcode and the complete sequences of the internal transcribed spacer regions (ITS1 and ITS2) of the nuclear ribosomal DNA. The phylogenies were reconstructed in maximum likelihood framework using IQ-TREE. K2P distances were used to assess the overlap range between intraspecific variation and interspecific divergence. Phylogenetic species concept and NJ tree, K2P distance, the statistical parsimony network as well as the generalized mixed Yule coalescent model (GMYC) were employed to delimitate the species boundaries in L. rufiantennus+F. tonkinensis and F. viridifemorata species groups. The results demonstrated that the genus Longgenacris should be placed in the subfamily Melanoplinae but not Catantopinae, and L. rufiantennus should be a member of the genus Fruhstorferiola but not Longgenacris. Species boundary delimitation confirmed the presence of oversplitting in L. rufiantennus+F. tonkinensis and F. viridifemorata species groups and suggested that each group should be treated as a single species.

A hyper-diverse genus of acanthocephalans revealed by tree-based and non-tree-based species delimitation methods: Ten cryptic species of Neoechinorhynchus in Middle American freshwater fishes

The genus Neoechinorhynchus represents a hyper-diverse group of acanthocephalans, parasites of fresh and brackish water fish and freshwater turtles, with approximately 116 species described worldwide. Forty-nine species have been recorded in the Americas, nine of them in Middle America. Even though species delimitation methods using DNA sequences have been rarely used for parasitic helminths, the genetic library for species of Neoechinorhynchus has grown in the past few years, enhancing the possibility of using these methods for inferring evolutionary relationships and for establishing more robust species boundaries. In this study, we used non-tree-based and tree-based methods through a coalescent approach to explore the species limits of specimens of Neoechinorhynchus collected in 57 localities across Middle America. We sequenced a large number of individuals to build a comprehensive dataset for three genes: the mitochondrial cytochrome c oxidase subunit I (352 individuals), the internal transcribed spacers (330 individuals), and the D2 + D3 domains of the large subunit (278 individuals). Several species delimitation methods were implemented, i.e., Automatic Barcode Gap Discovery (ABGD), General Mixed Yule-Coalescent Model (GMYC), Bayesian species delimitation (BPP) and species tree (∗BEAST). Additionally, we conducted a detailed morphological study of the diagnostic traits associated with the proboscis of 184 males and 169 females. Overall, our analyses allowed us to validate nine nominal species of Neoechinorhynchus and to identify 10 additional genetic lineages herein regarded as candidate species. This unexpected genetic diversity and the lack of reliable morphological traits show that the genus Neoechinorhynchus includes a group of cryptic species, at least in Middle America.