Hierarchical comparative analysis of genetic and genitalic geographical structure: testing patterns of male and female genital evolution in the scarab beetle Phyllophaga hirticula (Coleoptera: Scarabaeidae)

DNA Barcoding versus Morphological Variability of Pterostichus brevicornis brevicornis (Kirby, 1837) (Coleoptera, Carabidae) in the Arctic and Subarctic

Simple Summary

Taxonomic studies on a polymorphic species inhabiting a region with relatively uniform environmental conditions (e.g., the Arctic) should involve an integrative approach. Ground beetles such as the subgenus Cryobius of the genus Pterostichus are a successful group in expansion in the tundra biome. The current taxonomy of Cryobius species is unclear and could be considered an obstacle to ecological studies; knowledge of their distribution patterns in the Arctic is rather limited. In this study, the first report on the phylogeography and phylogeny of the most abundant tundra subspecies, P. (Cryobius) brevicornis brevicornis (Kirby, 1837), within its continuous range throughout northern Eurasia and North America is presented. The results indicated that the male genitalia morphology of P. b. brevicornis from Eurasian populations shared a higher geographic variability compared with the pronotum shape and the mitochondrial DNA sequences.

Abstract

The geographic patterns of genetic and morphological variability in ground beetles were examined throughout Northern Eurasia and North America using the most abundant circumpolar tundra subspecies, Pterostichus (Cryobius) brevicornis brevicornis (Kirby, 1837), as a model. Phylogenetic structure was assessed on the basis of a Bayesian approach using two DNA markers (partial sequences of the COI and 28S rRNA genes), while phylogeographic patterns and population genetic diversity were estimated using the COI gene only. Morphological patterns were analysed using elliptical Fourier coefficients that were calculated based on the pronotum and male genitalia shape outlines. The subspecies shares 23 COI haplotypes throughout its entire circumpolar range, while eight haplotypes of 28S rRNA were detected in Northern Eurasia. Phylogenetic analysis did not reveal subdivided species lineages with strict geographical imprint. The network, F_ST and uncorrected pairwise divergence analyses showed that the genetic distances between populations increase by longitude from Northeastern Asia to Europe. The genetic variability among the five studied geographical population groups of P. b. brevicornis was relatively high. The MANOVA showed significant regional divergence between local populations in Northern Eurasia based on both morphological markers, but only male genitalia variability was geographically structured. Neither the pronotum shape nor the male genitalia shape aligned with the phylogeographic patterns discovered on the basis of COI sequences. The genetic (COI) marker had more variation within, rather than among, population groups in addition to morphology of pronotum but not male genitalia.

Molecular phylogeny and species delimitation of the genus Dicerapanorpa (Mecoptera: Panorpidae)

Given that species is the fundamental unit in systematic biology, rigorous species delimitation is crucial for taxonomic studies, yet routine species delimitation remains an ongoing challenge in the taxonomic practice of insects. The two-horned scorpionfly Dicerapanorpa is a small genus in Panorpidae (Mecoptera) endemic to the Qinling-Bashan and Hengduan mountains, a biodiversity hotspot. However, species of Dicerapanorpa are difficult to delineate owing to marked intraspecific variation and interspecific similarity. Here, we investigate the diversity and species boundaries of Dicerapanorpa using an integrative approach based on DNA barcoding, morphological, geometric morphometric and molecular phylogenetic analyses. This integrative analyses confirmed the 13 described species of Dicerapanorpa and revealed three new species: Dicerapanorpa lativalva sp. nov., Dicerapanorpa hualongshana sp. nov. and Dicerapanorpa minshana sp. nov. Most molecular operational taxonomic units are in congruence with morphological clusters. Possible reasons for several discordances in Dicerapanorpa are tentatively discussed.

Molecular phylogeny of Candidula (Geomitridae) land snails inferred from mitochondrial and nuclear markers reveals the polyphyly of the genus

The genus Candidula (Geomitridae), consisting of 28 species in Western Europe as currently described, has a disjunct distribution in the Iberian Peninsula, Italy, the Balkans, the Aegean Islands, and one species on the Canary Islands. Although the genus is seemingly well defined by characters of the reproductive system, the relationships within the genus are still unclear and some authors have indicated a possible subgeneric division based on the internal morphology of the dart sac. Despite substantial phylogenetic incongruence, we present a well-resolved molecular phylogeny of Candidula based on two mitochondrial genes (COI and 16S rRNA), the nuclear rDNA region (5.8S rNRA + ITS2 + 28S rRNA) and seven additional nuclear DNA regions developed specifically for this genus (60SL13, 60SL17, 60SL7, RPL14, 40SS6, 60SL9, 60SL13a), in total 5595 bp. Six reciprocally monophyletic entities including Candidula species were recovered, grouping into two major clades. The incorporation of additional geomitrid genera allowed us to unequivocally demonstrate the polyphyly of the genus Candidula. One major clade grouped species from southern France and Italy with the widely distributed species C. unifasciata. The second major clade grouped all the species from the Iberian Peninsula, including C. intersecta and C. gigaxii. Candidula ultima from the Canary Islands was recovered as separated lineage within the latter clade and related to African taxa. The six monophyla were defined as six new genera belonging to different tribes within the Helicellinae. Thus, we could show that similar structures of the stimulatory apparatus of the genital system in different taxa do not necessarily indicate a close phylogenetic relationship in the Geomitridae. More genera of the family are needed to clarify their evolutionary relationships, and to fully understand the evolution of the stimulatory apparatus of the genital system within the Geomitridae.

Delimiting species using multilocus data: diagnosing cryptic diversity in the southern cavefish, Typhlichthys subterraneus (Teleostei: Amblyopsidae)

A major challenge facing biodiversity conservation and management is that a significant portion of species diversity remains undiscovered or undescribed. This is particularly evident in subterranean animals in which species delimitation based on morphology is difficult because differentiation is often obscured by phenotypic convergence. Multilocus genetic data constitute a valuable source of information for species delimitation in such organisms, but until recently, few methods were available to objectively test species delimitation hypotheses using genetic data. Here, we use recently developed methods for discovering and testing species boundaries and relationships using a multilocus dataset in a widely distributed subterranean teleost fish, Typhlichthys subterraneus, endemic to Eastern North America. We provide evidence that species diversity in T. subterraneus is currently underestimated and that the picture of a single, widely distributed species is not supported. Rather, several morphologically cryptic lineages comprise the diversity in this clade, including support for the recognition of T. eigenmanni. The high number of cryptic species in Typhlichthys highlights the utility of multilocus genetic data in delimiting species, particularly in lineages that exhibit slight morphological disparity, such as subterranean organisms. However, results depend on sampling of individuals and loci; this issue needs further study.

Species delimitation in fungal endophyte diversity studies and its implications in ecological and biogeographic inferences

The estimation of species diversity in fungal endophyte communities is based either on species counts or on the assignment of operational taxonomic units (OTUs). Consequently, the application of different species recognition criteria affects not only diversity estimates but also the ecological hypotheses that arise from those observations. The main objective of the study was to examine how the choice and number of genetic markers and species delimitation criteria influence biodiversity estimates. Here, we compare approaches to defining species boundaries in three dominant species complexes of tropical endophytes, specially Colletotrichum gloeosporioides agg., Pestalotiopsis microspora agg. and Trichoderma harzianum agg., from two Amazonian trees: Hevea brasiliensis and H. guianensis. Molecular tools were used to describe and compare the diversity of the different assemblages. Multilocus phylogenetic analyses [gpd, internal transcribed spacer (ITS) and tef1] and modern techniques for phylogenetic species delimitation were overlaid with ecological data to recognize putative species or OTUs. The results demonstrate that ITS alone generally underestimates the number of species predicted by other nuclear loci. These results question the use of ITS and arbitrary divergence thresholds for species delimitation.