Cryptic diversity and multiple origins of the widespread mayfly species group Baetis rhodani (Ephemeroptera: Baetidae) on northwestern Mediterranean islands

Detailed DNA barcoding of mayflies in a small European country proved how far we are from having comprehensive barcode reference libraries

Mayflies (Ephemeroptera) are among the crucial water and habitat quality bioindicators. However, despite their intensive long-term use in various studies, more reliable mayfly DNA barcode data have been produced in a negligible number of countries, and only ~40% of European species had been barcoded with less than 50% of families covered. Despite being carried out in a small area, our study presents the second-most species-rich DNA reference library of mayflies from Europe and the first comprehensive view from an important biodiversity hotspot such as the Western Carpathians. Within 1153 sequences, 76 morphologically determined species were recorded and added to the Barcode of Life Data System (BOLD) database. All obtained sequences were assigned to 97 BINs, 11 of which were unique and three represented species never barcoded before. Sequences of 16 species with high intraspecific variability were divided into 40 BINs, confirming the presence of cryptic lineages. Due to the low interspecific divergence and the non-existing barcoding gap, sequences of six species were assigned to three shared BINs. Delimitation analyses resulted in 79 and 107 putative species respectively. Bayesian and maximum-likelihood phylogenies confirmed the monophyly of almost all species and complexes of cryptic taxa and proved that DNA barcoding distinguishes almost all studied mayfly species. We have shown that it is still sufficient to thoroughly investigate the fauna of a small but geographically important area to enrich global databases greatly. In particular, the insights gained here transcend the local context and may have broader implications for advancing barcoding efforts.

Baetidae (Insecta: Ephemeroptera) of Aurès Mountains (Algeria): A New Species of the Baetis alpinus Species Group, with Notes on Baetis Laech, 1815 Biogeography within Maghreb

A new species, Baetis (Baetis) dihyaesp. nov., belonging to the Baetis alpinus species group, is described and illustrated based on larval material collected in the Aurès Mountains (northeastern Algeria) in 2020-2021. This new species is closely related to three European species, e.g., Baetis (B.) alpinus (Pictet, 1843); B. (B.) nubecularis Eaton, 1898; and B. (B.) pasquetorum Righetti & Thomas, 2002 by the combination of the following characteristics: (i) more than one short, stout bristle at the tip of segment II of the maxillary palp and (ii) a well-developed paracercus. However, the new species clearly differs from all congeners of the Baetis alpinus species group primarily by the (a) structure of mouthparts-with 14-18 long submarginal setae arranged in a single irregular row on the dorsal surface of the labrum; 2-6 short, stout bristles at the tip of segment II of the maxillary palp; and segment II of the labial palp without a considerably developed apico-internal lobe); (b) setation of abdominal terga, with a few triangular-shaped scales sparsely scattered near the posterior margin only; and (c) a well-developed paracercus, comprised of more than 50 segments. Primary data on the biology and distribution of this new species are provided, and molecular affinities are verified by the analysis of COI (barcode) sequences. Detailed notes on the distribution of mayfly species belonging to the Baetis alpinus species group common in Western Europe and the western part of North Africa are presented. The historical movement of Baetis representatives between Europe, North West Africa, and subsequently Algeria, with the land bridges 'Strait of Gibraltar' and 'Strait of Sicily' as colonization routes, is discussed in detail and identified in the present study as the Western Algeria colonization path and Eastern Algeria colonization path, respectively.

CO1 barcodes resolve an asymmetric biphyletic clade for Diabrotica undecimpunctata subspecies and provide nucleotide variants for differentiation from related lineages using real-time PCR

Diabrotica undecimpunctata is a multivoltine polyphagous beetle species that has long been documented as a significant agricultural pest throughout its native range in North America. This beetle can vector bacterial and viral plant pathogens that result in major losses to crops such as cucumber and soybean. Many countries outside the Americas treat D. undecimpunctata as a species of quarantine importance, while in the USA only the subspecies D. u. duodecimnotata is subject to quarantine, to prevent introduction from Mexico. Identification of D. undecimpunctata on the basis of morphology alone can be complicated given the use of conflicting characters in the description of some subspecific taxa. To better understand relationships among D. undecimpunctata subspecies and other related species, we sequenced mitochondrial cytochrome oxidase 1 (CO1) and nuclear internal transcribed spacer 2 (ITS2) DNA from individuals in different subspecific taxa and across different parts of the species range using museum samples and interceptions. When our data were combined with publicly available Diabrotica data, no pattern of divergence consistent with the currently recognized subspecific designations was found. In addition, we compared phylogenetic patterns in CO1 data from the congener D. virgifera to demonstrate the utility of mitochondrial data in resolving subspecies. From the CO1 data, a diagnostic real-time PCR assay was developed that could successfully identify all haplotypes within the large D. undecimpunctata clade for use in surveys and identification at ports of entry. These findings underscore the need to resolve molecular and morphological datasets into cogent, lineage-based groupings. Such efforts will provide an evolutionary context for the study of agriculturally important attributes of Diabrotica such as host preferences, xenobiotic metabolism, and natural and anthropogenic patterns of dispersal.

Reports of Baetidae (Ephemeroptera) species from Tafna Basin, Algeria and biogeographic affinities revealed by DNA barcoding

Background

The Mediterranean basin is known to be the cradle of many endemic species. Within mayflies (Insecta, Ephemeroptera), North African species belonging to the family Baetidae remain poorly known and, traditionally, affinities to European fauna were proposed. Recent studies, based on molecular reconstructions, showed closer relationships to Mediterranean islands fauna.

New information

Baetidae were sampled from North-West Algerian wadis (Tafna basin) and involved in COI barcoding reconstructions. Seven species were identified. The subgenus Rhodobaetis is represented by Baetisatlanticus known previously from Macaronesian islands, Europe and Morocco and the Maghrebian endemic Baetissinespinosus. Specimens, previously identified as Cloeoncf.dipterum, correspond to Cloeonperegrinator and, until now, only reported from Macaronesia. Besides the confirmation of endemicity of some species, such as Procloenstagnicola and B.sinespinosus, our molecular study showed quite original results for relationships between European, insular and Algerian species. Baetismaurus stood out as a North African endemic sister clade to an Iberian clade. Furthermore, we found clear interspecific distances between Algerian and European clades for A.cf.sinaica and B.cf.pavidus, suggesting the presence of cryptic species in Algeria. However, additional studies are needed, as, for the moment, no clear morphological characters were found to separate the different clades and support them as valid species.

Direct analysis of vicariance in Neotropical mayflies (Ephemeroptera)

The distribution of aquatic insects has been poorly explored in quantitative analyses aiming at the historical reconstruction of area relationships in the Neotropics. Ephemeroptera is an ancient group, characterized by its low vagility, and of high richness and endemicity in this region. Systematic knowledge of the group has enormously increased in the last decades, achieving a sufficient background to explore biogeographical historical patterns. Our aim is to reconstruct area history in the Neotropics using the rationale of Barrier biogeography (Hovenkamp protocol). We present eleven mayfly phylogenies, representing groups that evolved independently at least from the Jurassic (i.e., not a one-taxon history). With these groups, we conducted independent biogeographical analyses (using Vicariance Inference Program), and extracted the events that repeated in two or more clades. We found fifty-eight TVEs (Traceable Vicariant Events), from which four were found at least twice, thus constituting SVEs (Supported Vicariant Events).

Fast and accurate identification of cryptic and sympatric mayfly species of the Baetis rhodani group

OBJECTIVE

Species of the Baetis rhodani group are among the most widespread mayflies of the Palearctic region. However, frequent occurrence of morphologically cryptic species complicates the identification of sympatric species. Here, we proposed and tested a method for the fast, accurate, and cost-effective assignment of a large number of individuals to their putative species, based on high resolution melting profiles of a standard mitochondrial gene fragment. We tested this method using a system of three recently identified cryptic species inhabiting the Tyrrhenian Islands (western Mediterranean basin).

RESULTS

Highly species-specific high resolution melting profiles were obtained, allowing the unequivocal attribution of each individual to the respective species. This assay provides a convenient and easily customizable alternative to traditional barcoding approaches, provided that the mayfly taxa occurring within the geographic area of interest have been previously identified and their high resolution melting profiles assessed.

Baetis (Baetis) cypronyx sp. n., a new species of the Baetis alpinus species-group (Insecta, Ephemeroptera, Baetidae) from Cyprus, with annotated checklist of Baetidae in the Mediterranean islands

A detailed description of the larvae of Baetis (Baetis) cypronyxsp. n., a representative of the Baetisalpinus species-group within the mayfly family Baetidae, is provided, including a differential diagnosis with regard to closely related species of the group, especially Baetismelanonyx (Pictet, 1843) and Baetisbaroukianus Thomas & Dia, 1984. The new species is mainly distinguished by mouthparts (i.e. the shape and setation of labrum, maxillary and labial palps, details of paraglossae and mandibular incisors), setation of legs and abdominal terga, and length of paracercus. All available data on the biology of this putative endemic species of Cyprus are summarized. Annotated distributional data of the 33 species of Baetidae so far recorded from the Mediterranean islands are given, including new records and also including first data from Malta.

Cryptic diversity and multiple origins of the widespread mayfly species group Baetis rhodani (Ephemeroptera: Baetidae) on northwestern Mediterranean islands

How the often highly endemic biodiversity of islands originated has been debated for decades, and it remains a fervid research ground. Here, using mitochondrial and nuclear gene sequence analyses, we investigate the diversity, phylogenetic relationships, and evolutionary history of the mayfly Baetis gr. rhodani on the three largest northwestern Mediterranean islands (Sardinia, Corsica, Elba). We identify three distinct, largely co‐distributed, and deeply differentiated lineages, with divergences tentatively dated back to the Eocene–Oligocene transition. Bayesian population structure analyses reveal a lack of gene exchange between them, even at sites where they are syntopic, indicating that these lineages belong to three putative species. Their phylogenetic relationships with continental relatives, together with the dating estimates, support a role for three processes contributing to this diversity: (1) vicariance, primed by microplate disjunction and oceanic transgression; (2) dispersal from the continent; and (3) speciation within the island group. Thus, our results do not point toward a prevailing role for any of the previously invoked processes. Rather, they suggest that a variety of processes equally contributed to shape the diverse and endemic biota of this group of islands.