I. the origin of species by means of natural selection

The ability of a 650 base pair section of the mitochondrial cytochrome c oxidase I (COI) gene to provide species-level identifications has been demonstrated for large taxonomic assemblages of animals such as insects, birds, and fishes, but not for the subphylum Crustacea, one of the most diverse groups of arthropods. In this study, we test the ability of COI to provide identifications in this group, examining two disparate levels in the taxonomic hierarchy — orders and species. The first phase of our study involved the development of a sequence profile for 23 dominant crustacean orders, based upon the analysis of 150 species, each belonging to a different family. The COI amino acid data placed these taxa into cohesive assemblages whose membership coincided with currently accepted boundaries at the order, superorder, and subclass levels. Species-level resolution was subsequently exam- ined in an assemblage of Decapoda and in representatives of the genera Daphnia (Cladocera) and Gammarus (Amphipoda). These studies revealed that levels of nucleotide sequence divergence were from 19 to 48 times greater between congeneric species than between individuals of a species. We conclude that sequence variation in the COI barcode region will be very effective for discriminating species of Crustacea. Resume : Il a ete demontre que l'utilisation d'une section de 650 paires de bases du gene mitochondrial de la cyto- chrome c oxydase I (COI) permet de faire des identifications au niveau specifique de grands ensembles taxonomiques d'animaux tels que les insectes, les oiseaux et les poissons, mais pas encore dans le sous-phylum des crustaces, l'un des groupes les plus diversifies d'arthropodes. Nous testons dans notre etude le potentiel de l'utilisation de COI pour faire des identifications dans ce groupe en examinant deux niveaux disparates de la hierarchie taxonomique — les ordres et les especes. La premiere phase de notre recherche consiste en l'etablissement de profils de sequences pour 23 des ordres principaux de crustaces, d'apres l'analyse de 150 especes, appartenant chacune a une famille differente. Les donnees sur les acides amines de COI permettent de placer ces taxons en ensembles cohesifs dont la composition coincide avec les frontieres couramment acceptees aux niveaux de l'ordre, du super-ordre et de la sous-classe. Nous avons ensuite etudie la determination au niveau specifique chez un ensemble de decapodes et chez des representants des genres Daphnia (Cladocera) et Gammarus (Amphipoda). Ces etudes revelent que les niveaux de divergence des sequences de nucleotides sont de 19 a 48 fois plus importants entre les especes d'un meme genre qu'entre les indivi- dus d'une meme espece. Nous concluons que la variation des sequences dans la region du code-barre de COI devrait permettre de separer de facon tres efficace les especes de crustaces.

/pdf/biological-identifications-through-dna-barcodes-the-case-of-3xog40rbp1.pdf

Biological identifications through DNA barcodes: the case of the Crustacea

Microsatellites are powerful molecular markers, used commonly to estimate intraspecific genetic distances. With the exception of band sharing similarity index, available distance measures were developed specifically for diploid organisms and are unsuited for comparisons of polyploids. Here, we present a simple method for calculation of microsatellite genotype distances, which takes into account mutation processes and permits comparison of individuals with different ploidy levels. This method should provide a valuable tool for intraspecific analyses of polyploid organisms, which are widespread among plants and some animal taxa. An illustration is given using data from the planarian flatworm Schmidtea polychroa (Platyhelminthes).

A simple method for the calculation of microsatellite genotype distances irrespective of ploidy level.

We tested the efficacy of DNA barcodes in identifying mayfly species primarily from the northeastern United States and central Canada. We sequenced a 630-base-pair segment of the mitochondrial gene, cytochrome c oxidase 1 (COI), from 1 individual of each of 80 species to create a reference sequence profile. We used these reference sequences to identify 70 additional specimens representing 32 of the species that were in the profile. DNA barcodes correctly identified 69 of the 70 test specimens. The sole exception was an individual identified morphologically as Maccaffertium modestum that showed deep genetic divergence from other M. modestum specimens. Mean sequence divergence within species was 1%, whereas mean divergence among congeneric species was an order of magnitude greater (18%). We conclude that DNA barcoding can provide a powerful tool for mayfly species identification.

https://www.jstor.org/stable/10.1899/04-142.1

Biological identifications of mayflies (Ephemeroptera) using DNA barcodes

Cladocera is a primarily-freshwater monophyletic group, an important component of the microcrustacean zooplankton. They inhabit most types of continental fresh and saline water habitats, occurring more abundantly in both temporary and permanent stagnant waters. Cladocera is an ancient group of Palaeozoic origin. About 620 species are currently known, but we estimate that the real number of species is 2–4 times higher. A number of currently-recognised widespread species can be expected to harbour extensive cryptic diversity.

/pdf/global-diversity-of-cladocerans-cladocera-crustacea-in-3z6w44maaz.pdf

Global diversity of cladocerans (Cladocera; Crustacea) in freshwater

https://bibliotecadigital.exactas.uba.ar/download/paper/paper_00244082_v140_n2_p171_Adamowicz.pdf

Species diversity and endemism in the Daphnia of Argentina: a genetic investigation

It has long been known that polyploid organisms are more prevalent in arctic than in temperate environments. Past explanations for this geographical trend have focused on the role of glacial cycles in generating polyploids and the influence of abiotic factors in favouring polyploidy in the north. In combination, these mechanisms probably suffice to explain the observed geographical cline in ploidy levels in members of the Daphnia pulex complex in the Holarctic. While only diploid members of the D. pulex complex are found in the temperate regions of North America and Europe, allozyme and DNA quantification analyses indicate that the southern Argentine pulex-complex fauna is dominated by polyploids. Indeed, the present study is the first to document the presence of polyploid members of the D. pulex complex in any temperate climate. The results of phylogeographic analyses suggest that this difference in polyploid distribution between the northern and southern hemispheres is based more on ecological and historical contingencies than direct selection for polyploidy. Specifically, competition with diploid relatives probably limits the lower latitudinal range of polyploids in the north, but appears not to have occurred in Argentina. Because of these differences, the present study provides important insights into the diverse factors that determine the distributions and evolutionary fates of polyploid organisms.

María Cristina Marinone

Papers

Species diversity and endemism in the Daphnia of Argentina: a genetic investigation

New insights into the distribution of polyploid Daphnia: the Holarctic revisited and Argentina explored.

The Hyalella (Crustacea: Amphipoda) species cloud of the ancient Lake Titicaca originated from multiple colonizations.

Aquatic macroinvertebrates from littoral vegetated lakes in arid Patagonia: The influence of fish introduction on community structure