The Paramecium aurelia complex, a group of morphologically similar but sexually incompatible sibling species, is a unique example of the evolutionary plasticity of mating-type systems. Each species has two mating types, O (Odd) and E (Even). Although O and E types are homologous in all species, three different modes of determination and inheritance have been described: genetic determination by Mendelian alleles, stochastic developmental determination, and maternally inherited developmental determination. Previous work in three species of the latter kind have revealed the key roles of the E-specific transmembrane protein mtA and its highly specific transcription factor mtB: type O clones are produced by maternally inherited genome rearrangements that inactivate either mtA or mtB during development. Here we show, through transcriptome analyses in 5 additional species representing the three determination systems, that mtA expression specifies type E in all cases. We further show that the Mendelian system depends on functional and non-functional mtA alleles, and identify novel developmental rearrangements in mtA and mtB which now explain all cases of maternally inherited mating-type determination. Epistasis between these genes likely evolved from less specific interactions between paralogs in the P. aurelia common ancestor, after a whole-genome duplication, but the mtB gene was subsequently lost in three P. aurelia species which appear to have returned to an ancestral regulation mechanism. These results suggest a model accounting for evolutionary transitions between determination systems, and highlight the diversity of molecular solutions explored among sibling species to maintain an essential mating-type polymorphism in cell populations.
During our previous morphological and molecular studies, as well as modelling the environmental niche preferences of the genus Sirthenea Spinola, 1840 (Peiratinae), the distribution of the species S. flavipes (Stål, 1855) became one of the most interesting issues. This species has a very broad distribution range covering the southern part of western, central and eastern Asia. We observed two distinct types of colouration, each also exhibiting a certain degree of variability. Although both colour forms of the studied species show similar variability, the differences between them are so clear that they allow distinction of two populations that are separated by a geographical barrier. Morphology and colour variability are described for representatives of both populations. Genetic studies support the use of the distributional model for individuals in both populations, as well as a characteristic distribution of colour forms. Models which identified potentially suitable habitats based solely on climatic variables are prepared for both populations, as well as for the entire species, and predicted for the Last Glacial Maximum period. An analysis of ecoregions shows that both populations prefer areas with tree vegetation, such as tropical and subtropical moist broadleaf forest biomes. Our studies show morphological divergence of these two discrete populations, reflecting an incipient stage of speciation.
Genus Platymeris Laporte, 1833 is a medium-sized genus belonging to the subfamily Reduviinae, and all known species of these assassin bugs are large-sized insects, distributed exclusively in Africa. Among them, two species, Platymeris biguttatus and Platymeris rhadamanthus, are particularly well known for being bred in commercial cultures. Representatives of both species were bred and crossed in laboratory conditions resulting in interspecific hybrids. The offspring of both species were genetically tested to confirm their hybridisation by nuclear analysis of the wingless gene, which differs in sequence between the parental species. In addition, previous research on the distribution of these species has shown that their ranges partly overlap. This area began to be considered as a potential hybridisation zone. The occurrence of both species was modelled to determine the zone of overlap and estimate the potential hybridisation zone by using the ecological niche modelling technique and MAXENT software. In addition, we tested various model settings and program capabilities. As a result, two large areas were identified as potential hybridisation zones. Both are mostly within the tropical and subtropical moist broadleaf forests ecoregion, as well as tropical and subtropical grasslands, savannas and shrublands ecoregion. In addition, new occurrences of P. rhadamanthus in Namibia have been presented.
Species (or cryptic species) identification in microbial eukaryotes often requires a combined morphological and molecular approach, and if possible, mating reaction tests that confirm, for example, that distant populations are in fact one species. We used P. biaurelia (one of the 15 cryptic species of the P. aurelia complex) collected worldwide from 92 sampling points over 62 years and analyzed with the three above mentioned approaches as a model for testing protistan biogeography hypotheses. Our results indicated that despite the large distance between them, most of the studied populations of P. biaurelia do not differ from each other (rDNA fragment), or differ only slightly (COI mtDNA fragment). These results could suggest that in the past, the predecessors of the present P. biaurelia population experienced a bottleneck event, and that its current distribution is the result of recent dispersal by natural or anthropogenic factors. Another possible explanation for the low level of genetic diversity despite the huge distances between the collecting sites could be a slow rate of mutation of the studied DNA fragments, as has been found in some other species of the P. aurelia complex. COI haplotypes determined from samples obtained during field research conducted in 2015-2016 in 28 locations/374 sampling points in southern Poland were shared with other, often distant P. biaurelia populations. In the Kraków area, we found 5 of the 11 currently known COI P. biaurelia haplotypes. In 5 of 7 reservoirs from which P. biaurelia was obtained, two different COI haplotypes were identified.
Among the 30 known genera within subfamily Peiratinae, only the genusSirtheneahas a cosmopolitan distribution. The results of our studies are the first comprehensive analysis concerning one of the representatives of mentioned subfamily based on joint phylogenetic analyses of molecular and morphological data as well as molecular dating. A total of 32 species were included into the dataset with all known species of the genusSirthenea. Material of over 400 dry specimens was examined for the morphological part of this study. The cosmopolitan distribution ofSirtheneaand the inaccessibility of specimens preserved in alcohol required the extraction of DNA from the dried skeletal muscles of specimens deposited in 24 entomological collections. The oldest specimens used for the successful extraction and sequencing were collected more than 120 years ago in India. We performed Bayesian Inference analyses of molecular and morphological data separately, as well as combined analysis. The molecular and morphological data obtained during our research verify the correlation of the divergence dates of all knownSirtheneaspecies. Results of the relaxed molecular clock analysis of the molecular data show that, the genusSirtheneastarted diverging in the Late Cretaceous into two clades, which subsequently began to branch off in the Paleocene. Our results of phylogenetic analyses suggest that thefossula spongiosaand its development could be one of the most important morphological characters in the evolution of the genus, most likely associated with the ecological niche inhabited bySirthenearepresentatives. Confirmation of the results obtained in our studies is the reconciliation of the evolutionary history ofSirtheneawith the biogeographical processes that have shaped current global distribution of the genus.
Takecallis nigroantennatus Wieczorek sp. nov. (Hemiptera: Aphididae), associated with the cold hardy bamboo variety Fargesia spp. (Bambusoideae), is described and illustrated along with a key to species of the genus Takecallis. The results of a mitochondrial COI (DNA barcoding) and nuclear elongation factor 1 (EF1α) gene sequences, which confirm the genetic difference of the new taxon from the other congeneric species, are provided. The possible way of introduction of this species to Europe is discussed with its new locality from Belgium.
In this paper, the mature larva and pupa of Bagous claudicans are described and illustrated for the first time. Measurements of younger larval instars are also given. The biology of the species is discussed in association with larval morphology and feeding habits. Overall larval and pupal morphological characters of the genus Bagous are presented. Confirmation of the larva identification as Bagous claudicans species was conducted by cytochrome oxidase I (COI) sequencing. DNA barcoding was useful for specimen identification of larval stages. The systematic position of the species within the Bagous collignensis-group, based on morphological and molecular results, is also discussed.
In this paper, a new genus Sabahia Walczak & Gębicki with a new species Sabahia polypodii Walczak & Gębicki within the tribe Nirvanini is described. It originates from Sabah Province on Borneo (Malaysia, Sabah) and is most closely related to Decursusnirvana Gao & Zhang and Sinonirvana Gao & Zhang. It differs from these genera primarily with regard to the morphology of the male genitalia. Although it shows some resemblance to representatives of the genus Chudania Distant in the structure of the aedeagus, it can be clearly separated from this genus by the absence of a median carina from the facial part of the head. Details of the external morphology, as well as those of the male and female genitalia are documented (including scanning microscopy images). In addition, the phylogenetic relationships of several species within the subfamily Evacanthinae and related groups are discussed, based on comparative analyses of the genetic sequences for histone (H3) and the mitochondrial gene of cytochrome oxidase c (COI).
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