The ages of cladogenetic events in Coleoptera are frequently estimated with mitochondrial protein-coding genes (MPCGs) and the “standard” mitochondrial nucleotide substitution rate for arthropods. ...This rate has been used for different mitochondrial gene combinations and time scales despite it was estimated on short mitochondrial sequences from few comparisons of close related species. These shortcomings may cause greater impact at deep phylogenetic levels as errors in rates and ages increase with branch lengths. We use the full set of MPCGs of 15 species of beetles (two of them newly sequenced here) to estimate the nucleotide evolutionary rates in a reconstructed phylogeny among suborders, paying special attention to the effect of data partitioning and model choices on these estimations. The optimal strategy for nucleotide data, as measured with Bayes factors, was partitioning by codon position. This retrieved Adephaga as a sister group to Myxophaga with strong support (expected-likelihood weights test 0.94–1) and both sisters to Polyphaga, in contradiction with the most currently accepted views. The hypothesis of Archostemata being sister to the remaining Coleoptera, which is in agreement with morphology, was increasingly supported when third codon sites were recoded or completely removed, sequences were analyzed as AA, and heterogeneous models were implemented but the support levels remained low. Nucleotide substitution rates were strongly affected by the choice of data partitioning (codon position
versus individual genes), with up to sixfold levels of variation, whereas differences in the molecular clock algorithm produced changes of only about 20%. The global mitochondrial protein coding rate using codon partitioning and an estimated age of 250 million years (MY) for the origin of the Coleoptera was 1.34% per branch per MY, which closely matches the ‘standard’ clock of 1.15% per MY. The estimation of the rates on alternative topologies gave similar results. Using local molecular clocks, the evolutionary rate in the Polyphaga and Archostemata was estimated to be nearly twice as fast as in the Adephaga and Myxophaga (1.03%
versus 0.53% per MY). Rates across individual genes varied from 0.55% to 8.61% per MY. Our results suggest that
cox1 might not be an optimal gene for implementing molecular clocks in deep phylogenies for beetles because it shows relatively slow rates at first and second codon positions but very fast rates at third ones. In contrast,
nad5,
nad4 and
nad2 perform better, as they exhibit more homogeneous rates among codon positions.
is widely used as model organism in plant biology. Although not of agronomic significance, it offers important advantages for basic research in genetics and molecular biology including the ...availability of a large number of mutants and genetically modified lines. However, Arabidopsis seed longevity is limited and seeds stored for more than 10 years usually show a very low capacity for germination.
The influence of ultrasonic stimulation was investigated on the germination of
L. seeds. All experiments have been performed using a frequency of 45 kHz at constant temperature (24 °C). No germination rate differences were observed when using freshly collected seeds. However, using artificially deteriorated seeds, our results show that short ultrasonic stimulation (<1 min) significantly increased germination. Ultrasonic stimulation application of 30 s is the optimal treatment. A significant increase in the germination rate was also verified in naturally aged seeds after ultrasonic stimulation. Scanning electron microscopy observations showed an increase in the presence of pores in the seed coat after sonication that may be the cause, at least in part, of the increase in germination. The ultrasound treated seeds developed normally to mature fertile plants.
Ultrasound technology can be used to enhance the germination process of old Arabidopsis seeds without negatively affecting seedling development. This effect seems to be, at least in part, due to the opening of pores in the seed coat. The use of ultrasonic stimulation in Arabidopsis seeds may contribute to the recovering of long time stored lines.
Beetles have colonized water many times during their history, with some of these events involving extensive evolutionary radiations and multiple transitions between land and water. With over 13,000 ...described species, they are one of the most diverse macroinvertebrate groups in most nonmarine aquatic habitats and occur on all continents except Antarctica. A combination of wide geographical and ecological range and relatively accessible taxonomy makes these insects an excellent model system for addressing a variety of questions in ecology and evolution. Work on water beetles has recently made important contributions to fields as diverse as DNA taxonomy, macroecology, historical biogeography, sexual selection, and conservation biology, as well as predicting organismal responses to global change. Aquatic beetles have some of the best resolved phylogenies of any comparably diverse insect group, and this, coupled with recent advances in taxonomic and ecological knowledge, is likely to drive an expansion of studies in the future.
The demand for scientific biodiversity data is increasing, but taxonomic expertise is often limited or not available. DNA sequencing is a potential remedy to overcome this taxonomic impediment. ...Mitochondrial DNA is most commonly used, e.g., for species identification ("DNA barcoding"). Here, we present the first study in arthropods based on a near-complete species sampling of a family-level taxon from the entire Australian region. We aimed to assess how reliably mtDNA data can capture species diversity when many sister species pairs are included. Then, we contrasted phylogenetic subsampling with the hitherto more commonly applied geographical subsampling, where sister species are not necessarily captured.
We sequenced 800 bp cox1 for 1,439 individuals including 260 Australian species (78% species coverage). We used clustering with thresholds of 1 to 10% and general mixed Yule Coalescent (GMYC) analysis for the estimation of species richness. The performance metrics used were taxonomic accuracy and agreement between the morphological and molecular species richness estimation. Clustering (at the 3% level) and GMYC reliably estimated species diversity for single or multiple geographic regions, with an error for larger clades of lower than 10%, thus outperforming parataxonomy. However, the rates of error were higher for some individual genera, with values of up to 45% when very recent species formed nonmonophyletic clusters. Taxonomic accuracy was always lower, with error rates above 20% and a larger variation at the genus level (0 to 70%). Sørensen similarity indices calculated for morphospecies, 3% clusters and GMYC entities for different pairs of localities was consistent among methods and showed expected decrease over distance.
Cox1 sequence data are a powerful tool for large-scale species richness estimation, with a great potential for use in ecology and β-diversity studies and for setting conservation priorities. However, error rates can be high in individual lineages.
The biotas of old islands formed from continental terranes usually have a more complex biogeographical history than those of young oceanic islands, including taxa which have originated by vicariance ...and/or colonisation, over a variety of timescales. The Tyrrhenian Islands of Corsica, Sardinia and the Tuscan Archipelago in the Mediterranean have a complex geological history, shaped by interactions between the African and Eurasian plates since the Mesozoic. Our understanding of the historical biogeography of Tyrrhenian endemics remains limited for many groups, including freshwater invertebrates. Here we use a time-calibrated phylogeny, derived from mitochondrial and nuclear DNA sequence data, to explore the evolutionary history of Tyrrhenian endemic
Hydraena
water beetles, an ecologically important group in the islands’ streams. Whilst no endemic
Hydraena
appear to date from the initial separation of Corsica-Sardinia from the European mainland in the Oligocene, we show that Tyrrhenian species stem from five colonisation events, occurring at different intervals in the last ca. 15 Ma, at least two endemic lineages apparently arising through isolation at the end of the Messinian Salinity Crisis.
Hydraena reflexa
Rey, 1884, long considered a geographical form or subspecies of the widespread
H. pygmaea
Waterhouse, 1833, is reinstated as a valid species, endemic to Corsica and Sardinia.
H. reflexa
can be distinguished from
H. pygmaea
on external and aedeagal characters, documented here in detail. Specimens of ‘
H. reflexa
’ from southern continental Italy are shown to differ from those on Corsica and Sardinia, having identical male genitalia to
H. pygmaea
from elsewhere in its range. Genetically, this Calabrian form also clusters with
H. pygmaea
, and may have arisen through past introgression between a
reflexa
-like ancestor and
H. pygmaea
following the connection of the Calabrian block with the nascent Apennines in the Pliocene. The degree of genetic divergence seen between
H. pygmaea
and
H. reflexa
suggests that they diverged approximately 5.5 Ma in the Miocene, following the isolation of Corsico-Sardinian and mainland populations at the end of the Messinian.
Why some species are widespread while others are very restricted geographically is one of the most basic questions in biology, although it remains largely unanswered. This is particularly the case ...for groups of closely related species, which often display large differences in the size of the geographical range despite sharing many other factors due to their common phylogenetic inheritance. We used ten lineages of aquatic Coleoptera from the western Palearctic to test in a comparative framework a broad set of possible determinants of range size: species' age, differences in ecological tolerance, dispersal ability and geographic location.
When all factors were combined in multiple regression models between 60-98% of the variance was explained by geographic location and phylogenetic signal. Maximum latitudinal and longitudinal limits were positively correlated with range size, with species at the most northern latitudes and eastern longitudes displaying the largest ranges. In lineages with lotic and lentic species, the lentic (better dispersers) display larger distributional ranges than the lotic species (worse dispersers). The size of the geographical range was also positively correlated with the extent of the biomes in which the species is found, but we did not find evidence of a clear relationship between range size and age of the species.
Our findings show that range size of a species is shaped by an interplay of geographic and ecological factors, with a phylogenetic component affecting both of them. The understanding of the factors that determine the size and geographical location of the distributional range of species is fundamental to the study of the origin and assemblage of the current biota. Our results show that for this purpose the most relevant data may be the phylogenetic history of the species and its geographical location.
We examined the responses of sound-treated arabidopsis adult plants to water deprivation and the associated changes on gene expression. The survival of drought-induced plants was significantly higher ...in the sound treated plants (24,8%) compared with plants kept in silence (13,3%). RNA-seq revealed significant upregulation of 87 genes including 32 genes involved in abiotic stress responses, 31 involved in pathogen responses, 11 involved in oxidation-reduction processes, 5 involved in the regulation of transcription, 2 genes involved in protein phosphorylation/dephosphorylation and 13 involved in jasmonic acid or ethylene synthesis or responses. In addition, 2 genes involved in the responses to mechanical stimulus were also induced by sound, suggesting that touch and sound have at least partially common perception and signaling events.
The evolution of the coleopteran suborder Adephaga is discussed based on a robust phylogenetic background. Analyses of morphological characters yield results nearly identical to recent molecular ...phylogenies, with the highly specialized Gyrinidae placed as sister to the remaining families, which form two large, reciprocally monophyletic subunits, the aquatic Haliplidae + Dytiscoidea (Meruidae, Noteridae, Aspidytidae, Amphizoidae, Hygrobiidae, Dytiscidae) on one hand, and the terrestrial Geadephaga (Trachypachidae + Carabidae) on the other. The ancestral habitat of Adephaga, either terrestrial or aquatic, remains ambiguous. The former option would imply two or three independent invasions of aquatic habitats, with very different structural adaptations in larvae of Gyrinidae, Haliplidae and Dytiscoidea.
This study presents the largest set of morphological characters of adults and immature stages ever compiled for the coleopteran suborder Adephaga.
Analyses of the morphological characters yield results nearly identical to recent analyses of molecular data, suggesting that a stable phylogeny has been achieved.
The character transformation on the phenotypic level is reconstructed using a formal approach for the first time, based on the robust phylogenetic pattern and mesquite.
Beetles represent almost one-fourth of all described species, and knowledge about their relationships and evolution adds to our understanding of biodiversity. We performed a comprehensive ...phylogenetic analysis of Coleoptera inferred from three genes and nearly 1900 species, representing more than 80% of the world's recognized beetle families. We defined basal relationships in the Polyphaga supergroup, which contains over 300,000 species, and established five families as the earliest branching lineages. By dating the phylogeny, we found that the success of beetles is explained neither by exceptional net diversification rates nor by a predominant role of herbivory and the Cretaceous rise of angiosperms. Instead, the pre-Cretaceous origin of more than 100 present-day lineages suggests that beetle species richness is due to high survival of lineages and sustained diversification in a variety of niches.
We describe a new subterranean species of the genus
Exocelina
Broun, 1886 (Coleoptera: Dytiscidae) from the Malay Peninsula. Almost all of the 196 species of that genus are epigean and distributed ...mainly in New Guinea, Australia, Oceania and New Caledonia. One epigean species is, however, known from China. The discovery of a species on the Malay Peninsula fills that distribution gap to some degree.
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