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Phylogenetic and morphological analyses of Japanese Aquarius water strider, with a new synonym
Abstract
The genus Aquarius, of the subfamily Gerrinae, was formerly divided into two species and one subspecies in Japan (A. paludum paludum, A. paludum amamiensis and A. elongatus, respectively). Aquarius haliplous Yasunaga et al. 2018 has recently been described as a new species, which occurs in brackish waters of Nagasaki Prefecture and is found sympatrically with the widely distributed species, A. p. paludum. However, they are considered to be speciated, with no cross-breeding. In this study, molecular phylogenetic and morphological analyses were undertaken using the mitochondrial DNA COI (529 bp) and nuclear DNA histone H3 (314 bp) gene regions to investigate the genetic and morphological differentiation in the genus Aquarius, including A. haliplous, throughout Japan (including the islands). The results show that, unlike A. p. paludum, A. p. amamiensis and A. haliplous, A. elongatus displays substantial genetic differentiation. Considering that, although morphological differences exist in the antennae of A. p. paludum and A. p. amamiensis, A. haliplous has no clear genetic or morphological difference from A. p. paludum, and hence cannot be classified as a distinct species. Therefore, we propose that A. haliplous be synonymized with A. paludum.
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The Molecular Evolutionary Genetics Analysis (MEGA) software has matured to contain a large collection of methods and tools of computational molecular evolution. Here, we describe new additions that make MEGA a more comprehensive tool for building timetrees of species, pathogens, and gene families using rapid relaxed-clock methods. Methods for estimating divergence times and confidence intervals are implemented to use probability densities for calibration constraints for node-dating and sequence sampling dates for tip-dating analyses, which will be supported by new options for tagging sequences with spatiotemporal sampling information, an expanded interactive Node Calibrations Editor, and an extended Tree Explorer to display timetrees. We have now added a Bayesian method for estimating neutral evolutionary probabilities of alleles in a species using multispecies sequence alignments and a machine learning method to test for the autocorrelation of evolutionary rates in phylogenies. The computer memory requirements for the maximum likelihood analysis are reduced significantly through reprogramming, and the graphical user interface (GUI) has been made more responsive and interactive for very big datasets. These enhancements will improve the user experience, quality of results, and the pace of biological discovery. Natively compiled GUI and command-line versions of MEGA11 are available for Microsoft Windows, Linux, and macOS from www.megasoftware.net.
The evolution of local adaptation is crucial for the in situ persistence of populations in changing environments. However, selection along broad environmental gradients could render local adaptation difficult, and might even result in maladaptation. We address this issue by quantifying fitness trade‐offs (via common garden experiments) along a salinity gradient in two populations of the Neotropical water strider Telmatometra withei—a species found in both fresh (FW) and brackish (BW) water environments across Panama. We found evidence for local adaptation in the FW population in its home FW environment. However, the BW population showed only partial adaptation to the BW environment, with a high magnitude of maladaptation along naturally occurring salinity gradients. Indeed, its overall fitness was ~60% lower than that of the ancestral FW population in its home environment, highlighting the role of phenotypic plasticity, rather than local adaptation, in high salinity environments. This suggests that populations seemingly persisting in high salinity environments might in fact be maladapted, following drastic changes in salinity. Thus, variable selection imposed by salinization could result in evolutionary mismatch, where the fitness of a population is displaced from its optimal environment. Understanding the fitness consequences of persisting in fluctuating salinity environments is crucial to predict the persistence of populations facing increasing salinization. It will also help develop evolutionarily informed management strategies in the context of global change.
A new species of halophilous water strider, Aquarius haliplous Yasunaga, Asanabe, and Nagashima new species (Hemiptera: Gerridae: Gerrinae), is diagnosed and described. This species is endemic to Omura Bay, Nagasaki, southwestern Japan, and has a unique adaptation to this mixohaline habitat. Based on unique morphology and ecology both in the adult and immature forms, this new Aquarius Schellenberg species can be separated unequivocally from a similar species inhabiting freshwater, A. paludum (Fabricius). A key is provided to facilitate identification of the Japanese species and subspecies of Aquarius .
We examined phylogenetic relationships among gerrid water striders of the genus Aquarius Schellenbrg using molecular and morphological characters. The molecular data sets included 780 bp sequence data from the mitochondrial gene encoding cytochrome oxidase subunit I (COI), and 515 bp sequence data from the nuclear gene encoding elongation factor 1 alpha (EF-1 alpha). The morphological data set was a slightly modified version of a previously published data set. We included all 17 known species and one subspecies of Aquarius as well as five species from three related genera, Gigantometra gigas, Limnoporus esakii, L, rufoscutellatus, Gerris pingreensis, and G. lacustris. Unweighted parsimony analyses of the COI data set gave a single most parsimonious tree (MPT) with a topology quite similar to the morphological tree. Parsimony analyses of the EF-1 alpha data set gave 3 MPT's and a strict consensus of these trees gave a tree with a slightly different topology. A combined analysis of the three data sets gave a single MPT with the same topology as for the morphological data set alone. The phylogeny of Aquarius presented here supports the monophyly of the A. najas, remigis, conformis and paludum species groups as well as previous hypotheses about their relationships. On the other hand, the inclusion of molecular data weakens the support for the monophyly of the genus Aquarius, and questions the specific status of the eastern North American A. nebularis (as separate from A. conformis) and members of the Nearctic A. remigis group. Finally, we discuss the implications of the reconstructed phylogeny in the biogeography and ecological phylogenetics of Aquarius.
This study aims, first, to examine the limit for tolerance to lower salinity by an oceanic sea skater, Halobates micans, and , second, to make it clear whether exclusively fresh water Halobatinae species, Metrocoris histrio has salinity tolerance. Adults of H. micans were collected using Neuston Net from the starboard side of R/V MIRAI on a fixed station at 8°S, 80°E, whereas those of M. histrio were collected from a small pond filled with a spring fresh water in Kochi (33°N, 133°E), Japan. Time in survival was measured in starved condition under several salinity conditions: 0‰, 2‰, 4‰, 6‰, 8‰, 9‰ and 10‰ for H. micans; 0‰, 5‰, 10‰, 12.5‰, 15‰ for M. histrio. Half of adults were in coma due to lower salinity under 10‰ and time in survival was less than 10 hours under less than 4‰ for H. micans. Time in survival was half at 5‰ of 80 hours on average at 0‰ as a control and less than 10 hours at 10‰ or higher salinity for M. histrio. Relatively flexible osmo-regulation ability by H. micans would be related to wide variety of salinity condition of surface oceanic water, whereas very limited tolerance even to lower salinity of 5‰ may be permitted by the no chances to be exposed to brackish water in natural habitats of M. histrio. This study showed that salinity tolerance of Halobatinae species would reflect, directly, the salinity condition of their habitats.
The responses of females of the water strider, Aquarius paludum, to changes in NaCl concentration were examined in the laboratory. The insects were sampled seasonally in 2002 and 2003 at two reservoirs in Kochi, Japan, onnected by a waterway, one at the mouth of the river with high NaCl concentrations (the range in NaCl concentration during a year: 0.1 –1.08%) and one 700 m upstream, where the salinity was lower (0.03–0.23%). Sudden increase in NaCl concentration, from 0.45 to 0.9%, after adult strider emergence suppressed reproduction and promoted flight activity, whereas a decrease in salinity did not affect either trait. In the field, A. paludum was univoltine in brackish and multivoltine in freshwater ponds. Thus, the number of breeding periods per year was limited by fluctuations in the NaCl concentration in brackish habitats. Our results suggest that A. paludum can breed in brackish waters when the NaCl concentration is below the limitation for eproduction and growth. Abrupt increases in NaCl concentration caused by seawater surges, such as those following typhoons, can trigger the migration of individuals, which move to areas of lower NaCl concentration and so mix the genes of individuals inhabiting brackish and freshwater bodies.
The water strider Aquarius paludum inhabits the surfaces of a wide variety of freshwater habitats both emporary and permanent. It can also live on the surface brackish-water around river mouths. Exposure to a brackish rather than reshwater environment may affect a range of adult and offspring life-history traits. In a two-stage experiment A. paludum offspring from fresh- (F) and brackish-water (B) populations were obtained and their offspring reared in either a fresh- or brackish-water (0.45% NaCl) environments. The four offspring treatment groups (F-F, F-B, B-F, B-B) varied in terms of the parental and offspring rearing environments. The effect of parental and offspring rearing environment on longevity, fecundity and flight was assessed. Offspring reared in a brackish environment throughout their larval and adult stages had a reduced longevity and egg production. The flight activity of the offspring originated from the brackish-water population was maintained when they were reared in a brackish environment, but inhibited when they were exposed to freshwater. Our results suggest that the life-history strategies depend critically on the degree of salinity in both the current environment and that of their parents.
Estimating genealogical relationships among genes at the population level presents a number of difficulties to traditional methods of phylogeny reconstruction. These traditional methods such as parsimony, neighbour-joining, and maximum-likelihood make assumptions that are invalid at the population level. In this note, we announce the availability of a new software package, TCS, to estimate genealogical relationships among sequences using the method of Templeton et al. (1992) .
When one sex carries the other during some phase of courtship or mating, the associated loading may entail a significant cost to the carrier. This paper presents a series of laboratory experiments designed to identify the costs of mate-carrying in Aquarius remigis. Female A. remigis mate repeatedly and carry each mate for several hours, Dead males and lead weights were used to simulate normal mating and loading associated with mate-carrying, respectively. Females carrying weights equivalent to the weight of an average male showed no detectable reductions in survival, lipid reserves, or foraging success, and maintained themselves on the water surface for more than 10 days without access to resting sites. Weights equivalent to two males were supported for 6.1 +/- 4.9 days. Thus, female A. remigis appear to be ve well adapted to carrying their mates and are unlikely to be near their oad limits when carrying a single mate. However, females carrying males or equivalent weights suffered a significant reduction in maximum mobility (stride length and speed), and an increased risk of predation by frogs (Rana clamitans). Females carrying weights were more susceptible to predation than unburdened females but were less susceptible than females carrying males, suggesting that loading contributes significantly to, but does not fully explain, the increased predation risk. This risk probably results from both reduced mobility due to loading and greater visibility (size). Possible influences of the costs of loading on mating behavior and sexual size dimorphism are discussed.
The six extant species of Limnoporus water striders provide an unusual opportunity to compare allozyme and mitochondrial DNA (mtDNA) divergences with both morphological divergences and information on interspecific hybrid inviability. Parsimony analyses of mtDNA, allozymes, and morphology did not differ greatly, and each data type provided useful information on at least some nodes in the phylogeny. Simultaneous analysis of the combined data gave a better resolved and supported tree than did any single data type. Several measures of hybrid inviability bore no relationship to genetic distances between species, thus demonstrating the poor value of hybrid compatibility as an indicator of phylogenetic relationships. When genetic distances were related to estimates of time of divergence based on fossils, standard molecular clocks for mtDNA and allozymes showed as much as a 10-fold underestimate of absolute time. The phylogeny of Limnoporus allows more rigorous evaluation of several prior hypotheses of ecological or developmental processes in water striders. In particular, the phylogeny supports the evolutionary lability of wing dimorphism, sexual size dimorphism, and local differentiation of ontogenetic traits.
We examined phylogenetic relationships among gerrid water striders of the genus Aquarius Schellenberg using molecular and morphological characters. The molecular data sets included 780 bp sequence data from the mitochondrial gene encoding cytochrome oxidase subunit I (COI), and 515 bp sequence data from the nuclear gene encoding elongation factor I alpha (EF-1α). The morphological data set was a slightly modified version of a previously published data set. We included all 17 known species and one subspecies of Aquarius as well as five species from three related genera, Gigantometra gigas, Limnoporus esakii, L. rufoscutellatus, Gerris pingreensis, and G. lacustris. Unweighted parsimony analyses of the COI data set gave a single most parsimonious tree (MPT) with a topology quite similar to the morphological tree. Parsimony analyses of the EF-1α data set gave 3 MPT's and a strict consensus of these trees gave a tree with a slightly different topology. A combined analysis of the three data sets gave a single MPT with the same topology as for the morphological data set alone. The phylogeny of Aquarius presented here supports the monophyly of the A. najas, remigis, conformis and paludum species groups as well as previous hypotheses about their relationships. On the other hand, the inclusion of molecular data weakens the support for the monophyly of the genus Aquarius, and questions the specific status of the eastern North American A. nebularis (as separate from A. conformis) and members of the Nearctic A. remigis group. Finally, we discuss the implications of the reconstructed phylogeny in the biogeography and ecological phylogenetics of Aquarius.
Zettel, H.: Genetic diversity, species phylogeny and historical biogeography of the Aquarius paludum group (Heteroptera: Gerridae). Insect Syst. Evol. 34: 313-328. Copenhagen, September 2003. ISSN 1399-560X. We investigated genetic diversity and phylogeny of all water strider species assigned to the Aquarius paludum species group on basis of 425 bp DNA sequence data from the mitochond-rial gene encoding cytochrome oxidase subunit I (COI). Parsimony analyses and genetic dis-tances confirmed the taxonomic status of the two recently described species Aquarius lili Polhemus & Polhemus, 1994 from Timor and A. philippinensis Zettel & Ruiz, 2003 from the Philippines as being separate from the widespread Oriental A. adelaidis (Dohrn, 1860). Mole-cular clock estimates suggest that the disjunct zoogeographical pattern among the three species is due to a Pliocene/Pleistocene long-range dispersal, rather than a Mesozoic vicari-ance event as previously suggested. However, when we superimposed the disjunct distribution of Southern Hemisphere representatives of the paludum-group onto their phylogenetic re-lationship, the pattern indicated vicariance events following the break-up of Gondwana.
We examined phylogenetic relationships among halobatine water striders (Hemiptera, Gerridae) using molecular and morphological data. The molecular data set was 780 bp DNA sequence data from the 3′ half of the mitochondria! gene encoding cytochrome oxidase subunit I from 19 species of sea skaters, Halobates, and one species from each of three related genera, Asclepios annandalei, Austrobates rivularis, and Eurymetra natalensis. The morphological data set was a slightly modified version of a previously published data set. Unweighted parsimony analyses of the molecular data set gave one tree with weak support for most branches. Maximum likelihood analysis of the same data set gave a tree with slightly different topology, but reveiled many of the clades found in parsimony analyses of the morphological data set. Parsimony analyses of the combined molecular + morphology data sets gave a better resolved and better supported tree than did analyses of any single data set. The phytogeny of Halobates presented here allows a more rigorous evaluation of several prior hypotheses about evolutionary processes in marine water striders. In particular, it supports the hypothesis of at least two separate transitions from coastal to oceanic environments.
Relatively few insects have invaded the marine environment, and only five species of sea skaters, Halobates Eschscholtz (Hemiptera: Gerridae), have successfully colonized the surface of the open ocean. All five species occur in the
Pacific Ocean, H. germanus White also occurs in the Indian Ocean, whereas H. micans Esch- scholtz is the only species found in the Atlantic Ocean. We sequenced a 780 bp long region of the mitochondrial cytochrome
oxidase subunit I gene (COI) for a total of 66 specimens of the five oceanic Halobates species. Our purpose was to investigate the genetic variation within species and estimate the amount of gene flow between
populations. We defined 27 haplotypes for H. micans and found that haplotype lineages from each of the major oceans occupied by this species are significantly different, having
sequences containing five to seven unique base substitutions. We conclude that gene flow between populations of H. micans inhabiting the Atlantic, Pacific, and Indian Ocean is limited and hypothesize that these populations have been separated
for 1 to 3 million years. Similarly, there may be limited gene flow between H. germanus populations found in the Pacific and Indian Ocean and between H. sericeus populations inhabiting the northern and southern parts of the Pacific Ocean. Finally, we discuss our findings in relation
to recent hypotheses about the influence of oceanic diffusion on the distribution and population structure of oceanic Halobates spp.
The program MRBAYES performs Bayesian inference of
phylogeny using a variant of Markov chain Monte Carlo.
Availability: MRBAYES, including the source code, documentation,
sample data files, and an executable, is available at http://brahms.biology.rochester.edu/software.html.
Contact: johnh{at}brahms.biology.rochester.edu
Analyses of intersexual conflicts of interest over courtship, mating, or mate guarding require an understanding of the physiological costs of sexual interaction. Repeated respirometric measures of energetic expenditure were taken on female Aquarius remigis while unladen and while carrying a mating male, a small metal weight, or a euthanized male. Unladen "cruising" locomotion consumed an average of 334.6 microW of energy (82 J kg-1 m-1); this estimate of the cost of locomotion coincides with measures from voluntarily locomoting arthropods of similar mass and represents the first energetic measure of skating on a water surface. Cruising females carrying males or metal weights consumed 24% and 28% more energy than unladen females, respectively. Females engaged in "escape" locomotion consumed 43% more energy while carrying a male than while unladen. Further, our study shows that premating struggles, and therefore selective mating decisions, are energetically costly. Struggling females consumed an average of 936.6 microW, a 126% increase compared to cruising, nonstruggling females, and 64% more than mating females engaged in escape locomotion. We develop a quantitative model showing that at a certain harassment rate threshold, accepting superfluous matings becomes the "best of a bad job" for females.
We describe "universal" DNA primers for polymerase chain reaction (PCR) amplification of a 710-bp fragment of the mitochondrial cytochrome c oxidase subunit I gene (COI) from 11 invertebrate phyla: Echinodermata, Mollusca, Annelida, Pogonophora, Arthropoda, Nemertinea, Echiura, Sipuncula, Platyhelminthes, Tardigrada, and Coelenterata, as well as the putative phylum Vestimentifera. Preliminary comparisons revealed that these COI primers generate informative sequences for phylogenetic analyses at the species and higher taxonomic levels.
Keywords:cladogram estimation;gene genealogy;phylogeography;population genetics;software
Unlabelled:
RAxML-VI-HPC (randomized axelerated maximum likelihood for high performance computing) is a sequential and parallel program for inference of large phylogenies with maximum likelihood (ML). Low-level technical optimizations, a modification of the search algorithm, and the use of the GTR+CAT approximation as replacement for GTR+Gamma yield a program that is between 2.7 and 52 times faster than the previous version of RAxML. A large-scale performance comparison with GARLI, PHYML, IQPNNI and MrBayes on real data containing 1000 up to 6722 taxa shows that RAxML requires at least 5.6 times less main memory and yields better trees in similar times than the best competing program (GARLI) on datasets up to 2500 taxa. On datasets > or =4000 taxa it also runs 2-3 times faster than GARLI. RAxML has been parallelized with MPI to conduct parallel multiple bootstraps and inferences on distinct starting trees. The program has been used to compute ML trees on two of the largest alignments to date containing 25,057 (1463 bp) and 2182 (51,089 bp) taxa, respectively.
Availability:
icwww.epfl.ch/~stamatak
While the monophyly of winged insects (Pterygota) is well supported, phylogenetic relationships among the most basal extant pterygote lineages are problematic. Ephemeroptera (mayflies) and Odonata (dragonflies) represent the two most basal extant lineages of winged insects, and determining their relationship with regard to Neoptera (remaining winged insects) is a critical step toward understanding insect diversification. A recent molecular analysis concluded that Paleoptera (Odonata Ephemeroptera) is monophyletic. However, we demonstrate that this result is supported only under a narrow range of alignment parameters. We have further tested the monophyly of Paleoptera using additional sequence data from 18SrDNA, 28S rDNA, and Histone 3 for a broader selection of taxa and a wider range of analytical methodologies. Our results suggest that the current suite of molecular data ambiguously resolve the three basal winged insect lineages and do not provide independent confirmation of Odonata + Neoptera as supported via morphological data.
DNA barcoding has been actively used as a method for species identification, and it will become an increasingly important method in the future. However, DNA barcoding can occasionally encounter a major problem, namely “nuclear mitochondrial DNA pseudogenes (NUMTs)”. In this paper, we report the discovery of a pseudogene in the mitochondrial COI region from aquatic heteropterans. PCR with Folmer’s universal primer set produced two different lengths of DNA sequences: a standard 658 bp sequence and a slightly shorter 652 bp sequence. The presence of an “indel” and “stop codon” in the shorter sequence made them separable. We recommend using the “HCOoutout” primer as a downward primer for amplification of the COI region of aquatic heteropterans, especially corixid water bugs.
The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data. In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
This new edition to the classic book by ggplot2 creator Hadley Wickham highlights compatibility with knitr and RStudio. ggplot2 is a data visualization package for R that helps users create data graphics, including those that are multi-layered, with ease. With ggplot2, it's easy to:
• produce handsome, publication-quality plots with automatic legends created from the plot specification
• superimpose multiple layers (points, lines, maps, tiles, box plots) from different data sources with automatically adjusted common scales
• add customizable smoothers that use powerful modeling capabilities of R, such as loess, linear models, generalized additive models, and robust regression
• save any ggplot2 plot (or part thereof) for later modification or reuse
• create custom themes that capture in-house or journal style requirements and that can easily be applied to multiple plots
• approach a graph from a visual perspective, thinking about how each component of the data is represented on the final plot
This book will be useful to everyone who has struggled with displaying data in an informative and attractive way. Some basic knowledge of R is necessary (e.g., importing data into R). ggplot2 is a mini-language specifically tailored for producing graphics, and you'll learn everything you need in the book. After reading this book you'll be able to produce graphics customized precisely for your problems, and you'll find it easy to get graphics out of your head and on to the screen or page. New to this edition:<
• Brings the book up-to-date with ggplot2 1.0, including major updates to the theme system
• New scales, stats and geoms added throughout
• Additional practice exercises
• A revised introduction that focuses on ggplot() instead of qplot()
• Updated chapters on data and modeling using tidyr, dplyr and broom
This study addresses the problem of how insect females make the trade-off between reproduction and longevity when the availability of food varies greatly and when there is poor correlation between the quality of the adult and juvenile environments. The effect of food stress was studied in the waterstrider Gerris thoracicus Schumm. living in Finland mainly in rock pools and brackish water bays. In the laboratory experiments when food was abundant G. thoracicus females had a high reproductive output and a short lifetime. When food was scarce females decreased reproduction and lived longer. When the food ration was varied reproduction followed pulses of food with a time lag of a few days. The food ration used in the experiment had no effect on the longevity of males. The pattern studied in G. thoracicus is likely be an adaptation to unpredictable environments since Gerris lacustris L., an inhabitant of more permanent habitats, responded to food scarcity both with decreased egg production and a shorter lifetime. The conclusion is that G. thoracicus has a more dynamic life-history strategy. It shifts the trade-off in allocation between reproduction and longevity when the food ration changes: During food abundance it has a high reproductive rate at the expense of a reduced life span. During food scarcity it switches off reproduction and is thus able to live longer.
— We studied sequence variation in 16S rDNA in 204 individuals from 37 populations of the land snail Candidula unifasciata (Poiret 1801) across the core species range in France, Switzerland, and Germany. Phylogeographic, nested clade, and coalescence analyses were used to elucidate the species evolutionary history. The study revealed the presence of two major evolutionary lineages that evolved in separate refuges in southeast France as result of previous fragmentation during the Pleistocene. Applying a recent extension of the nested clade analysis (Templeton 2001), we inferred that range expansions along river valleys in independent corridors to the north led eventually to a secondary contact zone of the major clades around the Geneva Basin. There is evidence supporting the idea that the formation of the secondary contact zone and the colonization of Germany might be postglacial events. The phylogeographic history inferred for C. unifasciata differs from general biogeographic patterns of postglacial colonization previously identified for other taxa, and it might represent a common model for species with restricted dispersal.
The insects overwhelm all other organisms of the world in species numbers and diversity. However, there are relatively few insects that inhabit the sea. Most of them are confined to the intertidal zone, with only five species of sea skaters, genus Halobates, having been successful in colonizing the open ocean. We discuss the ecology of both coastal and pelagic Halobates and the closely related genus Asclepios, focusing on their distribution ranges and adaptive strategies to marine environments accompanied by brief discussions of their biology. Updated information on the known localities for three species of Asclepios and some 40 coastal species of Halobates are presented. Many species live in vulnerable coastal habitats exposed to environmental pollution and coastal development. As a case study we trace the historical changes in populations of three Japanese sea skaters, Asclepios shiranui, Halobates matsumurai and H. japonicus, all designated as endangered species. For oceanic Halobates, we present an updated distribution map along with global current systems and sea-surface temperatures, examine interactions between distribution ranges and physical factors at the air–sea interface and discuss spatio-temporal variations in populations of each species. Finally, we infer the life history strategy of oceanic Halobates through theoretical considerations.
While the monophyly of winged insects (Pterygota) is well supported, phylogenetic relationships among the most basal extant pterygote lineages are problematic. Ephemeroptera (mayflies) and Odonata (dragonflies) represent the two most basal extant lineages of winged insects, and determining their relationship with regard to Neoptera (remaining winged insects) is a critical step toward understanding insect diversification. A recent molecular analysis concluded that Paleoptera (Odonata + Ephemeroptera) is monophyletic. However, we demonstrate that this result is supported only under a narrow range of alignment parameters. We have further tested the monophyly of Paleoptera using additional sequence data from 18SrDNA, 28S rDNA, and Histone 3 for a broader selection of taxa and a wider range of analytical methodologies. Our results suggest that the current suite of molecular data ambiguously resolve the three basal winged insect lineages and do not provide independent confirmation of Odonata + Neoptera as supported via morphological data.
The recently-developed statistical method known as the "bootstrap" can be used to place confidence intervals on phylogenies. It involves resampling points from one's own data, with replacement, to create a series of bootstrap samples of the same size as the original data. Each of these is analyzed, and the variation among the resulting estimates taken to indicate the size of the error involved in making estimates from the original data, In the case of phylogenies, it is argued that the proper method of resampling is to keep all of the original species while sampling characters with replacement, under the assumption that the characters have been independently drawn by the systematist and have evolved independently. Majority-rule consensus trees can be used to construct a phylogeny showing all of the inferred monophyletic groups that occurred in a majority of the bootstrap samples. If a group shows up 95% of the time or more, the evidence for it is taken to be statistically significant. Existing computer programs can be used to analyze different bootstrap samples by using weights on the characters, the weight of a character being how many times it was drawn in bootstrap sampling. When all characters are perfectly compatible, as envisioned by Hennig, bootstrap sampling becomes unnecessary; the bootstrap method would show significant evidence for a group if it is defined by three or more characters.
1. We used mtDNA sequence variation to estimate population genetic structure between and among water strider populations of Potamobates williamsi and P. sumaco in the Ecuadorian Amazon.
2. Sequencing of the COI mitochondrial gene revealed 16 haplotypes, which were summarised into four haplotype groups. P. williamsi and P. sumaco shared two common and widespread haplotypes.
3. Population structure was moderate and gene flow was low. Both air and river distances were significantly correlated with gene flow and, thus, indicative of isolation by distance.
4. The genetic structure within and among populations of P. williamsi and P. sumaco was probably not influenced by the dynamic tropical lotic system.
The application of different substitution models to each gene (a.k.a. mixed model) should be considered in model-based phylogenetic analysis of multigene sequences. However, a single molecular evolution model is still usually applied. There are no computer programs able to conduct model selection for multiple loci at the same time, though several recently developed types of software for phylogenetic inference can handle mixed model. Here, I have developed computer software named ‘kakusan’ that enables us to solve the above problems. Major running steps are briefly described, and an analysis of results with kakusan is compared to that obtained with other program.
Abstract. Predation risk associated with the various components of the mating behaviour of the water strider Gerris buenoi are investigated with a series of experiments. Mating behaviour in this species includes frequent harassment of females by males (mate searching), pre-mating struggles that may function as mate choice by females, mating which includes copulation and male mate guarding, and post-mating struggles. Each component of the mating behaviour of females increases predation risk. Escape by females from harassment by males increases the movement rate of females and predacious backswimmers are attracted to movement at the water surface. Capture success of backswimmers is almost tripled on females engaged in pre- and post-mating struggles relative to single females. Because longer pre-mating struggles are one mechanism by which females bias the mating success of male phenotypes in water striders, these data demonstrate that mate choice is costly to females. Finally, mating females are at twice
The aquatic and semi-aquatic Heteroptera, consisting of the infraorders Leptopodomorpha, Gerromorpha, and Nepomorpha, comprise
a significant component of the world’s aquatic insect biota. Within these three infraorders as a whole there are currently
23 families, 343 genera and 4,810 species group taxa considered valid, of which 20 families, 326 genera and 4,656 species
inhabit freshwater. In addition, more than 1,100 unequivocally diagnosed species remain to be described. Aquatic Heteroptera
occur on all continents except Antarctica, and are most numerous in the tropical regions, although there are many distinctly
cold-adapted genera. Overall species richness is highest in the Neotropical and Oriental regions, which harbor 1,289 and 1,103
species, respectively. In comparison to these core tropical regions, species richness is significantly lower in the Afrotropical
(799 species), Australasian (654 species), Palearctic (496 species), Nearctic (424 species) and Pacific (37 species) regions.
Aquatic Heteroptera are notable for utilizing an exceptionally broad range of habitats, from marine and intertidal to arctic
and high alpine, across a global altitudinal range of 0–4,700m. Species may be found in almost every freshwater biotope,
and many exhibit striking morphological adaptations to their aquatic environment, making them excellent subjects for ecological
and biogeographic studies.
Intersexual conflicts over mating decisions may have an important impact on the evolution of mating behaviours and strategies and may develop into an arms race between the sexes. In waterstrider species, where intersexual conflict is known to occur, the evolution of male traits that allow them to overcome female reluctance to mate is expected. Reproductively active waterstriders,Aquarius remigis, were videotaped in the laboratory to examine the influence of total body length and front femoral width of males, male: female body size ratio, and female reproductive condition (number of mature eggs) on three variables associated with mating success: duration of the premating struggle, duration of mating, and number of successful matings. None of these behaviors was significantly correlated with the size ratio of the mating pair. However, total body length was negatively correlated with premating struggle duration, male front femoral width was positively correlated with number of successful matings, and number of mature eggs in females was positively correlated with duration of both the premating struggle and the mating itself. The relative influence of male sexual armaments and female choice on the outcome of mating interactions is discussed.
Conflict between the sexes over mating decision may result in antagonistic coevolution in structures that increase control over copulation. In Aquarius paludum both females and males have long abdominal spines. We tested the hypothesis that abdominal spines increase female ability to resist male mating attempts and reduce the costs of mating in A. paludum. We manipulated female spine length and observed female mating and egg-production rate in two different studies. We found that females with intact spines succeeded to reject male mating attempt more often than females with removed spines. Intact females also mated less often than females with removed or shortened spines. Male presence and mating rate increased female egg number. Our results thus support the hypothesis that abdominal spines help female to reject male mating attempts but contrary to predictions, we found that A. paludum females somehow benefit from multiple matings in spite of the sexual conflict.
Contrary to Bateman’s principle, polyandry appears to be a common female mating strategy. Several hypotheses have been proposed
to explain the evolution of polyandry. It is assumed that females gain either material or genetic benefits from multiple matings,
or that they are coerced into mating by males. In water striders, mating is generally assumed to be costly to females, and
they are thought to mate for reasons of convenience, adjusting their resistance to mating according to male harassment. Here,
we tested the effect of number of matings (with the same male) and number of partners on female fitness in a water strider
Aquarius paludum. In the first experiment, we regulated the time females spent with a male and found that females’ egg production increased
with multiple matings up to a point. The result supports the existence of an optimal female mating frequency. In the second
experiment, we tested how polyandry affects the number of eggs laid and egg hatching success. We conducted three different
trials: females mated four times with either a single male, two different males, or with four different males. Females that
mated with four different males laid the lowest number of eggs and had the lowest egg hatching success, suggesting that polyandry
reduces females’ egg production and egg hatching success in A. paludum. We conclude that A. paludum females probably gain material benefits from mating but no genetic benefits were found in this study.
It has long been recognized that male and female interests in mating may be asymmetrical. The present study quantified experimentally several potential costs and benefits in mating multiply in female water striders, Gerris odontogaster (Zett.). Matings were costly to females, mainly in terms of increased predation risk and time/energy costs involved in carrying passive males. There were no balancing benefits to females in mating multiply. It is concluded that females should theoretically mate approximately every 10th day for maximal survival and fecundity and that multiple matings are not beneficial to females per se. However, females frequently mate several times every day. Several facts suggest that matings are enforced by males at the expense of females' primary interests and that an intersexual conflict over the mating decision exists. However, since a mating male repels copulatory attempts by other males, females may minimize costs by accepting superfluous matings in order to forage relatively undisturbed.
The problem of selecting one of a number of models of different dimensions is treated by finding its Bayes solution, and evaluating the leading terms of its asymptotic expansion. These terms are a valid large-sample criterion beyond the Bayesian context, since they do not depend on the a priori distribution.
The application of maximum likelihood techniques to the estimation of evolutionary trees from nucleic acid sequence data is discussed. A computationally feasible method for finding such maximum likelihood estimates is developed, and a computer program is available. This method has advantages over the traditional parsimony algorithms, which can give misleading results if rates of evolution differ in different lineages. It also allows the testing of hypotheses about the constancy of evolutionary rates by likelihood ratio tests, and gives rough indication of the error of ;the estimate of the tree.
Several stages, from eggs to adults, of the water strider, Aquarius paludum (Fabricius), inhabiting fresh water are sometimes conveyed by heavy flow in the rainy or typhoon seasons in Japan to lotic brackish water in the mouth of rivers. The water striders might then respond to salinity either by remaining to wait for extensive rainfall to reduce osmotic pressure locally before reproducing ("breed here and later tactic") or by flying away to reproduce in fresh waters elsewhere ("breed elsewhere and later tactic"). All first instars died before the first molt when they were exposed to 1.75 and 3.5% NaCl solutions in a laboratory experiment. Living on 0.5 and 0.9% solutions through larval and adult stages slowed down larval growth and suppressed female reproduction. When exposed to the 0.5 and 0.9% solutions, 90 and 92% of males, respectively, showed histolysis of their flight muscles. Therefore, in brackish natural habitats, larvae and adults seem to follow the strategy "breed here and later." When water striders were exposed to 0.9% solution either just after emergence or 20 days later, females showed a higher flight propensity than those kept on fresh waters throughout, and they delayed the deposition of eggs. Therefore, when conveyed to brackish water after emergence by stream flow after heavy rain, adults seem to leave the area by flight, demonstrating the strategy "breed elsewhere and later" tactic. We conclude that water striders use alternative tactics for responding to salinity, depending on the stage of exposure.
The unique natural history, morphology and phylogeny for Aquarius haliplous
- H Asanabe
- A Hirano
- H Momosaka
- T Nagashima
- T Yasunaga
Asanabe H, Hirano A, Momosaka H, Nagashima T,
Yasunaga T (2019) The unique natural history, morphology
and phylogeny for Aquarius haliplous, in Nagasaki prefecture, Kyushu, Japan. Rostria (63), 1-15. (In Japanese.)