PeerJ Preprints: Entomologyhttps://peerj.com/preprints/index.atom?journal=peerj&subject=1300Entomology articles published in PeerJ PreprintsAntibiosis effects of rice carrying Bph14 and Bph15 on the brown planthopper, Nilaparvata lugenshttps://peerj.com/preprints/279602019-09-142019-09-14Liangmiao QiuWuqi WangLongqing ShiQiquan LiuZhixiong Zhan
The brown planthopper (BPH), Nilaparvata lugens, is the most destructive insect pest in rice production worldwide. The development and cultivation of BPH-resistant varieties is the most economical and efficient strategy to overcome the destruction caused by BPH. In this study, the modified bulk seedling test method was used to identify the BPH resistance level and host feeding choice of rice lines of Liangyou8676 (Bph14/Bph15), Bph68S (Bph14/Bph15), RHT (Bph3), Fuhui676, and TN1 on BPH. Meanwhile, the population, survival and emergence rate, developmental duration, honeydew excretion, female ratio and brachyptery ratio of adults were used as indicators to detect the antibiosis effects of the different rice lines. The results showed that the resistance levels of Rathu Heenati (RHT), Bph68S, Liangyou8676, Fuhui676, and TN1 to BPH were HR, R, MR, S and HS, respectively. The host choice implied that BPH was more inclined to feeding on rice plants with a lower resistance. An analysis of the antibiosis activity of rice lines RHT, BPh68S, and Liangyou8676 carrying resistance genes indicated a significant reduction in the population growth rate, survival and emergence rate of BPH nymphs, significant delay in the developmental duration of nymphs, reduced honeydew excretion of females, decreased female ratio, and a decreased brachyptery ratio of females and males, when compared with rice carrying no BPH-resistant genes.
The brown planthopper (BPH), Nilaparvata lugens, is the most destructive insect pest in rice production worldwide. The development and cultivation of BPH-resistant varieties is the most economical and efficient strategy to overcome the destruction caused by BPH. In this study, the modified bulk seedling test method was used to identify the BPH resistance level and host feeding choice of rice lines of Liangyou8676 (Bph14/Bph15), Bph68S (Bph14/Bph15), RHT (Bph3), Fuhui676, and TN1 on BPH. Meanwhile, the population, survival and emergence rate, developmental duration, honeydew excretion, female ratio and brachyptery ratio of adults were used as indicators to detect the antibiosis effects of the different rice lines. The results showed that the resistance levels of Rathu Heenati (RHT), Bph68S, Liangyou8676, Fuhui676, and TN1 to BPH were HR, R, MR, S and HS, respectively. The host choice implied that BPH was more inclined to feeding on rice plants with a lower resistance. An analysis of the antibiosis activity of rice lines RHT, BPh68S, and Liangyou8676 carrying resistance genes indicated a significant reduction in the population growth rate, survival and emergence rate of BPH nymphs, significant delay in the developmental duration of nymphs, reduced honeydew excretion of females, decreased female ratio, and a decreased brachyptery ratio of females and males, when compared with rice carrying no BPH-resistant genes.Phylogeny of Libellulidae: are there relationships between molecular phylogenetics and morphological analysis of wing shape of dragonflies?https://peerj.com/preprints/279582019-09-122019-09-12Shu T HuangHai R WangWan Q YangYa C SiYu T WangMeng L SunXin QiYi Bai
Background: Establishing the species limits and resolving phylogenetic relationships are primary goals of taxonomists and evolutionary biologists. At present, a controversial question is about interspecific phylogenetic information in morphological features. Are the interspecific relationships established based on genetic information consistent with the traditional classification system? To address these problems, this study analyzed the wing shape structure of 10 species of Libellulidae, explored the relationship between wing shape and dragonfly behavior and living habits, and established an interspecific morphological relationship tree based on wing shape data. By analyzing the sequences of mitochondrial COI gene and the nuclear genes 18S, 28S rRNA and ITS in 10 species of dragonflies, the interspecific relationship was established. Method: The wing shape information of the male forewings and hindwings was obtained by the geometric morphometrics method. The inter-species wing shape relationship was obtained by principal component analysis (PCA) in MorphoJ1.06 software. The inter-species wing shape relationship tree was obtained by cluster analysis (UPGMA) using Mesquite3.2 software. The COI, 18S, ITS and 28S genes of 10 species dragonfly were blasted and processed by BioEdit v6 software. The maximum parsimony (MP) tree was established by Puap4.0 software. The Bayes inference (BI) tree was established by MrBayes 3.2.6 in Geneious software. Results: The main difference in forewings among the 10 species of dragonfly was the apical, radial and discoidal regions dominated by the wing nodus. In contrast, the main difference among the hindwings was the apical and anal regions dominated by the wing nodus. The change in wing shape was closely related to the ability of dragonfly to migrate. The interspecific relationship based on molecular data showed that the species of Orthetrum genus branched independently of the other species. Compared to the molecular tree of 10 species, the wing shape clustering showed some phylogenetic information on the forewing shape (with large differences in the forewing shape tree vs. molecular tree), and there was no interspecific phylogenetic information of the hindwing shape tree vs. molecular tree. Conclusion: The dragonfly wing shape characteristics are closely related to its migration ability. Species with strong ability to migrate have the forewing shape that is longer and narrower, and have larger anal region, whereas the species that prefer short-distance hovering or standing still for a long time have forewing that are wider and shorter, and the anal region is smaller. Integrating morphological and molecular data to evaluate the relationship among dragonfly species shows there is some interspecific phylogenetic information in the forewing shape and none in the hindwing shape. The various regions of the forewing and hindwing are inconsistent, which may be due to their different functions.
Background: Establishing the species limits and resolving phylogenetic relationships are primary goals of taxonomists and evolutionary biologists. At present, a controversial question is about interspecific phylogenetic information in morphological features. Are the interspecific relationships established based on genetic information consistent with the traditional classification system? To address these problems, this study analyzed the wing shape structure of 10 species of Libellulidae, explored the relationship between wing shape and dragonfly behavior and living habits, and established an interspecific morphological relationship tree based on wing shape data. By analyzing the sequences of mitochondrial COI gene and the nuclear genes 18S, 28SrRNA and ITS in 10 species of dragonflies, the interspecific relationship was established. Method: The wing shape information of the male forewings and hindwings was obtained by the geometric morphometrics method. The inter-species wing shape relationship was obtained by principal component analysis (PCA) in MorphoJ1.06 software. The inter-species wing shape relationship tree was obtained by cluster analysis (UPGMA) using Mesquite3.2 software. The COI, 18S, ITS and 28S genes of 10 species dragonfly were blasted and processed by BioEdit v6 software. The maximum parsimony (MP) tree was established by Puap4.0 software. The Bayes inference (BI) tree was established by MrBayes 3.2.6 in Geneious software. Results: The main difference in forewings among the 10 species of dragonfly was the apical, radial and discoidal regions dominated by the wing nodus. In contrast, the main difference among the hindwings was the apical and anal regions dominated by the wing nodus. The change in wing shape was closely related to the ability of dragonfly to migrate. The interspecific relationship based on molecular data showed that the species of Orthetrum genus branched independently of the other species. Compared to the molecular tree of 10 species, the wing shape clustering showed some phylogenetic information on the forewing shape (with large differences in the forewing shape tree vs. molecular tree), and there was no interspecific phylogenetic information of the hindwing shape tree vs. molecular tree. Conclusion: The dragonfly wing shape characteristics are closely related to its migration ability. Species with strong ability to migrate have the forewing shape that is longer and narrower, and have larger anal region, whereas the species that prefer short-distance hovering or standing still for a long time have forewing that are wider and shorter, and the anal region is smaller. Integrating morphological and molecular data to evaluate the relationship among dragonfly species shows there is some interspecific phylogenetic information in the forewing shape and none in the hindwing shape. The various regions of the forewing and hindwing are inconsistent, which may be due to their different functions.Ooctonus vulgatus (Hymenoptera, Mymaridae), a potential biocontrol agent to reduce populations of Philaenus spumarius (Hemiptera, Aphrophoridae) the main vector of Xylella fastidiosa in Europehttps://peerj.com/preprints/279412019-09-072019-09-07Xavier MesminMarguerite ChartoisGuenaelle GensonJean-Pierre RossiAstrid CruaudJean-Yves Rasplus
As vector of Xylella fastidiosa (Wells, 1987) in Europe, the meadow spittlebug, Philaenus spumarius (Linnaeus, 1758) (Hemiptera: Aphrophoridae) is a species of major concern. Therefore, tools and agents to control this ubiquitous insect that develops and feeds on hundreds of plant species are wanted. We conducted a field survey of P. spumarius eggs in Corsica and provide a first report of Ooctonus vulgatus Haliday, 1833 (Hymenoptera, Mymaridae) as a potential biocontrol agent of P. spumarius in Europe. To allow species identification, we summarized the main characters distinguishing O. vulgatus from other European species of Ooctonus and generated COI DNA barcodes. We also assessed parasitism rates in several sampling sites, highlighting the top-down impact of O. vulgatus on populations of P. spumarius. Based on the geographic occurrences of O. vulgatus mined in the literature, we calibrated an ecological niche model to assess its potential distribution in the Holarctic. Our results showed that O. vulgatus potential distribution overlaps that of P. spumarius. Hence, O. vulgatus appears to be a promising biocontrol agent of the meadow spittlebug in Europe and it seems advisable to conduct research on this small parasitoid wasp to assess whether it could contribute to reduce the spread and impact of X. fastidiosa in Europe.
As vector of Xylella fastidiosa (Wells, 1987) in Europe, the meadow spittlebug, Philaenus spumarius (Linnaeus, 1758) (Hemiptera: Aphrophoridae) is a species of major concern. Therefore, tools and agents to control this ubiquitous insect that develops and feeds on hundreds of plant species are wanted. We conducted a field survey of P. spumarius eggs in Corsica and provide a first report of Ooctonus vulgatus Haliday, 1833 (Hymenoptera, Mymaridae) as a potential biocontrol agent of P. spumarius in Europe. To allow species identification, we summarized the main characters distinguishing O. vulgatus from other European species of Ooctonus and generated COI DNA barcodes. We also assessed parasitism rates in several sampling sites, highlighting the top-down impact of O. vulgatus on populations of P. spumarius. Based on the geographic occurrences of O. vulgatus mined in the literature, we calibrated an ecological niche model to assess its potential distribution in the Holarctic. Our results showed that O. vulgatus potential distribution overlaps that of P. spumarius. Hence, O. vulgatus appears to be a promising biocontrol agent of the meadow spittlebugin Europe and it seems advisable to conduct research on this small parasitoid wasp to assess whether it could contribute to reduce the spread and impact of X. fastidiosa in Europe.Complex landscape topography can facilitate local adaptation during a range shifthttps://peerj.com/preprints/278992019-08-142019-08-14Robert N. FittLesley T. Lancaster
Warming climates provide many species the opportunity to colonise newly-suitable regions at higher latitudes and elevations. Despite becoming warmer, higher latitudes and elevations nevertheless offer novel climatic challenges, such as greater thermal variability and altered frequency of weather events, and these challenges exert selection on expanding populations. However, high gene flow and genetic drift during the expansion phase may limit the degree to which species can adapt to novel climatic conditions at the range front. Here we examine how landscape topographic complexity influences the opportunity for local adaptation to novel conditions during a range shift. Using RAD-seq data, we investigated whether elevation, latitude, climatic niche differentiation, and gene flow across a complex landscape were associated with signatures of adaptation during recent range expansion of the damselfly Ischnura elegans in Northeast Scotland. Our data revealed two distinct routes of colonisation, with admixture between these routes resulting in increased heterozygosity and population density. Expansion rates, assessed as directional rates of gene flow, were greater between more climatically similar sites than between climatically divergent sites. Significant genetic structure and allelic turnover was found to emerge near the range front at sites characterised by high elevation, low directional gene flow, and high spatial differentiation in climate regimes. This predictive combination of factors suggests that landscape complexity may be a prerequisite for promoting differentiation of populations, and providing opportunities for local adaptation, during rapid or contemporary range shifts.
Warming climates provide many species the opportunity to colonise newly-suitable regions at higher latitudes and elevations. Despite becoming warmer, higher latitudes and elevations nevertheless offer novel climatic challenges, such as greater thermal variability and altered frequency of weather events, and these challenges exert selection on expanding populations. However, high gene flow and genetic drift during the expansion phase may limit the degree to which species can adapt to novel climatic conditions at the range front. Here we examine how landscape topographic complexity influences the opportunity for local adaptation to novel conditions during a range shift. Using RAD-seq data, we investigated whether elevation, latitude, climatic niche differentiation, and gene flow across a complex landscape were associated with signatures of adaptation during recent range expansion of the damselfly Ischnura elegans in Northeast Scotland. Our data revealed two distinct routes of colonisation, with admixture between these routes resulting in increased heterozygosity and population density. Expansion rates, assessed as directional rates of gene flow, were greater between more climatically similar sites than between climatically divergent sites. Significant genetic structure and allelic turnover was found to emerge near the range front at sites characterised by high elevation, low directional gene flow, and high spatial differentiation in climate regimes. This predictive combination of factors suggests that landscape complexity may be a prerequisite for promoting differentiation of populations, and providing opportunities for local adaptation, during rapid or contemporary range shifts.Interspecific differences of stridulatory signals in three species of bark beetles from the genus Polygraphus Er. (Coleoptera: Curculionidae, Scolytinae) inhabiting the island of Sakhalinhttps://peerj.com/preprints/276972019-07-242019-07-24Ivan Andreevich Kerchev
Stridulatory signals are involved in conspecific interactions between bark beetles (Coleoptera: Curculionidae, Scolytinae). In this study, we compared the qualitative profiles of acoustic signals in three species from the genus Polygraphus Er. Sympatry can be periodically observed in two of them – P. proximus and P. subopacus. Sporadically they occur on the same plants. P. nigrielytris colonize distinctly different host plant species; however, on the island of Sakhalin it inhabits the same biotopes. The purpose of the study is to identify species-specific parameters and the extent of differences in stridulatory signals of these species. Airborne signals produced during the contact of males of the same species were experimentally recorded. Among tested parameters of stridulatory signals, as the most species-specific were noted: chirp duration, number of tooth-strikes per chirp, and intertooth-strike interval.
Stridulatory signals are involved in conspecific interactions between bark beetles (Coleoptera: Curculionidae, Scolytinae). In this study, we compared the qualitative profiles of acoustic signals in three species from the genus Polygraphus Er. Sympatry can be periodically observed in two of them – P. proximus and P. subopacus. Sporadically they occur on the same plants. P. nigrielytris colonize distinctly different host plant species; however, on the island of Sakhalin it inhabits the same biotopes. The purpose of the study is to identify species-specific parameters and the extent of differences in stridulatory signals of these species. Airborne signals produced during the contact of males of the same species were experimentally recorded. Among tested parameters of stridulatory signals, as the most species-specific were noted: chirp duration, number of tooth-strikes per chirp, and intertooth-strike interval.Absence of complementary sex determination in Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae)https://peerj.com/preprints/278712019-07-242019-07-24Quan-quan LiuJin-cheng ZhouChen ZhangQian-jin DongSu-fang NingDong Hui
Over 60 species in Hymenoptera have been reported to possess a complementary sex determination (CSD) system. Under CSD, sex is determined by allelic complementation at one or several sex loci. But this mechanism is still uninvestigated in parasitoid wasp Trichogramma dendrolimi, one of the most important biocontrol agents widely used against Lepidopteran pests. We tested CSD in this species by conducting ten consecutive generations of inbreeding, to monitor both direct evidence (diploid male production) and indirect evidence (brood size, sex ratio, mortality). In total 475 males detected from this inbreeding regime, only one was determined as diploidy. The observed proportions of diploid male offspring significantly differed from expected values under CSD model involving up to ten independent loci, allowing us to safely reject CSD in T. dendrolimi. Meanwhile, the possibility of unviable diploid males was excluded by the absence of significant differences in brood size, offspring sex ratio and offspring mortality among different generations. Our study of sex determination in T. dendrolimi provides useful information for the mass rearing conditions in a biofactory and the quality improvement of this biocontrol agent. It also brings necessary background to further study of the sex determination in Trichogramma.
Over 60 species in Hymenoptera have been reported to possess a complementary sex determination (CSD) system. Under CSD, sex is determined by allelic complementation at one or several sex loci. But this mechanism is still uninvestigated in parasitoid wasp Trichogrammadendrolimi, one of the most important biocontrol agents widely used against Lepidopteran pests. We tested CSD in this species by conducting ten consecutive generations of inbreeding, to monitor both direct evidence (diploid male production) and indirect evidence (brood size, sex ratio, mortality). In total 475 males detected from this inbreeding regime, only one was determined as diploidy. The observed proportions of diploid male offspring significantly differed from expected values under CSD model involving up to ten independent loci, allowing us to safely reject CSD in T. dendrolimi. Meanwhile, the possibility of unviable diploid males was excluded by the absence of significant differences in brood size, offspring sex ratio and offspring mortality among different generations. Our study of sex determination in T. dendrolimi provides useful information for the mass rearing conditions in a biofactory and the quality improvement of this biocontrol agent. It also brings necessary background to further study of the sex determination in Trichogramma.Validation of COI metabarcoding primers for terrestrial arthropodshttps://peerj.com/preprints/278012019-07-152019-07-15Vasco ElbrechtThomas WA BraukmannNatalia V IvanovaSean WJ ProsserMehrdad HajibabaeiMichael WrightEvgeny V ZakharovPaul DN HebertDirk Steinke
Metabarcoding can rapidly determine the species composition of bulk samples and thus aids ecosystem assessment. However , it is essential to use primer sets that minimize amplification bias among taxa to maximize species recovery. Despite this fact, the performance of primer sets employed for metabarcoding terrestrial arthropods has not been sufficiently evaluated. Thus this study tests the performance of 36 primer sets on a mock community containing 374 species. Amplification success was assessed with gradient PCRs and the 21 most promising primer sets selected for metabarcoding. These 21 primer sets where also tested by metabarcoding a Malaise trap sample. We identified eight primer sets, mainly those including inosine and/or high degeneracy, that recovered more than 95% of the species in the mock community. Results from the Malaise trap sample were congruent with the mock community, but primer sets generating short amplicons produced potential false positives. Taxon recovery from the 21 amplicon pools of the mock community and Malaise trap sample were used to select four primer sets for metabarcoding evaluation at different annealing temperatures (40-60 Co) using the mock community. Temperature did only have a minor effect on taxa recovery that varied with the specific primer pair. This study reveals the weak performance of some primer sets employed in past studies. It also demonstrated that certain primer sets can recover most taxa in a diverse species assemblage. Thus there is no need to employ several primer sets targeting the same amplicon. While we identified several suited primer sets for arthropod metabarcoding, the primer selection depends on the targeted taxonomic groups, as well as DNA quality, desired taxonomic resolution, and sequencing platform employed for analysis.
Metabarcoding can rapidly determine the species composition of bulk samples and thus aids ecosystem assessment. However , it is essential to use primer sets that minimize amplification bias among taxa to maximize species recovery. Despite this fact, the performance of primer sets employed for metabarcoding terrestrial arthropods has not been sufficiently evaluated. Thus this study tests the performance of 36 primer sets on a mock community containing 374 species. Amplification success was assessed with gradient PCRs and the 21 most promising primer sets selected for metabarcoding. These 21 primer sets where also tested by metabarcoding a Malaise trap sample. We identified eight primer sets, mainly those including inosine and/or high degeneracy, that recovered more than 95% of the species in the mock community. Results from the Malaise trap sample were congruent with the mock community, but primer sets generating short amplicons produced potential false positives. Taxon recovery from the 21 amplicon pools of the mock community and Malaise trap sample were used to select four primer sets for metabarcoding evaluation at different annealing temperatures (40-60 Co) using the mock community. Temperature did only have a minor effect on taxa recovery that varied with the specific primer pair. This study reveals the weak performance of some primer sets employed in past studies. It also demonstrated that certain primer sets can recover most taxa in a diverse species assemblage. Thus there is no need to employ several primer sets targeting the same amplicon. While we identified several suited primer sets for arthropod metabarcoding, the primer selection depends on the targeted taxonomic groups, as well as DNA quality, desired taxonomic resolution, and sequencing platform employed for analysis.A new primer for metabarcoding of spider gut contentshttps://peerj.com/preprints/278542019-07-122019-07-12Denis LafageVasco ElbrechtJordan CuffDirk SteinkePeter HambäckAnn Erlandsson
As a key predator group, spiders have received a lot of attention by food web ecologists in diverse fields such as pest control, pollutant transfers, and cross-ecosystem fluxes. The difficulty involved in studying their diet has led to the use of new technologies such as metabarcoding of gut contents. The amplification of a broad range of spider prey without amplifying spiders themselves is challenging and, until now, an efficient universal primer purposed for this has not existed.
We developed a novel forward primer (NoSpi2) targeting the cytochrome c oxidase subunit I gene. The primer was designed not to amplify spiders of the oval calamistrum clade (Lycosidae and closely related species) while still amplifying most other invertebrates. NoSpi2 was tested together with the reverse primer BR2 in silico, in vitro on single specimens of prey and spiders, on mock and malaise trap communities, and in an ecological application.
In silico evaluation predicted high primer bias for spiders of the oval calamistrum clade and low bias for all other invertebrates. These results were largely confirmed by in vitro tests. Additionally, some spider families were not amplified contrary to our expectations. We demonstrated a high efficiency for the primer pair NoSpi2/BR2 which recovered up to 94% of taxa in the mock community and 85% of the taxa detected by the best invertebrate primer pair known (BF3+BR2) for the malaise trap community. The field experiment showed that Lycosidae spider DNA is not amplified by the NoSpi2 primer set. It also demonstrated a broad range of detectable prey species. We found prey from 12 orders, 67 families and 117 species.
The ability of the NoSpi2/BR2 primer combination to reliably amplify prey species, without amplifying any predator reads, makes it an ideal choice for gut-content analysis for spider species of lycosids and closely related species, even enabling the homogenization of entire spider specimens without dissection. Given that the detected prey species included other spiders and carabid beetles, this primer could be used for not only diet and biological control studies, but also to study intra-guild predation.
As a key predator group, spiders have received a lot of attention by food web ecologists in diverse fields such as pest control, pollutant transfers, and cross-ecosystem fluxes. The difficulty involved in studying their diet has led to the use of new technologies such as metabarcoding of gut contents. The amplification of a broad range of spider prey without amplifying spiders themselves is challenging and, until now, an efficient universal primer purposed for this has not existed.We developed a novel forward primer (NoSpi2) targeting the cytochrome c oxidase subunit I gene. The primer was designed not to amplify spiders of the oval calamistrum clade (Lycosidae and closely related species) while still amplifying most other invertebrates. NoSpi2 was tested together with the reverse primer BR2 in silico, in vitro on single specimens of prey and spiders, on mock and malaise trap communities, and in an ecological application.In silico evaluation predicted high primer bias for spiders of the oval calamistrum clade and low bias for all other invertebrates. These results were largely confirmed by in vitro tests. Additionally, some spider families were not amplified contrary to our expectations. We demonstrated a high efficiency for the primer pair NoSpi2/BR2 which recovered up to 94% of taxa in the mock community and 85% of the taxa detected by the best invertebrate primer pair known (BF3+BR2) for the malaise trap community. The field experiment showed that Lycosidae spider DNA is not amplified by the NoSpi2 primer set. It also demonstrated a broad range of detectable prey species. We found prey from 12 orders, 67 families and 117 species.The ability of the NoSpi2/BR2 primer combination to reliably amplify prey species, without amplifying any predator reads, makes it an ideal choice for gut-content analysis for spider species of lycosids and closely related species, even enabling the homogenization of entire spider specimens without dissection. Given that the detected prey species included other spiders and carabid beetles, this primer could be used for not only diet and biological control studies, but also to study intra-guild predation.Comparison of the bacterial abundance and diversity in the Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) between both sexeshttps://peerj.com/preprints/278262019-06-272019-06-27Chunhui GuoXin PengXialin ZhengXiaoyun WangRuirui WangZongyou HuangZhende Yang
Background. Insects harbor a myriad of microorganisms, many of which can affect the sex ratio and manipulate the reproduction of the host. Leptocybe invasa is an invasive pest that causes serious damage to eucalyptus plantations, and both female-biased sex ratios and thelytokous parthenogenesis in L. invasa contribute to the rapid invasion and fast growth of the population. However, the interior bacterial composition and abundance of L. invasa and the differences between both sexes remain unclear.
Results. The Illumina MiSeq platform was used to compare the composition of the bacterial community in adult females and males by sequencing with variation in the V3-V4 region of the 16S ribosomal DNA gene. The results showed that 1320 operational taxonomic units (OTUs) were obtained in total. These OTUs were annotated into 24 phyla, 71 classes, 130 orders, 245 families and 501 genera. At the genus level, the dominant bacteria in females and males was Rickettsia and Rhizobium, respectively.
Conclusion. The bacteria living in L. invasa adult females and males had high diversity. There were differences in the bacterial community in L. invasa between both sexes, and the bacterial diversity in male adults was more abundant than that in female adults. This study presents a comprehensive comparison of bacterial communities living in L. invasa between sexes, which plays a significant role in reproductive strategy, sex regulation and the invasive mechanism of L. invasa and provides a basis for follow-up studies on the coevolution and interaction between L. invasa and its predominant bacteria.
Background. Insects harbor a myriad of microorganisms, many of which can affect the sex ratio and manipulate the reproduction of the host. Leptocybe invasa is an invasive pest that causes serious damage to eucalyptus plantations, and both female-biased sex ratios and thelytokous parthenogenesis in L. invasa contribute to the rapid invasion and fast growth of the population. However, the interior bacterial composition and abundance of L. invasa and the differences between both sexes remain unclear.Results. The Illumina MiSeq platform was used to compare the composition of the bacterial community in adult females and males by sequencing with variation in the V3-V4 region of the 16S ribosomal DNA gene. The results showed that 1320 operational taxonomic units (OTUs) were obtained in total. These OTUs were annotated into 24 phyla, 71 classes, 130 orders, 245 families and 501 genera. At the genus level, the dominant bacteria in females and males was Rickettsia and Rhizobium, respectively.Conclusion. The bacteria living in L. invasa adult females and males had high diversity. There were differences in the bacterial community in L. invasa between both sexes, and the bacterial diversity in male adults was more abundant than that in female adults. This study presents a comprehensive comparison of bacterial communities living in L. invasa between sexes, which plays a significant role in reproductive strategy, sex regulation and the invasive mechanism of L. invasa and provides a basis for follow-up studies on the coevolution and interaction between L. invasa and its predominant bacteria.Chemical communication and ecology in Eupnoi harvestmenhttps://peerj.com/preprints/277782019-06-032019-06-03Ignacio Escalante
Communication via chemical signals and cues is a widespread modality in animals. Producing, transmitting, receiving and processing chemical compounds impose important challenges. Nonetheless, certain arthropods rely almost exclusively on this channel for intra- and inter-specific communication. Through a preliminary literature review, I summarize here the morphological, behavioral and evolutionary implications of chemical communication in harvestmen (the arachnid order Opiliones), with particular emphasis in one group: the Eupnoi or “Daddy Long-legs”. This group has a unique secretory gland that opens in an ozopore in their dorsum. While relying mostly on short-range olfaction and contact chemoreception using different setae, some harvestmen are known to use chemicals in defense, alarm, spatial marking, recruitment, or reproduction. I then propose future research direction on the mechanisms of production and the evolutionary history of these traits. Specific questions can include (1) are chemical signals used as alarm pheromones in Eupnoi aggregations? (2) Do harvestmen rely on chemicals to mark their traditional roosting sites? If so, what are the chemicals involved and how do those differ from the ones used as alarm signals? Also, (3) what are the specific functions of the chemical communication during in female-male communication and multi-specific roosting aggregations? And (4) to what extent the use of chemical defenses imposes a trade-off with other defense mechanisms such as ‘playing dead’ or voluntarily releasing legs. Overall, these harvestmen provide a unique opportunity to test comprehensive and interdisciplinary hypotheses to understand the evolution of chemical communication, as well as the importance of chemical ecology on species diversification in arthropods.
Communication via chemical signals and cues is a widespread modality in animals. Producing, transmitting, receiving and processing chemical compounds impose important challenges. Nonetheless, certain arthropods rely almost exclusively on this channel for intra- and inter-specific communication. Through a preliminary literature review, I summarize here the morphological, behavioral and evolutionary implications of chemical communication in harvestmen (the arachnid order Opiliones), with particular emphasis in one group: the Eupnoi or “Daddy Long-legs”. This group has a unique secretory gland that opens in an ozopore in their dorsum. While relying mostly on short-range olfaction and contact chemoreception using different setae, some harvestmen are known to use chemicals in defense, alarm, spatial marking, recruitment, or reproduction. I then propose future research direction on the mechanisms of production and the evolutionary history of these traits. Specific questions can include (1) are chemical signals used as alarm pheromones in Eupnoi aggregations? (2) Do harvestmen rely on chemicals to mark their traditional roosting sites? If so, what are the chemicals involved and how do those differ from the ones used as alarm signals? Also, (3) what are the specific functions of the chemical communication during in female-male communication and multi-specific roosting aggregations? And (4) to what extent the use of chemical defenses imposes a trade-off with other defense mechanisms such as ‘playing dead’ or voluntarily releasing legs. Overall, these harvestmen provide a unique opportunity to test comprehensive and interdisciplinary hypotheses to understand the evolution of chemical communication, as well as the importance of chemical ecology on species diversification in arthropods.