The Geography of Sexual Conflict: A Synthetic Review.

AbstractSexual conflict is a mechanism of selection driven by the divergent fitness interests between females and males. This disagreement can be great enough to promote antagonistic/defensive traits and behaviors. Although the existence of sexual conflict has been identified in many species, less research has explored the conditions that initially promote sexual conflict in animal mating systems. In previous work in Opiliones, we observed that morphological traits associated with sexual conflict occurred only in species from northern localities. We hypothesized that by shortening and compartmentalizing time periods optimal for reproduction, seasonality represents a geographic condition sufficient to promote sexual conflict. We conducted a systematic review of the literature on reproductive traits and behaviors. Using standardized criteria, we reviewed publications to identify whether subjects occurred in a temperate (high-seasonality) or tropical (low-seasonality) biome. After identifying and adjusting for a publication bias toward temperate research, we identified no significant difference in the strength of sexual conflict between temperate and tropical study systems. A comparison between the distribution of taxa studied in sexual conflict articles and articles focused on general biodiversity indicates that species with conflict-based mating systems more accurately represent the distribution of terrestrial animal species. These findings contribute to ongoing efforts to characterize the origins of sexual conflict as well as life history traits that covary with sexual conflict.

Dual Functions of labial Resolve the Hox Logic of Chelicerate Head Segments.

Despite an abundance of gene expression surveys, comparatively little is known about Hox gene function in Chelicerata. Previous investigations of paralogs of labial (lab) and Deformed (Dfd) in a spider have shown that these play a role in tissue maintenance of the pedipalp segment (lab-1) and in patterning the first walking leg identity (Dfd-1), respectively. However, extrapolations of these data across chelicerates are hindered by the existence of duplicated Hox genes in arachnopulmonates (e.g., spiders and scorpions), which have resulted from an ancient whole genome duplication (WGD) event. Here, we investigated the function of the single-copy ortholog of lab in the harvestman Phalangium opilio, an exemplar of a lineage that was not subject to this WGD. Embryonic RNA interference against lab resulted in two classes of phenotypes: homeotic transformations of pedipalps to chelicerae, as well as reduction and fusion of the pedipalp and leg 1 segments. To test for combinatorial function, we performed a double knockdown of lab and Dfd, which resulted in a homeotic transformation of both pedipalps and the first walking legs into cheliceral identity, whereas the second walking leg is transformed into a pedipalpal identity. Taken together, these results elucidate a model for the Hox logic of head segments in Chelicerata. To substantiate the validity of this model, we performed expression surveys for lab and Dfd paralogs in scorpions and horseshoe crabs. We show that repetition of morphologically similar appendages is correlated with uniform expression levels of the Hox genes lab and Dfd, irrespective of the number of gene copies.

A novel probe set for the phylogenomics and evolution of RTA spiders.

Spiders are important models for evolutionary studies of web building, sexual selection and adaptive radiation. The recent development of probes for UCE (ultra-conserved element)-based phylogenomic studies has shed light on the phylogeny and evolution of spiders. However, the two available UCE probe sets for spider phylogenomics (Spider and Arachnida probe sets) have relatively low capture efficiency within spiders, and are not optimized for the retrolateral tibial apophysis (RTA) clade, a hyperdiverse lineage that is key to understanding the evolution and diversification of spiders. In this study, we sequenced 15 genomes of species in the RTA clade, and using eight reference genomes, we developed a new UCE probe set (41 845 probes targeting 3802 loci, labelled as the RTA probe set). The performance of the RTA probes in resolving the phylogeny of the RTA clade was compared with the Spider and Arachnida probes through an in-silico test on 19 genomes. We also tested the new probe set empirically on 28 spider species of major spider lineages. The results showed that the RTA probes recovered twice and four times as many loci as the other two probe sets, and the phylogeny from the RTA UCEs provided higher support for certain relationships. This newly developed UCE probe set shows higher capture efficiency empirically and is particularly advantageous for phylogenomic and evolutionary studies of RTA clade and jumping spiders.

Molecular analyses of pseudoscorpions in a subterranean biodiversity hotspot reveal cryptic diversity and microendemism.

Nested within the Mediterranean biodiversity hotspot, the Dinaric Karst of the western Balkans is one of the world's most heterogeneous subterranean ecosystems and renowned for its highly diverse and mostly endemic fauna. The evolutionary processes leading to both endemism and diversity remain insufficiently understood, and large-scale analyses on taxa that are abundant in both subterranean and surface habitats remain infrequent. Here, we provide the first comprehensive molecular study on Croatian pseudoscorpions, a lineage of arachnids that is common and diverse in both habitats. Phylogenetic reconstructions using 499 COI sequences derived from 128 morphospecies collected across the Dinaric Karst show that: (i) occurrence in karstic microhabitats boosters speciation and endemism in the most diverse genera Chthonius C.L. Koch, 1843 (37 morphospecies) and Neobisium Chamberlin, 1930 (34 morphospecies), (ii) evidence for ongoing diversification is found in many species and species complexes through low optimal thresholds (OTs) and species delineation analyses, and (iii) landscape features, such as mountain ranges, correlate with patterns of genetic diversity in the diverse genus Neobisium. We present two synonymies: Protoneobisium Curcic, 1988 = Neobisium, syn. nov., and Archaeoroncus Curcic and Rada, 2012 = Roncus L. Koch, 1873, syn. nov. Overall, our study suggests that karstic microhabitats promote diversification in soil- and cave-dwelling arthropods at all taxonomic levels, but also provide important refugia for invertebrates in past and present periods of environmental change.

Comparative analysis of mitochondrial genomes reveals family-specific architectures and molecular features in scorpions (Arthropoda: Arachnida: Scorpiones).

Scorpions are a group of arachnids with great evolutionary success that comprise more than 2,000 described species. Mitochondrial genomes have been little studied in this clade. We describe and compare different scorpion mitochondrial genomes and analyze their architecture and molecular characteristics. We assembled eight new scorpion mitochondrial genomes from transcriptomic datasets, annotated them, predicted the secondary structures of tRNAs, and compared the nucleotide composition, codon usage, and relative synonymous codon usage of 16 complete scorpion mitochondrial genomes. Lastly, we provided a phylogeny based on all mitochondrial protein coding genes. We characterized the mitogenomes in detail and reported particularities such as dissimilar synteny in the family Buthidae compared to other scorpions, unusual tRNA secondary structures, and unconventional start and stop codons in all scorpions. Our comparative analysis revealed that scorpion mitochondrial genomes exhibit different architectures and features depending on taxonomic identity. We highlight the parvorder Buthida, particularly the family Buthidae, as it invariably exhibited different mitogenome features such as synteny, codon usage, and AT-skew compared to the parvorder Iurida that included the rest of the scorpion families we analyzed in this study. Our results provide a better understanding of the evolution of mitogenome features and phylogenetic relationships in scorpions.

Anatomy of the miniature four-legged mite Achaetocoptes quercifolii (Arachnida: Acariformes: Eriophyoidea).

Miniaturization is one of the important trends in the evolution of terrestrial arthropods. In order to study adaptations to microscopic sizes, the anatomy of the smallest insects was previously studied, but not the anatomy of the smallest mites. Some of the smallest mites are Eriophyidae. In this study we describe for the first time the anatomy of the mite Achaetocoptes quercifolii, which is about 115 µm long. For this purpose, we used light, scanning, and transmission electron microscopy and performed 3D reconstructions. The anatomy of A. quercifolii is compared with the anatomy of larger representatives of Eriophyoidea. Despite the small size of the studied species, there is no considerable simplification of its anatomy compared to larger four-legged mites. A. quercifolii has a number of miniaturization effects similar to those found in microinsects: a strong increase in the relative volume of the reproductive system, an increase in the relative volume of the brain, reduction in the number and size of cells of the nervous system. As in some larger four-legged mites, A. quercifolii undergoes midgut lysis at the stage of egg production. On the other hand, in A. quercifolii a greater number of opisthosomal muscles are preserved than in larger gall-forming four-legged mites.

Too early for the ferry: The biogeographic history of the Assamiidae of southeast Asia (Chelicerata: Opiliones, Laniatores).

Opiliones (harvestmen) have come to be regarded as an abundant source of model groups for study of historical biogeography, due to their ancient age, poor dispersal capability, and high fidelity to biogeographic terranes. One of the least understood harvestman groups is the Paleotropical Assamiidae, one of the more diverse families of Opiliones. Due to a labyrinthine taxonomy, poorly established generic and subfamilial boundaries, and the lack of taxonomic keys for the group, few efforts have been undertaken to decipher relationships within this arachnid lineage. Neither the monophyly of the family, nor its exact placement in the harvestman phylogeny, have been established. Here, we assessed the internal phylogeny of Assamiidae using a ten-locus Sanger dataset, sampling key lineages putatively ascribed to this family for five of the ten markers. Our analyses recovered Assamiidae as a monophyletic group, in a clade with the primarily Afrotropical Pyramidopidae and the southeast Asian Beloniscidae. Internal relationships of assamiids disfavored the systematic validity of subfamilies, with biogeography reflecting much better phylogenetic structure than the existing higher-level taxonomy. To assess whether the Asian assamiids came to occupy Indo-Pacific terranes via rafting on the Indian subcontinent, we performed divergence dating to infer the age of the family. Our results show that Indo-Pacific clades are ancient, originating well before the Cretaceous and therefore predate a vicariant mechanism commonly encountered for Paleotropical taxa.

Different environment, different reproductive strategies? Unexpected field observations in the harvestmen Discocyrtus prospicuus (Laniatores: Gonyleptidae).

The evolution of reproductive strategies depends on the relative balance between current benefits and future costs. Geographic variation in demographic and ecological factors has the potential to affect reproductive strategies by altering this optimal cost-benefit balance. Here, we studied a population of the harvestmen Discocyrtus prospicuus inhabiting an environment never studied before in this context: a tidal freshwater wetland. We made monthly observations of male-female interactions and their association with egg clutches during a two-year field survey. Our results do not match the expected pattern for this species, consisting of males deserting females immediately after copulation, and females laying isolated eggs and abandoning them after oviposition. Conversely, we show for the first-time pairs D. prospicuus, formed by a female and a male, resting together before and after oviposition. Females of this wetland population lay the eggs in small clutches and some of the clutches had eggs in more than one stage of development. Also, we found many females alone over or near the egg clutch in the typical resting position. These findings markedly widen the behavioral specter previously reported for this species and set the stage for future research to determine the causes of these variations.

Two new species of Neogonyleptes Roewer, 1913 (Opiliones: Gonyleptidae: Pachylinae) from the Nahuelbuta mountain range, Chile.

Two new species of the Chilean endemic genus Neogonyleptes Roewer, 1913 are described based on specimens obtained in the Nahuelbuta mountain range, Biobo and La Araucana Regions. The new taxa are morphologically allied to Neogonyleptes karschii (Srensen, 1902); however, both differ from all species of the genus by their dorsal scutum area III+IV, which is armed with a large, apically bifurcate apophysis. Neogonyleptes floresi sp. nov. differs from N. pedrazai sp. nov. principally in the slender body and legs, the proximal constriction of the scutal apophysis, and the distally straight prolateral apophysis on coxa IV. Detailed descriptions, illustrations, and comparisons of the new species are given. Additionally, some comments are provided about the taxonomy of Neogonyleptes and allied genera.

A new species of whip spider, Sarax sinensis sp. nov., from Fujian, China (Arachnida: Amblypygi: Charinidae).

To date, only two whip spider species have been recorded in China. We describe a new species, Sarax sinensis sp. nov., from Fujian, China. This species is morphologically similar to S. ioanniticus (Kritscher, 1959), S. israelensis (Miranda et al., 2016), and S. seychellarum (Kraepelin, 1898), but can be distinguished by the combination of the following characters: 35 segments in leg I tarsus, eight teeth on cheliceral claw, and four dorsal and ventral spines respectively on pedipalp femur. To examine the evolutionary history of S. sinensis sp. nov., we sequenced 12S, 16S, and COI gene regions of our specimens and inferred its phylogenetic position. The inferred phylogenetic trees placed the new species within Sarax, with its closest relative being distributed across the western Asia. The type specimens are deposited in the Museum of Biology, East China Normal University (ECNU).

From the Ethiopian Bale Mountains hotspotFilopalpinae subfam. nov., a new taxon of Laniatorean harvestmen based on external and genital morphology (Arachnida, Opiliones, Assamiidae).

Filopalpinae subfam. nov. is proposed as a new subfamily within family Assamiidae based on a new genus, Filopalpus gen. nov. and on five new species: F. joschmidti sp. nov., F. bale sp. nov., F. kakaensis sp. nov., F. altomontanus sp. nov. and F. niger sp. nov. All originate from the highlands of Ethiopia, namely the Bale Mountains and adjacent volcanoes in Oromia State. Species of the new subfamily are characterized by dense body cover with pointed tubercles causing a hedgehog appearance of the body (dorsal side, partly ventral side), extreme sexual dimorphism in pedipalps (in males thread-like long and thin surpassing body length by about four to six times, devoid of apophyses and thorns; in females short and stout about body length, with a distal grasping hand formed by apophyses and strong setae of tibia and tarsus, and tarsal claw). Male genital morphology is characterized by a hemolymph-pressure system of truncus penis and glans, a dorsal sub-distal tube-like glans with an inner prickly funnel, which is everted by hemolymph pressure during courtship. These male genital characters place the present species in Assamiidae, but external morphology points to a strongly different separate evolutionary unit within this family. The five species known to date were secured at altitudes between 2830 and 4100 m. At least two of the collecting areas are now devoid of forest due to human impact. To secure the present specimens at high-altitude localities was possible only by searching in remote microhabitats unavailable for cattle and man-made fire. A perspective on current subfamilies of Assamiidae and on pedipalpal morphology and evolution is presented.

Two new species of Rhopalochernes Beier, 1932 (Pseudoscorpiones: Chernetidae) from Colombia.

The pseudoscorpion genus Rhopalochernes Beier, 1932 is restricted to the Neotropical region and currently includes eight species. Recent field collections in the Caribbean region of Colombia have revealed the presence of two previously undescribed species, which are here described as Rhopalochernes luiscarlosi sp. nov. and Rhopalochernes catalinae sp. nov. They differ from one another by the shape of the carapace, the position of the trichobothria and the length of the nodus ramosus. They differ from other species of the genus by the absence of eye spots, and the number of the cheliceral setae. One of these features, the presence of only four setae on the cheliceral hand, is shared with R. panamensis Heurtault, 1998 and R. chamberlini Heurtault, 1998, with other species possessing a higher number. Additionally, the key for the genus proposed by Beier (1932) is updated for included all the species.

Exploring species diversity and abundance of scorpions (Arachnida: Scorpiones) in certain regions of Khyber Pakhtunkhwa, Pakistan.

Despite scorpion diversity has long been acknowledged, the mystery of how it develops remains unresolved. The geographical distribution, species abundance and biodiversity of scorpions fauna in Khyber Pakhtunkhwa is poorly explored with many aspects like morphological, geographical, ecological and phylogenetically. As a result of faunaistic study on scorpions a total of 171 specimens from various regimes, Charsadda, Mardan, Peshawar and Kohat districts of Khyber Pakhtunkhwa, Pakistan from March 2018 to October 2018 were collected. GarminTM GPS V Plus device. The software Arc GIS 10.2 was used to create maps of the study areas. Pitfall traps were used to gather samples from sandy habitats and pastureland. Five species Hottentotta tamulus Fabricius, 1798, with (35%), Scorpiops pseudomontanus Kovarik and Ahmed, 2009, (26%), Orthochirus fuscipes Pocock, 1900, (15%), Hottentotta buchariensis Birula, 1897, (13%) and Deccanometrus latimanus Pocock, 1894, (11%) were detected in our proposed study. The research indicates that abundance and temperature have a favorable connection, while abundance and humidity get a negative correlation. The value of evenness shows the strong equilibrium between the effectiveness of sampling species, and the Shannon's index suggests that the Pakistani region has a high level of scorpion variety.

Using Surrogate Insects in Acid Bioassays for Development of New Controls for Varroa destructor (Arachnida: Varroidae).

Resistance to traditional synthetic compounds by Varroa destructor Anderson and Trueman and shortcomings of the organic acid class of acaracides commonly used in varroa management requires continual development of new controls. V. destructor, however, are difficult to obtain for use in control bioassays because they are obligate parasites that cannot be easily reared outside of a honey bee colony. We conducted bioassays using other, more easily obtainable species to find organisms that could be used as surrogates for V. destructor when testing new potential controls. We compared the toxicities of acetic acid, lactic acid, formic acid, and oxalic acid at 0.005%, 0.05%, 0.5%, 5%, and 50% (20% oxalic acid only) concentrations based on natural volatility (nonheated) for the control of two beetle species, Oryzaephilus surinamensis L. and Alphitobius diaperinus Panzer, greater wax moth larvae, Galleria mellonella L., and V. destructor. The assay results were consistent across all species with formic acid and acetic acid showing 100% mortality of all four test species at 50% concentration. The assays also provided insight into the method of application (vaporization or contact) needed to cause mortality. Our results show that other organisms can be used in place of V. destructor for initial testing of acids and possibly other chemicals for control of the ectoparasite.

Recent speciation and phenotypic plasticity within a parthenogenetic lineage of levantine whip spiders (Chelicerata: Amblypygi: Charinidae).

Caves constitute ideal study systems for investigating adaptation and speciation, as the abiotic conditions shared by aphotic habitats exert a set of environmental filters on their communities. Arachnids constitute an important component of many cave ecosystems worldwide. We investigated the population genomics of two whip spider species: Sarax ioanniticus, a widely distributed parthenogenetic species found across the eastern Mediterranean; and S. israelensis, a recently described troglomorphic species that is endemic to caves in Israel. Here, we show that S. israelensis is completely genetically distinct from S. ioanniticus and most likely also a parthenogen. Counterintuitively, despite the lack of genetic variability within S. ioanniticus and S. israelensis, we discovered considerable variation in the degree of median eye reduction, particularly in the latter species. Natural history data from captive-bred specimens of S. israelensis validated the interpretation of parthenogenesis. Our results are most consistent with a scenario of a sexual ancestral species that underwent speciation, followed by independent transitions to apomictic parthenogenesis in each of the two daughter species. Moreover, the lack of genetic variability suggests that variation in eye morphology in S. israelensis is driven exclusively by epigenetic mechanisms.

Variations in the carapace shape of whip spiders (Arachnida: Amblypygi).

Morphological studies often need to reference body size to correctly characterise the shape of organisms. In arthropods, the most commonly used reference for this is the length or width of the carapace, thorax, or the prosoma in the case of chelicerates. However, in the case of animals with unlimited growth, such as whip spiders, this measure could be irrelevant if growth is allometric. In this study, we analyse the ontogenetic modifications in prosoma outline shape in whip spiders during growth and compare the differences in shape between species. Differences are important for the relative prosoma width between species and, in the case of Damon medius, during growth in the juvenile stages, whereas the shape remains stable in mature stages. We conclude that a one-dimensional measure (i.e., length or width) suffices for mature specimens of a single species or family, but for larger studies, or when including immature specimens, at least the prosoma area (within the outline shape) should be used as a size estimator.

Impact of mitotype diversity on metabarcoding biodiversity estimations in Insecta and Arachnida using different sample preparation strategies.

DNA barcoding and metabarcoding have been increasingly used in species delimitation and species diversity assessment, respectively, and the molecular markers used in animals are mainly derived from mitochondrial DNA. It is well known that the phenomenon of multiple mitochondrial haplotypes within the same specimen (hereafter referred to as "mitotype diversity") may have a negative impact on the proper assessment of biodiversity by metabarcoding. However, few studies have focused on the incidence of this phenomenon and its effects on metabarcoding results using different sample preparation strategies, such as mock community construction using pooled high-throughput sequencing (HTS) data, DNA-pooling and Tissue-pooling. In this study, we investigated mitotype diversity and its influence on metabarcoding based on 398 specimens from 66 species of Insecta and 82 specimens from 16 species of Arachnida by HTS of the mitochondrial cox1 gene fragment. The results revealed that mitotype diversity was common in the studied taxa and significantly increased the number of operational taxonomic units (OTUs) using the three sample preparation strategies. The results also showed that the bioinformatics pipeline based on authentic amplicon sequence variants was more reliable than the pipeline based on OTUs. Regarding the sample preparation strategies of DNA-pooling and Tissue-pooling commonly used in metabarcoding, our results revealed that their results of metabarcoding were quite similar, and the Tissue-pooling strategy was therefore preferred because of its simplicity. Our study calls for additional attention to the interference of mitotype diversity on the results of DNA metabarcoding in biodiversity assessment.

Evolutionary morphology of coxal musculature in Pseudoscorpiones (Arachnida).

Pseudoscorpions are an ancient and globally distributed lineage of arachnids with more than 4000 species. Despite being present in virtually all terrestrial habitats, their morphology and anatomy has rarely been studied to date, which hampers homology statements both within and between other arachnid orders. All pseudoscorpions share a morphological peculiarity, the fixation of the coxae of all the walking legs. The same morphological condition is seen in certain other arachnid taxa, such as Solifugae or Scorpiones - potential sistergroups of Pseudoscorpiones. To investigate the musculature apparatus of this unusual feature, we reconstructed the musculature in the coxae of walking legs in three species of pseudoscorpions that represent the three major clades within this order. Using micro-computed tomography (µCT), we show that pseudoscorpions have the highest number of coxal muscles amongst the arachnid orders (12 vs. fewer than 10 in others), and that the muscular composition of the first two legs differs from that in the hind legs, correlating with the difference in function, i.e. pulling in the front legs and pushing in the hind legs. Pseudoscorpions are also unique amongst the arachnids in lacking endoskeletal structures (coxal apodeme or costa coxalis) inside the coxae. We observed that within pseudoscorpions, there is a trend towards a reduction of the number of coxal muscles, with the most basal-branching taxon having the highest number and more derived taxa exhibiting lower counts. We hypothesize the muscular ground pattern for Pseudoscorpiones and discuss the evolution of this system by comparing it to the (scanty) data on other arachnids available in the literature.