Myrmecicultoridae, a New Family of Myrmecophilic Spiders from the Chihuahuan Desert (Araneae: Entelegynae)

Evolution and comparative morphology of raptorial feet in spiders

Spiders are among the most diverse animals, which developed different morphological and behavioral traits for capturing prey. We studied the anatomy and functionality of the rare and apomorphic raptorial spider feet using 3D reconstruction modeling, among other imaging techniques. The evolutionary reconstruction of the raptorial feet (tarsus plus pretarsus) features using a composite tree of spiders, indicating that similar traits emerged three times independently in Trogloraptoridae, Gradungulinae, and Doryonychus raptor (Tetragnathidae). The characteristics defining the raptorial feet are an interlocked complex merging of the base of the elongated prolateral claw with the pretarsal sclerotized ring, with the former clasping against the tarsus. Raptorial feet even flex over robust raptorial macrosetae forming a reduced tarsal version of a catching basket to encase prey during hunting. Our results show that Celaeniini (Araneidae) and Heterogriffus berlandi (Thomisidae), taxa previously compared with raptorial spiders, lack the raptorial feet key characteristics and the tarsal-catching basket. We make predictions about the possible behavior of the abovementioned taxa that will need to be tested by observing living specimens. We conclude that multiple morphological tarsal and pretarsal micro-structures define the raptorial foot functional unit and recommend a comprehensive evaluation before assigning this configuration to any spider taxa.

Diversification and post-glacial range expansion of giant North American camel spiders in genus Eremocosta (Solifugae: Eremobatidae)

Species of camel spiders in the family Eremobatidae are an important component of arthropod communities in arid ecosystems throughout North America. Recently, research demonstrated that the evolutionary history and biogeography of the family are poorly understood. Herein we explore the biogeographic history of this group of arachnids using genome-wide single nucleotide polymorphism (SNP) data, morphology, and distribution modelling to study the eremobatid genus Eremocosta, which contains exceptionally large species distributed throughout North American deserts. Relationships among sampled species were resolved with strong support and they appear to have diversified within distinct desert regions along an east-to-west progression beginning in the Chihuahuan Desert. The unexpected phylogenetic position of some samples suggests that the genus may contain additional, morphologically cryptic species. Geometric morphometric analyses reveal a largely conserved cheliceral morphology among Eremocosta spp. Phylogeographic analyses indicate that the distribution of E. titania was substantially reduced during the last glacial maximum and the species only recently colonized much of the Mojave Desert. Results from this study underscore the power of genome-wide data for unlocking the genetic potential of museum specimens, which is especially promising for organisms like camel spiders that are notoriously difficult to collect.

Combining genomic, phenotypic and Sanger sequencing data to elucidate the phylogeny of the two-clawed spiders (Dionycha)

The importance of morphology in the phylogenomic era has recently gained attention, but relatively few studies have combined both types of information when inferring phylogenetic relationships. Sanger sequencing legacy data can also be important for understanding evolutionary relationships. The possibility of combining genomic, morphological and Sanger data in one analysis seems compelling, permitting a more complete sampling and yielding a comprehensive view of the evolution of a group. Here we used these three data types to elucidate the systematics and evolution of the Dionycha, a highly diverse group of spiders relatively underrepresented in phylogenetic studies. The datasets were analyzed separately and combined under different inference methods, including a novel approach for analyzing morphological matrices with commonly used evolutionary models. We tested alternative hypotheses of relationships and performed simulations to investigate the accuracy of our findings. We provide a comprehensive and thorough phylogenetic hypothesis for Dionycha that can serve as a robust framework to test hypotheses about the evolution of key characters. We also show that morphological data might have a phylogenetic impact, even when massively outweighed by molecular data. Our approach to analyze morphological data may serve as an alternative to the proposed practice of arbitrarily partitioning, weighting, and choosing between parsimony and stochastic models. As a result of our findings, we propose Trachycosmidae new rank for a group of Australian genera formerly included in Trochanteriidae and Gallieniellidae, and consider Ammoxenidae as a junior synonym of Gnaphosidae. We restore the family rank for Prodidomidae, but transfer the subfamily Molycriinae to Gnaphosidae. Drassinella is transferred to Liocranidae, Donuea to Corinnidae, and Mahafalytenus to Viridasiidae.

Converging on the orb: denser taxon sampling elucidates spider phylogeny and new analytical methods support repeated evolution of the orb web

High throughput sequencing and phylogenomic analyses focusing on relationships among spiders have both reinforced and upturned long-standing hypotheses. Likewise, the evolution of spider webs-perhaps their most emblematic attribute-is being understood in new ways. With a matrix including 272 spider species and close arachnid relatives, we analyze and evaluate the relationships among these lineages using a variety of orthology assessment methods, occupancy thresholds, tree inference methods and support metrics. Our analyses include families not previously sampled in transcriptomic analyses, such as Symphytognathidae, the only araneoid family absent in such prior works. We find support for the major established spider lineages, including Mygalomorphae, Araneomorphae, Synspermiata, Palpimanoidea, Araneoidea and the Retrolateral Tibial Apophysis Clade, as well as the uloborids, deinopids, oecobiids and hersiliids Grade. Resulting trees are evaluated using bootstrapping, Shimodaira-Hasegawa approximate likelihood ratio test, local posterior probabilities and concordance factors. Using structured Markov models to assess the evolution of spider webs while accounting for hierarchically nested traits, we find multiple convergent occurrences of the orb web across the spider tree-of-life. Overall, we provide the most comprehensive spider tree-of-life to date using transcriptomic data and use new methods to explore controversial issues of web evolution, including the origins and multiple losses of the orb web.

The Lepidoptera of Cuatrociénegas Protected Area 1. A new species in the genus Callistege Hübner, [1823] (Erebidae, Erebinae, Euclidiini) from the Chihuahuan Desert, Coahuila, Mexico

A new species of Callistege Hübner, [1823] (Lepidoptera, Erebidae, Erebinae, Euclidiini) is described from Cuatrociénegas Protected Area and Biosphere Preserve in Coahuila, Mexico. Adult male and female moths are illustrated, including genitalia. Callistegeclara Homziak & Metzler, sp. nov. is one of 27 new species of insects discovered during an inventory survey of arthropods of White Sands National Monument, USA, and Cuatrociénegas Protected Area (Mexico), funded by the U.S. National Park Service. The Cuatrociénegas Basin is known for high endemism of aquatic and wetland biota within the Chihuahuan Desert. Callistegeclara Homziak & Metzler, sp. nov. was found in a wetland environment.

Application of propylene glycol in DNA-based studies of invertebrates

High-throughput sequencing (HTS) studies on invertebrates commonly use ethanol as the main sample fixative (upon collection) and preservative (for storage and curation). However, alternative agents exists, which should not be automatically neglected when studies are newly designed. This review provides an overview of the application of propylene glycol (PG) in DNA-based studies of invertebrates, thus to stimulate an evidence-based discussion.

The use of PG in DNA-based studies of invertebrates is still limited (n = 79), but a steady increase has been visible since 2011. Most studies used PG as a fixative for passive trapping (73%) and performed Sanger sequencing (66%; e.g. DNA barcoding). More recently, HTS setups joined the field (11%). Terrestrial Coleoptera (30%) and Diptera (20%) were the most studied groups. Very often, information on the grade of PG used (75%) or storage conditions (duration, temperature) were lacking. This rendered direct comparisons of study results difficult, and highlight the need for further systematic studies on these subjects.

When compared to absolute ethanol, PG can be more widely and cheaply acquired (e.g. as an antifreeze, 13% of studies). It also enables longer trapping intervals, being especially relevant at remote or hard-to-reach places. Shipping of PG-conserved samples is regarded as risk-free and is authorised, pinpointing its potential for larger trapping programs or citizen science projects. Its property to retain flexibility of morphological characters as well as to lead to a reduced shrinkage effect was especially appraised by integrative study designs. Finally, the so far limited application of PG in the context of HTS showed promising results for short read amplicon sequencing and reduced representation methods. Knowledge of the influence of PG fixation and storage for long(er) read HTS setups is currently unavailable.

Given our review results and taking difficulties of direct methodological comparisons into account, future DNA-based studies of invertebrates should on a case-by-case basis critically scrutinise if the application of PG in their anticipated study design can be of benefit.