Still a one species genus? Strong genetic diversification in the world’s largest living odonate, the Neotropical damselfly Megaloprepus caerulatus

The Quality of Sequence Data Affects Biodiversity and Conservation Perspectives in the Neotropical Damselfly Megaloprepus caerulatus

Ideally, the footprint of the evolutionary history of a species is drawn from integrative studies including quantitative and qualitative taxonomy, biogeography, ecology, and molecular genetics. In today’s research, species delimitations and identification of conservation units is often accompanied by a set of—at minimum—two sequence markers appropriate for the systematic level under investigation. Two such studies re-evaluated the species status in the world’s largest Odonata, the Neotropical damselfly Megaloprepus caerulatus. The species status of the genus Megaloprepus has long been debated. Despite applying a highly similar set of sequence markers, the two studies reached different conclusions concerning species status and population genetic relationships. In this study, we took the unique opportunity to compare the two datasets and analyzed the reasons for those incongruences. The two DNA sequence markers used (16S rDNA and CO1) were re-aligned using a strict conservative approach and the analyses used in both studies were repeated. Going step by step back to the first line of data handling, we show that a high number of unresolved characters in the sequence alignments as well as internal gaps are responsible for the different outcomes in terms of species delimitations and population genetic relationships. Overall, this study shows that high quality raw sequence data are an indispensable requirement, not only in odonate research.

Nonhuman Value: A Survey of the Intrinsic Valuation of Natural and Artificial Nonhuman Entities

To be intrinsically valuable means to be valuable for its own sake. Moral philosophy is often ethically anthropocentric, meaning that it locates intrinsic value within humans. This paper rejects ethical anthropocentrism and asks, in what ways might nonhumans be intrinsically valuable? The paper answers this question with a wide-ranging survey of theories of nonhuman intrinsic value. The survey includes both moral subjects and moral objects, and both natural and artificial nonhumans. Literatures from environmental ethics, philosophy of technology, philosophy of art, moral psychology, and related fields are reviewed, and gaps in these literatures are identified. Although the gaps are significant and much work remains to be done, the survey nonetheless demonstrates that those who reject ethical anthropocentrism have considerable resources available to develop their moral views. Given the many very high-stakes issues involving both natural and artificial nonhumans, and the sensitivity of these issues to how nonhumans are intrinsically valued, this is a vital project to pursue.

Negative body size-dependent resource allocation underlies conspicuous sexual ornaments in a territorial damselfly

Sexual ornaments, signalling individual quality to choosy females or rival males, often show steeper body size scaling compared with non-sexually selected traits. Theory posits such steeper body size scaling is the result of differential resource allocation, reflecting trade-offs between different components of fitness. Yet, the process of resource allocation towards body size-dependent sexual ornaments has been rarely understood empirically. Using the Neotropical territorial damselfly Megaloprepus caerulatus, whose males and females carry wax-based, sex-specific white wing bands and white wing tips respectively, we investigated nutrition sensitivity and body size scaling of both traits by manipulating larval food availability and directly quantified both the fat allocated to wing ornaments and the fat reserve from which allocations are made. Both colour traits exhibited sensitivity to food availability during larval development and steeper body size scaling compared with control traits. Although the absolute amount of fat invested in developing the colour ornaments increased with body size, the proportion of total fat allocated to the ornaments decreased with body size, making exaggerated ornaments less affordable for smaller individuals. Our data demonstrate that measuring the proportion of resource pool from which an individual's ornaments are derived (i.e. its affordability) is essential for understanding the maintenance of honesty of sexual signals.

The use of Odonata species for environmental assessment: a meta-analysis for the Neotropical region

The order Odonata has been regularly used as an indicator of the ecosystem's condition. The objective of this review was to analyze the importance of Odonata for environmental assessments (assessment types, statistical approach, life stages, and sampling method, or particular metric), summarizing the current state, the trends, and identifying related research issues in the Neotropical region. Therefore, we selected 62 articles from 2007 to 2018 based on published research to monitor Odonata assessments in the Neotropical region. We compiled a database and ran statistical analyses for the observed frequencies. We found that ecosystem health was the most frequent assessment type and quality the most used objective. In the case of statistical tests and metrics, multivariate analyses and species richness were most used in these papers. However, because there is a great diversity of habitats in this region, there is no unique monitoring protocol to assess the quality of ecosystem health and it is needed to create a proposal for a standard evaluation protocol. Consequently, guidelines for monitoring are presented, and we suggest three stages to establish a specific protocol for each site, which records the set of species most sensitive to the exchange rate evaluated, as well as the use of rarefaction methods, the index of diversity based on the area under the curve, and multivariate analysis, among other recommendations.

Complex evolutionary history of the American Rubyspot damselfly, Hetaerina americana (Odonata): Evidence of cryptic speciation

Analyzing the magnitude and distribution of genetic variation within and among populations allows for hypothesis testing about historical demographic size changes, secondary contacts, refugia, and speciation patterns. Species distribution and genetic structure are greatly influenced by the complex life cycle and behavior of odonates. Hetaerina americana has been widely used as a model system in behavioral studies, but its population genetic structure has not been analyzed, except for a single study that included only three populations but identified the presence of markedly differentiated genetic groups, suggesting the existence of cryptic species. Here, we tested this hypothesis by assessing throughout the distribution range of H. americana the patterns of genetic and morphological variation in the male caudal appendages, due to the great importance of these structures in mate recognition. As molecular markers we used sequences of the mitochondrial cytochrome oxidase I (COI) gene and the nuclear internal transcribed spacer (ITS) region, as well as six nuclear microsatellites. We found very high population genetic differentiation (Φ_ST > 0.51) in the three sets of markers but with strong mitonuclear discordance. A neutrality test suggested that the mitochondrial genome might be under purifying selection in association to climatic variables (temperature seasonality). The assignment of individuals to nuclear genetic groups showed little admixture and complete congruence with morphological differentiation in the male caudal appendages. Hence, the results suggest that H. americana represents at least two different cryptic species which are isolated reproductively.

Digest: Ecomorphological convergence across the Atlantic

Did the remarkable helicopter damselflies (family Pseudostigmatidae) evolve their unique feeding and oviposition behaviors independently on two continents? In this issue, Toussaint et al. use molecular phylogenetic approaches to provide convincing evidence that these "forest giants" are in fact an example of ecomorphological convergence across the Atlantic Ocean.

Transcriptome profiling with focus on potential key genes for wing development and evolution in Megaloprepus caerulatus, the damselfly species with the world's largest wings

The evolution, development and coloration of insect wings remains a puzzling subject in evolutionary research. In basal flying insects such as Odonata, genomic research regarding bauplan evolution is still rare. Here we focus on the world's largest odonate species-the "forest giant" Megaloprepus caerulatus, to explore its potential for looking deeper into the development and evolution of wings. A recently discovered cryptic species complex in this genus previously considered monotypic is characterized by morphological differences in wing shape and color patterns. As a first step toward understanding wing pattern divergence and pathways involved in adaptation and speciation at the genomic level, we present a transcriptome profiling of M. caerulatus using RNA-Seq and compare these data with two other odonate species. The de novo transcriptome assembly consists of 61,560 high quality transcripts and is approximately 93% complete. For almost 75% of the identified transcripts a possible function could be assigned: 48,104 transcripts had a hit to an InterPro protein family or domain, and 28,653 were mapped to a Gene Ontology term. In particular, we focused on genes related to wing development and coloration. The comparison with two other species revealed larva-specific genes and a conserved 'core' set of over 8,000 genes forming orthologous clusters with Ischnura elegans and Ladona fulva. This transcriptome may provide a first point of reference for future research in odonates addressing questions surrounding the evolution of wing development, wing coloration and their role in speciation.

The most primitive metazoan animals, the placozoans, show high sensitivity to increasing ocean temperatures and acidities

The increase in atmospheric carbon dioxide (CO₂) leads to rising temperatures and acidification in the oceans, which directly or indirectly affects all marine organisms, from bacteria to animals. We here ask whether the simplest-and possibly also the oldest-metazoan animals, the placozoans, are particularly sensitive to ocean warming and acidification. Placozoans are found in all warm and temperate oceans and are soft-bodied, microscopic invertebrates lacking any calcified structures, organs, or symmetry. We here show that placozoans respond highly sensitive to temperature and acidity stress. The data reveal differential responses in different placozoan lineages and encourage efforts to develop placozoans as a potential biomarker system.

The complete mitochondrial genome of the neotropical helicopter damselfly Megaloprepus caerulatus (Odonata: Zygoptera) assembled from next generation sequencing data

Odonata (dragonflies and damselflies) is a small order at the base of flying insects (Pterygota). Resolving family-level phylogenetic relationships within this order receives great attention. Hereby, genetic data already resulted in various changes, which are however still under discussion. Mitochondrial genomes may further enhance such phylogenies. This study presents the complete mitochondrial genome of the Neotropical damselfly Megaloprepus caerulatus based on next generation sequencing (NGS) data on total genomic DNA. The total length comprises 16,094 bp and includes the standard metazoan set of 37 genes together with a 1376 bp long A + T rich (control) region. Gene content, gene arrangement and base frequency are consistent with other odonate mitochondrial genomes. It further contains four intergenic spacer regions, indicating a possible family specific feature for the Coenagrionidae and its close relatives.

How humans drive speciation as well as extinction

A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinctions, and discuss the challenges of using net species diversity as a conservation objective. Humans drive rapid evolution through relocation, domestication, hunting and novel ecosystem creation-and emerging technologies could eventually provide additional mechanisms. The number of species relocated, domesticated and hunted during the Holocene is of comparable magnitude to the number of observed extinctions. While instances of human-mediated speciation are known, the overall effect these mechanisms have upon speciation rates has not yet been quantified. We also explore the importance of anthropogenic influence upon divergence in microorganisms. Even if human activities resulted in no net loss of species diversity by balancing speciation and extinction rates, this would probably be deemed unacceptable. We discuss why, based upon 'no net loss' conservation literature-considering phylogenetic diversity and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity.