Male terminalia of Cercopidae (Hemiptera, Cicadomorpha): towards a consensus terminology

The study of male genital appendages is often necessary to identify a species and to characterise the higher systematics ranks for the Cercopidae, a large family of Hemiptera. Therefore, many authors have used them in their work but without any clear consensus on the terms used for each part constituting the male terminalia. A standardised terminology is important for the quality of a taxonomic description but even more essential when we want to compare species and establish a primary homology between states of character and their use in the frame of phylogenetic analysis. The use of a consensus terminology should ensure that we are all observing, speaking and describing the same genital appendage and comparing homologous characters. In order to propose a consensus terminology, we have reviewed all the major works on the anatomy of terminalia for the family since the first description using those characters in 1922. We proposed the use of consensual terms, listed with their definitions. In addition we studied a diversified panel of male specimens, chosen in order to represent as many Cercopidae tribes as possible. We categorised five different groups of Cercopidae according to their male terminalia structures. This opens the reflection on the evolutionary patterns for these structures.

Multi-context Knowledge Base using Calculated Descriptors from Xper3: the Archaeocyaths Knowledge Base example

Natural sciences need to make assertions about characteristics of taxa. Traits and qualities or descriptors and states become increasingly crucial as a resource for identification adapted to both scientists and the public. Specialists, non-specialists, and the general public need different strategies for accessing the information. Creating a knowledge base is time-consuming and adapting this base to several needs seems to increase the required time substantially. Specialists think that an identification tool requires a complete overhaul when they want to change the target audience or the language... so they do not wish to get involved. How to minimize creation and update time? How to aggregate data only once in order to create a single knowledge base with different access levels? Strategies for integrating different patterns of descriptors in a single knowledge base are useful to modulate descriptions without loss of information and with the certainty that everything is up to date in each context. This multi-context knowledge base, derived from a single trait dataset, can generate descriptions adapted to different contexts and users. To address this issue, we propose to use calculated descriptors in order to have on the same knowledge base, different versions of descriptors that are updated automatically when the reference trait is modified. Calculated descriptors are a distinctive feature of Xper3. These descriptors are automatically computed from other descriptors by using logical operators (boolean operators). Xper3 (http://www.xper3.com) is a web platform that manages descriptive data and provides interactive identification keys. Xper3 and its previous version, Xper2, have been used already for various taxonomic groups. We will focus on fossils in order to reveal how calculated descriptors in Xper3 knowledge bases can solve the multi-context problem. The main source of content is the archaeocyaths knowledge base (http://archaeocyatha.infosyslab.fr). Archaeocyaths are the first animals to build reefs during the Cambrian. They are calcified sponges without spicules. The archaeocyaths knowledge base is an efficient resource for scientific studies and a useful tool for non-specialists, especially with the support of calculated descriptors. Correspondence between archaeocyath and sponge morphologies is not ready yet, but everything will be included into PORO (The Porifera Ontology, http://purl.obolibrary.org/obo/poro/releases/2014-03-06/) in the short term (an anatomy ontology about sponges). In this knowledge base, calculated descriptors are used to: create a consistent multilingual interactive identification key (French and English are available and Russian is in draft), generate descriptors adapted to different level of expertise and reword morphological descriptors (adapted for identification) into homologous characters (adapted for phylogeny). create a consistent multilingual interactive identification key (French and English are available and Russian is in draft), generate descriptors adapted to different level of expertise and reword morphological descriptors (adapted for identification) into homologous characters (adapted for phylogeny). Xper2 and Xper3 are compatible with TDWG’s Structured Descriptive Data (SDD) format. Calculated descriptors do not exist in SDD format and so they are exported from Xper3 as categorical descriptors, therefore losing the origin of values. Calculated descriptors are powerful and we are interested in discussing these with SDD and Xper3 users in order to improve the user interface and develop new tools for the analysis of such descriptors.

Effectiveness of homologous Thai letterforms presented in parafoveal vision

Design approaches to improve Thai font legibility by clarifying idealistic key features using a blur simulation method have been proposed. Specifically, the jutting out of the tail of characters and inclusion of a loop-with-serrated-line, together with sufficient character width, have been found to improve legibility. In the current study, a set of four homologous characters was presented to the parafoveal region with a short-exposure methodology to display the characters with low visual acuity. Overall, the results revealed that most of the chosen idealistic key features enhanced the legibility of characters presented in parafoveal vision. However, the detailed results revealed variation in the amount of confusion between letter pairs for each tested character. These findings suggest the need for several practical improvements by modifying the specific features of each letter. Although the results of the short-exposure and blur simulation approaches differed at times, the findings of both studies suggest possibilities for developing optimal letterforms using a combination of both methodologies.

Building a Twig Phylogeny

In this classroom activity, students build a phylogeny for woody plant species based on the morphology of their twigs. Using any available twigs, students can practice the process of cladistics to test evolutionary hypotheses for real organisms. They identify homologous characters, determine polarity through outgroup comparison, and construct a parsimonious tree based on synapomorphies (shared derived characters). This activity efficiently demonstrates many systematics concepts, including homology, homoplasy (convergence and reversal), polarity, synapomorphy, symplesiomorphy, autapomorphy, polytomy, and parsimony. It also engages students in inquiry, promotes student collaboration, raises awareness of plant structure, and exposes students to the diversity of common local trees.

Evolution of sexually dimorphic characters in peccaries (Mammalia, Tayassuidae)

Cladistic analysis of osteological and dental characters in a monophyletic group of Miocene and younger tayassuids demonstrates a pattern of changes in the degree of sexual dimorphism in canine tooth diameter and zygomatic arch width, and in phenotypic correlations between these characters. Primitively, tayassuids have canine teeth that are sexually dimorphic and discretely bimodal in size, and zygomatic arches that are narrow in both sexes. Many late Miocene and Pliocene tayassuids have broad, winglike zygomatic processes. In some species, these processes are large in both sexes, but in others, those of females are much smaller than those of males. The presence of large processes in both sexes is primitive relative to the condition of strong sexual dimorphism. In five separate clades, the zygomatic processes of both sexes become reduced in size, and the degree of sexual dimorphism in canine size becomes reduced as well. The pattern is congruent with predictions derived from a theoretical model of the evolution of sexual dimorphism, and it further indicates the emergence of a new phenotypic correlation between two previously uncorrelated characters, canine size and zygoma size. The advent of this new correlation coincides with the advent of pronounced sexual dimorphism in zygomatic processes. Although such a pattern could be explained by genetically modifying phenotypic expression of homologous characters in one sex or the other, an epigenetic modification of expression is equally plausible: the evolution of sexual dimorphism in homologous characters could be accomplished by placing phenotypic expression of an originally monomorphic character under the control of steroid sex hormones. This hypothesis is consistent with evidence from many vertebrate groups, and it provides testable predictions.

Hupehsuchus , an enigmatic aquatic reptile from the Triassic of China, and the problem of establishing relationships

Hupehsuchus , an aquatic reptile from the Triassic of China, represents a previously unrecognized diapsid order, the Hupehsuchia. Hupehsuchus exhibits a unique combination of skeletal features including very long, completely toothless jaws, bipartite neural spines, a complex pattern of dermal armour above the vertebral column, and laterally compressed, spindle-shaped body form. The pattern of vertebral articulation focuses the greatest amplitude of lateral undulation in the posterior trunk and caudal region. Many derived features of Hupehsuchus are also observed in other groups of Mesozoic diapsid reptiles, but no specific sister-group relationship can be established. The difficulty in determining the relationship of the Hupehsuchia may be attributed to the limited knowledge of the fossil record of diapsid reptiles in the late Permian and early Triassic, as well as the great amount of convergence exhibited by secondarily aquatic reptiles. The principle of parsimony cannot be used directly to identify homologous characters if most of the derived characters are convergent.

The Stochastic Mode of Molecular Evolution: What Consequences for Systematic Investigations?

Biochemical characters have been proposed as ideal sources of phylogenetic information. The homologous characters are easily identified, the relationships between such characters and the underlying genetic code is well understood, and, most importantly, biochemical characters are thought to evolve in a stochastic, clock-like manner. I present a modified version of the Zuckerkandl and Pauling (1965) model of stochastic evolution which is used to explore the consequences of a stochastic mode of evolution. The probability of observing shared character states is determined as a function of the evolutionary rate of a character, the time of independent ancestry for two sister taxa, the time of shared ancestry for the sister taxa independent of their next closest relative, and the number of functionally equivalent, equally probable character states. I found that, while many branching patterns can be reliably reconstructed using stochastically evolving characters, a large subset of theoretically possible phylogenies (as defined by the duration of shared and independent ancestry) would not be derived correctly. The model simulates a "best-case scenario" in which the rate of character evolution is constant over time. Violation of this assumption complicates phylogeny reconstruction and further limits the types of phylogenies that can be addressed with stochastically evolving characters. I discuss the implications of these findings for data analysis and experimental design.