Here, I combine previously underutilized models and priors to perform more biologically realistic phylogenetic inference from morphological data, with an example from squamate reptiles. When coding ...morphological characters, it is often possible to denote ordered states with explicit reference to observed or hypothetical ancestral conditions. Using this logic, we can integrate across character-state labels and estimate meaningful rates of forward and backward transitions from plesiomorphy to apomorphy. I refer to this approach as MkA, for "asymmetric." The MkA model incorporates the biological reality of limited reversal for many phylogenetically informative characters, and significantly increases likelihoods in the empirical data sets. Despite this, the phylogeny of Squamata remains contentious. Total-evidence analyses using combined morphological and molecular data and the MkA approach tend toward recent consensus estimates supporting a nested Iguania. However, support for this topology is not unambiguous across data sets or analyses, and no mechanism has been proposed to explain the widespread incongruence between partitions, or the hidden support for various topologies in those partitions. Furthermore, different morphological data sets produced by different authors contain both different characters and different states for the same or similar characters, resulting in drastically different placements for many important fossil lineages. Effort is needed to standardize ontology for morphology, resolve incongruence, and estimate a robust phylogeny. The MkA approach provides a preliminary avenue for investigating morphological evolution while accounting for temporal evidence and asymmetry in character-state changes.
•Energy is a finite resource and must be allocated among important physiological processes such as reproduction, the stress response, and immunity.•Snakes exhibit a wide variety of reproductive ...strategies and provide a unique study organism.•Timing of the acute stress response shifts throughout the breeding season.•Snakes appear to prioritize reproduction over immunity during energetically expensive processes such as vitellogenesis.
Energy is a finite resource required for all physiological processes and must be allocated efficiently among essential activities to ensure fitness and survival. During the active season, adult organisms are expected to prioritize investment in reproduction over other energetically expensive processes, such as responding to immunological challenges. Furthermore, when encountering a stressor, the balance between reproduction and immunity might be disrupted in order to fuel the stress response. Because of the distinct differences in life histories across species, watersnakes provide a unique group of study in which to examine these tradeoffs. Over a two-year period, we captured three watersnake species throughout Northeast Arkansas. Animals were subjected to restraint stress and blood samples were collected throughout the acute stress response. Blood samples were used to assess innate immunity and steroid hormone concentrations. We found the peak in corticosterone concentration is season-specific, potentially because energetic reserves fluctuate with reproductive activities. We also found body condition was positively related to acute stress and negatively related to immunity. Watersnakes evidently prioritize reproduction over immunity, especially during the energetically intensive process of vitellogenesis. Energetic tradeoffs between reproduction, immunity, and the stress response are complex, and this study contributes to our understanding of energetic shifts in free-living organisms in the context of stress.
Sceloporus aeneus y Sceloporus bicanthalis son especies de reciente evolución, similares en morfología e historia de vida, pero difieren en el modo reproductor y número de escamas cantales. Sin ...embargo, este último carácter es altamente variable y es el único, a una escala morfológica, que se ha usado hasta la fecha para diferenciarlas. En el presente trabajo se analizó el grado de variación morfológica de las escamas cefálicas, mediante morfometría geométrica y estadística multivariada, para determinar si el uso de estos métodos permite separar con mayor precisión ambas especies. Para ello, se utilizaron fotografías digitales de S. aeneus y S. bicanthalis y se colocaron marcas en escamas de la región dorsal, ventral y lateral de la cabeza. Los resultados muestran diferencias significativas en la forma de las escamas entre ambas especies para todas las vistas, de manera que cada especie presenta un morfotipo definido en lo que respecta a la escutelación del cráneo. El análisis sugiere que ambas especies pueden ser identificadas mediante variaciones en la forma de las escamas parietal e interparietal y no por el número de escamas cantales.
A relação dos seres humanos com as serpentes é algo cada vez mais frequente. Tal interação resulta em conhecimentos populares transmitidos ao longo das gerações, construtores de mitos e crendices que ...são traduzidos em sentimentos de medo e repulsa sobre estes répteis. Assim, a utilização de estratégias que destaquem a importância ecológica e ambiental das serpentes são importantes na busca da desmistificação necessária à conservação. Nosso estudo buscou verificar a percepção de estudantes do Ensino Médio da rede pública sobre o tema “serpentes”, utilizando diferentes intervenções pedagógicas. Foram utilizados: grupo focal; aula expositiva dialogada e prática demonstrativa com animais fixados, aplicação de questionário e oficina de produção de modelos e textos. O grupo focal revelou aspectos controversos sobre a biologia destes animais e primeiros-socorros, além de relatos de aversão e crendices. As aulas auxiliaram na promoção da empatia e durante a oficina observamos equívocos na representação de estruturas morfológicas, entretanto, verificamos na produção textual uma mudança de concepção sobre crenças de senso comum. Diante do exposto, sugerimos que na abordagem de temas envoltos em mitos e crendices, sejam adotadas diferentes estratégias didáticas, para a promoção da aprendizagem, buscando a empatia sobre a importância que cada grupo animal exerce na natureza.
Necrosaurus cayluxi is an enigmatic lizard from the Paleogene of the Phosphorites of Quercy, France that was first mentioned in the 19th century. Although it is generally believed that Filhol was the ...author who established this taxon, I am herein demonstrating that authorship should in fact be attributed to Zittel, a fact that also influences not only its generic nomenclature, but also its appropriate type material. As such, the valid name for this taxon should be Palaeovaranus cayluxi and its holotype is a left maxilla. Additionally, Ophisauriscus eucarinatus from the middle Eocene of Geiseltal, Germany, another taxon that was previously assigned to Necrosaurus, is herein shown to be a nomen dubium, whereas Melanosauroides giganteus from the same locality, is considered a valid species and is recombined as Palaeovaranus giganteus comb. nov. The suggested changes in nomenclature also affect “Necrosauridae”, a poorly defined clade of lizards from the Cretaceous–Paleogene of Europe, North America, and Asia. In order to maintain nomenclatural stability and define a monophyletic lineage, I am here establishing the new family Palaeovaranidae fam. nov., which includes solely the genus Palaeovaranus. The known occurrences of Palaeovaranus across the Paleogene of Western Europe are discussed.
Necrosaurus cayluxi est un lézard énigmatique du Paléogène des Phosphorites du Quercy, France, qui a été mentionné pour la première fois au 19e siècle. Bien qu’il soit généralement admis que Filhol est l’auteur qui a établi ce taxon, je démontre ici que la paternité devrait en fait en être attribuée à Zittel, ce qui influence également non seulement la nomenclature générique, mais aussi le matériel type approprié. En tant que tel, le nom valide pour ce taxon devrait être Palaeovaranus cayluxi et son holotype est un maxillaire gauche. En outre, Ophisauriscus eucarinatus de l’Éocène Moyen de Geiseltal, Allemagne, autre taxon précédemment assigné à Necrosaurus, est considéré comme étant un nomen dubium, tandis que Melanosauroides giganteus de la même localité est considéré comme une espèce valable et est recombinée comme Palaeovaranus giganteus comb. nov. Les changements suggérés dans la nomenclature affectent également les « Necrosauridae », un clade mal défini de lézards du Crétacé–Paléogène d’Europe, d’Amérique du Nord et d’Asie. Afin de maintenir la stabilité de la nomenclature et de définir une lignée monophylétique, j’établis ici la nouvelle famille Palaeovaranidae fam. nov., qui comprend uniquement le genre Palaeovaranus. Les exemples connus de Palaeovaranus à travers le Paléogène d’Europe occidentale sont discutés.
Snakes represent the richest Reptile group in Brazil, amounting to 412 species and 40% of them are endemic for the country. This great richness combined with the poor taxonomic knowledge makes the ...identification a difficult process. To correctly identify a specimen, guides, taxonomic revisions, identification keys, and consulting specialists are the most used methods. Identification keys are based on separation and segregation of characters, where the chosen paths lead to the appropriate taxa. These tools are normally used by students and non-taxonomists. Also, they can be very helpful with the general public, where they can identify the species with simple characters. This study aims to develop keys for the snakes from the State of Santa Catarina state, Brazil, focusing on the Itajaí Valley species. We surveyed 351 specimens deposited in Universidade Regional de Blumenau Zoological Collection (CZFURB), Universidade Federal de Santa Catarina (CHUFSC), and Natural History Museum of Capão da Imbuia (MHNCI) herpetological collections. Characters including pholidosis, dentition, and coloration patterns were examined from the 46 snake species registered from Itajaí Valley.
Modern squamates (lizards, snakes and amphisbaenians) are the world's most diverse group of tetrapods along with birds
and have a long evolutionary history, with the oldest known fossils dating from ...the Middle Jurassic period-168 million years ago
. The evolutionary origin of squamates is contentious because of several issues: (1) a fossil gap of approximately 70 million years exists between the oldest known fossils and their estimated origin
; (2) limited sampling of squamates in reptile phylogenies; and (3) conflicts between morphological and molecular hypotheses regarding the origin of crown squamates
. Here we shed light on these problems by using high-resolution microfocus X-ray computed tomography data from the articulated fossil reptile Megachirella wachtleri (Middle Triassic period, Italian Alps
). We also present a phylogenetic dataset, combining fossils and extant taxa, and morphological and molecular data. We analysed this dataset under different optimality criteria to assess diapsid reptile relationships and the origins of squamates. Our results re-shape the diapsid phylogeny and present evidence that M. wachtleri is the oldest known stem squamate. Megachirella is 75 million years older than the previously known oldest squamate fossils, partially filling the fossil gap in the origin of lizards, and indicates a more gradual acquisition of squamatan features in diapsid evolution than previously thought. For the first time, to our knowledge, morphological and molecular data are in agreement regarding early squamate evolution, with geckoes-and not iguanians-as the earliest crown clade squamates. Divergence time estimates using relaxed combined morphological and molecular clocks show that lepidosaurs and most other diapsids originated before the Permian/Triassic extinction event, indicating that the Triassic was a period of radiation, not origin, for several diapsid lineages.
The oldest evidence of a human presence in western Europe is currently documented at the late Early Pleistocene sites of Barranco León and Fuente Nueva 3 (Guadix-Baza Basin, SE Spain), dated ...respectively to 1.4 and 1.2 Ma. Understanding the climatic variability that these hominins encountered and coped with is of outstanding importance for placing their activities in an ecological context and understanding their capacity to adapt to changing conditions. Glacial-interglacial variability during this period was considerably less intense than during later phases of the Pleistocene. To date, however, no quantitative estimates are available for this climate variability in Early Pleistocene hominin sites, and no ‘cold’ reconstructions directly associated with the early hominin occupations of Europe have been performed either. Here stratigraphically constrained quantitative climatic reconstructions are provided for the sites of Barranco León and Fuente Nueva 3, using an improvement on the Mutual Ecogeographic Range method by projecting the niche envelope of the extant representatives of Ophisaurus sp. We ascertain differences in temperature and rainfall between the different layers of the two sites, in line with previous reconstructions that revealed warm, humid periods (‘interglacial’) as well as more temperate but drier periods (‘glacial’'), consistent with Early Pleistocene climate cyclicity. Our new estimates suggest that late Early Pleistocene hominins, though conditioned to some degree by climatic factors, were able to deal with changing climatic and environmental conditions (‘interglacial’ and ‘glacial’') in the southwestern extremity of the European continent.
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•The oldest human evidence in western Europe is currently documented at 1.4 Ma.•Understanding the climatic variability that these hominins encountered is relevant.•Paleoclimatic data are provided for an archaeopaleontological sequence.•The Early Pleistocene hominins were able to cope with changing climatic conditions.
Targeted sequence capture is becoming a widespread tool for generating large phylogenomic data sets to address difficult phylogenetic problems. However, this methodology often generates data sets in ...which increasing the number of taxa and loci increases amounts of missing data. Thus, a fundamental (but still unresolved) question is whether sampling should be designed to maximize sampling of taxa or genes, or to minimize the inclusion of missing data cells. Here, we explore this question for an ancient, rapid radiation of lizards, the pleurodont iguanians. Pleurodonts include many well-known clades (e.g., anoles, basilisks, iguanas, and spiny lizards) but relationships among families have proven difficult to resolve strongly and consistently using traditional sequencing approaches. We generated up to 4921 ultraconserved elements with sampling strategies including 16, 29, and 44 taxa, from 1179 to approximately 2.4 million characters per matrix and approximately 30% to 60% total missing data. We then compared mean branch support for interfamilial relationships under these 15 different sampling strategies for both concatenated (maximum likelihood) and species tree (NJst) approaches (after showing that mean branch support appears to be related to accuracy). We found that both approaches had the highest support when including loci with up to 50% missing taxa (matrices with ~40-55% missing data overall). Thus, our results show that simply excluding all missing data may be highly problematic as the primary guiding principle for the inclusion or exclusion of taxa and genes. The optimal strategy was somewhat different for each approach, a pattern that has not been shown previously. For concatenated analyses, branch support was maximized when including many taxa (44) but fewer characters (1.1 million). For species-tree analyses, branch support was maximized with minimal taxon sampling (16) but many loci (4789 of 4921). We also show that the choice of these sampling strategies can be critically important for phylogenomic analyses, since some strategies lead to demonstrably incorrect inferences (using the same method) that have strong statistical support. Our preferred estimate provides strong support for most interfamilial relationships in this important but phylogenetically challenging group.
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