David Salazar-Valenzuela

Diverse organisms use toxins as antipredator defenses. Although many taxa synthesize their toxins, dietary toxin acquisition is less documented, particularly in vertebrates. In poison frogs (Dendrobatidae), efficient sequestration of dietary alkaloids evolved at least three times from ancestors that bore at most trace concentrations of skin alkaloids. Yet molecular mechanisms underlying poison-frog sequestration remain poorly understood. We used two approaches to address this. First, we performed a broad phylogenetic analysis of the serpinA gene family, which includes serpina1 -like/alkaloid-binding globulin (ABG), the putative dendrobatid alkaloid transporter, and biliverdin-binding serpins (BBSs), which bind and spectrally tune biliverdin in blue-green arboreal frogs. Second, we used an evolutionarily narrower but discovery-oriented liver gene-expression analysis, contrasting seven populations from two sequestering Epipedobates species, the most recent origin of sequestration among dendrobatids (Silverstoneia and Hyloxalus . Phylogenetic analyses revealed extensive diversification of ABGs and BBS-like genes in Dendrobatidae, forming two and five major clades, respectively. These expansions reveal broader ligand-binding serpin diversity than previously recognized and indicate that alkaloid sequestration may involve multiple ABG paralogs. Gene-expression analyses revealed 23 candidate genes associated with small-molecule transport, xenobiotic metabolism, and immune response, including serpina1 -like, which was overexpressed in Epipedobates . A co-expression network analysis independently placed 20 of the 23 candidates into four key modules (enriched for differentially-expressed genes, containing ≥1 candidate, and correlated with sequestration). Our findings point to ligand-binding-protein diversification and coordinated gene-expression changes as major contributors to the evolution of alkaloid defenses in poison frogs.

Ecuador is one of earths’ most biodiverse countries. Scorpions are one of its particularly diverse animal groups and, unsurprisingly, scorpion sting causes a major public health issue across Ecuador. However, despite their medical relevance, little research has been carried out to understand the problem in more detail. Here, we contribute to the battle against scorpion envenoming in Ecuador by providing a holistic synthesis of different key aspects. We discuss i) what is known about the Ecuadorian scorpion diversity, ii) epidemiology, as well as iii) medical care and toxinology. We show that the scorpion fauna of Ecuador is diverse but not fully inventoried due to absence of integrative perspectives. Further, we demonstrate that certain scorpion sting hotspots exist across the country, yet the problem is widespread across Ecuador and fatalities can occur virtually anywhere. As for antivenom, no local remedy is produced, and the effectiveness of imported antivenoms needs to be established. Lastly, almost nothing is known about the venoms and venom toxins from Ecuadorian scorpions, rendering strategic venomic surveys as an important research priority in the future. Taken together, we highlight several key areas in which additional bodies of knowledge need to be established and provide a basis for future, in depth studies on the various aspects related to scorpion sting in Ecuador, particularly in taxonomy, natural history, epidemiology and toxinology.

Despite growing investments in nature-based solutions for urban resilience, their design often overlooks a fundamental biological process: evolution. Populations of organisms that sustain nature-based solutions are dynamic and can evolve over time. Rapid evolutionary changes, driven by urban environmental stressors, such as pollution, climate extremes, and habitat fragmentation, can reshape species’ traits, alter interactions, and shift ecosystem functions. We synthesize evidence of evolutionary change across systems that serve as nature-based solutions in urban contexts and show how evolutionary processes can enhance or undermine their performance. We propose four testable hypotheses linking evolutionary dynamics to nature-based solutions and outline design strategies to maintain adaptive potential. Integrating evolution into nature-based solutions is essential to ensure long-term and efficient functionality under accelerating environmental change.

Harlequin frogs, genus Atelopus, are a species-rich group of bufonid anurans from the Neotropics with more than 100 species. For nearly four decades now, this group has suffered from massive population declines. Almost all species are threatened with extinction, and many populations and several species are considered extinct or possibly extinct. This results in a limited sampling available for studies on harlequin frog systematics, especially in terms of molecular genetic information. However, efficient conservation of harlequin frogs requires an improved taxonomy. This is further complicated through the circumstance that many Atelopus species are relatively poor in external morphological characters combined with a high level of intra-specific character variation (e.g. coloration and body size). At the same time, cryptic diversity exists with well differentiated species (supported by osteology and molecular genetics) almost indistinguishable by external morphology. We compiled the largest dataset to date for mitochondrial (12S, 16S, cyt b) and nuclear (POMC, RAG1) markers and present a phylogeny (likelihood and Bayesian inference methods) including 152 samples from 104 populations scattered over the entire geographic range of the genus. Four allo- or parapatric main clades are distinguished: I. Sierra Nevada; II. Venezuelan-Andean; III. Andean-Chocó-Central American (with the ignescens and the varius-longirostris clades); and IV Amazonian (containing the tricolor and the flavescens-spumarius clades). The phylogenetic relationships within these clades remain to be resolved. Taxonomic implications included both splitting and lumping, but taxonomic action is here only taken for populations related to A. spumarius from western Amazonia. Besides redescriptions of A. spumarius sensu stricto and A. colomai, we describe two new species based on morphology, skull osteology and bioacoustics. Additional yet understudied populations from Amazonia may be allocated to these species or may represent additional undescribed taxa.

Anacondas, genus Eunectes, are a group of aquatic snakes with a wide distribution in South America. The taxonomic status of several species has been uncertain and/or controversial. Using genetic data from four recognized anaconda species across nine countries, this study investigates the phylogenetic relationships within the genus Eunectes. A key finding was the identification of two distinct clades within Eunectes murinus, revealing two species as cryptic yet genetically deeply divergent. This has led to the recognition of the Northern Green Anaconda as a separate species (Eunectes akayima sp. nov), distinct from its southern counterpart (E. murinus), the Southern Green Anaconda. Additionally, our data challenge the current understanding of Yellow Anaconda species by proposing the unification of Eunectes deschauenseei and Eunectes beniensis into a single species with Eunectes notaeus. This reclassification is based on comprehensive genetic and phylogeographic analyses, suggesting closer relationships than previously recognized and the realization that our understanding of their geographic ranges is insufficient to justify its use as a separation criterion. We also present a phylogeographic hypothesis that traces the Miocene diversification of anacondas in western South America. Beyond its academic significance, this study has vital implications for the conservation of these iconic reptile species, highlighting our lack of knowledge about the diversity of the South American fauna and the need for revised strategies to conserve the newly identified and reclassified species.

Predatory innovations impose reciprocal selection pressures upon prey. The evolution of snake venom alpha-neurotoxins has triggered the corresponding evolution of resistance in the post-synaptic nicotinic acetylcholine receptors of prey in a complex chemical arms race. All other things being equal, animals like caecilians (an Order of legless amphibians) are quite vulnerable to predation by fossorial elapid snakes and their powerful alpha-neurotoxic venoms; thus, they are under strong selective pressure. Here, we sequenced the nicotinic acetylcholine receptor alpha-1 subunit of 37 caecilian species, representing all currently known families of caecilians from across the Americas, Africa, and Asia, including species endemic to the Seychelles. Three types of resistance were identified: (1) steric hindrance from N-glycosylated asparagines; (2) secondary structural changes due to the replacement of proline by another amino acid; and (3) electrostatic charge repulsion of the positively charged neurotoxins, through the introduction of a positively charged amino acid into the toxin-binding site. We demonstrated that resistance to alpha-neurotoxins convergently evolved at least fifteen times across the caecilian tree (three times in Africa, seven times in the Americas, and five times in Asia). Additionally, as several species were shown to possess multiple resistance modifications acting synergistically, caecilians must have undergone at least 20 separate events involving the origin of toxin resistance. On the other hand, resistance in non-caecilian amphibians was found to be limited to five origins. Together, the mutations underlying resistance in caecilians constitute a robust signature of positive selection which strongly correlates with elapid presence through both space (sympatry with caecilian-eating elapids) and time (Cenozoic radiation of elapids). Our study demonstrates the extent of convergent evolution that can be expected when a single widespread predatory adaptation triggers parallel evolutionary arms races at a global scale.

Thoroughly documenting prey items and diet composition is crucial for understanding a predator’s role in the ecosystem. In gape restricted predators, such as snakes, documenting and analyzing the type and size of the prey is important to interpret their ecological role. We describe the diet patterns of a species of venomous snake, the Terciopelo pit viper (Bothrops asper), from its Ecuadorian populations. Examining the gastrointestinal contents of museum specimens collected over an extensive area of the Pacific lowlands of Ecuador, we encountered 69 identifiable prey items from four major taxonomic groups (amphibians, centipedes, mammals, and reptiles). We evaluated the observed composition of prey to check for differences between sexes and size-classes. To complement our observations of the Terciopelo species complex throughout their distribution, we carried out a systematic literature review. Our data show an ontogenetic shift in diet, with a transition from more diverse diet in juveniles towards a mammal-specialized diet in adults, and distinct proportion of prey taxa between the sexes in the juvenile size class.