Andrew J. Crawford

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Verified

Andrew verified their affiliation via an institutional email.

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• Ph.D.
• Professor (Associate) at Los Andes University (Colombia)

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. Th...

The Craugastor podiciferus Species Group contains eleven species of terraranan frogs distributed from eastern Honduras to eastern Panama. All species have remarkable color pattern polymorphisms, which may contribute to potential taxonomic problems. We performed exhaustive sampling throughout the geographic distribution of the group to evaluate the...

Identifying populations at highest risk from climate change is a critical component of conservation efforts. However, vulnerability assessments are usually applied at the species level, even though intraspecific variation in exposure, sensitivity and adaptive capacity play a crucial role in determining vulnerability. Genomic data can inform intrasp...

Amphibians represent a diverse group of tetrapods, marked by deep divergence times between their three systematic orders and families. Studying amphibian biology through the genomics lens increases our understanding of the features of this animal class and that of other terrestrial vertebrates. The need for amphibian genomic resources is more urgen...

Although biologists have described biofluorescence in a diversity of taxa, there have been few systematic efforts to document the extent of biofluorescence within a taxonomic group or investigate its general significance. Through a field survey across South America, we discover and document patterns of biofluorescence in tropical amphibians. We mor...

Amphibians are the most threatened major group of vertebrates worldwide and yet they are lagging behind other taxa in genomic resources that could aid in their conservation management. Here, we provide a status update on genomics technologies, how they have been used in amphibian research, and an outlook on how these approaches could inform future...

Amphibians are the most threatened group of vertebrates and are in dire need of conservation intervention to ensure their continued survival. They exhibit unique features including a high diversity of reproductive strategies, permeable and specialized skin capable of producing toxins and antimicrobial compounds, multiple genetic mechanisms of sex d...

As the most threatened vertebrate class on earth, amphibians are at the forefront of the biodiversity crisis, with the recognition of global amphibian declines and extinctions dating back several decades now. The current Amphibian Conservation Action Plan is adopting two strategies to address the goal of the amelioration of the amphibian crisis: th...

Amphibians represent a diverse group of tetrapods, marked by deep divergence times between their three systematic orders and families. Studying amphibian biology through the genomics lens increases our understanding of the features of this animal class and that of other terrestrial vertebrates. The need for amphibian genomics resources is more urge...

The number of amphibian species described yearly shows no signs of slowing down, especially in tropical regions, implying that the biodiversity of amphibians remains woefully underestimated. We describe a new species of poison frog from the Pacific lowlands of southwestern Colombia: Epipedobates currulao sp. nov., named for the Pacific music and da...

Dendropsophus molitor is a hylid frog endemic to the Eastern Cordillera of the Colombian Andes, where it exhibits extensive geographic variation in size and colour pattern. Previous multivariate analyses of acoustic and genetic data suggested that northern and southern populations of D. molitor were distinct lineages, and consequently, the northern...

Our study assesses the variability of amphibian biofluorescence and provides insight into its potential functions and role in anuran evolution. Via a field survey across South America, we discovered and documented patterns of biofluorescence in tropical amphibians. We more than tripled the number of species that have been tested for this trait and...

Amphibians are the most threatened group of vertebrates and are in dire need of conservation intervention to ensure their continued survival. They have many unique features including a high diversity of reproductive strategies, permeable and specialized skin capable of producing toxins and antimicrobial compounds, multiple genetic mechanisms of sex...

Ranaviruses can cause mass mortality events in amphibians, thereby becoming a threat to populations that are already facing dramatic declines. Ranaviruses affect all life stages and persist in multiple amphibian hosts. The detrimental effects of ranavirus infections to amphibian populations have already been observed in the UK and in North America....

The recurrent evolution of resistance to cardiotonic steroids (CTS) across diverse animals most frequently involves convergent amino-acid substitutions in the H1-H2 extracellular loop of Na+, K + -ATPase (NKA). Previous work revealed that hystricognath rodents (e.g. chinchilla) and pterocliform birds (sandgrouse) have convergently evolved amino-aci...

The recurrent evolution of resistance to cardiotonic steroids (CTS) across diverse animals most frequently involves convergent amino-acid substitutions to the H1-H2 extracellular loop of Na+,K+-ATPase (NKA). Previous work established that hystricognath rodents (e.g. chinchilla) and pterocliform birds (sandgrouse) have convergently evolved amino-aci...

A growing body of theoretical and experimental evidence suggests that intramolecular epistasis is a major determinant of rates and patterns of protein evolution and imposes a substantial constraint on the evolution of novel protein functions. Here, we examine the role of intramolecular epistasis in the recurrent evolution of resistance to cardioton...

Background Studies in vertebrate genomics require sampling from a broad range of tissue types, taxa, and localities. Recent advancements in long-read and long-range genome sequencing have made it possible to produce high-quality chromosome-level genome assemblies for almost any organism. However, adequate tissue preservation for the requisite ultra...

The Pacific coast of Colombia is characterized by mangrove ecosystems which play a crucial role as possible nurseries for juvenile sharks. However, trophic food webs from coastal ecosystems are heavily disturbed by increased fishing pressure, which affects numerous shark species. In this region of the Eastern Tropical Pacific (ETP), fisheries’ data...

High-quality reference genomes for non-model species can benefit conservation.

Vicariance is the simplest explanation for divergence between sister lineages separated by a potential barrier, and the northern Andes would seem to provide an ideal example of a vicariant driver of divergence. We evaluated the potential role of the uplift of the Eastern Cordillera (EC) of the Colombian Andes and the Mérida Andes (MA) of Venezuela...

PNAS 2022. Vol. 119 (4)e2115641119. https://doi.org/10.1073/pnas.2115641119

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban...

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban...

Natural history collections are essential to a wide variety of studies in biology because they maintain large collections of specimens and associated data, including genetic material (e.g., tissues) for DNA sequence data, yet they are currently under-funded and collection staff have high workloads. With the advent of aggregate databases and advance...

The complex topography of the species-rich northern Andes creates heterogeneous environmental landscapes that are hypothesized to have promoted population fragmentation and diversification by processes such as vicariance or local adaptation. Previous phylogenetic work on the palm rocket frog (Anura: Aromobatidae: Rheobates spp.), endemic to midelev...

November 2020 marked 2 y since the launch of the Earth BioGenome Project (EBP), which aims to sequence all known eukaryotic species in a 10-y timeframe. Since then, significant progress has been made across all aspects of the EBP roadmap, as outlined in the 2018 article describing the project’s goals, strategies, and challenges (1). The launch phas...

A global international initiative, such as the Earth BioGenome Project (EBP), requires both agreement and coordination on standards to ensure that the collective effort generates rapid progress toward its goals. To this end, the EBP initiated five technical standards committees comprising volunteer members from the global genomics scientific commun...

The 2016 Peace Agreement has increased access to Colombia’s unique ecosystems, which remain understudied and increasingly under threat. The Colombian government has recently announced its National Bioeconomic Strategy (NBS), founded on the sustainable characterization, management, and conservation of the nation's biodiversity as a means to achieve...

The term ‘mate guarding’ refers to the monopolization of the reproductive potential of a conspecific. Mate guarding has been recorded in invertebrates and vertebrates, but is poorly known in anuran amphibians (frogs and toads), the terrestrial vertebrates with the highest diversity of reproductive modes. Mate guarding in anurans may consist of a pr...

A growing body of theoretical and experimental evidence suggests that intramolecular epistasis is a major determinant of rates and patterns of protein evolution and imposes a substantial constraint on the evolution of novel protein functions. Here, we examine the role of intramolecular epistasis in the case of the recurrent evolution of resistance...

Studies in vertebrate genomics require sampling from a broad range of tissue types, taxa, and localities. Recent advancements in long-read and long-range genome sequencing have made it possible to produce high-quality chromosome-level genome assemblies for almost any organism. However, adequate tissue preservation for the requisite ultra-high molec...

Terraranae is a large clade of New World direct-developing frogs that includes 3–5 families and >1,100 described species (∼15% of all named frog species). The relationships among major groups of terraranan frogs have been highly contentious, including conflicts among four recent phylogenomic studies utilizing 95, 220, 389, and 2,214 nuclear loci, r...

Boana xerophylla is a common treefrog widely distributed in northern Brazil, Colombia, French Guiana, Guyana, Panama, Suriname, Trinidad and Tobago, and Venezuela. A recent study found molecular, acoustic, and morphometric differences between the populations located on opposite sides of the Orinoco River. Here, we carry out an updated molecular phy...

High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and biodiversity conservation. However, such assemblies are available for only a few non-microbial species1–4. To address this issue, the international Genome 10K (G10K) consortium5,6 has worked over a five-year period to evalu...

Although gene duplication is an important source of evolutionary innovation, the functional divergence of duplicates can be opposed by ongoing gene conversion between them. Here, we report on the evolution of a tandem duplication of Na+,K+-ATPase subunit α1 (ATP1A1) shared by frogs in the genus Leptodactylus, a group of species that feeds on toxic...

Reproductive phenology of snakes varies widely among species, likely influenced by biotic and abiotic factors related to seasonality. In Neotropical regions, where seasonal variation in temperature and photoperiod is minimal, the factors regulating the reproductive phenology of snakes remain poorly known, despite the great diversity of species foun...

The outstanding biodiversity of the Guiana Shield has raised many questions about its origins and evolution. Frogs of the genera Adelastes, Otophryne and Synapturanus form an ancient lineage distributed mostly across this region. These genera display strikingly disparate morphologies and life-history traits. Notably, Synapturanus is conspicuously a...

Gigantism results when one lineage within a clade evolves extremely large body size relative to its small-bodied ancestors, a common phenomenon in animals. Theory predicts that the evolution of giants should be constrained by two tradeoffs. First, because body size is negatively correlated with population size, purifying selection is expected to be...

Isthmian Central America (ICA) is one of the most biodiverse regions in the world, hosting an exceptionally high number of species per unit area. ICA was formed <25 million years ago and, consequently, its biotic assemblage is relatively young and derived from both colonization and in situ diversification. Despite intensive taxonomic work on the lo...

Populations of amphibians are experiencing severe declines worldwide. One group with the most catastrophic declines is the Neotropical genus Atelopus (Anura: Bufonidae). Many species of Atelopus have not been seen for decades and all eight Central American species are considered "Critically Endangered", three of them very likely extinct. Nonetheles...

Aim We investigate the spatiotemporal context of the diversification of Allobates, a widespread genus of Amazonian frogs with high species diversity particularly in western Amazonia. We tested if that diversity originated in situ or through repeated dispersals from other Amazonian areas and if this diversification took place during or after the Peb...

The complex topography of the species-rich northern Andes creates heterogeneous environmental landscapes that are hypothesized to have promoted population fragmentation and diversification by vicariance, gradients and/or the adaptation of species. Previous phylogenetic work on the Palm Rocket Frog (Anura: Aromobatidae: Rheobates spp.), endemic to m...

Gene duplication is an important source of evolutionary innovation, but the adaptive division-of-labor between duplicates can be opposed by ongoing gene conversion between them. Here we document a tandem duplication of Na ⁺ ,K ⁺ -ATPase subunit α1 (ATP1A1) shared by frogs in the genus Leptodactylus , a group of species that feeds on toxic toads. On...

High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and biodiversity conservation. However, such assemblies are only available for a few non-microbial species. To address this issue, the international Genome 10K (G10K) consortium has worked over a five-year period to evaluate an...

Aim To evaluate the potential role of the orogeny of the Eastern Cordillera (EC) of the Colombian Andes and the Mérida Andes (MA) of Venezuela as drivers of vicariance between populations of 37 tetrapod lineages co-distributed on both flanks, through geological reconstruction and comparative phylogeographic analyses. Location Northwestern South Am...

Background: Terraranae is a large clade of New World direct-developing frogs that includes 3–5 families and >1,000 described species, encompassing ~15% of all named frog species. The relationships among major groups of terraranan frogs have been highly contentious, including conflicts among three recent phylogenomic studies utilizing 95, 389, and 2...

Eastern Panamá is within the Mesoamerican biodiversity hotspot and supports an understudied amphibian fauna. Here we characterize the amphibian diversity across an elevational gradient in one of the least studied mountain ranges in eastern Panamá, Serranía de Majé. A total of 38 species were found, which represent 17% of all species reported for Pa...

Mountain chains and rivers are often found to represent barriers promoting vicariant differentiation in terrestrial vertebrates. Previous studies have supported the idea that the Cordillera de Mérida (CM), the easternmost branch of the Northern Andes, represents a geographic barrier for vertebrates, including frogs. Previous studies have also sugge...

Recent climatic models suggest the late Pleistocene was colder and had different precipitation regimes from the present. If this climatic shift occurred more rapidly than species could adapt, species likely shifted their ranges as populations moved in concert with suitable environmental conditions. We examined changes in altitudinal and horizontal...

Genomics has great potential to advance understanding of amphibian evolution, ecology, and behavior, as well as to improve conservation of this highly imperiled class of vertebrates. However, application of new massively parallel sequencing technology to amphibians lags behind its application to other vertebrates, due in part to their large, repeti...

Gigantism is the result of one lineage within a clade evolving extremely large body size relative to its small-bodied ancestors, a phenomenon observed numerous times in animals. Theory predicts that the evolution of giants should be constrained by two tradeoffs. First, because body size is negatively correlated with population size, purifying selec...

The tempo of evolutionary change through time is among the most heavily studied dimensions of macroevolution using phylogenies. Here, we present a simple, likelihood‐based method for comparing the rate of phenotypic evolution for continuous characters between trees. Our method is derived from a previous approach published by Brian O'Meara and colle...

A key goal of ecology and evolution is to understand the relative contributions of environment and history in determining the geographic distribution of organisms. For the Neotropical lowlands, where temperatures are similar across landscapes, we hypothesize that water balance may be a critical but understudied factor in determining the distributio...

Phylogenomic approaches offer a wealth of data, but a bewildering diversity of methodological choices. These choices can strongly affect the resulting topologies. Here, we explore two controversial approaches (binning genes into "supergenes" and inclusion of only rapidly evolving sites), using new data from hyloid frogs. Hyloid frogs encompass ∼53%...

Global amphibian declines have been attributed to several factors including the chytrid fungal pathogen, Batrachochytrium dendrobatidis (Bd), that infects hosts’ skin and causes death by inhibiting immune response and impairing osmoregulatory function. Here, we integrate extensive new field data with previously published locality records of Bd in C...

We conducted a molecular assessment of Colostethus-like frogs along an elevational gradient in the Serranía de Pirre, above Santa Cruz de Cana, eastern Panama, aiming to establish their species identity and to determine the altitudinal distribution of C. latinasus. Our findings confirm the view of C. latinasus as an endemic species restricted to th...

Background: Antarctica is surrounded by the Antarctic Circumpolar Current (ACC), the largest and strongest current in the world. Despite its potential importance for shaping biogeographical patterns, the distribution and connectivity of deep-sea populations across the ACC remain poorly understood. In this study we conducted the first assessment of...

In this report, we describe a new species of the Craugastor podiciferus species group from the premontane forest of the Pacific versant along the Costa Rican-Panamanian border. Mitochondrial DNA and karyotype analyses previously showed a marked genetic divergence between populations of the premontane forest of the Fila Costeña and the lowlands Sout...

Recent geological studies demonstrate that the Isthmus of Panama emerged some 10 m.y. earlier than previously assumed. Although absent today in Panama, Central American savanna environments likely developed in connection with the onset of Northern Hemisphere glaciations. As is widely recognized, most of the mammals crossing the isthmus since 2.5 Ma...

A new species of Pristimantis is described from an Andean cloud forest at 2650 m in the Cordillera Oriental of Colombia. Pristimantis dorado sp. nov. is similar to and could be closely related to P. acutirostris, but can be readily distinguished from this latter species by the absence of a tympanic annulus, vocal slits, vocal sac and reticulations...

Amphibians around the world are declining from threats that cannot currently be mitigated, making it impossible to safeguard some species in their natural habitats. Amphibians in the mountainous neotropics are one example where severe disease-related declines prompted calls for the establishment of captive assurance colonies to avoid extinctions. W...

Understanding the phylogenetic and geographical history of Neotropical lineages requires having adequate geographic and taxonomic sampling across the region. However, Colombia has remained a geographical gap in many studies of Neotropical diversity. Here we present a study of Neotropical skinks of the genus Mabuya, reptiles that are difficult to id...

Hypotheses to explain phylogeographic structure traditionally invoke geographic features, but often fail to provide a general explanation for spatial patterns of genetic variation. Organism's intrinsic characteristics might play more important roles than landscape features in determining phylogeographic structure. We developed a novel comparative a...

Colombia hosts the second highest amphibian species diversity on Earth, yet its fauna remains poorly studied, especially using molecular genetic techniques. We present the results of the first wide-scale DNA barcoding survey of anurans of Colombia, focusing on a transect across the Eastern Cordillera. We surveyed 10 sites between the Magdalena Vall...

The Genome 10K Project was established in 2009 by a consortium of biologists and genome scientists determined to facilitate the sequencing and analysis of the complete genomes of 10,000 vertebrate species. Since then the number of selected and initiated species has risen from ∼26 to 277 sequenced or ongoing with funding, an approximately tenfold in...

Species distributed across vast continental areas and across major biomes provide unique model systems for studies of biotic diversification, yet also constitute daunting financial, logistic and political challenges for data collection across such regions. The tree frog Dendropsophus minutus (Anura: Hylidae) is a nominal species, continentally dist...

Aim: The frog genus Rheobates (Anura: Aromobatidae) is endemic to mid-elevations in the Colombian Andes. Our aim was to evaluate the role of the northern Andean high peaks and the low Magdalena Valley in creating bar- riers to dispersal and promoting vicariance within Rheobates. Location: Three disjunct mid-elevation flanks of the northern Colombi...

Dendrobatid frogs are among the best known anurans in the world, mainly due to their toxicity and associated bright colors. A recently described dendrobatid genus, Andinobates. comprises frogs distributed among the Colombian Andes and Panama. During field work in the Distrito de Donoso, Colón province, Panama, we found a poison frog that we here de...

Species distributed across vast continental areas and across major biomes provide unique model systems for studies of biotic diversification, yet also constitute daunting financial, logistic and political challenges for data collection across such regions. The tree frog Dendropsophus minutus (Anura: Hylidae) is a nominal species, continentally dist...

Saturation is the idea that a community is effectively filled with species, such that no more can be added without extinctions. This concept has important implications for many areas of ecology, such as species richness, community assembly, invasive species and climate change. Here, we illustrate how biogeography can be used to test for community s...

Background / Purpose: We developed a comparative genomics pipeline that can lead to the identification of candidate genes responsible for certain ecological characteristics. The pipeline, Deconstructive Evolutionary Pipeline (DeEP), can be employed to answer two main questions: what genes were most likely gained or lost in the evolutionary histor...

The pathogenic chytrid fungus, Batrachochytrium dendrobatidis (Bd), constitutes a significant threat to more than 790 amphibian species occurring in Colombia. To date there is no molecular or morphological description of strains infecting Colombian populations. Here we report the genetic and morphological characterization of the first Colombian iso...

Amphibians constitute a diverse yet still incompletely characterized clade of vertebrates, in which new species are still being discovered and described at a high rate. Amphibians are also increasingly endangered, due in part to disease-driven threats of extinctions. As an emergency response, conservationists have begun ex situ assurance colonies f...

DNA barcoding facilitates the identification of species and the estimation of biodiversity by using nucleotide sequences, usually from the mitochondrial genome. Most studies accomplish this task by using the gene encoding cytochrome oxidase subunit I (COI; Entrez COX1). Within this barcoding framework, many taxonomic initiatives exist, such as thos...

Molecular markers offer a universal source of data for quantifying biodiversity. DNA barcoding uses a standardized genetic marker and a curated reference database to identify known species and to reveal cryptic diversity within wellsampled clades. Rapid biological inventories, e.g. rapid assessment programs (RAPs), unlike most barcoding campaigns,...

The Andes of South America hosts perhaps the highest amphibian species diversity in the world, and a sizable component of that diversity is comprised of direct-developing frogs of the genus Pristimantis (Anura: Craugastoridae). In order to better understand the initial stages of species formation in these frogs, this study quantified local-scale sp...

Posterior probability distributions for gene flow from IMa analysis. (TIF)

The completion of the land bridge between North and South America approximately 3.5-3.1 million years ago (Ma) initiated a tremendous biogeographic event called the Great American Biotic Interchange (GABI), described principally from the mammalian fossil record. The history of biotic interchange between continents for taxonomic groups with poor fos...