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Martin Wikelski - One of the best experts on this subject based on the ideXlab platform.
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Biochemical and microbiological evidence for fermentative digestion in free-living land iguanas (Conolophus pallidus) and marine iguanas (Amblyrhynchus cristatus) on the Galapagos archipelago
Physiological and Biochemical Zoology, 2014Co-Authors: Roderick I. Mackie, Mathew Rycyk, Rebecca L. Ruemmler, Rustam Aminov, Martin WikelskiAbstract:Abstract Herbivorous lizards are potentially capable of high digestive efficiency, but the presence of an indigenous microbial population has been implied from measurements of activity rather than directly studied. This study is the first to provide direct biochemical and microbiological evidence for fermentative digestion in free‐living land iguanas (Conolophus pallidus) and marine iguanas (Amblyrhynchus cristatus) from the Galapagos archipelago. In marine iguanas, the stomach and large capacious colon contained ca. 32% and 60%, respectively, of the weight of total gut content. Total volatile fatty acid concentration was ca. 150 and 180 mM, respectively, for marine and land iguanas. Molar proportions of acetate, propionate, and butyrate (80.3%, 9.5%, and 3.5%) in land iguana fecal samples were similar to those for marine iguanas. Examination of fecal samples using confocal and transmission electron microscopy, as well as cultivable counts, revealed a dense and diverse population of bacteria, with spores ...
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Genetic Differentiation between Marine Iguanas from Different Breeding Sites on the Island of Santa Fé (Galápagos Archipelago)
Journal of Heredity, 2010Co-Authors: Deborah Lanterbecq, Maren N. Vitousek, Scott Glaberman, Sebastian Steinfartz, Martin Wikelski, Edgar Benavides, Adalgisa CacconeAbstract:We studied patterns of genetic diversity within and among 5 populations (318 individuals) of Galapagos marine iguanas (Amblyrhynchus cristatus) from the island Santa Fe ´. Populations were separated by distances of 0.2 to 9.9 km. We sequenced 1182 base pairs of the mitochondrial control region and screened 13 microsatellite loci for variability. We also added data from 5 populations (397 individuals) sampled on 4 neighboring islands (Santa Cruz, Floreana, Espanola, and San Cristobal). The 5 Santa Fepopulations, revealed as genetically distinct from populations on other islands, present relatively low levels of genetic diversity, which are similar for both microsatellite (average observed heterozygosity from 0.7686 to 0.7773) and mitochondrial DNA (mtDNA) markers (haplotypic and nucleotide diversity from 0.587 to 0.728 and from 0.00079 to 0.00293, respectively), and comparable with those observed in similar-sized sampling sites on other islands. There was frequency-based evidence of genetic structure between northern and southern sites on Santa Fe ´( Fst of 0.0027-0.0115 for microsatellite and 0.0447-0.2391 for mtDNA), but the 4 southern sites showed little differentiation. Most of the intra-island genetic variation was allocated within rather than between sites. There was no evidence of sex-biased dispersal or population substructuring due to lek-mating behavior, suggesting that these 2 observed behaviors are not strong enough to leave an evolutionary signal on genetic patterns in this species.
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Stress physiology as a predictor of survival in Galapagos marine iguanas
Proceedings of The Royal Society B: Biological Sciences, 2010Co-Authors: L. Michael Romero, Martin WikelskiAbstract:Although glucocorticoid hormones are considered important physiological regulators for surviving adverse environmental stimuli (stressors), evidence for such a role is sparse and usually extrapolated from glucocorticoid effects under laboratory, short-term and/or non-emergency conditions. Galapagos marine iguanas (Amblyrhynchus cristatus) provide an excellent model for determining the ultimate func- tion of a glucocorticoid response because susceptibility to starvation induced by El Nino conditions is essentially their only major natural stressor. In a prospective study, we captured 98 adult male marine iguanas and assessed four major components of their glucocorticoid response: baseline corticosterone titres; corticosterone responses to acute stressors (capture and handling); the maximal capacity to secrete corticosterone (via adrenocorticotropin injection); and the ability to terminate corticosterone responses (negative feedback). Several months after collecting initial measurements, weak El Nino conditions affected the Galapagos and 23 iguanas died. The dead iguanas were typified by a reduced efficacy of nega- tive feedback (i.e. poorer post-stress suppression of corticosterone release) compared with surviving iguanas. We found no prior differences between dead and alive iguanas in baseline corticosterone concen- trations, responses to acute stressors, nor in capacity to respond. These data suggest that a greater ability to terminate a stress response conferred a survival advantage during starvation.
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Island tameness : an altered cardiovascular stress response in Galápagos marine iguanas
Physiology & Behavior, 2010Co-Authors: Maren N. Vitousek, L. Michael Romero, Elisa Tarlow, Nicole E. Cyr, Martin WikelskiAbstract:Island tameness is a widely documented phenomenon in which island species, particularly those that have evolved with no or few natural predators, show a greatly reduced behavioral response when faced with unfamiliar predators. This insufficient anti-predator response has led to widespread population declines among many island species exposed to novel predators, and has become a serious conservation problem. Despite its prevalence, the underlying physiology of island tameness is not known. Here we report that although Galapagos marine iguanas (Amblyrhynchus cristatus) initiated flight from an evolutionarily recent and unfamiliar potential predator (humans), they failed to show the cardiovascular stress response that facilitates successful escape, even after a prior capture experience. In contrast, when approached by a native predator (the Galapagos hawk; Buteo galapagoensis), marine iguanas show markedly increased heart rate independent of initiating escape movement. The secretion of catecholamines appears to be central to the initiation of escape behavior: naive animals remotely injected with epinephrine immediately increased flight initiation distance, whereas those injected with corticosterone did not. Our results provide the first evidence that muted escape behavior in predator-naive species is indicative of both a cognitive deficit in recognizing potential predators and a catecholamine deficit in response. Understanding how the response to predators differs in predator-naive species could enable the design of maximally effective techniques for inducing an anti-predator response in these vulnerable species.
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Are hotshots always hot? A longitudinal study of hormones, behavior, and reproductive success in male marine iguanas.
General and Comparative Endocrinology, 2008Co-Authors: Maren N. Vitousek, Dustin R. Rubenstein, Karin N. Nelson, Martin WikelskiAbstract:Polygynous lek-mating systems are characterized by high reproductive skew, with a small number of males gaining a disproportionate share of copulations. In lekking species, where female choice drives male mating success and patterns of reproductive skew, female preferences for ‘good genes’ should lead to preferred males having high reproductive success in all years. Here we investigate whether these ‘hotshot’ males have steroid hormone patterns that are consistent over time (between two mating seasons), and whether hormone levels consistently predict display behavior. We test these questions in the Galapagos marine iguana (Amblyrhynchus cristatus), a lekking vertebrate with high male reproductive skew. We found that male mating success and testosterone levels were not consistent across years. The most successful males showed an inverse relationship in copulation success between years. Similarly, territorial males that had high testosterone in one year had low levels in the next. Across years, testosterone was strongly associated with head-bob display, suggesting that this steroid plays a key role in mate attraction. These results suggest that female marine iguanas are not choosing the same ‘hotshot’ males in every year, but instead base their reproductive decisions on male behavioral traits that are hormonally mediated and variable across years. By using testosterone to regulate their costly display behaviors male marine iguanas appear to have a mechanism that allows them to adjust their reproductive effort depending on extrinsic and/or intrinsic factors.
Adalgisa Caccone - One of the best experts on this subject based on the ideXlab platform.
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ecological and evolutionary influences on body size and shape in the galapagos marine iguana Amblyrhynchus cristatus
Oecologia, 2016Co-Authors: Ylenia Chiari, Scott Glaberman, Adalgisa Caccone, Pedro Tarroso, Julien ClaudeAbstract:Oceanic islands are often inhabited by endemic species that have undergone substantial morphological evolutionary change due to processes of multiple colonizations from various source populations, dispersal, and local adaptation. Galapagos marine iguanas are an example of an island endemic exhibiting high morphological diversity, including substantial body size variation among populations and sexes, but the causes and magnitude of this variation are not well understood. We obtained morphological measurements from marine iguanas throughout their distribution range. These data were combined with genetic and local environmental data from each population to investigate the effects of evolutionary history and environmental conditions on body size and shape variation and sexual dimorphism. Our results indicate that body size and shape are highly variable among populations. Sea surface temperature and island perimeter, but not evolutionary history as depicted by phylogeographic patterns in this species, explain variation in body size among populations. Conversely, evolutionary history, but not environmental parameters or island size, was found to influence variation in body shape among populations. Finally, in all populations except one, we found strong sexual dimorphism in body size and shape in which males are larger, with higher heads than females, while females have longer heads than males. Differences among populations suggest that plasticity and/or genetic adaptation may shape body size and shape variation in marine iguanas. This study will help target future investigations to address the contribution of plasticity versus genetic adaptation on size and shape variation in marine iguanas.
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hybridization masks speciation in the evolutionary history of the galapagos marine iguana
Proceedings of The Royal Society B: Biological Sciences, 2015Co-Authors: Amy Macleod, Galo Quezada, Fritz Trillmich, Adalgisa Caccone, Gabriele Gentile, Miguel Vences, Ariel Rodriguez, Pablo Orozcoterwengel, Carolina Garcia, Sebastian SteinfartzAbstract:The effects of the direct interaction between hybridization and speciation—two major contrasting evolutionary processes—are poorly understood. We present here the evolutionary history of the Galapagos marine iguana (Amblyrhynchus cristatus) and reveal a case of incipient within-island speciation, which is paralleled by between-island hybridization. In-depth genome-wide analyses suggest that Amblyrhynchus diverged from its sister group, the Galapagos land iguanas, around 4.5 million years ago (Ma), but divergence among extant populations is exceedingly young (less than 50 000 years). Despite Amblyrhynchus appearing as a single long-branch species phylogenetically, we find strong population structure between islands, and one case of incipient speciation of sister lineages within the same island—ostensibly initiated by volcanic events. Hybridization between both lineages is exceedingly rare, yet frequent hybridization with migrants from nearby islands is evident. The contemporary snapshot provided by highly variable markers indicates that speciation events may have occurred throughout the evolutionary history of marine iguanas, though these events are not visible in the deeper phylogenetic trees. We hypothesize that the observed interplay of speciation and hybridization might be a mechanism by which local adaptations, generated by incipient speciation, can be absorbed into a common gene pool, thereby enhancing the evolutionary potential of the species as a whole.
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Genetic Differentiation between Marine Iguanas from Different Breeding Sites on the Island of Santa Fé (Galápagos Archipelago)
Journal of Heredity, 2010Co-Authors: Deborah Lanterbecq, Maren N. Vitousek, Scott Glaberman, Sebastian Steinfartz, Martin Wikelski, Edgar Benavides, Adalgisa CacconeAbstract:We studied patterns of genetic diversity within and among 5 populations (318 individuals) of Galapagos marine iguanas (Amblyrhynchus cristatus) from the island Santa Fe ´. Populations were separated by distances of 0.2 to 9.9 km. We sequenced 1182 base pairs of the mitochondrial control region and screened 13 microsatellite loci for variability. We also added data from 5 populations (397 individuals) sampled on 4 neighboring islands (Santa Cruz, Floreana, Espanola, and San Cristobal). The 5 Santa Fepopulations, revealed as genetically distinct from populations on other islands, present relatively low levels of genetic diversity, which are similar for both microsatellite (average observed heterozygosity from 0.7686 to 0.7773) and mitochondrial DNA (mtDNA) markers (haplotypic and nucleotide diversity from 0.587 to 0.728 and from 0.00079 to 0.00293, respectively), and comparable with those observed in similar-sized sampling sites on other islands. There was frequency-based evidence of genetic structure between northern and southern sites on Santa Fe ´( Fst of 0.0027-0.0115 for microsatellite and 0.0447-0.2391 for mtDNA), but the 4 southern sites showed little differentiation. Most of the intra-island genetic variation was allocated within rather than between sites. There was no evidence of sex-biased dispersal or population substructuring due to lek-mating behavior, suggesting that these 2 observed behaviors are not strong enough to leave an evolutionary signal on genetic patterns in this species.
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Characterization and evolution of MHC class II B genes in Galápagos marine iguanas (Amblyrhynchus cristatus).
Developmental and Comparative Immunology, 2009Co-Authors: Scott Glaberman, Maria A. Moreno, Adalgisa CacconeAbstract:Abstract Major histocompatibility complex (MHC) class II molecules play a key role in the adaptive immune system of vertebrates. Class II B genes appear to evolve in a very different manner in mammals and birds. Orthology is commonly observed among mammal loci, while genes tend to cluster phylogenetically within bird species. Here we present class II B data from a representative of another major group of amniotes, the squamates (i.e. lizards, snakes, amphisbaenians), with the ultimate goal of placing mammalian and avian MHC evolution into a broader context. In this study, eight class II B cDNA sequences were obtained from the Galapagos marine iguana ( Amblyrhynchus cristatus ) which were divided into five locus groups, Amcr - DAB1 through - DAB5 , based on similarities along most of the coding and noncoding portions of the transcribed gene. All marine iguana sequences were monophyletic with respect to class II genes from other vertebrates indicating that they originated from a common ancestral locus after squamates split from other reptiles. The β-1 domain, which is involved in antigen binding, exhibited signatures of positive selection as well as interlocus gene conversion in both long and short tracts—a pattern also observed in birds and fish, but not in mammals. On the other hand, the β-2 domain was divergent between gene groups, which is characteristic of mammals. Based on these results, we preliminarily show that squamate class II B genes have been shaped by a unique blend of evolutionary forces that have been observed in differing degrees in other vertebrates.
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characterization of a nonclassical class i mhc gene in a reptile the galapagos marine iguana Amblyrhynchus cristatus
PLOS ONE, 2008Co-Authors: Scott Glaberman, Louis Du Pasquier, Adalgisa CacconeAbstract:Squamates are a diverse order of vertebrates, representing more than 7,000 species. Yet, descriptions of full-length major histocompatibility complex (MHC) genes in this group are nearly absent from the literature, while the number of MHC studies continues to rise in other vertebrate taxa. The lack of basic information about MHC organization in squamates inhibits investigation into the relationship between MHC polymorphism and disease, and leaves a large taxonomic gap in our understanding of amniote MHC evolution. Here, we use both cDNA and genomic sequence data to characterize a class I MHC gene (Amcr-UA) from the Galapagos marine iguana, a member of the squamate subfamily Iguaninae. Amcr-UA appears to be functional since it is expressed in the blood and contains many of the conserved peptide-binding residues that are found in classical class I genes of other vertebrates. In addition, comparison of Amcr-UA to homologous sequences from other iguanine species shows that the antigen-binding portion of this gene is under purifying selection, rather than balancing selection, and therefore may have a conserved function. A striking feature of Amcr-UA is that both the cDNA and genomic sequences lack the transmembrane and cytoplasmic domains that are necessary to anchor the class I receptor molecule into the cell membrane, suggesting that the product of this gene is secreted and consequently not involved in classical class I antigen-presentation. The truncated and conserved character of Amcr-UA lead us to define it as a nonclassical gene that is related to the few available squamate class I sequences. However, phylogenetic analysis placed Amcr-UA in a basal position relative to other published classical MHC genes from squamates, suggesting that this gene diverged near the beginning of squamate diversification.
Sebastian Steinfartz - One of the best experts on this subject based on the ideXlab platform.
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Trophic niche differentiation mirrors intra-island population structure of Galápagos marine iguanas (Amblyrhynchus cristatus)
2019Co-Authors: Sten Anslan, Timm Reinhardt, Patrick Fink, Mario Brauns, Nicolás Peñafiel, Juan M. Guayasamin, Diego Páez-rosas, Miguel Vences, Sebastian SteinfartzAbstract:Abstract Background: Differences in the trophic niche often underlie ecological specialization of individuals and can promote ecological speciation of populations, but studies showing a link between differences in the trophic niche and genetic differentiation of populations are rare. On the island of San Cristóbal (Galapágos archipelago), a strong genetic differentiation between two relatively proximate populations (subspecies; Amblyrhynchus cristatus mertensi and A. c. godzilla) of marine iguanas along the coastline has been observed. Here, we explore whether this genetic differentiation is mirrored in the iguanas’ trophic niche. Results: Although, no significant difference in the number of consumed algal taxa between subspecies were detected, the Schoener index exhibited low diet overlap between A. c. mertensi and A. c. godzilla. The latter was also demonstrated by the PERMANOVA analysis with significantly different diet OTU composition from the fecal samples between subspecies. Stable isotope analysis revealed that subspecies identity was overall more important than site for the iguanas’ resource use. Conclusions: By applying a metabarcoding approach on feces samples in combination with stable isotope analysis of skin sheds, we found that A. c. mertensi and A. c. godzilla differ in their ecological niches. Moreover, stable isotope analysis indicated that marine iguana populations have low spatial foraging distances, which, together with the diet partitioning patterns, might explain, at least partially, the lack of gene flow between these geographically proximate marine iguana populations. Key words: diet analysis, trophic niche, metabarcoding, stable isotopes, marine iguanas, Amblyrhynchus cristatus
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Characterization of lipid structures in femoral secretions of Galápagos marine iguanas by shotgun lipidomics
Chemoecology, 2018Co-Authors: Alejandro Ibáñez, Galo Quezada, Susanne Brodesser, Corinna Klein, Marcus Kruger, Sebastian SteinfartzAbstract:The lipidome of femoral gland secretions of the marine iguana ( Amblyrhynchus cristatus ) was studied. The main aim of this work was to identify and quantify the lipids present in femoral secretions using mass spectrometry-based shotgun lipidomics. Lipids belonging to seven lipid classes were identified: ceramides (43.41%), triacylglycerols (42.15%), cholesteryl esters (4.18%), sphingomyelins (3.61%), phosphatidylcholines (2.67%), phosphatidylinositols (2.50%) and phosphatidylethanolamines (1.48%). The second aim of the study was to explore whether lipid composition matches the different subspecies or populations of marine iguanas. The different subspecies of iguanas did not group together in relation to their lipidome. The authors’ findings are discussed in an ecological context and compared with the results of a previous study that characterized volatile lipids in marine iguana secretions using gas chromatography. Given the high diversity of lipid structures in femoral secretions discovered in this study, it is likely that some of these could be involved in intraspecific communication. Certain lipids could have other functions, such as building a barrier to avoid water loss. More data needs to be added to explore this hypothesis. This study is the first to use a lipidomics-based approach to characterize lipid composition in lizard femoral secretions. The application of shotgun lipidomics to reptilian glandular secretions will shed new light on the potential function of lipids in intraspecific chemical communication.
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Diversity of compounds in femoral secretions of Galápagos iguanas (genera: Amblyrhynchus and Conolophus), and their potential role in sexual communication in lek-mating marine iguanas (Amblyrhynchus cristatus).
PeerJ, 2017Co-Authors: Alejandro Ibáñez, Galo Quezada, Markus Menke, Gustavo Jiménez-uzcátegui, Stefan Schulz, Sebastian SteinfartzAbstract:Background Chemical signals are widely used in the animal kingdom, enabling communication in various social contexts, including mate selection and the establishment of dominance. Femoral glands, which produce and release waxy secretions into the environment, are organs of central importance in lizard chemical communication. The Galapagos marine iguana (Amblyrhynchus cristatus) is a squamate reptile with a lek-mating system. Although the lekking behaviour of marine iguanas has been well-studied, their potential for sexual communication via chemical cues has not yet been investigated. Here we describe the diversity of the lipophilic fraction of males’ femoral gland secretions among 11 island populations of marine iguanas, and compare it with the composition of its sister species, the Galapagos land iguana (Conolophus subcristatus). We also conducted behavioural observations in marine iguana territorial males in order to explore the possible function of these substances in the context of male dominance in leks. Methods Femoral secretions were analysed by gas chromatography coupled to mass spectrometry (GC–MS), and chromatography with a flame ionisation detector (GC-FID) in order to characterise the lipophilic composition. To understand the potential role of femoral secretions in marine iguana intraspecific communication, territorial males were sampled for their femoral glands and monitored to record their head bob rate—a territorial display behaviour in males—as well as the number of females present in their leks. Results We found that the gland secretions were composed of ten saturated and unsaturated carboxylic acids ranging in chain length between C16 and C24, as well as three sterols. Cholesterol was the main compound found. Intriguingly, land iguanas have a higher diversity of lipophilic compounds, with structural group of lipids (i.e. aldehydes) entirely absent in marine iguanas; overall the chemical signals of both species were strongly differentiated. Lipid profiles also differed among populations of marine iguanas from different islands, with some islands demonstrating a high diversity of lipophilic compounds (i.e. full spectra of compounds), and others lacking one or more compounds. Among the compounds most frequently found missing were 11- and 13-eicosenoic acids. Gland secretions of males with a better body condition and with a higher dominance status (i.e. those accompanied by females and with higher head bob display) were proportionately richer in C20-unsaturated fatty acids (11-eicosenoic acid). Discussion Land and marine iguanas strongly diverged in their chemical composition of the femoral glands likely due to ecological differences between both species. Despite that marine iguana populations varied in their femoral gland composition that was not related to their genetic structure. Our results indicated that 11-eicosenoic acid may play an important role in intraspecific chemical communication in marine iguanas.
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The conservation status of the Galápagos marine iguanas, Amblyrhynchus cristatus : a molecular perspective
Amphibia-reptilia, 2016Co-Authors: Amy Macleod, Sebastian SteinfartzAbstract:Traditionally, conservation management focuses efforts on taxonomic units. However, when the taxa used do not reflect biologically meaningful units, such methods should be reconsidered to avoid the loss of irreplaceable biodiversity. The Galapagos marine iguana ( Amblyrhynchus cristatus ) is listed as Vulnerable on the IUCN Red List of Threatened Species and is facing growing anthropogenic threats. Currently, management is based on a taxonomy which is questionable in the light of recent molecular data. As such, there is a danger that evolutionarily significant populations may be left vulnerable to extirpation. Herein, we apply molecular data to elucidate the population structure of this species across the Galapagos archipelago, and thus advise conservation management in the absence of a revised taxonomy. Applying a wealth of molecular data including 12 microsatellite loci and 1181 bp of the mitochondrial control region in over 1200 individuals, we delineate distinct populations and prioritize their management. Bayesian population structure analysis revealed 10 distinct population clusters, which we propose as management units (MUs). All MUs are significantly differentiated, with one unit on San Cristobal Island being particularly distinct in terms of both microsatellite loci and mitochondrial data. Based on estimates of the genetic effective population size (N e ), we find the MUs comprised of populations occurring on Floreana, Espanola, Marchena, and San Cristobal to be alarmingly small. In consideration of both N e and anthropogenic threats, we recommend that conservation practitioners focus efforts on Floreana and San Cristobal islands, and argue that better census size estimates of populations are urgently needed.
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The complete mitochondrial genomes of the Galápagos iguanas, Amblyrhynchus cristatus and Conolophus subcristatus.
Mitochondrial DNA, 2015Co-Authors: Amy Macleod, Miguel Vences, Iker Irisarri, Sebastian SteinfartzAbstract:AbstractThe Galapagos iguanas are among the oldest vertebrate lineages on the Galapagos archipelago, and the evolutionary history of this clade is of great interest to biologists. We describe here the complete mitochondrial genomes of the marine iguana, Amblyrhynchus cristatus (Genbank accession number: KT277937) and the land iguana Conolophus subcristatus (Genbank accession number: KT277936). The genomes contain 13 protein-coding genes, 22 transfer RNAs, and two ribosomal RNAs genes, as well as a control region (CR). Both species have an identical gene order, which matches that of Iguana iguana. The CR of both Galapagos iguanas features similar tandem repeats units, which are absent in I. iguana. We present a phylogeny of the Iguanidae based on complete mitochondrial genomes, which confirms the sister-group relationship of Galapagos iguanas. These new mitochondrial genomes constitute an important data source for future exploration of the phylogenetic relationships and evolutionary history of the Galapago...
Maren N. Vitousek - One of the best experts on this subject based on the ideXlab platform.
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Genetic Differentiation between Marine Iguanas from Different Breeding Sites on the Island of Santa Fé (Galápagos Archipelago)
Journal of Heredity, 2010Co-Authors: Deborah Lanterbecq, Maren N. Vitousek, Scott Glaberman, Sebastian Steinfartz, Martin Wikelski, Edgar Benavides, Adalgisa CacconeAbstract:We studied patterns of genetic diversity within and among 5 populations (318 individuals) of Galapagos marine iguanas (Amblyrhynchus cristatus) from the island Santa Fe ´. Populations were separated by distances of 0.2 to 9.9 km. We sequenced 1182 base pairs of the mitochondrial control region and screened 13 microsatellite loci for variability. We also added data from 5 populations (397 individuals) sampled on 4 neighboring islands (Santa Cruz, Floreana, Espanola, and San Cristobal). The 5 Santa Fepopulations, revealed as genetically distinct from populations on other islands, present relatively low levels of genetic diversity, which are similar for both microsatellite (average observed heterozygosity from 0.7686 to 0.7773) and mitochondrial DNA (mtDNA) markers (haplotypic and nucleotide diversity from 0.587 to 0.728 and from 0.00079 to 0.00293, respectively), and comparable with those observed in similar-sized sampling sites on other islands. There was frequency-based evidence of genetic structure between northern and southern sites on Santa Fe ´( Fst of 0.0027-0.0115 for microsatellite and 0.0447-0.2391 for mtDNA), but the 4 southern sites showed little differentiation. Most of the intra-island genetic variation was allocated within rather than between sites. There was no evidence of sex-biased dispersal or population substructuring due to lek-mating behavior, suggesting that these 2 observed behaviors are not strong enough to leave an evolutionary signal on genetic patterns in this species.
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Island tameness : an altered cardiovascular stress response in Galápagos marine iguanas
Physiology & Behavior, 2010Co-Authors: Maren N. Vitousek, L. Michael Romero, Elisa Tarlow, Nicole E. Cyr, Martin WikelskiAbstract:Island tameness is a widely documented phenomenon in which island species, particularly those that have evolved with no or few natural predators, show a greatly reduced behavioral response when faced with unfamiliar predators. This insufficient anti-predator response has led to widespread population declines among many island species exposed to novel predators, and has become a serious conservation problem. Despite its prevalence, the underlying physiology of island tameness is not known. Here we report that although Galapagos marine iguanas (Amblyrhynchus cristatus) initiated flight from an evolutionarily recent and unfamiliar potential predator (humans), they failed to show the cardiovascular stress response that facilitates successful escape, even after a prior capture experience. In contrast, when approached by a native predator (the Galapagos hawk; Buteo galapagoensis), marine iguanas show markedly increased heart rate independent of initiating escape movement. The secretion of catecholamines appears to be central to the initiation of escape behavior: naive animals remotely injected with epinephrine immediately increased flight initiation distance, whereas those injected with corticosterone did not. Our results provide the first evidence that muted escape behavior in predator-naive species is indicative of both a cognitive deficit in recognizing potential predators and a catecholamine deficit in response. Understanding how the response to predators differs in predator-naive species could enable the design of maximally effective techniques for inducing an anti-predator response in these vulnerable species.
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Investment in mate choice depends on resource availability in female Galápagos marine iguanas (Amblyrhynchus cristatus)
Behavioral Ecology and Sociobiology, 2009Co-Authors: Maren N. VitousekAbstract:Changes in mate selectivity can significantly alter the direction and strength of sexual selection. When the direct cost of mate search increases selectivity often declines; however, little is known about how the relative cost of mate search affects investment in mate choice. Here, I investigate whether male and female Galápagos marine iguanas ( Amblyrhynchus cristatus ) alter their investment in mate choice behaviors when resources are limited and the relative cost of mate search is increased. Moderate resource limitation had little effect on male reproductive behavior: in both years, a similar number of males were territorial, and the mean display rate and copulation success of territorial males did not differ. In contrast, female mate search appeared to be affected by the prevailing environmental conditions. During the reproductive season following a moderate El Niño event, when food availability declined, females were in poorer body condition, assessed fewer territorial males, and mated with a male with lower relative reproductive success. Circulating hormone levels also differed between years: when resource availability was limited, receptive females had higher levels of testosterone and stress-induced corticosterone. The frequency and magnitude of climatic fluctuations are expected to increase in the future across many regions of the globe. Determining how sexual selection is shaped by changes in resource availability is vital for predicting the impact of climate change.
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Investment in mate choice depends on resource availability in female Galápagos marine iguanas (Amblyrhynchus cristatus)
Behavioral Ecology and Sociobiology, 2009Co-Authors: Maren N. VitousekAbstract:Changes in mate selectivity can significantly alter the direction and strength of sexual selection. When the direct cost of mate search increases selectivity often declines; however, little is known about how the relative cost of mate search affects investment in mate choice. Here, I investigate whether male and female Galápagos marine iguanas ( Amblyrhynchus cristatus ) alter their investment in mate choice behaviors when resources are limited and the relative cost of mate search is increased. Moderate resource limitation had little effect on male reproductive behavior: in both years, a similar number of males were territorial, and the mean display rate and copulation success of territorial males did not differ. In contrast, female mate search appeared to be affected by the prevailing environmental conditions. During the reproductive season following a moderate El Niño event, when food availability declined, females were in poorer body condition, assessed fewer territorial males, and mated with a male with lower relative reproductive success. Circulating hormone levels also differed between years: when resource availability was limited, receptive females had higher levels of testosterone and stress-induced corticosterone. The frequency and magnitude of climatic fluctuations are expected to increase in the future across many regions of the globe. Determining how sexual selection is shaped by changes in resource availability is vital for predicting the impact of climate change.
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ORIGINAL PAPER Investment in mate choice depends on resource availability in female Galápagos marine iguanas (Amblyrhynchus cristatus)
2009Co-Authors: Maren N. VitousekAbstract:Abstract Changes in mate selectivity can significantly alter the direction and strength of sexual selection. When the direct cost of mate search increases selectivity often declines; however, little is known about how the relative cost of mate search affects investment in mate choice. Here, I investigate whether male and female Galápagos marine iguanas (Amblyrhynchus cristatus) alter their investment in mate choice behaviors when resources are limited and the relative cost of mate search is increased. Moderate resource limitation had little effect on male reproductive behavior: in both years, a similar number of males were territorial, and the mean display rate and copulation success of territorial males did not differ. In contrast, female mate search appeared to be affected by the prevailing environmental conditions. During the reproductive season following a moderate El Niño event, when food availability declined, females were in poorer body condition, assessed fewer territorial males, and mated with a male with lower relative reproductive success. Circulating hormone levels also differed between years: when resource availability was limited, receptive females had higher levels of testosterone and stress-induced cortico-sterone. The frequency and magnitude of climatic fluctua-tions are expected to increase in the future across many regions of the globe. Determining how sexual selection is shaped by changes in resource availability is vital for predicting the impact of climate change
Scott Glaberman - One of the best experts on this subject based on the ideXlab platform.
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ecological and evolutionary influences on body size and shape in the galapagos marine iguana Amblyrhynchus cristatus
Oecologia, 2016Co-Authors: Ylenia Chiari, Scott Glaberman, Adalgisa Caccone, Pedro Tarroso, Julien ClaudeAbstract:Oceanic islands are often inhabited by endemic species that have undergone substantial morphological evolutionary change due to processes of multiple colonizations from various source populations, dispersal, and local adaptation. Galapagos marine iguanas are an example of an island endemic exhibiting high morphological diversity, including substantial body size variation among populations and sexes, but the causes and magnitude of this variation are not well understood. We obtained morphological measurements from marine iguanas throughout their distribution range. These data were combined with genetic and local environmental data from each population to investigate the effects of evolutionary history and environmental conditions on body size and shape variation and sexual dimorphism. Our results indicate that body size and shape are highly variable among populations. Sea surface temperature and island perimeter, but not evolutionary history as depicted by phylogeographic patterns in this species, explain variation in body size among populations. Conversely, evolutionary history, but not environmental parameters or island size, was found to influence variation in body shape among populations. Finally, in all populations except one, we found strong sexual dimorphism in body size and shape in which males are larger, with higher heads than females, while females have longer heads than males. Differences among populations suggest that plasticity and/or genetic adaptation may shape body size and shape variation in marine iguanas. This study will help target future investigations to address the contribution of plasticity versus genetic adaptation on size and shape variation in marine iguanas.
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Genetic Differentiation between Marine Iguanas from Different Breeding Sites on the Island of Santa Fé (Galápagos Archipelago)
Journal of Heredity, 2010Co-Authors: Deborah Lanterbecq, Maren N. Vitousek, Scott Glaberman, Sebastian Steinfartz, Martin Wikelski, Edgar Benavides, Adalgisa CacconeAbstract:We studied patterns of genetic diversity within and among 5 populations (318 individuals) of Galapagos marine iguanas (Amblyrhynchus cristatus) from the island Santa Fe ´. Populations were separated by distances of 0.2 to 9.9 km. We sequenced 1182 base pairs of the mitochondrial control region and screened 13 microsatellite loci for variability. We also added data from 5 populations (397 individuals) sampled on 4 neighboring islands (Santa Cruz, Floreana, Espanola, and San Cristobal). The 5 Santa Fepopulations, revealed as genetically distinct from populations on other islands, present relatively low levels of genetic diversity, which are similar for both microsatellite (average observed heterozygosity from 0.7686 to 0.7773) and mitochondrial DNA (mtDNA) markers (haplotypic and nucleotide diversity from 0.587 to 0.728 and from 0.00079 to 0.00293, respectively), and comparable with those observed in similar-sized sampling sites on other islands. There was frequency-based evidence of genetic structure between northern and southern sites on Santa Fe ´( Fst of 0.0027-0.0115 for microsatellite and 0.0447-0.2391 for mtDNA), but the 4 southern sites showed little differentiation. Most of the intra-island genetic variation was allocated within rather than between sites. There was no evidence of sex-biased dispersal or population substructuring due to lek-mating behavior, suggesting that these 2 observed behaviors are not strong enough to leave an evolutionary signal on genetic patterns in this species.
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Progressive colonization and restricted gene flow shape island-dependent population structure in Galápagos marine iguanas (Amblyrhynchus cristatus)
BMC Evolutionary Biology, 2009Co-Authors: Sebastian Steinfartz, Scott Glaberman, Deborah Lanterbecq, Michael A. Russello, Sabrina Rosa, Torrance C. Hanley, Cruz Marquez, Howard L. Snell, Heidi M. Snell, Gabriele GentileAbstract:Background Marine iguanas (Amblyrhynchus cristatus) inhabit the coastlines of large and small islands throughout the Galapagos archipelago, providing a rich system to study the spatial and temporal factors influencing the phylogeographic distribution and population structure of a species. Here, we analyze the microevolution of marine iguanas using the complete mitochondrial control region (CR) as well as 13 microsatellite loci representing more than 1200 individuals from 13 islands.
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Characterization and evolution of MHC class II B genes in Galápagos marine iguanas (Amblyrhynchus cristatus).
Developmental and Comparative Immunology, 2009Co-Authors: Scott Glaberman, Maria A. Moreno, Adalgisa CacconeAbstract:Abstract Major histocompatibility complex (MHC) class II molecules play a key role in the adaptive immune system of vertebrates. Class II B genes appear to evolve in a very different manner in mammals and birds. Orthology is commonly observed among mammal loci, while genes tend to cluster phylogenetically within bird species. Here we present class II B data from a representative of another major group of amniotes, the squamates (i.e. lizards, snakes, amphisbaenians), with the ultimate goal of placing mammalian and avian MHC evolution into a broader context. In this study, eight class II B cDNA sequences were obtained from the Galapagos marine iguana ( Amblyrhynchus cristatus ) which were divided into five locus groups, Amcr - DAB1 through - DAB5 , based on similarities along most of the coding and noncoding portions of the transcribed gene. All marine iguana sequences were monophyletic with respect to class II genes from other vertebrates indicating that they originated from a common ancestral locus after squamates split from other reptiles. The β-1 domain, which is involved in antigen binding, exhibited signatures of positive selection as well as interlocus gene conversion in both long and short tracts—a pattern also observed in birds and fish, but not in mammals. On the other hand, the β-2 domain was divergent between gene groups, which is characteristic of mammals. Based on these results, we preliminarily show that squamate class II B genes have been shaped by a unique blend of evolutionary forces that have been observed in differing degrees in other vertebrates.
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characterization of a nonclassical class i mhc gene in a reptile the galapagos marine iguana Amblyrhynchus cristatus
PLOS ONE, 2008Co-Authors: Scott Glaberman, Louis Du Pasquier, Adalgisa CacconeAbstract:Squamates are a diverse order of vertebrates, representing more than 7,000 species. Yet, descriptions of full-length major histocompatibility complex (MHC) genes in this group are nearly absent from the literature, while the number of MHC studies continues to rise in other vertebrate taxa. The lack of basic information about MHC organization in squamates inhibits investigation into the relationship between MHC polymorphism and disease, and leaves a large taxonomic gap in our understanding of amniote MHC evolution. Here, we use both cDNA and genomic sequence data to characterize a class I MHC gene (Amcr-UA) from the Galapagos marine iguana, a member of the squamate subfamily Iguaninae. Amcr-UA appears to be functional since it is expressed in the blood and contains many of the conserved peptide-binding residues that are found in classical class I genes of other vertebrates. In addition, comparison of Amcr-UA to homologous sequences from other iguanine species shows that the antigen-binding portion of this gene is under purifying selection, rather than balancing selection, and therefore may have a conserved function. A striking feature of Amcr-UA is that both the cDNA and genomic sequences lack the transmembrane and cytoplasmic domains that are necessary to anchor the class I receptor molecule into the cell membrane, suggesting that the product of this gene is secreted and consequently not involved in classical class I antigen-presentation. The truncated and conserved character of Amcr-UA lead us to define it as a nonclassical gene that is related to the few available squamate class I sequences. However, phylogenetic analysis placed Amcr-UA in a basal position relative to other published classical MHC genes from squamates, suggesting that this gene diverged near the beginning of squamate diversification.