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Martin Wikelski – One of the best experts on this subject based on the ideXlab platform.

  • 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, 2014
    Co-Authors: Roderick I. Mackie, Mathew Rycyk, Rebecca L. Ruemmler, Rustam Aminov, Martin Wikelski

    Abstract:

    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, 2010
    Co-Authors: Deborah Lanterbecq, Maren N. Vitousek, Sebastian Steinfartz, Scott Glaberman, Martin Wikelski, Edgar Benavides, Adalgisa Caccone

    Abstract:

    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, 2010
    Co-Authors: L. Michael Romero, Martin Wikelski

    Abstract:

    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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Adalgisa Caccone – One of the best experts on this subject based on the ideXlab platform.

  • ecological and evolutionary influences on body size and shape in the galapagos marine iguana Amblyrhynchus cristatus
    Oecologia, 2016
    Co-Authors: Ylenia Chiari, Scott Glaberman, Adalgisa Caccone, Pedro Tarroso, Julien Claude

    Abstract:

    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, 2015
    Co-Authors: Amy Macleod, Galo Quezada, Adalgisa Caccone, Gabriele Gentile, Miguel Vences, Fritz Trillmich, Ariel Rodriguez, Pablo Orozcoterwengel, Carolina Garcia, Sebastian Steinfartz

    Abstract:

    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, 2010
    Co-Authors: Deborah Lanterbecq, Maren N. Vitousek, Sebastian Steinfartz, Scott Glaberman, Martin Wikelski, Edgar Benavides, Adalgisa Caccone

    Abstract:

    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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Sebastian Steinfartz – One of the best experts on this subject based on the ideXlab platform.

  • Trophic niche differentiation mirrors intra-island population structure of Galápagos marine iguanas (Amblyrhynchus cristatus)
    , 2019
    Co-Authors: Sten Anslan, Timm Reinhardt, Patrick Fink, Mario Brauns, Nicolás Peñafiel, Juan M. Guayasamin, Diego Páez-rosas, Miguel Vences, Sebastian Steinfartz

    Abstract:

    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, 2018
    Co-Authors: Alejandro Ibáñez, Corinna Klein, Galo Quezada, Marcus Kruger, Susanne Brodesser, Sebastian Steinfartz

    Abstract:

    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, 2017
    Co-Authors: Alejandro Ibáñez, Galo Quezada, Markus Menke, Gustavo Jiménez-uzcátegui, Stefan Schulz, Sebastian Steinfartz

    Abstract:

    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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