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Fritz Trillmich - One of the best experts on this subject based on the ideXlab platform.
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The spatial ecology of invasive feral cats Felis catus on San Cristóbal, Galápagos: first insights from GPS collars
Mammal Research, 2020Co-Authors: A. Macleod, S. C. Cooke, Fritz TrillmichAbstract:The dangers posed by invasive species for endemic island wildlife are well recognised. Introduced domestic cats ( Felis catus ) represent a significant threat to several endemic species of the Galápagos archipelago—including hatchling Marine Iguanas ( Amblyrhynchus cristatus ) and potentially green turtles ( Chelonia mydas )—yet little is known about their spatial ecology and habitat use on these islands. Here, we describe a pilot study using GPS collars to track the movements of three feral cats at a site of conservation interest on San Cristóbal Island. Based on 175 days of GPS data, we undertook spatial analyses to ascertain home ranges, and to investigate the overlap of ranges between the cats and potential prey species. Average home range was 1.27 km^2 (1.12–1.46 km^2), which—though small for feral cats—is in keeping with previous findings in Galápagos. We found the cats did use the habitat of a small Marine Iguana population but did not change their spatial habits before and after Iguana hatchlings appeared. Changes over time in the daily movements of one cat indicated a possible response of the individual to the presence of hatchling green turtles ( Chelonia mydas ); though the data here are insufficient to show whether the cat was hunting these hatchlings. We recommend similar work be undertaken in areas with larger Marine Iguana populations, where hatchlings could represent a potentially important food source for invasive feral cats, as well as further work to determine the threat posed by cats to turtle hatchlings in Galápagos.
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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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New highly polymorphic microsatellite loci for the Galápagos Marine Iguana, Amblyrhynchus cristatus
Amphibia-reptilia, 2012Co-Authors: Amy Macleod, Fritz Trillmich, Volker Koch, Carolina García-parra, Sebastian SteinfartzAbstract:We describe the development and characterisation of six new dinucleotide motif microsatellite loci for populations of Marine Iguanas (Amblyrhynchus cristatus), endemic to the Galapagos archipelago. Primers were based on microsatellite-bearing sequences and initially developed using universally labelled primers. When analysed across 5 populations (representing 150 individuals), new loci displayed, on average, high levels of genetic diversity (range: 2-13 alleles, mean: 5.73) and values of heterozygosity (range: 0.0-0.906, mean: 0.605). No consistent deviations from Hardy-Weinberg equilibrium or significant linkage disequilibrium were observed, and all loci were shown to be free of common microsatellite errors. Utilising the 13 previously available microsatellite loci for this species, we describe here four multiplex combinations for the successful amplification of 19 microsatellite loci for Marine Iguanas. This powerful set of highly polymorphic markers will allow researchers to explore future questions regarding the ecology, evolution, and conservation of this unique species.
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energy limits to body size in a grazing reptile the galapagos Marine Iguana
Ecology, 1997Co-Authors: Martin Wikelski, Victor Carrillo, Fritz TrillmichAbstract:Galapagos Marine Iguana (Amblyrhynchus cristatus) populations show con- siderable differences in body size. Adult body mass varies by more than 10-fold, and body length (snout-vent length, SVL) varies by -2.2-fold. Predation and interspecific food com- petition are largely absent and can be excluded as potential forces explaining differences in body size among populations. This provides an ideal system in which to determine how proximate environmental factors affect adult body size. We compared the small Iguanas from Genovesa Island (mean adult male SVL 250 mm) to the larger Santa Fe Iguanas (mean adult male SVL 400 mm). Marine Iguanas forage on intertidal algae pastures in scramble competition. Energy availability was lower on Genovesa than on Santa Fe, because of lower Marine productivity on Genovesa. The length of grazable algal turf decreased with increas- ing sea surface temperature (SST). SST was -20C lower on Santa Fe than on Genovesa, implying 1.5 mm lower algae pastures on the latter. Genovesa showed a fivefold lower standing algal biomass and a twofold lower productivity of algae pastures than did Santa Fe. The smallest Iguanas of each island had 1.5-fold higher bite rates during foraging, and their absolute food intake per day was 35% that of the largest Iguanas. However, food intake per bite per gram of body mass was about twice as high for small Iguanas as for large Iguanas. Large Iguanas of both islands showed a marked decline in body mass during the two study years, whereas small Iguanas (SVL 200 mm SVL on Genovesa and >310 mm SVL on Santa Fe significantly lost mass; in the more productive year (1992/1993), thresholds were 230 mm and 350 mm SVL, respectively. Thus, food abundance (length and turnover of algal swards) explained differences in adult body length and mass between islands as a result of energetic limitation. On a given island, foraging efficiency (intake/bite) explained the negative energy balance of large compared to small Iguanas. This also explained why, on both islands, the largest animals suffered higher mortality rates than did medium-sized ones when food was scarce. The finding that small animals outcompeted larger ones because of their higher foraging efficiency resembles the grazing succession in ungulate herbivores.
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Hybridization between the Galapagos land and Marine Iguana (Conolophus subcristatus and Amblyrhynchus cristatus) on Plaza Sur
Journal of Zoology, 1997Co-Authors: K Rassmann, Fritz Trillmich, Diethard TautzAbstract:Hybridization plays an important role in the evolution of some of the vertebrate taxa on the Galapagos Islands, such as the Darwin finches. Conversely, only a single possible hybrid between the Galapagos Marine Iguana (Amblyrhynchus) and the land Iguana (Conolophus) has been reported from the island Plaza Sur. In this paper, the hybrid status of a morphologically unusual Iguana from this island is confirmed, using restriction fragment length polymorphism (RFLP) analyses of the nuclear ribosomal DNA (rDNA). Sequencing of the hybrid's mitochondrial cytochrome b gene revealed that it was the offspring of a female land Iguana and a male Marine Iguana. Preliminary molecular analyses of morphologically typical Marine and land Iguanas from Plaza Sur did not detect introgression of nuclear or mitochondrial markers between species. The potential significance of hybridization for the evolution of the Plaza Sur Iguana populations is discussed.
Sebastian Steinfartz - One of the best experts on this subject based on the ideXlab platform.
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no impact of a short term climatic el nino fluctuation on gut microbial diversity in populations of the galapagos Marine Iguana amblyrhynchus cristatus
Naturwissenschaften, 2021Co-Authors: Alejandro Ibanez, Galo Quezada, Sebastian Steinfartz, Miguel Vences, Molly C Bletz, Robert Geffers, Michael JarekAbstract:Gut microorganisms are crucial for many biological functions playing a pivotal role in the host’s well-being. We studied gut bacterial community structure of Marine Iguana populations across the Galapagos archipelago. Marine Iguanas depend heavily on their specialized gut microbiome for the digestion of dietary algae, a resource whose growth was strongly reduced by severe “El Nino”-related climatic fluctuations in 2015/2016. As a consequence, Marine Iguana populations showed signs of starvation as expressed by a poor body condition. Body condition indices (BCI) varied between island populations indicating that food resources (i.e., algae) are affected differently across the archipelago during ‘El Nino’ events. Though this event impacted food availability for Marine Iguanas, we found that reductions in body condition due to “El Nino”-related starvation did not result in differences in bacterial gut community structure. Species richness of gut microorganisms was instead correlated with levels of neutral genetic diversity in the distinct host populations. Our data suggest that Marine Iguana populations with a higher level of gene diversity and allelic richness may harbor a more diverse gut microbiome than those populations with lower genetic diversity. Since low values of these diversity parameters usually correlate with small census and effective population sizes, we use our results to propose a novel hypothesis according to which small and genetically less diverse host populations might be characterized by less diverse microbiomes. Whether such genetically depauperate populations may experience additional threats from reduced dietary flexibility due to a limited intestinal microbiome is currently unclear and calls for further investigation.
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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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New highly polymorphic microsatellite loci for the Galápagos Marine Iguana, Amblyrhynchus cristatus
Amphibia-reptilia, 2012Co-Authors: Amy Macleod, Fritz Trillmich, Volker Koch, Carolina García-parra, Sebastian SteinfartzAbstract:We describe the development and characterisation of six new dinucleotide motif microsatellite loci for populations of Marine Iguanas (Amblyrhynchus cristatus), endemic to the Galapagos archipelago. Primers were based on microsatellite-bearing sequences and initially developed using universally labelled primers. When analysed across 5 populations (representing 150 individuals), new loci displayed, on average, high levels of genetic diversity (range: 2-13 alleles, mean: 5.73) and values of heterozygosity (range: 0.0-0.906, mean: 0.605). No consistent deviations from Hardy-Weinberg equilibrium or significant linkage disequilibrium were observed, and all loci were shown to be free of common microsatellite errors. Utilising the 13 previously available microsatellite loci for this species, we describe here four multiplex combinations for the successful amplification of 19 microsatellite loci for Marine Iguanas. This powerful set of highly polymorphic markers will allow researchers to explore future questions regarding the ecology, evolution, and conservation of this unique species.
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A set of highly discriminating microsatellite loci for the Galápagos Marine Iguana Amblyrhynchus cristatus
Molecular Ecology Notes, 2006Co-Authors: Sebastian Steinfartz, Adalgisa CacconeAbstract:We describe here the cloning of 12 (7 dinucleotide, 1 trinucleotide and 4 tetranucleotide) microsatellite loci for the Galapagos Marine Iguana Amblyrhynchus cristatus . When tested for individuals from five different island populations on the Galapagos archipelago, high genetic diversities (9–20 alleles per locus) and heterozygosities (0.200–0.944) were observed. All loci showed no obvious deviations from Hardy–Weinberg equilibrium. The new set of microsatellite loci was able to assign individuals reliably to their island of origin, thus being able to discriminate between residents and migrants between islands.
Martin Wikelski - One of the best experts on this subject based on the ideXlab platform.
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behavioral and physiological adjustments to new predators in an endemic island species the galapagos Marine Iguana
Hormones and Behavior, 2007Co-Authors: Silke Berger, Martin Wikelski, Elisabeth K. V. Kalko, Michael L Romero, Thomas RödlAbstract:For the past 5 to 15 million years, Marine Iguanas (Amblyrhynchus cristatus), endemic to the Galapagos archipelago, experienced relaxed predation pressure and consequently show negligible anti-predator behavior. However, over the past few decades introduced feral cats and dogs started to prey on Iguanas on some of the islands. We investigated experimentally whether behavioral and endocrine anti-predator responses changed in response to predator introduction. We hypothesized that flight initiation distances (FID) and corticosterone (CORT) concentrations should increase in affected populations to cope with the novel predators. Populations of Marine Iguanas reacted differentially to simulated predator approach depending on whether or not they were previously naturally exposed to introduced predators. FIDs were larger at sites with predation than at sites without predation. Furthermore, the occurrence of new predators was associated with increased stress-induced CORT levels in Marine Iguanas. In addition, age was a strong predictor of variation in FID and CORT levels. Juveniles, which are generally more threatened by predators compared to adults, showed larger FIDs and higher CORT baseline levels as well as higher stress-induced levels than adults. The results demonstrate that this naive island species shows behavioral and physiological plasticity associated with actual predation pressure, a trait that is presumably adaptive. However, the adjustments in FID are not sufficient to cope with the novel predators. We suggest that low behavioral plasticity in the face of introduced predators may drive many island species to extinction.
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Effects of foraging mode and season on the energetics of the Marine Iguana, Amblyrhynchus cristatus
Functional Ecology, 1999Co-Authors: J. Drent, W.d. Van Marken Lichtenbelt, Martin WikelskiAbstract:1, Marine Iguanas (Amblyrhynchus cristatus) inhabiting the rocky shores of the Galapagos Islands apply two foraging strategies, intertidal and subtidal foraging, in a seasonal climate. Effects of both foraging strategy and seasonality on the daily energy expenditure (DEE) were measured using doubly labelled water. 2, Difference in foraging mode did not result in significant differences in DEE. 3, On Santa FC the DEE in the warm season was significantly higher than in the cool season (57.8 +/- 21.8 kJ kg(-0.8) day(-1) vs 38.0 kJ kg(-0.8) day(-1)). This difference can be explained by body temperature. A model estimate of the body temperature was used to predict monthly DEE figures, giving a year round budget. On average a l-kg Iguana would need only 47 kJ day(-1), or 17 mJ year(-1). This is lower than previous estimates in which body temperatures were not taken into account. 4, The water flux of the Marine Iguana increases with increasing foraging time. The linear rise per minute foraging is roughly two times as high for subtidally foraging animals as for intertidal foragers.
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energy limits to body size in a grazing reptile the galapagos Marine Iguana
Ecology, 1997Co-Authors: Martin Wikelski, Victor Carrillo, Fritz TrillmichAbstract:Galapagos Marine Iguana (Amblyrhynchus cristatus) populations show con- siderable differences in body size. Adult body mass varies by more than 10-fold, and body length (snout-vent length, SVL) varies by -2.2-fold. Predation and interspecific food com- petition are largely absent and can be excluded as potential forces explaining differences in body size among populations. This provides an ideal system in which to determine how proximate environmental factors affect adult body size. We compared the small Iguanas from Genovesa Island (mean adult male SVL 250 mm) to the larger Santa Fe Iguanas (mean adult male SVL 400 mm). Marine Iguanas forage on intertidal algae pastures in scramble competition. Energy availability was lower on Genovesa than on Santa Fe, because of lower Marine productivity on Genovesa. The length of grazable algal turf decreased with increas- ing sea surface temperature (SST). SST was -20C lower on Santa Fe than on Genovesa, implying 1.5 mm lower algae pastures on the latter. Genovesa showed a fivefold lower standing algal biomass and a twofold lower productivity of algae pastures than did Santa Fe. The smallest Iguanas of each island had 1.5-fold higher bite rates during foraging, and their absolute food intake per day was 35% that of the largest Iguanas. However, food intake per bite per gram of body mass was about twice as high for small Iguanas as for large Iguanas. Large Iguanas of both islands showed a marked decline in body mass during the two study years, whereas small Iguanas (SVL 200 mm SVL on Genovesa and >310 mm SVL on Santa Fe significantly lost mass; in the more productive year (1992/1993), thresholds were 230 mm and 350 mm SVL, respectively. Thus, food abundance (length and turnover of algal swards) explained differences in adult body length and mass between islands as a result of energetic limitation. On a given island, foraging efficiency (intake/bite) explained the negative energy balance of large compared to small Iguanas. This also explained why, on both islands, the largest animals suffered higher mortality rates than did medium-sized ones when food was scarce. The finding that small animals outcompeted larger ones because of their higher foraging efficiency resembles the grazing succession in ungulate herbivores.
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body size and sexual size dimorphism in Marine Iguanas fluctuate as a result of opposing natural and sexual selection an island comparison
Evolution, 1997Co-Authors: Martin Wikelski, Fritz TrillmichAbstract:Body size is often assumed to represent the outcome of conflicting selection pressures of natural and sexual selection. Marine Iguana (Amblyrhynchus cristatus) populations in the Galapagos exhibit 10-fold differences in body mass between island populations. There is also strong sexual size dimorphism, with males being about twice as heavy as females. To understand the evolutionary processes shaping body size in Marine Iguanas, we analyzed the selection differentials on body size in two island populations (max. male mass 900 g in Genovesa, 3500 g in Santa Fe). Factors that usually confound any evolutionary analysis of body sizes-predation, interspecific food competition, reproductive role division-are ruled out for Marine Iguanas. We show that, above hatchlings, mortality rates increased with body size in both sexes to the same extent. This effect was independent of individual age. The largest animals (males) of each island were the first to die once environmental conditions deteriorated (e.g., during El Nifios). This sex-biased mortality was the result of sexual size dimorphism, but at the same time caused sexual size dimorphism to fluctuate. Mortality differed between seasons (selection differentials as low as -1.4) and acted on different absolute body sizes between islands. Both males and females did not cease growth when an optimal body size for survival was reached, as demonstrated by the fact that individual adult body size phenotypically increased in each population under favorable environmental conditions beyond naturally selected limits. But why did Marine Iguanas grow "too large" for survival? Due to lek mating, sexual selection constantly favored large body size in males (selection differentials up to +0.77). Females only need to reach a body size sufficient to produce surviving offspring. Thereafter, large body size of females was less favored by fertility selection than large size in males. Resulting from these different selection pressures on male and female size, sexual size dimorphism was mechanistically caused by the fact that females matured at an earlier age and size than males, whereafter they constantly allocated resources into eggs, which slowed growth. The observed allometric increase in sexual size dimorphism is explained by the fact that the difference between these selective processes becomes larger as energy abundance in the environment increases. Because body size is generally highly heritable, these selective processes are expected to lead to genetic differences in body size between islands. We propose a common-garden experiment to determine the influence of genetic factors and phenotypic reaction norms of final body size.
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foraging strategies of the galapagos Marine Iguana amblyrhynchus cristatus adapting behavioral rules to ontogenetic size change
Behaviour, 1994Co-Authors: Martin Wikelski, Fritz TrillmichAbstract:[Ontogenetic development in reptiles entails major changes in size-related foraging options. We studied the changes in foraging behavior of Marine Iguanas. In this species, size increases about twenty- to hundredfold from hatching to full adult size. The foraging strategy of Marine Iguanas was studied at Miedo on Santa Fe Island in the Galapagos archipelago. During low tide, large Marine Iguanas (>250 mm snout vent length (SVL)) foraged more in the lower intertidal than small ones ( 250 mm snout vent length (SVL)) foraged more in the lower intertidal than small ones (<250 mm SVL) which preferred the upper intertidal with higher temperatures and less frequent wave washing. Animals usually returned to the same foraging site day after day and had lower food intake after changing their foraging site. Feeding accounted for 60% of the time spent in the intertidal. Smaller animals fed every day, larger ones only every other day. Smaller individuals shuttled faster between foraging and basking sites than larger ones. Total feeding time per day was, however, the same for both size classes. At neap tides (= high water level at low tide) animals had shorter foraging bouts than at spring tides with much lower water levels at peak low tide. Length of feeding bouts depended most on wave action, time of low tide (during the daylight period), and body mass of an animal. Small animals fed significantly less at higher than at lower wave activities. All animals on Santa Fe spent more time feeding in the intertidal than in the subtidal. Only large males additionally foraged subtidally and the more so the bigger they were. During the reproductive season, territorial males were less likely to go foraging, but when feeding, territorials fed more subtidally than nonterritorials, went foraging earlier, and spent less time foraging in the IT than nonterritorials. Ability to resist wave drag increased with body size but did not decrease at lower body temperature, whereas running speed did so significantly. Bite frequency during foraging also decreased with decreasing body temperature and smaller, younger animals had higher bite rates than older, bigger ones. White-painted animals rewarmed slower than naturally black ones and partially compensated for this by shortening foraging bouts but increasing their number. The observed age-related changes in foraging behavior can be explained by postulating a rule of the form 'forage while warm and warm up when getting inefficient at grazing'. Of course, animals will also stop feeding should the stomach be filled before the end of the low tide cycle. To explain age- and motivation-related differences in foraging behavior, the only change that needs to be postulated is in the thresholds of body temperature inducing switches from foraging to warming-up and back. These changes are adaptive responses to size-related changes in costs and benefits of foraging in a cool, wavewashed environment.]
Trillmich Fritz - One of the best experts on this subject based on the ideXlab platform.
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The spatial ecology of invasive feral catsFelis catuson San Cristobal, Galapagos: first insights from GPS collars
'Springer Science and Business Media LLC', 2020Co-Authors: Macleod A., Cooke S. C., Trillmich FritzAbstract:MacLeod A, Cooke SC, Trillmich F. The spatial ecology of invasive feral catsFelis catuson San Cristobal, Galapagos: first insights from GPS collars. MAMMAL RESEARCH. 2020;65(3):621-628.The dangers posed by invasive species for endemic island wildlife are well recognised. Introduced domestic cats (Felis catus) represent a significant threat to several endemic species of the Galapagos archipelago-including hatchling Marine Iguanas (Amblyrhynchus cristatus) and potentially green turtles (Chelonia mydas)-yet little is known about their spatial ecology and habitat use on these islands. Here, we describe a pilot study using GPS collars to track the movements of three feral cats at a site of conservation interest on San Cristobal Island. Based on 175 days of GPS data, we undertook spatial analyses to ascertain home ranges, and to investigate the overlap of ranges between the cats and potential prey species. Average home range was 1.27 km(2)(1.12-1.46 km(2)), which-though small for feral cats-is in keeping with previous findings in Galapagos. We found the cats did use the habitat of a small Marine Iguana population but did not change their spatial habits before and after Iguana hatchlings appeared. Changes over time in the daily movements of one cat indicated a possible response of the individual to the presence of hatchling green turtles (Chelonia mydas); though the data here are insufficient to show whether the cat was hunting these hatchlings. We recommend similar work be undertaken in areas with larger Marine Iguana populations, where hatchlings could represent a potentially important food source for invasive feral cats, as well as further work to determine the threat posed by cats to turtle hatchlings in Galapagos
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New highly polymorphic microsatellite loci for the Galapagos Marine Iguana, Amblyrhynchus cristatus
'Brill', 2012Co-Authors: Macleod Amy, Trillmich Fritz, Koch Volker, Garcia-parra Carolina, Steinfartz SebastianAbstract:MacLeod A, Koch V, Garcia-Parra C, Trillmich F, Steinfartz S. New highly polymorphic microsatellite loci for the Galapagos Marine Iguana, Amblyrhynchus cristatus. Amphibia-Reptilia. 2012;33(3-4):533-536.We describe the development and characterisation of six new dinucleotide motif microsatellite loci for populations of Marine Iguanas (Amblyrhynchus cristatus), endemic to the Galapagos archipelago. Primers were based on microsatellite-bearing sequences and initially developed using universally labelled primers. When analysed across 5 populations (representing 150 individuals), new loci displayed, on average, high levels of genetic diversity (range: 2-13 alleles, mean: 5.73) and values of heterozygosity (range: 0.0-0.906, mean: 0.605). No consistent deviations from Hardy-Weinberg equilibrium or significant linkage disequilibrium were observed, and all loci were shown to be free of common microsatellite errors. Utilising the 13 previously available microsatellite loci for this species, we describe here four multiplex combinations for the successful amplification of 19 microsatellite loci for Marine Iguanas. This powerful set of highly polymorphic markers will allow researchers to explore future questions regarding the ecology, evolution, and conservation of this unique species
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Hybridization between the Galapagos land and Marine Iguana (Conolophus subcristatus and Amblyrhynchus cristatus) on Plaza Sur
'Wiley', 1997Co-Authors: Rassmann K, Trillmich Fritz, Tautz DAbstract:Rassmann K, Trillmich F, Tautz D. Hybridization between the Galapagos land and Marine Iguana (Conolophus subcristatus and Amblyrhynchus cristatus) on Plaza Sur. JOURNAL OF ZOOLOGY. 1997;242(4):729-739.Hybridization plays an important role in the evolution of some of the vertebrate taxa on the Galapagos Islands, such as the Darwin finches. Conversely, only a single possible hybrid between the Galapagos Marine Iguana (Amblyrhynchus) and the land Iguana (Conolophus) has been reported from the island Plaza Sur. In this paper, the hybrid status of a morphologically unusual Iguana from this island is confirmed, using restriction fragment length polymorphism (RFLP) analyses of the nuclear ribosomal DNA (rDNA). Sequencing of the hybrid's mitochondrial cytochrome b gene revealed that it was the offspring of a female land Iguana and a male Marine Iguana. Preliminary molecular analyses of morphologically typical Marine and land Iguanas from Plaza Sur did not detect introgression of nuclear or mitochondrial markers between species. Thr potential significance of hybridization for the evolution of the Plaza Sur Iguana populations is discussed
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The microevolution of the Galapagos Marine Iguana Amblyrhynchus cristatus assessed by nuclear and mitochondrial genetic analyses
'Wiley', 1997Co-Authors: Rassmann K, Trillmich Fritz, Tautz D, Gliddon CAbstract:Rassmann K, Tautz D, Trillmich F, Gliddon C. The microevolution of the Galapagos Marine Iguana Amblyrhynchus cristatus assessed by nuclear and mitochondrial genetic analyses. MOLECULAR ECOLOGY. 1997;6(5):437-452.Marine Iguanas may have inhabited the Galapagos archipelago and its former, now sunken islands for more than 10 million years (Myr). It is therefore surprising that morphological and immunological data indicate little evolutionary divergence within the genus. We utilized mitochondrial DNA (mtDNA) sequence analyses and nuclear DNA fingerprinting to re-evaluate the level and pattern of genetic differentiation among 22 Marine Iguana populations from throughout the archipelago. Both genetic marker systems detect a low level of within-genus divergence, but they show contrasting levels of geographical subdivision among the populations. The mitochondrial gene pools of populations from different regions of the archipelago are isolated, and the mtDNA pattern appears to follow the sequence in which the islands were colonized by Marine Iguanas. Conversely, the nuclear DNA study indicates substantial interpopulational gene exchange, and the geographical distribution of the nuclear markers seems to be determined by isolation by distance among the populations. The natural history of Marine Iguanas suggests that the contrasting nuclear and mitochondrial DNA patterns result from an asymmetric migration behaviour of the two sexes, with higher (active and passive) interisland dispersal for males than females. Separate genetic analyses for the sexes appear to support this hypophesis. Based on these findings, a scenario is proposed that explains the Marine Iguanas' low genetic divergence, notwithstanding their long evolutionary history in the Galapagos archipelago
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Energy limits to body size in a grazing reptile, the Galapagos Marine Iguana
'Wiley', 1997Co-Authors: Wikelski M, Trillmich FritzAbstract:Wikelski M, Carrillo V, Trillmich F. Energy limits to body size in a grazing reptile, the Galapagos Marine Iguana. ECOLOGY. 1997;78(7):2204-2217.Galapagos Marine Iguana (Amblyrhynchus cristatus) populations show considerable differences in body size. Adult body mass varies by more than 10-fold, and body length (snout-vent length, SVL) varies by approximate to 2.2-fold. Predation and interspecific food competition are largely absent and can be excluded as potential forces explaining differences in body size among populations. This provides an ideal system in which to determine how proximate environmental factors affect adult body size, We compared the small Iguanas from Genovesa Island (mean adult male SVL 250 mm) to the larger Santa Fe Iguanas (mean adult male SVL 400 mm). Marine Iguanas forage on intertidal algae pastures in scramble competition. Energy availability was lower on Genovesa than on Santa Fe, because of lower Marine productivity on Genovesa. The length of grazable algal turf decreased with increasing sea surface temperature (SST). SST was approximate to 2 degrees C lower on Santa Fe than on Genovesa, implying approximate to 1.5 mm lower algae pastures on the latter. Genovesa showed a fivefold lower standing algal biomass and a twofold lower productivity of algae pastures than did Santa Fe. The smallest Iguanas of each island had approximate to 1.5-fold higher bite rates during foraging, and their absolute food intake per day was 35% that of the largest Iguanas. However, food intake per bite per gram of body mass was about twice as high for small Iguanas as for large Iguanas. Large Iguanas of both islands showed a marked decline in body mass during the two study years, whereas small Iguanas (SVL 200 mm SVL on Genovesa and > 310 mm SVL on Santa Fe significantly lost mass; in the more productive year (1992/1993), thresholds were 230 mm and 350 mm SVL, respectively. Thus, food abundance (length and turnover of algal swards) explained differences in adult body length and mass between islands as a result of energetic limitation. On a given island, foraging efficiency (intake/bite) explained the negative energy balance of large compared to small Iguanas. This also explained why, on both islands, the largest animals suffered higher mortality rates than did medium-sized ones when food was scarce. The finding that small animals outcompeted larger ones because of their higher foraging efficiency resembles the grazing succession in ungulate herbivores
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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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.
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A set of highly discriminating microsatellite loci for the Galápagos Marine Iguana Amblyrhynchus cristatus
Molecular Ecology Notes, 2006Co-Authors: Sebastian Steinfartz, Adalgisa CacconeAbstract:We describe here the cloning of 12 (7 dinucleotide, 1 trinucleotide and 4 tetranucleotide) microsatellite loci for the Galapagos Marine Iguana Amblyrhynchus cristatus . When tested for individuals from five different island populations on the Galapagos archipelago, high genetic diversities (9–20 alleles per locus) and heterozygosities (0.200–0.944) were observed. All loci showed no obvious deviations from Hardy–Weinberg equilibrium. The new set of microsatellite loci was able to assign individuals reliably to their island of origin, thus being able to discriminate between residents and migrants between islands.