| 1. |
- Jeglinski, Jana W. E., et al.
(författare)
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Differences in foraging ecology align with genetically divergent ecotypes of a highly mobile marine top predator
- 2015
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 179:4, s. 1041-1052
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Tidskriftsartikel (refereegranskat)abstract
- Foraging differentiation within a species can contribute to restricted gene flow between ecologically different groups, promoting ecological speciation. Galapagos sea lions (Zalophus wollebaeki) show genetic and morphological divergence between the western and central archipelago, possibly as a result of an ecologically mediated contrast in the marine habitat. We use global positioning system (GPS) data, time-depth recordings (TDR), stable isotope and scat data to compare foraging habitat characteristics, diving behaviour and diet composition of Galapagos sea lions from a western and a central colony. We consider both juvenile and adult life stages to assess the potential role of ontogenetic shifts that can be crucial in shaping foraging behaviour and habitat choice for life. We found differences in foraging habitat use, foraging style and diet composition that aligned with genetic differentiation. These differences were consistent between juvenile and adult sea lions from the same colony, overriding age-specific behavioural differences. Our study contributes to an understanding of the complex interaction of ecological condition, plastic behavioural response and genetic make-up of interconnected populations.
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| 2. |
- Krueger, Oliver, et al.
(författare)
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Disentangling the Contribution of Sexual Selection and Ecology to the Evolution of Size Dimorphism in Pinnipeds
- 2014
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 68:5, s. 1485-1496
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Tidskriftsartikel (refereegranskat)abstract
- The positive relationship between sexual size dimorphism (SSD) and harem size across pinnipeds is often cited as a textbook example of sexual selection. It assumes that female aggregation selected for large male size via male–male competition. Yet, it is also conceivable that SSD evolved prior to polygyny due to ecological forces. We analyzed 11 life-history traits in 35 pinniped species to determine their coevolutionary dynamics and infer their most likely evolutionary trajectories contrasting these two hypotheses. We find support for SSD having evolved prior to changes in the mating system, either as a consequence of niche partitioning during aquatic foraging or in combination with sexual selection on males to enforce copulations on females. Only subsequently did polygyny evolve, leading to further coevolution as the strength of sexual selection intensified. Evolutionary sequence analyses suggest a polar origin of pinnipeds and indicate that SSD and polygyny are intrinsically linked to a suite of ecological and life-history traits. Overall, this study calls for the inclusion of ecological variables when studying sexual selection and argues for caution when assuming causality between coevolving traits. It provides novel insights into the role of sexual selection for the coevolutionary dynamics of SSD and mating system.
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| 3. |
- Lenz, Tobias L., et al.
(författare)
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Divergent allele advantage at MHC-DRB through direct and maternal genotypic effects and its consequences for allele pool composition and mating
- 2013
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 280:1762, s. 20130714-
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Tidskriftsartikel (refereegranskat)abstract
- It is still debated whether main individual fitness differences in natural populations can be attributed to genome-wide effects or to particular loci of outstanding functional importance such as the major histocompatibility complex (MHC). In a long-term monitoring project on Galapagos sea lions (Zalophus wollebaeki), we collected comprehensive fitness and mating data for a total of 506 individuals. Controlling for genome-wide inbreeding, we find strong associations between the MHC locus and nearly all fitness traits. The effect was mainly attributable to MHC sequence divergence and could be decomposed into contributions of own and maternal genotypes. In consequence, the population seems to have evolved a pool of highly divergent alleles conveying near-optimal MHC divergence even by random mating. Our results demonstrate that a single locus can significantly contribute to fitness in the wild and provide conclusive evidence for the 'divergent allele advantage' hypothesis, a special form of balancing selection with interesting evolutionary implications.
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| 4. |
- Lopes, Fernando, et al.
(författare)
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Fine-scale matrilineal population structure in the Galapagos fur seal and its implications for conservation management
- 2015
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 16:5, s. 1099-1113
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Tidskriftsartikel (refereegranskat)abstract
- Females of many pinniped species generally exhibit strong fine-scale philopatry, but it is unclear over what spatial scale this behavior may translate into genetic population structure. We conducted a population genetic survey in the Galapagos fur seal, Arctocephalus galapagoensis, an endangered pinniped endemic to a small geographic range in the northwest of the Galapagos archipelago. To assess patterns of genetic diversity levels and population differentiation, we analyzed part of the mitochondrial control region (mtDNA) and 18 microsatellites DNA markers. We detected similar levels of genetic diversity to many other pinniped species (h = 0.86, pi = 0.012, A = 7.44) despite severe anthropogenic exploitation in the nineteenth century and recurrent population crashes due to recent climatic perturbations associated with El Nio Southern Oscillation events. We further found remarkably strong fine-scale matrilineal population structure, with 33.9 % of the mtDNA variation being partitioned among colonies separated by as little as 70 km swimming distance. In contrast, population structure inferred from nuclear markers was weak. Our findings provide further evidence that natal philopatry can translate into fine-scale genetic population structure in highly mobile species. We discuss the relevance of our results for the fine-scale conservation management of this species with a very restricted geographic range.
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| 5. |
- Mueller, Birte, et al.
(författare)
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Growth under uncertainty : The influence of marine variability on early development of Galapagos sea lions
- 2011
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Ingår i: Marine mammal science. - : Wiley. - 0824-0469 .- 1748-7692. ; 27:2, s. 350-365
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Development implies a change in allocation of resources from somatic growth to reproduction. In a highly variable environment, growth can vary from year to year thereby influencing the long-term life history perspective. The Galapagos sea lion (Zalophus wollebaeki) lives in a highly unpredictable marine environment in which food abundance varies not only seasonally, but also annually due to El Niño. Galapagos sea lions are restricted to a patch of cold upwelling waters surrounding the archipelago and are closely tied to land as nursing females alternate between foraging at sea and nursing ashore. Therefore, their offspring are especially vulnerable to ocean warming causing reduced food abundance. We found a significant correlation between sea surface temperature (SST) and early growth: Both mass at birth and linear growth within the first 2 mo of life correlated negatively with SST. Absolute mass gain was higher for males, but both sexes gained equally 1.9% of birth mass per day. Until the age of 3 yr male and female juveniles showed similar growth to an asymptotic mass of 40 and 35 kg, respectively. As a consequence of the highly variable environment, the plasticity in growth strategy of Galapagos sea lion juveniles appears wider than that of all other sea lions allowing them to cope with poor conditions.
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| 6. |
- Pörschmann, Ulrich, et al.
(författare)
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Male reproductive success and its behavioural correlates in a polygynous mammal, the Galapagos sea lion (Zalophus wollebaeki)
- 2010
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 19:12, s. 2574-2586
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Tidskriftsartikel (refereegranskat)abstract
- Sexual selection theory predicts competitive males and choosy females. Nevertheless, since molecular marker-based studies, paternity outside the expected mating patterns has increasingly been described. Even in highly polygynous systems, where paternity is expected to be strongly skewed towards large, dominant males, alternative mating tactics have been suggested. We examined reproductive success in the polygynous Galapagos sea lion (Zalophus wollebaeki). Semiaquatic territoriality allows females to move freely and may lower the degree of polygyny otherwise suggested by both territorial behaviour and strong sexual dimorphism. We assigned paternities with 22 microsatellites and analysed how male reproductive success was related to size, dominance status, intrasexual agonistic behaviour, proximity to females, and attendance in the colony. Male behaviour was consistent across two seasons for all parameters under consideration. Attendance was by far the most important determinant of paternal success. Skew in reproductive success towards large, dominant males was weak and dominance status played no role. This appears to be caused by an extremely long reproductive season lasting five or more months, making it difficult for any male to monopolize receptive females. Females seem to choose displaying males that were present in the colony for a long time rather than dominance per se. Sexual dimorphism in Galapagos sea lions may thus be more influenced by selection for fasting than fighting ability. Our data provide further evidence for alternative mating tactics, as several males gained relatively high reproductive success despite short attendance and hardly any involvement in agonistic interactions.
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| 7. |
- Trillmich, Fritz, et al.
(författare)
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On the Challenge of Interpreting Census Data : Insights from a Study of an Endangered Pinniped
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Population monitoring is vital for conservation and management. However, simple counts of animals can be misleading and this problem is exacerbated in seals (pinnipeds) where individuals spend much time foraging away from colonies. We analyzed a 13-year-series of census data of Galapagos sea lions (Zalophus wollebaeki) from the colony of Caamano, an islet in the center of the Galapagos archipelago where a large proportion of animals was individually marked. Based on regular resighting efforts during the cold, reproductive (cold-R; August to January) and the warm, non-reproductive (warm-nR; February to May) season, we document changes in numbers for different sex and age classes. During the cold-R season the number of adults increased as the number of newborn pups increased. Numbers were larger in themorning and evening than around mid-day and not significantly influenced by tide levels. More adults frequented the colony during the warm-nR season than the cold-R season. Raw counts suggested a decline in numbers over the 13 years, but Lincoln-Petersen (LP-) estimates (assuming a closed population) did not support that conclusion. Raw counts and LP estimates were not significantly correlated, demonstrating the overwhelming importance of variability in attendance patterns of individuals. The probability of observing a given adult in the colony varied between 16%(mean for cold-R season) and 23%(warm-nR season) and may be much less for independent 2 to 4 year olds. Dependent juveniles (up to the age of about 2 years) are observed much more frequently ashore (35% during the cold-R and 50% during the warm-nR seasons). Simple counts underestimate real population size by a factor of 4-6 and may lead to erroneous conclusions about trends in population size.
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