| 1. |
- Gonzalez-Voyer, Alejandro, et al.
(author)
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Larger brain size indirectly increases vulnerability to extinction in mammals
- 2016
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 70:6, s. 1364-1375
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Journal article (peer-reviewed)abstract
- Although previous studies have addressed the question of why large brains evolved, we have limited understanding of potential beneficial or detrimental effects of enlarged brain size in the face of current threats. Using novel phylogenetic path analysis, we evaluated how brain size directly and indirectly, via its effects on life history and ecology, influences vulnerability to extinction across 474 mammalian species. We found that larger brains, controlling for body size, indirectly increase vulnerability to extinction by extending the gestation period, increasing weaning age, and limiting litter sizes. However, we found no evidence of direct, beneficial, or detrimental effects of brain size on vulnerability to extinction, even when we explicitly considered the different types of threats that lead to vulnerability. Order-specific analyses revealed qualitatively similar patterns for Carnivora and Artiodactyla. Interestingly, for Primates, we found that larger brain size was directly (and indirectly) associated with increased vulnerability to extinction. Our results indicate that under current conditions, the constraints on life history imposed by large brains outweigh the potential benefits, undermining the resilience of the studied mammals. Contrary to the selective forces that have favored increased brain size throughout evolutionary history, at present, larger brains have become a burden for mammals.
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| 2. |
- Duarte, Helder, et al.
(author)
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Can amphibians take the heat? : Vulnerability to climate warming in subtropical and temperate larval amphibian communities
- 2012
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In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 18:2, s. 412-421
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Journal article (peer-reviewed)abstract
- Predicting the biodiversity impacts of global warming implies that we know where and with what magnitude these impacts will be encountered. Amphibians are currently the most threatened vertebrates, mainly due to habitat loss and to emerging infectious diseases. Global warming may further exacerbate their decline in the near future, although the impact might vary geographically. We predicted that subtropical amphibians should be relatively susceptible to warming-induced extinctions because their upper critical thermal limits (CTmax) might be only slightly higher than maximum pond temperatures (Tmax). We tested this prediction by measuring CTmax and Tmax for 47 larval amphibian species from two thermally distinct subtropical communities (the warm community of the Gran Chaco and the cool community of Atlantic Forest, northern Argentina), as well as from one European temperate community. Upper thermal tolerances of tadpoles were positively correlated (controlling for phylogeny) with maximum pond temperatures, although the slope was steeper in subtropical than in temperate species. CTmax values were lowest in temperate species and highest in the subtropical warm community, which paradoxically, had very low warming tolerance (CTmaxTmax) and therefore may be prone to future local extinction from acute thermal stress if rising pond Tmax soon exceeds their CTmax. Canopy-protected subtropical cool species have larger warming tolerance and thus should be less impacted by peak temperatures. Temperate species are relatively secure to warming impacts, except for late breeders with low thermal tolerance, which may be exposed to physiological thermal stress in the coming years.
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| 3. |
- Dugo-Cota, Alvaro, et al.
(author)
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A test of the integrated evolutionary speed hypothesis in a Neotropical amphibian radiation
- 2015
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In: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 24:7, s. 804-813
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Journal article (peer-reviewed)abstract
- Aim - The evolutionary speed hypothesis is a mechanistic explanation for the latitudinal biodiversity gradient. The recently extended integrated evolutionary speed hypothesis (IESH) proposes that temperature, water availability, population size and spatial heterogeneity influence the rate of molecular evolution which, in turn, affects diversification. However, the evidence for some of the associations predicted by the IESH is not conclusive, and in some cases is contradictory.Location - The Neotropics.Methods - Using a comparative Bayesian method we tested the following predictions of the IESH: the association between the rate of molecular evolution and temperature (and elevation and latitude, as proxies), water availability (using precipitation and relative humidity as proxies), productivity and rate of diversification. We also accounted for the potential confounding effects of body size and UVB radiation. We tested these predictions separately in mitochondrial and nuclear genes.Results - Substitution rates of mitochondrial and nuclear genes were positively associated with temperature and negatively with elevation, while only the mitochondrial coding gene rate was associated with UVB radiation. However, when controlling for temperature, the association between substitution rate and elevation and UVB radiation disappeared, while a negative association with precipitation emerged. Moreover, diversification events were positively correlated with the rate of molecular evolution but only in mitochondrial genes.Main conclusions - Our results support two key predictions of the IESH. They highlight the important association between rate of molecular evolution and temperature within a recently diverged group and also confirm the positive association between molecular evolution and diversification rate, although only in mitochondrial genes. However, the lack of association between diversification and temperature and the low effect size of the relationship between substitution rates and diversification in mitochondrial genes emphasize the important role other factors, such as time, spatial heterogeneity and population size might have in the origin and maintenance of the latitudinal biodiversity gradient.
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| 4. |
- Eckerström-Liedholm, Simon, 1988-
(author)
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Behavioural, physiological and morphological correlates of life-history in killifishes − a macroevolutionary approach
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Life-histories commonly evolve along a continuum from short-lived and fecund, to long-lived and less fecund. Because life-history traits are mostly components of reproduction and survival, understanding the causes and consequences of life-history variation is at the core of evolutionary biology. This thesis aims to identify what other key traits (e.g. behavioural, physiological and morphological traits) covary with life-history, and why. Numerous hypotheses describe how life-history might be associated with other traits, with life-history trade-offs often considered to be a primary driver of any such relationships. For example, since resources are limited, increased investment in one trait must lead to decreased investment in one or several other traits, all else equal. Hypotheses on the relationship between life-history and other traits have been tested in many studies, but empirical studies in controlled experimental settings are rare. In this thesis I explore how behaviour, physiology and morphology relate to variation along the life-history continuum from fast to slow, in a system with substantial variation in life-history traits - the killifishes.I began by exploring the patterns of egg to body size allometry in killifishes (Paper I), where species with faster life-histories showed indications of constraints on the independent evolution of egg size and body size. Furthermore, I found evidence of differences in variance and in the rates of evolution of egg size and body size across species, potentially caused by the colonisation of ephemeral habitats, which could have selected for adaptations that lead to differences in size.I then performed a comparative common garden study (Paper II) of the pace-of-life syndrome hypothesis, which predicts that species with fast life-histories should take larger risks in order to maintain their increased reproductive rate. I obtained data on risk taking behaviours, including movement, tendency to enter an open environment, and aggressiveness, in addition to metabolic rate, for 20 species of killifish, with multiple replicates per species. The results indicated trait dependent associations with life-history, where aggression seemed to correlate positively with speed of life-history, in congruence with our prediction.Next, my colleagues and I assessed the association between life-history and sexual selection (Paper III), in order to determine if investment in secondary sexual traits might be traded off against survival in killifish. Fin size was found to be negatively associated with escape performance in a simulated predator attack, suggesting survival costs for individuals with large fins. Importantly, fin size was also positively associated with the speed of life-history, supporting the hypothesis that costs to survival probability is lower in fast-living species.Lastly, I tested the hypothesized negative covariation between relative brain size and speed of life-history, by collecting and analysing brain size measurements for 21 species of killifish (Paper IV). Surprisingly, a positive relationship between speed of life-history and relative brain size was found for adults, although juveniles did not differ in relative brain size. This implies at least one of two things: either there is no need to trade off brain size with life-history since resource acquisition is higher, or brain size and life-history are traded-off with other traits.In conclusion, I show that previously found trade-offs between life-history and investment in other costly traits are only sometimes present, when tested in a system with substantial divergences in the speed of life-history. I also provide evidence for a trait dependent association between life-history and among species differences in risk-taking and metabolic rate.
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| 5. |
- Eckerström-Liedholm, Simon, 1988-, et al.
(author)
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Fast life-histories are associated with larger brain size in killifishes
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Other publication (other academic/artistic)abstract
- Comparative studies suggest a negative relationship between pace of life-history, and relative energetic investment into brain size. However, since brain size typically evolves as a correlated response to selection on body size, any lag in brain size evolution will result in a shift in relative brain size (e.g. small body – large relative brain size).Coevolution between body size and life-history hence has the potential to drive secondary associations between relative brain size and life-history, when body size is correlated with life history. However, as far as we know, the relationship between relative brain size and life-history strategy has not been examined in systems that simultaneously present marked contrasts in life-history but no concordant shifts in body size. Using a common garden approach, we test the association between relative brain size and life-history in 21 species of killifish; a study system that fulfils the aforementioned requirements. Contrary to the prediction that brain size evolves through energetic trade-offs with life-history, we found that adults, but not juveniles, of fast-living species had larger relative brain sizes. Rather than an energetic link to life-history, our results suggest that fast- and slow-living species differ in terms of how cognitively demanding environments they inhabit are, or alternatively in the ontogenetic timing of somatic vs. neural growth.
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| 6. |
- Eckerström-Liedholm, Simon, et al.
(author)
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Macroevolutionary evidence suggests trait-dependent coevolution between behavior and life-history
- 2019
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 73:11, s. 2312-2323
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Journal article (peer-reviewed)abstract
- Species with fast life-histories typically prioritize current over future reproductive events, compared to species with slow life-histories. These species therefore require greater energetic input into reproduction, and also likely have less time to realize their reproductive potential. Hence, behaviors that increase access to both resources and mating opportunities, at a cost of increased mortality risk, could coevolve with the pace of life-history. However, whether this prediction holds across species, remains untested under standardized conditions. Here, we test how risky behaviors, which facilitate access to resources and mating opportunities (i.e., activity, boldness, and aggression), along with metabolic rate, coevolve with the pace of life-history across 20 species of killifish that present remarkable divergences in the pace of life-history. We found a positive association between the pace of life-history and aggression, but interestingly not with other behavioral traits or metabolic rate. Aggression is linked to interference competition, and in killifishes is often employed to secure mates, while activity and boldness are more relevant for exploiting energetic resources. Our results suggest that the trade-off between current and future reproduction plays a more prominent role in shaping mating behavior, while behaviors related to energy acquisition may be influenced by ecological factors.
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| 7. |
- Eckerström-Liedholm, Simon, 1988-, et al.
(author)
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Macroevolutionary evidence suggests trait-dependent coevolution between behaviour and life-history
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Other publication (other academic/artistic)abstract
- Species with fast life-histories prioritize current over future reproduction, which ought to require greater energetic resources, but also results in a shorter time-period to realize their reproductive potential, compared to slow life-histories, which prioritize future reproduction. Hence, behaviours that increase access to both resources and mating opportunities, at a cost of increased mortality risk, are thought to coevolve with the pace of life-history. However, whether this prediction holds across species, is yet to be tested under standardized conditions. Here, we test how potentially risky behaviours, which facilitate access to resources and mating opportunities (i.e. activity, boldness and aggression), along with metabolic rate, correlates with the pace of life-history across 20 species of killifish, which present a remarkable divergence in the pace of their life-histories. We found a positive correlation between the pace of life-history and aggression, but not with any other behavioural traits or metabolic rate. Aggression is often expressed in the context of mating, while the other behaviours we measured might be more relevant for access to energetic resources. Our results therefore suggest that the trade-off between current and future reproduction plays a more prominent role in shaping mating behaviour, while behaviours related to acquisition of energetic resources may be more affected by ecological factors.
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| 8. |
- Eckerström-Liedholm, Simon, et al.
(author)
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Time-limited environments affect the evolution of egg-body size allometry
- 2017
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 71:7, s. 1900-1910
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Journal article (peer-reviewed)abstract
- Initial offspring size is a fundamental component of absolute growth rate, where large offspring will reach a given adult body size faster than smaller offspring. Yet, our knowledge regarding the coevolution between offspring and adult size is limited. In time-constrained environments, organisms need to reproduce at a high rate and reach a reproductive size quickly. To rapidly attain a large adult body size, we hypothesize that, in seasonal habitats, large species are bound to having a large initial size, and consequently, the evolution of egg size will be tightly matched to that of body size, compared to less time-limited systems. We tested this hypothesis in killifishes, and found a significantly steeper allometric relationship between egg and body sizes in annual, compared to nonannual species. We also found higher rates of evolution of egg and body size in annual compared to nonannual species. Our results suggest that time-constrained environments impose strong selection on rapidly reaching a species-specific body size, and reproduce at a high rate, which in turn imposes constraints on the evolution of egg sizes. In combination, these distinct selection pressures result in different relationships between egg and body size among species in time-constrained versus permanent habitats.
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| 9. |
- Gonzalez-Voyer, Alejandro, et al.
(author)
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Brain structure evolution in a basal vertebrate clade: evidence from phylogenetic comparative analysis of cichlid fishes
- 2009
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In: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 9, s. 238-
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Journal article (peer-reviewed)abstract
- Background: The vertebrate brain is composed of several interconnected, functionally distinct structures and much debate has surrounded the basic question of how these structures evolve. On the one hand, according to the 'mosaic evolution hypothesis', because of the elevated metabolic cost of brain tissue, selection is expected to target specific structures mediating the cognitive abilities which are being favored. On the other hand, the 'concerted evolution hypothesis' argues that developmental constraints limit such mosaic evolution and instead the size of the entire brain varies in response to selection on any of its constituent parts. To date, analyses of these hypotheses of brain evolution have been limited to mammals and birds; excluding Actinopterygii, the basal and most diverse class of vertebrates. Using a combination of recently developed phylogenetic multivariate allometry analyses and comparative methods that can identify distinct rates of evolution, even in highly correlated traits, we studied brain structure evolution in a highly variable clade of ray-finned fishes; the Tanganyikan cichlids.Results: Total brain size explained 86% of the variance in brain structure volume in cichlids, a lower proportion than what has previously been reported for mammals. Brain structures showed variation in pair-wise allometry suggesting some degree of independence in evolutionary changes in size. This result is supported by variation among structures on the strength of their loadings on the principal size axis of the allometric analysis. The rate of evolution analyses generally supported the results of the multivariate allometry analyses, showing variation among several structures in their evolutionary patterns. The olfactory bulbs and hypothalamus were found to evolve faster than other structures while the dorsal medulla presented the slowest evolutionary rate.Conclusion: Our results favor a mosaic model of brain evolution, as certain structures are evolving in a modular fashion, with a small but non-negligible influence of concerted evolution in cichlid fishes. Interestingly, one of the structures presenting distinct evolutionary patterns within cichlids, the olfactory bulbs, has also been shown to evolve differently from other structures in mammals. Hence, our results for a basal vertebrate clade also point towards a conserved developmental plan for all vertebrates.
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| 10. |
- Gonzalez-Voyer, Alejandro, et al.
(author)
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Distinct Evolutionary Patterns of Brain and Body Size During Adaptive Radiation
- 2009
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 63:9, s. 2266-2274
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Journal article (peer-reviewed)abstract
- Morphological traits are often genetically and/or phenotypically correlated with each other and such covariation can have an important influence on the evolution of individual traits. The strong positive relationship between brain size and body size in vertebrates has attracted a lot of interest, and much debate has surrounded the study of the factors responsible for the allometric relationship between these two traits. Here, we use comparative analyses of the Tanganyikan cichlid adaptive radiation to investigate the patterns of evolution for brain size and body size separately. We found that body size exhibited recent bursts of rapid evolution, a pattern that is consistent with divergence linked to ecological specialization. Brain weight on the other hand, showed no bursts of divergence but rather evolved in a gradual manner. Our results thus show that even highly genetically correlated traits can present markedly different patterns of evolution, hence interpreting patterns of evolution of traits from correlations in extant taxa can be misleading. Furthermore, our results suggest, contrary to expectations from theory, that brain size does not play a key role during adaptive radiation.
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