| 1. |
- Bererhi, Badreddine, et al.
(författare)
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Limited effects of inbreeding on breeding coloration
- 2023
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Ingår i: Journal of Heredity. - : Oxford University Press (OUP). - 0022-1503 .- 1465-7333. ; 114:2, s. 143-151
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Tidskriftsartikel (refereegranskat)abstract
- Animal color signals may function as indicators of fighting ability when males compete for access to females. This allows opponents to settle aggressive interactions before they escalate into physical combat and injury. Thus, there may be strong directional selection on these traits, toward enhanced signal quality. This renders sexually selected traits particularly susceptible to inbreeding depression, due to relatively low ratios of additive genetic variance to dominance variance. We measured the effects of inbreeding on an intrasexually selected color signal (the badge) in a population of Swedish sand lizards (Lacerta agilis) using the Rhh software based on 17 to 21 microsatellites. Males of this sexually dichromatic species use the badge during aggressive interactions to display, and assess, fighting ability. We found negative effects of homozygosity on badge size, saturation, and brightness. However, no such effects were observed on color hue. Pairwise correlations between badge size, hue, and saturation were all statistically significant. Thus, the sand lizard "badge" is a multicomponent signal with variation explained by covariation in badge size, saturation, and color hue. Body mass corrected for skeletal size (body condition) positively predicted badge size and saturation, encouraging future research on the extent that sexual signals may convey information on multigene targets (i.e. "genic capture").
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| 2. |
- Day, L. B., et al.
(författare)
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Correlated Evolution of Acrobatic Display and Both Neural and Somatic Phenotypic Traits in Manakins (Pipridae)
- 2021
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Ingår i: Integrative and Comparative Biology. - : Oxford University Press (OUP). - 1540-7063 .- 1557-7023. ; 61:4, s. 1343-1362
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Tidskriftsartikel (refereegranskat)abstract
- Brightly colored manakin (Ayes: Pipridae) males are known for performing acrobatic displays punctuated by non-vocal sounds (sonations) in order to attract dull colored females. The complexity of the display sequence and assortment of display elements involved (e.g., sonations, acrobatic maneuvers, and cooperative performances) varies considerably across manakin species. Species-specific display elements coevolve with display-distinct specializations of the neuroanatomical, muscular, endocrine, cardiovascular, and skeletal systems in the handful of species studied. Conducting a broader comparative study, we previously found positive associations between display complexity and both brain mass and body mass across eight manakin genera, indicating selection for neural and somatic expansion to accommodate display elaboration. Whether this gross morphological variation is due to overall brain and body mass expansion (concerted evolution) versus size increases in only functionally relevant brain regions and growth of particular body ("somatic") features (mosaic evolution) remains to be explored. Here, we test the hypothesis that cross-species variation in male brain mass and body mass is driven by mosaic evolution. We predicted positive associations between display complexity and variation in the volume of the cerebellum and sensorimotor arcopallium, brain regions which have roles in sensorimotor processes, and learning and performance of precisely timed and sequenced thoughts and movements, respectively. In contrast, we predicted no associations between the volume of a limbic arcopallial nucleus or a visual thalamic nudeus and display complexity as these regions have no-specific functional relationship to display behavior. For somatic features, we predicted that the relationship between body mass and complexity would not include contributions of tarsus length based on a recent study suggesting selection on tarsus length is less labile than body mass. We tested our hypotheses in males from 12 manakin species and a closely related flycatcher. Our analyses support mosaic evolution of neural and somatic features functionally relevant to display and indicate that sexual selection for acrobatic complexity increases the capacity for procedural learning via cerebellar enlargement and may decrease maneuverability via increases in tarsus length.
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| 3. |
- Friscia, A., et al.
(författare)
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Adaptive Evolution of a Derived Radius Morphology in Manakins (Aves, Pipridae) to Support Acrobatic Display Behavior
- 2016
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Ingår i: Journal of Morphology. - : Wiley. - 0362-2525. ; 277:6, s. 766-775
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of the avian skeleton is often studied in the context of adaptations for powered flight. The effects of other evolutionary forces, such as sexual selection, on avian skeletal design are unclear, even though birds produce diverse behaviors that undoubtedly require a variety of osteological modifications. Here, we investigate this issue in a family of passerine birds called manakins (Pipridae), which have evolved physically unusual and elaborate courtship displays. We report that, in species within the genus Manacus, the shaft of the radius is heavily flattened and shows substantial solidification. Past work anecdotally notes this morphology and attributes it to the species' ability to hit their wings together above their heads to produce loud mechanical sonations. Our results show that this feature is unique to Manacus compared to the other species in our study, including a variety of taxa that produce other sonations through alternate wing mechanisms. At the same time, our data reveal striking similarities across species in total radius volume and solidification. Together, this suggests that supposedly adaptive alterations in radial morphology occur within a conserved framework of a set radius volume and solidness, which in turn is likely determined by natural selection. Further allometric analyses imply that the radius is less constrained by body size and the structural demands that underlie powered flight, compared to other forelimb bones that are mostly unmodified across taxa. These results are consistent with the idea that the radius is more susceptible to selective modification by sexual selection. Overall, this study provides some of the first insight into the osteological evolution of passerine birds, as well as the way in which opposing selective forces can shape skeletal design in these species. (C) 2016 Wiley Periodicals, Inc.
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| 4. |
- Fuxjager, M. J., et al.
(författare)
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Evolutionary patterns of adaptive acrobatics and physical performance predict expression profiles of androgen receptor - but not oestrogen receptor - in the forelimb musculature
- 2015
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 29:9, s. 1197-1208
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Tidskriftsartikel (refereegranskat)abstract
- Superior physical competence is vital to the adaptive behavioural routines of many animals, particularly those that engage in elaborate sociosexual displays. How such traits evolve across species remains unclear. Recent work suggests that activation of sex steroid receptors in neuromuscular systems is necessary for the fine motor skills needed to execute physically elaborate displays. Thus, using passerine birds as models, we test whether interspecific variation in display complexity predicts species differences in the abundance of androgen and oestrogen receptors (AR and ER-) expressed in the forelimb musculature and spinal cord. We find that small-scale evolutionary patterns in physical display complexity positively predict expression of AR in the main muscles that lift and retract the wings. No such relationship is detected in the spinal cord, and we do not find a correlation between display behaviour and neuromuscular expression of ER-. Also, we find that AR expression levels in different androgen targets throughout the body - namely the wing muscles, spinal cord and testes - are not necessarily correlated, providing evidence that evolutionary forces drive AR expression in a tissue-specific manner. These results suggest co-evolution between the physical prowess necessary for display performance and levels of AR expression in avian forelimb muscles. Moreover, this relationship appears to be both specific to muscle and AR-mediated signalling. Given that prior work suggests that activation of muscular AR is a necessary component of physical display performance, our current data support the hypothesis that sexual selection shapes levels of AR expressed in the forelimb skeletal muscles to help drive the evolution of adaptive motor abilities.
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| 5. |
- Hansson, Alexander, et al.
(författare)
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Context-dependent thermolability of sex determination in a lacertid lizard with heteromorphic sex chromosomes
- 2023
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Ingår i: Biology Open. - 2046-6390. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- Developmental conditions can profoundly impact key life history traits of the individual. In cases where offspring sex is driven by developmental reaction norms, permanent changes to the phenotype can fundamentally alter life history trajectories. Sex determination mechanisms in reptiles are remarkably diverse, including well-characterised genetic and temperature-dependent sex determination. In rarer, but increasingly more commonly documented cases, sex can also be determined by a combination of the two, with temperature overriding the genetically determined sex. Thus, sex-by-temperature interactions is a mechanism that can be contextually labile, where reaction norms of sex against developmental environment might only be observable under certain conditions. We examine the effects of incubation temperature on hatchling sex in an oviparous lizard with clearly defined heteromorphic sex chromosomes presumed to determine sex solely on a genetic basis. We also test the repeatability of our results by replicating incubation experiments across 3 years. We show that warmer temperatures may override chromosomal sex and cause an overproduction of daughters. However, this effect was inconsistent among years, with high temperature only resulting in a daughter-significant bias in one year. Warm-incubated daughters were more efficient at converting yolk into tissue, which would allow for greater resource allocation to other fitness-related processes, such as growth. This suggests that thermolabile sex determination could be a trait under selection. More energy-efficient embryos also produced faster-growing offspring, suggesting that energy utilization patterns of the embryo were maintained into the juvenile stage, which could have important implications for the ontogenetic development and evolution of life histories.
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| 6. |
- Lindsay, Willow, 1980, et al.
(författare)
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Acrobatic Courtship Display Coevolves with Brain Size in Manakins (Pipridae)
- 2015
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Ingår i: Brain, behavior, and evolution. - : S. Karger AG. - 0006-8977 .- 1421-9743. ; 85:1, s. 29-36
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Tidskriftsartikel (refereegranskat)abstract
- Acrobatic display behaviour is sexually selected in manakins (Pipridae) and can place high demands on many neural systems. Manakin displays vary across species in terms of behavioural complexity, differing in number of unique motor elements, production of mechanical sounds, cooperation between displaying males, and construction of the display site. Historically, research emphasis has been placed on neurological specializations for vocal aspects of courtship, and less is known about the control of physical, non-vocal displays. By examining brain evolution in relation to extreme acrobatic feats such as manakin displays, we can vastly expand our knowledge of how sexual selection acts on motor behaviour. We tested the hypothesis that sexual selection for complex motor displays has selected for larger brains across the Pipridae. We found that display complexity positively predicts relative brain weight (adjusted for body size) after controlling for phylogeny in 12 manakin species and a closely related flycatcher. This evidence suggests that brain size has evolved in response to sexual selection to facilitate aspects of display such as motor, sensorimotor, perceptual, and cognitive abilities. We show, for the first time, that sexual selection for acrobatic motor behaviour can drive brain size evolution in avian species and, in particular, a family of suboscine birds. (C) 2015 S. Karger AG, Basel
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| 7. |
- Lindsay, Willow, 1980, et al.
(författare)
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Corticosterone: a costly mediator of signal honesty in sand lizards
- 2016
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 6:20, s. 7451-7461
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms underlying honest signal expression remain elusive and may involve the integration of social and physiological costs. Corticosterone is a socially modulated metabolic hormone that mediates energy investment and behavior and may therefore function to deter dishonest signal expression. We examined the relationship between corticosterone and green badge coloration in male sand lizards (Lacerta agilis), hypothesizing that physiological and behavioral costs resulting from elevated baseline glucocorticoids function in maintenance of honest signal expression. We found that large-badged males had higher corticosterone titer, with this relationship apparent at the end of the season and absent early in the season. Large-badged males also suffered higher ectoparasite load (number of tick nymphs), despite being in better condition than small-badged males. Ectoparasite load was positively related to corticosterone titer early in the season at the time of badge formation. High-condition individuals had lower corticosterone and lower numbers of ectoparasites than low-condition individuals, suggestive of conditional variation in ability to withstand costs of corticosterone. We found an opposing negative relationship between corticosterone titer and endoparasite load. Corticosterone titer was also negatively associated with male mobility, a fitness-determining behavior in this species. Because badge size is involved in mediating agonistic social interactions in this species, our results suggest that badge-dependent variation in corticosterone is likely reflective of variation in social conditions experienced over the course of the season. Our results implicate corticosterone in maintenance of signal honesty, both early in the season through enforcement of physiological costs (ectoparasite load) and during the season through behavioral costs (male mobility). We propose that socially modulated variation in corticosterone critically functions in mediation of signal honesty without requiring a direct role for corticosterone in trait expression.
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| 8. |
- Lindsay, Willow, 1980, et al.
(författare)
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Endless forms of sexual selection
- 2019
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Ingår i: PeerJ. - : PeerJ. - 2167-8359. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, the field of sexual selection has exploded, with advances in theoretical and empirical research complementing each other in exciting ways. This perspective piece is the product of a "stock-taking'' workshop on sexual selection and sexual conflict. Our aim is to identify and deliberate on outstanding questions and to stimulate discussion rather than provide a comprehensive overview of the entire field. These questions are organized into four thematic sections we deem essential to the field. First we focus on the evolution of mate choice and mating systems. Variation in mate quality can generate both competition and choice in the opposite sex, with implications for the evolution of mating systems. Limitations on mate choice may dictate the importance of direct vs. indirect benefits in mating decisions and consequently, mating systems, especially with regard to polyandry. Second, we focus on how sender and receiver mechanisms shape signal design. Mediation of honest signal content likely depends on integration of temporally variable social and physiological costs that are challenging to measure. We view the neuroethology of sensory and cognitive receiver biases as the main key to signal form and the 'aesthetic sense' proposed by Darwin. Since a receiver bias is sufficient to both initiate and drive ornament or armament exaggeration, without a genetically correlated or even coevolving receiver, this may be the appropriate 'null model' of sexual selection. Thirdly, we focus on the genetic architecture of sexually selected traits. Despite advances in modern molecular techniques, the number and identity of genes underlying performance, display and secondary sexual traits remains largely unknown. In-depth investigations into the genetic basis of sexual dimorphism in the context of long-term field studies will reveal constraints and trajectories of sexually selected trait evolution. Finally, we focus on sexual selection and conflict as drivers of speciation. Population divergence and speciation are often influenced by an interplay between sexual and natural selection. The extent to which sexual selection promotes or counteracts population divergence may vary depending on the genetic architecture of traits as well as the covariance between mating competition and local adaptation. Additionally, post-copulatory processes, such as selection against heterospecific sperm, may influence the importance of sexual selection in speciation. We propose that efforts to resolve these four themes can catalyze conceptual progress in the field of sexual selection, and we offer potential avenues of research to advance this progress.
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| 9. |
- Lindsay, Willow, 1980, et al.
(författare)
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Long term effects of outbreeding: experimental founding of island population eliminates malformations and improves hatching success in sand lizards
- 2020
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207. ; 249
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Tidskriftsartikel (refereegranskat)abstract
- Loss of genetic variation is an increasing problem in many natural populations as a result of population fragmentation, inbreeding, and genetic drift, which may lead to inbreeding depression and subsequent "extinction vortices". In such cases, outbreeding offers a potential population saviour from extinction. Here we compare offspring viability between an experimentally founded outbred island population of sand lizards Lacerta agilis, and an inbred mainland source population on the Swedish West coast. We have studied the mainland population for over a decade during which > 4000 offspring from > 500 parents were monitored. We conducted an outbreeding experiment in which lizards from the mainland population with relatively low genetic variation were crossbred with lizards from distant populations that lack gene flow. The resulting 454 offspring were introduced to an otherwise uninhabited island with ideal sand lizard habitat. A survey of the island two decades later showed that offspring produced by females from the experimentally founded population had 13% higher hatching success (99.3% versus 86.4%) and elimination of the malformations occurring in 21% of clutches in the mainland source population. These results co-occur with higher genetic diversity. We conclude that outbreeding improved offspring viability in our island population ca 5-6 generations after the founding event, that is, with sustained viability effects at a time when heterotic effects are expected to have subsided.
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| 10. |
- Lindsay, Willow, 1980, et al.
(författare)
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Quantitative genetics of breeding coloration in sand lizards; genic capture unlikely to maintain additive genetic variance
- 2023
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540.
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Tidskriftsartikel (refereegranskat)abstract
- Sexual selection on fitness-determining traits should theoretically erode genetic variance and lead to low heritability. However, many sexually selected traits maintain significant phenotypic and additive genetic variance, with explanations for this "lek paradox" including genic capture due to condition-dependence, and breaks on directional selection due to environmental sources of variance including maternal effects. Here we investigate genetic and environmental sources of variance in the intrasexually selected green badge of the sand lizard (Lacerta agilis). The badge functions as a cue to male fighting ability in this species, and male-male interactions determine mate acquisition. Using animal models on a pedigree including three generations of males measured over an extensive 9-year field study, we partition phenotypic variance in both badge size and body condition into additive genetic, maternal, and permanent environmental effects experienced by an individual over its lifespan. Heritability of badge size was 0.33 with a significant estimate of underlying additive genetic variance. Body condition was strongly environmentally determined in this species and did not show either significant additive genetic variance or heritability. Neither badge size nor body condition was responsive to maternal effects. We propose that the lack of additive genetic variance and heritability of body condition makes it unlikely that genic capture mechanisms maintain additive genetic variance for badge size. That said, genic capture was originally proposed for male traits under female choice, not agonistic selection. If developmental pathways generating variance in body condition, and/or the covarying secondary sex trait, differ between inter- and intrasexual selection, or the rate at which their additive genetic variance or covariance is depleted, future work may show whether genic capture is largely restricted to intersexual selection processes.
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