scholarly journals Global geographic patterns of sexual size dimorphism in birds: Support for a latitudinal trend?

2014 ◽  
Author(s):  
Nicholas R Friedman ◽  
Vladimír Remeš
Keyword(s):  
Sexual Size Dimorphism ◽  
Phylogenetic Signal ◽  
A Priori ◽  
Explanatory Power ◽  
Global Scale ◽  
Physical Geography ◽  
Size Dimorphism ◽  
The North ◽  
Sexual Selection Theory ◽  
Latitudinal Trend

Sexual size dimorphism (SSD) is widespread among animals, and is a common indication of differential selection among males and females. Sexual selection theory predicts that SSD should increase as one sex competes more fiercely for access to mates, but it is unclear what effect spatial variation in ecology may have on this behavioral process. Here, we examine SSD across the class Aves in a spatial and phylogenetic framework, and test several a priori hypotheses regarding its relationship with climate. We mapped the global distribution of SSD from published descriptions of body size, distribution, and phylogenetic relationships across 2581 species of birds. We examined correlations between SSD and nine predictor variables representing a priori models of physical geography, climate, and climate variability. Our results show guarded support for a global latitudinal trend in SSD based on a weak prevalence of species with low or female-biased SSD in the North, but substantial spatial heterogeneity. While several stronger relationships were observed between SSD and climate predictors within zoogeographical regions, no global relationship emerged that was consistent across multiple methods of analysis. While we found support for a global relationship between climate and SSD, this support lacked consistency and explanatory power. Furthermore the strong phylogenetic signal and conspicuous lack of support from phylogenetically corrected analyses suggests that any such relationship in birds is likely due to the idiosyncratic histories of different lineages. In this manner, our results broadly agree with studies in other groups, leading us to conclude that the relationship between climate and SSD is at best complex. This suggests that SSD is linked to behavioral dynamics that may at a global scale be largely independent of environmental conditions.

scholarly journals Why female birds of prey are larger than males

2020 ◽  
Vol 129 (3) ◽  
pp. 532-542
Author(s):  
Jonny Schoenjahn ◽  
Chris R Pavey ◽  
Gimme H Walter
Keyword(s):  
Sexual Size Dimorphism ◽  
A Priori ◽  
Nest Defence ◽  
Birds Of Prey ◽  
Causal Process ◽  
Size Dimorphism ◽  
Substantial Body ◽  
Key Factor ◽  
Reversed Sexual Size Dimorphism ◽  
Passionate Debate

Abstract The causes of the reversed sexual size dimorphism (RSD; females larger than males) in birds of prey are subject to a centuries-old, passionate debate. A crucial difficulty is to distinguish whether the postulated benefits derive from the proposed causal process(es) or are incidental. After reviewing the existing literature, we present a methodology that overcomes this difficulty and renders unnecessary any speculative a priori distinctions between evolved function and incidental effects. We can thus justify the following novel version of the well-known nest defence hypothesis as the most likely to explain the phenomenon in all birds of prey that show RSD: if the female predominates in actively defending the eggs and young against predators, then she is the heavier sex, and her relatively greater body mass is adaptive. That is, heavier females are favoured (independently of males) by natural selection. The attractiveness of this hypothesis is that it has the potential to explain the phenomenon in all raptors exhibiting RSD, can deal with the exceptional cases in this group, explains the direction of the dimorphism, focuses on a key factor in the reproductive success of most raptors, is parsimonious, i.e. does not require supporting hypotheses, and is supported by a substantial body of evidence.

scholarly journals Evolution of sexual size dimorphism and its relationship with sex ratio in carabid beetles of Genus Ceroglossus Solier

2013 ◽  
Vol 59 (6) ◽  
pp. 769-777 ◽  
Author(s):  
Hugo A. Benítez ◽  
Jorge Avaria-Llautureo ◽  
Cristian B. Canales-Aguirre ◽  
Viviane Jerez ◽  
Luis E. Parra ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sexual Size Dimorphism ◽  
Phylogenetic Signal ◽  
Comparative Method ◽  
Carabid Beetles ◽  
Entire Group ◽  
Geometrical Shape ◽  
Specific Level ◽  
Size Dimorphism ◽  
Morphological Studies

Abstract Although the degree of mate competition, given extreme differences in sex ratio, explains much of the pattern of male-biased size dimorphism among diverse taxa, it fails for some species which have potential for intense male competition for mates and yet exhibit little or no sexual size dimorphism (SSD). This fact suggest that species with low SSD should be express the effect of evolutionary pressure in non-obvious geometrical shape promoted by sex ratio in an evolutionary time scale. To evaluate this hypothesis we used phylogenetic comparative method in a Bayesian framework to investigate the evolution of SSD and the role of sex ratio at inter-specific level in the species of Ceroglossus (Coleoptera: Carabidae). In our results the proportion farthest from 1:1 is associated with more disparate body shape, even though the entire group has minimum variation in sex ratio, which is an intrinsic life history character of this group considering its phylogenetic conservatism or phylogenetic signal. We suggest that the sex ratio has determined the dimorphism degree during evolution of this group, since both traits have increased or decreased together during the species divergence (i.e. positive phylogenetic correlation: r2≈0.85). We suggest that morphological studies of SSD will benefit from using comparative method with Bayesian approaches to assess the effect of phylogenetic history and its uncertainty. Finally, this will be allow to researchers to quantify the uncertainty of specific evolutionary hypotheses accounting for observed sexual dimorphism patterns.

scholarly journals An evolutionary explanation of female-biased sexual size dimorphism in North Sea plaice, Pleuronectes platessa L.

2021 ◽  
Author(s):  
Fabian Mollet ◽  
Katja Enberg ◽  
David Boukal ◽  
Adriaan Rijnsdorp ◽  
Ulf Dieckmann
Keyword(s):  
North Sea ◽  
Reproductive Behavior ◽  
Sexual Size Dimorphism ◽  
Male Body ◽  
Male Mortality ◽  
Size Dimorphism ◽  
The North ◽  
Diminishing Returns ◽  
The North Sea ◽  
Energy Acquisition

Sexual size dimorphism (SSD) is caused by differences in selection pressures and life-history tradeoffs faced by males and females. Proximate causes of SSD may involve sex-specific mortality, energy acqui-sition, and energy expenditure for maintenance, reproductive tissues, and reproductive behavior. Using a quantitative, individual-based, eco-genetic model parameterized for North Sea plaice, we explore the importance of these mechanisms for female-biased SSD, under which males are smaller and reach sexual maturity earlier than females (common among fish, but also arising in arthropods and mammals). We consider two mechanisms potentially serving as ultimate causes: (1) male investments into male repro-ductive behavior might detract energy resources that would otherwise be available for somatic growth, and (2) diminishing returns on male reproductive investments might lead to reduced energy acquisition. In general, both of these can bring about smaller male body sizes. We report the following findings. First, higher investments into male reproductive behavior alone cannot explain the North Sea plaice SSD. This is because such higher reproductive investments require increased energy acquisition, which would cause a delay in maturation, leading to male-biased SSD contrary to observations. When account-ing for the observed differential (lower) male mortality, maturation is postponed even further, leading to even larger males. Second, diminishing returns on male reproductive investments alone can qualitative-ly account for the North Sea plaice SSD, even though the quantitative match is imperfect. Third, both mechanisms can be reconciled with, and thus provide a mechanistic basis for, the previously advanced Ghiselin-Reiss hypothesis, according to which smaller males will evolve if their reproductive success is dominated by scramble competition for fertilizing females, as males would consequently invest more into reproduction than growth, potentially implying lower survival rates relaxing male-male competition. Fourth, a good quantitative fit is achieved by combining both mechanisms while accounting for costs males incur during spawning.

scholarly journals Much more than a clasp: evolutionary patterns of amplexus diversity in anurans

2020 ◽  
Vol 129 (3) ◽  
pp. 652-663 ◽  
Author(s):  
Juan D Carvajal-Castro ◽  
Yelenny López-Aguirre ◽  
Ana María Ospina-L ◽  
Juan C Santos ◽  
Bibiana Rojas ◽  
...  
Keyword(s):  
Morphological Traits ◽  
Sexual Size Dimorphism ◽  
Phylogenetic Signal ◽  
Evolutionary Relationships ◽  
Behavioural Ecology ◽  
Ancestral State ◽  
Evolutionary Patterns ◽  
Evolutionary Transitions ◽  
Size Dimorphism ◽  
Reproductive Modes

Abstract The evolution and diversification of animal reproductive modes have been pivotal questions in behavioural ecology. Amphibians present the highest diversity of reproductive modes among vertebrates, involving various behavioural, physiological and morphological traits. One such feature is the amplexus, which is the clasp or embrace of males on females during reproduction and is found almost universally in anurans. Hypotheses about the origin of amplexus are limited and have not been tested thoroughly, nor have they taken into account evolutionary relationships in most comparative studies. However, these considerations are crucial to an understanding of the evolution of reproductive modes. Here, using an evolutionary framework, we reconstruct the ancestral state of amplexus in 685 anuran species. We investigate whether the type of amplexus has a strong phylogenetic signal and test whether sexual size dimorphism could have influenced amplexus type or male performance while clasping females. Overall, we found evidence of ≥34 evolutionary transitions in amplexus type across anurans. We found that amplexus type exhibits a high phylogenetic signal and that amplexus type does not evolve in association with sexual size dimorphism. We discuss the implications of our findings for the diversity of amplexus types across anurans.

scholarly journals Much more than a clasp: Evolutionary pattern of amplexus diversity in anurans

2019 ◽  
Author(s):  
Juan D. Carvajal-Castro ◽  
Yelenny López-Aguirre ◽  
Ana María Ospina-L ◽  
Juan C. Santos ◽  
Bibiana Rojas ◽  
...  
Keyword(s):  
Behavioral Ecology ◽  
Morphological Traits ◽  
Evolutionary History ◽  
Sexual Size Dimorphism ◽  
Phylogenetic Signal ◽  
Ancestral State ◽  
Evolutionary Transitions ◽  
Size Dimorphism ◽  
Evolutionary Pattern ◽  
Reproductive Modes

ABSTRACTThe evolution and diversification of animal reproductive modes have been pivotal questions in behavioral ecology. Amphibians present the highest diversity of reproductive modes among vertebrates, involving various behavioral, physiological and morphological traits. One of such features is the amplexus, the clasp or embrace of males on females during reproduction, which is almost universal to anurans. Hypotheses about the origin amplexus are limited and have not been thoroughly tested, nor had they taken into account evolutionary relationships in most comparative studies. However, these considerations are crucial to understand the evolution of reproductive modes. Here, using an evolutionary framework, we reconstruct the ancestral state of amplexus in 686 anuran species; investigate whether the amplexus type is a conserved trait; and test whether sexual size dimorphism (SSD) could have influenced the amplexus type or male performance while clasping females. Overall, we found evidence of at least 35 evolutionary transitions in amplexus type across anurans. We also found that amplexus exhibits a high phylogenetic signal (it is conserved across Anura evolutionary history) and the amplexus type does not evolve in association with SSD. We discuss the implications of our findings on the diversity of amplexus types across anurans.

Deep Learning for Autonomous Extraction of Millimeter-scale Deformation in InSAR Time Series

2021 ◽  
Author(s):  
Bertrand Rouet-Leduc ◽  
Romain Jolivet ◽  
Manon Dalaison ◽  
Paul Johnson ◽  
Claudia Hulbert
Keyword(s):  
Time Series ◽  
Ground Deformation ◽  
A Priori ◽  
Active Faults ◽  
Global Scale ◽  
Geothermal Field ◽  
The North ◽  
Atmospheric Propagation ◽  
Propagation Delays ◽  
Deformation Dynamics

<p>Systematically characterizing slip behaviours on active faults is key to unraveling the physics of tectonic faulting and the interplay between slow and fast earthquakes. Interferometric Synthetic Aperture Radar (InSAR), by enabling measurement of ground deformation at a global scale every few days, may hold the key to those interactions. <br>However, atmospheric propagation delays often exceed ground deformation of interest despite state-of-the art processing, and thus InSAR analysis requires expert interpretation and a priori knowledge of fault systems, precluding global investigations of deformation dynamics. <br>We show that a deep auto-encoder architecture tailored to untangle ground deformation from noise in InSAR time series autonomously extracts deformation signals, without prior knowledge of a fault's location or slip behaviour.<br>Applied to InSAR data over the North Anatolian Fault, our method reaches  2 mm detection, revealing a slow earthquake twice as extensive as previously recognized.<br>We further explore the generalization of our approach to inflation/deflation-induced deformation, applying the same methodology to the geothermal field of Coso, California. </p>

scholarly journals Autonomous extraction of millimeter-scale deformation in InSAR time series using deep learning

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Bertrand Rouet-Leduc ◽  
Romain Jolivet ◽  
Manon Dalaison ◽  
Paul A. Johnson ◽  
Claudia Hulbert
Keyword(s):  
Time Series ◽  
Ground Deformation ◽  
A Priori ◽  
Active Faults ◽  
Global Scale ◽  
Geothermal Field ◽  
The North ◽  
Atmospheric Propagation ◽  
Propagation Delays ◽  
Deformation Dynamics

AbstractSystematically characterizing slip behaviours on active faults is key to unraveling the physics of tectonic faulting and the interplay between slow and fast earthquakes. Interferometric Synthetic Aperture Radar (InSAR), by enabling measurement of ground deformation at a global scale every few days, may hold the key to those interactions. However, atmospheric propagation delays often exceed ground deformation of interest despite state-of-the art processing, and thus InSAR analysis requires expert interpretation and a priori knowledge of fault systems, precluding global investigations of deformation dynamics. Here, we show that a deep auto-encoder architecture tailored to untangle ground deformation from noise in InSAR time series autonomously extracts deformation signals, without prior knowledge of a fault’s location or slip behaviour. Applied to InSAR data over the North Anatolian Fault, our method reaches 2 mm detection, revealing a slow earthquake twice as extensive as previously recognized. We further explore the generalization of our approach to inflation/deflation-induced deformation, applying the same methodology to the geothermal field of Coso, California.

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