Cryptic sexual dimorphism reveals differing selection pressures on continental islands

Biotropica ◽  
2020 ◽  
Author(s):  
Fionn Ó Marcaigh ◽  
David J. Kelly ◽  
Kangkuso Analuddin ◽  
Adi Karya ◽  
Naomi Lawless ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Selection Pressures ◽  
Continental Islands

Sexual dimorphism in the antennae of terrestrial isopods: a result of male contests or scramble competition?

2000 ◽  
Vol 78 (11) ◽  
pp. 1987-1993 ◽  
Author(s):  
F Lefebvre ◽  
M Limousin ◽  
Y Caubet
Keyword(s):  
Sexual Dimorphism ◽  
Negative Correlation ◽  
Morphological Analysis ◽  
Scramble Competition ◽  
Behavioral Analysis ◽  
Sexually Dimorphic ◽  
Selection Pressures ◽  
Terrestrial Isopods ◽  
Male Contests

In Oniscidea (terrestrial crustaceans), males are known to have longer antennae than females. This sexual dimorphism may result from a variety of selection pressures. However, some species are well known for their highly aggressive males, which use their antennae as weapons. We tested the hypothesis that longer antennae in males have been selected for by means of antennal contests. Morphological analysis of the antennae and behavioral analysis of male dyads were performed in parallel on 7 species. We demonstrate significant sexual dimorphism of the antennae in 6 of the 7 species, and various forms of male aggressiveness depending on the species. Our hypothesis was rejected because we found a negative correlation between the use of the antennae in contests and the magnitude of sexual dimorphism. Furthermore, some species are sexually dimorphic but the males never compete using their antennae. We propose and argue that scramble competition to be the first to find receptive females could explain why males have longer chemoreceptive antennae.

scholarly journals Phenotypic Variation in Skull Size and Shape Between Newfoundland and Mainland Populations of North American Black Bears, Ursus americanus

2003 ◽  
Vol 117 (2) ◽  
pp. 236 ◽  
Author(s):  
John A. Virgl ◽  
Shane P. Mahoney ◽  
Kim Mawhinney
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Ursus Americanus ◽  
Population Variation ◽  
Black Bears ◽  
Selection Pressures ◽  
Skull Shape ◽  
Skull Size ◽  
Environmental Selection ◽  
Gape Size

It is well recognized that differences in environmental selection pressures among populations can generate phenotypic divergence in a suite of morphological characteristics and associated life history traits. Previous analysis of mitochondrial DNA and body size have suggested that Black Bears (Ursus americanus) inhabiting the island of Newfoundland represent a different subspecies or ecotype from mainland populations. Assuming that body size covaries positively with skull size, we predicted that skull size would be greater for bears on the island than the mainland, and the distribution of size-related shape components in multivariate space should show a distinct separation between Newfoundland and mainland populations. Measurements of 1080 specimens from Newfoundland, Alberta, New York, and Quebec did not provide unequivocal support for our prediction that skull size in Newfoundland bears would be larger than bears from the mainland populations. After removing ontogenetic effects of skull size, between-population variation in skull shape was greater in females than males, and the analysis significantly separated Newfoundland bears from mainland populations. Explanations for this pattern are numerous, but currently remain hypothetical. Limited covariation between skull size and body size suggests that genetic traits regulating the size of Black Bear skulls are more heritable (i.e., less influenced by environmental selection pressures) than characteristics affecting body size. We hypothesize that if gape size does not limit prey size in solitary terrestrial carnivores, large degrees of among-population variation in body size should be coupled with little covariation in skull size. In general, sexual dimorphism in skull size and shape was marginal for the phenotypic characters measured in our study. We believe that sexual dimorphism in skull size in Black Bears is primarily driven by intrasexual selection in males for increased gape size display, while similarity in skull shape between sexes is associated with the constraints of a temporally-selective, but similar diet.

Latitudinal variation in sexual dimorphism in a freshwater fish group

2020 ◽  
Vol 131 (4) ◽  
pp. 898-908
Author(s):  
Bayu K A Sumarto ◽  
Hirozumi Kobayashi ◽  
Ryo Kakioka ◽  
Rieko Tanaka ◽  
Ken Maeda ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Freshwater Fish ◽  
Generalized Least Squares ◽  
Latitudinal Variation ◽  
Lower Latitude ◽  
Tropical Species ◽  
Ancestral State ◽  
Selection Pressures ◽  
Fish Family

Abstract Tropical animals are characterized by showy ornaments and conspicuous body colours as compared with their temperate relatives. Some recent studies have hypothesized that sexual selection pressures are stronger in the tropics than in the temperate zone. Although negative correlations between latitude and the degree of sexual dimorphism would support this hypothesis, phylogeny should be taken into account in such comparative studies. Comparisons of the degree of sexual dimorphism in body size and fin lengths among species of the Adrianichthyidae, a freshwater fish family having a wide geographical range throughout Southeast and East Asia, revealed that lower latitude species are sexually more dimorphic in all characters than higher latitude species. Phylogenetic generalized least squares analyses using a mitochondrial DNA phylogeny demonstrated that the negative correlations between latitude and the degree of sexual dimorphism become non-significant when phylogeny is considered, but that the variance in the degree of sexual dimorphism is explained not only by phylogeny but also almost equally by latitude. Ancestral state reconstruction indicated that sexual dimorphisms have evolved independently even within major clades. These findings are consistent with the view that tropical species are exposed to stronger sexual selection pressures than temperate species. We discuss possible causes of the latitudinal variation in sexual selection pressure.

scholarly journals Parental Investment and Sexual Dimorphism in Digger Wasps (Hymenoptera: Sphecidae)

1981 ◽  
Vol 5 ◽  
pp. 58-63
Author(s):  
Howard Evans ◽  
Kevin O'Neill
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Reproductive Success ◽  
Parental Investment ◽  
Mating Success ◽  
Female Body ◽  
Intrasexual Competition ◽  
Mating Strategy ◽  
Selection Pressures ◽  
Female Body Size

While investigating the mating strategy of wasps in the genus Philanthus we have discovered that the major determinant of mating success in males is body size (i.e., larger males are more successful at obtaining matings; this will be summarized further at the end of this report). In vertebrates that display sexual dimorphism and where there is male-male combat involved in the mating strategy, males are usually the larger sex. This is not the case in the Sphecidae where, in the vast majority of species (including Philanthus), the males are smaller, on the average, than females. This is puzzling, given the superiority of larger males in intrasexual competition. Even though larger males show a higher reproductive success than smaller males, there must be stronger selection pressures acting on female body size which promotes larger size in most species of digger wasps.

The bottleneck may be the solution, not the problem

2016 ◽  
Vol 39 ◽  
Author(s):  
Arnon Lotem ◽  
Oren Kolodny ◽  
Joseph Y. Halpern ◽  
Luca Onnis ◽  
Shimon Edelman
Keyword(s):  
Working Memory ◽  
Language Acquisition ◽  
Recent Theory ◽  
Cognitive Mechanisms ◽  
Selection Pressures ◽  
Biological Trait ◽  
Memory Bottleneck

AbstractAs a highly consequential biological trait, a memory “bottleneck” cannot escape selection pressures. It must therefore co-evolve with other cognitive mechanisms rather than act as an independent constraint. Recent theory and an implemented model of language acquisition suggest that a limit on working memory may evolve to help learning. Furthermore, it need not hamper the use of language for communication.

RHYNCHOLITES AND THE PROBLEM OF NARROW AND BROAD CONCEPTION OF TAXONS

2018 ◽  
pp. 12-17 ◽  
Author(s):  
I. R. Khuzina ◽  
V. N. Komarov
Keyword(s):  
Sexual Dimorphism ◽  
Morphological Characteristics ◽  
Mass Scale ◽  
Individual Variability ◽  
Point Of View ◽  
The Other ◽  
New Taxon ◽  
Artificial System ◽  
Broad Understanding

The paper considers a point of view, based on the conception of the broad understanding of taxons. According to this point of view, rhyncholites of the subgenus Dentatobeccus and Microbeccus are accepted to be synonymous with the genus Rhynchoteuthis, and subgenus Romanovichella is considered to be synonymous with the genus Palaeoteuthis. The criteria, exercising influence on the different approaches to the classification of rhyncholites, have been analyzed (such as age and individual variability, sexual dimorphism, pathological and teratological features, degree of disintegration of material), underestimation of which can lead to inaccuracy. Divestment of the subgenuses Dentatobeccus, Microbeccus and Romanovichella, possessing very bright morphological characteristics, to have an independent status and denomination to their synonyms, has been noted to be unjustified. An artificial system (any suggested variant) with all its minuses is a single probable system for rhyncholites. The main criteria, minimizing its negative sides and proving the separation of the new taxon, is an available mass-scale material. The narrow understanding of the genus, used in sensible limits, has been underlined to simplify the problem of the passing the view about the genus to the other investigators and recognition of rhyncholites for the practical tasks.

Observation on the breeding biology of Polypedates teraiensis (Dubois, 1987) (Amphibia: Rhacophoridae)

2017 ◽  
Vol 17 (1) ◽  
pp. 25-32
Author(s):  
Jacinta Lalchhanhimi ◽  
Lalremsanga H.T.
Keyword(s):  
Sexual Dimorphism ◽  
Breeding Season ◽  
Sound Production ◽  
Reproductive Function ◽  
Breeding Biology ◽  
Tree Frog ◽  
University Campus ◽  
Morphometric Measurements ◽  
Advertisement Calls ◽  
Males And Females

The breeding biology of tree frog, Polypedates teraiensis was studied during the breeding season at Mizoram University Campus. It was found that sound production by male during the breeding season was primarily a reproductive function and advertisement calls attract females to the breeding areas and announce other males that a given territory is occupied. The aim of this study was to provide the detailed information on the breeding behaviour and the advertisement calls of Polypedates teraiensis. The morphometric measurements of the amplecting pairs (males and females) for sexual dimorphism along with clutch sizes were also studied.

Spatial expression profiling reveals tissue-specific sexual dimorphism of the natriuretic peptide system in mice

2014 ◽  
Author(s):  
Samantha Mirczuk ◽  
Camille Robson ◽  
Benjamin Robinson ◽  
Andrew Lessey ◽  
Victoria Lipscomb ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Natriuretic Peptide ◽  
Expression Profiling ◽  
Tissue Specific ◽  
Spatial Expression ◽  
Peptide System ◽  
Natriuretic Peptide System

Sexual dimorphism in the mechanisms for insulin resistance

2019 ◽  
Author(s):  
Marcia Hiriart ◽  
Myrian Velasco ◽  
Marcia Hiriart
Keyword(s):  
Insulin Resistance ◽  
Sexual Dimorphism
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