scholarly journals Sexual dimorphism in Apfelbeckia insculpta (L. Koch, 1867) (Myriapoda: Diplopoda: Callipodida)

2017 ◽  
Vol 69 (1) ◽  
pp. 23-33 ◽  
Author(s):  
Bojan Ilic ◽  
Bojan Mitic ◽  
Slobodan Makarov
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Endemic Species ◽  
Balkan Peninsula ◽  
Body Plan ◽  
Body Proportions ◽  
Adult Body ◽  
Copulation Behavior

Apfelbeckia insculpta (L. Koch, 1867) is one of the largest European millipedes and an endemic species of the Balkan Peninsula. We present data on sexual dimorphism in size and body proportions obtained from 179 adult specimens of this species from four caves in Serbia and one in Montenegro using univariate and multivariate morphometric techniques. Sexual dimorphism was apparent and female-biased for all measured characters, except for lengths of the antennae and the 24th leg pair (which were larger in males) and lengths of the first, second and fourth leg pairs, which exhibited small differences between sexes. Generally, females had significantly greater body size than males, while males expressed significantly greater values in traits that can be associated with mobility and copulation behavior. Also, we found significant variations in sexual size and body proportions dimorphism among analyzed populations. The influences of fecundity and sexual selection on the adult body plan in A. insculpta are discussed.

Factors driving sexual dimorphism and colour variability in the Achala Copper Lizard (Pristidactylus achalensis), an endemic species to the highland mountains in central Argentina

2020 ◽  
Vol 98 (6) ◽  
pp. 377-389
Author(s):  
S. Naretto ◽  
M. Chiaraviglio
Keyword(s):  
Sex Differences ◽  
Spatial Distribution ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Endemic Species ◽  
Morphological Changes ◽  
Head Size ◽  
Head Width ◽  
Temporal And Spatial Distribution ◽  
Central Argentina

The intensity of mating competition varies according to the temporal and spatial distribution of individuals. Measuring sexual dimorphism over time and interpreting the association between individuals is therefore important if we aim to understand how sexual traits are influenced. We examined sex differences in the Achala Copper Lizard (Pristidactylus achalensis (Gallardo, 1964)), an endemic species from the highest part of mountains of central Argentina. Over 4 years, we explored sex-specific variation in body size, head size, interlimb length, and body colouration. Furthermore, we evaluated how these traits varied temporally, and we also explored whether the spatial distribution of individuals is explained by variation in these traits. We found that P. achalensis is a species with sexual dimorphism in multiple characters, including body size, head size, and colouration. Interestingly, some traits related to mating, such as head width, show a temporal variability in both sexes, whereas other traits, such as colouration, varies seasonally only in males. Our results underline the intriguing possibility of seasonal morphological changes related to mating, and more broadly that sex differences are influenced by sexual selection pressures mediated by temporal variation in mate competition.

Heads or tails? Sexual dimorphism in helodermatid lizards

2007 ◽  
Vol 85 (1) ◽  
pp. 92-98 ◽  
Author(s):  
C.M. Gienger ◽  
Daniel D. Beck
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Morphological Traits ◽  
Tail Length ◽  
Repeated Sequences ◽  
Analysis Of Covariance ◽  
Head Size ◽  
Heloderma Suspectum

We tested the hypothesis that helodermatid lizards (Gila monsters, Heloderma suspectum Cope, 1869, and beaded lizards, H. horridum (Wiegmann, 1829)) show sexual dimorphism in morphological traits related to male–male agonistic behaviors. Male–male combat in helodermatid lizards involves repeated sequences of ritualized grappling. Male Gila monsters use their heads in attempts to gain or maintain a superior position during repeated combat bouts that may last for hours. Pairs of fighting male beaded lizards form spectacular body arches, with abdomens adpressed and snouts, forelimbs, and tail tips contacting the ground. We measured body size, head size, and tail length in 208 preserved H. suspectum, and body size and tail length (but not head size) in 79 live H. horridum, then tested for sexual dimorphism using analysis of covariance. Male Gila monsters had proportionately larger heads than females but did not differ in tail length or body size. Male beaded lizards had proportionately longer tails than females and were larger in body size only when the largest individuals were included in the analysis. Differences in head dimensions (in H. suspectum) and tail length (in H. horridum) are likely the result of sexual selection acting through male–male agonistic behaviors in this unique lizard taxon.

scholarly journals Morphometric differentiation and sexual dimorphism in Limnomedusa macroglossa (Duméril & Bibron, 1841) (Anura: Alsodidae) from Uruguay

2021 ◽  
Vol 16 (1) ◽  
pp. 11-25
Author(s):  
Valeria De Olivera-López ◽  
Arley Camargo ◽  
Raúl Maneyro
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Phenotypic Plasticity ◽  
Life History Strategies ◽  
Clinal Variation ◽  
Size And Shape ◽  
Secondary Sexual Characteristics ◽  
Sexual Characteristics ◽  
Morphological Differences

Intersexual morphological differences within a species occur in many traits, including body size and shape. Many processes that cause geographic variability in morphology have been proposed: population structure, phenotypic plasticity (environmental effects on development), and natural and/or sexual selection. Several hypotheses can explain patterns of sexual dimorphism in anurans, including natural or intra/inter-sexual selection, and differences in life history strategies between sexes. Limnomedusa macroglossa is considered a habitat specialist restricted to rocky outcrops in Brazil, Argentina, Paraguay, and Uruguay. We evaluated the extent of sexual (size and shape) dimorphism in L. macroglossa from Uruguay based on morphometrics and secondary sexual characteristics, while taking into account geographic variation. Sexual dimorphism in body size of adults was found, but multivariate analyses did not demonstrate the existence of significant differences in shape. There were also significant differences in body size and hind leg measurements among six hydrographic basins as a result from the phenotypic plasticity correlated with local temperature, representing a clinal variation along the latitudinal gradient of Uruguay. The sexual dimorphism found in body size is probably the consequence of higher growth rates and/or late sexual maturity in females, which favors larger body size for accommodating larger ovaries, and thus, higher reproductive output. 

Sexual dimorphism in thick-billed murres, Uria lomvia

1993 ◽  
Vol 71 (2) ◽  
pp. 346-351 ◽  
Author(s):  
Donald T. Stewart
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Discriminant Analysis ◽  
Driving Force ◽  
Mate Guarding ◽  
Canonical Discriminant Analysis ◽  
Uria Lomvia ◽  
Breeding Sites ◽  
Univariate Statistics

The pattern of sexual dimorphism in thick-billed murres, Uria lomvia, from the Lancaster Sound – Jones Sound region, Northwest Territories, was examined for weight and 21 skeletal characters. Univariate statistics (Bonferroni-corrected t-tests) indicated that males were significantly larger than females in 6 bill and skull characters. Multivariate statistics also indicated that males had larger bills and skulls than females (based on canonical discriminant analysis), but males were not larger than females in overall body size (as defined by the first principal-components axis). The direction and magnitude of dimorphism were consistent with a hypothesis based on sexual selection as the driving force. In particular, large bill and skull sizes in males are consistent with agonistic behaviours associated with male–male competition for breeding sites and mate guarding.

scholarly journals Morphological distinction and sexual dimorphism in divergent clades of Neurergus kaiseri (Amphibia: Salamandridae)

2018 ◽  
Vol 32 ◽  
pp. 5-17
Author(s):  
Hadi Khoshnamvand ◽  
Mansoureh Malekian ◽  
Yazdan Keivany
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Principle Component Analysis ◽  
Morphological Differentiation ◽  
Taxonomic Revision ◽  
Morphological Characters ◽  
Head Width ◽  
Morphological Distinction ◽  
Ecological Differences

Morphological differentiation and sexual dimorphism in the two genetically distinct clades (Northern and Southern clades) of the Lorestan newt, Neurergus kaiseri, was evaluated for 72 live specimens, using five body- and nine head-related characters and eight calculated ratios. Principle component analysis of morphological characters confirmed that the Lorestan newt populations are well separated into two distinct groups, suggesting that a taxonomic revision in N. kaiseri may be required because of significant molecular, morphological and ecological differences between these clades. Sexual dimorphism in N. kaiseri includes body size and shape. Females were clearly larger than males in most body- and head-related variables and males had relatively greater head width and eye length. Sexual dimorphism in this species may be linked to sexual selection and ecological differences between sexes. However, many aspects of the ecology and reproductive biology of this species remain unknown.

scholarly journals Sexual selection on male vocal fundamental frequency in humans and other anthropoids

2016 ◽  
Vol 283 (1829) ◽  
pp. 20152830 ◽  
Author(s):  
David A. Puts ◽  
Alexander K. Hill ◽  
Drew H. Bailey ◽  
Robert S. Walker ◽  
Drew Rendall ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Immune Function ◽  
Fundamental Frequency ◽  
Low Frequency ◽  
Evolutionary Transitions ◽  
Mating Competition ◽  
Males And Females ◽  
Low Cortisol

In many primates, including humans, the vocalizations of males and females differ dramatically, with male vocalizations and vocal anatomy often seeming to exaggerate apparent body size. These traits may be favoured by sexual selection because low-frequency male vocalizations intimidate rivals and/or attract females, but this hypothesis has not been systematically tested across primates, nor is it clear why competitors and potential mates should attend to vocalization frequencies. Here we show across anthropoids that sexual dimorphism in fundamental frequency ( F 0 ) increased during evolutionary transitions towards polygyny, and decreased during transitions towards monogamy. Surprisingly, humans exhibit greater F 0 sexual dimorphism than any other ape. We also show that low- F 0 vocalizations predict perceptions of men's dominance and attractiveness, and predict hormone profiles (low cortisol and high testosterone) related to immune function. These results suggest that low male F 0 signals condition to competitors and mates, and evolved in male anthropoids in response to the intensity of mating competition.

Differences in sexual dimorphism among four gazelle taxa (Gazella spp.) in the Middle East

2010 ◽  
Vol 60 (4) ◽  
pp. 395-412 ◽  
Author(s):  
Peter Cunningham ◽  
Martin Plath ◽  
Torsten Wronski ◽  
Mohamed Sandouka
Keyword(s):  
Body Weight ◽  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Mating Systems ◽  
Research Centre ◽  
Sexually Dimorphic ◽  
Male Sex ◽  
The Difference ◽  
Horn Development

AbstractSexual selection can lead to sexual dimorphism, where elaborated traits used in mate attraction or weaponry are more expressed in the male sex. The degree of sexual dimorphism, however, is known to vary even among closely related taxa. Here we examined sexual dimorphism in horn length and three measures related to body size (body weight, shoulder height, and neck circumference) in four gazelle taxa, representing at least three species, i.e. Dorcas gazelle (G. dorcas), Sand gazelle (G. subgutturosa marica) and Mountain gazelle (G. gazella). The latter is represented by two distinctive phenotypes maintained and bred at the King Khalid Wildlife Research Centre in Saudi Arabia. We describe marked differences in sexual dimorphism among taxa. For example, the difference in sexually dimorphic horn development was driven primarily by females exhibiting pronounced differences in horn development. We discuss how divergent mating systems, and group sizes affect these differences among the examined taxa, with more competition in larger groups probably promoting the evolution of larger horns in females, thereby leading to less sexual dimorphism.

Sexual dimorphism and evidence for intrasexual selection from quill impalements, injuries, and mate guarding in porcupines (Erethizon dorsatum)

1997 ◽  
Vol 75 (6) ◽  
pp. 847-854 ◽  
Author(s):  
Richard Alan Sweitzer ◽  
Joel Berger
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Mate Guarding ◽  
Reproductive Activity ◽  
Erethizon Dorsatum ◽  
Threshold Size ◽  
Guarding Behavior ◽  
Mating Opportunities ◽  
Foot Pad

Sexual selection is a commonly cited explanation for sexual size dimorphism. We examined patterns of sexual dimorphism in North American porcupines (Erethizon dorsatum) and used data on quill impalements, injuries, and guarding behavior to examine the intrasexual component of sexual selection among male porcupines. Results indicated that porcupines were sexually dimorphic for foot-pad length, body length, and body mass because males grew more rapidly and for longer periods than females. Quill impalements, injuries, and guarding episodes were restricted predominantly to older, larger males, intimating that only the largest porcupines were reproductively active. Regression analyses suggested that size was more important than age in predicting reproductive activity among males. Also, relatively few quill impalements and guarding episodes among younger, smaller animals suggest that there is a threshold size below which male porcupines do not attempt to compete for mate access. Although our data do not directly link larger body size in males with relatively high reproductive success, they suggest that sexual dimorphism in this species is at least partly the result of the intrasexual component of sexual selection. It is also possible that females select males on the basis of quill morphology or some other indicator of male quality. Thus, our understanding of sexual dimorphism in porcupines would benefit from additional research investigating the extent to which body size and patterns of quill number or size are advantageous to male porcupines in garnering mating opportunities and enhancing fitness.

Social behavior and sexual dimorphism in the Bonaire whiptail, Cnemidophorus murinus (Squamata: Teiidae): the role of sexual selection

2003 ◽  
Vol 81 (11) ◽  
pp. 1781-1790 ◽  
Author(s):  
Troy A Baird ◽  
Laurie J Vitt ◽  
Teresa D Baird ◽  
William E Cooper, Jr. ◽  
Janalee P Caldwell ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Sexual Dimorphism ◽  
Male Aggression ◽  
Body Dimensions ◽  
Light Blue ◽  
Ultimate Causation ◽  
Courtship Activity ◽  
Coloration Patterns

We measured body dimensions and coloration and quantified the behavior of females and males of two color phases in the Bonaire whiptail, Cnemidophorus murinus, to begin addressing the ultimate causation for sexual dimorphism in this species. Examination of size-adjusted body dimensions revealed that males have wider, longer, and deeper heads as well as somewhat longer forelegs and hind legs. Males were characterized by two distinct coloration patterns. Blue males displayed purple–blue dewlaps, blue–gray background coloration on the head and anterior torso, numerous light blue spots on the flanks, brown–orange coloration on the posterior torso, and a turquoise section on the proximal portion of the tail. By contrast, brown males were uniform olive–green to yellow–brown, with the exception of light blue spots on the lateral torso. Females were colored like brown males but lacked the blue spots. Testis length scaled with body size. Testes of only 26% of brown males were active, whereas all blue males had active testes. Blue males initiated aggressive encounters involving chases and displays directed toward other males much more frequently than females were aggressive with consexuals or with either type of male. Brown males were not observed to initiate aggression. Most blue male aggression was directed toward other blue males (70.6% of encounters), whereas 29.4% of encounters were with brown males. Blue males initiated 85.7% of the courtship encounters observed compared with only 7.1% initiated by brown males and 7.2% by females. Male-biased dimorphism in head and leg dimensions as well as coloration, together with higher rates of intrasexual aggression and courtship activity by blue males, are consistent with the hypothesis that sexual selection explains the evolution of sexual dimorphism in C. murinus.

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