The manifestation and significance of sexual dimorphism in anguid lizards: a case study of Barisia monticola

1989 ◽  
Vol 67 (1) ◽  
pp. 68-72 ◽  
Author(s):  
James L. Vial ◽  
James R. Stewart
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Reproductive Behavior ◽  
Reproductive Potential ◽  
Head Size ◽  
Adult Males ◽  
Allometric Growth ◽  
Natural And Sexual Selection ◽  
Dimorphic Expression

The dimorphic expression of body size, body – head size relationships, and chromatic characters among anguid lizards is reviewed. These characteristics are quantitatively examined in a population of Barisia monticola. No sexual differences are found in body size. Head size is positively correlated with body size; however, allometric growth rates in head size are significantly greater in adult males than in females or juveniles. Adult males also differ significantly in eight of nine chromatic characters, the most pronounced being the presence of light dorsal scale markings. These differences are explored in the context of both natural and sexual selection. We hypothesize that the absence of dimorphism in overall body size is the result of natural selection operating to maximize female reproductive potential. In contrast, we predict that dimorphism expressed in body – head size relationships and dichromatism are consequences of sexual selection relating to agonistic and reproductive behavior of males.

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.

Etologia ecologico-evolutiva a amfibienilor: sinteza conceptuala a rezultatelor investigatiilor la nivel regional si european

2019 ◽  
Author(s):  
Tudor Cozari ◽  
Keyword(s):  
Sexual Selection ◽  
Reproductive Behavior ◽  
Reproductive Strategies ◽  
Reproductive Potential ◽  
Ambient Conditions ◽  
Republic Of Moldova ◽  
Parental Contribution ◽  
The Republic ◽  
First Time ◽  
Fundamental Mechanism

Following from long investigations of more than 50 populations of amphibians from the Republic of Moldova and Italy were elucidated ecological particularities and evolutionary reproductive behavior of some species of Caudata and Anura Orders. For the first time, on Autecological & Sinecological level, has been made assessment of nuptial systems of amphibians – of parental contribution, reproductive success, „r” & „K” reproductive strategies and their role in sexual selection and evolution the attainment of reproductive potential as a fundamental mechanism of survival of amphibian populations in various ambient conditions.

The evolution of sexual dimorphism in the skink Eumeces laticeps: an example of sexual selection

1985 ◽  
Vol 63 (5) ◽  
pp. 995-1002 ◽  
Author(s):  
Laurie J. Vitt ◽  
William E. Cooper Jr.
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Breeding Season ◽  
Prey Size ◽  
Maximum Size ◽  
Head Size ◽  
Sexually Dimorphic ◽  
Eumeces Laticeps ◽  
Aggressive Male ◽  
The Mean

Adults of the skink Eumeces laticeps are sexually dimorphic in coloration, body size, head size, and relative head size. Males have larger heads at a given body size than females and the divergence in relative head size is coincident with the size at which sexual maturity is reached. Although there were no differences between sexes in tail loss frequencies, there were substantial differences in frequencies of body and head scars, a consequence of aggressive male–male interactions. Prey size was correlated with body and head size and males tended to eat larger prey items than females. However, both sexes are capable of eating prey much larger than the mean or maximum size of prey found in stomachs, suggesting that resource partitioning is a consequence of sexual size differences rather than a cause. The heads of males at a given body size increase during the breeding season, and a combination of head and body size apparently determines the outcome of intrasexual aggressive encounters. Moreover, small males were never observed with females during the breeding season, and those males observed "guarding" females were significantly larger than males observed in the absence of females. We conclude that sexual selection accounts for many of the differences in morphological traits between sexes of E. laticeps.

Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus

1993 ◽  
Vol 71 (9) ◽  
pp. 1715-1723 ◽  
Author(s):  
P. le F. N. Mouton ◽  
J. H. van Wyk
Keyword(s):  
Sexual Dimorphism ◽  
Reproductive Activity ◽  
Energy Allocation ◽  
Head Size ◽  
Adult Males ◽  
Altitudinal Variation ◽  
Female Head ◽  
Basic Colour ◽  
Epidermal Glands

In a high-altitude population of the Drakensberg crag lizard, Pseudocordylus melanotus, most adult males, unlike adult females, are brightly coloured, and they are larger in body size and have relatively larger heads than females. Three basic colour phases can be distinguished among the brightly coloured adult males. No apparent differences in reproductive activity, number and differentiation state of the generation glands and femoral pores, or scar frequency were noted among the three colour phases. In males the development of bright colours and the differentiation of the epidermal glands coincide with the onset of sexual maturity. Sexual dimorphism in head size of adults is due to a decrease in female head size relative to juvenile head size as well as an increase in relative head size of males. Preliminary data indicate a social structure of territorial polygyny in P. melanotus and suggest that the dimorphism can partly be ascribed to sexual selection. There are also, however, indications of altitudinal variation in the expression of sexual dimorphism, which may be explained in terms of differential energy allocation by females at different altitudes.

scholarly journals Relative growth, sexual maturity and handedness in the ghost shrimp Callichirus major (Decapoda: Callianassidae) from the southwestern Atlantic

2019 ◽  
Vol 83 (2) ◽  
pp. 167 ◽  
Author(s):  
Juliana Priscila Piva Rio ◽  
Patricio Hernáez ◽  
Marcelo Antonio Amaro Pinheiro
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Sexual Maturity ◽  
Adult Males ◽  
Allometric Growth ◽  
Growth Phases ◽  
Relative Growth ◽  
Ghost Shrimp ◽  
Living Organisms ◽  
Main Growth

Biometric studies provide valuable information about changes associated with the growth and sexual maturity of living organisms. We analysed sexual dimorphism, allometric growth, sexual maturity and handedness in the ghost shrimp Callichirus major at Gonzaga beach, Brazil, where the catches of this species have been prohibited since 1992. To this end, a total of 544 individuals of C. major were collected during 12 months of sampling. Males were significantly smaller than females, denoting sexual dimorphism with respect to body size. The analysis of allometric growth between chelar carpus length and carapace length (CL) revealed a positive allometric relationship in juveniles of both sexes and adult males, but a negative allometry in adult females. Overall, our results showed the existence of two main growth phases related to sexual maturity, with a similar transition point for males (15.0 mm CL) and females (16.0 mm CL). Heterochely and homochely were registered in shrimp from both sexes, but in males heterochely occurred to a higher degree and was predominant (86.9%), whereas in females homochely was slightly more frequent (59.3%). The consequences of sexual dimorphism in terms of body size and chelipeds in the mating system of C. major are discussed in this study.

scholarly journals Massive, solidified bone in the wing of a volant courting bird

2012 ◽  
Vol 8 (5) ◽  
pp. 760-763 ◽  
Author(s):  
Kimberly S. Bostwick ◽  
Mark L. Riccio ◽  
Julian M. Humphries
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
High Resolution ◽  
Flexural Strength ◽  
Sound Production ◽  
Long Bones ◽  
Adult Males ◽  
Terrestrial Vertebrates ◽  
Strength And Stiffness ◽  
Courtship Displays

One pervasive morphological feature of tetrapods is the pipe-like, often marrow-filled, structure of the limb or long bones. This ‘hollow’ form maximizes flexural strength and stiffness with the minimum amount of bony material, and is exemplified by truly hollow (air-filled), or pneumatic, humeri in many modern birds. High-resolution microCT scans of the wings of two male club-winged manakins ( Machaeropterus deliciosus ) uncovered a notable exception to the hollow-tube rule in terrestrial vertebrates; males exhibited solidified ulnae more than three times the volume of birds of comparable body size, with significantly higher tissue mineral densities. The humeri exhibited similar (but less extreme) modifications. Each of the observed osteological modifications increases the overall mass of the bone, running counter to pervasive weight-reducing optimizations for flight in birds. The club-winged manakin is named for a pair of unique wing feathers found in adult males; these enlarged feathers attach directly to the ulna and resonate to produce a distinctive sound used in courtship displays. Given that the observed modifications probably assist in sound production, the club-winged manakin represents a case in which sexual selection by female choice has generated an ecologically ‘costly’ forelimb morphology, unique in being specialized for sound production at a presumed cost in flight efficiency.

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