Sexual Dimorphism in Head Shape, Relative Head Width, and Body Size ofEurycea aquaticaandEurycea cirrigera

2013 ◽  
Vol 47 (2) ◽  
pp. 321-327 ◽  
Author(s):  
Michael A. Alcorn ◽  
Jennifer Deitloff ◽  
Sean P. Graham ◽  
Elizabeth K. Timpe
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Head Width ◽  
Head Shape

scholarly journals Body size, female reproduction and sexual dimorphism in the lizard Ameiva ameiva (Teiidae) in a restinga of southeastern Brazil

2008 ◽  
Vol 25 (2) ◽  
pp. 370-372 ◽  
Author(s):  
Carlos Frederico Duarte Rocha
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Clutch Size ◽  
Reproductive Period ◽  
Southeastern Brazil ◽  
Head Width ◽  
Sexually Dimorphic ◽  
Female Reproduction ◽  
Female Body Size ◽  
Reproductive Body

In this study 57 specimens of the lizard Ameiva ameiva (Linnaeus, 1758) collected in the restinga at Barra de Maricá, in the state of Rio de Janeiro, southeastern Brazil, were analyzed to investigate size relations and reproduction (in females) and sexual dimorphism of this population. We answered the following questions: 1) what is the minimum reproductive body size in females? 2) what is the average clutch size and 3) how is clutch size related to body size? 4) Are body and head sizes sexually dimorphic? Mean clutch size was 6.7 ± 2.1 eggs and was positively correlated with female body size. Sexual dimorphism favoring males was found: adult mean snout-vent length was great in males (124.2 ± 17.8 mm) than females (96.5 ± 23.1 mm SVL), and males were larger with respect to head width and length, and body mass. Thus, despite the marked seasonality at Barra de Maricá, A. ameiva has an extended reproductive period. Also, intrasexual selection may have acted on females to produce larger clutches, and on males, favoring larger males.

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.

scholarly journals Body size in tiger beetles (Coleoptera: Cicindelidae) in the south-eastern European biodiversity hotspot: sexual dimorphism and patterns of co-occurrence

2019 ◽  
Vol 2 ◽  
Author(s):  
Radomir Jaskuła ◽  
Mateusz Płóciennik ◽  
Axel Schwerk
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Habitat Preferences ◽  
Total Body Length ◽  
Head Width ◽  
Tiger Beetles ◽  
South Eastern ◽  
Reproduction Process ◽  
Similar Body ◽  
Sea Coast

In south-eastern Europe, especially in lowland areas located close to the sea coast, the diversity of Cicindelidae is one of the highest in the entire Palaearctic realm. This is both because of geological history of the region and the presence of large mosaic of habitats attractive for these beetles. As a result in the region about 25% of all Palaearctic species of tiger beetles can be found, including endemics. Many of them can be characterized by narrow or very narrow habitat preferences occurring only in one or two types of macrohabitats. In the present study sexual dimorphism of six species of tiger beetles (Calomera littoralis, C. fischeri, Cephalota circumdata, C. chiloleuca, Cylindera trisignata trisignata, Myriochila melancholica) collected along the sea coast of the Black and Mediterranean Seas was studied based on eight body parameters (right mandible length, length of head, width of head, length of pronotum, maximum pronotum width, length of elytra, maximum elytra width, and total body length.). Moreover, patterns of species co-occurrence on the basis of body size were investigated. As results we found significant sexual dimorphism indicated by larger body size of females and longer mandibles in males of the studied Cicindelidae species, what can be explained by different roles of the particular sexes in courtship (females invest much more energy in the reproduction process than males, e.g. to produce eggs or to find a good place to deposit them, as a result bigger size is much more beneficial for this sex). Moreover, we discovered that in the studied area tiger beetle species characterized by similar body size avoid each other and do not occur in the same areas.

scholarly journals An Improved Approach to Measuring Sexual Dimorphism in Snakes: Morphological Variation in the Bahamian Racer (Cubophis vudii vudii)

2020 ◽  
Vol 27 (2) ◽  
pp. 137-146
Author(s):  
Scott Johnson ◽  
William K. Hayes
Keyword(s):  
Body Size ◽  
Natural Selection ◽  
Sexual Dimorphism ◽  
Linear Models ◽  
Geometric Mean ◽  
Tail Length ◽  
Head Width ◽  
Island Populations ◽  
Total Length ◽  
New Providence

Sexual dimorphism in animals exists in many forms, including overall size difference between the sexes (sexual size dimorphism, SSD) and size and structural differences in body components (sexual body component dimor­phism, SBCD). Studies of sexual dimorphism seek to determine whether dimorphic traits result from sexual selection, natural selection, or non-adaptive processes. Characterizing sexual dimorphism depends on identifying an unbiased character for overall body size, which can then be used to assess both SSD and SBCD. Most studies of snakes use snout-vent length (SVL) for this purpose, but SVL may itself be dimorphic. In this study, we examined SSD and SBCD in three island populations of the Bahamian Racer (Cubophis vudii vudii). Discriminant function analysis (DFA) showed that head width (females wider) and tail length (males longer) best discriminated between the sexes, and total length provided the least discrimination. Linear models using total length as the least-biased measure for overall size revealed an absence of SSD, but SBCD existed for head size (width 8.9% greater in females, length similar), trunk length (4.3% longer in females), and tail length (9.8% longer in males). Linear models also revealed differences among island populations for total length (New Providence < Eleuthera = Allen Cay) and head length (Allen Cay < Eleuthera < New Providence), but not head width or tail length. Extent of SBCD varied depending on choice of character to control for overall body size, with total length yielding the most female-biased values, and geometric mean, principal component 1 (PC1) of a principal components analysis, and SVL providing increasingly more male-biased values, respectively. Body condition was statistically similar for the two sexes and three seasons (spring, summer-fall, winter), but the mod­erate and large effect sizes, respectively, suggest that females were heavier than males, and both sexes were heaviest in spring. Females, which represented 64.9 of all snakes, suffered injuries disproportionately to males (19.7% and 3.1%, respectively), but no differences in sex ratio or frequency of injury existed among the island populations. Collectively, these findings illustrate the utility of using DFA and other approaches (geometric mean, PC1) to identify a relatively unbiased reference character for overall body size and suggest that sexual and natural selection interact to shape the morphology of these snakes.

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.

Sexual dimorphism, deformations, and epibionts of Phrynops tuberosus (Testudines, Chelidae)

2015 ◽  
Vol 65 (3-4) ◽  
pp. 311-320 ◽  
Author(s):  
João Fabrício Mota Rodrigues ◽  
José Roberto Feitosa Silva
Keyword(s):  
Sexual Dimorphism ◽  
Natural History ◽  
Tail Length ◽  
Condition Index ◽  
Head Width ◽  
Body Condition Index ◽  
Future Studies ◽  
History Of ◽  
One Year ◽  
Effective Conservation

Studies focusing on the natural history of species are essential for developing effective conservation measures and evaluating ecological hypotheses. To this end, we describe natural history data of the Cotinga River toadhead turtle, Phrynops tuberosus, in the Banabuiú River in Ceará, Brazil, and evaluated sexual dimorphism, epibionts, and mutilation effects. We hand-captured 134 individuals by snorkeling, over a period of one year, resulting in the capture of 94 males, 24 females, and 16 juveniles. Females had larger head width and body mass than males, while males had longer tail length. One quarter of the turtles captured had some sort of injury or deformation, most common injuries being missing claws, mutilations, and shell deformations. We found no difference in body condition index between mutilated and non-mutilated animals. Mollusks, insects, and leeches were found as epibionts on P. tuberosus and most of the captured turtles had extensive algal cover. Future studies should focus on understanding the effect of mutilations on animal fitness and reproductive success.

Sexual dimorphism in human cranial trait scores: Effects of population, age, and body size

2014 ◽  
Vol 154 (2) ◽  
pp. 259-269 ◽  
Author(s):  
Heather M. Garvin ◽  
Sabrina B. Sholts ◽  
Laurel A. Mosca
Keyword(s):  
Body Size ◽  
Sexual Dimorphism

Body size, brain size, and sexual dimorphism in Homo naledi from the Dinaledi Chamber

2017 ◽  
Vol 111 ◽  
pp. 119-138 ◽  
Author(s):  
Heather M. Garvin ◽  
Marina C. Elliott ◽  
Lucas K. Delezene ◽  
John Hawks ◽  
Steven E. Churchill ◽  
...  
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Brain Size

scholarly journals Variation in body size of Phanocerus clavicornis Sharp, 1882 (Coleoptera: Elmidae: Larainae) in Atlantic Rainforest streams in response to hydraulic disturbance

2013 ◽  
Vol 73 (4) ◽  
pp. 747-752 ◽  
Author(s):  
MO. Segura ◽  
T. Siqueira ◽  
AA. Fonseca-Gessner
Keyword(s):  
Body Size ◽  
Total Body Length ◽  
Atlantic Rainforest ◽  
Southeastern Brazil ◽  
Head Width ◽  
High Plasticity ◽  
Larval Size ◽  
Morphometric Variation ◽  
Total Body ◽  
Rain Events

In this study, patterns of body size of Phanocerus clavicornis Sharp, 1882 (Coleoptera: Elmidae: Larainae) were investigated along a gradient of change in speed of flow conditions in streams of low order in the Atlantic Rainforest in southeastern Brazil. Specifically, the hypothesis that the distribution of P. clavicornis larvae vary in size in response to variations in the speed of flow in streams was tested. A Surber sampler was used to collect larvae from the streambed during two sampling periods, defined by the rain regime: August in the dry season and February in the rainy season. Possible differences in mean measured body size were tested by analysis of variance (ANOVA). The ANOVA result indicated for all measurements on the larvae collected in first-order streams (head width, prothoracic width and total body length), there were significant differences indicating a morphometric variation due to changing hydraulic conditions, the smallest larvae being associated with the period of greater rainfall. However, the larger streams (3rd order), where the rain events had less impact on the larval size, varied widely. The results of this study suggest that the interstitial space is important for the protection of the larvae from water flow, and that populations of P. clavicornis have high plasticity, a key feature for the occupation of unstable environments for this species. These results are important for an understanding of the life history and behavioural characteristics of the species, which allow them to persist in streams along a gradient of flow disturbance.

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