Effects of food restriction on growth, energy allocation, and sexual size dimorphism in Yarrow’s Spiny Lizard, Sceloporus jarrovii

2008 ◽  
Vol 86 (4) ◽  
pp. 268-276 ◽  
Author(s):  
Robert M. Cox ◽  
Michele M. Barrett ◽  
Henry B. John-Alder
Keyword(s):  
Growth Rate ◽  
Food Restriction ◽  
Sexual Difference ◽  
Sexual Size Dimorphism ◽  
Energy Allocation ◽  
Size Dimorphism ◽  
Available Energy ◽  
Sexually Antagonistic Selection ◽  
Fat Bodies ◽  
Growth Energy

Evolutionary biologists often view sexual size dimorphism (SSD) as a fixed genetic consequence of sexually antagonistic selection, but the actual magnitude of SSD may often be strongly dependent upon proximate environmental factors. Sexual differences in growth rate lead to male-biased SSD in wild populations of Yarrow’s Spiny Lizard ( Sceloporus jarrovii Cope, 1875), yet both sexes grow at similar rates under controlled laboratory conditions. We hypothesized that male-biased SSD in S. jarrovii reflects an obligatory sexual difference in energy allocation to growth versus competing functions, but that an ad libitum diet provides an energy surplus which overwhelms this sex-specific energetic trade-off. To test this hypothesis, we reared juveniles under high (3 crickets/d) and low (1 cricket/d) food availabilities. Food restriction dramatically reduced growth in both sexes but did not differentially affect growth of females relative to males. Food consumption did not differ between sexes, but males grew slightly faster than females at both levels of food availability, indicating a greater fractional allocation of available energy to growth. By contrast, females had larger fat bodies than did males, particularly under food restriction. This sexual difference in energy allocation to storage could explain the slightly higher growth rate of males relative to females.

Sexual size dimorphism in relation to age and growth based on skeletochronological analysis in a Tibetan frog

2009 ◽  
Vol 30 (3) ◽  
pp. 351-359 ◽  
Author(s):  
Xin Lu ◽  
Xiaoyan Ma
Keyword(s):  
Growth Rate ◽  
Cross Sections ◽  
Sexual Difference ◽  
Sexual Size Dimorphism ◽  
Population Level ◽  
Age And Growth ◽  
Size Difference ◽  
Size Dimorphism ◽  
Asymptotic Size ◽  
Central Tibet

AbstractThe number of lines of arrested growth (LAGs) in diaphyseal cross-sections of phalanges or femora was used to assess individual age and growth of 612 Nanorana parkeri, including 363 males, 143 females, 70 juveniles, and 36 tadpoles, in a population from central Tibet, China. The oldest immature frogs had an age of 6 years; both the youngest sexually mature males and females were 3 years old. However, the majority of individuals bred for the first time at 5 years in males and 6 years in females. Females had greater average age (6.27 years) and lifespan (11 years) than males (5.72 and 10 years). At the population level, females, on average, were significantly larger in body length (40.3 mm) than males (37.0 mm). However, the significant size difference only occurred when both sexes were over 6 years old, at which most frogs attained maturity. Growth curve and growth rate estimated for each sex based on a von Bertalanffy model showed that females had a larger asymptotic size (54.2 mm) but smaller growth coefficient k (0.16) than males (40.0 mm, 0.37), and that females had greater growth rate than males in all age classes, except at metamorphosis. According to these results, we concluded that the sexual difference of growth between pre- and post-maturation periods contributed to the age-specific sexual size dimorphism of N. parkeri.

Sexual size dimorphism in steppe tortoises (Testudo horsfieldi): growth, maturity, and individual variation

2001 ◽  
Vol 79 (8) ◽  
pp. 1433-1441 ◽  
Author(s):  
Frédéric Lagarde ◽  
Xavier Bonnet ◽  
Brian T Henen ◽  
Johanna Corbin ◽  
Ken A Nagy ◽  
...  
Keyword(s):  
Growth Rate ◽  
Individual Variation ◽  
Sexual Difference ◽  
Sexual Size Dimorphism ◽  
Age And Growth ◽  
Size At Maturity ◽  
Size Dimorphism ◽  
Size Dependent ◽  
Complex Interactions ◽  
Size At Birth

Age and size at maturity are determined through complex interactions among size at birth, growth rate, maturation, and survival. We studied sexual size dimorphism and growth rate and maturation patterns in a long-lived organism, the steppe tortoise (Testudo horsfieldi), using the scute lamina number and width as age and growth measures. There was no sexual difference in the juvenile growth rate, but females matured later and hence were larger at maturity than males. We also observed considerable inter-individual variation in age and size at maturity. In both sexes, precocious animals grew faster during the juvenile phase but matured at a smaller body size than did tardy animals. Consequently, maturity did not seem size-dependent per se but rather was determined by growth rate. The strong variation between and within the sexes in age and size at maturity suggest that different growth trajectories and maturation schedules depend upon sex and individual responses to resource availability.

scholarly journals A skeletochronological estimate of age and growth in a large riparian frog from Madagascar (Anura, Mantellidae, Mantidactylus)

Herpetozoa ◽  
2019 ◽  
Vol 32 ◽  
pp. 39-44 ◽  
Author(s):  
Fabio M. Guarino ◽  
Angelica Crottini ◽  
Marcello Mezzasalma ◽  
Jasmin E. Randrianirina ◽  
Franco Andreone
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Sexual Size Dimorphism ◽  
The Body ◽  
Age And Growth ◽  
Growth Trajectories ◽  
Growth Coefficient ◽  
Size Dimorphism ◽  
Adult Females ◽  
Similar Growth

We characterized the body size (as snout-vent length), age, sexual size dimorphism, and growth rate in a population of one of the larger riparian frog from Madagascar (Mantidactylusgrandidieri) from a rainforest patch close to Vevembe, SE Madagascar. We identified a significant female-biased sexual size dimorphism. Age was estimated using phalangeal skeletochronology and was significantly higher in females than in males. Modal age class turned out to be 4 years in both sexes but a large percentage of adult females (75%) fell in the 5–6 years-old classes, while no male exceeded 4 years. We here report M.grandidieri as a medium-long-lived anuran species. Von Bertalanffy’s model showed similar growth trajectories between the sexes although the growth coefficient in females (k = 0.335) was slightly but not significantly higher than in males (k = 0.329).

scholarly journals Ontogenetic mechanisms underlying sexual size dimorphism in Urodele amphibians: An across-species approach

2013 ◽  
Vol 59 (1) ◽  
pp. 142-150 ◽  
Author(s):  
Lixia Zhang ◽  
Xin Lu
Keyword(s):  
Growth Rate ◽  
Body Size ◽  
Evolutionary Biology ◽  
Sexual Size Dimorphism ◽  
Demographic Data ◽  
High Growth ◽  
Annual Growth Rate ◽  
Size Dimorphism ◽  
Ontogenetic Trajectory ◽  
Delayed Maturation

Abstract Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism (SSD), only have a few been directed toward elucidating its ontogenetic basis. Urodeles are an amphibian group in which the direction and degree of SSD vary greatly among species. Using demographic data yielded by skeletochronology for 33 urodele species, the current study reveals a positive across-species correlation between SSD and the sex difference in mean age of adult animals, and the latter increases with the corresponding difference in age at maturity; annual growth rate does not differ between the sexes. We conclude that extended longevities in one sex, which is mediated by delayed maturation, would allow it to grow for longer and get larger, with growth rate making a weak contribution to body size. The sex-specific divergence in ontogenetic trajectory might be explained by potentially high growth costs of reproduction to females in association with stronger fecundity selection, and to males that are expected to experience stronger sexual selection.

Growth and sexual size dimorphism in Alberta populations of the eastern short-horned lizard, Phrynosoma douglassi brevirostre

1985 ◽  
Vol 63 (1) ◽  
pp. 139-154 ◽  
Author(s):  
G. Lawrence Powell ◽  
Anthony P. Russell
Keyword(s):  
Growth Model ◽  
Sexual Difference ◽  
Sexual Size Dimorphism ◽  
Growth Models ◽  
Tail Length ◽  
Growth Patterns ◽  
Head Width ◽  
Adult Size ◽  
Adult Males ◽  
Size Dimorphism

Alberta populations of Phrynosoma douglassi brevirostre display marked sexual size dimorphism, adult females being considerably larger than adult males. Discriminant analyses of whole mensural characters and of scaled mensural characters indicate that this dimorphism is present from birth, although it is more strongly expressed after sexual maturity. Recapture data were used to generate modified logistic by weight growth models for snout–vent length (SVL), and allometric models for each sex were generated for growth in tail length, head length, and head width. The SVL growth model for females indicates delayed maturity leading to greater adult size, an expected feature of a female viviparine. The SVL growth model for males indicates that growth ceases sooner than in females, resulting in a smaller adult size. This is possibly a result of male dispersal competition, an hypothesis further borne out by the results of a preliminary analysis of mobility in the two sexes, and may also be influenced by intersexual dietary competition. Differences in head dimensions between the sexes are a function of the differences in SVL at adulthood, but there is a significant sexual difference in the allometric relationship of tail length to SVL. No difference in the growth patterns and adult size of either sex was found to exist over the range in Alberta.

Characterization of the growth rate of adult wolffishes Anarhichas minor and A. lupus: Is avoidance of paternal care at the origin of the expression of a sexual size dimorphism?

Aquaculture ◽  
2018 ◽  
Vol 497 ◽  
pp. 24-31 ◽  
Author(s):  
Bernard-Antonin Dupont Cyr ◽  
Helge Tveiten ◽  
Grant W. Vandenberg ◽  
Pierre U. Blier ◽  
Robert L. Roy ◽  
...  
Keyword(s):  
Growth Rate ◽  
Sexual Size Dimorphism ◽  
Paternal Care ◽  
Size Dimorphism

A test of three hypotheses for latitudinal segregation of the sexes in wintering birds

1981 ◽  
Vol 59 (8) ◽  
pp. 1527-1534 ◽  
Author(s):  
J. P. Myers
Keyword(s):  
Sexual Difference ◽  
Sexual Size Dimorphism ◽  
Bird Species ◽  
Western Hemisphere ◽  
Comparative Data ◽  
Sexual Differences ◽  
Breeding Ground ◽  
Size Dimorphism ◽  
Physiological Tolerance ◽  
Location Data

Three hypotheses have been proposed to explain sexual differences in wintering latitude for different bird species: (1) intersexual behavioral dominance leads the subordinate sex to migrate farther to avoid competition; (2) intrasexual selection favors those individuals of one sex that arrive earlier and thus selects for wintering closer to the breeding ground; and (3) sexual differences in physiological tolerance allow the larger sex to survive harsher climates. Using sex, age, date, and location data from specimens collected south of the breeding range in the western hemisphere, I tested predictions of these hypotheses for two scolopacid shorebirds showing reverse sexual size dimorphism, the red phalarope, Phalaropus fulicarius, and the sanderling, Calidris alba.Neither red phalaropes nor adult sanderlings showed any sexual difference in wintering latitude. First-winter male sanderlings tended to winter farther south than first-winter females. Combined with comparative data from other species of shorebirds and passerines, these results are consistent only with hypothesis 2.

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