Population structure and the evolution of sexual size dimorphism and sex ratios in an insular population of Florida box turtles (Terrapene Carolina bauri)

1997 ◽  
Vol 75 (9) ◽  
pp. 1495-1507 ◽  
Author(s):  
C. Kenneth Dodd Jr.
Keyword(s):  
Sex Ratio ◽  
Sexual Size Dimorphism ◽  
Sex Ratios ◽  
Size Dimorphism ◽  
Terrapene Carolina ◽  
Key Population ◽  
Younger Age ◽  
Box Turtles ◽  
The Status ◽  
Using Data

Hypotheses in the chelonian literature suggest that in species with sexual size dimorphism, the smaller sex will mature at a smaller size and a younger age than the larger sex, sex ratios should be biased in favor of the earlier maturing sex, and deviations from a 1:1 sex ratio result from maturation of the smaller sex at a younger age. I tested these hypotheses using data collected from 1991 to 1995 on an insular (Egmont Key) population of Florida box turtles, Terrapene Carolina bauri. Contrary to predictions, the earlier maturing sex (males) grew to larger sizes than the late maturing sex. Males were significantly larger than females in mean carapace length but not mean body mass. Sex ratios were not balanced, favoring the earlier maturing sex (1.6 males: 1 female), but the sex-ratio imbalance did not result from faster maturation of the smaller sex. The imbalance in the sex ratio in Egmont Key's box turtles is not the result of sampling biases; it may result from nest placement. Size-class structure and sex ratios can provide valuable insights into the status and trends of populations of long-lived turtles.

THE ENIGMA OF ETHIOPIAN SEX RATIOS AT BIRTH

2016 ◽  
Vol 49 (5) ◽  
pp. 611-622
Author(s):  
Michel Garenne
Keyword(s):  
Sex Ratio ◽  
Urban Areas ◽  
Maternal Education ◽  
Sex Ratios ◽  
Household Wealth ◽  
Poor Nutritional Status ◽  
Linguistic Groups ◽  
Children Ever Born ◽  
Using Data ◽  
The Many

SummaryThis study analysed sex ratios at birth (defined as the number of male births per 100 female births) using data on children ever-born from three censuses conducted in Ethiopia in 1984, 1994 and 2007. The results showed very high values by any standard, with an average of 108.4 for a sample of some 8.2 million births, with somewhat lower values in urban areas. Analysis of socioeconomic correlates revealed that the sex ratio varied very much by household wealth, from about 110 for very poor women to about 102 for wealthier women. The high value of the sex ratio at birth in Ethiopia could be explained by poverty, used as a proxy for poor nutritional status. In multivariate analysis, the effects of living in urban areas and of maternal education were less important than household wealth. Among the many ethno-linguistic groups, the Nilotic family had higher sex ratios than other groups. The results were confirmed using data from DHS surveys conducted in the country, and by the analysis of children still living at time of census.

Spring emergence of Eastern Box Turtles (Terrapene carolina): influences of individual variation and scale of temperature correlates

2017 ◽  
Vol 95 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Brett A. DeGregorio ◽  
Tracey D. Tuberville ◽  
Robert A. Kennamer ◽  
Bess B. Harris ◽  
I. Lehr Brisbin
Keyword(s):  
Individual Variation ◽  
Meteorological Data ◽  
Terrapene Carolina ◽  
Air Temperatures ◽  
Winter Temperatures ◽  
Box Turtles ◽  
Eastern Box Turtles ◽  
Using Data ◽  
And Behavior ◽  
Spring Emergence

Many organisms spend considerable time in dormancy to avoid stressful environmental conditions. Understanding the timing and triggers of dormancy behavior is critical for understanding an animal’s life history and behavior. Eastern Box Turtles (Terrapene carolina (L., 1758)) avoid winter temperatures by burrowing into the soil and remaining dormant. Identifying the proximate environmental cues that trigger emergence can improve conservation efforts by reducing potential aboveground turtle mortality. During a 17-year study, half of all variation in emergence timing was attributed to individual variation and the habitat that they occupied during dormancy. We suggest that individual variation in emergence timing is common within populations and confounds efforts to identify reliable emergence cues. Additionally, the scale of meteorological data limits the ability to identify emergence predictors. Using data from temperature loggers placed at dormancy locations, we found that surface air temperatures, averaged over the 5 days prior to emergence, were more strongly related to emergence probability than any variables derived from local weather stations. Turtles generally did not emerge from dormancy until the 5-day mean surface temperatures measured at dormancy sites reached approximately 15 °C. Our results suggest that individuals respond differently to environmental thresholds for emergence and individuals may be characterized as risk-taking or risk-aversive.

scholarly journals Adult sex ratios and their implications for cooperative breeding in birds

2017 ◽  
Vol 372 (1729) ◽  
pp. 20160322 ◽  
Author(s):  
Jan Komdeur ◽  
Tamás Székely ◽  
Xiaoyan Long ◽  
Sjouke A. Kingma
Keyword(s):  
Sex Ratio ◽  
Cooperative Breeding ◽  
Adult Population ◽  
Sex Ratios ◽  
Bird Species ◽  
Dispersal Distance ◽  
Sex Bias ◽  
Wide Range ◽  
Cooperatively Breeding ◽  
Using Data

Cooperative breeding is a form of breeding system where in addition to a core breeding pair, one or more usually non-breeding individuals provide offspring care. Cooperative breeding is widespread in birds, but its origin and maintenance in contemporary populations are debated. Although deviations in adult sex ratio (ASR, the proportion of males in the adult population) have been hypothesized to influence the occurrence of cooperative breeding because of the resulting surplus of one sex and limited availability of breeding partners, this hypothesis has not been tested across a wide range of taxa. By using data from 188 bird species and phylogenetically controlled analyses, we show that cooperatively breeding species have more male-biased ASRs than non-cooperative species. Importantly, ASR predicts helper sex ratio: in species with more male-biased ASR, helper sex ratio is also more male biased. We also show that offspring sex ratios do not predict ASRs, so that the skewed ASRs emerge during the period when individuals aim to obtain a breeding position or later during adulthood. In line with this result, we found that ASR (among both cooperatively and non-cooperatively breeding species) is inversely related to sex bias in dispersal distance, suggesting that the cost of dispersal is more severe for the further-dispersing sex. As females usually disperse further in birds, this explains the generally male-biased ASR, and in combination with benefits of philopatry for males, this probably explains why ASR is more biased in cooperatively breeding species. Taken together, our results suggest that a sex bias in helping in cooperatively breeding species relates to biased ASRs. We propose that this relationship is driven by sex-specific costs and benefits of dispersal and helping, as well as other demographic factors. Future phylogenetic comparative and experimental work is needed to establish how this relationship emerges. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

scholarly journals Evolution of sexual size dimorphism and its relationship with sex ratio in carabid beetles of Genus Ceroglossus Solier

2013 ◽  
Vol 59 (6) ◽  
pp. 769-777 ◽  
Author(s):  
Hugo A. Benítez ◽  
Jorge Avaria-Llautureo ◽  
Cristian B. Canales-Aguirre ◽  
Viviane Jerez ◽  
Luis E. Parra ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Sexual Size Dimorphism ◽  
Phylogenetic Signal ◽  
Comparative Method ◽  
Carabid Beetles ◽  
Entire Group ◽  
Geometrical Shape ◽  
Specific Level ◽  
Size Dimorphism ◽  
Morphological Studies

Abstract Although the degree of mate competition, given extreme differences in sex ratio, explains much of the pattern of male-biased size dimorphism among diverse taxa, it fails for some species which have potential for intense male competition for mates and yet exhibit little or no sexual size dimorphism (SSD). This fact suggest that species with low SSD should be express the effect of evolutionary pressure in non-obvious geometrical shape promoted by sex ratio in an evolutionary time scale. To evaluate this hypothesis we used phylogenetic comparative method in a Bayesian framework to investigate the evolution of SSD and the role of sex ratio at inter-specific level in the species of Ceroglossus (Coleoptera: Carabidae). In our results the proportion farthest from 1:1 is associated with more disparate body shape, even though the entire group has minimum variation in sex ratio, which is an intrinsic life history character of this group considering its phylogenetic conservatism or phylogenetic signal. We suggest that the sex ratio has determined the dimorphism degree during evolution of this group, since both traits have increased or decreased together during the species divergence (i.e. positive phylogenetic correlation: r2≈0.85). We suggest that morphological studies of SSD will benefit from using comparative method with Bayesian approaches to assess the effect of phylogenetic history and its uncertainty. Finally, this will be allow to researchers to quantify the uncertainty of specific evolutionary hypotheses accounting for observed sexual dimorphism patterns.

Sex ratios, mating behavior and sexual size dimorphism of the northern water snake, Nerodia sipedon

1995 ◽  
Vol 36 (5) ◽  
pp. 301-311 ◽  
Author(s):  
Patrick J. Weatherhead ◽  
Frances E. Barry ◽  
Gregory P. Brown ◽  
Mark R. L. Forbes
Keyword(s):  
Mating Behavior ◽  
Sexual Size Dimorphism ◽  
Sex Ratios ◽  
Nerodia Sipedon ◽  
Size Dimorphism ◽  
Water Snake ◽  
Northern Water Snake

Male–male contests for mates, sexual size dimorphism, and sex ratio in a natural population of a solitary parasitoid

2013 ◽  
Vol 100 ◽  
pp. 1-8 ◽  
Author(s):  
Margarete V. Macedo ◽  
Ricardo F. Monteiro ◽  
Mariana P. Silveira ◽  
Peter J. Mayhew
Keyword(s):  
Sex Ratio ◽  
Natural Population ◽  
Sexual Size Dimorphism ◽  
Size Dimorphism ◽  
Solitary Parasitoid ◽  
Male Contests
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