Studies on sex-determination in amphibians. V. The effects of changing the water content of the egg, at or before the time of fertilization, on the sex ratio of Bufo lentiginosus

Abstract Rising global temperatures threaten to disrupt population sex ratios, which can in turn cause mate shortages, reduce population growth and adaptive potential, and increase extinction risk, particularly when ratios are male biased. Sex ratio distortion can then have cascading effects across other species and even ecosystems. Our understanding of the problem is limited by how often studies measure temperature effects in both sexes. To address this, the current review surveyed 194 published studies of heat tolerance, finding that the majority did not even mention the sex of the individuals used, with <10% reporting results for males and females separately. Although the data are incomplete, this review assessed phylogenetic patterns of thermally induced sex ratio bias for 3 different mechanisms: sex-biased heat tolerance, temperature-dependent sex determination (TSD), and temperature-induced sex reversal. For sex-biased heat tolerance, documented examples span a large taxonomic range including arthropods, chordates, protists, and plants. Here, superior heat tolerance is more common in females than males, but the direction of tolerance appears to be phylogenetically fluid, perhaps due to the large number of contributing factors. For TSD, well-documented examples are limited to reptiles, where high temperature usually favors females, and fishes, where high temperature consistently favors males. For temperature-induced sex reversal, unambiguous cases are again limited to vertebrates, and high temperature usually favors males in fishes and amphibians, with mixed effects in reptiles. There is urgent need for further work on the full taxonomic extent of temperature-induced sex ratio distortion, including joint effects of the multiple contributing mechanisms.

Download Full-text

Variation in Weight, Size, and Sex Ratio of Coccinellid Adults (Coleoptera: Coccinellidae)

The Canadian Entomologist ◽

10.4039/ent98639-6 ◽

1966 ◽

Vol 98 (6) ◽

pp. 639-644 ◽

Cited By ~ 10

Author(s):

B. C. Smith

Keyword(s):

Body Size ◽

Sex Ratio ◽

Water Content ◽

Food Supply ◽

Sexual Differences ◽

Intraspecies Variation ◽

Food Scarcity ◽

Food Requirement ◽

Males And Females

AbstractThe weight and size of coccinellid adults varied with species, sex, and feeding. Intraspecies variation in weight was generally similar in the eight species studied. Females were more variable than males in body size. Females of some species were heavier and larger than males, and species can be classified on a basis of difference in the weight and size of the sexes.An increase in the food supply after a period of food scarcity affected the sex ratio, as the minimum food requirement of females was greater than males. Females increased in weight more rapidly than males after feeding. The availability of food in the field affected the weight and size of some species. Adult water content was influenced by feeding but not by sex or the quantity of food given to the larva.Males were more abundant in species with small sexual differences in weight and size. The degree of difference in weight and size between males and females may be used as a criterion to select species that are best adapted to survive when food is scarce.

Download Full-text

Sex Determination and Sex Ratio Patterns in Parasitic Hymenoptera

Evolution and Diversity of Sex Ratio ◽

10.1007/978-1-4684-1402-8_14 ◽

1993 ◽

pp. 442-476 ◽

Cited By ~ 26

Author(s):

Robert F. Luck ◽

Richard Stouthamer ◽

Leonard P. Nunney

Keyword(s):

Sex Ratio ◽

Sex Determination ◽

Parasitic Hymenoptera

Download Full-text

Analysis of the sex ratio in Bradysia matogrossensis (Diptera, Sciaridae)

Genetics and Molecular Biology ◽

10.1590/s1415-47572000000100018 ◽

2000 ◽

Vol 23 (1) ◽

pp. 97-103 ◽

Cited By ~ 4

Author(s):

Lincoln S. Rocha ◽

André Luiz P. Perondini

Keyword(s):

Sex Ratio ◽

Sex Determination ◽

X Chromosome ◽

Control Mechanism ◽

Sex Ratios ◽

Laboratory Strain ◽

Chromosome Elimination ◽

Common Control ◽

Males And Females ◽

Successive Generations

In sciarid flies, the control of sex determination and of the progeny sex ratio is exercised by the parental females, and is based on differential X-chromosome elimination in the initial stages of embryogenesis. In some species, the females produce unisexual progenies (monogenic females) while in others, the progenies consist of males and females (digenic females). The sex ratio of bisexual progenies is variable, and departs considerably from 1:1. Bradysia matogrossensis shows both monogenic and digenic reproduction. In a recently established laboratory strain of this species, 15% of the females were digenic, 10% produced only females, 13% produced only males, and 62% produced progenies with one predominant sex (33% predominantly of female and 29% predominantly male progenies). These progeny sex ratios were maintained in successive generations. Females from female-skewed progenies yielded female- and male-producing daughters in a 1:1 ratio. In contrast, daughters of females from male-skewed progenies produce bisexual or male-skewed progenies. The X-chromosome of B. matogrossensis shows no inversion or other gross aberration. These results suggest that the control of the progeny sex ratio (or differential X-chromosome elimination) involves more than one locus or, at least, more than one pair of alleles. The data also suggest that, in sciarid flies, monogeny and digeny may share a common control mechanism.

Download Full-text

Unexpected resilience of species with temperature-dependent sex determination at the Cretaceous–Palaeogene boundary

Biology Letters ◽

10.1098/rsbl.2010.0882 ◽

2010 ◽

Vol 7 (2) ◽

pp. 295-298 ◽

Cited By ~ 15

Author(s):

Sherman Silber ◽

Jonathan H. Geisler ◽

Minjin Bolortsetseg

Keyword(s):

Climate Change ◽

Sex Ratio ◽

Sex Determination ◽

Volcanic Eruptions ◽

Egg Laying ◽

Molecular Clocks ◽

Temperature Dependent ◽

Hell Creek Formation ◽

Male Preponderance ◽

Genotypic Sex Determination

It has been suggested that climate change at the Cretaceous–Palaeogene (K–Pg) boundary, initiated by a bolide impact or volcanic eruptions, caused species with temperature-dependent sex determination (TSD), including dinosaurs, to go extinct because of a skewed sex ratio towards all males. To test this hypothesis, the sex-determining mechanisms (SDMs) of Cretaceous tetrapods of the Hell Creek Formation (Montana, USA) were inferred using parsimony optimizations of SDMs on a tree, including Hell Creek species and their extant relatives. Although the SDMs of non-avian dinosaurs could not be inferred, we were able to determine the SDMs of 62 species; 46 had genotypic sex determination (GSD) and 16 had TSD. The TSD hypothesis for extinctions performed poorly, predicting between 32 and 34 per cent of survivals and extinctions. Most surprisingly, of the 16 species with TSD, 14 of them survived into the Early Palaeocene. In contrast, 61 per cent of species with GSD went extinct. Possible explanations include minimal climate change at the K–Pg, or if climate change did occur, TSD species that survived had egg-laying behaviour that prevented the skewing of sex ratios, or had a sex ratio skewed towards female rather than male preponderance. Application of molecular clocks may allow the SDMs of non-avian dinosaurs to be inferred, which would be an important test of the pattern discovered here.

Download Full-text