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opencc-by-4.0Nov 2011View details →

Fig. 6 in Seasonal changes in the gonadossomatic index, allometric condition factor and sex ratio of an auchenipterid catfish from eastern Amazonia

Fig. 6. Bimonthly variation in the raw data (a,c) and mean values (b, d) for the condition factor (K) in juvenile (a, b) and adult (c, d) female of the Auchenipterichthys longimanus collected from July 2008 to July 2009 in the Caxiuanã National Forest.

opencc-zeroFeb 2022View details →

Brood sex ratio, early chick survival, and cell-mediated immunity measurements for 3 experimental groups of Larus canus and Chroicocephalus ridibundus pairs

Sex allocation theory predicts that parents should adjust their brood sex ratio to maximize fitness returns in relation to parental investment. Adaptive adjustment of sex ratio may be driven by differential costs of rearing sons and daughters or differential benefits of investing limited resources into offspring of different sex. In both cases, possible sex ratio bias should depend on parental condition. For sexually dimorphic birds with males larger than females, sons may be less likely to fledge since they are more vulnerable to food shortages or because they have impaired immunocompetence due to higher testosterone levels. Poor condition females should thus overproduce daughters to minimize possible reproductive failure. We manipulated the number of eggs laid and the amount of food available to laying females to induce differences in the condition in two gull species differing in sexual size-dimorphism. In the Black-headed Gull (Chroicocephalus ridibundus), sexual size differences are marginal, but in the Mew Gull (Larus canus, MG) males are 11% larger. In both species, females forced to lay an additional egg (presumed in worse condition) overproduced daughters, while females receiving supplemental food before laying (presumed improved condition) overproduced sons. This sex ratio skew was larger in MG, species with larger size dimorphism. Chick immunocompetence at hatching was unrelated to sex, being higher in broods of fed mothers and lower for chicks hatched from last-laid eggs. Chick survival between hatching and day 5 post-hatch was positively related to their immunocompetence, but chicks from last-laid eggs and males of the more dimorphic species (MG) survived less well. Results indicate that costs of raising larger sex offspring coupled with parental condition shape brood sex ratio in populations studied. Adaptive brood sex ratio adjustment occurs mostly before egg-laying and includes differential sex allocation in eggs depending on the probability of producing a fledged chick.

opencc-zeroFeb 2022View details →

Antler detection from the sky: deer sex ratio monitoring using drone-mounted thermal infrared sensors

Sex differences in large mammals with sexual dimorphism are important ecological and evolutionary issues and key factors for wildlife management. To examine the potential use of drone (unmanned aerial vehicle; UAV) observation using thermal infrared images for sex ratio monitoring of deer, we conducted UAV surveys at night in a sparse forest located on the distribution periphery of sika deer (Cervus nippon) and wild boar (Sus scrofa) local populations during summer and winter. Of the 163 thermal infrared images of large mammals detected, 132 (81.0%) and 16 (9.8%) were identified for deer and wild boar, respectively. In addition, velvet antlers of deer were visually recognized during summer, and 92% of the detected deer were antlered. This biased sex ratio would be a characteristic in the distribution periphery of local deer populations. Therefore, monitoring abundance and sex ratio using thermal infrared sensors on UAVs can improve deer management especially in the distribution periphery of local populations.

Figure 8 in Sex ratio, oocyte development and spawning season of Mediterranean moray eel (Muraena helena) from the northern coast of Tunisia

Figure 8. – Section of gonad, illustrating the actively spawning subphase of ovary with A) a postovulatory follicle (POF) and B) cortical alveolar oocytes (CA) and mature oocytes in early germinal vesicle migration (indicated by asterisk), late germinal vesical migration (GVM) and germinal vesicle breakdown (GVBD).

Figure 6 in Sex ratio, oocyte development and spawning season of Mediterranean moray eel (Muraena helena) from the northern coast of Tunisia

Figure 6. – Section of gonad, illustrating the developing reproductive phase of ovary (PG = primary growth oocyte; CA = cortical alveolar oocyte; Vtg1 = primary vitellogenic oocyte; Vtg2 = secondary vitellogenic oocyte).

Figure 4 in Sex ratio, oocyte development and spawning season of Mediterranean moray eel (Muraena helena) from the northern coast of Tunisia

Figure 4. – Section of gonad, illustrating the spawning capable reproductive phase of testis (Sg2 = secondary spermatogonia; Sc1 = primary spermatocyte; Sc2 = secondary spermatocyte; St = spermatid; Sz = spermatozoa).

Figure 3 in Sex ratio, oocyte development and spawning season of Mediterranean moray eel (Muraena helena) from the northern coast of Tunisia

Figure 3. – Section of gonad, illustrating the early developing subphase of testis (Sg2 = secondary spermatogonia; Sc1 = primary spermatocyte; Sc2 = secondary spermatocyte).

opencc-by-4.0Apr 2019View details →

Highly feminised sex-ratio estimations for the world's third-largest nesting aggregation of loggerhead sea turtles

All data uploaded is in a CSV format. TempVariation contains the daily average temperatures for each island (pooling data between years and beaches). LumTempYear contains the comparison between temperature and luminosity for each beach for all 3 years of data collection. LumTemp contains pools the data from LumTempYear so that there is one average temperature reading per beach. The weightings column states the percentage nesting occurring on that beach. BeachHist builds upon LumTemp including the estimated proportion of nests experiencing critically high temperatures, based on the daily temperatures received from the TempVariation.

Fig. 4 in Flight patterns and sex ratio of beetles of the subfamily Dynastinae (Coleoptera, Melolonthidae)

Fig. 4. Circular histogram showing peak flight activity of: (A) Cyclocephala cearae; (B) C. distincta; (C) Dyscinetus dubius; (D) Stenocrates holomelanus; (E) C. paraguayensis; (F) Ligyrus (Ligyrus) cuniculus, during one year of collection using light trap at Campo de Instrução Marechal Newton Cavalcanti, Abreu e Lima, PE, Brazil. Black line = mean vector and confidence interval.

Fig. 3 in Flight patterns and sex ratio of beetles of the subfamily Dynastinae (Coleoptera, Melolonthidae)

Fig. 3. Rainfall effect in the most abundant tribes of Dynastinae (Melolonthidae), during one year of collection using light trap at Campo de Instrução Marechal Newton Cavalcanti, Abreu e Lima, PE, Brazil: (A) Mean abundance of Cyclocephalini beetles, recorded monthly, between December 2010 and November 2011 (except April 2011). (B) Mean abundance of Pentodontini beetles, recorded monthly, between December 2010 and November 2011 (except April 2011). (C) Rainfall, recorded monthly, between December 2010 and November 2011 (except April 2011).

Fig. 1 in Flight patterns and sex ratio of beetles of the subfamily Dynastinae (Coleoptera, Melolonthidae)

Fig. 1. Map showing sampling site: (A) Pernambuco State represented in black. (B) Black dot representing Campo de Instrução Marechal Newton Cavalcanti, Abreu e Lima, Pernambuco, Brazil. (C) Black dot representing sampling site at Marechal Newton Cavalcanti, Abreu e Lima, Pernambuco, Brazil.

Fig. 2 in Flight patterns and sex ratio of beetles of the subfamily Dynastinae (Coleoptera, Melolonthidae)

Fig. 2. Light trap model used for beetle sampling: (A) Black light bulb. (B) Mixed mercury bulb. (C) Light support.

opencc-by-4.0Apr 2015View details →

Fig. 1 in Sex ratios in juveniles and adults of Dichroplus maculipennis (Blanchard) and Borellia bruneri (Rehn) (Orthoptera: Acrididae)

Fig. 1. (A), (B), (E)–(H) Dichroplus maculipennis. (A) Adult female. (B) Juvenile female. (E) and (F) Male external genitalia, dorsal (E) and lateral (F) views. (G) and (H) Juvenile female external genitalia, dorsal (G) and lateral (H) views. (C), (D), (I)–(L) Borellia bruneri. (C) Adult female. (D) Juvenile female. (I) and (J) Male external genitalia, dorsal (I) and lateral (J) views. (K) and (L) Juvenile female external genitalia, dorsal (K) and lateral (L) views.

opencc-zeroDec 2012View details →

Data from: A method for estimating population sex ratio for sage-grouse using noninvasive genetic samples

Population sex ratio is an important metric for wildlife management and conservation, but estimates can be difficult to obtain, particularly for sexually monomorphic species or for species that differ in detection probability between the sexes. Noninvasive genetic sampling (NGS) using polymerase chain reaction (PCR) has become a common method for identifying sex from sources such as hair, feathers, or feces, and is a potential source for estimating sex ratio. If, however, PCR success is sex-biased, naively using NGS could lead to a biased sex ratio estimator. We measured PCR success rates and error rates for amplifying the W and Z chromosomes from greater sage-grouse (Centrocercus urophasianus) fecal samples, examined how success and error rates for sex identification changed in response to fecal sample exposure time, and used simulation models to evaluate precision and bias of 3 sex assignment criteria for estimating population sex ratio with variable sample sizes and levels of PCR replication. We found PCR success rates were higher for females than males and that choice of sex assignment criteria influenced the bias and precision of corresponding sex ratio estimates. Our simulations demonstrate the importance of considering the interplay between the sex-bias of PCR success, number of genotyping replicates, sample size, true population sex ratio, and accuracy of assignment rules for designing future studies. Our results suggest that using fecal DNA for estimating the sex ratio of sage-grouse populations has great potential and, with minor adaptations, should be applicable to numerous species.

opencc-zeroDec 2012View details →

Data from: Sex ratio and density affect sexual selection in a sex-role reversed fish

Understanding how demographic processes influence mating systems is important to decode ecological influences on sexual selection in nature. We manipulated sex ratio and density in experimental populations of the sex-role reversed pipefish Syngnathus typhle. We quantified sexual selection using the Bateman gradient (ß′ss), the opportunity for selection (I), and sexual selection (Is), and the maximum standardized sexual selection differential (s′max). We also measured selection on body length using standardized selection differentials (s′) and mating differentials (m′), and tested whether the observed I and Is differ from values obtained by simulating random mating. We found that I, Is, and s′max, but not ß′ss, were higher for females under female- than male-bias and the opposite for males, but density did not affect these measures. However, higher density decreased sexual selection (m′ but not s′) on female length, but selection on body length was not affected by sex ratio. Finally, Is but not I was higher than expected from random mating, and only for females under female bias. This study demonstrates that both sex ratio and density affect sexual selection and that disentangling interrelated demographic processes is essential to a more complete understanding of mating behavior and the evolution of mating systems.

opencc-zeroDec 2015View details →

Data from: Crowd control: sex ratio affects sexually selected cuticular hydrocarbons in male Drosophila serrata

Although it is advantageous for males to express costly sexually selected signals when females are present, they may also benefit from suppressing these signals to avoid costly interactions with rival males. Cuticular chemical profiles frequently function as insect sexual signals; however, few studies have asked whether males alter these signals in response to their social environment. In Drosophila serrata, an Australian fly, there is sexual selection for a multivariate combination of male cuticular hydrocarbons (CHCs). Here, we show that the ratio of females to males that an adult male experiences has a strong effect on his CHC expression, with female-biased adult sex ratios eliciting greater expression of CHC profiles associated with higher male mating success. Classical models predict that male reproductive investment should be highest when there is a small but nonzero number of rivals, but we found that males expressed the most attractive combination of CHCs when there were no rivals. We found that male CHCs were highly sensitive to adult sex ratio, with males expressing higher values of CHC profiles associated with greater mating success as the ratio of females to males increased. Moreover, sex ratio has a stronger effect on male CHC expression than adult density. Finally, we explore whether sex ratio affects the variance among a group of males in their CHC expression, as might be expected if individuals respond differently to a given social environment, but find little effect. Our results reveal that subtle differences in social environment can induce plasticity in male chemical signal expression.

opencc-zeroDec 2010View details →

Data from: Persistence of an extreme male-biased adult sex ratio in a natural population of polyandrous bird

In a number of insects, fishes and birds the conventional sex roles are reversed: males are the main care provider whereas females focus on matings. The reversal of typical sex roles is an evolutionary puzzle, because it challenges the foundations of sex roles, sexual selection and parental investment theory. Recent theoretical models predict that biased parental care may be a response to biased adult sex ratios (ASRs). However, estimating ASR is challenging in natural populations, because males and females often have different detectabilities. Here we use demographic modelling with field data from 2101 individuals, including 579 molecularly sexed offspring, to provide evidence that ASR is strongly male-biased in a polyandrous bird with male-biased care. The model predicts 6.1 times more adult males than females (ASR = 0.860, proportion of males) in the Kentish plover Charadrius alexandrinus. The extreme male-bias is consistent between years, and concordant with experimental results showing strongly biased mating opportunity toward females. Based on these results we conjecture that parental sex role reversal may occur in populations that exhibit extreme male-biased ASR.

opennotspecifiedMar 2009View details →

Figure 2 in Natural history of Peucetia flava (Araneae, Oxyopidae): seasonal density fluctuation, phenology and sex ratio on the glandular plant Rhyncanthera dichotoma (Melastomataceae)

Figure 2. Phenogram of the Peucetia flava population on plants of Rhyncanthera dichotoma.

opencc-zeroOct 2021View details →

Reproductive success and mortality of male and female Daphnia at different sex ratios

This dataset contains data from Daphnia sexual reproduction experiments described in the paper: "Galimov YR, Haag CR, Tukhbatullin AR, Tchabovsky AV 2021. Sex ratio effects on reproductive success of male and female Daphnia. Journal of Evolutionary Ecology ". We compared reproductive success of male and female Daphnia in experimental populations with sex ratios varying from one male per 81 females to one male per one female. In males, reproductive success strongly and monotonically decreased with decreasing number of females per male. In females, in contrast, mating success and reproductive success were reduced only at the most female-biased sex ratio (1:81), when many females remained unmated and unfertilized, and then again at equal sex ratios, probably due to negative effects of high density or stress induced by numerous males. Our results suggest that mating competition and the opportunity for sexual selection may exist not only in males but, at least periodically, also in females.