Significant Sexual Size Dimorphism Research Articles

Invasive American Bullfrogs Age, Body Size, and Sexual Size Dimorphism Geographical Variation in Northwestern China

Invasive species impact both the local biota and human economies and are a very serious threat to biodiversity. The American bullfrog was initially introduced into northwestern China and many other sites for aquacultural purposes. Then, the frogs escaped and established feral populations. Here, we investigated the variations in age, body size, and sexual size dimorphism of two breeding populations inhabiting the southern (warm and dry) and northern (cold and wet) regions of Xinjiang province in northwestern China. Both populations originated from a single source that was introduced into Xinjiang 54 years ago. In both populations, males were significantly smaller than females, indicating significant sexual size dimorphism. The mean age and body size of both sexes in the population in the colder region were lower than those of the population in the warmer region. Bullfrogs in the southern population had a higher degree of sexual size dimorphism. These results increase our understanding of the American bullfrog, which could help in the development of strategies to control this invasive species.

Sexual selection leads to positive allometry but not sexual dimorphism in the expression of horn shape in the blue wildebeest, Connochaetes taurinus

Sexual selection is thought to be an important driver of adaptation, speciation and extinction. Empirically testing these predictions across macroevolutionary timescales first requires an understanding of the morphology of secondary sexual traits in extant taxa. We used three-dimensional geometric morphometrics to analyse a large sample of the skull of the blue wildebeest, Connochaetes taurinus, in which horns are found in both sexes but only used in intrasexual competition in males. We show that the horns fit several predictions of secondary sexual traits; overall skull shape is significantly correlated with size (R2 = 0.38, p = 0.001), and the sexually selected horns show drastically higher growth rates and variation than any other skull element, supporting previous findings. We also find that despite showing significant sexual dimorphism in shape and size (R2 = 0.21, p = 0.001), allometric growth trajectories of sexes are identical (R2 = 0.01, p = 0.635) and dimorphism is not readily detectable without prior knowledge of sex, and is not possible when shape is corrected for size. Our results show that even with strong sexual selection operating in only one sex, the expression of secondary sexual traits may show characteristic and indistinguishable patterns of growth and variance in both sexes.

Body Size Structure and Sex Ratio in a Population of the Common Lizard Zootoca vivipara (Lichtenstein, 1823) from SW Poland

We present data on the population structure, body size variations and allometric growth patterns for a common lizard (Zootoca vivipara) population from Southwestern Poland. We measured 339 lizards (89 males, 75 females, 63 subadults and 111 juveniles). The sex ratio did not differ from 1:1; however, we recorded intra-seasonal variations. There was significant sexual size dimorphism (males were smaller in body length), as well as tail length (males had longer tails) and body mass dimorphism (females were heavier). We also found sexual differences in the allometric pattern of tail growth, i.e. there was an isometry for males but a negative allometry for females.

Genome-wide association study reveals the genetic basis of growth trait in yellow catfish with sexual size dimorphism

Sexual size dimorphism has been widely observed in a large number of animals including fish species. Genome-wide association study (GWAS) is a powerful tool to dissect the genetic basis of complex traits, whereas the sex-differences in the genomics of animal complex traits have been ignored in the GWAS analysis. Yellow catfish (Pelteobagrus fulvidraco) is an important aquaculture fish in China with significant sexual size dimorphism. In this study, GWAS was conducted to identify candidate SNPs and genes related to body length (BL) and body weight (BW) in 125 female yellow catfish from a breeding population. In total, one BL-related SNP and three BW-related SNPs were identified to be significantly associated with the traits. Besides, one of these SNPs (Chr15:19195072) was shared in both the BW and BL traits in female yellow catfish, which was further validated in 185 male individuals and located on the exon of stat5b gene. Transgenic yellow catfish and zebrafish that expressed yellow catfish stat5b showed increased growth rate and reduction of sexual size dimorphism. These results not only reveal the genetic basis of growth trait and sexual size dimorphism in fish species, but also provide useful information for the marker-assisted breeding in yellow catfish.

Morphological variations based on geometric morphometrics between male and female pronota of Oxythyrea cinctella (Schaum, 1841) (Coleoptera: Scarabaeidae, Cetoniinae)

In this study, pronotum size and shape were used as an exemplar characteristic to evaluate the utility of pronotal morphology on the sexual dimorphism determination of the scarab beetle Oxythyrea cinctella (Schaum, 1841). Using geometric morphometrics, the sexual size and shape dimorphism of pronotum of 85 specimens (45 females, 40 males) collected from Ankara Province (Turkey) were analyzed. Results of geometric morphometrics revealed that there is statistically significant sexual size and shape dimorphism in pronotum. Further, the mean centroid sizes of the females was significantly larger than that of the males. Finally, multivariate regression results indicated that size has negligible influence on the differentiation in pronotum shape between sexes. We hope the results here presented would be helpful for the further understanding of the sexual dimorphism in the beetle genus Oxythyrea.

Sex-specific markers developed by genome-wide 2b-RAD sequencing confirm an XX/XY sex determination system in Chinese longsnout catfish (Leiocassis longirostris)

Longsnout catfish (Leiocassis longirostris), an important commercial fish in China, shows significant sexual size dimorphism. However, the sex determination system and mechanism of longsnout catfish remain unknown. In this study, an effective protocol of artificial gynogenesis using heterologous sperm was successfully developed and male heterogametic XX/XY sex determination system was revealed in longsnout catfish. Subsequently, sex-specific markers were developed based on isolated homologous X-specific and Y-specific sequences by 2b-RAD sequencing and PCR amplification. Finally, the Y-specific and XY-shared primers were developed and validated in a full-sib family, a gynogenetic population and two local populations, which further verify the sex determination system. Therefore, this study not only reveals XX/XY sex determination system in longsnout catfish, but also provides applicable sex-specific markers for production of all-male population for aquaculture in the future.

Determining home range, changes in habitat use with time, and the threats to an endangered freshwater turtle (Rafetus euphraticus) in Turkey

Abstract The Euphrates softshell turtle (Rafetus euphraticus) is the most threatened chelonian species in the Middle East, where it is endemic to the Tigris and Euphrates basins. Since the ecology of this species is little known, it is difficult to plan any reliable action for its correct management and conservation. To enhance the scientific knowledge on R. euphraticus, and to establish a science‐based management strategy, a detailed investigation was undertaken on the distribution, habitat, activity and home range of R. euphraticus in Turkey. The previous distribution records in Turkey are for the 1990s; thus, this study is the first comprehensive field research on the species after nearly 3 decades. There was a significant sexual size dimorphism in the Turkish population, with males larger than females. Four individuals were radiotracked for 1 year. The mean home range was highly variable depending on how it was calculated, but that of males was considerably greater than that of females by all methods used. A quantitative evaluation was made of habitat change with time. The land cover classes potentially available to turtles in the Euphrates River basin increased by more than 100% between the 1990s and 2018: 92% of this enhancement was derived from water bodies and coastal lands. Fifteen dams have been built in the lower part of the basins in the last 30 years. In addition, continuing human interactions have caused the fragmentation or destruction of suitable habitats for R. euphraticus. The factors threatening R. euphraticus were assessed and a conservation action plan was developed. Some objectives such as monitoring and creating awareness of this action plan have been met while others are still waiting to be achieved.

Life-history traits and the first demographic data of Iranian population of the West Asian Lemon-Yellow Tree Frog, Hyla savignyi (Audouin, 1827)

The life-history of an organism consists of its lifetime pattern of growth, development, storage, age, and reproduction. In this study, some life-history traits of Hyla savignyi were studied in populations from different parts of Iran. The microscopic and macroscopic analysis showed that testicular activity in H. savignyi is potentially continuous, reaching its peak level in April. Metamorphosis was completed in approximately 102 days after egg deposition, and body size at metamorphosis was 10 mm. Significant sexual size dimorphism was present in all populations, and a larger female asymptotic body size was observed (43.07 mm for females vs 41.16 mm for males). The adult survival rate (S) and life expectancy (ESP) were the same for both sexes (S = 0.73 and ESP = 4.2 years). Age and body size were positively correlated with each other for both females and males. Maximum longevity was recorded to be six years in both females and males, and ages of sexual maturity were estimated to be two or three years in breeding individuals. The adult sample age ranged from two to six years (mean age of females: 4.40±0.68 years; males: 3.63±0.13 years). Our data confirm the general patterns of body size variation and mean age in anurans and show that females are larger than males and live longer.

The canine counts! Significance of a craniodental measure to describe sexual dimorphism in canids: Golden jackals (Canis aureus) and African wolves (Canis lupaster)

Sexual dimorphism is a widespread phenomenon among mammals, including carnivorans. While sexual dimorphism in golden jackals (Canis aureus) has been analysed in the past, in the related and apparently convergent canid, the African wolf (Canis lupaster), it is poorly studied and showed to be relatively small. Previously, sexual size dimorphism (SSD) research in these species was mostly based on skull and body measurements. In our study, we also included dental measurements, namely the diameter of the canine. We used 11 measured sections of 104 adult specimens, comprising 61 golden jackal and 43 African wolf skulls. Data analyses were carried out through logistic regression and conditional inference trees (CIT). To compare the results of SSD to other species, sexual dimorphism indices (SDI) were calculated. Golden jackals and African wolves show significant sexual size dimorphism, both in cranial and dental size. The logistic regression revealed that the mesiodistal diameter of the upper canine is most effective in discerning the sexes. The difference in the calculated SDI of the canine diameter between the sexes amounted to 8.71 in golden jackals and 14.11 in African wolves, respectively—with regional diversity. Thus, the canine diameter is an important measure to investigate SSD as well as an easy tool to apply in the field.

Dorcadion micans J. Thomson, 1867 (Coleoptera: Cerambycidae) Pronotumunda Geometrik Morfometri Kullanarak Eşeysel Dimorfizm

Sexual dimorphism is one of the most notable sources of phenotypic variation in animals. The expression of sexual traits varies widely for many species of insects. In this study, we analyzed the sexual size and shape dimorphism of pronotum in Turkish endemic species, Dorcadion micans J. Thomson, 1867 (Coleoptera: Cerambycidae). Our results have showed that there is statistically significant sexual size and shape dimorphism in pronotum. Males have a longer and sharper pronotum shape with smaller pronotum size than females. Multivariate regression results indicated that size has negligible influence on the differentiation in pronotum shape between sexes.

Integrative Transcriptome Sequencing Reveals the Molecular Difference of Maturation Process of Ovary and Testis in Mud Crab Scylla paramamosain

The mud crab Scylla paramamosain is a species with significant sexual dimorphism in growth rate and body size, of which the females are of higher economic and nutritional values than the males. Accordingly, there is an urgent need to explore the molecular mechanism underlying sex determination and gonadal differentiation. The single-molecule long-read technology combining with RNA sequencing was employed to construct a full-length transcriptome for gonads of S. paramamosain. In total, 1,562,819 FLNC reads were obtained from 1,813,758 reads of inserts (ROIs). Among them, the 10,739 fusion isoforms corresponded to 23,634 reads and were involved in 5,369 genes in the reference annotation. According to the criteria for new transcripts, a total of 213,809 isoforms were recognized as novel transcripts and then matched against Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), NR, Swissprot, and KOG databases. We also identified 22,313 SSRs, 169,559 lncRNAs, and 25,451 SNPs. Additionally, 349,854 alternative splicing (AS) events from 8,430 gene models were detected, and 5,129 polyadenylation sites were profiled from 3,090 genes. GO and KEGG annotation indicated that AS and APA probably play important roles in the gonadal development and maturation. Besides, the DEGs associated with gonadal development and maturation were identified and analyzed based on the RNA-Seq data.

Ontogenetic and sexual patterns in the cranial system of the brown rat (Rattus norvegicus Berkenhout, 1769) from Hai'l region, Kingdom of Saudi Arabia.

The brown rat, Rattus norvegicus, is a model system in ecological and systematic science, but little is known about its skull morphology and developmental patterns. Our objective was to investigate the cranial ontogenetic patterns in the brown rats, from Hai’l, Kingdom of Saudi Arabia.Quantitative analysis of sexual shape dimorphisms (SShD) and age-classes were investigated using 28 landmarks plotted on two-dimensional images for dorsal and ventral views. Our results detected statistically significant sexual dimorphism (P-value <0.0001) in cranial shape and size for R. norvegicus. Nevertheless, males are much larger than females and display variation around the brain-case, while females tend to show greater variation around the occipital bone. In addition, there are subtle age-classes during ontogeny in the skull. However, the older age classes (i.e. age classes 3 and 4) represent well-built crania with an extended case of the brain and shortest nasal, while youngest specimens represent an elongated snout of minimum crania.Future GMM research should therefore examine the pre-defined age-classes and sex-related individuals in brown rat skulls in relation to genotype to characterize trends in skull shape variation that may affect teeth, zygomatic arches, brain case, and compartments of muscle attachments through its ecological patterns.

Population structure and body size of the Sahara blue-eyed pond turtle Mauremys leprosa saharica, from an isolated pond in the Lower Draa Basin, southern Morocco.

The marginal populations of the Sahara blue-eyed pond turtle, Mauremys leprosa saharica (Testudines: Geoemydidae) in the pre-Saharan area in the Lower Draa Valley, are faced to extreme environmental conditions of arid climate and anthropogenic activities including overuse of water and land salinization. In this study, we investigated a small isolated population of the blue-eyed pond turtle at Sidi El Mehdaoui Oasis, Lower Draa Valley, to determine its population structure and morphometric characteristics. Water salinity was about 24% of seawater and dissolved oxygen concentration was less than 3mgl-1 (sub-hypoxia). The average body size of adults (carapace length) was much lower in comparison to other Moroccan populations. Among adult individuals, the mean carapace lengths were 103 ± 21mm and 104.4 ± 35mm for males and females, respectively. The corresponding mean body mass were 173 ± 92.4g and 135 ± 52g. There were no significant differences between sexes for size or weight. The studied population is small, with a predominance of adults (75%). A significant sexualsize dimorphism was found. In fact, the Sexual Dimorphism Index for size had the lowest level ever described for the species possibly because of the low productivity of this marginal isolated habitat. The increased drought and salinization are major threats to the long-term persistence of the vulnerable populations of the Saharan blue-eyed pond turtle and their habitats. Therefore, conservation measures of these populations through the protection of their habitats are very urgent.

Cranial variation in allactagine jerboas (Allactaginae, Dipodidae, Rodentia): a geometric morphometric study.

Allactaginae is a subfamily of dipodids consisting of four- and five-toed jerboas (Allactaga, Allactodipus, Orientallactaga, Pygeretmus, Scarturus) found in open habitats of Asia and North Africa. Recent molecular phylogenies have upended our understanding of this group’s systematics across taxonomic scales. Here, I used cranial geometric morphometrics to examine variation across 219 specimens of 14 allactagine species (Allactaga major, A. severtzovi, Orientallactaga balikunica, O. bullata, O. sibirica, Pygeretmus platyurus, P. pumilio, P. shitkovi, Scarturus aralychensis, S. euphraticus, S. hotsoni, S. indicus, S. tetradactylus, S. williamsi) in light of their revised taxonomy. Results showed no significant sexual size or shape dimorphism. Species significantly differed in cranial size and shape both overall and as species pairs. Species identity had a strong effect on both cranial size and shape. Only a small part of cranial shape variation was allometric, with no evidence of unique species allometries, and most specimens fit closely to the common allometric regression vector. Allactaga was the largest, followed by Orientallactaga, Scarturus, and finally Pygeretmus. Principal component 1 (PC1) separated O. bullata+O. balikunica+S. hotsoni (with inflated bullae along with reduced zygomatic arches and rostra) from A. major+A. severtzovi+O. sibirica (with converse patterns), while PC2 differentiated Orientallactaga (with enlarged cranial bases and rostra along with reduced zygomatic arches and foramina magna) from Scarturus+Pygeretmus (with the opposite patterns). Clustering based on the unweighted pair group method with arithmetic mean (UPGMA) contained the four genera, but S. hotsoni clustered with O. bullata+O. balikunica and O. sibirica clustered with A. major+A. severtzovi, likely due to convergence and allometry, respectively.

Machine-learning strategies for testing patterns of morphological variation in small samples: sexual dimorphism in gray wolf (Canis lupus) crania

BackgroundStudies of mammalian sexual dimorphism have traditionally involved the measurement of selected dimensions of particular skeletal elements and use of single data-analysis procedures. Consequently, such studies have been limited by a variety of both practical and conceptual constraints. To compare and contrast what might be gained from a more exploratory, multifactorial approach to the quantitative assessment of form-variation, images of a small sample of modern Israeli gray wolf (Canis lupus) crania were analyzed via elliptical Fourier analysis of cranial outlines, a Naïve Bayes machine-learning approach to the analysis of these same outline data, and a deep-learning analysis of whole images in which all aspects of these cranial morphologies were represented. The statistical significance and stability of each discriminant result were tested using bootstrap and jackknife procedures.ResultsOur results reveal no evidence for statistically significant sexual size dimorphism, but significant sex-mediated shape dimorphism. These are consistent with the findings of prior wolf sexual dimorphism studies and extend these studies by identifying new aspects of dimorphic variation. Additionally, our results suggest that shape-based sexual dimorphism in the C. lupus cranial complex may be more widespread morphologically than had been appreciated by previous researchers.ConclusionOur results suggest that size and shape dimorphism can be detected in small samples and may be dissociated in mammalian morphologies. This result is particularly noteworthy in that it implies there may be a need to refine allometric hypothesis tests that seek to account for phenotypic sexual dimorphism. The methods we employed in this investigation are fully generalizable and can be applied to a wide range of biological materials and could facilitate the rapid evaluation of a diverse array of morphological/phenomic hypotheses.

Size, shape and sex differences in three subspecies of Black-tailed Godwits Limosa limosa

ABSTRACT Capsule: Black-tailed Godwits Limosa limosa show sexual size dimorphism and size differences between the subspecies. The shape varies slightly between the subspecies, but not between the sexes. Aims: To investigate whether and how the three subspecies of Black-tailed Godwits, and the sexes of these subspecies, differ in size and shape. Methods: We collected body dimensions (lengths of the bill, total head, tarsus, tarsus-toe and wing) of adult Black-tailed Godwits from three locations (Iceland, the Netherlands and northwest Australia) corresponding to the breeding or wintering grounds of three known subspecies (islandica, limosa and melanuroides, respectively). Determining sex by molecular assays, we computed degrees of sexual size dimorphism. Using principal component analysis (PCA), we compared differences in size and shape among the different subspecies. Results: The limosa subspecies was the largest and also showed the most significant sexual size dimorphism. Sexual size dimorphism was smallest for wing length and largest for bill length. The first two axes of the PCA that included all subspecies of both sexes explained 94% of the total variation. Most body dimensions were highly correlated with each other, but wing length varied independently of the other dimensions. Males and females differed only in size (the first axis). However, one of the two small subspecies, islandica, also differed in shape (the second axis) from limosa and melanuroides. Conclusions: In all three subspecies of Black-tailed Godwits, females are larger than males. The fact that subspecies differed in the degree of size dimorphism and slightly in shape hints at sex-related differences in the ecological selection pressures between the different flyways.

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

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).

Interspecific size- and sex-related variation in the cranium of European brown frogs (Genus Rana)

The vertebrate skull is considered as phylogenetically conserved, but shows extensive diversification in many clades due to various environmental, climate and habitat influences. We explored the cranial size and shape differences of three closely related brown frog species, Rana temporaria, R. dalmatina and R. graeca to emphases the interspecific variation and intraspecific sexual differences, the allometric patterns in cranial shape changes and the relationship between cranial shape, phylogeny, and ecological similarity. Brown frogs significantly differ in cranial size and shape. Interspecific cranial shape changes are under strong influence of size variation. When size is considered, our results show that R. dalmatina is the most divergent species, while differences between R. dalmatina and R. temporaria cranial shapes are diminished when size is removed and peculiar features of R. graeca cranium arise (the most robust and rounded cranium). In both cases, with size and without size, major shape changes are related to the position of quadratum and width of the cranium at the level of anterior margin of eye. When comparing non-allometric shape with ecological similarity and phylogenetic relatedness we found that ecologically similar but phylogenetically more distant species shared the cranial morphology. Intraspecific patterns of cranial phenotypic variation in brown frogs showed significant cranium sexual size and shape dimorphism and absence of allometric scaling between sexes. More detailed studies on the relation of morphology and ecology in brown frogs are necessary to explain the mechanism behind cranial size and shape variation.

Sexual size and shape dimorphism in two ground beetle taxa, Carabus (Procrustes) coriaceus cerisyi and C. (Morphocarabus) kollari praecellens (Coleoptera: Carabidae) - A geometric morphometric approach

We investigated morphometric variation in size and shape of the head, pronotum, and abdomen between the taxa and sexes of two ground beetles, Carabus coriaceus cerisyi Dejean, 1826 and C. kollari praecellens Palliardi, 1825. These two taxa differ in overall size, and both of them are characterized by significant sexual size dimorphism. In many taxa, allometry, the relationship between changes in shape and changes in size, can be a major component of intra- and interspecific variation in body shape. In the present study, we applied landmark-based geometric morphometrics to explore allometric and non-allometric components of shape variation between the taxa and more importantly between sexes within the taxa. We were able to show that the differences of shape between the taxa cannot be explained by allometric changes, as allometry explains only a small amount of total shape variation between the taxa, which was expected due to the fact that the taxa belong to separate subgenera. Between the sexes, on the other hand, allometry contributes largely to the variation, particularly in abdomen shape. However, the differences of head and pronotum shape between the sexes cannot be entirely explained in terms of allometric scaling. Our results indicate that allometry contributes largely to differences of body shape between the sexes, while differences between the taxa are influenced by other factors and processes.

Spurs, sexual dimorphism and reproductive maturity in Tasmanian echidnas (Tachyglossus aculeatus setosus)

We present data from an 18-year study of a wild population of Tasmanian echidnas, which show that the presence of spurs in an adult are a reliable indicator of sex, and that there is a slight but significant sexual dimorphism in size, with a male to female mass ratio of 1.1. Minimum age at first breeding in the wild for Tasmanian echidnas was 5 years, as has been found on Kangaroo Island, compared with 3 years in captive echidnas. It is often assumed that although the echidna is distributed throughout Australia, New Guinea and off-shore islands that all aspects of its basic biology are the same in all populations, but comparisons of our results with data from other populations suggest that there may be differences in size and sexual dimorphism.