Narrow versus broad: sexual dimorphism in the wing form of western European species of the subgenus Avaritia (Culicoides,Ceratopogonidae)

While wing form is known to differ between males and females of the genus Culicoides, detailed studies of sexual dimorphism are lacking. In this study, we analyze sex-specific differences in the wing form of 5 species of the subgenus Avaritia, using geometric morphometrics and comparative phylogenetic methods. Our results confirm the existence of marked sexual dimorphism in the wing form of the studied species and reveal for the first time that while there is a shared general pattern of sexual shape dimorphism within the subgenus, sexual size dimorphism, and particular features of sexual shape dimorphism differ among species. Sexual shape dimorphism was found to be poorly associated to size and the evolutionary history of the species. The tight association of sexual shape dimorphism with aspect ratio suggests that the shape of the wing is optimized for the type of flight of each sex, that is, dispersal flight in females versus aerobatic flight in males. Moreover, the fact that interspecific shape differences are greater and more strongly associated to aspect ratio in males than in females might be indicating that in males the selective pressures affecting flight performance characteristics are more heterogeneous and/or stronger than in females among the studied species.     

新疆塔里木盆地叶城沙蜥的两性异形

叶城沙蜥是一种主要分布于中国新疆南部地区的蜥蜴,通过测量和比较采自新疆塔里木盆地且末县叶城沙蜥的个体大小以及口宽等8个形态特征,研究了叶城沙蜥的两性异形。研究共采集叶城沙蜥62只,其中成年雌性个体27只,雄性个体35只。结果显示:(1)叶城沙蜥雌雄性成体的体长有显著差异,雄性大于雌性,表明叶城沙蜥具有雄性偏大的两性异形模式;(2)叶城沙蜥其他身体形态特征中尾长、腹长和头长3个特征有显著差异,其中雄性的尾长和头长大于雌性,而雌性的腹长大于雄性;(3)叶城沙蜥雌雄性个体间的口宽、眼间距等其他形态特征则没有显著差异。叶城沙蜥的两性异形表现为雄性大于雌性,并且雄性具有更大的头部和更长的尾部,雌性具有更长有腹部,这可能是雄性个体面临的性选择压力与雌性个体面临的繁殖压力共同作用的结果。     

Reproductive strategies in males of the world's southernmost lizards

Reproductive and life history patterns in reptiles are tightly related to the environmental conditions, so male reproductive cycles have been historically characterized as continuous, for tropical lizards, or seasonal, for temperate lizards. However, males of Liolaemus and Phymaturus lizards (Liolaemidae), from cold temperate climates of high altitudes or latitudes in Argentina and Chile, have developed a variety of reproductive cycles to coordinate with the short female reproductive season and to deal with the low frequency of reproductive females in the population. Using gonadal histology and morphological analysis, we describe the male reproductive biology, fat storage and sexual dimorphism of the viviparous lizards Liolaemus sarmientoi and Liolaemus magellanicus that inhabit an austral grass steppe at 51°S, in the southern limit of the American continent. Males of L. sarmientoi and L. magellanicus are reproductively available during the entire activity season of approximately 5 months. In addition, males of both species exhibit greater body sizes than females in morphological variables relevant in sexual selection. Meanwhile, females of both species exhibit larger inter‐limb length than conspecific males, which suggests fecundity selection to increase space for a larger litter size. The continuous sperm production throughout the activity season allows these liolaemids to mate at any time when females ovulate, representing a selective advantage to deal with the short activity season and the adversities of the cold environment they inhabit.     

Sexual size dimorphism in the lizard Oplurus cuvieri cuvieri (Squamata,Opluridae) from Madagascar

Sexual size dimorphism in the medium-sized lizard Oplurus cuvieri cuvieri, which is endemic to the dry deciduous forest of Madagascar, is presented. Adults are sexually dimorphic in body size, head size, and tail length. Males have a greater snout–vent length (SVL), head depth, head width, jaw length, tail length and body mass than females. Juvenile males have greater annual SVL growth rates than juvenile females, contributing to adult sexual size dimorphism. Moreover, the rates of increase in head depth and width differ significantly between the sexes after reaching maturity so that adult males have larger heads for a given body size than adult females. I suggest three proximate mechanisms that may cause sex-related differences in adult head size of O. c. cuvieri based on natural selection; to reduce intersexual food competition, sexual selection involving mate acquisition in males, and ontogenetic change of allometry to improve reproductive output in females.     

Numerical Methods in Marine Ecology

In order to elucidate the taxonomic status of the melanistic, girdled lizard, Cordylus cordylus niger, occurring in the Cape Peninsula and the Saldanha Bay area, South Africa, character variation among populations of the C. cordylus complex in the section of the Cape Province south of 32°3C latitude and west of 19°30' longitude was analysed. Variation for 92 external morphological characters at 54 localities was determined. Distinct patterns of interlocality variation were observed in only eight characters, but interestingly, these patterns were concordant in all eight cases. The observed patterns are interpreted as indicating that three phenotypic forms of the nominate species occur in the south-western Cape, namely a coastal melanistic form (= C. c. niger), occurring in insular and peninsular situations along the coast; a montane melanistic form occurring at relatively high altitudes along the western section of the Cape Fold Mountains; and the typical form (= C. c. cordylus), occurring commonly along the coastal lowlands, but also further inland at some places.     

Cordylus Minor: A valid species of South african lizard (Reptilia: Cordylidae)

The taxonomic status of Cordylus cordylus minor FitzSimons 1943 is reconsidered. An analysis of variation in external morphological characters shows minor and cordylus to be two non-overlapping sets of organisms. A phylogenetic study shows the minor-cordylus set to be non-monophyletic, leaving no option than to consider minor a separate species.     

Sexual dimorphism in jaw muscles of the Japanese sparrowhawk (Accipiter gularis)

Materials suitable for anatomical research of raptorial birds are rare. Bird‐eating raptors show distinct inter‐sexual differences in body size and parental roles. The large females catch larger prey and prepare small morsels to feed their young using their hooked beaks. Here, we investigated the architectural properties of different jaw muscles of the Japanese sparrowhawk (Accipiter gularis) and examined whether there is sexual dimorphism in their architectural design. The results showed that musculus depressor mandibulae, the opener of the lower jaw, was characterized by relatively long fascicle length, whereas musculus pterygoideus was characterized by its larger mass and physiological cross‐sectional area (PCSA) in both sexes. Females have the potential capacity to produce rapid and strong bites by their significantly longer fascicle length of M. depressor mandibulae and larger mass and PCSA of M. pterygoideus. For body size‐matched gender, jaw muscles of males had fibres of relatively longer length than females, enabling greater velocity and excursion. Architectural characteristics of jaw muscles, together with the absolute dimorphism (the fascicle length of M. depressor mandibulae, the muscle mass and PCSA of M. pterygoideus) and relative dimorphism in the muscle mass of M. pterygoideus, reflect dietary difference and asymmetric parental roles between the sexes.     

Faecal analysis suggests generalist diets in three species of Western Cape cordylids

Climate has been proposed as an explanation for the present-day distribution of closely-related melanistic and non-melanistic cordylid species in the southwestern Cape of South Africa. However, diet may also contribute towards shaping geographic distributions. We present preliminary data on diet composition based on analyses of faecal pellets of Cordylus cordylus (non-melanistic), C. niger (melanistic) and C. oelofseni (melanistic). Coleoptera were the most common prey ingested both in summer and early spring for all species, followed by Hymenoptera for all species in summer. The overlap in other arthropod taxa ingested was low across species and seasons, suggesting an opportunistic component to their foraging behaviour.We distinguished plant matter in faecal samples of all species in all seasons, reflecting either voluntary or accidental ingestion. The results of this study suggest that the generalist diets of these cordylid species should not constrain their distributions despite the common preference for coleopterans.     

Ecology of Wahlberg’s velvet gecko,Homopholis wahlbergii,in southern Africa

We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout–vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85mmSVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females reproduce every year once they reach sexual maturity. Egg size ranged from 17–19mm long. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL. Virtually all males larger than this size displayed at least semi-turgid testes and most adult male testes were at least semi-turgid for much of the year. The only significant decrease in testicular activity was in mid-winter (June–August), thus, spermatogenesis is closely tied to female follicular development and ovulation. Velvet geckos are largely insectivorous (92%) and feed on a broad spectrum of prey. Their diet was dominated both numerically (34%) and volumetrically (22%) by beetles. Lepidoptera were the next most important prey category, suggesting that they exploit both terrestrial and flying invertebrates. They are unusual among lizards because they feed on millipedes. Males and females had very similar diets which may be explained by their lack of sexual dimorphism, although females tended to eat a greater volume of prey. Interestingly, less than half (37%) of the lizards examined contained prey items, suggesting that most individuals were not in positive energy balance. We also found evidence of prey size selection as a function of gape size, such that larger geckos took advantage of larger prey items.     

Identification of genomic regions that exhibit sexual dimorphism for size and muscularity in cattle

Sexual dimorphism, the phenomenon whereby males and females of the same species are distinctive in some aspect of appearance or size, has previously been documented in cattle for traits such as growth rate and carcass merit using a quantitative genetics approach. No previous study in cattle has attempted to document sexual dimorphism at a genome level; therefore, the objective of the present study was to determine whether genomic regions associated with size and muscularity in cattle exhibited signs of sexual dimorphism. Analyses were undertaken on 10 linear-type traits that describe the muscular and skeletal characteristics of both males and females of five beef cattle breeds: 1,444 Angus (AA), 6,433 Charolais (CH), 1,129 Hereford, 8,745 Limousin (LM), and 1,698 Simmental. Genome-wide association analyses were undertaken using imputed whole-genome sequence data for each sex separately by breed. For each single-nucleotide polymorphism (SNP) that was segregating in both sexes, the difference between the allele substitution effect sizes for each sex, in each breed separately, was calculated. Suggestively (P ≤ 1 × 10⁻⁵) sexually dimorphic SNPs that were segregating in both males and females were detected for all traits in all breeds, although the location of these SNPs differed by both trait and breed. Significantly (P ≤ 1 × 10⁻⁸) dimorphic SNPs were detected in just three traits in the AA, seven traits in the CH, and three traits in the LM. The vast majority of all segregating autosomal SNPs (86% in AA to 94% in LM) had the same minor allele in both males and females. Differences (P ≤ 0.05) in allele frequencies between the sexes were observed for between 36% (LM) and 66% (AA) of the total autosomal SNPs that were segregating in both sexes. Dimorphic SNPs were located within a number of genes related to muscularity and/or size including the NAB1, COL5A2, and IWS1 genes on BTA2 that are located close to, and thought to be co-inherited with, the MSTN gene. Overall, sexual dimorphism exists in cattle at the genome level, but it is not consistent by either trait or breed.     

Different patterns in the histology and autofluorescence of the Harderian glands of the Syrian Hamster, rat, mouse, Mongolian gerbil and guinea pig

The purpose of this study was to compare the natural fluorescence in the Harderian glands of the Syrian hamster, rat, mouse, Mongolian gerbil and guinea pig (both sexes). For each species, 10 animals (five males and five females) were used. Histological autofluorescence studies were performed using a fluorescence microscope (450-490 nm filter). Two different types of fluorescent cells were observed in both hamster (type AFI high intensity and type AFII, low fluorescence) and rat (type AFI, low fluorescence and type AFII, high fluorescence) Harderian glands. The fluorescence was basally located in all mice cells, whereas it was observed near the epithelial cell nuclei in the Mongolian gerbil (occupying two-thirds and one-third of the cells in males and females, respectively). A high intensity of fluorescence was present throughout the acinar cells in the guinea pig. The patterns of fluorescence identified exhibited a sexual dimorphism in all species studied. These results demonstrate that the Harderian glands of the animal species examined exhibit a variety of histological autofluorescence patterns.     

Sexual Dimorphism of Endocranial,Facial and Limb Measurements in the Yellow Baboon (Papio cynocephalus)

The present study focused on the sexual dimorphism of yellow baboon (Papio cynocephalus) to clarify its relationship with social behaviour. The degree of sexual dimorphism in the endocranial volume is the lowest among the investigated measurements. Among the facial measurements, the degree value of sexual dimorphism was the maximum (38.4%) for palate length and the minimum for palate breadth at the upper second molar (M2) (16.8%). Reduced major axis (RMA) regression analysis indicated that most positive allometry in relation to body mass was barely shown in the endocranial volume, palate length, palate breadth at M2 and mandibular ramal width. On the other hand, most negative allometry in relation to body mass was barely indicated in the bizygomatic breadth, skull length, humeral length and femoral length. The plate breadth at M2 in males was smaller than that in females in equivalent to body mass. The results of the present study suggest that more males have longer pointed muzzles than females, which is considered to create an impressive view of large canine teeth. This contributes to display among males and agonistic encounters rather than to necessity of increased facial size due to larger body size or dietary influences.     

Changes in body and organ weights of Japanese quail selected for 6‐week body weight 1

Three populations of Japanese quail, selected over 13 generations for increased body weight, a randomly selected base population and reciprocal backcrosses of selected lines to the control were studied. Live body weight and weights of liver, testes, oviducts and carcasses were obtained to assess the effects of selection.

At 6 weeks of age a 20 g. difference in live body weight existed between selected line and base population. Sexual dimorphism in live body weight in favour of females appeared at 3 weeks of age and increased with age. A 5 g. difference in 6‐week body weight between female backcross progeny from sires from selected lines and those sired by males from the base population suggested an influence of sex‐linked genes. At 8 weeks of age the weight of females of both reciprocal back‐cross types significantly exceeded the average of females from the selected lines suggesting that female reproductive organ weight had increased under selection as well as heterosis. Carcass weight of selected females was lower than for corresponding males, a reversal of the sexual dimorphism displayed by the controls.

Reciprocal differences in liver weight between backcross females, but not males, suggested an effect of sex‐linked genes.

Testis as well as oviduct weights of quail from selected lines were substantially greater than from controls.     

A pilot study of sexual dimorphism in the head morphology of domestic dogs

The dog (Canis lupus familiaris) displays more morphological diversity than any other species. It is a direct descendant of the gray wolf (Canis lupus), but shows remarkable behavioral and morphological differences. It has been suggested that differences in skull shape that relate to brain shape and retinal ganglion cell distribution may predict behavioral differences. The aim of this pilot study was to assess head morphology in common breeds for evidence of sexual dimorphism in head length, head width, and the ratio of the 2: cephalic index (CI). When males of 80 breeds studied were compared with females, sexual dimorphism (differences in a t-test at the level of P < 0.01) emerged for head length in 5 breeds, for head width in 10 breeds and in CI for 2 breeds. The 2 breeds that showed sexual dimorphism in CI showed no difference (at the level of P < 0.01) in either length or width. These results suggest that all 3 types of dimorphism in head morphometrics must be considered separately. Although the longer and wider heads in males may be predicted because, within a breed, they are expected to be generally bigger animals, the sexual dimorphism in CI is of interest. It may belie differences in brain shape and even predict differences in health, welfare, and behavior.     

Elytron length and sexual dimorphism in Zonocerus elegans (Thunb.), (Orthoptera: Pyrgomorphidae)

Adults of the African pyrgomorphid grasshopper, Zonocerus elegans Thunberg, exhibit strong alar polymorphism, especially in the male sex, with wings either vestigial or fully developed. Analysis of body and elytron lengths of about 400 insects revealed sexual dimorphism, females being larger than males, and showed a bimodal distribution for wing length. The difference in average wing length between long-winged and short-winged forms was 14 mm. Since the two distributions (short and long) do not overlap, they would correspond closely to the subsidiary infra-subspecific categories f. brachyptera and f. macroptera, respectively, although even wings of the lower macroptera range seem to be vestigial, i.e. imperfectly developed and useless for flight.     

The heritability and genetic correlations of sexual dimorphism for 10-week weight in poultry

The quantitative genetic parameters of sexual dimorphism for 10‐week body weight and its genetic correlation with egg weight and egg number was determined in an unselected population of White Leghorns. The genetic correlation between male and female weights was 0.586 indicating considerable genotype‐sex interaction. The heritability of the difference in weight between males and females was 0.267.

The genetic correlations of the difference in weight between sexes with body weights of males and females were 0.690 and 0.06 respectively. There was evidence of a fairly high positive genetic correlation between egg weight and sexual dimorphism. Egg number to 44 weeks of age and sexual dimorphism were positively correlated but the magnitude of the correlation coefficient was small.     

An integrated Assessment of a group with complex systematics: the Iberomaghrebian lizard genus Podarcis (Squamata,Lacertidae)

A critical review of the evolutionary biology of Iberian and North African lizard members of the genus Podarcis (Lacertidae) based on phylogeny, phylogeography, morphometrics, behavior, ecology and physiology is presented. The Iberomaghrebian region is inhabited by at least 12 different evolutionary lineages that group into a monophyletic clade (except Podarcis muralis). In contrast to the current taxonomy, the saxicolous ‘Podarcis hispanica’ is paraphyletic with respect to Podarcis bocagei and Podarcis carbonelli, two currently recognized species. Nodes in the phylogenetic tree are deep, resulting from old divergences, clearly preceding the Pleistocene. Nevertheless, more recent range changes as a result of glaciations are also evident. The most plausible evolutionary scenario for this group indicates both vicariant and dispersal events. Although parapatry between lineages is the rule, sympatry and even syntopy are frequent, but usually between ground‐dwelling and saxicolous forms. Contacts between forms with similar habitat use are rare and local. Morphological distinctiveness between lineages has been demonstrated, indicating historical constraints. However, other characters have repeatedly evolved under similar environmental pressures independently of the evolutionary lineage. Strong sexual dimorphism derives from sexual selection and is attained before sexual maturity, although developmental restrictions exist. Variation between populations is also important and derives from local variation in both natural (habitat, climate) and sexual (density) selective pressures. Evidence for short‐term changes has already been found, particularly in insular populations. Reproductive isolation between syntopic forms and partner recognition are based on male—male competition and on visual and chemical recognition of females by conspecific males. Despite this ancient diversification, most forms maintain a degree of reproductive compatibility. Hybridisation may occur, but is limited, and there is evidence of selection against hybrids. The ecological analysis presented here does not support exploitative competition, but rather behavioral interference between forms. Ecomorph classification of lineages suggests character displacement between those with extensive range overlap. Finally, a critical assessment of the specific status of all lineages is provided and directions for further research are suggested.     

Flight performance and wing morphology in the bat Carollia perspicillata: biophysical models and energetics

Studies on functional performance are important to understand the processes responsible for the evolution of diversity. Morphological trait variation within species influences the energetic cost of locomotion and impacts life history traits, with ecological and evolutionary consequences. This study examined wing morphology correlates of flight performance measured by energetic expenditure in the Seba's short-tailed bat, Carollia perspicillata. In the flight experiments, nature caught bats (59 females, 57 males) were allowed to fly for 3 min in a room. After each flight, thermographic images were taken to measure body temperature, and biophysical models were used to calculate sensible heat loss as a measure of energetic expenditure. Wing morphological traits were measured for each individual and associated with heat loss and power required to fly on performance surfaces. Wing morphological traits explained 7–10% of flight energetic cost, and morphologies with the best performance would save the energy equivalent to 9–30% of total daily requirements. The optimal performance areas within the C. perspicillata morphospace were consistent with predicted selection trends from the literature. A trade-off between demands for flight speed and maneuverability was observed. Wing loading and camber presented sexual dimorphism. These morphological differences are likely associated with more economical but less maneuverable flight in females, leading them to fly more often in open areas along the forest edge. Our findings demonstrate how small scale changes in wing morphology can affect life history strategies and fitness.