Sexual size dimorphism and morphometric sexing in a North African population of Laughing Doves Spilopelia senegalensis

Like the majority of Columbiformes, the Laughing Dove Spilopelia senegalensis is sexually monomorphic in plumage, but seems to be slightly dimorphic in size. However, due to the lack of studies little is known about the sexual size dimorphism in this species. In this work, we used morphometric data on a sample of 61 Laughing Doves from southern Tunisia, and sexed using a DNA-based method, to assess size differences between males and females and to determine a discriminant function useful for sex identification. The results showed that wing length was the most dimorphic trait, which could be due to the effects of sexual selection. The best function for the discrimination between sexes included wing length and head length, which is comparable with findings on other dove species. This discriminant function accurately classified 89% of birds, providing a rapid and accurate tool for sex identification in the studied population. Further data from different populations are needed for firmer conclusions about the extent of sexual size dimorphism and the reliability of the morphometric sexing approach in this dove species.     

Disturbance-dependent Yellow-legged Gull (Larus michahellis) predation on Larid chicks decreases with chick age

Predation is one of the key factors shaping the dynamics of animal populations. In birds, nest loss due to predation can be a significant cause of low reproductive success. Ground-nesting birds are among the bird groups most susceptible to predation, mainly because their nests are easily accessible to a broad suite of potential predators. For these birds, anthropogenic disturbances can generate changes in nest predation risk by altering their antipredator behaviour and also by altering the behaviour of the predator species, i.e. the predator becoming much more aware of predation opportunities due to frequent disturbances and/or motivated to repeat predation attempts when some are successful. To date, most previous studies investigating this have focused on a single effect, either predation or disturbance, on chick survival. It remains unknown how the risk of predation with and without disturbance varies with chick age. In this study, we used behavioural observations to assess how the interaction between predators and disturbance affects predation risk in chicks and how this interacts with chick age. Specifically, we investigated the effect of disturbance caused by humans and stray dogs on the predation of Slender-billed Gull Chroicocephalus genei chicks by Yellow-legged Gulls Larus michahellis, and whether this depended on the age of the chicks. Our results revealed that disturbance had a significant positive effect on predation measures of Slender-billed Gull chicks by Yellow-legged Gulls, but that this effect was mediated both by disturbance type and the age of chicks. Stray dogs entering the colony had a stronger disturbance effect on chicks than passing humans, increasing predation risk by Yellow-legged Gulls. Our results also showed that chick age interacts with disturbance type to determine the predation risk. This is probably mediated by chicks' capacity to escape predation by gathering in a single large crèche that runs into the water when disturbed. To preserve Slender-billed Gull colonies in one of its few remaining breeding sites in Tunisia, and as gulls tend to react even when the disturbance occurs relatively far from the colonies, it is crucial to (1) restrict human access to dikes and islets where large colonies breed and (2) construct artificial islets attractive to gulls and inaccessible to stray dogs.     

Annual reproductive cycle,spawning periodicity and sexual maturity of false scad Caranx rhonchus (Geoffroy Saint‐Hilaire, 1817) (Pisces,Carangidae) from the South‐Eastern Mediterranean (Gulf of Gabès,Tunisia)

The reproductive biology of Caranx rhonchus (Geoffroy Saint‐Hilaire, 1817) (Pisces, Carangidae) was studied in the Gulf of Gabès (Mediterranean Sea) from June 2004 to May 2006. Of 1313 individuals examined, 668 were females (50.9%) and 645 were males (49.1%). The overall sex ratio did not deviate significantly in favour of females (♀ : ♂ = 1.04 : 1). Monthly changes in the Gonado–Somatic Index (GSI) showed a rapid increase from May to June and an extended very high level from June to September (4.43–3.47% for females and 3.35–2.61% for males), before declining sharply in October (down to 2.02% for females and 0.57% for males). The gametogenesis activity began with a pre‐maturation phase from March to May, followed by a ripe‐spawning phase from June to September. From the last days of July to the end of October, the gonads were in the spent and post‐spawning stages. From November to early May, gonads were in the resting stages. The size at which 50% of the population reached sexual maturity was not significantly different between males and females :  males attained sexual maturity at fork length FL₅₀ = 161.20 ± 0.37 mm (n = 262), whereas females attained maturity at FL₅₀ = 160.70 ± 0.23 mm (n = 296). The age of maturity for both sexes occurred at 2.1 years.     

Opportunistic feeding responses of the Yellow-legged Gull Larus michahellis to accessibility of refuse dumps

Capsule The gulls adjust their diet composition and diversity according to refuse dump accessibility.

Aims To examine the influence of the accessibility of open-air refuse dumps on the pre-laying diet of the adult Yellow-legged Gull.

Methods We studied six colonies settled on six rocky islands off the southeastern coast of France. A comparative study of the diet of breeding adults from the six colonies was made through pellet analysis (a total of 848 pellets). We determined the main foraging habitat used (refuse dumps, terrestrial habitats, marine habitat) and the number of foraging habitats used simultaneously (one, two or three), from which we deduced the mean diet diversity.

Results Refuse dumps were consistently the main foraging habitat (evidence in 53–74% of pellets) for the six colonies, even when refuse dump accessibility was low. The majority of pellets contained materials from two simultaneous foraging habitats (evidence in 50–64% of pellets). We demonstrated the influence of a gradient of refuse dump accessibility in terms of adjustment of the pre-laying adult's diet. Indeed, high refuse dump accessibility leads to a poorly diversified diet dominated by refuse. In contrast, when refuse dump accessibility is low, Yellow-legged Gulls broaden their trophic niche, with an increased exploitation of alternative foraging habitats, such as terrestrial habitats.

Conclusion These results show the species' opportunistic feeding and high adaptability, two parameters which need to be known to foresee the consequences on population dynamics, feeding and predatory behaviour of a sudden and severe food shortage, for example due to closure of open-air refuse dumps.     

Multiple discriminant function analysis of sex and race in the postcranial skeleton

Terry Collection femora and innominates of 260 American Whites and Blacks (65 males and 65 females of each race) were analyzed by multiple discriminant function analysis. A stepwise procedure produced three optimal discriminant functions using 15 of our 32 measurements. These functions correctly identified 95% of the sample. The first two-one for sex and one for race-are statistically and biologically significant and form the basis of our analysis. The sexing function manifested both size and shape elements. Prominent among the former was joint size--acetabular diameter and epicondylar diameter of the femur. The shape elements included form of the greater sciatic notch and of the inferomedial aspect of the pubic body. The racing function highlighted a pattern of greater innominate dimensions, exclusive of the acetabular joint, in Whites. This was in contrast to the greater length of the Black femur. Overall, the function seems to express the established differences between the races in the ratio of lower limb length to torso length. While these functions have been applied successfully to forensic cases with confirmed identifications, questions regarding the breadth of applicability of discriminant functions make it desirable to validate our results on new material from the Terry and other collections.     

GEOGRAPHICAL VARIATION IN METRIC SKULL CHARACTERS AMONG PROPOSED SUBPOPULATIONS AND STOCKS OF HARBOR PORPOISE, PHOCOENA PHOCOENA, IN THE WESTERN NORTH ATLANTIC

A total of 433 skulls of harbor porpoises, Phocoena phocoena , were examined to evaluate geographical variation within the western North Atlantic, using analysis of covariance and discriminant analysis based on 45 measurements of skull components. The relationship between condylobasal length and body length was sigmoid in both sexes. Condylobasal length is generally less in adult males than in adult females.
Despite some overlap, morphological differences between different regions and even adjacent local stocks could be recognized by ANCOVA and discriminant analysis. The percentage of correct classification by discriminant functions was 65.2% for the four regional samples: (1) North Canadian Atlantic (which includes Gulf of St. Lawrence and Newfoundland), (2) Bay of Fundy, (3) Gulf of Maine-New York, and (4) Maryland-South Carolina. It was 65.9% for the four local geographical areas (10s of km) within the Bay of Fundy; Quoddy-region porpoises revealed a closer relationship with the southwestern Nova Scotia population than with other adjacent stocks. The results at this level imply that gene flow is restricted to some degree even among closely adjacent geographical units. Management of this species should aim, therefore, for conservation of a variety of local stocks.     

The discriminant power of biometrics for sex determination in European Bee-eaters Merops apiaster

ABSTRACT

Capsule A combination of several biometric measures enables the reliable sexing of the European Bee-eater Merops apiaster, a species with subtle sex differences in plumage and morphometry.

Aims To explore variation in biometrics and their suitability to discriminate sex in adult European Bee-eaters Merops apiaster.

Methods We sampled populations of a long-distance migratory species with low sexual size dimorphism, the European Bee-eater Merops apiaster, from colonies in western Iberia (Portugal) and Central Europe (Germany) to investigate body size variation and derive population-specific and general sex discriminant functions.

Results Overall, male Bee-eaters were larger than females while Bee-eaters from Germany and Portugal did not differ in size, except for primary length and tail length. The best single measurement to discriminate sex was wing length for Portuguese birds and tail tip length for German birds, as in the combined dataset. Multivariate discriminant functions of head-bill, wing and tail tip lengths provided the highest discriminant accuracy, discriminating sex for 91% of the birds from Portugal, 96% from Germany and 94% when using the combined dataset. Nonetheless, the discriminant accuracy remained high in the functions using only two variables for Portugal (head-bill and tail tip 91%, head-bill and wing 88%, wing and tail tip 88%), Germany (head-bill and tail tip 95%, wing and tail tip 97%) and in the combined dataset (head-bill and tail tip 92%, wing and tail tip 93%).

Conclusions Population specific discriminant functions allow sexing of European Bee-eaters by morphometry with high degree of accuracy at least for Iberia and Central European populations. Such discriminant functions can be used to assign the sex of adult Bee-eaters reliably and swiftly while the bird is still in the hand, highlighting the potential of these functions for rapidly sexing species with low degrees of sexual size and plumage dimorphism.     

Comparative response to citrus foliage and citrus fruit odour by wild and mass-reared sterile Mediterranean fruit fly males of a genetic sexing strain

In greenhouse behavioural assessments conducted at Seibersdorf, Austria that allowed flies the choice of different types of potted host trees and plants, it was found that mature laboratory mass-reared Mediterranean fruit fly males, Ceratitis capitata (Wied), (Dipt. Tephritidae), strain Vienna-42 (temperature-sensitive lethal genetic sexing strain) showed the same preference for orange foliage, over other plants types and parts, as wild males. They aggregated in leks, released pheromone, and courted approaching females almost exclusively on orange foliage. Even though a number of other trees and plants were available to Vienna-42 males, less than 1% of these sexual activities occurred on the foliage or other plant parts of non-Citrus trees and not a single mating occurred there. In choice tests carried out in Chios, Greece in large field cages housing naturally planted orange trees, it was determined that mature and sterile Mediterranean fruit fly males of the same sexing strain responded to the odour emanating from the flavedo (due to superficial cuts made in the fruit peel containing the oil glands) of ripening sweet, sour oranges and lemons, in a similar intensity, order of fruit preference and time of day as did mature males of the local wild population. Males of both strains were frequently observed contacting with their mouth parts the oils exuding from the cuts made in the flavedo of the orange peel, or exhibiting homosexual activity on, or near the cuts. The results show that mass-reared, sterile males of the Vienna-42, genetic sexing strain behave in a comparable way to wild males in an important component of habitat location (odour of host foliage and host fruit) and hence are competitive with them in these respects. None of the standard international quality control tests for sterile Mediterranean fruit flies evaluates this important habitat location behaviour, which is a prerequisite for the successful encounter of the sexes in a sterile release programme.     

The role of mobile consumers in lake nutrient cycles: a brief review

Spawning habitats of anchovy Engraulis encrasicolus and sardinella Sardinella aurita were investigated in the Gulf of Gabès by means of two surveys carried out during the summer of 2005 and 2009. The spatial patterns of early developmental stages were analyzed through Lloyd’s patchiness index, single quotient analyses, and principal component analyses. The results showed that Gulf of Gabès is an important area for anchovy and sardinella spawning. Within this area, anchovy and sardinella showed preference for the warmest waters to spawn. The main spawning areas for anchovy were located in the inner parts of the Gulf, and a secondary spawning area was observed offshore. Contrastingly, the main spawning ground of sardinella was found in the center of the Gulf. In both years, early larvae of anchovy showed a greater degree of aggregation than that of sardinella. The developmental stages of both species showed low spatial overlap, indicating that the spawning habitats of these species are spatially differentiated in the Gulf of Gabès.     

Effects of testosterone implants on pair behaviour during incubation in the Yellow-legged Gull Larus cachinnans

The Yellow-legged Gull Larus cachinnans is monogamous with bi-parental incubation. In this study, the effects of high levels of plasma testosterone in male Yellow-legged Gulls during the incubation period were analysed. Free-living male gulls were implanted with testosterone (T-males), and their sexual behaviour within the pair was observed and compared with that of control pairs. Egg temperatures, length of incubation and hatching success were also analysed. T-males and their mates displayed more sexual behaviour than the controls. T-males engaged in mounting behaviour with their mates, whereas control males did not. Proportionally less time was spent incubating (in relation to time present in the colony) by T-males than control males. However, the mates of T-males did not spend more time incubating than control females to compensate for male neglect, although they did spend more time on the territory. Egg temperature in T-male nests was significantly lower than in control nests, but no significant difference in the length of incubation or hatching success between the two groups was found. In birds, the effects of high testosterone levels on male behaviour during incubation have only been analysed in a polyandrous species whose females usually do not contribute to incubation. The present results thus suggest that those males of a monogamous species with bi-parental incubation that sustain high testosterone levels after laying, thus reducing their contributions to incubation, will be confronted with a lack of compensation from their mates during incubation. Finally, this lack of female compensation seems to be mediated by behavioural interactions with the male rather than by her absence from the colony.     

Common dolphinfish,Coryphaena hippurus,spawn at their easternmost Atlantic range adjacent to the Mediterranean Sea

This study provides sound evidence of the spawning activity of common dolphinfish (Coryphaena hippurus) in the Gulf of Cadiz (southwest Spain) during summer months. Along with waters off Côte d'Ivoire, this area adjacent to the Mediterranean Sea is the easternmost Atlantic spawning ground documented for the species. All the fish analysed (5 males and 15 females) were at spawning stage, except the smallest female (61.5 cm in fork length), which might not have yet reached sexual maturation. The oceanographic conditions during the samplings were similar to those occurring during the peak spawning season in the Gulf of Mexico. The study results are consistent with recent genetic studies indicating differentiation between Mediterranean and Atlantic dolphinfish populations, with the Strait of Gibraltar representing a boundary between two distinct reproductive units. The present results may contribute to improve the understanding of the dynamics of dolphinfish population and the management of eastern Atlantic and Mediterranean stocks.     

Genetic sexing through the use of Y-linked transgenes

Sterile insect technique (SIT)-based pest control programs rely on the mass release of sterile insects to reduce the wild target population. In many cases, it is desirable to release only males. Sterile females may cause damage, e.g., disease transmission by mosquitoes or crop damage via oviposition by the Mediterranean fruit fly (Medfly). Also, sterile females may decrease the effectiveness of released males by distracting them from seeking out wild females. To eliminate females from the release population, a suitable sexual dimorphism is required. For several pest species, genetic sexing strains have been constructed in which such a dimorphism has been induced by genetics. Classical strains were based on the translocation to the Y chromosome of a selectable marker, which is therefore expressed only in males. Recently, several prototype strains have been constructed using sex-specific expression of markers or conditional lethal genes from autosomal insertions of transgenes. Here, we describe a novel genetic sexing strategy based on the use of Y-linked transgenes expressing fluorescent proteins. We demonstrate the feasibility of this strategy in a major pest species, Ceratitis capitata (Wiedemann), and discuss the advantages and disadvantages relative to other genetic sexing methods and potential applicability to other species.     

Geographical variation in the yellow‐legged gull: introgression or convergence from the herring gull?

Yellow-legged gulls Larus michahellis from the Atlantic Iberian coast exhibit some phenotypic similarities with the herring gull L. argentatus from Western Europe. To assess this phenomenon and its possible origin, we compared Mediterranean yellow-legged gulls, Atlantic Iberian yellow-legged gulls and herring gulls for several phenotypic traits (morphology, plumage), and used genetic data to determine the evolutionary history of the Atlantic Iberian yellow-legged gulls. Data from mitochondrial cytochrome b gene and microsatellite loci clearly indicate that Atlantic Iberian gulls are closely related to Mediterranean yellow-legged gulls, and do not show stronger signs of introgression with herring gulls relative to other populations of yellow-legged gulls. Atlantic Iberian yellow-legged gulls are more similar to herring gulls in body size and shape than to other yellow-legged gulls populations, but not in mantle colour and wing-tip pattern. Body size and other phenotypic and life history similarities with the herring gull ( L. argentatus argenteus ) such as voice, winter plumage and breeding phenology, previously described in several studies, might thus be interpreted as convergent characters. Within the yellow-legged gull, the high F _st-values obtained from four nuclear microsatellite loci indicate substantial population structure and reduced levels of gene flow between gull populations in Mediterranean France and Atlantic Iberia. Differences among these populations in breeding phenology and migration patterns, likely resulting from different local selection pressures, might contribute to this low level of gene flow.     

<Emphasis Type="Italic">Pseudodiplectanum syrticum</Emphasis> n. sp. (Monogenea: Diplectanidae), a parasite of <Emphasis Type="Italic">Synapturichthys kleinii</Emphasis> (Teleostei: Soleidae) from off Tunisia

Pseudodiplectanum syrticum n. sp. (Monogenea: Diplectanidae) is described from the gills of Synapturichthys kleinii (Risso) collected from the Gulf of Gabès in the Mediterranean Sea off Tunisia. The new species differs from the congeneric species by the morphology of the penis and vagina. It resembles the Mediterranean species P. kearni Vala, Lopez-Roman & Boudaoud, 1980 from Solea vulgaris Quensel and P. gibsoni Oliver, 1987 from Michrochirus variegatus (Donovan) in its tubular penis, but it differs from these two species by having a vagina with a long tube presenting two loops and a male copulatory organ ending in a curved point. It also differs in the morphology and size of the transverse bars of the haptor. In P. syrticum the ventral transverse bar and dorso-lateral bars are longer than those of P. gibsoni (114 vs 69.5-89 microm and 48 vs 33-44 microm, respectively).     

Molecular evidence for introgressive hybridization in New Zealand masked gulls

We used mitochondrial DNA (mtDNA) gene sequences and nuclear microsatellite loci to investigate the extent and outcome of hybridization between the Black-billed Gull Chroicocephalus bulleri and the Red-billed Gull Chroicocephalus novaehollandiae scopulinus in New Zealand. Six of 26 sampled Black-billed Gulls possessed mtDNA typical of Red-billed Gulls, but allele frequencies at six polymorphic microsatellites provided little evidence of mixed ancestry expected in very recent hybrids. None of the Red-billed Gulls sampled from different colonies possessed Black-billed Gull mtDNA expected in the reciprocal cross, suggesting that hybridization in the two species typically occurs between female Red-billed Gulls and Black-billed Gull males. The lack of any hybrid signal in the nuclear loci indicates that there has been extensive backcrossing with Black-billed Gulls, effectively diluting the Red-billed Gull nuclear DNA contribution. Divergence of Red-billed Gulls and Black-billed Gulls occurred approximately 250 000 years ago, indicating that unsorted ancestral polymorphism is an unlikely alternative to hybridization. Comparing demographic models within an approximate Bayesian computation (ABC) framework, we confirm that the observed patterns cannot result from incomplete lineage sorting. Using an ABC random forest approach, we determined that the most likely model explaining the data is a recent introgression scenario, whereby unidirectional gene flow is re-established following a period of strict isolation. The ability of Black-billed and Red-billed Gulls to successfully interbreed shows that despite significant differentiation (F_ST > 0.3), there has been insufficient time for the two species to develop complete reproductive isolation. The apparent one-way transfer of Red-billed Gull mtDNA into Black-billed Gulls and extensive backcrossing argues against cytoplasmic–nuclear genome incompatibilities between the two species. We hypothesize that the specific mate recognition system cued on colours of soft parts normally functions to prevent hybridization, but that it can break down under demographic conditions where there is a shortage of available mates and a surplus of females in the Red-billed Gull population. The high incidence of introgression in Black-billed Gulls conflicts with field observations that interbreeding is extremely rare.     

Mate choice by wild and mass‐reared females of the Mediterranean fruit fly

The sterile insect technique (SIT) is used to control Mediterranean fruit fly, Ceratitis capitata (Wiedemann), but its effectiveness is limited by low sexual competitiveness of mass‐reared males. This study investigated whether wild and mass‐reared [from a temperature sensitive lethal (tsl) genetic sexing strain] females display similar mate preferences and thus exert similar selective forces on the evolution of male courtship behaviour. Wild females preferred wild males over tsl males, whereas tsl females mated indiscriminately. The probability that mounting resulted in copulation was related to the duration of pre‐mount courtship for wild females, and wild males performed longer courtships than tsl males. Copulation occurred independently of courtship duration in tsl females. Counter to the aim of the SIT, female choice by tsl females appears to promote the evolution of male behaviour disfavoured by wild females.     

Female philopatry in coastal basins and male dispersion across the North Atlantic in a highly mobile marine species, the sperm whale (Physeter macrocephalus)

The mechanisms that determine population structure in highly mobile marine species are poorly understood, but useful towards understanding the evolution of diversity, and essential for effective conservation and management. In this study, we compare putative sperm whale populations located in the Gulf of Mexico, western North Atlantic, Mediterranean Sea and North Sea using mtDNA control region sequence data and 16 polymorphic microsatellite loci. The Gulf of Mexico, western North Atlantic and North Sea populations each possessed similar low levels of haplotype and nucleotide diversity at the mtDNA locus, while the Mediterranean Sea population showed no detectable mtDNA diversity. Mitochondrial DNA results showed significant differentiation between all populations, while microsatellites showed significant differentiation only for comparisons with the Mediterranean Sea, and at a much lower level than seen for mtDNA. Samples from either side of the North Atlantic in coastal waters showed no differentiation for mtDNA, while North Atlantic samples from just outside the Gulf of Mexico (the western North Atlantic sample) were highly differentiated from samples within the Gulf at this locus. Our analyses indicate a previously unknown fidelity of females to coastal basins either side of the North Atlantic, and suggest the movement of males among these populations for breeding.     

Karyological studies inCoris julis (Pisces,Labridae)

In the present investigation the diploid number 2n=48 (NF=58) has been determined for females, primary males, and secondary males ofCoris julis from the Gulf of Palermo. Differentiated sex chromosomes have not been observed in the population under study.     

Demographic impact of landfill closure on a resident opportunistic gull

The management of mixed municipal waste can have an impact on wildlife and ecosystems. Previous studies have investigated how opportunistic species like gulls can react very fast to new landfills; however, the impact of landfill closure on bird populations is less investigated. Yet, there is a need to understand how fast and to what extent, animal populations can be adapted to new scenarios where the waste will not be deposited in landfill sites anymore. The aim is to determine the influence of landfill closures on apparent survival of a resident Yellow-legged Gull (Larus michahellis) population, used as a model species showing short-distance foraging movements, and with a high dependence on local food subsidies. Complementarily, we built some basic population growth models in order to determine how potential changes in survival (before/after landfill closure) will impact on population growth rate. Using a data set of 4,437 Yellow-legged Gull chicks ringed in four colonies over a period of 13 years, we obtained evidence supporting that the apparent survival was affected by landfill closure, especially if the landfill was located within a buffer of 10 km around the colony. Landfill closure affected the survival of first-year gulls (with a mean decrease of ~ 0.5–0.36), but not of older birds. Consequently, we did not detect a remarkable effect of landfill closures on population growth rate, probably due to the lack of effect on adult survival rates except for one of the surveyed colonies, where we found an annual decline of 7%.     

Sexing Wrens Troglodytes troglodytes indigenus using morphological measurements and discriminant analysis

Within the breeding population of a deciduous woodland, male Wrens averaged slightly larger than females in wing length, foot length, head plus bill length and body mass. First-year and older birds were similar for three of these morphometric variables, but the first-year group were shorter-winged than the older birds (by 3%). Despite this, wing length still proved to be a useful discriminator of sex when the data were pooled for all ages (74% of males exceeding the maximum female value of 49.8 mm). A discriminant function utilizing wing length and head plus bill length correctly sexed 96% of individuals in the sample from which it was derived (n = 49 males, 36 females). This function was converted into a predictive equation for the probability of an unknown case being male, and a plot of wing length against head plus bill length along with probability contours which enabled the sexing of unknown cases without the need for calculations. Measurements of the morphological variables investigated were found to be highly repeatable for a single worker, with the exception of body mass which differed substantially between the sexes but which was only moderately repeatable. The methods provided should prove valuable for sexing British mainland Troglodytes troglodytes indigenus, and probably also Western European T. t. troglodytes, but should not be applied to the larger, offshore island races.