Do female bank voles (Clethrionomys glareolus) mate multiply to improve on previous mates?

Contrary to classical sexual selection theories, females of many taxa mate with multiple males during one reproductive cycle. In this study, we conducted an experiment on the “trade-up hypothesis”, which proposes that females remate if a subsequently encountered male is potentially superior to previous mates to maximize the genetic quality of their offspring. We presented bank vole females (Clethrionomys glareolus) sequentially with two males of known dominance rank in different orders, i.e., either first subordinate and second dominant, first dominant and second subordinate, or two males that were equal in dominance (high ranking) and observed their mating behavior. We found that 92% of the females mated multiply and did not base their remating decision on male social status. Therefore, polyandry cannot be explained by the “trade-up hypothesis” based on dominance rank in this species. However, we found that dominant males sired significantly more offspring than subordinate males. This varied according to mating order: dominant males sired more offspring when they were second than when they were first. Moreover, litter sizes were significantly smaller when the dominant male was first (smallest relative success of dominant males) compared to litter sizes when mating order was reversed or both males equal in status. Our results suggest that even though multimale mating includes males that are of poorer quality and thus potentially decreases the fitness of offspring, most of a female’s offspring are sired by dominant males. Whether this is due to cryptic female choice, sperm competition, or a combination of both, remains to be tested.     

Shouting the odds: vocalization signals status in a lizard

Many species possess multiple sexually dimorphic traits, which incorporate different sensory modalities (e.g., acoustic, olfactory and visual), although their relative roles in sexual selection and in determining reproductive success are still poorly understood for most taxa. We assessed the role of multiple male traits, including one acoustic (dominant call frequency) and one visual (yellow throat patch) trait, in residency advertisement, contest behavior, and breeding success in barking geckos (Ptenopus garrulus garrulus). We show that male barking geckos maintain largely exclusive home ranges, with a trend for larger males to maintain larger home ranges. We also show that larger males have a lower dominant calling frequency. When aggressive behavior was elicited in the field using a recorded call of average frequency, resident males with low frequency calls were more likely to respond aggressively and charge the speaker compared to males with high frequency calls. However, body size and small relative throat patch size, rather than call frequency, were the best predictors of overall aggressiveness. Body size was also the best predictor of whether males bred. We suggest that call frequency in this crepuscular species constitutes an effective long-range signal of body size, used by males for remote rival assessment and to advertise home range boundaries in low-light environments.     

Low queen mating frequency in the seed-harvester ant Pogonomyrmex (Ephebomyrmex) pima: implications for the evolution of polyandry

The evolution of polyandry is a central problem in the study of insect mating systems, and both material and genetic benefits have been proposed to offset the presumed costs of multiple mating. Although most eusocial Hymenoptera queens mate with just one or occasionally two males, high levels of polyandry are exhibited by several taxa, including seed-harvester ants of the genus Pogonomyrmex. Previous studies of queen mating frequency in Pogonomyrmex have focused on monogynous (one queen per colony) species in the subgenus Pogonomyrmex. We performed a genetic mother–offspring analysis of mating frequency in Pogonomyrmex (Ephebomyrmex) pima, a queen-dimorphic species with dealate and intermorph queens that differ in colony structure (intermorph colonies contain multiple queens). Our results demonstrate that both dealate and intermorph queens of P. (E.) pima are typically single maters, unlike their congeners analyzed thus far. Polyandry appears to be a derived trait in Pogonomyrmex, but comparative tests between P. (E.) pima queen morphs and across the genus provide no evidence that it evolved as an adaptation to increase genetic diversity within colonies or to obtain more sperm, respectively.     

Female sensory bias may allow honest chemical signaling by male Iberian rock lizards

Some mate choice theories propose that only male signals that are honest and condition-dependent can be stable, while another hypothesis states that males evolve signals that exploit the sensory system of females. However, sensory traps might evolve into honest signals if they are differentially costly for males. We tested whether a pre-existing sensory bias for food chemicals explained chemosensory preferences of female Iberian rock lizards for male scents. We manipulated hunger levels of females and found that food-deprived females had increased chemosensory responses to chemical stimuli from both invertebrate prey and femoral secretions of males, but not to control water. Further tests suggested that cholesta-5,7-dien-3-ol (provitamin D₃), a lipid found in both prey and males’ scent, may be one of the chemicals eliciting these responses. Moreover, hungry females spent more time on scent marks of males that had experimentally increased cholesta-5,7-dien-3-ol than on scent marks of males alone, whereas for control females this effect was not significant. We suggest that preexisting sensory bias for essential nutrients (i.e., provitamin D) may be the origin of similar female responses to male chemicals. However, previous studies have suggested that the allocation of these chemicals to ornaments is costly and only high quality males can afford it. Therefore, preexisting sensory bias for essential nutrients may further allow the evolution and maintenance of honest sexual displays.     

Modelling multiple dispersion of radionuclides through the environment

The migration of a contaminant through the environment is the result of the transport by a variety of biotic and abiotic carriers which move according to different dispersion mechanisms. Consequently, the patterns of the distribution of a pollutant in the environment cannot be ever explained on the basis of a single migration process or assuming that the concentrations of contaminant in the different kinds of carriers quickly reach the equilibrium condition. The present work discusses two examples (wash-off from catchments and transport through soils of radionuclides) that clearly demonstrate the inadequacy of “single dispersion” models to predict these patterns. On the contrary, models based on multiple dispersion can successfully simulate the particular features of the above mentioned processes. It was demonstrated that the time behaviour of radionuclide migration rates from catchment of different rivers vary within small ranges as a consequence of multiple dispersion. This result can be useful for the development of generic predictive models.     

Multiple insemination increases reproductive success of female Montandon’s newt (<Emphasis Type="Italic">Triturus montandoni</Emphasis>, Caudata,Salamandridae)

The adaptive significance of multiple matings for females is a matter of much controversy. In insects, supplying the female’s sperm reserves with portions of fresh spermatozoa may be the main function of multiple matings. This simple explanation may also be applied to other animals which produce large numbers of eggs over prolonged periods of time. We tested the fertility insurance hypothesis in Montandon’s newt (Triturus montandoni, Amphibia, Salamandridae). T. montandoni females are inseminated internally by spermatophores they have picked up, and subsequently lay eggs fertilized by spermatozoa released from the spermatheca. We compared the reproductive success of singly and multiply inseminated females of Montandon’s newt in the laboratory. Multiply inseminated females laid more eggs and had a lower percentage of non-developing eggs than females who mated only once. Our data suggest that remating increases the reproductive success of multiply inseminated females by replenishing sperm reserves in the spermatheca or by supplying females with fresh portions of spermatozoa with high fertilizing capacity. Received: 7 January 2000 / Revised: 13 September 2000 / Accepted: 7 October 2000     

Extremely high mating frequency in the Florida harvester ant (<Emphasis Type="Italic">Pogonomyrmex badius</Emphasis>)

High effective multiple queen mating is a rare but taxonomically widespread phenomenon in eusocial Hymenoptera that has arisen convergently in several taxa. In ants, high effective mating frequencies have been confirmed in only two clades: the higher leaf-cutters (Atta, Acromyrmex) and the Pogonomyrmex seed harvesters. We analysed polyandry in Pogonomyrmex badius, which has a life-history unique within the genus, and report the highest numerical mating frequencies thus far recorded in ants. We also show that P. badius is characterized by one of the highest effective mating frequencies hitherto found in ants. It is now clear that all major sub-clades of Pogonomyrmex sensu stricto exhibit high levels of polyandry. Therefore, multiple mating must have arisen early in the evolution of the genus, and may have constituted a mechanism to increase offspring variability for queens that were confronted with increasingly complex levels of organization. Too few congeners have been investigated by the same method to be certain that polyandry in P. badius is really higher than in the rest of the genus. If so, research should concentrate on a possible link between high queen mating frequency and the distinct caste system found in P. badius.Communicated by L. Keller     

Determining Visitors’ Dispositions Toward the Designation of a Greek National Park

This article presents the findings of the first major visitor survey conducted at the Central Rhodope Mountain Complex, situated in northern Greece. The study area is one of a number of sites planned to become National Parks under a recent initiative of the Greek government. We used a logistic regression method to define significant predictors of visitors’ awareness and attitude toward park designation, as well as their willingness to pay a conditional entrance fee. Study findings demonstrated that the probability of being aware of the park designation initiative is higher for visitors who obtained information from travel agencies or media to make their destination choice, compared to visitors who resorted to word-of-mouth recommendations. Knowledge and attitudes toward animals living in the study area revealed a limited influence on visitors’ dispositions toward park designation. The results of this study call for action to implement education programs for National Park users. These programs should aim at rendering the environmental characteristics of the Central Rhodope Mountain Complex to be significant predictors of visitors’ dispositions toward the study area. This would favor its uniqueness as a destination, as well as contribute to its long-term economic sustainability.     

Biamnial elevated alpha-fetoprotein and positive acetylcholinesterase in twins,one with anencephaly

Anencephaly in twin B was accompanied by elevated amniotic fluid alpha-fetoprotein (AFP) and a positive acetylcholinesterase (AChE) band on gel electrophoresis in both twin sacs, although twin A was normal. AChE results did not help distinguish the false positive AFP in this set of twins, implying that AChE may diffuse transamniotically as has been previously postulated for AFP. In light of the low concordance rate for neural tube defects in twins, patient counselling in this situation must include the information that AFP and AChE may be falsely elevated in normal twin when the other twin has a neural tube defect.     

Prenatal detection of multiple copies of a familial supernumerary marker chromosome

Direct preparations and long-term cultures from a chorion villus biopsy, taken because of a known maternal additional marker chromosome, showed a 48,XX,+mar,+mar karyotype in all cells examined. The same karyotype was revealed in a subsequent amniotic fluid sample and in cord blood at delivery. Detailed examination of the child at delivery and at 1 year of age showed no evidence of phenotypic abnormality or developmental problems.