Constraints on control: factors influencing reproductive success in male mandrills (Mandrillus sphinx)

Over the last decade, paternity analysis using molecular markershas revealed that observed mating systems do not necessarilycorrelate with reproductive systems and thus cannot providereliable information about male reproductive success (RS). Thisis especially true for primate species with a complex multimale-multifemalesocial organization, such as mandrills (Mandrillus sphinx).Using molecular markers for the measurement of individual RSand a comprehensive data set comprising 193 offspring from 27birth cohorts over a 20-year period of sampling, we investigatedthe social, genetic, and demographic factors that may influencethe probability of paternity by dominant male mandrills, livingin a semi–free-ranging colony. We observed a significantskew in RS towards dominant males, with their probability ofpaternity increasing as the number of adult males in the groupincreased, and when they were closely related to subordinateadolescent males. Conversely, the probability of dominant malessiring infants decreased when the number of simultaneously tumescentfemales increased. Fewer offspring were sired by dominant maleswhen female partners were closely related to them and when therelatedness between dominant and subordinate adult males increased.These two last points suggests particularly that mechanismsof kin recognition are operating to avoid the costs of inbreedingand may also reflect the lower costs to dominant males of losingconception opportunities to more closely related subordinateadult males. This study is, to our knowledge, one of the firstin primates to use an integrative approach and multivariateanalysis to show that multiple factors are involved in determiningthe probability of paternity by dominant males.     

Germination ecology of Cassava (Manihot esculenta Crantz, Euphorbiaceae) in traditional agroecosystems: Seed and seedling biology of a vegetatively propagated domesticated plant

Cassava is clonally propagated, but Amerindian farmers also use plants from volunteer seedlings to prepare stem cuttings. Although sexual reproduction plays a role in cassava’s evolution it is poorly studied. We examined one aspect of cassava reproductive ecology, seed dormancy and germination. Volunteer seedlings emerge from a soil bank of seeds produced during the previous cycle of cultivation that remain ungerminated through the fallow period, then germinate synchronously after vegetation is slashed and burned. Laboratory experiments showed that germination can be enhanced by mechanical scarification and also by dry heat treatment, suggesting that burning after field clearing could help break dormancy. Germination was also stimulated by high temperatures (35°C) that in nature indicate bare soils, and inhibited by temperatures (25°C) close to those in soil shaded by vegetation and by light. Seeds of both wild and domesticated cassava exhibit physiological dormancy, an adaptation for germination in periodically disturbed habitats. In addition to these preadaptations, preliminary results also suggest specific adaptations of domesticated cassava to the distinctive disturbance regimes of swidden agriculture.     

When leaves act like flowers: how dwarf palms attract their pollinators

In pollination mutualisms, floral odours are signals advertising the presence and location of rewards. However, in the case of the dwarf palm (Chamaerops humilis) and its species‐specific pollinating weevil (Derelomus chamaeropsis), rewards and advertisements are spatially separated. Flowers provide their specific pollinators with food and sites for both egg laying and larval development, but do not advertise them with floral odours or visually conspicuous petals. Insect behavioural bioassays revealed that pollinators are attracted by scents emitted by the leaves, which provide no rewards. These scents are released by large structures located at the sinuses of the palmate leaf. Such scent‐releasing structures have not been previously reported on palm leaves, and we suggest that they may represent an ‘exaptation’ (pre‐existing trait that acquired new functions). We also propose that such functional crossovers between vegetative and reproductive domains may be more frequent in plants than is currently documented.     

Ancient and recent evolutionary history of the bruchid beetle, Acanthoscelides obtectus Say, a cosmopolitan pest of beans

Acanthoscelides obtectus Say is a bruchid species of Neotropical origin, and is specialized on beans of the Phaseolus vulgaris L. group. Since the domestication and diffusion of beans, A. obtectus has become cosmopolitan through human-mediated migrations and is now a major pest in bean granaries. Using phylogeographic methods applied to mitochondrial DNA (mtDNA) and nuclear microsatellite molecular markers, we show that the origin of this species is probably further south than Mesoamerica, as commonly thought. Our results also indicate that A. obtectus and its Mesoamerican sister species Acanthoscelides obvelatus, two morphologically close species differing principally in voltinism, speciated in allopatry: A. obtectus (multivoltine) arising in Andean America and A. obvelatus (univoltine) in Mesoamerica. In contrast to Mesoamerica where beans fruit once yearly, wild beans in Andean America fruit year-round, especially in regions showing little or no seasonality. In such habitats where resources are continuously present, multivoltinism is adaptive. According to existing hypotheses, multivoltinism in A. obtectus is a new adaptation that evolved after bean domestication. Our data suggest the alternative hypothesis that multivoltinism is an older trait, adapted to exploit the year-round fruiting of wild beans in relatively aseasonal habitats, and allowed A. obtectus to become a pest in bean granaries. This trait also permitted this species to disperse through human-mediated migrations associated with diffusion of domesticated beans. We also show that diversity of Old World A. obtectus populations can be quite well explained by a single colonization event about 500 bp. Human-mediated migrations appear not to be rare, as our results indicate a second more recent migration event from Andean America to Mexico.     

Modeling the population dynamics of annual plants with seed bank and density dependent effects

A model is proposed for the population dynamics of an annual plant (Sesbania vesicaria) with a seed bank (i.e. in which a proportion of seeds remain dormant for at least one year). A simple linear matrix model is deduced from the life cycle graph. The dominant eigenvalue of the projection matrix is estimated from demographic parameters derived from field studies. The estimated values for population growth rate () indicates that the study population should be experiencing a rapid exponential increase, but this was not the case in our population.The addition of density dependent effects on seedling survivorship and adult fecundity, effects for which field studies provide evidence, considerably improves our model. Depending on the demographic parameters, the model leads to stable equilibrium, oscillations, or chaos. Study of the behaviour of this model in the parameter space shows that the existence of a seed bank allows higher among-year variation of adult fecundity, without leaving the region of demographic stability. Field data obtained over 3 years confirm this prediction.     

Fig Wasps: A Staple Food for Ants on Ficus

Mutualisms involve the exchange of resources and these resources attract exploiters and predators. Because predators may have a stronger effect either on mutualists or on exploiters, their net effect on the mutualism may be positive or negative. Ants and Ficus -associated wasps are a potential example. These wasps could represent sufficient food to ensure a permanent presence of predators. If this is the case then we may expect divergent selection (dependent on fig species) on traits facilitating or impeding ant predatory activity. Dioecious Ficus species in Brunei present the opportunity to determine whether presence of fig wasps on a tree ensures increased presence of ants because: (1) wasps are mainly present on male trees, thus allowing study of the effect of wasp abundance on ant presence; and (2) preliminary observations showed that ants present on trees were mainly predatory species that do not tend hemipterans. We show here, for several dioecious Ficus species, that many more ants were present on male trees than on female trees. Furthermore, these ants were mainly dominant predatory taxa that often nested in the male trees. Hence, wasps on male trees provide a sufficient resource in terms of quantity and reliability to ensure the continuous presence of dominant ants on the trees.