Biomedical subjects

Martine Hossaert-McKey

Publications and source records attributed to Martine Hossaert-McKey.

6 recordsLinked to original sources

PubMed2005

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.

Animals↗

PubMed2004

Temporal and sexual variation of leaf-produced pollinator-attracting odours in the dwarf palm.

Information on intra-specific variation in pollinator-attracting floral traits provides clues to selective pressures imposed by pollinators. However, these traits also reflect constraints related to floral phenology or morphology. The specific weevil pollinator Derelomus chamaeropsis of the dioecious Mediterranean dwarf palm Chamaerops humilis is attracted by volatile compounds that leaves, and not flowers, release during anthesis. Production of these olfactory cues is thus probably not constrained by any other floral function. This provides the opportunity to study variation of a "floral" trait that is not produced by a floral organ. We studied volatile compounds emitted by leaves of 12 individual C. humilis over the whole flowering season. The quantity of volatile compounds emitted by leaves reached a maximum when plants required pollinator visits. The relationship between odour emission and floral phenology was slightly different between male and female plants, probably reflecting differences in the exact time at which females and males benefit from pollinator visitation. Male plants produced higher quantities of volatile compounds than females. Odour composition was highly variable among individuals but did not differ between male and female plants. In this system, female C. humilis are pollinated by deceit and pollinators should be selected to avoid visiting them. The absence of sexual difference in blend composition may thus prevent pollinators from discriminating between male and female plants.

Analysis of Variance↗

PubMed2003

Olfactive detection of fig wasps as prey by the ant Crematogaster scutellaris (Formicidae; Myrmicinae).

In the species-specific and obligate mutualism between the fig (Ficus carica) and its pollinator (the fig wasps Blastophaga psenes), a third participant, the ant Crematogaster scutellaris, is a predator of the wasps. Here, we ask how ant workers can rapidly localise such prey, whose availability is limited in time and space. Using a Y-tube olfactometer, we tested ant response to odours emitted by different types of figs (receptive female, ripe female or male figs) and by fig wasps (pollinators or non-pollinators). We demonstrate that ants were significantly attracted only to odours emitted by pollinators, either alone or associated with odours of male figs (releasing wasps). Detection of prey odour by ants is an important trait that can explain their observed high rate of predation on pollinators, and could have important implications on the stability of the fig/fig wasp mutualism.

Animals↗

PubMed2002

Why do fig wasps actively pollinate monoecious figs?

Active pollination, although rare, has been documented in a few pollination mutualisms. Such behaviour can only evolve if it benefits the pollinator in some way. The wasps that pollinate Ficus inflorescences can be active or passive pollinators. They lay their eggs in fig flowers, so that a proportion of flowers will host a wasp larva instead of a seed. We show in an actively pollinated monoecious fig that lack of pollination does not induce fig abortion or affect wasp offspring size but results in smaller numbers of offspring. Hence, conversely to other active pollination systems, seed formation is not obligatory to sustain developing pollinator larvae; however there is a direct fitness cost to active pollinators not to pollinate. We then compared the locations of eggs and fertilised flowers of three actively pollinated Ficus species and one passively pollinated species. We found that more flowers containing wasp eggs were fertilised in the actively pollinated species relative to those of the passively pollinated one. These results along with comparison with similar studies on dioecious figs, support the hypothesis that active pollination has evolved in fig wasps to ensure that more flowers containing wasp eggs are fertilised as this may increase the chances of successful gall development. The stigmatic platform characterising actively pollinated figs is probably an adaptation to increase pollen dispersion within the fig.

Animals↗

PubMed2002

Fig volatile compounds--a first comparative study.

We analysed the compounds of volatile blends released by receptive figs of twenty Ficus species to attract their specific pollinating wasps. In all, 99 different compounds were identified. The compounds are mainly terpenoids, aliphatic compounds and products from the shikimic acid pathway. In each species blend, there are few major compounds, which are generally common among floral fragrances. Most species blends also include rare compounds, but generally their proportion in the blend is low. A possible basis for species-specificity of Ficus-wasp interactions is discussed in relation to the patterns of volatiles found in this interspecies comparison.

Animals↗

PubMed2002

Specific attraction of fig-pollinating wasps: role of volatile compounds released by tropical figs.

Floral scents often act as pollinator attractants. In the case of obligate and specific plant-pollinator relationships, the role of floral signals may be crucial in allowing the encounter of the partners. About 750 Ficus species (Moraceae) are involved in such interactions, each with a distinct species of pollinating wasp (Chalcidoidea, Agaonidae). Several species have been shown to release volatile compounds, but their role in pollinator attraction has rarely been simultaneously tested. We investigated the floral scents of four tropical fig species and combined chemical analysis with biological tests of stimulation of insects. Pollinators of three species were stimulated by the odor of their associated fig species and generally not by the odor of another species. The fourth actually comprised two distinct varieties. The main compound was often a different one in each species. Floral blends of different species always shared compounds, but ratios of these compounds varied among species.

Animals↗