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Rahier, Martine
Nom
Rahier, Martine
Affiliation principale
Fonction
Professeure ordinaire
Email
Martine.Rahier@unine.ch
Identifiants
Résultat de la recherche
Voici les éléments 1 - 8 sur 8
- PublicationAccès libreThe phylogeography of an alpine leaf beetle: Divergence within i Oreina elongata spans several ice ages(2010)
; Naisbit, Russell E - PublicationAccès libreGlacial survival and local adaptation in an alpine leaf beetle(2007)
; Naisbit, Russell. E.The challenge in defining conservation units so that they represent evolutionary entities has been to combine both genetic properties and ecological significance. Here we make use of the complexity of the European Alps, with their genetic landscape shaped by geographical barriers and postglacial colonization, to examine the correlation between ecological and genetic divergence. Montane species, because of the fragmentation of their present habitat, constitute extreme cases in which to test if genetically distinct subgroups based on neutral markers are also ecologically differentiated and show local adaptation. In the leaf beetle Oreina elongata, populations show variation in host plant use and a patchy distribution throughout the Alps and Apennines. We demonstrate that despite very strong genetic isolation (FST = 0.381), variation in host plant use has led to differences in larval life-history traits between populations only as a secondary effect of host defence chemistry, and not through physiological adaptation to plant nutritional value. We also establish that populations that are more ecologically different in terms of larval performance are also more genetically divergent. In addition, morphological variation used to define subspecies appears to be mirrored in the population genetics of this species, resulting in almost perfect clustering based on microsatellite data. Finally, we argue from their strong genetic structure and congruent distribution that the subspecies of O. elongata were divided among the same glacial refugia within the Alps that have been proposed for alpine plants. - PublicationAccès libreGeographic variation in oviposition choice of a leaf beetle: the relationship between host plant ranking, specificity, and motivation(2007)
- PublicationAccès libreConserved oviposition preferences in alpine leaf beetle populations despite host shifts and isolation(2007)
; Naisbit, Russell. E.1. Choosing the plant on which to lay their eggs is the last act of care that most female herbivorous insects bestow upon their offspring. These decisions play a pivotal role in insect–plant interactions, placing host preference under strong selection and contributing to the diversity of phytophagous insects as one of the first traits to adapt to new hosts.
2. This study presents a test of whether extreme isolation and exposure to different host plants can produce intra-specific divergence in oviposition preference in alpine insects. Geographic variation should impose selection to fine-tune host plant ranking and specificity to the plants normally encountered, to avoid wasting time during the very limited reproductive season experienced at high altitudes.
3. Beetles from five populations of Oreina elongata differing in host availability were offered three natural hosts: Cirsium spinosissimum, Adenostyles alliariae, and Adenostyles glabra. A novel application of a continuation ratio model (logistic regression) was made to sequential no-choice experiments, combined with quasi-likelihood analysis of multiple-choice experiments.
4. The results show little geographic variation in host plant choice: all populations strongly preferred Cirsium in multiple-choice trials, and in no-choice experiments laid around 47% of their remaining eggs during each stage, almost regardless of the host present.
5. Enemy-free space seems to explain the preference for Cirsium, but isolation and exposure to different plants has clearly not caused local adaptation in host plant ranking or specificity. Reasons for this conservatism despite divergence in other characteristics are discussed. - PublicationAccès libreIsolation and characterization of microsatellite loci in the Alpine leaf beetle, Oreina elongata(2005)
- PublicationAccès libreThe evolution of larval foraging behaviour in response to host plant variation in a leaf beetle(2005)
; The evolutionary causes of variation in host specialization among phytophagous insects are still not well understood and identifying them is a central task in insect–host plant biology. Here we examine host utilization of the chrysomelid beetle Oreina elongata that shows interpopulation variation in the degree of specialization. We focus on larval behaviour and on what selection pressures may favour the use of two different larval host plants (Adenostyles alliariae and Cirsium spinosissimum) in one population as opposed to specialization onto one of them as is seen in other populations. The results suggest that the degree of exploratory foraging behaviour is higher in larvae from the two-host population than in single host populations, and a field survey of the two-host population also indicated that larvae do move between host species. A field experiment indicated that predation rates on O. elongata larvae in the two-host population are higher on one of the host species, A. alliariae, than on the alternative C. spinosissimum. In combination with earlier results this finding suggest that larvae move between hosts to obtain better food on one host, and to get better protection from predators on the other. It appears that in this two-host situation a single plant species does not provide the most beneficial conditions in all parts of O. elongata life cycle and individuals may obtain different plant-specific benefits by moving between host species. This heterogeneous host situation appears to have selected for the explorative larval foraging strategy seen in the in the two-host population. In general, the results support the notion that to understand patterns of host plant use in insects it is often vital to consider a range of host related selection pressures whose relative importance may vary between life stages of the insect. - PublicationAccès libreLocal adaptations in an alpine leaf beetle(2003)
- PublicationAccès libreThe growth strategy of an alpine beetle: maximization or individual growth adjustment in relation to seasonal time horizons ?(2003)
2. The presence of such ability was tested for in the alpine beetle Oreina elongata Suffrian. In this species, the favourable period for development is relatively short and of unpredictable length, and individuals are chemically defended against predation; factors that could affect the balance between the benefits and costs of high growth rate.
3. Here it is shown that when time stressed, O. elongata larvae were able to increase growth rate, accelerate development and reach the normal final weight.
4. Hence, individual growth rate adjustment was present in a situation where its adaptive value appeared to be relatively weak, which supports the notion that flexible growth strategies are a common phenomenon in temperate insects.