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Larval Traits (larval + trait)
Selected AbstractsHow do paedomorphic newts cope with lake drying?ECOGRAPHY, Issue 4 2003Mathieu Denoël Paedomorphosis, in which adult individuals retain larval traits, is widespread in newts and salamanders. Most evolutionary models predict the maintenance of this life-history trait in favourable aquatic habitats surrounded by hostile terrestrial environments. Nevertheless, numerous ponds inhabited by paedomorphic individuals are unpredictable and temporary. In an experimental framework, I showed that paedomorphic newts were able to metamorphose and thus survive in the absence of water. However, the mere decrease of water level or the life space do not seem to induce metamorphosis in paedomorphs. On the contrary, drying up induces almost all individuals to move on land and after that to colonize other aquatic sites located nearby. Such terrestrial migrations allow survival in drying conditions without metamorphosis as long as the distances of terrestrial migration are short. These results are consistent with the presence of paedomorphs in drying ponds and are in favor of classic optimality models predicting metamorphosis in unfavorable environments. [source] Adaptive radiation through phenological shift: the importance of the temporal niche in species diversificationECOLOGICAL ENTOMOLOGY, Issue 1 2009JEAN-MARIE SACHET Abstract 1.,Phenological shift in oviposition in seed predators may be a key factor for adaptive radiation if temporal differences lead to less intense competition. 2.,This hypothesis was tested at two sites in the French Alps in three sympatric species of larch cone flies grouped into two phenological groups (early and late) differing in adult emergence and oviposition timing by approximately 2 weeks. The present study assessed the intensity of competition within and between groups by measuring four larval traits. Cone traits were measured, and the impact of early species parasitism on cone development was assessed. 3.,The occupation of the central axis of a developing cone by one early larva has a strong detrimental effect on cone growth and seed production. However, there was almost no correlation between the variables measured on the cones and on the larvae, suggesting that the resources available were not limiting. 4.,Inter-group competition had no significant effect on early larvae. In contrast, both inter- and intra-group competition had a significant negative effect on late larvae length (,11% and ,16% respectively), dry mass (,8% and ,23%), and lipid mass (,15% and ,26%). The intensity of competition was stronger among larvae in the same phenological group, which is consistent with the hypothesis that shifts in oviposition promote adaptive radiation in larch cone flies by reducing competition among larvae. [source] The role of competition in adaptive radiation: a field study on sequentially ovipositing host-specific seed predatorsJOURNAL OF ANIMAL ECOLOGY, Issue 1 2004Laurence Després Summary 1We propose an alternative model to the host-shifting model of sympatric speciation in plant,insect systems. The role of competition in driving ecological adaptive radiation was evaluated in a seed predator exploiting a single host-plant species. Sympatric speciation may occur through disruptive selection on oviposition timing if this shift decreases competition among larvae feeding on seeds. 2The globeflower fly Chiastocheta presents a unique case of adaptive radiation, with at least six sister species co-developing in fruits of Trollius europaeus. These species all feed on seeds, and differ in their oviposition timing, one species ovipositing in 1-day-old flowers (early species), while all the other species sequentially oviposit throughout the flower life span (late species). We evaluated the impact of conspecific and heterospecific larvae on larval installation success, and on larval fresh mass and area, for early and late species, in natural conditions. 3None of the three larval traits measured was correlated with fruit size, and no fruit lost all seeds to predation, suggesting that seed availability was not a limiting factor for larval development. 4Our results show strong intraspecific competition among early larvae for larval installation, and among late larvae for larval mass. By contrast, larval competition between species was weak. These results are consistent with the hypothesis that shifts in oviposition promoted rapid radiation in globeflower flies by lowering competition among larvae. [source] Do larvae evolve the same way as adults in Tingidae (Insecta: Heteroptera)?CLADISTICS, Issue 2 2004Eric Guilbert A recent cladistic analysis showed that adult traits of Tingidae, which exhibit a great variety of shapes, evolved homoplastically from simple to complex (Guilbert, 2001). These complex traits, often exaggerated, were hypothesized to be adaptive. However, this study, as well as another by Lis (1999), both based on adult morphology, contradict the traditional classification of Tingidae. A new analysis is performed here, that includes larval characters, which, like those of adults, have a great variety of shapes. The results corroborate the traditional classification of the Tingidae. No clear divisions among Tinginae are drawn from the analysis, but an evolutionary pattern of shapes among Tingidae emerges from this study. There is a global tendency for larval traits to evolve convergently from simple to complex, as suggested for adults. The pattern seen in adult and larval traits is independent, but consistent. These traits can be used in the same anti-predation context, but with different roles. [source] | ||||||||||