Reproductive flexibility: genetic variation, genetic costs and long-term evolution in a collembola

• Published in: PloS one Vol. 3; no. 9; p. e3207
• Main Authors: Tully, Thomas, Ferrière, Régis
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 15.09.2008; Public Library of Science (PLoS)
• Subjects: Adaptation; Adaptations; Adjustment; Analysis; Animal behavior; Animals; Aquatic insects; Arthropods - genetics; Arthropods - physiology; Biological Evolution; Biology; Cloning; Cluster Analysis; Clutch size; Clutches; Collembola; Comparative analysis; Correlation; Crowding; Cues; Data analysis; Divergence; Ecology/Evolutionary Ecology; Eggs; Environment; Environmental conditions; Evolution; Evolution (Biology); Evolution, Molecular; Evolutionary Biology; Evolutionary Biology/Animal Behavior; Evolutionary Biology/Animal Genetics; Evolutionary Biology/Evolutionary Ecology; Evolutionary genetics; Female; Fitness; Flexibility; Folsomia candida; Food; Food quality; Gene polymorphism; Genetic aspects; Genetic diversity; Genetic polymorphisms; Genetic Variation; Insecta; Investment; Isotomidae; Life history; Life span; Models, Biological; Models, Genetic; Museums; Norms; Phenotype; Phenotypic variations; Phylogeny; Physiology; Polymorphism; Polymorphism, Genetic; Proportional Hazards Models; Reproducibility of Results; Reproduction - physiology; Reproductive fitness; Survival; France
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0003207

In a variable yet predictable world, organisms may use environmental cues to make adaptive adjustments to their phenotype. Such phenotypic flexibility is expected commonly to evolve in life history traits, which are closely tied to Darwinian fitness. Yet adaptive life history flexibility remains poorly documented. Here we introduce the collembolan Folsomia candida, a soil-dweller, parthenogenetic (all-female) microarthropod, as a model organism to study the phenotypic expression, genetic variation, fitness consequences and long-term evolution of life history flexibility. We demonstrate that collembola have a remarkable adaptive ability for adjusting their reproductive phenotype: when transferred from harsh to good conditions (in terms of food ration and crowding), a mother can fine-tune the number and the size of her eggs from one clutch to the next. The comparative analysis of eleven clonal populations of worldwide origins reveals (i) genetic variation in mean egg size under both good and bad conditions; (ii) no genetic variation in egg size flexibility, consistent with convergent evolution to a common physiological limit; (iii) genetic variation of both mean reproductive investment and reproductive investment flexibility, associated with a reversal of the genetic correlation between egg size and clutch size between environmental conditions ; (iv) a negative genetic correlation between reproductive investment flexibility and adult lifespan. Phylogenetic reconstruction shows that two life history strategies, called HIFLEX and LOFLEX, evolved early in evolutionary history. HIFLEX includes six of our 11 clones, and is characterized by large mean egg size and reproductive investment, high reproductive investment flexibility, and low adult survival. LOFLEX (the other five clones) has small mean egg size and low reproductive investment, low reproductive investment flexibility, and high adult survival. The divergence of HIFLEX and LOFLEX could represent different adaptations to environments differing in mean quality and variability, or indicate that a genetic polymorphism of reproductive investment reaction norms has evolved under a physiological tradeoff between reproductive investment flexibility and adult lifespan.