Life history traits of specialist and generalist species

Global changes alter ecosystems and have caused dramatic population declines and extinctions. In particular specialist species of very different groups have been affected all over the world in various ecosystems. Specialization is often reduced to a discrete trait. One interest of this paper is the analysis of specialization using a quantitative measure. Thus, understanding the characteristics of specialist species is an urgent challenge for scientists. Here, we use a phylogenetic approach to examine how niche width evolution is associated with particular life history traits. At the macro evolutionary scale we used comparative analyses to examine the relationships between specialization and some life history traits (namely age at first reproduction, fecundity and dispersal). Second, at the micro evolutionary scale, we assess whether specialisation is associated with higher or lower within species variability in life history traits, (i.e do generalist species have a higher plasticity than specialists?). We found that life history traits variation between species was not connected to specialization. Age at maturity and fecundity appeared quasi-fixed by historical contingency and thus can be regarded as constraints. Only within species variation of dispersion is linked to specialization. Thus, it seems that the specialization’s evolution, i.e the ecological gradient occupied by a species, is modelled by evolutionary forces acting on behavioural traits but not on life cycle history traits.