These generalist strains could then make use of different genetic features including reversible frame-shifting of contingency genes, intra-genomic and inter-genomic recombination to fine-tune their genetic and phenotypic capacities, which may benefit their survival in individual hosts or changing environments without preventing their generalist adaptation potential.
The overlap in carbohydrate availability and use by L. casei associated with plants or the gastrointestinal tract also supports the hypothesis that many strains from these environments should be viewed as ecological generalists, whereas adaptation to cheese has been accompanied by extensive genome decay that, ultimately, resulted in niche specialization [ 28].
It is relevant to important questions in evolutionary biology, including sympatric speciation, generalist versus specialist adaptation, and parasite-host co-evolution.
Studies on the effect of tannins on the gut pH and redox potential of larvae found that many specialist and generalist insects have developed adaptations to cope with them [ 48, 49].
To determine whether adaptation to low host density – but not high host density – is accomplished by the evolution of generalist traits, we adapted replicate phage populations to experimental low density and high density microcosms containing an equal mixture of E. coli and S. typhimurium.
They also indicate the role hormesis may play in the adaptation of generalist herbivores to a variety of hostplants presenting different sets of chemical challenges.
We would expect the same reasoning to apply to any generalist herbivore that has developed adaptations to several different plant toxins, only one of which may be encountered in an individual's lifetime.
A further point of interest will be to examine the degree to which invasive asclepiads have generalist pollination systems as a pre-adaptation to exploiting novel pollinators when invading new areas.
For populations of R. leptorrhynchoides, periodic disturbance by fire may result in temporal variability in selection regimes that would lead to less local adaptation and selection for generalist genotypes with broad ecological tolerance.
We may speculate that the generalist strategy of B. burgdorferi echoes adaptation to impoverished ecologic conditions in the past because of large-scale habitat destruction in the northeastern United States in the course of the post-Columbian settlement and during the industrial revolution (8).
