  Speciation is driven by many different factors. Among those are trade-offs
between different ways an organism utilizes resources, and these trade-offs can
constrain the manner in which selection can optimize traits. Limited migration
among allopatric populations and species interactions can also drive
speciation, but here we ask if trade-offs alone are sufficient to drive
speciation in the absence of other factors. We present a model to study the
effects of trade-offs on specialization and adaptive radiation in asexual
organisms based solely on competition for limiting resources, where trade-offs
are stronger the greater an organism's ability to utilize resources. In this
model resources are perfectly substitutable, and fitness is derived from the
consumption of these resources. The model contains no spatial parameters, and
is therefore strictly sympatric. We quantify the degree of specialization by
the number of ecotypes formed and the niche breadth of the population, and
observe that these are sensitive to resource influx and trade-offs. Resource
influx has a strong effect on the degree of specialization, with a clear
transition between minimal diversification at high influx and multiple species
evolving at low resource influx. At low resource influx the degree of
specialization further depends on the strength of the trade-offs, with more
ecotypes evolving the stronger trade-offs are. The specialized organisms
persist through negative frequency-dependent selection. In addition, by
analyzing one of the evolutionary radiations in greater detail we demonstrate
that a single mutation alone is not enough to establish a new ecotype, even
though phylogenetic reconstruction identifies that mutation as the branching
point. Instead, it takes a series of additional mutations to ensure the stable
coexistence of the new ecotype in the background of the existing ones,
reminiscent of a recent observa
