Table 1.

Summary of factors affecting diversification rates and diversity limits. Up arrows, increases/ing; down arrows, decreases/ing.

type of factor	factor	effects on speciation rate	effects on extinction rate	effects on diversity limits
	area	↑ potential for geographical isolation of separated populations	↓ by ↑ survival of refuge populations
environmental factors strongly correlated with area	population size	↑ rate of appearance of beneficial mutations, standing genetic variation, persistence of incipient species	↓ by buffering populations from demographic stochasticity, environmental disasters, habitat loss	↑ number of species with viable populations supported
	habitat diversity	↑ population divergence through local adaptation		↑ niche space available
	fragmentation /topographic diversity	↑ isolation of populations; however past a certain point, will ↓ speciation by ↓ population size	if fragmentation results in too small patches of area or habitat, will ↑ extinction rate	↑ by allowing more ecologically equivalent species to be supported
environmental factors not strongly correlated with area	energy availability	↑ rate of molecular evolution, rate of coevolutionary dynamics, size of populations supported		↑ by facilitating specialization to narrow niches
clade traits	life-history traits	faster life cycle ↑ speciation by increasing mutation rate	faster life cycle ↓ extinction by ↑ resilience to disturbance
	range size	larger range sizes ↑ speciation by ↑ potential for isolation of populations	larger range sizes ↓ extinction by ↑ survival of refuge populations	smaller range sizes ↑ diversity limit by allowing more species to pack into same area
	niche breadth	narrower niche breadths associated with ↑ speciation	narrower niche breadths associated with ↑ extinction	narrower niche breadths ↑ diversity limit by allowing finer subdivision of niche space
	dispersal	↓ by reducing potential isolation of populations, but can also ↑ speciation rate by ↑ rate at which species colonize new regions	↓ by ↑ resilience to disturbance	↓ if high dispersal ability is associated with large, non-overlapping species ranges