Question

What are two possible explanations for why a species has a limited distribution (for example saguaro cactus appears in Arizona but not Baja California)?

Answer 1

The two main factors which influence species distribution are abiotic and biotic factors.

Abiotic factors mainly include soil factors which is commonly called as edaphic factors, climatic factors such as temperature, humidity, sunlight etc and social factors.

Biotic factors include predation from predators, competition for food and other resources even for mates and prevalence of disease in particular area.

In the case of saguaro cactus the factor limiting it's distribution to particular area is the abiotic factor (climatic conditions). The plant cannot grow in elevated cold conditions and it prefers to grow in Sonoran desert in Arizona.