Why is it that some species are found in some areas but not others? Answering this question is the task of biogeography and the answers fall into two main categories: that species dispersed to that area from elsewhere at some point in the past, or it has been there since it originated.
With the integration of data from fossils, phylogenies based upon both morphological and molecular data and palaeoenvironmental information, it is possible to offer explanations of why some species are found in particular areas and how they got there. The fossils permit the phylogenies to be time-calibrated and dated evolutionary events can be assessed in light of simultaneous environmental change.
I will illustrate these basic principles of biogeography initially with an example of long distance geodispersal: an obscure and rare group of bees found primarily in the Mediterranean region have all of their close relatives in the New World. I will suggest how they got to their currently occupied range.
Bees are more diverse in arid and semi-arid regions of the world and also more diverse in the southern hemisphere. I will explore the radiation of bees in the world’s driest desert – the Atacama Desert of Chile. Here, some bees must remain in diapause for many years before conditions are suitable for production of the next generation. I will give examples of unusual habitats that provide resources for bees in this otherwise inhospitable environment.
In most of the Atacama Desert the limited rainfall occurs in winter, but in the extreme northeast of the country, most rain falls in summer. I will investigate the potential influence of this disjunction on bee evolution.
Lastly, I will discuss the often remarkable adaptations bees have for foraging on desert plants and use dated phylogenies to investigate bee transition to the most speciose genus of flowering plants in the Atacama.