For example, D. pachea is endemic to the Sonoran Desert of North America, where it depends on the sterols in the cactus Lophocereus schottii, which has alkaloids that other Drosophila species cannot tolerate. Because of its obligate association with its cactus host, it is exposed to temperatures that often approach 50°C. Such species provide unprecedented opportunities to understand the genetic bases of adaptations to extreme situations (see Box 1) and to recruit these species to address problems of species loss in the face of global warming and other anthropogenic changes.

D. melanogaster, described by Meigen in 1830, appears to have originated in sub-Saharan Africa (Lachaise et al., 1988). The first out-of-Africa habitat expansion of D. melanogaster is thought to have occurred between 10,000 and 15,000 years ago, when it moved to Europe and Asia

The oldest extant group of venomous animals is the marine phylum Cnidaria, which includes sea anemones, corals, jellyfish and hydroids.

The starlet sea anemone, Nematostella vectensis, is becoming a leading cnidarian lab model as unlike many other cnidarian species it can be grown in the lab throughout its life cycle. This makes Nematostella a unique system to study the venom of an animal with a complex life cycle. Another advantage is that the high genetic homogeneity of the common Nematostella lab strain minimizes individual genetic variation, which is far from trivial in most other venomous animals collected from the wild in limited numbers.