Recent studies have suggested that up to 50% of species may go extinct in the next 50 years. This is in part due to coextinction; for example the loss of tropical butterfly species from Singapore is attributed to the loss of their specific larval host plants. To see how possible future cases of coextinction would play out, researchers have made models to show probabilistic relationships between affiliate and host extinctions across co-evolved inter-specific systems. The subjects are pollinating Ficus Wasps and Ficus, primate parasites, (Pneumocystis Fungi, Nematode, and Lice) and their hosts, parasitic mites and lice and their avian hosts, butterflies and their larval host plants, and ant butterflies and their host ants. For all but the most host-specific affiliate groups (e.g., primate Pneumocystis fungi and primates), affiliate extinction levels may be modest at low levels of host extinction but can be expected to rise quickly as host extinctions increase to levels predicted in the near future. This curvilinear relationship between host and affiliate extinction levels may also explain, in part, why so few coextinction events have been documented to date.