The endemic thrips fauna of California
The fauna discussed here includes some remarkable features, both biogeographical and ecological. Two of the smallest Thysanoptera families worldwide, the Adiheterothripidae and the Fauriellidae, are both represented in California. The first of these is known otherwise only from a single genus of four species found between the Mediterranean and India, and the second is known only from two species in the Mediterranean area and two in southeastern Africa. Similarly, the genus Orothrips in the Aeolothripidae is otherwise known only from the Mediterranean.
In contrast to these distant relationships, the Californian thrips fauna is noticeably different from, and less diverse than, the thrips fauna of eastern USA. In particular, the large suite of leaf-litter species related to the genus Eurythrips that is so abundant in the eastern States (Mound, 1976, 1977) is unrepresented in California. Moreover, the thrips fauna of Florida (Diffie et al., 2008), possibly as a result of its more humid climate, includes a much larger proportion of Neotropical species that are presumably windborne from the Caribbean. There also appears to be a considerable faunal discontinuity southwards from California, with increasing numbers of large fungus-feeding thrips being found in Mexico. Moreover, the very large and worldwide genus Thrips shows a startling discontinuity with the Neotropics, such that only one native species of this genus is known from south of the border between the USA and Mexico.
The genus Ankothrips (Melanthripidae), also Dactuliothrips (Aeolothripidae), include an interestingly large number of spectacular species, but as yet there is no ecological explanation for their diversity, nor many observations on their behavior and biology. More problematic is the presence of over 20 species of the genus Aeolothrips (Aeolothripidae). The members of this genus are commonly regarded as facultative predators, and thus might be expected to be not host specific. Judging from the available descriptions, particularly of males, the diversity of Aeolothrips species in California is probably real, and thus constitutes an interesting biological phenomenon. In contrast, the presence of eleven species in California of the genus Leptothrips (Phlaeothripidae) requires further substantiation, both biological and morphological. Species in this genus are considered to be predatory on mites or other small insects, and at least one species is found on a wide range of native and introduced plants. The apparent diversity within Leptothrips is possibly not real, but seems likely to reflect inadequate morphological taxonomy. Two other genera are also species rich in California, Thrips (Thripidae) and Liothrips (Phlaeothripidae). Both of these are known to have species with a high level of host-specificity, and thus both genera may yet prove to be even more diverse than is currently recognized.