The Geographical and Ecological Distribution of Arboreal Psocoptera

Annu. Rev. Entomol. 1985.30:175-196. Downloaded from arjournals.annualreviews.org
by Mr. Bas van Berkum on 10/10/07. For personal use only.
Annual Reviews
www.annualreviews.org/aronline
184 THORNTON
tion between differentiation and isolation is greater for the stenotopic acraeus
than for the eurytopic dentatus, and it appears that both are actively speciating
on the archipelago. In view of the known geological history (31),. dispersal
rather than fragmentation events appear to have been the likely precursors of
differentiation both between archipelago populations and between the continental
and Galapagos species. A related species, I. texanus, was an early and
regular colonizer of Florida mangrove islets defaunated by tent fumigation
(71).
Temperate South America
The temperate South American fauna is rather better known than that of the
tropics, particularly west of the Andes. Many groups that are typical of the
tropics are lacking, and the characteristic genus Ptenopsila is endemic to the
region. The temperate fauna is less diverse; only a few species are both frequent
and abundant, a situation similar to that in northern latitudes. The Elipsocidae
appear to have radiated particularly in Chile, where the genera Eolachesilla and
Roesleria are endemic and Nothopsocus is endemic to Chile and the Juan
Fernandez Islands. Although Chile may be regarded as an ecological island
with the Atacama desert to the north and mountains to the east, the Andean
barrier declines in significance in the south as the range becomes lower and
eventually runs into the sea. The Valdivian forests possess a rich and varied
fauna; the more southern Magellanic forests, dominated by Nothofagus, are
impoverished, with an attenuated fauna (63).
The arboreal psocid fauna of Argentina appears to include southward incursives,
and many species there do not occur in Chile. However, in the south, at
least two of the four most abundant Chilean species are trans-Andean. The
Embidopsocinae and Pachytroctidae, which are well represented in Brazil and
Argentina, have not been found in Chile, and Sphaeropsocidae appear to be
rare east of the Andes yet have nine species in Chile (4). In other genera several
species pairs with a member on each side of the Andes have been noted (1).
Of the Juan Fernandez group, only Robinson Crusoe (Mas a Tierra) has been
surveyed (88). The nine known species comprise an endemic complex of five
Nothopsocus species, a species widely distributed it/Chile, and three with an
extensive range and probably recently introduced. Remarkably, on the Chilean
mainland Nothopsocus is represented by only two species, which are neither
widely distributed nor common. In contrast, the genus Drymopsocus (also
Elipsocidae), which has four widely distributed species in Chile, was not found
on Robinson Crusoe. Possibly, ecological exclusion is responsible for these
contrasting patterns. The families Caeciliidae and Philotarsidae, both common
in Chile, also appear to be absent from Robinson Crusoe. The Galapagos and
Robinson Crusoe faunas are strikingly different; elipsocids are not known from
the Galapagos, and only Peripsocus nitens, abundant on the Chilean mainland,
is probably common to the two.