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deals with the distribution of taxa around the planet in space
and time, and the factors influencing this distribution. It includes
understanding how modes of dispersal have affected which taxa
are cosmopolitan (found worldwide), which are endemic (only found
in limited regions), and which have disjunct (widely separated)
distributions that may be explained by larger processes such as
plate tectonics (changing position of landmasses over geologic
time due to shifting of the earths plates), landscape and
climatic features that provide opportunities and corridors of
dispersal, and catastropic changes to an environment, such as
volcanic eruptions. Combining the evidence from biogeography and
that of genetic relationships among taxa through phylogenetic
studies of their "family tree," scientists are able
to make hypotheses about the when, how, and why taxonomic groups
are distributed as we find them today or in the fossil record.
the present time, therevids have been found in all of the biogeographic
regions (Afrotropical, Australasian, Nearctic, Neotropical, Palearctic,
Oceanian, and Oriental) except the Antarctic. The family is thought
to have arisen in the Jurassic when the continents had coalesced
into the supercontinent of Pangea, about 200 million years ago.
Fossil evidence indicates that both the Therevidae and its sister
family, Scenopenidae had already differentiated by the Upper Jurassic.
This is consistent with the likely Triassic origin of the Brachycera
and rise of other asiloids in the Jurassic (Gaimari and Irwin
a biogeographic region:
Australasian & Oceanian
were the continents when?
more about biogeography:
York University biogeography website
University of British Columbia: Explore the World's Biomes
UCMP: Plate Tectonics and Continental Drift
Link for Pangea: Paleomap