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Unformatted text preview: ive to the more northern and
western islands were radically different
from the species found on the more
southern and eastern islands, despite
being part of the same biome. ! This biogeographical demarcation is
known as the Wallace line; it separates
species with Asian and Australian
affinities. A deep ocean trench
maintained a water barrier to dispersal,
resulting in landforms on either side of
the line remaining isolated. Humans as Dispersal Agents
! In many cases, human activity circumvents physical barriers.
! Humans have also transported thousands of plants, birds, insects,
and other species across physical barriers to new locations (both
accidentally and intentionally). ! Consider the case of mongoose in Hawaii, originally introduced to
control rats in sugarcane fields. Exotic and Invasive Species
! If an exotic species is introduced into a new area, spreads rapidly,
and eliminates native species, it is considered an invasive species. ! In Southern California, Arundo and Tamarix, have had devastating
effects in our streams, impacting native plants and animals. Biotic and Abiotic Factors Interact
! It is often difficult for ecologists to separate the effects of biotic
and abiotic factors on s...
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- Winter '11