LS1_LECTURE_21

this biogeographical demarcation is known as the

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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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