Getting from Point A to Point B: Species dispersal and vectors

These five symbols represent the primary vectors for invasive species dispersal. Although humans are generally the initial vector that introduces the species to a new ecosystem, water, wind, terrestrial animals, and birds can be important vectors once the new species is established. These symbols will be used to describe the vectors for species dispersal in our species profiles.

What is the probability of an introduced species spreading to new areas once introduced? How does it spread? Can the species be effectively managed without understanding its method of dispersal. Can a species be managed effectively by simply focusing on its method of dispersal? These are important questions when managing human and wildlife interactions.

Species that are considered invasive are generally species that have been introduced to a non-native environment by humans. Once introduced, some species cannot establish new populations without being moved again by humans while others are capable of dispersing via other means. Vectors are “agents” of dispersal for  plants and animals. Humans are a vector for all species; however, wind, water and animals other than humans are also vectors for dispersal. Species that have many vectors for dispersal are of most concern when introduced to non-native environments. Similarly, species that have wind and birds as vectors for dispersal can be transported long distances in very little time. The species that we should be most concerned about in the context of non-native invasives are species that have very good dispersal ability.

Eastern Prickly Pear Cactus, Optunia humifusa, is native to Ontario and listed as an endangered species. Non-native invasive plants are on of the primary threats to this species in Ontario; however, Eastern Prickly Pear Cactus is a non-native invasive species in Kenya and Australia. Dispersal in its native range and introduced range is primarily via animals and birds that feed on the fruit and seeds of the plant. (Photo: Feltham, 2017)