Galapagos Islands. The data in Display 12.17 come from a 1973 study. (Data from
ID: 3282641 • Letter: G
Question
Galapagos Islands. The data in Display 12.17 come from a 1973 study. (Data from M. P. Johnsoin and P. H. Raven, "Species Number and Endemism: The Galapagos Archipelago Revisited," Science 179 (1973): 893-5.) The number of species on an island is known to be related to the island's area. Of interest is what other variables are also related to the number of species, after island area is accounted for, and whether the answer differs for native species and nonnative species. (Note: Elevations for five of the islands were missing and have been replaced by estimates for purposes of this exercise.) DISPLAY 12.17 Plant species and geography of the Galapagos Islands; first 5 rows of 30 Observed species Distance(km) From nearest island Cruz (km Area of From nearest island Area Elevation Island Toal Native (km2) 332 109 114 1.84 26.3 572.33 0.78 0.18 1.9 903.82 23 21 Baltra Bartolome Caldwell Champion 25.09 1.24 0.21 0.10 1.05 0.6 0.6 2.8 1.9 1.9 58 31 0.6 58.7 47.4 25 130Explanation / Answer
Those species comprising the trial vertebrate groups (birds, mammals, reptiles, and amphibians; 258 species) and plants (87 species) were considered further. Species accounts were used to classify each species as being from a mainland or an island. Only species restricted to islands were listed as “island” species. Included in these tallies are three marine mammals, which we listed as “mainland” for the purposes of these analyses. Species accounts were also used to tally the factors listed as having contributed to species extinction. To do so, both the annotated list of contributing factors, and the text description were examined for each species. We classified extinction factors into three categories: predation, competition, and other factors. Predation includes pairwise species interactions that are positive for one species and negative for the other; this included any of the following: human hunting (including any form of direct human exploitation of a species), carnivorous predation, herbivorous predation, parasitism, and infectious disease. “Competition” included interactions where species competed for resources. All other factors, such as habitat loss and pollution, were considered to be “other factors.” Tallies were compiled for species listed as (i) only being impacted by predation, (ii) impacted by predation together with other factors, and (iii) impacted by competition together with other factors. In no case was competition listed as the sole factor causing a species extinction. These same tallies were repeated for the subset of extinct species listed as having been impacted by an “alien,” i.e., nonnative or exotic, species.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.