Individuals for which tusk morphology could not be accurately determined are not represented. The pie charts show the proportion of two-tusked (dark blue), single-tusked (blue), and tuskless (light blue) females observed prewar ( n = 54), in survivors of the war ( n = 108), and in the first generation born postwar ( n = 91) on the basis of contemporary surveys and historical photos. The line depicts the minimum elephant population size in Gorongosa National Park by year from aerial censuses ( 30) the dashed segment indicates a period for which no robust census data are available. ( A) Change in population size and tusk morphology. Analyses of historical video footage and contemporary sighting data (supplementary materials) show that the precipitous decline of the Gorongosa elephant population was accompanied by a nearly threefold increase in the frequency of tuskless females, from 18.5% ( n = 52) to 50.9% ( n = 108) (two-sample equality of proportions test with continuity correction, P < 0.001) ( Fig. No record of tuskless male elephants within Gorongosa National Park exists (table S2). Intensive poaching in Africa has been associated with an increase in the frequency of tuskless elephants, exclusively (or nearly so) among females (table S3). In Gorongosa National Park, the Mozambican Civil War (1977 to 1992) reduced large-herbivore populations by >90% ( 15), and armies on both sides of the conflict targeted elephants for ivory ( 15, 16). Warfare is associated with intensified exploitation and population declines of wildlife throughout Africa ( 11), and organized violence has long been intertwined with the ivory trade ( 12– 14). This study provides evidence for rapid, poaching-mediated selection for the loss of a prominent anatomical trait in a keystone species. One of these loci ( AMELX) is associated with an X-linked dominant, male-lethal syndrome in humans that diminishes the growth of maxillary lateral incisors (homologous to elephant tusks). Whole-genome scans implicated two candidate genes with known roles in mammalian tooth development ( AMELX and MEP1a), including the formation of enamel, dentin, cementum, and the periodontium. Survey data revealed tusk-inheritance patterns consistent with an X chromosome–linked dominant, male-lethal trait.
Poaching resulted in strong selection that favored tusklessness amid a rapid population decline.
We examined the impacts of ivory poaching during the Mozambican Civil War (1977 to 1992) on the evolution of African savanna elephants ( Loxodonta africana) in Gorongosa National Park. Understanding the evolutionary consequences of wildlife exploitation is increasingly important as harvesting becomes more efficient.
0 kommentar(er)
