The influence of the 1997-1998 El Niño upon the Galápagos lycosid populations, and a possible role in speciation
Baert, L.; Maelfait, J.-P. (2002). The influence of the 1997-1998 El Niño upon the Galápagos lycosid populations, and a possible role in speciation, in: Toft, S. et al.European arachnology 2000: 19th European Colloquium of Arachnology, Aarhus, Denmark, 17-22 July 2000. pp. 51-56
In: Toft, S.; Scharff, N. (2002). European arachnology 2000: 19th European Colloquium of Arachnology, Aarhus, Denmark, 17-22 July 2000. Aarhus University Press: [s.l.]. ISBN 9788779340015. 358 pp., more
El Niño is a worldwide climatological event occurring every 2 to 8.5 years. This event is associated with high sea-surface temperatures across the tropical Pacific and weak or reversing easterly trade winds. The combination of both leads to abnormally strong convective storms in the eastern Pacific and heavy rainfall in western Latin America (especially Ecuador and Peru) and in the Galápagos. The authors had the opportunity to witness the recent 1997-1998 El Niño event during their stay in the Galápagos in March and April 1998. The effect of extremely wet conditions upon the Hogna albemarlensis populations of the islands Santa Cruz, Santiago and Volcán Cero Azul (Island Isabela) were observed. Hogna albemarlensis, a coastal species, normally lives in saline habitats near lagoons and in permanent wetlands below 600m of altitude. It exhibited an extremely aggressive expansion of its distribution all over the islands and volcanoes, occurring everywhere in very high densities and even outnumbering the highland species Hogna galapagoensis which presumably evolved from the founder species H. albemarlensis. A situation was created in which both the coastal and the highland species, met each other for a certain period of time. Every El Niño event is followed by a number of extremely dry years (called La Niña) resulting in the drying out of all temporary wetlands produced during the El Niño period and once again restricting the lycosid populations to their former areas. El Niños have certainly played an important role in the speciation of the lycosid species on islands where the coastal species and highland species occur. A hypothesis is proposed.
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