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Bottleneck effects in local populations of fossorial Ctenomys (Rodentia, Ctenomyidae) affected by vulcanism

Heredity volume 74, pages 638646 (1995) | Download Citation



Bottleneck effects in three local populations of the fossorial rodent Ctenomys maulinus brunneus as caused by the recent eruption of the Lonquimay volcano in the Andes of Southcentral Chile are presented. Comparative census estimates in Río Colorado indicated a 91.3 per cent decrease in the breeding population size after the catastrophe. All parameters of genetic diversity were drastically affected and surpassed neutral expectations in each population. The proportion of polymorphic loci decreased by 57 per cent, 100 per cent and 83.2 per cent in the bottleneck populations of Río Colorado, Las Raíces and Alto Bío Bío, respectively. The source populations were estimated to have 2.2, 1.5 and 1.4 alleles per locus whereas the three derived populations had estimated values of 1.4, 1.0 and 1.1, respectively. Average heterozygosity dropped by 71 per cent, 100 per cent, and 57 per cent in the same populations, respectively. The spatial genetic structuring observed before the eruption indicated a high degree of population subdivision (Wahlund effect), consistent with an isolation-by-distance model. After the eruption, excessive microspatial genetic differentiation and larger-scale homogeneity indicated drastic disruption of the breeding or social units. Low levels of genetic variation in Andean Ctenomys, claimed to be an adaptive response to the stable subterranean niche, can be attained by the recurrent catastrophe-induced effects of genetic drift.


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  1. Instituto de Ecología y Evolución, Universidad Austral de Chile, Casilla 567, Valdivia, Chile

    • M H Gallardo
    • , N Köhler
    •  & C Araneda


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Correspondence to M H Gallardo.

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