It has been suggested that kin groups are better predisposed to cooperatively manage essential natural resources than non-kin groups because of inclusive fitness gains. Whether these long-term genetic pay-offs sufficiently offset the immediate costs of cooperation in periods of scarcity is uncertain. We compared patterns of resource sharing across three island communities in the Nicobar Archipelago affected by the 2004 tsunami. While sharing mechanisms were similar across regions, group composition varied: Central and Southern Nicobar were organised along kinship lines, while Chowra was organised as corporate alliances of unrelated households. We documented post-tsunami losses and conflicts emerging in resource sharing after the event. While kin groups showed considerable breakdown in resource sharing arrangements, corporate communities in Chowra were much more resilient to change. Our results suggest that the more immediate reciprocity of corporate alliances may outweigh the potential benefits of inclusive fitness when faced with conditions of extreme resource scarcity.