TEMPERATURE INDUCED BODY SIZE INCREASE IN A BENTHIC MARINE MOLLUSK FAUNA FROM SEYMOUR ISLAND, ANTARCTICA
We measured body size of gastropod lineages including taxa from the nassariids, buccinids, and struthiolariids as well as one bivalve genus Eurhomalea sp. spanning this time period. Our samples included 1669 individuals from over 100 localities. Preliminary results indicate that body size in the gastropod lineages increased on average 26% when the climate cooled. This trend can also be observed in the size data of the bivalve taxon from the same layers (increase of 7%).
Reasons for this phenomenon are still widely discussed. Putative causes range from adaptive theories of cost-benefit of certain life-history traits connected to e.g., early maturity at small sizes in warm climate to non-adaptive models explaining the pattern with temperature dependent biochemical processes at cellular and molecular levels. Although causes are still debated, our data supports the notion that evidence for the temperature-size rule is not limited to spatial body size clines in the recent, but can also be observed temporally in the fossil record.