Mar 12, 2008

Evolutionary responses to environmental heterogeneity in central american echinoid larvae: plastic versus constant phenotypes

Evolution; International Journal of Organic Evolution
Justin S McAlister

Abstract

Do changes in food resources lead to evolutionary changes in phenotypic plasticity or in different constant phenotypes? I addressed this question by studying plasticity of larval feeding arms for "geminate species pairs" in three echinoid genera. These closely related species were geographically isolated when the Panamanian Isthmus raised 2.8-3.1 million years ago, creating two different food level environments: high but variable food levels in the eastern Pacific versus chronically low food levels in the western Caribbean. I reared larvae of geminate species in different replicated food environments for 10 days postfertilization, collected morphological measurements of individual arm and body lengths, and calculated degrees of plasticity of relative arm length for each species. In contrast to previous studies with temperate echinoids, there was no significant plasticity of arm length in either the Pacific or Caribbean species considered here. Caribbean species, however, had significantly longer relative arm lengths than Pacific species, regardless of food levels. These results suggest that historical changes in food levels have led to the evolution of constant rather than plastic differences between Pacific and Caribbean echin...Continue Reading

  • References18
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Mentioned in this Paper

Echinometra
Embryo
Neuro-Oncological Ventral Antigen 2
Echinometra lucunter
Diadema
Eucidaris
Larval Development
Isthmus of the Cingulate Gyrus
Chlorophyll a
Larva

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