Morphological response of planktic foraminifers to habitat modifications associated with the emergence of the Isthmus of Panama
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The impact of global change on marine ecosystems is a major concern for the future. Examples from the geological past may provide insight into how ecosystems respond to major shifts in environment. Here we use the progressive closure of the Central American Seaway over the last 10 Myrs, and the resulting new environmental conditions and niches on either side of the Panama Isthmus, as a time series documenting the reaction of planktic foraminifers to environmental change and vicariance. Our main finding is that the size and shape evolution of both investigated species is strongly influenced by temperature, despite their different ecology. The surface dweller Trilobatus sacculifer conserved the same shape on both sides of the Isthmus for most of the studied interval, and diverged only recently when environment diverged on both sides of the Isthmus. The shape response is a combination of a change in mean shape and in percentage of morphotypes occurring within T. sacculifer. This suggests a minor role of vicariance and the potential to react to changes in the local environment through ecotypic or plastic variation. This interpretation is corroborated by extensive phenotypic variability in the absence of genetic differentiation today in this species. The shape of the deeper-living species Gt. tumida, in contrast, diverged on both sides of the Isthmus at a time that coincides with the cut-off of the connection of its habitat. This divergence combines a response to temperature and to location, suggesting local adaptation in response to vicariance. These different reactions highlight both a high potential for adaptation, but also sensitivity to temperature variations. The species-specific responses to environmental pressures indicate the difficulty in upscaling from one species to foraminifers in general.
Schmidt , D , Caromel , A , Seki , O , Rae , J W B & Renaud , S 2016 , ' Morphological response of planktic foraminifers to habitat modifications associated with the emergence of the Isthmus of Panama ' Marine Micropaleontology , vol 128 , pp. 28-38 . DOI: 10.1016/j.marmicro.2016.08.003
© 2016 Elsevier B.V. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at http://dx.doi.org/10.1016/j.marmicro.2016.08.003
The authors would like to thank NERC for funding AGMC (NE/G524228/1) and JWBR (NE/F007345/1) via PhD studentships and the Royal Society for funding DNS via a University Research Fellowship and a Wolfson Merit Award. The work was supported by NERC grant NE/H006273/1. OS acknowledges the Ministry of Education, Culture, Sports, Science and Technology for funding via Japan Society of Promotion of Science (No. 1800410000) enabling the research at Bristol. The data is deposited at www.pangaea.de, (doi:10.1594/PANGAEA.837987).
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