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Calibration of the repeatability of foraminiferal test size and shape measures with recommendations for future use

Calibration of the repeatability of foraminiferal test size and shape measures with recommendations for future use
Calibration of the repeatability of foraminiferal test size and shape measures with recommendations for future use
The fossil record of planktonic foraminifera is ideally suited to defining stratigraphic age controls and exploring fundamental questions in evolutionary biology due to its excellent preservation potential that yields continuous, high-resolution fossil archives of large numbers of individuals. For full morphometric analyses foraminifera tests are generally mounted, oriented and imaged manually, while data are processed using standard software such as ImageJ or Image Pro. However, manually induced orientation errors are a source of potential bias in trait measurements even when quantified using the same computational subroutine. Here we test the repeatability of four measures of foraminiferal test shape on six morphologically distinct species and present a calibration (power analysis) of the number of individuals needed to determine a given percentage change in these traits. We mounted and measured every individual twice and analysed the difference between the two measurements to determine the effects of small orientation changes on the studied traits. We show that measurements of test area and aspect ratio are statistically indistinguishable between runs for all species studied, and a power law calibration suggests that between 25 and 50 individuals are needed to detect at least a 10% in- or decrease in either trait. However, despite mounting tests on glass slides to clarify perimeter outlines, test perimeter was only repeatable in the spherical species Orbulina universa, and test roundness was not repeatable for three out of six studied species. We recommend the use of lengths and avoidance of perimeters and their dependent metrics to reduce orientation induced bias.
0377-8398
21-27
Brombacher, Anieke
2a4bbb84-4743-4a36-973b-4ad2bf743154
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Ezard, Thomas H.g.
a143a893-07d0-4673-a2dd-cea2cd7e1374
Brombacher, Anieke
2a4bbb84-4743-4a36-973b-4ad2bf743154
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Ezard, Thomas H.g.
a143a893-07d0-4673-a2dd-cea2cd7e1374

Brombacher, Anieke, Wilson, Paul A. and Ezard, Thomas H.g. (2017) Calibration of the repeatability of foraminiferal test size and shape measures with recommendations for future use. Marine Micropaleontology, 133, 21-27. (doi:10.1016/j.marmicro.2017.05.003).

Record type: Article

Abstract

The fossil record of planktonic foraminifera is ideally suited to defining stratigraphic age controls and exploring fundamental questions in evolutionary biology due to its excellent preservation potential that yields continuous, high-resolution fossil archives of large numbers of individuals. For full morphometric analyses foraminifera tests are generally mounted, oriented and imaged manually, while data are processed using standard software such as ImageJ or Image Pro. However, manually induced orientation errors are a source of potential bias in trait measurements even when quantified using the same computational subroutine. Here we test the repeatability of four measures of foraminiferal test shape on six morphologically distinct species and present a calibration (power analysis) of the number of individuals needed to determine a given percentage change in these traits. We mounted and measured every individual twice and analysed the difference between the two measurements to determine the effects of small orientation changes on the studied traits. We show that measurements of test area and aspect ratio are statistically indistinguishable between runs for all species studied, and a power law calibration suggests that between 25 and 50 individuals are needed to detect at least a 10% in- or decrease in either trait. However, despite mounting tests on glass slides to clarify perimeter outlines, test perimeter was only repeatable in the spherical species Orbulina universa, and test roundness was not repeatable for three out of six studied species. We recommend the use of lengths and avoidance of perimeters and their dependent metrics to reduce orientation induced bias.

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More information

Accepted/In Press date: 23 May 2017
Published date: 26 May 2017
Organisations: Ocean and Earth Science, Southampton Marine & Maritime Institute, Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 410074
URI: http://eprints.soton.ac.uk/id/eprint/410074
ISSN: 0377-8398
PURE UUID: a3fda477-e80b-4985-9b22-2fe0b990d1b7
ORCID for Thomas H.g. Ezard: ORCID iD orcid.org/0000-0001-8305-6605

Catalogue record

Date deposited: 03 Jun 2017 04:02
Last modified: 17 Dec 2019 06:07

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