Dear All,
this is out now:
https://link.springer.com/article/10.1007/s11692-021-09531-3
On the Misidentification of Species: Sampling Error in Primates and
Other Mammals Using Geometric Morphometrics in More Than 4000 Individuals
Andrea Cardini, Sarah Elton, Kris Kovarovic, Una Strand Viđarsdóttir &
P. David Polly - Evolutionary Biology (2021)
The abstract is below.
For a couple of days, I'll leave a pdf copy at
https://tinyurl.com/speciesmisid
The focus is morphospecies in living mammals but has potential
implications beyond that (especially in palaeo).
Cheers
Andrea
On the Misidentification of Species: Sampling Error in Primates and
Other Mammals Using Geometric Morphometrics in More Than 4000 Individual
Abstract
An accurate classification is the basis for research in biology.
Morphometrics and morphospecies play an important role in modern
taxonomy, with geometric morphometrics increasingly applied as a
favourite analytical tool. Yet, really large samples are seldom
available for modern species and even less common in palaeontology,
where morphospecies are often identified, described and compared using
just one or a very few specimens. The impact of sampling error and how
large a sample must be to mitigate the inaccuracy are important
questions for morphometrics and taxonomy. Using more than 4000 crania of
adult mammals and taxa representing each of the four placental
superorders, we assess the impacts of sampling error on estimates of
species means, variances and covariances in Procrustes shape data using
resampling experiments. In each group of closely related species (mostly
congeneric), we found that a species can be identified fairly accurately
even when means are based on relatively small samples, although errors
are frequent with fewer specimens and primates more prone to
inaccuracies. A precise reconstruction of similarity relationships, in
contrast, sometimes requires very large samples (> 100), but this varies
widely depending on the study group. Medium-sized samples are necessary
to accurately estimate standard errors of mean shapes or intraspecific
variance covariance structure, but in this case minimum sample sizes are
broadly similar across all groups (≈ 20–50 individuals). Overall, thus,
the minimum sample sized required for a study varies across taxa and
depends on what is being assessed, but about 25–40 specimens (for each
sex, if a species is sexually dimorphic) may be on average an adequate
and attainable minimum sample size for estimating the most commonly used
shape parameters. As expected, the best predictor of the effects of
sampling error is the ratio of between- to within-species variation: the
larger the ratio, the smaller the sample size needed to obtain the same
level of accuracy. Even though ours is the largest study to date of the
uncertainties in estimates of means, variances and covariances in
geometric morphometrics, and despite its generally high congruence with
previous analyses, we feel it would be premature to generalize. Clearly,
there is no a priori answer for what minimum sample size is required for
a particular study and no universal recipe to control for sampling
error. Exploratory analyses using resampling experiments are thus
desirable, easy to perform and yield powerful preliminary clues about
the effect of sampling on parameter estimates in comparative studies of
morphospecies, and in a variety of other morphometric applications in
biology and medicine. Morphospecies descriptions are indeed a small
piece of provisional evidence in a much more complex evolutionary
puzzle. However, they are crucial in palaeontology, and provide
important complimentary evidence in modern integrative taxonomy. Thus,
if taxonomy provides the bricks for accurate research in biology,
understanding the robustness of these bricks is the first fundamental
step to build scientific knowledge on sound, stable and long-lasting
foundations.
--
Dr. Andrea Cardini
Researcher, Dipartimento di Scienze Chimiche e Geologiche, Università di
Modena e Reggio Emilia, Via Campi, 103 - 41125 Modena - Italy
tel. 0039 059 4223140
Adjunct Associate Professor, Centre for Forensic Anthropology, The
University of Western Australia, 35 Stirling Highway, Crawley WA 6009,
Australia
E-mail address: [email protected], [email protected]
WEBPAGE: https://sites.google.com/view/alcardini2/
or https://tinyurl.com/andreacardini
FREE Yellow BOOK on Geometric Morphometrics:
https://tinyurl.com/yellowmorphobook
ESTIMATE YOUR GLOBAL FOOTPRINT:
http://www.footprintnetwork.org/en/index.php/GFN/page/calculators/
SUPPORT: secondwarning.org
--
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