Trends in the sand: Directional evolution in the shell shape of recessing scallops (Bivalvia: Pectinidae)

Directional evolution is one of the most compelling evolutionary patterns observed in macroevolution. Yet, despite its importance, detecting such trends in multivariate data remains a challenge. In this study, we evaluate multivariate evolution of shell shape in 93 bivalved scallop species, combinin...

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Bibliographic Details
Published in:Evolution 2016-09, Vol.70 (9), p.2061-2073
Main Authors: Sherratt, Emma, Alejandrino, Alvin, Kraemer, Andrew C., Serb, Jeanne M., Adams, Dean C.
Format: Article
Language:English
Subjects:
Animals
Biological Evolution
Bivalvia
Directional evolution
Evolution
geometric morphometrics
Macroevolution
mollusca
Pectinidae
Pectinidae - anatomy & histology
Pectinidae - classification
Phylogenetics
Phylogeny
Species Specificity
Trends
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Summary:Directional evolution is one of the most compelling evolutionary patterns observed in macroevolution. Yet, despite its importance, detecting such trends in multivariate data remains a challenge. In this study, we evaluate multivariate evolution of shell shape in 93 bivalved scallop species, combining geometric morphometrics and phylogenetic comparative methods. Phylomorphospace visualization described the history of morphological diversification in the group; revealing that taxa with a recessing life habit were the most distinctive in shell shape, and appeared to display a directional trend. To evaluate this hypothesis empirically, we extended existing methods by characterizing the mean directional evolution in phylomorphospace for recessing scallops. We then compared this pattern to what was expected under several alternative evolutionary scenarios using phylogenetic simulations. The observed pattern did not fall within the distribution obtained under multivariate Brownian motion, enabling us to reject this evolutionary scenario. By contrast, the observed pattern was more similar to, and fell within, the distribution obtained from simulations using Brownian motion combined with a directional trend. Thus, the observed data are consistent with a pattern of directional evolution for this lineage of recessing scallops. We discuss this putative directional evolutionary trend in terms of its potential adaptive role in exploiting novel habitats.
ISSN:0014-3820
1558-5646
DOI:10.1111/evo.12995