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Morphospaces, Morphometrics, and Phylogenetics

Kriebel, Ricardo [1], Berger, Brent [2], Spalink, Daniel [3], Reginato, Marcelo [4], Sytsma, Kenneth J. [5].

The evolution of shape and size in the pollen of Myrtales.

Pollen is one of the best documented morphological structures in the order Myrtales. Since the start of systematic studies within the order, knowledge on pollen morphology contributed cladistic characters for phylogenetic analyses and more recently pollen characters have been mapped onto molecular phylogenies, and fossil grains used to time calibrate these phylogenies. While some pollen characters are easy to code in a discrete way (absence or presence of viscin threads), others have been recognized as problematic (absence or presence of pseudocolpi, and “more or less oblate” pollen shape). Here we study pollen shape and size in the order Myrtales in a continuous way using morphometrics and test previous hypotheses about pollen shape evolution in the order. Pollen grains were extracted from the literature, measured, and outlines of the grains made for both equatorial and polar views. Elliptic Fourier analysis was used to obtain a morphospace and extract shape variables for both pollen views. The shape data was subsequently added to the size data and both matched to the most recent phylogeny of Myrtales, as well to a new phylogeny resulting from a super matrix of twelve genes. These phylogenies were used to reconstruct ancestral pollen shape and size, visualize occupation of space by the different families with a phylomorphospace approach, and test for significant shifts in pollen traits during the evolutionary history of Myrtales. In addition, we used this data to place the fossil pollen grain Heterocolpites paleaocenica, which was described as likely belonging to the Melastomataceae, into the phylogeny of extant species. A total of 444 pollen grains were included in the analysis of equatorial view and 583 grains in the analysis of polar view. In general, the historical use of oblate pollen shape in equatorial view as distinctive for Myrtaceae and Onagraceae is supported by the morphometric data. Shifts in the evolution of shape from heterocolpate and rounded to triangular and flattened were detected independently in the families Myrtaceae and Onagraceae, and a shift in size from small to large in the Onagraceae. The Heterocolpites pollen was not placed in the Melastomataceae in the most likely phylogenies, nor when incorporating uncertainty over randomly sampled trees. Extensions of the utility of elliptic Fourier analysis to quantify other floral structures of Myrtales will be discussed.


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1 - University of Wisconsin, Department of Botany, 430 Lincoln Drive, Madison, WI, 53706, United States
2 - St. John's University, 8000 Utopia Parkway, Queens, NY, 11439, USA
3 - University Of Wisconsin-Madison, Department Of Botany, 430 Lincoln Drive, Madison, WI, 53706, USA
4 - The New York Botanical Garden, 2900 Southern Blvd, Bronx, NY, 10458-5126, United States
5 - University of Wisconsin, Department of Botany, 430 Lincoln Drive, Madison, WI, 53706, USA

Keywords:
elliptic Fourier analysis
Morphometrics
Myrtales
Phylogeny
pollen.

Presentation Type: Symposium Presentation
Session: SY06
Location: Salon 10/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 4:15 PM
Number: SY06007
Abstract ID:1192
Candidate for Awards:None


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