Systematic implication of seed micromorphology in Arenaria (Caryophyllaceae) and allied genera

Published Date
Flora - Morphology, Distribution, Functional Ecology of Plants
September 2014, Vol.209(9):513–529, doi:10.1016/j.flora.2014.07.004

Author 

• Somayeh Sadeghian ^a,b
 
• Shahin Zarre ^a,,
 
• Günther Heubl ^c

• aCenter of Excellence in Phylogeny of Living Organisms, and Department of Plant Science, School of Biology, College of Science, University of Tehran, PO Box 14155-6455, Tehran, Iran
• bDepartment of Biology, Faculty of Science, University of Bu-Ali Sina, Hamedan, Iran
• cBiodiversity Research—Systematic Botany, Department of Biology I, Ludwig-Maximilians Universität München, Menzinger Str. 67, D-80638; and GeoBio-Center LMU, München, Germany

Received 29 January 2014. Revised 12 June 2014. Accepted 16 July 2014. Available online 6 August 2014. Edited by R. Lösch.

Highlights

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  Seed micromorphology is useful in delimitation of taxa in Arenaria complex.
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  Colliculate, rugose, papillate, and smooth are the main types of seed sculpturing.
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  Smooth seed surface is a synapomorphy for Arenaria subgen. Leiosperma.
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  Winged seeds characterize Arenaria subgen. Odontostemma.

Abstract

Variations in seed micromorphology of 64 taxa of Arenaria and allied genera were examined using scanning electron microscopy (SEM) in order to evaluate their diagnostic value for systematic studies in the genus and providing additional evidence on delimitation of natural groups. Significant diversity was found in seed coat morphology both among and within genera. Size, color, and shape of seeds appear to be of low importance at species level but provide useful evidence at generic rank. Cerastium and Stellaria are well distinguished from Arenaria by serrate seed margins and solid columellae on testa cells. The sculpturing pattern renders most characters potentially applicable in taxonomy and phylogeny assessment in Arenaria. The studied taxa show four basic types of sculpturing, viz. colliculate, rugose, papillate, and smooth. The colliculate type which is characteristic for the core group of Arenaria (A. subg. Arenaria) can be further divided into five subtypes. The smooth seed surface with indistinct cell boundaries represents a synapomorphy for A.subg. Leiosperma, whereas the winged seeds along with rugose surface characterize subg. Odontostemma. Otherwise seed micromorphology rarely provides adequate evidence for separation of natural groups, especially at sectional rank. We hypothesize that the seeds are highly polymorphic in certain groups of taxa showing recent adaptive radiation, such as the annual species of Arenaria, and do not provide strong support for natural groups within the genus.

© 2014 Elsevier GmbH

Keywords

Caryophyllaceae

SEM

Eremogone

Seed morphology

Taxonomy

Phylogeny

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