Morphological and genetic relationships of Myosotis laxa ssp. baltica and ssp. caespitosa, and typification of M. laxa ssp. baltica

Silvia Pihu,Ene Kook,Maarja Öpik,Ülle Reier

doi:10.5586/asbp.2009.006

Silvia Pihu, Ene Kook + Show 2 more

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https://doi.org/10.5586/asbp.2009.006

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Abstract

Intraspecific taxonomy of Myosotis laxa has been unclear for a long time. M. laxa ssp. baltica has been treated as a microendemic taxon of the Baltic Sea region, which has evolved in the Aland Islands and has spread northwards; the spread to southeast has been declared doubtful. Morphologically intermediate individuals between M. l. ssp. caespitosa and M. l. ssp. baltica exist; these have sometimes been classified as M. l. ssp. laxa. The aim of this paper is to clarify phylogenetic relationships between subspecies of M. laxa s.l. Here, M. laxa ssp. baltica is lectotypified. We proved that typical M. l. ssp. baltica does occur in the south-eastern Baltic region, namely in Estonia, using herbarium and freshly collected material. A group of plants were identified as typical M. l. ssp. baltica, but many specimens showed intermediate characters between M. laxa ssp. baltica and ssp. caespitosa. The two subspecies could be clearly differentiated neither by morphological characteristics nor by ITS sequences. M. laxa s. l. appeared to be monophyletic according to the ITS phylogeny. We propose that Myosotis laxa ssp. baltica is a coastal ecotype of Myosotis laxa, which has adapted to the fluctuating conditions of coastal habitats. Genetically, it has not yet evolved into a separate species and therefore it would be reasonable to assign it a rank of variety. However, further investigation including wider taxon and geographical sampling is needed to finally clarify the position of all subspecies.

Highlights

IntroductionThe genus Myosotis (family Boraginaceae) contains about 100 species and is spread in temperate zones of northern and southern hemisphere
Genus MyosotisThe genus Myosotis contains about 100 species and is spread in temperate zones of northern and southern hemisphere
The majority of the herbarium specimens identified as M. laxa ssp. baltica and several identified as M. laxa or M. l. ssp. caespitosa were examined from the Estonian (TAA, TU) and Scandinavian herbaria (S, H), paying special attention to morphologically typical specimens of M. laxa ssp. baltica

Summary

Introduction

The genus Myosotis (family Boraginaceae) contains about 100 species and is spread in temperate zones of northern and southern hemisphere. Some problematic taxa remain in the genus, for example, the M. laxa complex. The complex contains three subspecies: M. laxa ssp. Caespitosa (Schultz) Hyl. ex Nordh., and M. laxa ssp. M. laxa was described by Lehmann in 1818, being the oldest name in this complex and is used as the species name. It was described as an annual with weak branching and spreading stems, sparse inflorescences, small flowers, and calyces as well as pedicels much elongating after flowering (Lehmann 1818). Lehmann did not designate a type specimen, he only said that he has seen a dried specimen from NorthAmerica (Lehmann 1818), the present location of which is not known

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