2
Tiny Plants with Enormous Potential:
Phylogeny and Evolution
of Duckweeds
Nicholas P. Tippery and Donald H. Les
Abstract
Duckweeds (family Lemnaceae) comprise 37
angiosperm species, which are distributed
among five genera. Although these tiny specimens represent the smallest flowering plants
on earth, the group is practically ubiquitous in
water bodies worldwide. The paucity of morphological features in duckweeds has made it
difficult to elucidate their evolutionary history,
or to present a compelling classification of the
group, but more recent molecular evidence has
facilitated an improved systematic evaluation
of these unique plants. The duckweeds are
closely related to aroids (family Araceae), with
which they share several morphological features. Within Lemnaceae, the two species of
Spirodela and the monotypic genus Landoltia
are more distantly related to other duckweeds
than are the larger genera Lemna, Wolffia, and
Wolffiella to one another. A substantial amount
of plastid DNA sequence data has upheld a
phylogeny for the family that is mostly
consistent, and many of those relationships
have been corroborated by the recent addition
of nuclear DNA data. Morphologically, the
genera lacking roots (Wolffia and Wolffiella)
comprise a single lineage, as do the three
largest genera (Lemna, Wolffia, and Wolffiella)
that are more reduced in comparison with
Landoltia and Spirodela. The biogeography of
Lemnaceae indicates that numerous dispersal
events have occurred in relatively recent
evolutionary time, and that several species
essentially are cosmopolitan. Although not
particularly speciose, duckweeds comprise a
surprisingly diverse group with much potential
for exploring various genetic, biochemical,
and metabolic phenomena.
2.1 Introduction
Duckweeds (family Lemnaceae) are a common
floristic element of freshwater aquatic habitats
worldwide, where they often cover large portions
of the water surface. Their growth form, in which
the entire plant body floats on or is suspended
beneath the water surface, is uncommon among
aquatic plants, and their extreme morphological
reduction makes them truly unique. Among the
reduced features are leaves and stems, which are
collectively subsumed into a simplified structure
known as a “frond,” and roots, which are entirely
lacking in two genera (Wolffia and Wolffiella).
Vegetative reproduction commonly occurs by the
budding of additional fronds that can separate
from the parent frond, as well as by producing
N. P. Tippery
Department of Biological Sciences, University of
Wisconsin, Whitewater, USA
D. H. Les (&)
Department of Ecology and Evolutionary Biology,
University of Connecticut, Connecticut, USA
e-mail: les@uconn.edu
© Springer Nature Switzerland AG 2020
X. H. Cao et al. (eds.), The Duckweed Genomes, Compendium of Plant Genomes,
https://doi.org/10.1007/978-3-030-11045-1_2
19
Tiny Plants with Enormous Potential:
Phylogeny and Evolution
of Duckweeds
Nicholas P. Tippery and Donald H. Les
Abstract
Duckweeds (family Lemnaceae) comprise 37
angiosperm species, which are distributed
among five genera. Although these tiny specimens represent the smallest flowering plants
on earth, the group is practically ubiquitous in
water bodies worldwide. The paucity of morphological features in duckweeds has made it
difficult to elucidate their evolutionary history,
or to present a compelling classification of the
group, but more recent molecular evidence has
facilitated an improved systematic evaluation
of these unique plants. The duckweeds are
closely related to aroids (family Araceae), with
which they share several morphological features. Within Lemnaceae, the two species of
Spirodela and the monotypic genus Landoltia
are more distantly related to other duckweeds
than are the larger genera Lemna, Wolffia, and
Wolffiella to one another. A substantial amount
of plastid DNA sequence data has upheld a
phylogeny for the family that is mostly
consistent, and many of those relationships
have been corroborated by the recent addition
of nuclear DNA data. Morphologically, the
genera lacking roots (Wolffia and Wolffiella)
comprise a single lineage, as do the three
largest genera (Lemna, Wolffia, and Wolffiella)
that are more reduced in comparison with
Landoltia and Spirodela. The biogeography of
Lemnaceae indicates that numerous dispersal
events have occurred in relatively recent
evolutionary time, and that several species
essentially are cosmopolitan. Although not
particularly speciose, duckweeds comprise a
surprisingly diverse group with much potential
for exploring various genetic, biochemical,
and metabolic phenomena.
2.1 Introduction
Duckweeds (family Lemnaceae) are a common
floristic element of freshwater aquatic habitats
worldwide, where they often cover large portions
of the water surface. Their growth form, in which
the entire plant body floats on or is suspended
beneath the water surface, is uncommon among
aquatic plants, and their extreme morphological
reduction makes them truly unique. Among the
reduced features are leaves and stems, which are
collectively subsumed into a simplified structure
known as a “frond,” and roots, which are entirely
lacking in two genera (Wolffia and Wolffiella).
Vegetative reproduction commonly occurs by the
budding of additional fronds that can separate
from the parent frond, as well as by producing
N. P. Tippery
Department of Biological Sciences, University of
Wisconsin, Whitewater, USA
D. H. Les (&)
Department of Ecology and Evolutionary Biology,
University of Connecticut, Connecticut, USA
e-mail: les@uconn.edu
© Springer Nature Switzerland AG 2020
X. H. Cao et al. (eds.), The Duckweed Genomes, Compendium of Plant Genomes,
https://doi.org/10.1007/978-3-030-11045-1_2
19