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10 Apr 2019

Secrets of carnivorous plant evolution

A carnivorous plant family has evolved three genera that each employ extraordinary strategies to exploit both flying insects and aquatic microscopic crustaceans and algae.

Bladderworts (Utricularia; Lentibulariaceae) were a favourite of Charles Darwin and have proved to be an excellent way to study plant ecology and evolution.

Recent work by researchers from across the world has helped us understand the ecology, physiology and evolution of these extraordinary carnivorous plants.

Bladderworts exhibit an enormous diversity across their worldwide distribution with adaptions that allow them to thrive in habitats ranging from Bromeliad tanks in the tree-tops of tropical cloud forests, fast-flowing streams, near-arctic lakes, alpine bogs, and remote mound-springs of Australia’s Great Artesian Basin.

Above is an image of an aquatic Utricularia showing bladder traps.
An aquatic Utricularia showing bladder traps.

Carnivorous strategies

Flowers can range from 40 mm long in the orchid-like Brazilian epiphytes, to some of the smallest flowers in the plant world at just a few millimetres long in the Australian species U. simmonsii.

Likewise, the carnivorous bladder-traps vary widely in size from a few millimetres long to about 13 mm long in the Australian tropical species U. arnhemica.

The flowering plant family Lentibulariaceae includes three genera that have evolved incredible carnivorous strategies: Butterworts (Pinguicula) capture insects on the sticky upper-leaf surfaces, the Lobsterpots (Genlisea) trap microscopic prey in passive helically shaped subterranean tubes, and Bladderworts (Utricularia) trap small aquatic creatures in active suction bladder traps.

Pinguicula have thick fleshy leaves that are super-sticky.

Diverse habitats and fast traps

Butterworts are found across Asia, Europe and Central and North America; Corkscrew plants are found in Africa and South America, while about 250 species of Bladderworts are found across the world with Australia having about 58 species of which 42 are endemic.

Provided the habitat has low nutrient soil and water, there is a strong chance your local swamp will contain a Bladderwort species or three.

The bladder traps of Bladderworts are a water-filled vesicle with a hinged door at on end. Specialised glands upon the trap surface pump 40% of the internal water to the outside creating a negative internal pressure.

This negative pressure is released when a prey, such as a small crustacean of about half a millimetre in length, touches the trigger hairs. It is sucked into the trap within about 20 thousandths of a second – this repeatable process is one of the fastest carnivorous plant movements.

Once a prey organism finds itself imprisoned, the plants’ enzymes and bacteria quickly turn it into a feast for the Bladderwort.

Aquatic carnivorous bladderworts (Utricularia species) catch prey animals with suction traps. High speed video recordings show that the plant "swallows" its prey in less than a millisecond.

What a wonderful and long-continued series of variations must have led up to the perfect ‘‘trap’’ in Utricularia, while at any stage of the process the same end might have been gained by a little development of roots and leaves, as in 9,999 plants out of 10,000!
Alfred Russel Wallace, from a letter to Charles Darwin dated 21 July 1875 (Marchant, 1916, p. 234)

Evolutionary marvels

I specialise in the study of the evolution within the Lentibulariaceae family. My work has helped untangle relationships between the Butterworts, Lobsterpots and Bladderworts.  

These studies also led to uncovering excessive rates of molecular evolution and molecular energetic adaptations in the Bladderworts as compared to Butterworts and other flowering plants.

For example, they have lost the typical flowering plant-bodyplan, namely roots and shoots. Lobsterpots and Bladderworts also possess the smallest genomes known in plants, having purged almost all the “junk” DNA that occupies the genomes of most other plants.

With the help of a team of US researchers, I'm currently sequencing genomes from across the Lentibulariaceae family to gain some understanding of these evolutionary processes. The full genomes of three Australian species are already sequenced and assembled, with fifteen more in the works.

Dr Richard Jobson collecting aquatic plants in Queensland.

Untangling the DNA

In my most recent work with PhD student Paulo Baleeiro we found that a single South American species complex was instead an assemblage of at least six species. One of these species is only known from a single Brazilian waterfall, highlighting the link between understanding biodiversity and conservation.

One of the several Australian complexes currently being studied, the Fairy aprons (Utricularia dichotoma) uncovered five new species and seven new subspecies. One of these species is only known from two remote Artesian mound springs in far western Queensland.

The same study also provided the evidence for reinstating two species originally named by Robert Brown (the namesake of the NSW Herbarium Building) in 1804 from his collections in the Sydney basin.

While fieldwork provides some material required for studies, and they have taken me to many remote regions of Australia and the world, preserved herbarium material is also an essential element for providing data on morphological characters and DNA markers for phylogenetic studies of evolutionary relationships.

Dr Richard Jobson
Remote fieldwork is essential for studying plants.

Plants with Bite

There is so much more to learn about carnivorous plants plus a wide variety of unique shapes and colours to see. 

Plants with Bite, the carnivorous plant display at The Calyx, has over 7,000 carnivorous plants (18,000 plants altogether) - so you don't have to endure tropical rainstorms or trudge through muddy swamps to see Bladderworts up close.

Bladderworts and a range of other carnivorous plants can be seen in the Plants with Bite display. (Pictured an endangered U.singeriana) 

About Dr Richard Jobson

Dr Jobson has been studying carnivorous plants since his early postgraduate years working on their ecology and diet and has been growing them since childhood.

He has also studied the evolution of the Droseraceae family (Venus fly traps, Tropical pitcher plants and Sundews) uncovering the sister relationship between the terrestrial Dionaea (Venus fly trap) and aquatic Aldrovanda (Waterwheel plant). 

This provided evidence that the snap trap innovation evolved just once in the common ancestor of these two genera. His work on understanding Bladderwort evolution has led to the recent publication of 15 new Australian species.

U.hamiltonii_TopEnd plants with bite royal botanic garden
Utricularia hamiltonii - simple beauty, complex evolution. 
Find out more about Plants with Bite.
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