Plant-eating lizards on the cusp of tooth evolution

Date:
October 15, 2021
Source:
University of Helsinki
Summary:
Researchers found that complex teeth, a hallmark of mammals, also
evolved several times in reptiles, prompting the evolutionary
success of plant- eating lizards. However, contrary to mammals
their tooth evolution was not unidirectional.



FULL STORY ========================================================================== Researchers at the Universities of Helsinki and Lyon and the Geological
Survey of Finland found that complex teeth, a hallmark of mammals, also
evolved several times in reptiles, prompting the evolutionary success of plant-eating lizards. However, contrary to mammals their tooth evolution
was not unidirectional.


==========================================================================
The study, published in Nature Communications, reveals that several
lizard groups evolved teeth with multiple tips ("cusps") that allowed
new plant-based diets and higher speciation rates -- that is, how fast
new species appear.

Surprisingly, tooth evolution was more flexible in lizards and snakes than mammals, revealing a more nuanced view of tooth and dietary evolutionary adaptations in vertebrates.

Tooth shape is closely linked with diet Scientists have richly documented
the connection of tooth shape and diet in mammals, showing very diverse
teeth fuelled their evolutionary success. But what about other toothed
animals? The authors chose to study squamates, the group including lizards
and snakes. "The teeth of squamates have received limited attention,
even though they twice outnumber mammals in species numbers, and span
many habitats and geographic ranges," remarks Nicolas Di-Poi", Associate Professor at the Institute of Biotechnology, University of Helsinki.

The researchers performed comparative analyses on tooth shape and
diet data for more than 500 living and fossil species. They found the
ancestor to all snakes and lizards had simple peg-like teeth and fed on insects. Later, complex teeth bearing multiple cusps -- similar to those
of early mammals -- evolved multiple times independently in different
lizard lineages. The appearance of multiple- cusped teeth allowed some
lizard groups to evolve more plant-rich diets, sometimes leading to even
more complex teeth.

Lizards' teeth evolution took two directions The team also found that
complex teeth and plant consumption provided an evolutionary advantage,
as both traits favoured the appearance of new species.

However, many lizard lineages also lost complex teeth to re-evolve
the ancestral simple tooth morphology. "This came as a complete
surprise," says PhD candidate Fabien Lafuma from the University
of Helsinki, "as complex teeth appear as a critical innovation
for both squamates and mammals." The study suggests that all
land-living vertebrates experience the same selective pressures for
more cusps to increase plant consumption. Nevertheless, fundamental
differences make squamates stand out. Contrary to mammals, tooth
evolution was not unidirectional, and numerous lineages reduced
complexity over time. This difference could stem from variations in
tooth development, showing that minor molecular changes may produce
widely different outcomes over evolutionary time scales. Lafuma
concludes, "this work gives us a more nuanced understanding of how
the same critical adaptation evolved in different vertebrate groups." ========================================================================== Story Source: Materials provided by University_of_Helsinki. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Fabien Lafuma, Ian J. Corfe, Julien Clavel, Nicolas
Di-Po�.

Multiple evolutionary origins and losses of tooth complexity
in squamates. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467-021- 26285-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211015184314.htm

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