(August 10, 2015) A
lizard lineage which has evolved over the last 19 million years has helped
scientists to re-think one of the most important concepts of modern biology.
‘Adaptive radiation’ is recognised as a pillar of
evolutionary science. It describes the development of new biodiversity, and is
triggered when a species encounters a new environment with plenty of available
resources – this is called ‘ecological opportunity’. This single species then
makes the most of these resources and multiplies rapidly into several new
forms. When all these resources have been used up by new species, the process
of biodiversity proliferation slows down dramatically.
‘Early-bursts’ of new species diversification have
previously been seen as a central part of this process – scientists have for
decades referred to this trend as a key component of adaptive radiation.
However, new research published in the academic journal BMC Evolutionary
Biology suggests that the term should not be defined by these early rapid
surges.
The revelation comes from scientists at the University of
Lincoln, UK, who have been investigating the evolution of the Liolaemus lizard
– one of the most species-rich and ecologically diverse lineages of
vertebrates.
Their study suggests that the gradual uplifts of the Andes
mountain range in South America over millions of years led to the episodic
emergence of ecological opportunity, which in turn caused several waves of
diversification in this group of lizards. As a result, they found a number of
peaks of originations diversification of new Liolaemus lizard species, rather
than one ‘early-burst’.
Dr Daniel Pincheira-Donoso, Senior Lecturer in the School of
Life Sciences at the University of Lincoln, explained: “Our research shows that
the diversification of the Liolaemus lizards has occurred in a number of
episodes over an extended period of time. As the Andes uplifted, new ecological
opportunity continued to emerge and new bursts of diversification took place –
there was never an early explosion followed by a slow-down, but instead,
constant pulses of new species evolution.