August 24, 2016 by Bob
Yirka
(Phys.org)—A team of researchers
with Villanova University in the U.S. and associates from South Africa, Germany
and Switzerland has found via genetic study that extreme matrotrophy evolved
just once in African mabuyine skink. In their paper published in the
journal Biology Letters, the researchers describe how they ventured
to Zambia and Angola to obtain skink samples and then conducted DNA tests on
them to create family trees which allowed them to learn more about the
evolutionary history of matrotrophy in skinks.
Skinks are lizards with smooth
bodies and short or even absent limbs. Quite often, they look like snakes. In
this new effort, the researchers sought to learn more about a certain group of
them—those that reproduce using a process called extreme matrotrophy. Instead
of simply delivering their young through live birth, or by laying eggs, as is
done by most other lizards and snakes, some skinks provide nutrients to their
embryos through a placenta—a form of extreme live birth. But has such an
ability evolved more than once in different species, or are all such skinks
related to a common ancestor? That is what the researchers wanted to know. To
find out, they collected multiple samples representing multiple different
species, took them back to their lab and set about reconstructing their evolutionary history via
genetic study (using multilocus DNA data). They then compared their results
with species obtained from other sites in Asia and the Neotropics.
The team reports that testing
suggests one likely evolutionary moment that led to matrotrophy in
Africa—though they could not rule out the possibility of a second. The data
also indicated that there may have been another unassociated moment in the
Neotropics. Taken together, the evidence indicates the likelihood that there
were no more than three moments (leading to the evolution of three sister
groups) that led to matrotrophy in the three groups that make up skink ancestry
(which includes 66 species). The results also showed a lot of similarity
between the ways mammalian reproduction evolved and placental development in
skink ancestors.
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