Passage 1 is adapted from “,” © 2005 by Public Library of Science. Passage 2 is adapted from Tim Heupink, et al. “,” © 2014 by Tim Heupink, et al.
Passage 1
For reasons that are not entirely clear, when animals make
their way to isolated islands, they tend to evolve relatively
quickly toward an outsized or pint-sized version of their
mainland counterpart.
Perhaps the most famous example of an island giant—and,
sadly, of species extinction—is the dodo, once found on the
Indian Ocean island of Mauritius. When the dodo’s ancestor
(thought to be a migratory pigeon) settled on this island with
abundant food, no competition from terrestrial mammals, and
no predators, it could survive without flying, and thus was
freed from the energetic and size constraints of flight. New
Zealand also had avian giants, now extinct, including the
flightless moa, an ostrich-like bird, and Haast’s eagle
(Harpagornis moored), which had a wingspan up to 3
meters. Though Haast’s eagle could fly—and presumably
used its wings to launch brutal attacks on the hapless moa—
its body mass (10–14 kilograms) pushed the limits for self-
propelled flight.
As extreme evolutionary examples, these island birds can
offer insights into the forces and events shaping evolutionary
change. In a new study, Michael Bunce et al. compared
ancient mitochondrial DNA extracted from Haast’s eagle
bones with DNA sequences of 16 living eagle species to
better characterize the evolutionary history of the extinct
giant raptor. Their results suggest the extinct raptor
underwent a rapid evolutionary transformation that belies its
kinship to some of the world’s smallest eagle species.
The authors characterized the rates of sequence evolution
within mitochondrial DNA to establish the evolutionary
relationships between the different eagle species. Their
analysis places Haast’s eagle in the same evolutionary lineage
as a group of small eagle species in the genus Hieraaetus.
Surprisingly, the genetic distance separating the giant eagle
and its more diminutive Hieraaetus cousins from their last
common ancestor is relatively small.
Passage 2
The mysterious spotted green pigeon (Caloenas maculata)
was a relative of the dodo, according to scientists who have
examined its genetic make-up. The authors say their results,
published in the open access journal BMC Evolutionary
Biology, support a theory that both birds are descended from
“island hopping” ancestors.
The scientists took DNA from two feathers of the spotted
green pigeon. Because of its age, the DNA was highly
fragmented, so they focused in on three DNA “mini
barcodes” – small sections of DNA which are unique for
most bird species. They looked at these sections of the
pigeon’s DNA, and compared it to other species.
This showed that the spotted green pigeon is indeed a
separate species, showing a unique DNA barcode compared
to other pigeons. The pigeon is genetically most closely
related to the Nicobar pigeon and the dodo and Rodrigues
solitaire, both extinct birds from islands near Madagascar.
The spotted green pigeon shows signs of a semi-terrestrial
island lifestyle and the ability to fly. The closely related
Nicobar pigeon shows similar habits and has a preference for
travelling between small islands.
The scientists say this lifestyle, together with the
relationship of both pigeons to the dodo and Rodrigues
solitaire, supports an evolutionary theory that the ancestors of
these birds were “island hoppers,” moving between islands
around India and Southeast Asia. The birds that settled on
particular islands then evolved into the individual species.
The dodo’s ancestor managed to hop as far as the island of
Mauritius near Madagascar where it then lost the ability to
fly.
Dr. Tim Heupink, Griffith University Australia says: “This
study improves our ability to identify novel species from
historic remains, and also those that are not novel after all.
Ultimately this will help us to measure and understand the
extinction of local populations and entire species.”
Passage 1
For reasons that are not entirely clear, when animals make
their way to isolated islands, they tend to evolve relatively
quickly toward an outsized or pint-sized version of their
mainland counterpart.
Perhaps the most famous example of an island giant—and,
sadly, of species extinction—is the dodo, once found on the
Indian Ocean island of Mauritius. When the dodo’s ancestor
(thought to be a migratory pigeon) settled on this island with
abundant food, no competition from terrestrial mammals, and
no predators, it could survive without flying, and thus was
freed from the energetic and size constraints of flight. New
Zealand also had avian giants, now extinct, including the
flightless moa, an ostrich-like bird, and Haast’s eagle
(Harpagornis moored), which had a wingspan up to 3
meters. Though Haast’s eagle could fly—and presumably
used its wings to launch brutal attacks on the hapless moa—
its body mass (10–14 kilograms) pushed the limits for self-
propelled flight.
As extreme evolutionary examples, these island birds can
offer insights into the forces and events shaping evolutionary
change. In a new study, Michael Bunce et al. compared
ancient mitochondrial DNA extracted from Haast’s eagle
bones with DNA sequences of 16 living eagle species to
better characterize the evolutionary history of the extinct
giant raptor. Their results suggest the extinct raptor
underwent a rapid evolutionary transformation that belies its
kinship to some of the world’s smallest eagle species.
The authors characterized the rates of sequence evolution
within mitochondrial DNA to establish the evolutionary
relationships between the different eagle species. Their
analysis places Haast’s eagle in the same evolutionary lineage
as a group of small eagle species in the genus Hieraaetus.
Surprisingly, the genetic distance separating the giant eagle
and its more diminutive Hieraaetus cousins from their last
common ancestor is relatively small.
Passage 2
The mysterious spotted green pigeon (Caloenas maculata)
was a relative of the dodo, according to scientists who have
examined its genetic make-up. The authors say their results,
published in the open access journal BMC Evolutionary
Biology, support a theory that both birds are descended from
“island hopping” ancestors.
The scientists took DNA from two feathers of the spotted
green pigeon. Because of its age, the DNA was highly
fragmented, so they focused in on three DNA “mini
barcodes” – small sections of DNA which are unique for
most bird species. They looked at these sections of the
pigeon’s DNA, and compared it to other species.
This showed that the spotted green pigeon is indeed a
separate species, showing a unique DNA barcode compared
to other pigeons. The pigeon is genetically most closely
related to the Nicobar pigeon and the dodo and Rodrigues
solitaire, both extinct birds from islands near Madagascar.
The spotted green pigeon shows signs of a semi-terrestrial
island lifestyle and the ability to fly. The closely related
Nicobar pigeon shows similar habits and has a preference for
travelling between small islands.
The scientists say this lifestyle, together with the
relationship of both pigeons to the dodo and Rodrigues
solitaire, supports an evolutionary theory that the ancestors of
these birds were “island hoppers,” moving between islands
around India and Southeast Asia. The birds that settled on
particular islands then evolved into the individual species.
The dodo’s ancestor managed to hop as far as the island of
Mauritius near Madagascar where it then lost the ability to
fly.
Dr. Tim Heupink, Griffith University Australia says: “This
study improves our ability to identify novel species from
historic remains, and also those that are not novel after all.
Ultimately this will help us to measure and understand the
extinction of local populations and entire species.”