A new species has developed on the Galapagos Islands, and scientists have been lucky enough to observe its development over the past 36 years. On the Daphne Major, an Island in the Galapagos Archipelago, three known species of Darwin Finches reside. During his travels around the Galapagos, Darwin discovered several species of Finch and it was these that helped him develop his theory of evolution through natural selection and were thus known as Darwin’s Finches. It seems somewhat fitting then that it is these birds which are giving scientists a first-hand insight into a process which as never before been observed in the wild.
It began in 1981 when a non-native Finch species known as the Large Cactus Finch appeared on the Island and proceeded to mate with a Medium Ground Finch, a species native to the Galapagos. The Large Cactus Finch is believed to have flown roughly 65 miles from its native territory of the Island Espanola, and produced a set of fertile young and the beginning of a whole new genetic line.
Generally it would be expected that when two birds of a different species mate and produce fertile young, any traits or differences that union produced would be bred out when that fertile young goes on to reproduce with another species in the area. Indeed researchers believed that when this young bred with one of the other three species of Finch on the Island, the traits which defined this new species would be absorbed and disappear. However, this was not the case with this species. From just the second generation this species became what is known as a closed species group, essentially only mating with others of its own species. This has had to rely on inbreeding on the part of this new species to reproduce and survive, but this has not seemed to have led to any adverse effects or deficiency in the species. One element which researchers believe has contributed to the success of this breed is bill morphology; the size and depth of their beaks being bigger than the other native species on the Island means they can efficiently live off of the large, woody fruits of the Island, especially during the dry months, droughts or when food is generally in limited supply.
As a new species, they have developed their own ‘song’; as birds generally rely on bill morphology as well as the song of the bird to distinguish whether it is a bird of their species and therefore whether to mate with it or not, the change in bill as well as this different song means that other species of Finch on the Island are unlikely to reproduce with this new species, recognising that it is not one of their own.
Not only is the development of a new species something to be celebrated, but its evolution is also a topic of interest; evolution, a process which we commonly think to take hundreds of years, has now been carried out in just two generations worth. This new species arose through a process known as hybrid specification, specifically homoploid hybrid specification. Most common in plants, it means an infertile hybrid becomes fertile due to a doubling in the chromosomes. However, homoploid hybridisation occurs when the offspring are fertile but without this doubling of chromosomes and it is this homoploid hybridisation which occurs most often in animals, as is the case with this new species of Finch. However, this homoploid hybridisation itself is very rare in animals with very few known cases.
Whilst no official name has been given to this new species, researchers have nicknamed it Big Bird. This hybridization process, being the first time it has been observed in the wild, has not only brought us a new species of Finch but raises many interesting questions in regards to evolution and hybridisation in wild animals.
This research report can be found in the journal ‘Science’ here.
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