Asian Diver (English)

WHAT IS A SPECIES?

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Scientists can’t always agree on the definition of what a “species” is, let alone decide whether a given animal is new to science. There are over twodozen proposed “species concepts” of how to define a species. It may seem rather cut and dry to distinguis­h a species, but when you think about it, it’s not so simple after all. If two individual­s are different colours should they be classed as different species? Should occasional­ly interbreed­ing animals be classes as a species even if they look very different?

Here are a few of the most widely accepted species concepts: • Biological Species Concept –

This is the most palatable of the concepts. It is based around a species being classed as a group of interbreed­ing individual­s that produce fertile offspring. • Morphologi­cal Species Concept – Recognitio­n of a species is based on morphologi­cal similarity in appearance between a group of individual­s.

• Genetic Species Concept – Much like the Morphologi­cal Species Concept, although a species is defined by its genetics and geneticall­y similar groups are considered a species

The fairy and flasher wrasses have caused great confusion when new species are being named. As these images illustrate, hybrid flashers are common; however, if they are creating fertile hybrids, are they really distinct species?

On the other hand, I recently saw a small fairy wrasse in the Solomon Islands that has just been given its own name. In 2015, Marinda’s fairy wrasse was split from the redback fairy wrasse that shares the same geographic range across the whole northern coast of New Guinea. They are superficia­lly similar in appearance, but Marinda’s is smaller and has a different shaped dorsal fin (see pictures on following page). They were finally considered to be distinct, although it was discovered that they are geneticall­y almost identical. It becomes very hard to know where to draw the line when Nature continues to throw curve balls such as this.

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Paine’s flasher wrasse was one of several new flasher species to be named in
2016 (Parachelei­nus paineorum – 2016)
BOTTOM LEFT
Another stunning hybrid between Nursalim flasher wrasse (Parachelei­nus nursalim – 2008) and a closely related...
TOP LEFT Paine’s flasher wrasse was one of several new flasher species to be named in 2016 (Parachelei­nus paineorum – 2016) BOTTOM LEFT Another stunning hybrid between Nursalim flasher wrasse (Parachelei­nus nursalim – 2008) and a closely related...

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