WHAT IS A SPECIES?

Asian Diver (English) - - Man & Sea -

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.

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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