Discriminating butterflies show how one species could split into two

Walk through the rainforests of Ecuador and you might encounter a beautiful butterfly called Heliconius cydno. It’s extremely varied in its colours. Even among one subspecies, H.cydno alithea, you can find individuals with white wingbands and those with yellow. Despite their different hues, they are still the same species… but probably not for much longer.

Even though the two forms are genetically similar and live in the same area, Nicola Chamberlain from Harvard University has found that one of them – the yellow version – has developed a preference for mating with butterflies of its own colour. This fussiness has set up an invisible barrier within the butterfly population, where traits that would typically separate sister species – colour and mate preferences – have started to segregate. In time, this is the sort of change that could split the single species into two.  

Heliconius butterflies defend themselves with foul chemicals and advertise their distasteful arsenal with bright warning colours on their wings. The group has a penchant for diversity, and even closely related species sport different patterns. But the butterflies are also rampant mimics. Distantly related species have evolved uncanny resemblances so that their warnings complement one another – a predator that learns to avoid one species will avoid all the ones that share the same patterns.  It’s a mutual protection racket, sealed with colour.

The result of this widespread mimicry is that populations of the same species can look very different because they are imitating different models. This is the case with H.cydno – the yellow form mimics the related H.eleuchia, while the white form mimics yet another species, H.sapho.

How can we be sure that the pairs of butterflies that look alike aren’t in fact more closely related? For a start, scientists have shown that the frequencies of the yellow and white versions of alithea in the wild match those of the species they mimic. Genetic testing provides the clincher. It confirms that the two mimics are indeed more closely related to each other than they are to their models.

Genetics also tells us how alithea achieves its dual coats. Colour is determined by a single gene; if a butterfly inherits the dominant version, it’s white and if it gets two copies of the recessive one, it’s yellow. Pattern is controlled in a similar way by a second gene. These variations aside, there are no distinct genetic differences between the two alithea forms. They are still very much a single population of interbreeding butterflies.

But that may change, and fussy males could be the catalyst. Chamberlain watched over 1,600 courtship rituals performed by 115 captured males. Her voyeuristic experiments showed that yellow males strongly preferred to mate with yellow females, although white males weren’t so fussy.

This isn’t just a whimsical preference – Chamberlain thinks that the colour gene sits very closely to a gene for mate preference. The two genes may even be one and the same. Either way, their proximity on the butterfly’s genome means that their fates are intertwined and they tend to be inherited as a unit. That’s certainly plausible, for the same pigments that colour the butterflies’ wings also serve to filter light arriving into their eyes. A change in the way those pigments are produced could alter both the butterfly’s appearance and how it sees others of its kind.  

To see what happens when this process goes further, you don’t have to travel far. Costa Rica is home to another H.cydno subspecies called galanthus, and a closely related species called H.pachinus. They represent a further step down the road that alithea is headed down. Galanthus and H.pachinus look very different because they mimic different models – the former has white wingbands reminiscent of H.sapho, while the latter has green bands inspired by H.hewitsoni.

Nonetheless, the two species could interbreed if they ever got the chance. Two things stand in the way. The first is geography – H.cydno galanthus stays on the eastern side of the country, while H.pachinus remains on the west. The second is, as with alithea, sex appeal. Males prefer females bearing the same wing colours as they do so even if the two sexes of the two species were to cross paths, they’d probably fly right past each other.

Genetically, these species have also diverged far further than the two forms of alithea have. They differ at no less than five genes involved in colour and pattern, two of which are practically identical to the ones that causing alithea to segregate. They also provide more evidence that the genes for colour and mate preference are closely linked, for crossbreeding the two species yields offspring with half-way colours and half-way preferences.

These butterflies are by no means the only examples of speciation in the wild. In this blog alone, I’ve discussed a beautiful case study of diversity creating itself among fruit flies and parasitic wasps, explosive bursts of diversity in cichlid fish fuelled by violent males, and a giant predatory bug that’s splitting cavefish into isolated populations.

But Heliconius butterflies may be the most illuminating of all these case studies. They’re easy to capture, breed and work with. And as Chamberlain’s study shows, they can marshal together the contribution of experts in genetics, ecology, evolution and animal behaviour in an effort to understand that most magnificent of topics – the origin of species.

[This post was written as an entry for the NESCENT evolution blogging contest. For more details about this competition, visit their website.]

Reference: Science 10.1126/science.1179141

More on speciation:

• How diversity creates itself – cascades of new species among flies and parasitic wasps
• Giant insect splits cavefish into distinct populations
• Malawi cichlids – how aggressive males create diversity

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Native language shapes the melody of a newborn baby’s cry

Telling the difference between a German and French speaker isn’t difficult. But you may be more surprised to know that you could have a good stab at distinguishing between German and French babies based on their cries. The bawls of French newborns tend to have a rising melody, with higher frequencies becoming more prominent as the cry progresses. German newborns tend to cry with a falling melody.

These differences are apparent just three days out of the womb. This suggests that they pick up elements of their parents’ language before they’re even born, and certainly before they start to babble themselves.

Birgit Mampe from the University of Wurzburg analysed the cries of 30 French newborns and 30 German ones, all born to monolingual families. She found that the average German cry reaches its maximum pitch and intensity at around 0.45 seconds, while French cries do so later, at around 0.6 seconds.

These differences match the melodic qualities of each respective language. Many French words and phrases have a rising pitch towards the end, capped only by a falling pitch at the very end. German more often shows the opposite trend – a falling pitch towards the end of a word or phrase.

These differences in “melody contours” become apparent as soon as infants start making sounds of their own. While Mampe can’t rule out the possibility that the infants learned about the sounds of their native tongue the few days following their birth, she thinks it’s more likely that they start tuning into the own language in the womb.

In some ways, this isn’t surprising. Features like melody, rhythm and intensity (collectively known as prosody) travel well across the wall of the stomach and they reach the womb with minimum disruption. We know that infants are very sensitive to prosodic features well before they start speaking themselves, which helps them learn their own mother tongue.

But this learning process starts as early as the third trimester. We know this because newborns prefer the sound of their mother’s voice compared to those of strangers. And when their mums speak to them in the saccharine “motherese”, they can suss out the emotional content of those words through analysing their melody.

Mampe’s data show that not only can infants sense the qualities of their native tongue, they can also imitate them in their first days of life. Previously, studies have found that babies can imitate the vowel sounds of adults only after 12 weeks of life, but clearly other features like pitch can be imitated much earlier. They’re helped by the fact that crying only requires them to coordinate their breathing and vocal cord movements, while making speech sounds requires far more complex feats of muscular gymnastics that are only possible after a few months. 

Reference: Current Biology doi:10.1016/j.cub.2009.09.064

More on child development: 

• Infants match human words to human faces and monkey calls to monkey faces (but not quacks to duck faces)
• Bilingual children learn language rules more efficiently than monolinguals
• Babies can tell apart different languages with visual cues alone
• Bilingual infants have better mental control
• Five-month-old babies prefer their own languages and shun foreign accents

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2009 Holiday Gift Guide: Roku HD-XR Player

We are kicking off our 2009 Holiday Gift Guide with the Roku HD-XR player. Why? Well, we think that it’s the perfect time to introduce someone to the new hotness that is TV, delivered over the web, and right into the living room. Sure, Netflix has come to the Xbox 360, but if you want streaming access to the Netflix service and don’t own a game console, this is your cheapest barrier to entry. The HD-XR model also gives you access to the Amazon Unbox catalogue, as well as the entire MLB game service as well, if you are subscribed.

Definitely a great gift for movie buffs, the Roku HD-XR player is able to stream over 12,000 movies and television shows from the Netflix Watch Instantly catalogue, and over 45,000 from Amazon Video on Demand. It connects to your home network through an ethernet port, or over Wi-Fi, connecting at up to 802.11n if you have it. There’s also a USB port on back, which Roku says is for future use. Our guess is that they’ll be allowing the device to read from an external USB drive, which would be stellar.

The actual device is tiny, so it takes up barely any space, and setup takes just a couple of minutes – very simple. Of course, a Netflix subscription is required, but once you have that, everything else is a piece of cake.

Honorable Mention: If you want all the features of the Roku HD-XR, but don’t need the USB port or 802.11n wireless speeds, you can grab the Roku HD Player for $99!

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Verizon Finally Announces DROID Eris, $99 Available Nov 6th

Verizon has officially made the DROID Eris, Verizon’s version of the HTC Hero, well, official. Like previous reports, the DROID Eris will release on November 6th for the low, low price of $99 (after rebate, with 2 year contract). We’re unsure of why Verizon decided to wait until the day before to announce this puppy but the pricing is absolutely on point. It feels like Verizon is the only carrier who "gets" it when it comes to pricing.

The DROID Eris Specs are pretty much exactly like the Sprint HTC Hero–5MP camera, 528MHz Qualcomm processor, 3.2-inch multitouch screen, and Android 1.5–but the battery is now only 1300mAh compared to 1500 mAh on the Sprint HTC Hero. The four Android harware buttons are replaced by touch-sensitive buttons similar to the DROID.

The DROID Eris offers a great alternative to the DROID and a completely different experience. And make no mistake, this isn’t some budget phone, this is still the same phone we deemed the best Android phone on the market only a month ago.

Who’s buying a DROID Eris?

[vzw]

NYC Verizon Store Opening At Midnight For DROID, Will Others ?

If you’re in or around the New York City area on Droid Day, you’ll have the opportunity to be among the first group to own the Verizon Motorola DROID. We’ve just received a tip that tells us that the Verizon Wireless store on 34th Street is planning to open on November 6th at 12:00 AM for a Midnight Launch of the DROID. We’re hoping that this is a start of a trend and that many other Verizon stores will follow suit with midnight launches because we know you guys would get restless knowing others are already enjoying their DROID.

Are other stores getting Midnight Launches of the DROID? Who’s going to be the first to buy one?

a BIG thanks to VZDroidGuy for the tip!

Android in Canada: LG GW620 Eve to Rogers, DROID to Telus ?

Our neighbors to the north, Canada, should be happy to know that their Android offerings are about to be expanded. As expected, the LG GW620, LG’s first Android device, will launch on Rogers for $49.99 with new 3-year contract. We’ve seen the LG Eve before and were intrigued by its social networking capabilities. Since it is on Rogers, if you somehow manage to unlock it, it’ll work on AT&T 3G bands. And since AT&T has yet to officially acknowledge Android, we’re sure some of you might just go do that.

In other news, there’s a rumor floating around that points to Telus being the carrier that’ll get the Motorola DROID. We’re working on getting more details, but if this is true, it’ll be huge. From what little we know about Canadian carriers, Telus is in the middle of a switch from CDMA networks to GSM networks, however, many of their new devices (iPhone 3GS, GSM HTC Hero, etc) use GSM and we’re hoping that they’ll get the GSM DROID. Why? Because if Telus does get the GSM version, those DROIDs will also work with AT&T 3G bands. So even with AT&T not acknowledging Android, there’s potential for unlocked DROIDs on AT&T. We’re still waiting for official word from Telus to give this rumor more legitimacy but in the mean time, this might be the closest you’ll ever get to an AT&T DROID.

So what do you guys think? Do Canada Android users and AT&T users both win?

[via engadget, themobileninjas]

thanks rileyfreeman & milfette for the tip!

Droid Eris Gets Unboxed, Better than Sprint HTC Hero ?

The DROID Eris, Verizon’s version of the HTC Hero, has been unboxed and looks generally ready to go for the November 6th launch. Why Verizon doesn’t want to officially announce this device is beyond us, because from the looks of it, they’ve got themselves a winner here. 

BGR’s tipster says that the DROID Eris is both thinner and lighter than the Sprint HTC Hero and pretty much the best Android device other than the DROID. So when will someone knock off Verizon from its perch of having the two best Android phones on the market?

Hit the jump to see more pictures of the DROID Eris!

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