Invertebrates in the news #4 - Speciation in reef hermit crabs

The journal Science has a section entitled "Editor's choice" where they feature recent papers that caught their attention. This week, they chose to highlight a paper written by Machel and Gustav that looks at the patterns of speciation in the genus of hermit crab Calcinus.

Calcinus lineapropodus (photo by Gustav Paulay)

By combining information about the genealogical relationships of 56 species (almost all the species known in this genus as well as 9 undescribed species) and information about the color of the species and where they live, they were able to discover some interesting facts about the evolution of this group.

• Closely related species have similar shapes but they can have very different color patterns. This means that color patterns evolve rapidly and that they can be used to tease species apart. This also suggests that the hermit crabs themselves use these color patterns to recognize the members of their own species. So, the apparition of new color patterns could lead to new species. To illustrate this rapid evolution in color patterns, compare these closely related species that live most of the time on branching corals: Calcinus minutus (from Guam), Calcinus rosaceus (from Oman) and Calcinus nitidus (from Moorea).

Calcinus minutus from Guam (photo by Gustav Paulay), Calcinus rosaceus (photo by Machel Malay), Calcinus nitidus (photo by Gustav Paulay)

• Isolated islands and archipelagos such as Hawaii have several endemic species of Calcinus, which suggests that the formation of new species (speciation) happened on the edges of their geographical ranges.

• Most species of Calcinus are found in oceanic areas in particular in the Western Pacific and in Polynesia. This is different from what is known for other marine invertebrates. Indeed, in corals, fishes, and various groups of mollusks, most of the diversity is found in a more continental area called the "coral triangle" (from northern Australia to Indonesia and Papua New Guinea). To illustrate this difference, compare the 2 maps below. The first one shows the distribution of the diversity for the hermit crabs of the genus Calcinus whereas the map on the bottom is the same kind of map for the cowries. The unusual diversity pattern found in Calcinus highlights the importance of the ecological and historical processes characterizing each group of organism that have led to their current geographical distribution.

Distribution of the species richness of the genus Calcinus. Contours represent 4, 10, 13 and 17 species. (from Malay & Paulay 2010)

Distribution of the species richness of cowries. Orange to red colors represent high number of species (above 64), green to yellow colors represent intermediate number of species (between 40 to 64), light blue to dark blue represent low number of species (between 1 and 40). (from Paulay & Meyer 2006)

Links:

• Editor's choice. Science. 327 (26 March 2010): http://www.sciencemag.org/content/vol327/issue5973/twil.dtl#327/5973/1555-c
• Malay MC, Paulay G. 2010. Peripatric Speciation Drives Diversification and Distributional Pattern of Reef Hermit Crabs (Decapoda: Diogenidae: Calcinus). Evolution. 64-3:634-662. DOI: 10.1111/j.1558-5646.2009.00848.x
• Paulay G, Meyer C. Dispersal and divergence across the greatest ocean region : Do larvae matter ? Integrative and Comparative Biology. 2006;46(3):269-281. DOI: 10.1093/icb/icj027

AAUS Training

In order to dive under the auspices of the University of Florida, divers must undergo training to become AAUS certified Scientific Divers. Art, François, and Nat all needed this training for their future field endeavors. In order to keep your status current you must complete 12 dives a year. Jenna and I had fallen short (way short) so we needed to re-checkout with Cheryl, the Dive Safety Officer (DSO) of UF, so we tagged along on some of their dives one day.

Here are the three trainees (Nartçois) preparing to descend to 100 feet. We were diving in a spring that day and the water was quite cold, so they're all rocking a hood.

Although AAUS certification is not a NAUI-card-having designation of diver, there are several aspects of the training, one of which is to become a Rescue Diver. Below, Jenna plays the role of a tired diver and François gives her a hand with a fin push.

Although it it seems pretty clear from this next picture that François is attempting to drown Nat, he is actually practicing getting them both out of dive gear while towing him to the exit and administering rescue breathing.

Below is a short video of Nat performing the same exercise on Art, either saving his life or drowning him. You be the judge.

Also key to scientific diver training are navigational skills. Here Art and Nat prepare to navigate an underwater square at a depth of 30-40 feet using a compass for direction and a pre-determined number of fin-kicks as the distance.

You know what dive training means...more fieldwork! And hopefully some more blog posts from the field, replete with showy animal photos and calendar-worthy scenery.

:) Mandy

...but we've been really busy

I know it's been way too long since my last update, but just wait till you see all that we've had going on and I hope all will be forgiven.

The Shrimp Mafia has disbanded with Ivan and Sammy returning to their respective countries of origin leaving Art to describe new species on his own. But not to worry, Magali Honey (Maggie) is visiting and will be here for a few weeks. She came just in time, I think that by this point the hotel we use has started factoring our visitors into their monthly budget. Here are Machel and Maggie bonding over talk of barnacles and sea cucumbers.

Also during the month of February, prospective grad students came to visit the department. One of the women who came to interview with our (Gustav's) lab is Christine Ewers. I didn't capture her on film this time (I was sick, another reason for the lack of posts, do you forgive me yet?) but she has been on a R/V Bellows field trip with us in the past. Here are she and Julie patching up a trawl net.

Another new arrival who is here to stay (at least for a few years) is Hsiu-Chin Lin. The newest member of the team, she is joining us a post-doc. She has a lot of genetic expertise that we are anxious to add to our collective knowledge.


In addition to all the arrivals and departures. We also participated in the 2010 UF Marine Biology Symposium. Many of us presented talks or posters of our various and sundry research interests. My data were a mess and needed a lot of time and attention to polish up enough in time to present at the symposium. Other things that I might have been meaning to do (i.e. posting to this blog) may or may not have fallen to the wayside as a consequence, but I'm sure you understand. At the conference, the cuke team swept the undergraduate awards with Julie, Laura, and J.D. all winning prizes. Here is a glimpse of Julie's first place presentation with some nice ossicle pictures. Try and soak in the knowledge.

So in addition the the grant-ending other-work-neglecting catch-up to do, we now have our symposium-readiness other-work-neglecting catch-up to do. Sarah has been doing a lot of cataloging and label matching. Here she is shelving a freshly labeled box of something. This is the shelving where we keep the wet (ethanol preserved) collection. It's not as creepy as the lighting makes it look. You should see the herpetology collection!

Jenna has also been tackling some label matching, but it seems like there's always someone wanting a Geneious tutorial. We've been getting back so much sequence data from the Smithsonian that everyone wants to get to work on building some trees for their study group. One of the latest petitioners is Sea.

Fred has also begun work on his Thailand collection and has spent some time in the range this week sorting through trays of land snails that's he's collected to prepare them for cataloging.

Also doing land snail work, Chelsey and John have been working on the many, many (many, many) lots from Madagascar. Chelsey may be employed full time over in the shark range, but she keeps coming back home to Invert Zoo, feeling the pull of the Acavidae and their messy taxonomy, and possibly the snack drawer and its ever-changing bounty.

I'm also pleased to report that I've made serious inroads into the desk blockade that has been constructed around me. I would say that things are returning to normal, but I realize that I really have no standard for comparison. What can I say, we're a happenin' joint.

:) Mandy