Associate Professor at the University of Nottingham (UK). My research focuses on niche limits and dynamics across scales, from individual organisms to the globe. Mostly lizards.
Anole masks. Note: The dewlaps looked a lot pinker under natural light!
Organisms that colonize a new landmass are often faced with strange environments and selection pressures. Biologists are no exception. Having quasi-recently emigrated to England, I can tell you that, from a North American perspective, the UK can be pretty strange. One of the novelties, along with saying ‘Ta’ and not heating buildings, is the ‘fancy dress’ party. If you’re American or Canadian, then ‘fancy dress’ probably conjures images of black tie, tails and sherry (Downton Abbey anyone?). But no. ‘Fancy Dress’ is when otherwise regular people don ridiculous costumes and drink a lot (wait, that does sound like Downton Abbey). The reasons behind this custom (the dressing up, not the drinking) are unknown to me. Maybe it’s because there’s no Halloween and thus no annual outlet for looking like an idiot?
Anyway, the point is that this year, our departmental party’s theme was Noah’s Ark. Of course, this left us with only one option. If the world’s going to flood, then we’d better be sure there’s a pair of anoles on board. After all, think of the opportunity for radiation when the waters recede. All it took was a little duct tape, papier-mâché, paint, an artistic spouse and voila, Anolis masks! Of course, I can’t believe that I’m the only one who has ever attempted an anole costume – anyone else have any pics to share of their efforts?
Proportion of population genetic divergence accounted for by isolation-by-environment and isolation-by-distance in 17 Anolis species (from Wang et al.)
Identifying the factors contributing to population genetic divergence is important for understanding how many evolutionary processes play out in geographical space. Plus, it’s just plain interesting. In a new paper in Ecology Letters, Ian Wang, with Anole Annals stalwarts Rich Glor and Jonathan Losos, tested the roles of environment and distance in determining spatial patterns of population genetic divergence of 17 anole species on the Greater Antilles. To give the game away (spoiler alert!), the short answer is that both play a role, with some interesting variations among islands and species. However, it’s not just Wang et al.’s results that are interesting (more on those later), but also how they went about getting them.
Wang et al. tested two (not mutually exclusive) hypotheses for population genetic divergence. The first was isolation-by-distance (IBD), where distance and dispersal barriers prevent gene flow among populations. The second was isolation-by-environment (IBE), where there is either selection against dispersers, or a preference to remain in the environment where individuals are locally adapted. To test these hypotheses for each species, the authors first quantified environmental dissimilarity among populations using the Worldclim dataset, MODIS vegetation data, and elevation. Next they measured geographic distances among populations, but with a twist. To incorporate the idea that certain environments will be easier to disperse through than others, Wang et al. constructed environmental niche models. They then used the resulting (reverse) suitability values as a proxy for the ‘resistance’ of an area to movement and calculated the weighted distance between populations using two methods: least-cost pathway and all-possible-paths (circuit distance).
Armed with these measures of environmental dissimilarity and geographic distance, Wang et al. used structural equation modeling to determine the contribution of IBE and IBD to genetic divergence (they redid the analysis a few other ways, to ensure their results were robust. Short answer: they were). They found that both IBE and IBD had a role, but that distance was of greater importance, with collinearity being much less of an issue than I, at least, initially guessed. Their results were relatively consistent across species and islands, though a few species, mostly Hispaniolan, were exceptions (you’ll have to read the paper to find out which ones). Regardless of whether you’re more interested in the general pattern across species (and islands), or in the exceptions, Wang et al.’s study will undoubtedly generate more research questions and spur future work.
Lastly, one of the paper’s aspects I liked best was how the authors used environmental niche models. Species distribution/environmental niche/ecological niche/spawns-of-hell models get a lot of flak from a lot of sources. Much of this is even deserved – however, this is often more the fault of the modeller than the model. As Wang et al. have shown, such models can still provide useful and interesting insights into ecological and evolutionary process. In fact, anole biologists are leaders in new and informative ways to exploit such models. Wang et al.’s paper certainly continues this (emerging) tradition.
Wang, IJ, Glor, RE & Losos, JB. 2012. Quantifying the roles of ecology and geography in spatial genetic divergence. Ecology Letters. doi: 10.1111/ele.12025
We all know that geckos want to be anoles. But I fear I have unearthed a plot by an unidentified group of gecko-groupies to elevate the lowly gecko in the eyes of the public by forcing innocent anoles to masquerade themselves as (gasp) Madagascan day geckos. It all began several weeks ago, under the guise of a day trip to London to take in a little-known sporting event involving heroic UK demi-gods and demi-goddesses versus some other people (or so the BBC told me). Late in the day, we found ourselves wandering one of our favourite London haunts – the Natural History Museum. The mission: a gift for our soon-to-be-born niece (and where else would you go to find a gift for a newborn other than a natural history museum gift shop?). In the book section, I found a potentially better option: My First Book of Reptiles and Amphibians. It looked perfect – what baby wouldn’t love to be lulled to sleep by a full page close-up of a mouse disappearing down a viper’s throat or tidbits of information like “An adder’s bite is rarely fatal. It can cause mild swelling, and is very painful, but it is unlikely to kill you.” Imagine what herpetological feats said child would achieve later in life!
Kidd Cay, one of the islands included in the Calsbeek and Cox (2010) study (photo from Losos and Pringle, 2011).
Chances are that if you read this blog, then you also tend to note when Nature publishes something anoley. Thus, you’re probably already aware that last week Losos and Pringle published a reply to a paper by Calsbeek and Cox that appeared in Nature last year. In that paper, C&C concluded that competition is a more important agent of selection than predation for island anoles. In their reply, L&P point out limitations in the original study’s major assumptions, experimental design, and statistical analyses. Rather than go into all the gory details, I suggest you look at their reply directly. Just don’t let your non-anolologist colleagues or family members get a look at their Fig. 1a or you’ll lose any credibility you might have once garnered by speaking about the rigours of field work. As is usual, C&C have also published a reply to the reply where they respond to the criticisms, re-performing some analyses. Again, I don’t want to focus on the details; I’d rather let each reader decide for themselves.
Personally, I enjoy reading replies and replies to replies and if it gets to a reply to a reply to a reply, well even better! It’s the way science should work – someone publishes something, there is debate, and the scientific community self-corrects if necessary. However, recently an article in Ecosphereentitled “Do rebuttals affect future science?” by Banobi et al. challenged this view.
