8/19/2013 Topic 11: Convergence What is convergence? What is convergence? How can convergence be detected? Emerald Tree Boas and Green Tree Do we see convergence? Pythons What are the classic herp examples? show a remarkable Have they been formally studied? level of convergence Photos © KP Bergmann, Philadelphia Zoo (adult ETB) What is convergence? What is convergence? Several patterns are ________________ conflated into convergence: Phylogenetic term _____________ Previously defined as _____________ the similarity of a _____________ character between taxa due to convergence “True” _______________ However, it includes: All mean slightly different True convergence things Reversal Parallelism Being clear on definitions is important These have similar effects on phylogeny reconstruction Snake-like Adults with gill slits Photos © KP Bergmann, Philadelphia Zoo Pough et al. 2004, Fig 3-1 What is convergence? What is convergence? _____________ Lerista ________________ (Scincidae) When evolution switches _______________ Independent evolution A recently evolved of similar traits in character is lost related lineages whose common ancestor did A recently lost character not share that trait is re-evolved (Futuyma 1986) Parallelism generally Example: involves a homologous Bachia digit loss and re- ____________________ evolution Generally closely related Derived species tend to lineages (not always) have _______________ 5 digits is ancestral Digit loss This has not been tested in Lerista , but is likely Digit gain Kohlsdorf & Wagner 2006; Photo © E Alzate Greer 1990 1 8/19/2013 What is convergence? What is convergence? __________________ How is convergence viewed? A B C D E F G H Phylogeny Independent evolution _______________ of similar traits in _______________ independent lineages, Confounds ability to often by ___________ accurately reconstruct ______________ C phylogeny A mistake in coding? B E Difference from D F Biology in general parallelism can be G C blurred ____________________ A ____________________ B E H D F Adaptation by different G “when two taxa evolve Root taxa to similar situations to be more similar to A one another than their A phylogenetic perspective H ancestors were to each is important to studying it other” (Stayton 2008) Stayton 2008 Stayton 2008 How can convergence be detected? How can convergence be detected? Pattern 2: Two ________ What kinds of patterns ____________________ does convergence result ____________________ in? The two taxa may be quite different in some Pattern 1: Two different ways, similar in others taxa converging ________ Trait 2 Trait 2 Trait _____________ What we typically think of as convergence Trait 1 Trait 1 Stayton, 2006; Photos © KP Bergmann, Philadelphia Zoo Stayton, 2006; Photo www.digimorph.org How can convergence be detected? Do we see convergence? Pattern 3: Two different What pattern of convergence are each of these taxa evolving _________ examples? Why? ____________________ Parallel evolution, but NOT necessarily parallelism The ____________ 2 Trait ______________ are convergent, even if the phenotype is not Trait 1 More typical of very unrelated taxa (?) Pufferfishes and Tail as a fat Suite of morphological horned lizards? storage organ & behavioral traits Stayton, 2006; Photos ??, PJB Photos © PJB, KP Bergmann, Philadelphia Zoo 2 8/19/2013 Do we see Do we see convergence? convergence? What are the herp examples? Fossoriality Fusion of skull Snake-like body form (BE & LR) in _________________ squamates Small relative head size Limited cranial kinesis Has evolved __________ Feed on smaller prey independently than non-fossorial Has occurred in two ways, but relatives within each, we still have convergence __________________ __________________ Examples: What pattern of convergence? Gymnophiona Amphisbaenia Scolecophidia What pattern is this? Brandley et al. 2008; Bergmann 2013 www.digimorph.org Do we see convergence? Do we see convergence? Clinging ability increases with ____________ & ___________ Adhesive pads on digits Skinks are poor clingers for their body mass – pads are Gekkonidae smaller, less effective Evolved 3 times in squamates Scales modified to have fine keratinous hairs called ____________ Anolis Same mechanism of action (________________ forces) Also seen in some inverts, like tarantulas Prasinohaema What pattern is this? Photos: KP Bergmann, USDA, Afco Zoo Supplies; SEMs: Williams and Peterson, 1982. Photos: KP Bergmann, USDA, Afco Zoo Supplies; Graph: Irschick et al. 1996 Do we see convergence? Do we see convergence? Iguanidae and “Agamidae” Iguanidae and “Agamidae” More examples ____________________ What pattern do we see here? New & Old World, respectively Ecological analogs look very similar Many instances of convergence Adaptation to _____________ Perhaps a lizard’s shape can be modified in only certain ways e.g. a laterally flattened tail may be the easiest way for a lizard to adapt to swimming Photos © K Bergmann, K Derby Photos: PJB, K Bergmann, Pough et al., E Rudolph 3 8/19/2013 Do we see convergence? Do we see convergence? Iguanidae vs. “Agamidae” Phrynosoma vs. Moloch Most of these examples Similar morphology are relatively slight Both eat ants examples of convergence _________________ _________________ Phrynosoma & Moloch _________________ horridus is more complex _________________ _________________ Different from generalist lizards _________________ No body lunge Slow-moving Faster tongue ____________________ protrusion Have micro-grooves that Faster feeding cycle allow them to gather Don’t process prey water in dry deserts Photos: © PJB, J Meyers Meyers and Herrel 2005 Do we see convergence? Do we see convergence? Reduction in shell defenses in insular giant tortoises Herbivory in lizards Independent evolution of a saddle-backed shell in the Comparison of skull shape Mascarine islands Comparing ___________ Similar patterns on Galapagos, Aldabra to non-herbivore sister group Herbivores tend to “move” towards a common area of morphospace, relative to sister groups Herbivores tend to evolve skulls with higher mechanical advantage __________________ __________________ What pattern is this? Austin and Arnold 2001 Stayton 2006 Do we see convergence? Do we see convergence? Convergence in Unrelated rock-dwelling lizards have a saxicolous lizards flat body and long limbs In general, saxicolous Live on vertical rock surfaces taxa have evolved: ________________ Seen in: ________________ Petrosaurus (Phrynosomatinae) Platysaurus (Cordylidae) Petrosaurus has evolved Pseudocordylus (Cordylidae) a shallower head, but Anolis bartschi ( Polychrotinae) not longer limbs Some tropidurines PC-2: Head depth PC-2: Has this body shape evolved along the branch on the phylogeny that also led to saxicoly? PC-1: Limb length Photos © Branch, Kober Revell et al. 2007 4 8/19/2013 Do we see Convergence? Do we see Convergence? _______________________ Anolis ecomorphs mtDNA sequence phylogeny Morphometric data, distance clustering Ecomorphs evolved multiple times on different Greater Antillean islands Each ecomorph clusters separately from others in morphospace Does this represent convergence? Need to look at the morphology Convergence is going on, but what pattern? From Losos et al., 1998 From Losos et al., 1998 Do we see Convergence? Anolis ecomorphs ___________________ plays a role Same ecomorphs, but different sequence of evolution _________________ do not fall into ecomorphs Irschick et al. 1997; Losos et al., 1998 5.