Topic 11: Convergence What Is Convergence? What Is Convergence

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

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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

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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

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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

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

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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