Phylogenetics - IB 200B 8 Feb 2011

Heterochrony &

All members of a monophyletic taxon share a common ancestor whose developmental pathway was modified to produce descendant morphologies.

Haeckel, E. 1899 - originally a physician became professor of comparative anatomy, later professor of , a chair established for him at Jena. Haeckel was deeply influenced by Darwin's "Origin…", and became "the apostle of Darwinism in Germany." Also coined term "Ecology." "I established the opposite view, that this history of the () must be completed by a second, equally valuable, and closely connected branch of thought - the history of race (phylogeny). Both of these branches of evolutionary science are, in my opinion, in the closest causal connection; this arises from the reciprocal action of the laws of heredity and adaptation... 'ontogenesis is a brief and rapid recapitulation of phylogenesis, determined by the physiological functions of heredity (generation) and adaptation (maintenance).”

Rejection of recapitulationist ideas in the early part of this century, however, the study of links between development and was relatively neglected until Ontogeny and Phylogeny was published by Gould in 1977. Gould presented his own ideas on (evolutionary changes in the timing of development), presenting a unified view of , recapitulation, paedogenesis, retardation, progenesis, etc. Basic idea is that all heterochrony is a result of acceleration or retardation of different developmental processes (growth, sexual maturation, morphological changes, etc.).

Heterochrony involves three kinds of evolutionary changes in the timing of development: changes in rate, changes in onset time, and changes in offset time. Each change can either be an increase or a decrease, thus six kinds of pure heterochrony can be defined: neoteny (slower rate), acceleration (faster rate), post- displacement (late onset), pre-displacement (early onset), progenesis (early offset) and hypermorphosis (late offset). Paedomorphosis (underdevelopment in descendant adults) is caused by the first of each preceding pair. Peramorphosis is the opposite pattern with opposite processes. (McKinney & McNamara, 1991).

Phylogenetics - IB 200B 8 Feb 2011

Gould (1977) Clock-models

Size and shape added to the determination of heterochrony by Gould (1977).

Phylogenetics - IB 200B 8 Feb 2011

Smith (2001)

Organisms are not “heterochronic.”

Dissociation of developmental pathways.

Phylogenetics - IB 200B 8 Feb 2011

Lindberg (1988)

Phylogenetics - IB 200B 8 Feb 2011

Ontogeny enters into our consideration of phylogenetics at three levels:

(1) Polarization of character state transformations (augmentation or primary).

(2) Assessment of homology.

(3) The recognition and exploration of heterochronic (and heterotopic) patterns in the ingroup.

Heterotopy - change in spatial patterning of ontogenetic processes (another Haeckel term).

Heterochrony is of interest because produces novelties constrained along ancestral ontogenies, giving rise to parallelisms between ontogeny and phylogeny. can produce new morphologies along trajectories different from those of the ancestors. As discussed above, heterochrony has an analytical formalism that virtually precludes the recognition of heterotopy (Zelditch & Fink 1996).

Hennig recognized both the problems and advantages of ontogeny and coined term semaphoront - an at a particular stage in ontogeny.

The quantification of these patterns usually involves constructing ontogenetic trajectories; vectors or curves that describe shape and size change through development. Although differences in these trajectories have been equated with developmental processes (ie. progenesis, neoteny, acceleration, hypermorphosis, etc., trajectories confound the mechanisms that create with the results of those processes (i.e., shape or size change at different times in ontogeny). Thus, heterochronic and heterotopic shifts cannot be considered processes or causal in producing novel morphologies, but rather the outcomes of changes in mechanisms that do. Although heterochrony and heterotopy do not necessarily produce novel morphologies, the construction of ontogenetic trajectories serves as a starting point for examination of generative mechanisms.

Lindberg & Guralnick (2003)

1a111 1a11 112 121 1 1a 1a 1a 1q 12 121 1 a 1a b 1q 122 112 1a 1a 122 1a 1q 12 11 111 1a 1a 1q 1q 21 1a 1a211 21 1q 221 1a 2 1a212 1q 1q 22 221 A-D 2q 2 1q 222 2 1a 1a 2q 2q 11 1a222 A 1a22 11 1 2a 2q 2q 12 2a1 12 2a 3q 2 2a 1Q 3q 2a21 3q 1 22 4a-c 2 2a 2a 4d 2 1 2Q 1A 3a AB 3a 2 4d 3a 1 3Q 4d ABCD 2A 4a CD 4Q B 3A 4A divisions cell number Phylogenetics - IB 200B 8 Feb 2011

2 9 11 12 Polyplacophora 5 6 6 6 1q 2q 3q 4Q

10 Patellogastropoda 2 = Character number 5 3q 5 = Cell division 1q = Cell lineage

Vetigastropoda

7 8 9 11 2 Neritopsina 4 5 6 6 5 2q 3q 1q

3 5 6 9 11 12 1314 2 Sorbeoconcha 6 5 6 6 6 6 6 7 5 1q 2q 3q 4Q 4d 1q

4 9 13 10 13 Architaenoglossa 6 5 6 5 6 1q 2q 4d 3q 4d 2 6 1 5 11 Opisthobranchia 5 6 1q 4 5 6 1q 3q 12 10 13 6 Valvatoidea 4Q 9 5 6 3q 4d

6 2q Pulmonata

Characters 7‐9 – this cell lineage produces prototroch and posttrochal ectoderm; the first stomatoblast contributes to the formation of the foot and shell gland (Dictus and Damen 1997). 7 – median number of cells present at formation of 2q cell lineage (4th division): 16=0 and 12=1. 8 – median number of cells present at formation of 2q1 cell lineage (5th division): 32=0, 24=1. 9 – median number of cells present at formation of 2q11 cell lineage (6th division): 60=0, 52=1, 44=2, 41=3, 37‐38=4 and 32=5.

Characters 10‐11 – this cell lineage produces ectomesoderm and posttrochal ectoderm (Dictus and Damen 1997). 10 – median number of cells present at formation of 3q cell lineage (5th division): 20=0, 23‐24=1, and 32=2. 11 – median number of cells present at formation of 3q1 cell lineage (6th division): 54=0, 60=1, 48=2, 40‐41=3, and 36=4. Phylogenetics - IB 200B 8 Feb 2011

Lindberg & Guralnick (MS) Scaphopoda

Patellogastropoda

Vetigastropoda

Neritopsina

Sorbeoconcha

Architaenoglossa

Valvatoidea

Opisthobranchia

Pulmonata

A 0.08 C 0.08 Veti Arch 0.06 Opist Sorb 0.06 Val

0.04 Veti 0.04

Pul Pat Scaph 0.02 0.02 HTU2 HTU3 Pul HTU6-7 0.00 0.00 HTU4-5 Nerit Opist Pat -0.02 Nerit -0.02 Val -0.04 -0.04 Sorb

-0.06 Arch Poly -0.06 Scaph HTU1 -0.08 -0.08 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 B 0.08 D 0.08 Veti Arch Val Arch 0.06 0.06 Val 0.04 Veti 0.04 0.02 0.02 Opist Pul HTU2 0.00 HTU3 Pul HTU6-7 0.00 HTU4-5 -0.02 Opist Nerit Nerit -0.02 Pat -0.04 Sorb Pat Sorb -0.04 -0.06 Scaph -0.08 -0.06 Scaph HTU1 -0.10 -0.08 -0.12 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 -0.10 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 PCA 1 PCA 1 Phylogenetics - IB 200B 8 Feb 2011

Developmental Sequence Data Maxwell & Harrison (2009)

Phylogenetics - IB 200B 8 Feb 2011

Hunt & Yasuhara (2010)