4 Phylogeny of Animals
137
However, the genomic processes that underlie such morphological switches
remain to be uncovered. The relationship between the evolution of genomes and
morphology constitutes one of the main current questions in evolutionary biology,
especially because these two aspects of organisms are reputed to have undergone radically divergent modalities of evolution: strong selection for bodies versus
neutralistic drift for genomes. The Evodevo field has recently uncovered the developmental genetics sources of macroevolutionary changes but these insightful studies
remain limited to the molecular actors involved in specific genetic pathways (Muller
2007). On the other hand, the extensive study of both multigenic families and
genome rearrangements that is underpinning phylogenomics could shed new light
on developmental regulation at the genome scale, especially when it is associated with molecular genetics data acquired using model organisms. For instance,
Domazet-Los et al. recently introduced the so-called “phylostratigraphic” approach
involving comparison of the expression patterns and structures of multigenic families for a large number of genes involved in the development of germ layers
(Domazet-Loso et al. 2007). They observed differences between the phylogenetic
origins of all these genes and showed that those associated with the ectoderm,
for example, are most likely more ancient. These promising findings plead for a
renewed interest in neglected animal groups whose importance for comparative
approaches and character orientation is undisputable. The extension of genome
sequencing to some key organisms with key phylogenetic positions, paleontology
and development, such as ctenophores and chaetognaths, constitutes the next step
toward a better understanding of metazoan evolution.
References
Aboobaker AA, Blaxter ML (2003) Hox Gene Loss during Dynamic Evolution of the Nematode
Cluster. Curr Biol 13:37–40
Adoutte A, Balavoine G, Lartillot N, Lespinet O, Prud’homme B, de Rosa R (2000) The new
animal phylogeny: reliability and implications. Proc Natl Acad Sci U S A 97:4453–4456
Aguinaldo AM, Turbeville JM, Linford LS, Rivera MC, Garey JR, Raff RA, Lake JA (1997)
Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387:
489–493
Anderson FE, Cordoba AJ, Thollesson M (2004) Bilaterian phylogeny based on analyses of a
region of the sodium-potassium ATPase beta-subunit gene. J Mol Evol 58:252–268
Aristotle (1965) De Generatione animalium, tr. Arthur Platt, Clarendon Press, Oxford
Balavoine G, de Rosa R, Adoutte A (2002) Hox clusters and bilaterian phylogeny. Mol Phylogenet
Evol 24:366–373
Ball EE, Miller DJ (2006) Phylogeny: the continuing classificatory conundrum of chaetognaths.
Curr Biol 16:R593–R596
Barnes RD (1974) Invertebrate zoology. W.B. Saunders Company, Philadelphia.
Baurain D, Brinkmann H, Philippe H (2007) Lack of resolution in the animal phylogeny: closely
spaced cladogeneses or undetected systematic errors?. Mol Biol Evol 24:6–9
Bergsten J (2005) A reviews of long-branch attraction. Cladistics 21:163–193
Blair JE, Ikeo K, Gojobori T, Hedges SB (2002) The evolutionary position of nematodes. BMC
Evol Biol 2:7
137
However, the genomic processes that underlie such morphological switches
remain to be uncovered. The relationship between the evolution of genomes and
morphology constitutes one of the main current questions in evolutionary biology,
especially because these two aspects of organisms are reputed to have undergone radically divergent modalities of evolution: strong selection for bodies versus
neutralistic drift for genomes. The Evodevo field has recently uncovered the developmental genetics sources of macroevolutionary changes but these insightful studies
remain limited to the molecular actors involved in specific genetic pathways (Muller
2007). On the other hand, the extensive study of both multigenic families and
genome rearrangements that is underpinning phylogenomics could shed new light
on developmental regulation at the genome scale, especially when it is associated with molecular genetics data acquired using model organisms. For instance,
Domazet-Los et al. recently introduced the so-called “phylostratigraphic” approach
involving comparison of the expression patterns and structures of multigenic families for a large number of genes involved in the development of germ layers
(Domazet-Loso et al. 2007). They observed differences between the phylogenetic
origins of all these genes and showed that those associated with the ectoderm,
for example, are most likely more ancient. These promising findings plead for a
renewed interest in neglected animal groups whose importance for comparative
approaches and character orientation is undisputable. The extension of genome
sequencing to some key organisms with key phylogenetic positions, paleontology
and development, such as ctenophores and chaetognaths, constitutes the next step
toward a better understanding of metazoan evolution.
References
Aboobaker AA, Blaxter ML (2003) Hox Gene Loss during Dynamic Evolution of the Nematode
Cluster. Curr Biol 13:37–40
Adoutte A, Balavoine G, Lartillot N, Lespinet O, Prud’homme B, de Rosa R (2000) The new
animal phylogeny: reliability and implications. Proc Natl Acad Sci U S A 97:4453–4456
Aguinaldo AM, Turbeville JM, Linford LS, Rivera MC, Garey JR, Raff RA, Lake JA (1997)
Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387:
489–493
Anderson FE, Cordoba AJ, Thollesson M (2004) Bilaterian phylogeny based on analyses of a
region of the sodium-potassium ATPase beta-subunit gene. J Mol Evol 58:252–268
Aristotle (1965) De Generatione animalium, tr. Arthur Platt, Clarendon Press, Oxford
Balavoine G, de Rosa R, Adoutte A (2002) Hox clusters and bilaterian phylogeny. Mol Phylogenet
Evol 24:366–373
Ball EE, Miller DJ (2006) Phylogeny: the continuing classificatory conundrum of chaetognaths.
Curr Biol 16:R593–R596
Barnes RD (1974) Invertebrate zoology. W.B. Saunders Company, Philadelphia.
Baurain D, Brinkmann H, Philippe H (2007) Lack of resolution in the animal phylogeny: closely
spaced cladogeneses or undetected systematic errors?. Mol Biol Evol 24:6–9
Bergsten J (2005) A reviews of long-branch attraction. Cladistics 21:163–193
Blair JE, Ikeo K, Gojobori T, Hedges SB (2002) The evolutionary position of nematodes. BMC
Evol Biol 2:7