Biologue

Issue 26
Australian Biological Resources Study, April 2002
ISSN 0814 B8880

Participatory Programme (continued)

Research Grants (continued)

Articles from ABRS Grantees (continued)

Calcareous sponges (Porifera: Calcarea) provide clues for the conservation biology of the Great Barrier Reef World Heritage Area
Article by Gert Wörheide & John NA Hooper, Queensland Centre for Biodiversity, Queensland Museum, PO Box 3300 BRISBANE SOUTH QLD 4101 Our recent phylogeographic studies of western Pacific calcareous sponges (Porifera: Calcarea) have highlighted the importance of outlier (exogenous) populations to the conservation biology of the Great Barrier Reef (GBR), emphasising the underpinning role of systematics in marine resource management. Calcareous sponges are a small (circa 500 spp worldwide) and largely understudied groups, but nevertheless are already acknowledged to be phylogenetically important. Recent molecular data suggest that they may be more closely related to Cnidaria and Ctenophora than to the other sponge classes, Demospongiae and Hexactinellida, probably rendering phylum Porifera paraphyletic (Borchiellini et al., 2001; Medina et al., 2001). The temperate Australian fauna is relatively well known from the naturalistic/scientific studies of the late 19th century (e.g. Carter, 1886), whereas the tropical fauna was very poorly known prior to this current project. This shortcoming is partly attributed to the mostly cryptic lifestyle of calcareans in tropical coral reefs, where they mainly live in cryptic habitats, like caves and overhangs and other sciaphilic habitats, which the early naturalist explorers were rarely able to sample. Prior to our project, only 14 species had been described from the entire GBR in over 100 years. By comparison, since the start of the project we have already published 14 new species, redescribed 7 others that were barely recognisable from their original descriptions (Wörheide & Hooper, 1999, 2002; Figure 1), and have also amassed a large collection of both undescribed species (awaiting publication) and populations of known species (awaiting genetic analysis) from different parts of the GBR. These collections were undertaken during various biodiversity surveys of sessile marine invertebrates by the Queensland Museum, for which this particular component was initially funded (1998-2000) by a postdoctoral fellowship from the German Academic Exchange Service (DAAD) to GW, and subsequently (2000-2002) by a research grant from ABRS and research fellowships from AstraZeneca R & D Griffith University (to GW and JH). The number of new species of calcareans is expected to increase dramatically in the near future as these data are published, and already the project has contributed significantly to revising many initial decisions published in the Zoological Catalogue of Australia, Porifera (Hooper & Wiedenmayer, 1994). Calcarean taxonomy is extremely difficult, certainly in comparison to other sponge taxa, requiring specialised histological preparation techniques that permit the study of skeletal and soft tissue features to differentiate species (Fig. 2). The systematics of this group is even more challenging, requiring new tools (e.g. molecular data) to corroborate or refute morphological hypotheses. We found in a preliminary phylogenetic study of GBR calcarean family Leucettidae, that the phylogenetic relationships inferred from classical morphological characters are not concordant with the phylogeny inferred from molecular data, requiring a complete revision of this family - and probably others too. A second recently completed phylogeographic study focussed on the allegedly widespread western Pacific species Leucetta chagosensis (Calcinea: Leucettidae) as a model taxon (Wörheide et al., 2000; Wörheide et al., in prep). It revealed a genetic separation of the GBR populations of L. chagosensis into two divergent clades. We discovered a northern/central clade, which also included specimens from Guam and Taiwan, and a southern/subtropical clade, which extended south to Brisbane. Both clades overlapped only narrowly in their geographic distributions, with a demarcation line extending from the Whitsunday Islands to the Swain Reefs. A nested clade analysis inferred that the distribution of both GBR clades was controlled by past fragmentation events with subsequent range expansion, most likely during past (glacial) sea level oscillations. It was inferred that during sea level low stands, when the GBR was dry, and thus uninhabitable by marine organisms, the northern GBR clade found refuge on the Queensland Plateau and the southern clade in the subtropical regions. With rising sea level, the GBR was repopulated from the Queensland Plateau and the subtropical regions, giving rise to present day heterogeneous distributions of these two populations. Our data highlight the importance of both regions for future conservation studies of the GBR, which are probably pivotal to its conservation and management as they might provide the GBR with an essential potential for restocking after catastrophic events. References: Borchiellini C., Manuel, M., Alivon, E., Boury-Esnault, N., Vacelet, J. & Le Parco, Y. (2001): Sponge paraphyly and the origin of Metazoa. Journal of Evolutionary Biology, 14(1): 171-179. Carter H.J. (1886): Descriptions of sponges from the neighbourhood of Port Philipps Head, S. Australia. Annals and Magazine of Natural History, 5(17/18): 431-441, 502-516, 34-55, 126-149. Hooper J.N.A. & Wiedenmayer, F. (1994): Porifera. In, Wells, A. ed. Zoological Catalogue of Australia, pp. 1-624 (CSIRO Australia, Melbourne). Medina M., Collins, A.G., Silberman, J.D. & Sogin, M.L. (2001): Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA. Proceedings of the National Academy of Science of the USA, 98(17): 9707-9712. Wörheide G. & Hooper, J.N.A. (1999): Calcarea from the Great Barrier Reef. 1: Cryptic Calcinea from Heron Island and Wistari Reef (Capricorn-Bunker Group). Memoirs of the Queensland Museum, 43(2): 859-891. Wörheide G. & Hooper, J.N.A. (2002): New species of Calcaronea (Porifera: Calcarea) from cryptic habitats of the southern Great Barrier Reef (Heron Island and Wistari Reef, Capricorn-Bunker Group, Australia). Journal of Natural History, in press. Wörheide G., Degnan, B.M. & Hooper, J.N.A. (2000): Population phylogenetics of the common coral reef sponges Leucetta spp. and Pericharax spp. (Porifera: Calcarea) from the Great Barrier Reef and Vanuatu. Abstracts, 9th International Coral Reef Symposium, Bali, October 2000: 23. Wörheide G., Hooper, J.N.A. & Degnan, B.M. (in prep): Phylogeography of western Pacific Leucetta 'chagosensis' (Porifera: Calcarea) from ribosomal DNA sequences: implications for population history and conservation of the Great Barrier Reef World Heritage Area (Australia).

Calcareous sponges (Porifera: Calcarea) provide clues for the conservation biology
of the Great Barrier Reef World Heritage Area

Article by
Gert Wörheide & John NA Hooper, Queensland Centre for Biodiversity, Queensland Museum, PO Box 3300 BRISBANE SOUTH QLD 4101

Our recent phylogeographic studies of western Pacific calcareous sponges (Porifera: Calcarea) have highlighted the importance of outlier (exogenous) populations to the conservation biology of the Great Barrier Reef (GBR), emphasising the underpinning role of systematics in marine resource management. Calcareous sponges are a small (circa 500 spp worldwide) and largely understudied groups, but nevertheless are already acknowledged to be phylogenetically important. Recent molecular data suggest that they may be more closely related to Cnidaria and Ctenophora than to the other sponge classes, Demospongiae and Hexactinellida, probably rendering phylum Porifera paraphyletic (Borchiellini et al., 2001; Medina et al., 2001).

The temperate Australian fauna is relatively well known from the naturalistic/scientific studies of the late 19th century (e.g. Carter, 1886), whereas the tropical fauna was very poorly known prior to this current project. This shortcoming is partly attributed to the mostly cryptic lifestyle of calcareans in tropical coral reefs, where they mainly live in cryptic habitats, like caves and overhangs and other sciaphilic habitats, which the early naturalist explorers were rarely able to sample. Prior to our project, only 14 species had been described from the entire GBR in over 100 years. By comparison, since the start of the project we have already published 14 new species, redescribed 7 others that were barely recognisable from their original descriptions (Wörheide & Hooper, 1999, 2002; Figure 1), and have also amassed a large collection of both undescribed species (awaiting publication) and populations of known species (awaiting genetic analysis) from different parts of the GBR.

These collections were undertaken during various biodiversity surveys of sessile marine invertebrates by the Queensland Museum, for which this particular component was initially funded (1998-2000) by a postdoctoral fellowship from the German Academic Exchange Service (DAAD) to GW, and subsequently (2000-2002) by a research grant from ABRS and research fellowships from AstraZeneca R & D Griffith University (to GW and JH). The number of new species of calcareans is expected to increase dramatically in the near future as these data are published, and already the project has contributed significantly to revising many initial decisions published in the Zoological Catalogue of Australia, Porifera (Hooper & Wiedenmayer, 1994).

Calcarean taxonomy is extremely difficult, certainly in comparison to other sponge taxa, requiring specialised histological preparation techniques that permit the study of skeletal and soft tissue features to differentiate species (Fig. 2). The systematics of this group is even more challenging, requiring new tools (e.g. molecular data) to corroborate or refute morphological hypotheses. We found in a preliminary phylogenetic study of GBR calcarean family Leucettidae, that the phylogenetic relationships inferred from classical morphological characters are not concordant with the phylogeny inferred from molecular data, requiring a complete revision of this family - and probably others too. A second recently completed phylogeographic study focussed on the allegedly widespread western Pacific species Leucetta chagosensis (Calcinea: Leucettidae) as a model taxon (Wörheide et al., 2000; Wörheide et al., in prep). It revealed a genetic separation of the GBR populations of L. chagosensis into two divergent clades.

We discovered a northern/central clade, which also included specimens from Guam and Taiwan, and a southern/subtropical clade, which extended south to Brisbane. Both clades overlapped only narrowly in their geographic distributions, with a demarcation line extending from the Whitsunday Islands to the Swain Reefs. A nested clade analysis inferred that the distribution of both GBR clades was controlled by past fragmentation events with subsequent range expansion, most likely during past (glacial) sea level oscillations. It was inferred that during sea level low stands, when the GBR was dry, and thus uninhabitable by marine organisms, the northern GBR clade found refuge on the Queensland Plateau and the southern clade in the subtropical regions. With rising sea level, the GBR was repopulated from the Queensland Plateau and the subtropical regions, giving rise to present day heterogeneous distributions of these two populations. Our data highlight the importance of both regions for future conservation studies of the GBR, which are probably pivotal to its conservation and management as they might provide the GBR with an essential potential for restocking after catastrophic events.

References:

Borchiellini C., Manuel, M., Alivon, E., Boury-Esnault, N., Vacelet, J. & Le Parco, Y. (2001): Sponge paraphyly and the origin of Metazoa. Journal of Evolutionary Biology, 14(1): 171-179.

Carter H.J. (1886): Descriptions of sponges from the neighbourhood of Port Philipps Head, S. Australia. Annals and Magazine of Natural History, 5(17/18): 431-441, 502-516, 34-55, 126-149.

Hooper J.N.A. & Wiedenmayer, F. (1994): Porifera. In, Wells, A. ed. Zoological Catalogue of Australia, pp. 1-624 (CSIRO Australia, Melbourne).

Medina M., Collins, A.G., Silberman, J.D. & Sogin, M.L. (2001): Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA. Proceedings of the National Academy of Science of the USA, 98(17): 9707-9712.

Wörheide G. & Hooper, J.N.A. (1999): Calcarea from the Great Barrier Reef. 1: Cryptic Calcinea from Heron Island and Wistari Reef (Capricorn-Bunker Group). Memoirs of the Queensland Museum, 43(2): 859-891.

Wörheide G. & Hooper, J.N.A. (2002): New species of Calcaronea (Porifera: Calcarea) from cryptic habitats of the southern Great Barrier Reef (Heron Island and Wistari Reef, Capricorn-Bunker Group, Australia). Journal of Natural History, in press.

Wörheide G., Degnan, B.M. & Hooper, J.N.A. (2000): Population phylogenetics of the common coral reef sponges Leucetta spp. and Pericharax spp. (Porifera: Calcarea) from the Great Barrier Reef and Vanuatu. Abstracts, 9th International Coral Reef Symposium, Bali, October 2000: 23.

Wörheide G., Hooper, J.N.A. & Degnan, B.M. (in prep): Phylogeography of western Pacific Leucetta 'chagosensis' (Porifera: Calcarea) from ribosomal DNA sequences: implications for population history and conservation of the Great Barrier Reef World Heritage Area (Australia).