sign in sign up
<<
Home , Malay Archipelago

a

e-ISSN: 1948-6596 https://escholarship.org/uc/fb doi:10.21425/F5FBG41470 Perspective and meta-archipelagos

Robert J. Whittaker1,2,*, José María Fernández-Palacios3, Thomas J. Matthews4,5, François Rigal5,6 and Kostas A. Triantis7

1 School of Geography and the Environment, University of Abstract. The term meta- has been in use in cultural Oxford, Oxford OX1 3QY, UK. studies for some time, to refer to certain complex areas in which the boundaries between conventionally recognised archipelagos are 2 Center for Macroecology, Evolution indistinct, although the concept also carries additional connotations. and Climate, Natural History Use of the term in appears more recent and without Museum of Denmark, University effort to prescribe its meaning. We outline, from a biogeographical of Copenhagen, Copenhagen, perspective, distinctions between meta-archipelagos and archipelagos Denmark. and those not occurring within either collective grouping, 3 Island Ecology and Biogeography highlighting that network analysis tools provide metrics for formal Research Group, Instituto analytical purposes. Universitario de Enfermedades Keywords: Biogeographical regions, island biogeography, Tropicales y Salud Pública de meta‑archipelago, modularity, network analysis Canarias (IUETSPC), Universidad de La Laguna, Tenerife, Canary Islands, Spain. Group and Universidade dos Materiaux, MIRA, UMR5254, 4 School of Geography, Açores–Depto. de Ciências 64000, PAU, France and Environmental Sciences, Agrárias e Engenharia do and Birmingham Institute of Ambiente, PT-9700-042, Angra 7 Department of Ecology and Forest Research, University of do Heroísmo, Açores, Portugal. Taxonomy, Faculty of Biology, Birmingham, Birmingham B15 6 CNRS - Université de Pau et National and Kapodistrian 2TT, UK. des Pays de l’Adour – E2S University of Athens, Athens 5 Centre for Ecology, Evolution UPPA, Institut des Sciences GR-15784, Greece. and Environmental Changes Analytiques et de Physico-Chimie *Corresponding author. Email: (CE3C)–Azorean Biodiversity pour l’Environnementet les [email protected]

“…the are an island bridge connecting, in it is often debatable where one archipelago ends and “another way,” North to . This geographical another begins (Benítez Rojo and Maraniss 1985, accident gives the entire area, including its continental above). This matters in island biogeography as many foci, the character of an archipelago, that is, a of our analyses are based on data sets structured into discontinuous conjunction…[which] can be seen as an archipelagos (e.g., Bunnefeld and Phillimore 2012). island that “repeats” itself….Which one, then would The rationale for this is that islands configured in be the repeating island, Jamaica, Aruba, Puerto Rico, isolated geographical groups exchange information Miami, Haiti, Recife? Certainly none of the ones that (i.e., there are movements and exchanges of pollen, we know. That original, that island at the center, is spores, propagules, individuals, semi-nomadic flocks, as impossible to reach as the hypothetical Antilli[a] and perhaps even nutrients and energy) and they do that reappeared time and again, always fleetingly, so to a significantly greater degree than they do with in the cosmographers’ charts. This is again because any other more distant land-masses. the is a meta-archipelago…” Benítez Rojo In analytical terms, some might argue the islands and Maraniss (1985, p. 431–432) within such archipelagos to be spatially auto- correlated and thus non-independent data points. The etymology of the word archipelago points But this depends on the questions being asked. In to a derivation linked to the Italian arcipelago as a practice, for some purposes island biologists are name for the Aegean (principal ) (Fig. 1). The wider engaged in studying process and pattern at the meaning developed presumably since the intra-island level, while for other purposes it is the is replete with large numbers of islands. We use the inter-island patterns within the archipelago (such term today for chains, clusters, or collections of islands. as the species–area relationship) that are the focus Yet in complex island regions such as the Caribbean of interest and analysis (e.g., Whittaker et al. 2017, or South-East (, New , Price et al. 2018). Moreover, to establish the generality ) and parts of the South Pacific/, of our models and hypotheses, we often wish to

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 1 Whittaker et al. Archipelagos and meta-archipelagos

’ Figure 1. A map of the Aegean, by Nicolaum Visscher (1649−1702), published around 1681, illustrating a complex island region in which it is challenging to decide on archipelago or meta-archipelago membership from a biological perspective. Sourced from Wikimedia Commons, wherein it is stated that this is an image from the digital and/or physical collections of the Koninklijke Bibliotheek, the Dutch National Library. extend our analyses to encompass islands belonging demonstrates that even quite distant archipelagos to many sets of archipelagos (e.g., Bunnefeld and can and do exchange ‘information’ (e.g., Gillespie et Phillimore 2012, Norder et al. 2018). This generates al. 2008, Hembry and Balukjian 2016), it is not always a further challenge, which is to determine the degree straightforward to determine ‘natural units’ for specific to which nearby archipelagos are truly independent biogeographical analyses. Answering such a question ‘replicates’ as opposed to being interconnected by similar levels of information exchange as the islands becomes a matter of quantification and determining within our archipelagos. As, increasingly, evidence of thresholds that might permit objective determination movement behaviours and of past propagule exchange of where the boundaries between archipelagos can and colonization events encoded in phylogenetic data be drawn (see Box 1).

Box 1. Distinguishing the meta-archipelago from the archipelago: a biogeographical definition A meta-archipelago is a group of archipelagos that have and continue to exhibit a meaningful level of information exchange (e.g., propagules, colonization events) and within which such exchanges occur substantially more often than with other areas but significantly less often than is the case within a single archipelago. In cases of large, persistent and well isolated systems, the meta-archipelago may be equivalent to a biogeographical sub-region or perhaps to a biogeographical network, but the concept may also be applied to groups of entities within smaller, impermanent and less isolated systems, such as constellations of habitat islands.

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 2 Whittaker et al. Archipelagos and meta-archipelagos

Biogeographers have of course been working regions (Jønsson and Holt 2015). However, efforts on these questions since the foundations of the have been made to draw lines sub-dividing discipline (Box 2). At the coarsest of scales it is basins. Examples include the subdivision of the what biogeographical regionalization schemes South East Asian / island region by are all about (Wallace 1880, Holt et al. 2013). Wallace’s Line, Weber’s Line and etc., based on In practice, the placing of distant oceanic islands zoogeographical data (Whittaker and Fernández- into regionalization schemes has proven problematic Palacios 2007) or of the region based because such islands often exhibit multiple source on phytogeographical data (e.g., Renvoize 1979).

Box 2. Extract from the preface of The Archipelago, by (1869, Vol. I) The question of how to treat complex archipelagic regions has been of interest since the foundations of the discipline of biogeography. In an attempt to identify distinct units within the broad Malay archipelago, Wallace stated:

“…I divide the Archipelago into five groups of islands, as follows: I. The Indo- Malay Islands: comprising the and , , , and , II. The Group: comprising the islands of Timor, , , and Lombock, with several smaller ones, III. Celebes: comprising also the Sula Islands and Bouton, IV. The Moluccan Group: comprising Bouru, Ceram, Batchian, Gilolo, and Morty; with the smaller islands of Ternate, Tidore, Makian, Kaióa, Amboyna, Banda, Goram, and Matabello, V. The Papuan Group: comprising the great island of , with the Aru Islands, Mysol, Salwatty, Waigiou, and several others. The Ke Islands are described with this group on account of their ethnology, though zoologically and geographically they belong to the Moluccas…”

Later, he referred to the “Philippine Archipelago” as part of : an archipelago within an archipelago.

More recently, efforts have been made to apply reflecting richness of non‑endemics, is characteristic sophisticated modern methods of network analysis of typically smaller islands distant from mainland to (the island region between South-East sources but situated near the boundaries between Asian and Australasian continental shelfs) and to modules. These analyses thus help determine, the Caribbean that do more than simply identify within complex island regions, how best to delimit the boundaries between different sub-regions (i.e., archipelago membership and inter-connectedness groups of islands), also called modules in network from a biogeographical perspective. theory. These analyses determine the degree of In slightly simpler circumstances than Wallacea, compositional connectedness based on species the Caribbean, or the Indian Ocean, the North distributions and identify the degree of local vs Atlantic archipelagos west of Northern and regional topological linkage using null models Iberia have been grouped phytogeographically into to assess the significance of the linkages. In two the Macaronesian region (Fig. 2; Vanderpoorten et papers, Carstensen et al. (2012) and Dalsgaard et al. 2007, Whittaker and Fernández-Palacios 2007, al. (2014) develop this approach to identify four Torre et al. 2018), a label that has recently been biogeographical roles for islands in the network: used for a new line of gin distilled in the Canaries. (i) network hubs are islands possessing both many Rather fine it is too: evidently benefitting from the local species and many shared across the region; indigenous botanical ingredients. But, for analytical (ii) module hubs have many local species but few purposes, should we lump the islands at the level of of regional distribution; (iii) connectors possess a the Macaronesian region, or by archipelago (Canaries, few local species but many shared across the region; Azores, etc), or even, for the Azores, for example, and finally (iv) peripheral islands have few local sub-divide the archipelago into three sub-groups? species and few shared regionally. Their analyses Perhaps the answer depends on the question being identified four modules within Wallacea and six asked? We should also note that the boundaries within the , assigning islands within these and even the validity of Macaronesia itself has also modules to the four categories just listed. In general, been the subject of controversy, with evidence to remote large islands tend to possess high richness suggest that the Cape Verde islands, far to the south of endemics and therefore feature local linkage, (Fig. 2), may not properly belong in a grouping with whereas stronger regional topological linkages, the other archipelagos (Azores, Madeira, Savage

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 3 Whittaker et al. Archipelagos and meta-archipelagos

[Salvage] Islands, Canaries) and that the degree of We propose that the term archipelago be used Macaronesian distinctiveness depends on the choice for a group of islands, typically closely spaced, which of taxa (cf. García-Talavera 1999, Fernández-Palacios have historically exchanged biological information and Dias 2001, Vanderpoorten et al. 2007). and which have continued to do so, with significantly higher frequency than they do with any other land masses. Mostly, islands within archipelagos have similar origins and geo-environmental dynamics, and share a common source pool(s). By contrast, the meta‑archipelago should be used for a collection of nearby archipelagos whereby the information exchange is at a lower level (see Fig. 3), yet has been and remains sufficient to denote the membership of the islands as having shared legacies distinguishing them from other collections of islands and/or mainlands. The archipelagos within a meta-archipelago are likely to embrace more varied origins, geo-dynamics and source pool biases. These usages are thus akin, in terms of compositional pattern, to the notions of modules and networks (sensu Newman 2006, Carstensen et al. 2012, Poisot 2013, Thébault 2013, Dalsgaard et al. 2014) but have perhaps broader intuitive appeal, extendable across historical and contemporary pattern and process, from oceanic island systems (in which many species are generated through in situ diversification) to networks of habitat islands (Box 1).

Figure 2. Macaronesia is a recognized but controversial biogeographical (in origin phytogeographical) region consisting of the archipelagos shown, together with a narrow coastal strip of north- and with affinities to the tip of the (after García-Talavera 1999).

To accommodate the notion of different degrees of connectivity between and among groups of islands, we suggest adoption of the term meta-archipelago (Box 1). This term does not yet appear to be in common usage in island biogeography, although some very brief mentions have occurred (e.g., see Kueffer et al. 2016, Triantis et al. 2016; the latter defining meta-archipelagos simply as archipelagos of archipelagos). However, the term has appeared in cultural studies, in which it Figure 3. The meta-archipelago: in this hypothetical case, a appears to trace back to the work of the Cuban writer constellation of three archipelagos that have and continue Antonio Benítez-Rojo (see Benítez-Rojo and Maraniss to exhibit a meaningful level of information exchange (1985) or Benítez-Rojo’s (1992) The repeating island: (e.g., propagules) signified by the lines of varying thickness the Caribbean and post-modern perspective). In his joining the islands; exchanges among constituent archipelagos work the meta-archipelago is described as a chaos should occur significantly less often than the level of exchange “having neither a boundary nor a center” and within typical within an archipelago, but significantly more than which culturally, each island is a “copy of a different with other areas. Inspired by a sketch in Poisot (2013). one, founding and refounding ethnological materials like a cloud will do with its vapor.” Well, we get the drift and the concept proposed captures much of what In a previous essay, Triantis et al. (2016) introduced we are after, particularly in the idea of replication the idea of the meta-archipelago level without, however, of units which actually embrace difference as well elaborating on it. In illustration, they mentionedTarphius as degrees of connectivity, and the notion of the beetles, a genus with representatives in both Old and importance of connection not only amongst islands New and which are monophyletic at the level but between the meta-archipelago and other areas. of Macaronesia (Amorim et al. 2012). They occur on Yet, for biogeographical purposes we need a rather three of the Macaronesian archipelagos (Madeira, different formulation. Azores and Canaries), and are also monophyletic for the

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 4 Whittaker et al. Archipelagos and meta-archipelagos

Azores as a whole, although on an island level within applicable across different taxa the labelling needs the Azores this is not the case and instead multiple to be for it to be useful? Methods and approaches colonization events have been invoked. Such data applied for biogeographical regionalization and/or provide clear indication of more frequent exchange network analyses that use distributional (sometimes amongst islands within an archipelago than between with phylogenetic) data from multiple taxa might be archipelagos, while justifying the treatment of the of use in resolving this question (e.g., Holt et al. 2013, meta-archipelago as being distinct from the mainland Ficetola et al. 2017). source regions. Other plant and animal lineages have Do we need a new term? The proliferation of also radiated repeatedly in multiple archipelagos within terms is not always helpful to a discipline, although Macaronesia, while typically generating single island arguably the greater problem is the inconsistent use endemic species on particular islands (Price et al. 2018). of the terms we have. In this instance, we suggest that Similar patterns are found in other complex island the term meta-archipelago has appeal and may prove regions (e.g., : Gillespie et al. 2008). useful. In particular, it may encourage ecological island It seems likely that the appropriate scales of separation biogeographers to conceptualize the islands they study of membership and the particular data and metrics as belonging not simply to one group, framed in relation best suited to identify groups of islands as belonging to a particular, distant mainland, but to consider and to either archipelagos or meta-archipelagoes will to analyse how the biota of each island may be part of depend on the particular biogeographical purposes. a loose, but structured network of concentric layers of Depending on the data that are fed into such analyses relatedness and exchange. The layers of archipelago and the methods of analysis selected, it may be possible to develop these approaches to emphasize either and meta-archipelago provide the two closest layers contemporary patterns of movement and exchange, or of the networks that exist around many islands, while to emphasize past process regimes, reflecting deeper the failure to identify such patterns of linkage would time evolutionary linkages or, for example, the regimes identify an island as either a truly isolated island, an of currents, climate and sea-level conditions of the island that sits in the pocket of a dominant mainland, Pleistocene glacial episodes (Norder et al. 2018). For or one that belongs to a continuum or patchwork of at least some of these purposes, the analytical tools more or less connected habitat patches. Ecologists are already well developed (e.g., Dalsgaard et al. 2014, and biogeographers are familiar with the terms Torre et al. 2018, Triantis et al. 2018). meta‑population and meta-community, which denote In some geographical circumstances (e.g., islands the subdivision of populations and communities into within long, thin lakes), islands may actually be areas that are insufficiently connected to form a exchanging biological information with the mainland single entity but yet are not entirely independent of more frequently than with each other. In such one another (e.g., Leibold and Chase 2017). The term circumstances, the groups of islands concerned may meta-archipelago in its essence, simply extends this be useful for many island biogeographical purposes, concept into island biogeographical pattern and process, but arguably do not warrant the label of archipelago embracing both ecological-island-biogeography and by the above definition. Paradoxically, by this approach ‘evolutionary/historical-island biogeography’, hopefully might the islands of the Aegean Sea be deemed merely encouraging a free flow of discussion bridging these an island group or region, rather than one archipelago, traditions. or meta-archipelago? Here the evidence for five out of the nine taxa considered in Triantis et al. (2018, References p. 287), is that, for example, Crete and the surrounding islets are quite distinct from the rest of the Aegean Amorim, I.R., Emerson, B.C., Borges, P.A.V. & Wayne, islands, and thus Crete and its islets can be seen as R.K. (2012) Phylogeography and molecular an archipelago within an Aegean meta-archipelago. Were it the case that all taxa have similar scales phylogeny of Macaronesian island Tarphius of interaction with fragmented land- and seascapes, (Coleoptera: Zopheridae): why are there so few then it might be realistic to think of prescribing species in the Azores? Journal of Biogeography, a single framework of islands, archipelagos and 39, 1583–1595. meta‑archipelagos. But as previous regionalization and filter effect analyses have shown, and as recent Benítez-Rojo, A. (1992) The repeating island: The modularity analyses of Macaronesia also show (Torre et Caribbean and the postmodern perspective. al. 2018), this is not the case. Hence, the distributions Duke University Press, Durham, N.C. [or see and exchanges of more vagile taxa frequently span 1989 version in Spanish] multiple archipelagos, whilst the least vagile taxa exhibit largely within-archipelago or within-island Benítez-Rojo, A. & Maraniss, J. (1985) The repeating scales of distribution and exchange. Even within a island. Review and Bread Loaf single taxon (e.g., bryophytes, seed plants, beetles, Quarterly, 7, 430–452. birds, land mammals, etc), there is always a significant Bunnefeld N. & Phillimore A.B. (2012) Island, span of movement or dispersal attainment. In using the terms island, archipelago and meta-archipelago, archipelago and taxon effects: mixed models therefore, there is a further question of how broadly as a means of dealing with the imperfect

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 5 Whittaker et al. Archipelagos and meta-archipelagos

design of nature’s experiments. Ecography, Oxford. doi:10.1093/OBO/9780199830060- 35, 15–22. 0149. Carstensen, D.W., Dalsgaard, B., Svenning, J-C., Rahbek, Leibold, M.A. & Chase, J.M. (2017) Metacommunity C., Fjeldså, J., Sutherland, W.J. & Olesen, J.M. ecology. Princeton University Press, Princeton. (2012) Biogeographical modules and island Newman, M.E.J. (2006) Modularity and community roles: a comparison of Wallacea and the West structure in networks. Proceedings of the Indies. Journal of Biogeography, 39, 739–749. National Academy of Sciences USA 103, Dalsgaard, B., Carstensen, D.W., Fjeldså, J., Maruyami, 8577–8582. P.K., Rahbek, C., Sandel, B., Sonne, J., Svenning, Norder, S.J., Proios, K.V., Whittaker, R.J., et al. (2018) J-C., Wang, Z. & Sutherland, W.J. (2014) Beyond the Last Glacial Maximum: Island Determinants of bird species richness, endemism, endemism is best explained by long-lasting and island network roles in Wallacea and the and Biogeography, doi:10.1111/geb.12835. current and historical climate matter? Ecology Poisot,archipelago T. (2013). An configurations. a posteriori measure Global of networkEcology andWest Evolution, Indies: is 20,geography 4019–4031. sufficient or does modularity. F1000Research, 2, doi: 10.12688/ Fernández-Palacios, J.M. & Dias, E. (2001) Marco f1000research.2-130.v3. Price, J.P., Otto, R., Menezes de Sequeira, M., Kueffer, de las Islas Canarias. Ecología y conservación (eds.biogeográfico J.M. Fernández-Palacios Macaronésico. In& J.L.Naturaleza Martín- Palacios, J.M. (2018) Colonization and Esquivel) pp. 45–52. Editorial Turquesa, Santa C., Schaefer, H., Caujapé-Castells, J. & Fernández- Cruz de Tenerife. in three Macaronesian archipelagos. Journal diversification shape species–area relationships Ficetola, G.F., Mazel, F. & Thuiller, W. (2017) Global of Biogeography, 45, 2027–2039. determinants of zoogeographical boundaries. Renvoize, S.A. (1979) The origins of Indian Ocean Nature Ecology & Evolution, 1, 0089. Bramwell), pp. 107–129. Academic Press, García-Talavera, F. (1999) La Macaronesia. London.island floras. In Plants and islands (ed. D. y paleoecológicas. In Ecología y Cultura en CanariasConsideraciones (eds. J.M. geológicas, Fernández-Palacios, biogeográficas J.J. presence-absence matrices and bipartite Thébault,networks: E. (2013) insights Identifying into modularity compartments measures. in Bacallado, & J.A. Belmonte) pp. 39–63. Cabildo Journal of Biogeography, 40, 759–768. Insular de Tenerife, Santa Cruz de Tenerife. Torre, G., Fernández-Lugo, S., Guarino, R. & Fernández- Gillespie, R.G., Claridge, E.M. & Goodacre, S.L. Palacios, J.M. (2018) Network analysis by (2008) Biogeography of the fauna of French simulated annealing of taxa and islands of Macaronesia (North ). Ecography, a series of hot spot archipelagos. Philosophical doi.org/10.1111/ecog.03909. TransactionsPolynesia: diversification of the Royal Societywithin and B: Biological between Triantis, K.A., Whittaker, R.J., Fernández-Palacios, Sciences, 363, 3335–3346. J.M. & Geist, D.J. (2016) Oceanic archipelagos: Hembry. D.H. & Balukjian, B. (2016) Molecular a perspective on the geodynamics and phylogeography of the (Tahiti; biogeography of the ’s smallest biotic provinces. Frontiers of Biogeography, 8.2, archipelago models. Journal of Biogeography, e29605. 43,South1372–1387. Pacific) reveals departures from hotspot Triantis, K.A., Kougioumoutzis, K., Legakis, A., et Holt, B.G., Lessard, J.P., Borregaard, M.K., et al. (2013) al. (2018) The zoogeographic regions of An update of Wallace’s zoogeographic regions the Aegean Sea: A multi-taxon approach. of the world. Science, 339, 74–78. In Biogeography and biodiversity of the Jønsson, K.A. & Holt, B.G. (2015) Islands contribute Aegean. In honour of Prof. Moysis Mylonas disproportionately high amounts of evolutionary diversity in passerine birds. & K. A. Triantis), pp. 279–290. Broken Hill Nature Communications, 6, 8538. Publishers(eds S. Sfenthourakis, Ltd. P. Pafilis, A. Parmakelis Kueffer, C., Drake, D. & Fernández-Palacios, J.M. (2016) Vanderpoorten, A., Rumsey, F.J. & Carine, M.A. Island biology, Oxford Bibliographies, OUP, (2007) Does Macaronesia exist? Conflicting

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 6 Whittaker et al. Archipelagos and meta-archipelagos

signal in the bryophyte and pteridophyte Whittaker, R.J., Fernández-Palacios, J.M., Matthews, floras. American Journal of Botany, 94, T.J., Borregaard, M.K. & Triantis, K.A. (2017) 625– 639. Island biogeography: taking the long view of Wallace, A.R. (1869) The Malay Archipelago. nature’s laboratories. Science, 357, eaam8326. Macmillan, London. Wallace, A.R. (1880) Island Life. Macmillan, London. Submitted: 29 October 2018 Whittaker, R.J. & Fernández-Palacios, J.M. (2007) First decision: 20 November 2018 Island biogeography: ecology, evolution, and Accepted: 30 November 2018 conservation, 2nd edn. Oxford University Press, Oxford. Edited by Michael N Dawson

Frontiers of Biogeography 2018, 10.3-4, e41470 © the authors, CC-BY 4.0 license 7