Vagrants and the Paucity of Land Bird Species at the Prince Edward Islands

Aim To use patterns of nestedness in the indigenous and non-indigenous biotas of the Southern Ocean islands to determine the influence of dispersal ability on biogeographical patterns, and the importance of accounting for variation in dispersal ability in their subsequent interpretation, especially in the context of the Insulantarctic and multi-regional hypotheses proposed to explain the biogeography of these islands.Location Southern Ocean islands.Methods Nestedness was determined using a new metric, d1 (a modification of discrepancy), for the indigenous and introduced seabirds, land birds, insects and vascular plants of 26 Southern Ocean islands. To assess the possible confounding effects of spatial autocorrelation on the results, islands were assigned to 11 major island groups and each group was treated as a single island in a following analysis. In addition, nestedness of the six Southern Ocean islands comprising the South Pacific Province (New Zealand islands) was analysed. All analyses were conducted for species and genera, for each of the taxa on its own, and for the complete data sets.Results Statistically significant nestedness was found in all of the taxa examined, with nestedness declining in the order seabirds > land birds > vascular plants > insects for the indigenous species. Vagility had a marked influence on nestedness and the biogeographical patterns shown by the indigenous species. This influence was borne out by additional analyses of marine taxa and smallsized terrestrial species, both of which were more nested than the most nested group examined here, the seabirds. Assemblages of non-indigenous species also showed nestedness, and nestedness was generally more pronounced than in the indigenous species. Surprisingly, vagility had a significant effect on nestedness in these assemblages too.Main conclusions Nestedness analyses provide a quantitative means of comparing biogeographical patterns for groups differing in vagility. These comparisons revealed that vagility has a considerable influence on biogeographical patterns and should be taken into account in analyses. Here, investigations of more vagile taxa support hypotheses for a single origin of the Southern Ocean island biota (the Insulantarctica scenario), whilst those of less mobile taxa support the more commonly held, multi-regional hypothesis. All biogeographical analyses across the Southern Ocean (and elsewhere) will be influenced by the effects of dispersal ability, with composite analyses dominated by sedentary groups likely to favour multi-regional scenarios, and those dominated by mobile groups favouring single origins. Mechanisms underlying nestedness in the region range from nested physiological tolerances in more mobile groups to colonization ability and patterns of speciation in less vagile taxa. Journal of Biogeography (J. Biogeogr.) (2005) 32, 155-168 ª 2005 Blackwell Publishing Ltd www.blackwellpublishing.com/jbi 155

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“…, 1998 for discussion), and vagrants (see e.g. Burger et al. , 1980), and mammals (few species) were not included in the present analyses.…”

Section: Methodsmentioning

confidence: 99%

Nestedness of Southern Ocean island biotas: ecological perspectives on a biogeographical conundrum

Greve

Gremmen²,

Gaston

et al. 2004

Journal of Biogeography

110

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“…The line between regular vagrancy and establishment is vague, and the sub-Antarctic islands (and more southerly locations) record vagrant species on a regular basis (e.g. Burger, Williams & Sinclair, 1980;Berruti & Schramm, 1981 ;Gartshore, 1987;Gauthier-Clerc, Jiguet & Lambert, 2002). Burger et al (1980) estimated that, over the past 10 000 years, at least 80 000 birds might have reached Prince Edward Islands, attributing the failure to establish to low resource availability, severe climate, and high predation of vagrants by sub-Antarctic skuas.…”

Section: ) Vertebratesmentioning

confidence: 99%

“…Burger, Williams & Sinclair, 1980;Berruti & Schramm, 1981 ;Gartshore, 1987;Gauthier-Clerc, Jiguet & Lambert, 2002). Burger et al (1980) estimated that, over the past 10 000 years, at least 80 000 birds might have reached Prince Edward Islands, attributing the failure to establish to low resource availability, severe climate, and high predation of vagrants by sub-Antarctic skuas. Little is known about the biology and impact of alien birds on the sub-Antarctic islands.…”

Section: ) Vertebratesmentioning

confidence: 99%

Biological invasions in the Antarctic: extent, impacts and implications

Frénot

Chown

Whinam³

et al. 2005

Biol. Rev.

606

822

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Alien microbes, fungi, plants and animals occur on most of the sub-Antarctic islands and some parts of the Antarctic continent. These have arrived over approximately the last two centuries, coincident with human activity in the region. Introduction routes have varied, but are largely associated with movement of people and cargo in connection with industrial, national scientific program and tourist operations. The large majority of aliens are European in origin. They have both direct and indirect impacts on the functioning of speciespoor Antarctic ecosystems, in particular including substantial loss of local biodiversity and changes to ecosystem processes. With rapid climate change occurring in some parts of Antarctica, elevated numbers of introductions and enhanced success of colonization by aliens are likely, with consequent increases in impacts on ecosystems. Mitigation measures that will substantially reduce the risk of introductions to Antarctica and the sub-Antarctic must focus on reducing propagule loads on humans, and their food, cargo, and transport vessels.

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“…The prevailing and strongest winds recorded at Marion Island are north-westerly (i.e. in the direction from Africa [le Roux 2008]) and, according to this 'weather hypothesis', such winds could assist in blowing birds towards the islands (Burger et al 1980). Alternatively, the 'reverse migration hypothesis' (Pfeifer et al 2007) may explain the relative abundance of vagrant Palaearctic migrants observed at Marion Island, especially during the autumn (northward) migrating season (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Non-marine vagrant birds observed at the Prince Edward Islands have been reported by Burger et al (1980) for the period 1974-1979, Berruti and Schramm (1981) for 1979-1981, and Newton et al (1983) for 1981-1983. Additional new species have been reported by Cooper and Underhill (2002;blacksmith lapwing Vanellus armatus) and Kritzinger (2009;common moorhen Gallinula chloropus).…”

Section: Introductionmentioning

confidence: 87%