Taxonomic homogenization and differentiation across Southern Ocean Islands differ among insects and vascular plants

Shaw, Justine D., Spear, Dian, Greve, Michelle and Chown, Steven L. (2010) Taxonomic homogenization and differentiation across Southern Ocean Islands differ among insects and vascular plants. Journal of Biogeography, 37 2: 217-228. doi:10.1111/j.1365-2699.2009.02204.x

Author Shaw, Justine D.
Spear, Dian
Greve, Michelle
Chown, Steven L.
Title Taxonomic homogenization and differentiation across Southern Ocean Islands differ among insects and vascular plants
Journal name Journal of Biogeography   Check publisher's open access policy
ISSN 1365-2699
Publication date 2010-02-01
Sub-type Article (original research)
DOI 10.1111/j.1365-2699.2009.02204.x
Open Access Status Not yet assessed
Volume 37
Issue 2
Start page 217
End page 228
Total pages 12
Place of publication Oxford, United Kingdom
Publisher Wiley-Blackwell
Language eng
Formatted abstract
Aim  To investigate taxonomic homogenization and/or differentiation of insect and vascular plant assemblages across the Southern Ocean Islands (SOI), and how they differ with changing spatial extent and taxonomic resolution.

Location  Twenty-two islands located across the Southern Ocean, further subdivided into five island biogeographical provinces. These islands are used because comprehensive data on both indigenous and non-indigenous insect and plant species are available.

Methods  An existing database was updated, using newly published species records, identifying the indigenous and non-indigenous insect and vascular plant species recorded for each island. Homogenization and differentiation were measured using Jaccard’s index (JI) of similarity for assemblages across all islands on a pairwise basis, and for island pairs within each of the biogeographical provinces. The effects of taxonomic resolution (species, genus, family) and distance on levels of homogenization or differentiation were examined. To explore further the patterns of similarity among islands for each of the taxa and groupings (indigenous and non-indigenous), islands were clustered based on JI similarity matrices and using group averaging.

Results  Across the SOI, insect assemblages have become homogenized (0.7% increase in similarity at species level) while plant assemblages have become differentiated at genus and species levels. Homogenization was recorded only when pairwise distances among islands exceeded 3000 km for insect assemblages, but distances had to exceed 10,000 km for plant assemblages. Widely distributed non-indigenous plant species tend to have wider distributions across the SOI than do their insect counterparts, and this is also true of the indigenous species.

Main conclusions  Insect assemblages across the SOI have become homogenized as a consequence of the establishment of non-indigenous species, while plant assemblages have become more differentiated. The likely reason is that indigenous plant assemblages are more similar across the SOI than are insect assemblages, which show greater regionalization. Thus, although a suite of widespread, typically European, weedy, non-indigenous plant species has established on many islands, the outcome has largely been differentiation. Because further introductions of insects and vascular plants are probable as climates warm across the region, the patterns documented here are likely to change through time.
Keyword Biological invasions
Non-indigenous species
Southern Ocean Islands
Spatial scale
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 40 times in Thomson Reuters Web of Science Article | Citations
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Created: Mon, 19 May 2014, 21:00:42 EST by Justine Shaw on behalf of School of Biological Sciences