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The effect of environmental diversification on species diversification in New Caledonian caddisflies (Insecta: Trichoptera: Hydropsychidae)
Stockholm University, Faculty of Science, Department of Zoology, Systematic Zoology.
Swedish Museum of Natural History, Entomology department.
2010 (English)In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 37, no 5, 879-890 p.Article in journal (Refereed) Published
Abstract [en]

Aim To test whether environmental diversification played a role in the diversification of the New Caledonian Hydropsychinae caddisflies.

Location New Caledonia, south-west Pacific.

Methods The phylogeny of the New Caledonian Hydropsychinae caddisflies was hypothesized using parsimony and Bayesian methods on molecular characters. The Bayesian analysis was the basis for a comparative analysis of the correlation between phylogeny and three environmental factors: geological substrate (ultrabasic, non-ultrabasic), elevation and precipitation. Phylogenetic divergence times were estimated using a relaxed clock method, and environmental factors were mapped onto a lineage-through-time plot to investigate the timing of environmental diversification in relation to species radiation. The correlation between rainfall and elevation was tested using independent contrasts, and the gamma statistic was calculated to infer the diversification pattern of the group.

Results The diversification of extant Orthopsyche–Caledopsyche species began in the Middle–Late Oligocene, when much of the island of New Caledonia was covered by ultrabasic substrate and mountain forming was prevalent. Most lineages originated in the Middle–Late Miocene, a period associated with long-term climate oscillation. Optimization of environmental factors on the phylogeny demonstrated that the New Caledonian Hydropsychinae group adapted to ultrabasic substrate early in its evolutionary history. The clade living mostly on ultrabasic substrate was far more species-rich than the clade living mostly on non-ultrabasic substrate. Elevation and rainfall were significantly correlated with each other. The lineage-through-time plot revealed that the main environmental diversification preceded species diversification. A constant speciation through time was rejected, and the negative gamma indicates that most of the diversification occurred early in the history of the clade. According to the inferred phylogeny, the genus Orthopsyche McFarlane is a synonym under Caledopsyche Kimmins, and Abacaria caledona Oláh & Barnard should also be included in Caledopsyche.

Main conclusions The age of the radiation does not support a vicariance origin of New Caledonian Hydropsychinae caddisflies. Environmental diversification pre-dates lineage diversification, and thus environmental heterogeneity potentially played a role in the diversification of the group, by providing a variety of fragmented habitats to disperse into, promoting speciation. The negative gamma indicates that the speciation rate slowed as niches started to fill.

Place, publisher, year, edition, pages
2010. Vol. 37, no 5, 879-890 p.
Keyword [en]
Character optimization • environmental heterogeneity • evolutionary radiation • freshwater insects • Hydropsychidae • lineage-through-time plot • New Caledonia • phylogeny • species diversification
National Category
Natural Sciences
URN: urn:nbn:se:su:diva-38742DOI: 10.1111/j.1365-2699.2009.02263.xISI: 000276861700008OAI: diva2:314116
Available from: 2010-04-27 Created: 2010-04-27 Last updated: 2011-11-23Bibliographically approved
In thesis
1. Diversification on an ancient Darwinian island: Evolutionary history of caddisflies (Trichoptera) and other organisms on New Caledonia
Open this publication in new window or tab >>Diversification on an ancient Darwinian island: Evolutionary history of caddisflies (Trichoptera) and other organisms on New Caledonia
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Islands are either of continental or oceanic origin, and the biota of such islands are a result of vicariance and dispersal, respectively. New Caledonia, in the South Pacific, is a part of former Gondwana, but the origin of its biota is heavily debated. Geological studies show that the island was submerged in the Eocene, and that oceanic crust was obducted onto New Caledonia leaving a thick layer of ultramafic rocks on top of the island. We tested the null hypothesis that New Caledonian biota are a result of old Gondwanan vicariance by fitting diversification models on phylogenies from the literature and calculating the gamma statistic. According to the null hypothesis diversification is gradual over time. If on the other hand the biota are a result of recent dispersal or have survived in refugia we would expect slowing of diversification over time. Based on our results we can reject the null hypothesis of old vicariance for the New Caledonian biota. The caddisfly (Trichoptera) fauna on New Caledonia is exceptionally rich with around 600 species, and more than 99.9% are endemic. Molecular phylogenetic hypotheses for three monophyletic caddisfly radiations, Xanthochorema, Caledopsyche et al. and Agmina, are presented. Age estimates agrees with the geological evidence. Three new species of Xanthochorema are described and more than 63% of the Agmina species are new to science. The ultramafic rock substrate, with high heavy metal concentration, has led to high levels of plant adaptation on New Caledonia. We show that caddisflies adapted early to this substrate and subsequently dispersed to non-ultramafic substrate several times, with significantly fewer dispersal events back to the toxic substrate, indicating that adaptation to ultramafic substrate is required and recolonization is difficult when this adaptation has been lost. Ultramafic substrate and other environmental factors have been important in driving the diversification of New Caledonian caddisflies.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2010. 35 p.
New Caledonia, Trichoptera, island, biogeography, phylogenetics, DNA, dispersal, vicariance, adaptation, ultramafic, diversification, new species, environmental factors
Research subject
Systematic Zoology
urn:nbn:se:su:diva-41154 (URN)978-91-7447-114-4 (ISBN)
Public defence
2010-10-15, Lilla Hörsalen, Naturhistoriska Riksmuseet, Frescativägen 40, Stockholm, 13:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 5: AcceptedAvailable from: 2010-09-23 Created: 2010-07-05 Last updated: 2010-07-08Bibliographically approved

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