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Diversification on an ancient Darwinian island: Evolutionary history of caddisflies (Trichoptera) and other organisms on New Caledonia
Stockholm University, Faculty of Science, Department of Zoology.
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.
Keyword [en]
New Caledonia, Trichoptera, island, biogeography, phylogenetics, DNA, dispersal, vicariance, adaptation, ultramafic, diversification, new species, environmental factors
Research subject
Systematic Zoology
Identifiers
URN: urn:nbn:se:su:diva-41154ISBN: 978-91-7447-114-4 (print)OAI: oai:DiVA.org:su-41154DiVA: diva2:328588
Public defence
2010-10-15, Lilla Hörsalen, Naturhistoriska Riksmuseet, Frescativägen 40, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
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
List of papers
1. Species diversifications in New Caledonia: towards the end of the museum model?
Open this publication in new window or tab >>Species diversifications in New Caledonia: towards the end of the museum model?
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:su:diva-41054 (URN)
Available from: 2010-07-01 Created: 2010-07-01 Last updated: 2010-07-06
2. New species and descriptions of females of the New Caledonian endemic genus Xanthochorema (Trichoptera, Hydrobiosidae)
Open this publication in new window or tab >>New species and descriptions of females of the New Caledonian endemic genus Xanthochorema (Trichoptera, Hydrobiosidae)
2008 (English)In: Zoologia Neocaledonica 6. Biodiversity studies in New Caledonia, Paris: Muséum national d’Histoire naturelle , 2008, 79-97 p.Chapter in book (Other academic)
Place, publisher, year, edition, pages
Paris: Muséum national d’Histoire naturelle, 2008
Series
Mémoires du Muséum national d’Histoire naturelle, 197
Identifiers
urn:nbn:se:su:diva-31077 (URN)978-2-85653-605-6 (ISBN)
Available from: 2009-11-03 Created: 2009-11-03 Last updated: 2010-07-06Bibliographically approved
3. Early Xanthochorema (Trichoptera, Insecta) radiations in New Caledonia originated on ultrabasic rocks.
Open this publication in new window or tab >>Early Xanthochorema (Trichoptera, Insecta) radiations in New Caledonia originated on ultrabasic rocks.
2008 (English)In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 48, no 3, 904-17 p.Article in journal (Refereed) Published
Abstract [en]

The toxic and nutrient poor ultrabasic rock substrate covering one-third of New Caledonia greatly influenced on the biogeography and diversity of plants in the island. Studies on the effect of ultrabasic substrate on fauna are almost entirely absent. In this paper we examine whether the diversification of Trichoptera of the New Caledonian endemic genus Xanthochorema Kimmins, 1953 was related to the presence of ultrabasic substrate. The analysis is based on data from a phylogeny derived from DNA sequences of mitochondrial COX1, COX2 and 16S, and nuclear EF1a genes. The study of the relationships between ancestral species and substrate was carried out using dispersal-vicariance analysis and tracing the history of substrate association with ultrabasic and non-ultrabasic distributions representing the terminals in the fully resolved phylogenetic tree. Our results show that (1) the ancestor of all Xanthochorema species was present on ultrabasic substrate, (2) early speciation events were restricted to ultrabasic substrate, (3) younger ancestral species dispersed into non-ultrabasic substrates, and (4) late speciation events were restricted to non-ultrabasic substrate. These results correspond to the hypothesis that New Caledonia once was more extensively covered by ultrabasic rocks than at present.

Keyword
Trichoptera; Dispersal–vicariance analysis; Tracing distributions; New Caledonia; Ultrabasic rocks; Species radiation; Phylogeny
National Category
Biological Systematics
Identifiers
urn:nbn:se:su:diva-14622 (URN)10.1016/j.ympev.2008.06.006 (DOI)000259421300009 ()18620067 (PubMedID)
Available from: 2008-10-15 Created: 2008-10-15 Last updated: 2010-07-06Bibliographically approved
4. The effect of environmental diversification on species diversification in New Caledonian caddisflies (Insecta: Trichoptera: Hydropsychidae)
Open this publication in new window or tab >>The effect of environmental diversification on species diversification in New Caledonian caddisflies (Insecta: Trichoptera: Hydropsychidae)
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.

Keyword
Character optimization • environmental heterogeneity • evolutionary radiation • freshwater insects • Hydropsychidae • lineage-through-time plot • New Caledonia • phylogeny • species diversification
National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-38742 (URN)10.1111/j.1365-2699.2009.02263.x (DOI)000276861700008 ()
Available from: 2010-04-27 Created: 2010-04-27 Last updated: 2011-11-23Bibliographically approved
5. The diversity and radiation of the largest monophyletic animal group on New Caledonia (Trichoptera: Ecnomidae: Agmina)
Open this publication in new window or tab >>The diversity and radiation of the largest monophyletic animal group on New Caledonia (Trichoptera: Ecnomidae: Agmina)
2010 (English)In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 23, no 10, 2112-2122 p.Article in journal (Refereed) Published
Abstract [en]

In area, New Caledonia is the smallest of the world's 25 official biodiversity hotspots, but in many taxonomic groups, the island has the highest concentration of species on earth, particularly so in the freshwater insect order Trichoptera. This study aims at applying molecular data and morphology for estimating the real species diversity of the genus Agmina on New Caledonia and investigating potential effects of ultramafic rock substrate on diversification. A dated molecular phylogeny was applied to study diversity and diversification related to geological substrate using the dispersal-extinction-cladogenesis model, diva and Bayesian ancestral character reconstruction. More than 47 species (> 63%) were unknown to science. Initial radiation occurred on ultramafic substrate followed by several independent dispersal events to nonultramafic substrate. The rate of shift from ultramafic to nonultramafic substrate was significantly higher than the rate of shift in the opposite direction, indicating a possible cost associated with living on ultramafic substrate.

Keyword
Agmina, biogeography, diversification, Ecnomidae, evolution, freshwater, species diversity, south-west Pacific, Trichoptera, ultramafic substrate
National Category
Zoology
Identifiers
urn:nbn:se:su:diva-41152 (URN)10.1111/j.1420-9101.2010.02072.x (DOI)000281827000008 ()
Available from: 2010-07-05 Created: 2010-07-05 Last updated: 2011-12-01Bibliographically approved

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