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Species Radiation (species + radiation)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Radiation of the Spider Genus Dysdera (Araneae, Dysderidae) in the Canary Islands: Cladistic Assessment Based on Multiple Data Sets

CLADISTICS, Issue 4 2001
Miquel A. Arnedo
The volcanic archipelago of the Canary Islands, 100 km off the northwestern coast of Africa, harbors 43 endemic species of the mostly circum-Mediterranean spider genus Dysdera (Araneae, Dysderidae). This amounts to approximately one-fourth of all known Dysdera species in an area that represents 0.1% of the range of the genus. In order to address the origin of this extraordinary number of endemic species, the phylogenetic relationships among all the endemic taxa and a sample of 27 continental species were reconstructed. A simultaneous cladistic analysis was performed on 66 morphological characters, 471 bp of the cytochrome oxidase I and 424 bp of the 16S rRNA mitochondrial genes. The preferred most parsimonious tree supports a single origin for most of the endemic species (84%), although this tree is ambiguous regarding the total number of overseas colonizations (allowing a minimum of two and a maximum of four colonization events). Our data suggest that the Canary Islands have been the source of the colonizers of some of the remaining Macaronesian archipelagoes (certainly for the Selvagem Islands and the Cape Verdes and possibly for Madeira); the Azores have been independently colonized by dysderids from the continent. The present study provides a phylogenetic framework for an exceptional case of insular species radiation, an essential tool for unraveling the factors that have promoted this amazing diversification. Species radiations in oceanic archipelagoes are excellent models for the study of speciation processes. [source]

The effect of environmental diversification on species diversification in New Caledonian caddisflies (Insecta: Trichoptera: Hydropsychidae)

JOURNAL OF BIOGEOGRAPHY, Issue 5 2010
Marianne Espeland
Abstract 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. [source]

Geographical history of the central-western Pacific black fly subgenus Inseliellum (Diptera: Simuliidae: Simulium) based on a reconstructed phylogeny of the species, hot-spot archipelagoes and hydrological considerations

JOURNAL OF BIOGEOGRAPHY, Issue 9 2001
Douglas A. Craig
Aim With six new species of subgenus Inseliellum Rubtsov recently described, a revised reconstructed phylogeny based on morphology is required. Geological history of islands where Inseliellum occurs, plus a cladistic analysis and hydrological considerations, provide the basis for a reconstructed geographical history of the species. Location Inseliellum is widely distributed and occurs in Micronesia, Cook Islands and Polynesia. A single specimen is known from Tonga Islands. Methods Maximum parsimony criteria using PAUP*, plus cytological information, were used to arrive at a preferred phylogenic reconstruction. Island ages of the hot spot archipelagoes involved are well known. The phylogeny was then compared with the palaeogeology. Information on evolution of running water habitats as islands age was incorporated into the biogeography. Results Cladistic analysis of forty of the forty-eight known Inseliellum species with Simulium (Nevermannia) neornatipes Dumbleton from New Caledonia and S. (Hebridosimulium) laciniatum Edwards from Fiji as outgroups, shows basal species and clades to be on widely separated older islands. In the Society Islands basal species are widely spread. Derived species, with morphological adaptations to deal with specialized habitats, are on younger islands (e.g. Tahiti), where a major species radiation has taken place. The reconstructed phylogeny indicates dispersal back to older islands, with minor subsequent species radiation. Main conclusions Palaeogeological evidence provides a basis for postulating that Inseliellum entered the western Pacific area some 20 Ma, with the possibility that it rafted eastwards on proto-Tonga Islands to the edge of southern-central Pacific. Older Cook Islands were present at that time. Movement into the Marquesas Islands was not earlier than 6 Ma and into the Society Islands perhaps 8,10 Ma. Basal species with generalized habitat requirements would have found suitable habitats (inferred from hydrological postulates) on leaves in the original, small shaded streams. With erosion and valley development, in particular on Tahiti, species radiated into specialized habitats such as cascades. Rich seston and high velocity probably drove reduction of filtering fans in some clades. With collapse of the caldera and formation of large rivers at c. 0.9 Ma, S. exasperans Craig and S. tahitiense Edwards adapted to deep, swiftly flowing water, all indicative that specialized habitat availability drove species radiation in Inseliellum. In the Society Islands, dispersal of derived species back to the oldest western islands was not possible because erosion has removed suitable habitats. [source]

Immigration, species radiation and extinction in a highly diverse songbird lineage: white-eyes on Indian Ocean islands

MOLECULAR ECOLOGY, Issue 12 2006
BEN H. WARREN
Abstract Molecular phylogenetic hypotheses of species-rich lineages in regions where geological history can be reliably inferred may provide insights into the scale of processes driving diversification. Here we sample all extant or recently extinct white-eye (Zosterops) taxa of the southwest Indian Ocean, combined with samples from all principal continental lineages. Results support a high dispersal capability, with at least two independent continental sources for white-eyes of the region. An early (within 1.8 million years ago) expansion into the Indian Ocean may have originated either from Asia or Africa; the three resulting lineages show a disparate distribution consistent with considerable extinction following their arrival. Africa is supported as the origin of a later expansion into the region (within 1.2 million years ago). On two islands, a pair of Zosterops species derived from independent immigrations into the Indian Ocean co-occur or may have formerly co-occurred, providing strong support for their origin by double-island colonization rather than within-island (sympatric or microallopatric) speciation. On Mauritius and La Réunion, phylogenetic placement of sympatric white-eyes allow us to rule out a scenario in which independent within-island speciation occurred on both islands; one of the species pairs must have arisen by double colonization, while the other pair is likely to have arisen by the same mechanism. Long-distance immigration therefore appears to be responsible for much of the region's white-eye diversity. Independent immigrations into the region have resulted in lineages with mutually exclusive distributions and it seems likely that competition with congeneric species, rather than arrival frequency, may limit present-day diversity. [source]