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Island Age (island + age)
Selected AbstractsGeographical 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 considerationsJOURNAL OF BIOGEOGRAPHY, Issue 9 2001Douglas 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] The Azores diversity enigma: why are there so few Azorean endemic flowering plants and why are they so widespread?JOURNAL OF BIOGEOGRAPHY, Issue 1 2010Mark A. Carine Abstract Aim, Endemism in the flora of the Azores is high (33%) but in other respects, notably the paucity of evolutionary radiations and the widespread distribution of most endemics, the flora differs markedly from the floras of the other Macaronesian archipelagos. We evaluate hypotheses to explain the distinctive patterns observed in the Azorean endemic flora, focusing particularly on comparisons with the Canary Islands. Location, Azores archipelago. Methods, Data on the distribution and ecology of Azorean endemic flowering plants are reviewed to ascertain the incidence of inter-island allopatric speciation and adaptive, ecological speciation. These are contrasted with patterns for the Canary Islands. Patterns of endemism in the Azores and Canaries are further investigated in a phylogenetic context in relation to island age. beast was used to analyse a published molecular dataset for Pericallis (Asteraceae) and to investigate the relative ages of Azorean and Canarian lineages. Results, There are few examples of inter-island allopatric speciation in the Azorean flora, despite the considerable distances between islands and sub-archipelagos. In contrast, inter-island allopatric speciation has been an important process in the evolution of the Canary Islands flora. Phylogenetic data suggest that Azorean endemic lineages are not necessarily recent in origin. Furthermore, in Pericallis the divergence of the Azorean endemic lineage from its closest relative pre-dates the radiation of a Canarian herbaceous clade by inter-island allopatric speciation. Main conclusions, The data presented do not support suggestions that hypotheses pertaining to island age, age of endemic lineages and ecological diversity considered individually explain the lack of radiations and the widespread distribution of Azorean endemics. We suggest that palaeoclimatic variation, a factor rarely considered in macroecological studies of island diversity patterns, may be an important factor. Palaeoclimatic data suggest frequent and abrupt transitions between humid and arid conditions in the Canaries during the late Quaternary, and such an unstable climate may have driven the recent diversification of the flora by inter-island allopatric speciation, a process largely absent from the climatically more stable Azores. Further phylogenetic/phylogeographic analyses are necessary to determine the relative importance of palaeoclimate and other factors in generating the patterns observed. [source] On the general dynamic model of oceanic island biogeographyJOURNAL OF BIOGEOGRAPHY, Issue 6 2009Simone Fattorini Abstract Aim, To investigate the biological meaning of equations used to apply the general dynamic model (GDM) of oceanic island biogeography proposed by R. J. Whittaker, K. A. Triantis and R. J. Ladle. Location, Analyses are presented for 17 animal groups living on the Aeolian Islands, a volcanic archipelago in the central Mediterranean, near Sicily. Methods, In addition to the mathematical implementation of the GDM proposed by Whittaker, Triantis and Ladle, and termed here logATT2 (, where S is species number or any other diversity metric, t is island age, A is island area, and a, b, c and d are fitted parameters), a new implementation based on the Arrhenius equation of the species,area relationship (SAR) is investigated. The new model (termed powerATT2) is: . For logATT2 and powerATT2 models, equations were developed to calculate (1) the expected number of species at equilibrium (i.e. when the island has reached maturity) per unit area (Seq), and (2) the time required to obtain this value (teq). Whereas the intercept in the Gleason model (S = C + z log A) or the coefficient of the Arrhenius power model (S = CAz) of the SAR can be considered measures of the expected number of species per unit area, this is not the case for the parameter a of the ATT2 models. However, values of Seq can be used for this purpose. The index of ,colonization ability' (CAB), calculated as the ratio , may provide a measure of the mean number of species added per unit area per unit time. Results, Both ATT2 models fitted most of the data well, but the powerATT2 model was in most cases superior. Equilibrial values of species richness (Seq) varied from c. 3 species km,2 (reptiles) to 100 species km,2 (mites). The fitted curves for the powerATT2 model showed large variations in d, from 0.03 to 3. However, most groups had values of d around 0.2,0.4, as commonly observed for the z -values of SARs modelled by a power function. Equilibration times ranged from about 170,000 years to 400,000 years. Mites and springtails had very high values of CAB, thus adding many more species per unit area per unit time than others. Reptiles and phytophagous scarabs showed very low values, being the groups that added fewest species per unit area per unit time. Main conclusions, Values of equilibrial species richness per unit area are influenced by species biology (e.g. body size and ecological specialization). Theoretical and empirical evidence suggests that higher immigration rates should increase the z -values of the Arrhenius model. Thus, in the same archipelago, groups with larger z -values should be characterized by higher dispersal ability. Results obtained here for the parameter d conform to this prediction. [source] Floristic biogeography of the Hawaiian Islands: influences of area, environment and paleogeographyJOURNAL OF BIOGEOGRAPHY, Issue 3 2004Jonathan P. Price Abstract Aim, A detailed database of distributions and phylogenetic relationships of native Hawaiian flowering plant species is used to weigh the relative influences of environmental and historical factors on species numbers and endemism. Location, The Hawaiian Islands are isolated in the North Pacific Ocean nearly 4000 km from the nearest continent and nearly as distant from the closest high islands, the Marquesas. The range of island sizes, environments, and geological histories within an extremely isolated archipelago make the Hawaiian Islands an ideal system in which to study spatial variation in species distributions and diversity. Because the biota is derived from colonization followed by extensive speciation, the role of evolution in shaping the regional species assemblage can be readily examined. Methods, For whole islands and regions of each major habitat, species,area relationships were assessed. Residuals of species,area relationships were subjected to correlation analysis with measures of endemism, isolation, elevation and island age. Putative groups of descendents of each colonist from outside the Hawaiian Islands were considered phylogenetic lineages whose distributions were included in analyses. Results, The species,area relationship is a prominent pattern among islands and among regions of each given habitat. Species number in each case correlates positively with number of endemics, number of lineages and number of species per lineage. For mesic and wet habitat regions, island age is more influential than area on species numbers, with older islands having more species, more single-island endemics, and higher species : lineage ratios than their areas alone would predict. Main conclusions, Because species numbers and endemism are closely tied to speciation in the Hawaiian flora, particularly in the most species-rich phylogenetic lineages, individual islands' histories are central in shaping their biota. The Maui Nui complex of islands (Maui, Moloka,i, L,na,i and Kaho,olawe), which formed a single large landmass during most of its history, is best viewed in terms of either the age or area of the complex as a whole, rather than the individual islands existing today. [source] Genetic diversity and population structure of an insular tree, Santalum austrocaledonicum in New Caledonian archipelagoMOLECULAR ECOLOGY, Issue 7 2005L. BOTTIN Abstract We present a study of the genetic diversity and structure of a tropical tree in an insular system. Santalum austrocaledonicum is endemic to the archipelago of New Caledonia and is exploited for oil extraction from heartwood. A total of 431 individuals over 17 populations were analysed for eight polymorphic microsatellite loci. The number of alleles per locus ranged from 3 to 33 and the observed heterozygosity per population ranged from 0.01 in Maré to 0.74 in Ile des Pins. The genetic diversity was lowest in the most recent islands, the Loyautés, and highest in the oldest island, Grande Terre, as well as the nearby small Ile des Pins. Significant departures from panmixia were observed for some loci,population combinations (per population FIS = 0,0.03 on Grande-Terre and Ile des Pins, and 0,0.67 on Loyautés). A strong genetic differentiation among all islands was observed (FST = 0.22), and the amount of differentiation increased with geographic distance in Iles Loyauté and in Grande Terre. At both population and island levels, island age and isolation seem to be the main factors influencing the amount of genetic diversity. In particular, populations from recent islands had large average FIS that could not be entirely explained by null alleles or a Wahlund effect. This result suggests that, at least in some populations, selfing occurred extensively. Conclusively, our results indicate a strong influence of insularity on the genetic diversity and structure of Santalum austrocaledonicum. [source] Measurements of area and the (island) species,area relationship: new directions for an old patternOIKOS, Issue 10 2008Kostas A. Triantis The species,area relationship is one of the strongest empirical generalizations in geographical ecology, yet controversy persists about some important questions concerning its causality and application. Here, using more accurate measures of island surface size for five different island systems, we show that increasing the accuracy of the estimation of area has negligible impact on the fit and form of the species,area relationship, even though our analyses included some of the most topographically diverse island groups in the world. In addition, we show that the inclusion of general measurements of environmental heterogeneity (in the form of the so-called choros model), can substantially improve the descriptive power of models of island species number. We suggest that quantification of other variables, apart from area, that are also critical for the establishment of biodiversity and at the same time have high explanatory power (such as island age, distance, productivity, energy, and environmental heterogeneity), is necessary if we are to build up a more predictive science of species richness variation across island systems. [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 considerationsJOURNAL OF BIOGEOGRAPHY, Issue 9 2001Douglas 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] | ||||||||||