Search

Areas of endemism represent territories (no matter the size) of non-random overlap in the geographic distribution of two or more taxa, reflecting a common spatial history of these taxa. The common spatial history is a result of different processes that connect areas of endemism to evolutionary theory. Numerous and diverse definitions of areas of endemism have been proposed. All of them have used as the conceptual foundation of the definition a certain degree of non-random congruence of geographic distribution amongst at least two taxa. ‘Certain degree’ means that geographic congruence does not demand complete agreement on the boundaries of those taxa's distributions at all possible scales of mapping. The words ‘certain degree’ mask the polythetic nature of areas of endemism. The polythetic characterization of areas of endemism implies that each locality of the study area has a large number of a set of species. Each species of this set is present in many of those localities and, generally, none of those species is present in every locality of the area. The converse will be a monothetic nature of areas of endemism where a taxon or group of taxa is present in all the localities of the study area. We propose here that the expansion of the definition of areas of endemism, including their polythetic characterization, will improve understanding of large biogeographic areas such as realms, regions, provinces, and districts, and will increase the scientific content (e.g., predictive capability and explanatory power) of areas of endemism. [ABSTRACT FROM AUTHOR]

Plant disjunctions between the temperate regions of the northern and southern hemisphere, commonly called amphitropical or bipolar disjunctions, have been discussed by numerous authors but very little attention has been paid to the occurrence of such disjunctive ranges in the complex thalloids (Marchantiidae). A perusal of the literature revealed 20 species of Marchantiidae with amphitropical ranges, in eight genera (Asterella,Clevea,Corsinia,Cryptomitrium,Oxymitra,Riccia,RiellaandSphaerocarpos). These amphitropical species are distributed in subtropical and Mediterranean regions of the northern and southern hemisphere but not, or rarely, in the tropics. The majority are disjunctive between North America and southern South America and between Eurasia and South Africa. Long-distance dispersal of spores via birds is considered the most plausible natural cause of these amphitropical ranges. About two-third of the species have bisexual spores, which should be advantageous to long-distance dispersal. Extinction due to past climatic fluctuations may also have played a role but fossil evidence is lacking. A few species have attained their amphitropical range by human-mediated introduction:Riccia warnstorfiiLimpr. andSphaerocarpos texanusAustin were presumably introduced in the southern hemisphere whereasS. stipitatusBisch.exLindenb. from Central Chile and South Africa is adventive in the northern hemisphere. The amphitropical ranges exhibited by a number of complex thalloid species are solely based on morphological, floristic and ecological evidence and have not been tested by molecular analysis. Careful comparisons of the northern and southern populations based on an integrated molecular-phylogenetic, morphological-anatomical and chemical approach should be carried out. [ABSTRACT FROM AUTHOR]

The genusLavandulaL. consists of 39 species distributed from the North Atlantic Islands, across the Mediterranean Basin to India. We analysed 36 taxa of the genusLavandularepresenting two of the three subgenera and six of the eight sections according to the most recent classification (Upson & Andrews 2004). We achieved a phylogenetic reconstruction from partial sequences from plastid trnK and matK genes; the genome size was estimated by flow cytometer measurements. The primary aim was to track phylogenetic patterns through the maternal inherited marker at the sectional level and identify possible genome duplications. The cpDNA tree shows the phylogenetic relationships between subgenus, sections and also elucidates for the first time the relationships between the endemic species of Macaronesia, Morocco and Arabia. The ancestral split between the two subgenera could be explained by dispersal followed by an early vicariance event. TheC-value shows genome up-sizing within several phylogenetic clades and geographical areas. An ancestral genome-up sizing is characterized at the node of sectionDentataeandLavandula. The cpDNA tree suggests that the taxaL. angustifoliasubsp.pyrenaica(DC.) Guinea andL. stoechassubsp.luiseiriare best treated as a distinct species. [ABSTRACT FROM PUBLISHER]

A new species,Klasea yunus-emreiB. Dogan, Ocak & A. Duran (Asteraceae), is described from central Anatolia, Turkey. The species grows on calcareous soils in the Alpu district (Eski¸ehir province) in central Anatolia. It is morphologically similar toKlasea lasiocephala(Bornm.) Greuter & Wagenitz. Diagnostic morphological characters from closely similar taxa are discussed and arranged in a key. Ecology, conservation status and biogeography of the species are also presented. The achene surface ofK. yunus-emreiandK. lasiocephalaare examined by Scanning Electron Microscope. In addition, the geographical distribution of the new species and other related species are mapped. [ABSTRACT FROM PUBLISHER]

The intra- and inter-population and geographic differentiation ofAlnus incanawere examined biometrically on the basis of morphological character of the leaves. The study results only partly confirmed the assumption that Carpathian and Alpine populations of the species differ significantly. This may indicate that gene exchange continued during glacial periods as these regions were not sufficiently isolated from each other. The geographic variation of grey alder along the Balkans–Scandinavia axis is more eminent. It is debatable whetherA. incanahas migrated northwards from montane refugia, along Central European rivers, mostly the Vistula and Oder. It can be, however, noted that the Masurian, Sudetan and East Carpathian populations are similar to one another. [ABSTRACT FROM AUTHOR]

The woodland vegetation of Central Albania is studied and discussed along an altitudinal gradient in the Dajti National Park (DNP). The plant species combinations recorded in 168 plots were classified and subjected to indirect gradient analysis using environmental variables of geology, soil, topography, disturbance and grazing impact. The transect over more than 1300 m reflects the biogeographically intermediate paramediterranean vegetation zonation and the relatively humid Mediterranean “hygric series” at its eastern margins. It reveals the total range of woodland types known to occur in Central Albania, thus stressing the representativity of the area regarding biodiversity and biogeography, and its importance for nature conservation. Along the elevation gradient, we found three plant communities of the mesomediterranean Quercetalia ilicis, five of the supramediterranean Quercetalia pubescentis and five of the montane or oromediterranean Fagetalia sylvaticae. [ABSTRACT FROM PUBLISHER]

The aim of this article was to test the way in which geographical factors influence island floras in the Mediterranean basin, using ferns as target organisms, and the islands surrounding Sicily as location. A matrix with presence/absence data concerning fern taxa in the 16 islands studied was compiled. Cluster analysis, principal co-ordinates analysis (PCoA), principal components analysis (PCA) and a Bayesian analysis were performed. For each island, the total number of fern taxa was regressed against three factors: island area, island elevation and isolation. All the analyses pointed to affinities between islands according to their different geological composition, independently from their geographic position. A clear positive island species/area relationship (ISAR) was shown only for the volcanic islands. The island species/(area×elevation) relationship (ISAER), on the contrary, was unsatisfactory. The main features of interest are the following: (1) the clear division of the islands into two groups, volcanic vs. sedimentary; (2) the floristic richness of the volcanic compared to sedimentary islands and (3) the uniqueness of the pteridophyte flora of Pantelleria. This seems to demonstrate that the lower number of taxa in the islands farthest away from the “mainland” (Sicily, Tunisia) is not due to isolation, but due to another factor, probably habitat availability. [ABSTRACT FROM PUBLISHER]

The three subgenera of alder (Alnusroman Clethropsis and Alnobetula) are taxonomically distinctive, but how does their pollen match up with their gross morphology? This study links pollen characters with the taxonomic divisions of the genus alder based on nrDNA ITS sequence data. The value of the study is in the breadth of the taxonomic coverage of the three subgenera, as the samples per species only range from 1 to 6. From 29 Alnus species, the authors studied pollen from 59 modern reference collections (prepared by acetolysis) and recorded the number and type of apertures (pores), thickness of the arci, pollen size and polar arci. Tallies of the number of pores on the pollen grains in a reference collection typically have a range of ± 1 or 2. Exceptions are presumed hybrid collections in Alnus rugosa with a range of ± 5, which have malformed pollen cells suggesting infertility. The presumed hybrids show a greater range of both pore number and size of pollen grains. The dominant pore number is a key feature that separates the subgenus Alnobetula (= Alnaster) from the other two subgenera by consistently having predominantly 5-, 6- or 7-pored pollen grains, while all other Alnus taxa sampled have pollen with predominantly 4- or 5-pored pollen. The dominant pore number is a consistent feature within the subgenus Alnobetula (10 species), but is inconsistent in 3 out of 16 species of the subgenus Alnus and within the subgenus Clethropsis (3 species). Thickenings of the pore lip, aspidate (protruding) and vestibulate pores are important features of Alnus pollen on a species level. Alnus-like pollen morphology occurs occasionally in certain other betulaceous genera (Betula and Carpinus). Differences in character or thickness of arci (band-like thickenings on the pollen wall between pores) tend to be somewhat consistent within a species and vary within subgenera. Two Alnobetula species in the Alnus viridis complex (Alnus crispa and Alnus sinuata) have arci that are weakly developed or appear as simple folds; walls are fragile and pores are typically less aspidate. Pollen sizes in different species overlap greatly, may be partly influenced by processing methods and do not seem to be generally helpful in characterizing species. Circular doughnut-shaped arci thickenings on the polar area of pollen grains are a common feature (16–40%) in two closely related East Asian taxa of subgenus Alnobetula with large pollen (‘Clade A’: Alnus firma and Alnus sieboldii). These ‘Clade A’ features have been reported from Miocene collections of Alnus pollen from Alaska, and support megafossil evidence in determining the biogeography of this group along the Pacific Rim in the Neogene. The Miocene appearance of subgenus Alnobetula megafossils in both Alaska and Japan can only have occurred via a Bering Land Bridge. This relation is now confirmed by Reinink-Smith's Miocene ‘Clade-A-type’ pollen data of Alaska. These taxa had Pacific Rim distributions, similar fruiting carposamaras and now correspond to a DNA ITS subgroup within Alnobetula. Depending on the geographic location with limited number of local alder species, certain Holocene identifications are possible based on pore structure and arci thickness, e.g. the Alnus crispa-type in eastern Canada and the Alnus sinuata-type in the Pacific northwest. [ABSTRACT FROM PUBLISHER]

Biogeography, the study of animal and plant distribution, has a history extending back to at least the eighteenth century. But it was not until the work of Charles Darwin and Alfred Russel Wallace in the mid-nineteenth century that it really came into its own as a science. Darwin's importance notwithstanding, it was really Wallace who put the field on the map, and many of today's research threads can be traced back to his influence. This article provides a summary review of Wallace's life and work and biogeography as a field of study, including Wallace's role in its development. [ABSTRACT FROM PUBLISHER]

Nivicolous myxomycetes constitute an ecologically well defined group of organisms occurring at the edge of melting winter snow cover. They often are considered and described as alpine species, occurring exclusively or most frequently in the alpine belt. We reviewed and synthesized available published data on the altitudinal occurrences of nivicolous myxomycetes in 22 massifs worldwide and attributed the records to main altitudinal belts (montane/subalpine/alpine) defined for particular areas. Based on this comparative analysis we attempted to analyze and discuss general views on the altitudinal/biogeographical properties of nivicolous myxomycetes. Our, study indicates that the altitudinal distribution of nivicolous mycomycetes extends over montane, subalpine and alpine belts. The most abundant records were found in the forest (montane) belt, while the alpine belt had the lowest number of occurrences. Although this picture might be biased to some extent by better average exploration of lower areas, it shows clearly that this ecological group--even though connected with mountainous habitats--does not form an alpine element. Therefore they should not be considered alpine species. Based on the available data it also could be hypothesized that nivicolous myxomycetes form a widely distributed biogeographical mountain element instead of an alpine or arctic-alpine element. Based on our conclusions we also emphasize the need for precise and cautious use of the notion of "alpines", which appears to be confusingly overused in the myxomycete studies. [ABSTRACT FROM AUTHOR]

Asexual organisms usually have larger, and in the Northern Hemisphere, more northern distributions than their sexual relatives. This phenomenon, called geographical parthenogenesis, has been attributed to predispositions in certain taxa, advantages of polyploidy and/or hybrid origin, advantages of uniparental reproduction, introgression of apomixis into sexuals, niche differentiation of clones, and biotic interactions. Here we focus on the role of uniparental reproduction in colonisation, and the importance of different developmental pathways, i.e. autonomous apomixis which does not require pollination and fertilisation of endosperm nuclei for successful seed set, and pseudogamous apomixis which does. A literature survey suggests that geographical parthenogenesis occurs frequently in species with autonomous apomixis, while the correlation with pseudogamy is poorly documented. However, taxonomic patterns (e.g. predominance of Asteraceae) and also methodological bias may influence estimates of frequencies of geographical parthenogenesis. We demonstrate that a flow cytometric seed screen (FCSS) is a powerful method for assessing pseudogamous vs. autonomous apomixis. We show that population genetic studies provide insights into the genetic diversity of apomicts, but do not give strong support for uniparental reproduction being the only explanation of geographical parthenogenesis. Molecular studies help elucidate the evolutionary and biogeographical history of apomictic complexes, and we conclude that multidisciplinary studies are needed to understand fully the phenomenon of geographical parthenogenesis. [ABSTRACT FROM AUTHOR]

Four species of Favolaschia are accepted for New Zealand: F. calocera, F. pustulosa, and two new species F. cyatheae and F. austrocyatheae. Favolaschia cyatheae, F. austrocyatheae, and F. pustulosa are native to New Zealand. Favolaschia calocera, first described from Madagascar, has also been previously reported from New Zealand, Norfolk Island, and Italy. We report a wider geographical distribution for this species. Levels of genetic variation between collections suggest that F. calocera is paleotropical, native to Madagascar, southern China, and Thailand, with recent (probably human-induced) introductions to Norfolk Island, Kenya, Italy, New Zealand, and Réunion Island. ITS sequences show that the tiny monocotyledon-inhabiting F. minima is not a Favolaschia; it is here transferred to Panellus. Taxonomic descriptions, illustrations, distribution maps within New Zealand, and a key to the Favolaschia species known from New Zealand are provided, together with a discussion on past miscitations of the genus Favolaschia and its species. [ABSTRACT FROM AUTHOR]

We examined the distribution of trees and shrubs on 14 mid-channel islands in the Swan River, northwest Montana. We observed the general trend that plants were distributed in a linear sequence of send stages. Pioneer successional phase plants dominated the downstream ends of islands, mid-successional vegetation dominated the middle of the islands, and late successional vegetation and the oldest trees were largely restricted to the upstream portions of the largest islands. The observed pattern was most distinct on islands farthest upstream in the river channel (i.e., smallest catchment area) and least distinct on islands farthest downstream in the catchment basin. We conclude the consistent pattern of semi organization and the influence of catchment size would be unlikely if the development of mid-channel river islands were controlled by site-specific factors influencing individual islands independently. We suggest that all islands are responding similarly to the shared influence of fluvial dynamics (i.e., timing, duration, and magnitude of rise and fall of river discharge), but smaller scale variability in plant distribution among individual islands suggests site-specific variables and/or random events modify the action of fluvial dynamics. [ABSTRACT FROM AUTHOR]

Biogeography is a natural science that deals with the study of the earth's plant and animal distribution patterns in geographical space, both in terms of the present day and also in the context of their evolution and development over time. it has deep historical roots in the identification of the spatial relationships of organisms, while its fundamental principles embody those of the theory of evolution and the ecosystem concept. More recently, the work of, among others, Robert MacArthur and Edward Wilson, has proved instrumental in developing thinking as to how organisms achieve and maintain their ranges. Over longer, geological, time scales, the key principles of biogeography include the influence of changing global geography, especially through continental drift, on biological distributions. In the context of the present day and more recent past, climate and climatic change are regarded as the most significant factors determining the distributions of organisms. Biogeography is applicable to a wide range of practical environmental problems in South Africa. In particular, the discipline has made important advances in understanding issues such as the establishment and management of conservation areas, the prediction of the impact of global climate change on organisms, and on the management of plant and animal communities, including humans, as integral components of ecosystems. [ABSTRACT FROM AUTHOR]