bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular biogeography of the Mediterranean lizards Podarcis Wagler, 1830 and Teira Gray, 1838 (Reptilia, Lacertidae)
Authors: Oliverio Marco , Bologna Marco A. , Mariottini Paolo 
Published: March 2003

AbstractAim  We discuss biogeographical hypotheses for the Mediterranean lizard species Podarcis and Teira within a phylogenetic framework based on partial mitochondrial DNA sequences.Methods  We derived the most likely phylogenetic hypothesis from our data set (597 aligned positions from the 12S rDNA and phenyl tRNA) under parsimony, distance and maximum likelihood assumptions.Results  The species usually included in Teira do not form a strongly monophyletic clade. In contrast, the monophyly of the genus Podarcis is rather well supported. Seven lineages are identified in the genus; in order of appearance within the tree, these are: the Balearic pityusensis and lilfordi pair, the sicula complex, a Tyrrhenian tiliguerta and raffonei pair, muralis, the Siculo‐Maltese filfolensis and wagleriana pair, the Balkan group (erhardi, peloponnesiaca, milensis, melisellensis and taurica), and the Ibero‐Maghrebian group (bocagei, atrata, hispanica and vaucheri).Conclusions  The origin of the three European genera of lacertid assayed (Lacerta, Teira and Podarcis) is hypothesized to have occurred in the Oligocene. For Podarcis, a possible scenario of a Miocene diversification is derived from the sequence data, and the zoogeography of the lineages are discussed in relation to the palaeogeography of the Mediterranean. It is hypothesized that in the early history of the genus the main lineages separated by rapid, numerous and close events that produced a starting point very similar to a polytomy, hard to resolve by parsimony analysis of the data set.
Patterns in the distribution, composition and diversity of diatom assemblages in relation to ecoclimatic factors in Arctic Lapland
Authors: Weckström J. , Korhola A. 
Published: March 2003

AimRelationships between diatom distribution, composition, species richness and environmental variables in lakes in Arctic Lapland were explored with particular attention to temperature.LocationTransect in northern Fennoscandia (66°92–69°27) spanning boreal coniferous forest to treeless tundra along an altitudinal gradient of 108–1024 m a.s.l.MethodsSurface‐sediment diatom assemblages and 22 physical and chemical limnological variables from 64 lakes were determined. Ordination techniques (PCA, DCA, CCA) and associated Monte Carlo permutation tests were used to identify the main environmental parameters controlling the distribution of the diatom taxa. Temperature optima and tolerances were estimated by weighted averaging (WA) regression. Diversity indices and cluster analysis were used to discover patterns in biodiversity and composition of diatom assemblages along the vegetational and altitudinal gradients.ResultsA total of 370 diatom taxa representing 40 genera were recorded, most of which were periphytic species. Lake‐water pH, calcium, sediment organic content, mean July temperature, and total organic carbon (TOC) were identified as the most important environmental variables in explaining the diatom distributions. Lakes located in the middle of the temperature gradient (i.e. mountain birch woodland in the ‘forest–tundra’ transition zone) was found to have the highest species diversity. The temperatures at around 13 °C (≈ 300 m a.s.l) and at around 9.5 °C (≈ 750 m a.s.l.) were identified as the major biotic boundaries.Main conclusionsOur results indicate that distribution, composition and species diversity of diatoms are markedly regulated by temperature and other climate‐related factors in ecotonal waters. Ecological boundary areas are highlighted as important areas for maintaining biodiversity. The overall results lend support to the concept of ‘aquatic ecotone’.
Floristic analysis of vascular plant genera of North America north of Mexico: spatial patterning of phytogeography
Authors: Qian Hong 
Published: March 2003

AimThis paper aims at determining and quantifying phytogeographical relationships between North America and the rest of the world at the regional level and identifying possible patterns of regional differentiation in phytogeographical relationships, particularly along latitudinal and longitudinal gradients.LocationNorth America north of Mexico.MethodsNorth America north of Mexico was divided into twelve geographical regions arrayed in a grid with three divisions east‐to‐west by four divisions north‐to‐south. Based on the similarity of their world‐wide geographical distribution patterns, a total of 1904 indigenous genera of vascular plants found in North America north of Mexico were grouped into ten phytogeographical elements. Phytogeographical relationships of the twelve geographical regions of North America north of Mexico to the world flora were examined, based on the composition of phytogeographical elements. Multivariate analyses were used to determine the phytogeographical relationships.ResultsAlong a latitudinal gradient from the Arctic to tropical North America, the proportions of the cosmopolitan and holarctic genera markedly increased, whereas the pantropical, amphi‐Atlantic tropical, neotropical and North American endemic genera strikingly decreased. Along a longitudinal gradient from the Atlantic coast to the Pacific coast, the proportions of the pantropical, amphi‐Pacific tropical, neotropical and North American–eastern Asian genera tended to decrease, whereas the North American–South American and North American endemic genera tended to increase.Main conclusionsThe spatial patterns of the phytogeography of North America could be to a large degree interpreted by the different effects of the direct land connections between North America and Eurasia and South America on intercontinental migration and by the different effects of regional geographical settings within North America on the speciation, dispersal and extinction of plant species.
Establishment patterns of exotic birds are constrained by non‐random patterns in introduction
Authors: Blackburn Tim M. , Duncan Richard P. 
Published: March 2003

AimSpecies transported to and introduced into non‐native environments, termed ‘introductions’, constitute a growing component of many regional floras and faunas, yet not all such species successfully establish. Investigations into why some introductions succeed while others fail are often based on analyses of the outcome of historical introductions. Such ‘experiments in nature’ have the drawback that the effects of interest may be confounded because they have not been randomized with respect to each other, and because the species and locations chosen for introduction may not be a random subset of the available species or locations. Our aim is to quantify this non‐randomness using a global data set of bird introductions, and examine the factors associated with introduction probability in two subsets of these data, one taxonomic (order Anseriformes) and one geographical (British birds).LocationGlobal.MethodsStatistical analyses of the distributions among taxa and locations for 1378 introduction events for 426 bird species across the world, and statistical analyses of the characteristics of Anseriform and British bird species selected for introduction.ResultsGlobal introductions of birds have been highly non‐random with respect to taxon, location of origin, and location of introduction. Most introductions involve species in just five families (Phasianidae, Passeridae, Psittacidae, Anatidae and Columbidae), and most introductions have been to temperate and island locations. Within the taxonomic and geographical subsets, the species chosen for introduction tend to be abundant species that would have been relatively easy to obtain.Main conclusionsThe characteristics of the species and locations chosen for introduction are not representative of species and locations in general, which limits our ability to draw general conclusions from historical records, and generates problems of confounding and non‐independence in statistical analyses of introduction success. We suggest possible solutions for these problems.
A comparison of a discovery‐based and an event‐based method of historical biogeography
Authors: Brooks Daniel R. , McLennan Deborah A. 
Published: March 2003

AimThe event‐based method Dispersal‐Vicariance Analysis (DIVA) is compared with the discovery‐based method Brooks Parsimony analysis (BPA).LocationSouth‐western USA, Mexico and northern Central America.MethodsResults of DIVA of phylogenetic trees for six clades of birds inhabiting seven areas in the south‐western US, Mexico and northern Central America are compared with those of BPA for the same data set.ResultsBoth approaches identify the same vicariant elements but differ in the way they treat dispersal. DIVA places such elements in one general ‘dispersal’ category, while BPA identifies different forms of dispersal, including peripheral isolates speciation (speciation by dispersal), post‐speciation dispersal, non‐response to a vicariance event, secondary contact between congeners (and the potential for reinforcement completing speciation) and potential extinction resulting from competition between a resident and a colonizing congener.Main conclusionsBPA is more sensitive than DIVA with respect to the different possible manifestations of geographical dispersal. Despite substantial dispersal, avian communities in these areas manifest substantial historical structuring.
Distribution, abundance and biomass of epiphyte‐lianoid communities in a New Zealand lowland Nothofagus‐podocarp temperate rain forest: tropical comparisons
Authors: Hofstede Robert G. M. , Dickinson Katharine J. M. , Mark Alan F. 
Published: March 2003

AimIn tropical rain forests, epiphytes can contribute significantly to species diversity and biomass, a feature not generally associated with temperate forest systems. This study investigates epiphyte‐liane diversity and biomass on three host trees (two Dacrycarpus dacrydioides [Podocarpaceae] and one Nothofagus menziesii [Fagaceae]).LocationThese trees were of varying architecture on different sites in a New Zealand lowland temperate rain forest at 45°43′ S.MethodsCover of epiphytic and lianoid species (vascular and non‐vascular) was recorded in 5 m vertical height segments (trunk), on four aspects (north, south, east and west); and in four sections (inner, middle, outer branches and branch extremes) on four branch faces (positions: topside, both sides, underside) on each tree. Inclination, branch face, and diameter of branch/trunk substrate, height above ground, duff thickness, and location on tree (trunkfoot, main trunk, inner branches, middle branches, outer branches, branch extremes) were all recorded in 359 samples. Epiphytic biomass was derived for one tree.ResultsSixty‐one vascular and ninety‐four non‐vascular taxa were recorded. Eight communities associated with the highly vegetated inner branches and main trunk, and seven indicative of the less vegetated middle to outer branches and branch extremes were recognized. Thirteen of the fifteen communities were present on a forest interior D. dacrydioides tree, nine on a riverside D. dacrydioides tree and seven on a N. menziesii tree. Most of the seven measured environmental variables were statistically significant in relation to ordination analyses of the samples. Dry mass per unit area and dry bulk density recorded were 350 ± 125 and 118 ± 13 g dm–2, respectively (trunkbase), and 206 ± 21 and 91 ± 4 g dm–2, respectively (inner and middle branches combined).Main conclusionsEpiphytic community analyses that do not include non‐vascular flora either as generalized categories or as individual taxa are incomplete. Values for epiphytic dry weight for the trunkfoot of one tree appear to exceed comparable figures recorded from tropical rain forest systems. Epiphytic communities and biomass within at least some temperate rain forests can be validly compared with those of tropical rain forests.
Geographic distribution and population size of the mountain tapir (Tapirus pinchaque) in Colombia
Authors: Lizcano D. J. , Pizarro V. , Cavelier J. , Carmona J. 
Published: March 2003

AimWe conducted a study to estimate the past and present distribution and population size of T. pinchaque in Colombia.LocationThe study included all mountain ranges above 2000 m.MethodsThe past distribution was obtained by plotting on a map of past distribution of montane rain forests, the geographical locations with the name `danta' or `tapir' above 2000 m obtained from topographic maps, the locations cited in bibliographic references, and the results of interviews in the 530 Andean municipalities. The present distribution was obtained by plotting the present distribution of montane rain forests, the results of interviews and ground control. Population size was estimated by combining measurements of population density with maps of present distribution.ResultsIn the past, the species occurred in the central and eastern Cordilleras, as well as in the Andean Massive where the three cordilleras merge in the south of the country. Currently, the species occurs in the central Andes south of Nevados National Park, and in the eastern Andes, south of Paramo de Sumapaz, Bogotá. According to our most optimistic estimates, there are about 2500 tapirs in the Andes of Colombia.Main conclusionsThese individuals occur in a total of thirty‐five forest patches that range from 5 to 3700 km2. Only five to six fragments have the minimum necessary size (826 km2) to maintain at least 150 individuals, the estimated number to maintain viable population in the short term. The populations most threatened are those of the central Cordillera between P.N. Las Hermosas and P.N. Nevado del Huila where large tracts of mature montane forests are being converted to opium fields.
Geographical distribution of allozyme variation in relation to post‐glacial history in Carex digitata, a widespread European woodland sedge
Authors: Tyler Torbjörn 
Published: March 2003

AimTo investigate the distribution, and broad‐scale geographical patterns, of variation, in the widespread boreo‐nemoral woodland herb Carex digitata throughout its native European range. To interpret the revealed geographical pattern of variation in terms of glacial survival, post‐glacial migration and inter‐regional gene‐flow.LocationThe whole of Europe divided into twenty‐five geographical regions.MethodsGenetic variation at nine polymorphic allozyme loci was analysed in 10–25 individuals from 66 populations from throughout the European range of C. digitata. Allele frequencies were calculated both at the level of populations and at the level of geographical regions, and these frequencies were used to calculate the Cavalli‐Sforza chord distance (CSCD). CSCD between neighbouring regions were presented on geographical maps. CSCD at both the population and the regional level were subjected to UPGMA cluster analysis. Standard measures of genetic diversity were calculated and divided into within population, region and species components.ResultsMost alleles had a scattered distribution throughout, but several alleles were mainly found in Fennoscandia and regional allelic richness was the highest here. Cluster analysis on the level of populations did not recover any geographical structure. However, genetic distances between regions, each consisting of 1–4 populations, revealed a clear geographical pattern. Genetic distances were low between (1) Scandinavian and British regions and (2) between Mediterranean regions, moderate between Central European regions and high between far‐east European and Caucasian regions.Main conclusionsA post‐glacial scenario involving independent glacial survivals in south‐eastern European Russia, the Caucasian Mountains, the Mediterranean area and central Europe is proposed. Northern Europe (i.e. Fennoscandia) appears to have been colonized through many independent long‐distance dispersals from different extra‐Fennoscandian populations. High regional population densities in Fennoscandia are assumed to have facilitated accumulation of genetic variation and inter‐regional gene‐flow as compared with more southern populations which are generally of restricted size and appear to have been mutually isolated and subjected to strong genetic drift.
Korapuki Island as a case study for restoration of insular ecosystems in New Zealand
Authors: Towns David R. 
Published: March 2003

AimSuccess with eradicating invasive species from islands around New Zealand raises the prospect of reversing the loss of species by restoring biotic communities on modified islands. I seek to identify methods that can be used to clarify restoration targets on Korapuki Island, which was modified by introduced mammals until 1987.LocationKorapuki, Green and Middle islands, Mercury Islands, north‐eastern New Zealand.MethodsI describe methods of identifying restoration targets by using biogeographical frameworks, and benchmark systems based on neighbouring unmodified islands. Methods that can help identify directions and rates of change are also investigated.ResultsThe benchmark islands (Middle and Green) have complex forest systems with a distinctive component of large, flightless invertebrates, dense populations of tuatara Sphenodon punctatus (Gray), dense and diverse populations of lizards and dense populations of burrowing seabirds. The restoration island (Korapuki) has simplified forest systems, few large invertebrates, no S. punctatus, a depauperate fauna of lizards and scattered populations of seabirds. These differences are consistent with the recorded effects of rabbits Oryctolagus cuniculus (L.) and Pacific rats Rattus exulans (Peale) removed from Korapuki Island in 1986–87. Three restoration scenarios are described and restoration targets identified. Time scales for natural succession are likely to be influenced by a long‐lived colonizing tree species that now predominate over much of the island. The rate of expansion of reintroduced animals is influenced by the very low productivity of many of the species apparently extirpated by introduced mammals.Main conclusionsEcological restoration of island ecosystems has been likened to reconstituting the ambiguous because of conceptual and practical difficulties. Goals for restoration of island systems are often dependent on value judgements. Biological outcomes or targets can be clarified by the use of unmodified neighbouring islands as benchmarks. However, successional pathways on the restored island may not converge with the benchmarks because of environmental differences between sites.
Breakage of mutualisms by exotic species: the case of Cneorum tricoccon L. in the Balearic Islands (Western Mediterranean Sea)
Authors: Riera Núria , Traveset Anna , García Oscar 
Published: March 2003

AimIn this study we tested the hypothesis that the dispersal success (estimated here as fruit removal rate) of a native shrub species living in the Balearic Archipelago, Cneorum tricoccon L. (Cneoraceae), has decreased significantly in those islands where endemic lizards of the genus Podarcis have disappeared. These lizards acted as the main seed dispersers of the plant and became extinct after the introduction of carnivores. At least one of these carnivores, the pine marten (Martes martes L.), is also an important frugivore, consuming the fruits and dispersing the seeds of C. tricoccon and thus allowing the comparison of fruit removal rates between the two groups of vertebrates (lizards and mammals). We further tested the possibility that lizards (in particular, P. pityusensis Boscà) could be exerting selection on seed size.MethodsIn seven populations from four islands, we monitored fruit removal by either lizards or mammals. The fruits of C. tricoccon do not drop after ripening, remaining attached to the branches for long periods if not removed. In order to test whether lizards might be exerting selection on seed size, we compared seed diameter and weight between defecated and uningested (collected directly from plants) seeds for each of the populations.ResultsFruits were removed in significantly greater proportions in those populations where lizards are still present. Data showed that in two of the examined populations in the Pityusic islands, defecated seeds were lighter and smaller than controls suggesting that lizards selected fruits of smaller size than the average of the population.Main conclusionsThe introduction of carnivores in the Balearics has led to important changes in the population dynamics of many native species. In the larger islands (Mallorca and Menorca), carnivores seemed to have caused the extinction of endemic lizards who acted as the only dispersers of some plants such as C. tricoccon. Pine martens, in particular, are in turn frugivorous and thus can `replace' to some extent the `lost' seed dispersers. We hypothesize that besides having decreased fruit removal rates in this shrub, these `new' dispersers have modified considerably the distribution of the plant on Mallorca island, as the fossil record shows that lizards lived at low altitudes (<500 m a.s.l.) and the plant can be currently found up to 1000 m a.s.l. Furthermore, preliminary data suggest that lizards might be exerting a selective pressure on seed size. If this is true, this pressure might have been released – or counteracted if carnivores select for fruit size as well – after the extinction of lizards from some islands, which would have important ecological consequences for the plant.
Variation at high latitudes: the geography of body size and cranial morphology of the muskox, Ovibos moschatus
Authors: Smith Paul A. , Schaefer James A. , Patterson Brent. R. 
Published: March 2003

Abstract Aim Bergmann's rule, one of the most studied and controversial ecogeographical generalizations, has rarely been tested with observations from high latitudes. We tested the rule using cranial measurements of the muskox [Ovibos moschatus (Zimmerman)], a homeotherm with an extremely northern distribution. We also used these data to describe geographical patterns in the species' dental architecture, an extension of the framework developed from interspecific comparisons.Location Specimens were compiled from arctic Canada, Alaska and Greenland, a latitudinal range of 60° N−83° N.Methods Body size was estimated from principal components analysis (PCA) of five cranial characters from 128 specimens. Mean scores on the first principal component from each locality were regressed against latitude and mean temperature to identify geographical variation in body size; scores on the second principal component were regressed against latitude to assess patterns in dental architecture. Regression analyses of the individual characters were performed as a complement to PCA.Results No latitudinal or climatic trend in body size was observed in either sex. On the other hand, for males, significant latitudinal variation was found for the second PCA axis (r = −0.434), and the feature which loaded most heavily on it, maxillary tooth row length (r = 0.429). For females, this dental structure also tended to increase with latitude (r = 0.423), but the trend was only marginally significant (P=0.12), perhaps owing to a smaller sample size.Main conclusions The geographically invariant body size of muskoxen failed to support current hypotheses of size variation. Behavioural and physiological adaptations may exempt the muskox from selective pressures underlying these hypotheses. We interpret latitudinal variation in dental architecture as a reflection of a cline in diet, dominated by graminoids at the expense of willows at higher latitudes. This intraspecific geographical trend is a recapitulation of the interspecific framework for large mammalian herbivores.